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INTERNET-DRAFT                                              R. W. Shirey
Obsoletes: RFC 2828 (if approved) 2828, FYI 36                             BBN Technologies
Expiration Date: 20 February 2004                         20 August 2004 9 September 2005                           9 March 2005


                 Internet Security Glossary, Version 2
                   <draft-shirey-secgloss-v2-00.txt>
                   <draft-shirey-secgloss-v2-01.txt>

Status of this Memo

   By submitting this Internet-Draft, I certify that any applicable
   patent or other IPR claims of which I am aware have been disclosed,
   or will be disclosed, and any of which I become aware will be
   disclosed, in accordance with RFC 3668.

   This document may not be modified, and derivative works of it may
   not be created, except to publish it as an RFC and to translate it
   into languages other than English.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
   groups may also distribute working documents as Internet-
   Drafts. Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than a "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html"

Copyright Notice

   Copyright (C) The Internet Society (2004). (2005). All Rights Reserved.

Abstract

   This Glossary has 1,500 entries that give provides definitions, abbreviations, and explanations for
   of terminology concerning for information system security. It makes The 288 pages of
   listings offer recommendations to improve the clarity of Internet
   Standards documents (ISDs) and the ease with which to make them more easily understood by
   international
   readers can understand ISDs. Its readers. The recommendations follow the principles that
   ISDs should (a) use the same term or definition whenever the same
   concept is mentioned; (b) use terms in their plainest, dictionary
   sense; (c) use terms that are already well-established in open
   publications; and (d) avoid terms that are proprietary, favor a
   particular vendor, or create a bias toward a particular technology or
   mechanism versus other, competing techniques that already exist or
   might be developed.





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Table of Contents

   Section                                                          Page
   -------                                                          ----
   1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . .   3
   2. Format of Entries  . . . . . . . . . . . . . . . . . . . . . .   4
      2.1 Presentation Order . . . . . . . . . . . . . . . . . . . .   4
      2.2 Capitalization and Abbreviation  . . . . . . . . . . . . .   4
      2.3 Support for Automated Searching  . . . . . . . . . . . . .   5
      2.4 Definition Type and Context  . . . . . . . . . . . . . . .   5
      2.5 Explanatory Notes  . . . . . . . . . . . . . . . . . . . .   5
      2.6 Cross-References . . . . . . . . . . . . . . . . . . . . .   5
      2.7 Trademarks . . . . . . . . . . . . . . . . . . . . . . . .   6
      2.8 The New Punctuation  . . . . . . . . . . . . . . . . . . .   6
   3. Types of Definitions Entries . . . . . . . . . . . . . . . . . . . . . . .   6
      3.1 Type "I": Recommended Definition with Definitions of Internet Basis Origin . . .   6
      3.2 Type "N": Recommended Definition with Definitions of Non-Internet Basis Origin .   7
      3.3 Type "O": Other Definitions. . . . . . . . . . . . Terms and Definitions to be Noted  . . . .   7
      2.4
      3.4 Type "D": Deprecated Terms and Definitions . . . . . . . . . . . . .   7
      2.5
      3.5 Definition Substitutions . . . . . . . . . . . . . . . . .   7
   4. Definitions  . . . . . . . . . . . . . . . . . . . . . . . . .   9
   5. Informative References . . . . . . . . . . . . . . . . . . .   276 . 297
   6. Security Considerations  . . . . . . . . . . . . . . . . . . . 293 315
   7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 293 315
   8. Author's Address . . . . . . . . . . . . . . . . . . . . . . . 293 315
   9. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 293 315




























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1. Introduction

   This Glossary provides an internally consistent and self-contained
   set of terms, abbreviations, and definitions -- supported by
   explanations, recommendations, and references -- for terminology that
   concerns information system security. The intent of this Glossary is
   to improve the comprehensibility of Internet Standards documents
   (ISDs) -- i.e., RFCs, Internet-Drafts, and other material produced as
   part of the Internet Standards Process [R2026] (RFC 2026) -- and of all other
   Internet-related material, too. discourse. A few non-security, networking terms are
   included to make the Glossary self-contained, but more complete
   glossaries of networking terms are available elsewhere [A1523, F1037,
   R1208, R1983].

   This Glossary supports the goals of the Internet Standards Process:

   o Clear, Concise, Easily Understood Documentation

      This Glossary seeks to improve comprehensibility of security-
      related content of ISDs. That requires wording to be clear and
      understandable, and requires the set of security-related terms and
      definitions to be consistent and self-supporting. Also,
      terminology needs to be uniform across all ISDs; i.e., the same
      term or definition needs to be used whenever and wherever the same
      concept is mentioned. Harmonization of existing ISDs need not be
      done immediately, but it is desirable to correct and standardize
      terminology when new versions are issued in the normal course of
      standards development and evolution.

   o Technical Excellence

      Just as Internet Standard (STD) protocols should operate
      effectively, ISDs should use terminology accurately, precisely,
      and unambiguously to enable standards to be implemented correctly.

   o Prior Implementation and Testing

      Just as STD protocols require demonstrated experience and
      stability before adoption, ISDs need to use well-established
      language. Using terms in their plainest, dictionary sense (when
      appropriate) helps to ensure international understanding. ISDs
      need to avoid using private, made-up terms in place of generally- generally
      accepted terms from open publications. ISDs need to avoid
      substituting new definitions that conflict with established ones.
      ISDs need to avoid using "cute" synonyms (e.g., see: Green Book),
      because no matter how popular a nickname may be in one community,
      it is likely to cause confusion in another.

   o Openness, Fairness, and Timeliness

      ISDs need to avoid terms that are proprietary or otherwise favor a
      particular vendor, or that create a bias toward a particular


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      security technology or mechanism over other, competing techniques
      that already exist or might be developed in the future. The set of
      terminology used across the set of ISDs needs to be flexible and
      adaptable as the state of Internet security art evolves.

   In support of those goals, this Glossary provides guidance by marking
   terms and definitions as being either endorsed or deprecated for use
   in ISDs. The key words "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
   and "OPTIONAL" are intended to be interpreted the same way as in an
   Internet Standard (i.e., as specified in RFC 2119). Other glossaries
   (e.g., [Raym]) list additional terms that deal with Internet security
   but have not been included in this Glossary because they are not
   appropriate for ISDs.

   This Glossary is not an Internet standard, and its guidance
   represents only the recommendations of this author. However, this
   Glossary provides reasons for its recommendations -- particularly for
   the SHOULD NOTs -- so that readers can judge for themselves whether
   to follow the guidance.

2. Format of Entries

   Section 4 presents Glossary entries in the following manner:

   2.1 Order of Entries

      Entries are sorted in lexicographic order, without regard to
      capitalization. Numeric digits are treated as preceding alphabetic
      characters; special characters are treated as preceding digits;
      blanks are treated as preceding all other characters; and a hyphen
      or slash between two parts of an entry is treated like a blank.

      If an entry has multiple definitions (e.g., "domain"), they are
      numbered beginning with "1", and any of those multiple definitions
      that are RECOMMENDED for use in ISDs are presented before other
      definitions for that entry. If definitions are closely related
      (e.g., "threat"), they are denoted by adding letters to a number,
      such as "1a" and "1b".

   2.2 Capitalization and Abbreviations

      Entries that are proper nouns are capitalized (e.g., "Data
      Encryption Algorithm"), as are other words derived from proper
      nouns (e.g., "Caesar cipher"). All other entries are not
      capitalized (e.g., "certification authority"). Each acronym or
      other abbreviation that appears in this Glossary, either as an
      entry or in a definition or explanation, is defined in this
      Glossary, except items of common English usage, such as "e.g.",
      "etc.", "i.e.", "vol.", "pp.", and "U.S.".





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   2.3 Support for Automated Searching

      Each entry is preceded by a dollar sign ($) and a space. This
      makes it possible to find the defining entry for an item "X" by
      searching for the character string "$ X", without stopping at
      entries in which "X" is used in explanations.

   2.4 Definition Type and Context

      Each entry is preceded by a character -- I, N, O, or D -- enclosed
      in parentheses, to indicate the type of definition (as is
      explained further in Section 3):
      -  "I" for a RECOMMENDED term or definition of Internet origin.
      -  "N" if RECOMMENDED but not of Internet origin.
      -  "O" for a term or definition that is NOT recommended for use in
         ISDs but is something that authors of Internet documents need
         to should
         know about.
      -  "D" for a term or definition that is deprecated and SHOULD NOT
         be used in Internet documents.

      If a definition is valid only in a specific context (e.g.,
      "baggage"), that context is shown immediately following the
      definition type and is enclosed by a pair of slash symbols (/). If
      the definition is valid only for specific parts of speech, that is
      shown in the same way (e.g., "archive).

   2.5 Explanatory Notes

      Some entries have explanatory text that is introduced by one or
      more of the following keywords:
      -  Deprecated Abbreviation (e.g., "EE", "H field", "W3")
      -  Deprecated Definition (e.g., "digital certification")
      -  Deprecated Usage (e.g., "authenticate")
      -  Deprecated Term (e.g., "certificate authority")
      -  Pronunciation (e.g., "*-property")
      -  Derivation (e.g., "discretionary access control")
      -  Tutorial (e.g., "accreditation")
      -  Example (e.g., "back door")
      -  Usage (e.g., "access")

      Explanatory text in this Glossary MAY be reused in other ISDs.
      However, such text is not intended to authoritatively supersede
      text of an ISD in which the Glossary entry is already used.

   2.6 Cross-References

      Some entries contain a parenthetical remark of the form "(See:
      X)",
      X.)", where X is a list one of more related Glossary entries. Some
      entries contain a remark of the form "(Compare: X)", where X is a
      list of other entries that either are antonyms or differ in some
      other manner worth observing. noting.



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   2.7 Trademarks

      All servicemarks and trademarks that appear in this Glossary are
      used in an editorial fashion and to the benefit of the mark owner,
      without any intention of infringement.

   2.8 The New Punctuation

      This Glossary uses the "new" or "logical" punctuation style that
      is
      favored by computer programmers, as described in by Raymond [Raym]:
      Programmers use pairs of quotation marks the same way they use
      pairs of parentheses, i.e., as balanced delimiters. For example,
      if " Alice "Alice sends" is a phrase, and so are "Bill receives" and "Eve
      listens", then a programmer would write the following sentence:

         "Alice sends", "Bill receives", and "Eve listens".

      According to standard American usage, the punctuation in that
      sentence is incorrect; the continuation commas and the final
      period should go inside the string quotes, like this:

         "Alice sends," "Bill receives," and "Eve listens."

      However, a programmer would not include a character in a literal
      string if the character did not belong there, because that could
      cause an error. For example, suppose a sentence in a draft of a
      tutorial on the vi editing language looked like this:

         Then delete one line from the file by typing "dd".

      A book editor following standard usage might change the sentence
      to look like this:

         Then delete one line from the file by typing "dd."

      However, in the vi language, the dot character repeats the last
      command accepted. So, if a reader entered "dd.", two lines would
      be deleted instead of one.

      Similarly, use of standard American punctuation might cause
      misunderstanding in entries in this Glossary. Thus, the new
      punctuation is used here, and we recommend it for ISDs.

3. Types of Definition Entries

   Each entry in this Glossary is marked as type I, N, O, or D:

   3.1 Type "I": Recommended Term or Definition with Definitions of Internet Basis Origin

      The marking "I" indicates two things:
      -  Origin: "I" (as opposed to "N") means either that the Internet
         Standards Process or Internet community is authoritative for


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         the definition *or* that the term is sufficiently generic that
         this Glossary can freely state a definition without
         contradicting a non-Internet authority (e.g., "attack").
      -  Recommendation: "I" (as opposed to "O") means that the term and
         definition are RECOMMENDED for use in ISDs. However, some "I"
         entries may be accompanied by a "Usage" note that states a
         limitation (e.g., "certification"), and ISDs SHOULD NOT use the
         defined term outside that limited context.

      Many "I" entries are proper nouns (e.g., "Internet Protocol") for
      which the definition is intended only to provide basic
      information; i.e., the authoritative definition of such terms is
      found elsewhere. For a proper noun described as an "Internet
      protocol", please refer to the current edition of "Internet
      Official Protocol Standards" (STD (Standard 1) for the standardization
      status of the protocol.

   3.2 Type "N": Recommended Term or Definition with Definitions of Non-Internet Basis Origin

      The marking "N" indicates two things:
      -  Origin: "N" (as opposed to "I") means that the entry has a non-
         Internet basis or origin.
      -  Recommendation: "N" (as opposed to "O") means that the term and
         definition are RECOMMENDED for use in ISDs, if they are needed
         at all in ISDs. Many of these entries are accompanied by a
         label that states a context (e.g., "package") or a note that
         states a limitation (e.g., "data integrity"), and ISDs SHOULD
         NOT use the defined term outside that context or limit. Some of
         the contexts are rarely if ever expected to occur in an ISD
         (e.g., see: baggage). In those cases, the listing exists to
         make Internet authors aware of the non-Internet usage so that
         they can avoid conflicts with non-Internet documents.

   3.3 Type "O": Other Terms and Definitions To Be Noted

      The marking "O" means that the definition has a is of non-Internet basis
      origin and SHOULD NOT be used in ISDs *except* in cases where the
      term is specifically identified as non-Internet.

      For example, an ISD might mention "BCA" (see: brand certification
      authority) or "baggage" as an example of some concept; in that
      case, the document should specifically say "SET(trademark) BCA" or
      "SET(trademark) baggage" and include the definition of the term.

   3.4 Type "D": Deprecated Terms and Definitions

      If this Glossary recommends that an a term or definition SHOULD NOT
      be used in ISDs, then the entry is marked as type "D", and a
      "Deprecated Term", "Deprecated Definition", or "Deprecated Usage"
      explanatory note is provided.




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   3.5 Definition Substitutions

      Some terms have a definition published by a non-Internet authority
      -- government (e.g., "object reuse"), industry (e.g., "Secure Data
      Exchange"), national authority (e.g., "Data Encryption Standard"),
      or international body (e.g., "data confidentiality") -- that is
      suitable for use in ISDs. In those cases, this Glossary marks the
      definition "N", recommending its use in Internet documents.

      Other such terms have definitions that are inadequate or
      inappropriate for ISDs. For example, a definition might be
      outdated or too narrow, or it might need clarification by
      substituting more careful wording (e.g., "authentication
      exchange") or explanations, using other terms that are defined in
      this Glossary. In those cases, this Glossary marks the entry "O",
      and provides an "I" or "N" entry that precedes, and is intended to
      supersede, the "O" entry.

      In some cases where this Glossary provides a definition to
      supersede an "O" definition, the substitute is intended to subsume
      the meaning of the "O" entry and not conflict with it. For the
      term "security service", for example, the "O" definition deals
      narrowly with only communication services provided by layers in
      the OSI model OSIRM and is inadequate for the full range of ISD usage, while
      the new "I" definition provided by this Glossary can be used in
      more situations and for more kinds of service. However, the "O"
      definition is also listed so that ISD authors will be aware of the
      context in which the term is used more narrowly.

      When making substitutions, this Glossary attempts to avoid
      contradicting any non-Internet authority. Still, terminology
      differs between the standards of authorities such as the American Bar Association,
      OSI, SET, the U.S. DoD, and other authorities; and this Glossary
      probably is not exactly aligned with any of them.




















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4. Definitions

   $ *-property
      (N) Synonym for "confinement property" in the context of the Bell-
      LaPadula model. Pronunciation: star property.

   $ 3DES
      (N) See: Triple Data Encryption Algorithm.

   $ A1 computer system
      (O) /TCSEC/ See: TCSEC. Tutorial under "Trusted Computer System
      Evaluation Criteria".

   $ AA
      See: attribute authority.

   $ ABA Guidelines
      (N) "American Bar Association (ABA) Digital Signature Guidelines"
      [ABA], a framework of legal principles for using digital
      signatures and digital certificates in electronic commerce.

   $ Abstract Syntax Notation One (ASN.1)
      (N) A standard for describing data objects. [Larm, X680] (See:
      CMS.)

      Deprecated Usage: This The term is often incorrectly "ASN.1" can be used narrowly to refer
      describe the notation or language called "Abstract
      Syntax Notation One", or can be used more broadly to BER.
      encompass the notation, its associated encoding rules
      (see: BER), and software tools that assist in its use.

      Tutorial: OSIRM defines computer network functionality in layers.
      Protocols and data objects at higher layers are abstractly defined
      to be implemented using protocols and data objects from lower
      layers. A higher layer may define transfers of abstract objects
      between computers, and a lower layer may define those transfers
      concretely as strings of bits. Syntax is needed to specify data
      formats of abstract objects, and encoding rules are needed to
      transform abstract objects into bit strings at lower layers. OSI
      standards use ASN.1 for those specifications and use various
      encoding rules for those transformations. (See: BER.)

      In ASN.1, formal names are written without spaces, and separate
      words in a name are indicated by capitalizing the first letter of
      each word except the first word. For example, the name of a CRL is
      "certificateRevocationList".

   $ ACC
      (I) See: access control center.

   $ acceptable risk
      (I) A risk that is understood and tolerated by a system's user,


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      operator, owner, or accreditor, usually because the cost or
      difficulty of implementing an effective countermeasure for the
      associated vulnerability exceeds the expectation of loss. (See:
      adequate security, (second
      law under) Courtney's laws.)



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   $ access
      1. (I) The ability and means to communicate with or otherwise
      interact with a system to use system resources either to handle
      information or to gain knowledge of the information the system
      contains. (Compare: handle.)

      Usage: The definition is intended to include all types of
      communication with a system, including one-way communication in
      either direction. In actual practice, however, entities that are
      outside a security perimeter and can receive output from the
      system but cannot provide input or otherwise directly interact
      with the system, passive users might
      be treated as not having "access" (and, and, therefore, be exempt from security policy requirements, such as
      most requirements of the need for a system's security clearance). policy. (See: "passive
      user" under "user".)

      2. (O) /formal model/ "A specific type of interaction between a
      subject and an object that results in the flow of information from
      one to the other." [NCS04]

   $ Access Certificate for Electronic Services (ACES)
      (O) A PKI operated by the U.S. Government's General Services
      Administration in cooperation with industry partners. (See: CAM.)

   $ access control
      1. (I) Protection of system resources against unauthorized access.

      2. (I) A process by which use of system resources is regulated
      according to a security policy and is permitted only by authorized
      entities (users, programs, processes, or other systems) according
      to that policy. (See: access, access control service, computer
      security, discretionary access control, mandatory access control,
      role-based access control.)

      3. (I) /formal model/ Limitations on interactions between subjects
      and objects in an information system.

      4. (O) "The prevention of unauthorized use of a resource,
      including the prevention of use of a resource in an unauthorized
      manner." [I7498 Part 2]

      5. (O) /U.S. Government/ A system using physical, electronic, or
      human controls to identify or admit personnel with properly
      authorized access to a SCIF.

   $ access control center (ACC)
      (I) A computer that maintains a database (possibly in the form of
      an access control matrix) defining the security policy for an
      access control service, and that acts as a server for clients
      requesting access control decisions.


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      Tutorial: An ACC is sometimes used in conjunction with a key
      center to implement access control in a key distribution key-distribution system


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      for symmetric cryptography. (See: BLACKER, Kerberos.)

   $ access control list (ACL)
      (I) /information system/ A mechanism that implements access
      control for a system resource by enumerating the system entities
      that are permitted to access the resource and, and stating, either
      implicitly or explicitly, the types of access modes granted to each. each entity.
      (Compare: access control matrix, access list, access profile, capability.)
      capability list.)

   $ access control matrix
      (I) A rectangular array of cells, with one row per subject and one
      column per object. The entry in a cell -- that is, the entry for a
      particular subject-object pair -- indicates the access mode that
      the subject is permitted to exercise on the object. Each column is
      equivalent to an "access control list" for the object; and each
      row is equivalent to an "access profile" for the subject.

   $ access control service
      (I) A security service that protects against a system entity using
      a system resource in a way not authorized by the system's security
      policy. (See: access control, discretionary access control,
      identity-based security policy, mandatory access control, rule-
      based security policy.)

      Tutorial: This service includes protecting against use of a
      resource in an unauthorized manner by an entity (i.e., a
      principal) that is authorized to use the resource in some other
      manner. (See: insider.) The two basic mechanisms for implementing
      this service are ACLs and tickets.

   $ access level
      (D) Synonym for the hierarchical "classification level" in a
      security level. [C4009] (See: security level.)

      Deprecated Term: ISDs SHOULD NOT use this term; it mixes concepts
      in a potentially misleading way. Access control may be based on
      attributes other than classification level.

   $ access list
      (I) /physical security/ Roster of persons who are authorized to
      enter a controlled area. (Compare: access control list.)

   $ access mode
      (I) A distinct type of data processing operation -- e.g., read,
      write, append, or execute execute, or a combination of operations -- that
      a subject can potentially perform on an object in an information
      system. [Huff]



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   $ access policy
      (I) A kind of "security policy". (See: access, access control.)

   $ access profile
      (O) /information system/ A mechanism that implements access


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      control synonym for a system entity by enumerating the system resources
      that the entity is authorized to access and, either implicitly or
      explicitly, the types of access granted to each. (Compare: access
      control matrix, access control list, access list, capability.) "capability list".

      Usage: The definition is not widely known; therefore, ISDs that use this term SHOULD state a definition for it. it
      because the definition is not widely known.

   $ access right
      (I) Synonym for "authorization"; emphasizes the possession of the
      authorization by a system entity.

   $ accountability
      (I) The property of a system or system resource that ensures that
      the actions of a system entity may be traced uniquely to that
      entity, which can then be held responsible for its actions. [Huff]
      (See: audit service.)

      Tutorial: Accountability (also known as (a.k.a. "individual accountability")
      typically involves requires a system capability ability to positively associate the
      identity of a user with the time, method, and mode of the user's
      access to the system. This capability ability supports detection and
      subsequent investigation of security breaches. Individual persons
      who are system users are held accountable for their actions after
      being notified of the rules of behavior for using the system and
      the penalties associated with violating those rules.

   $ accounting
      See: COMSEC accounting.

   $ accounting legend code (ALC)
      (O) /U.S. Government/ Numeric system used to indicate the minimum
      accounting controls required for items of COMSEC material within
      the CMCS. [C4009] (See: COMSEC accounting.)

   $ accreditation
      (N) An administrative action by which a designated authority
      declares that an information system is approved to operate in a
      particular security configuration with a prescribed set of
      safeguards. [FP102, SP37] (See: certification.)

      Tutorial: An accreditation is usually based on a technical
      certification of the system's security mechanisms. To accredit a
      system, the approving authority must determine that any residual
      risk is an acceptable risk. Although the terms "certification" and
      "accreditation" are used more in the U.S. DoD and other government
      agencies than in commercial organizations, the concepts apply any
      place where managers are required to deal with and accept
      responsibility for security risks. For example, the American Bar
      Association is developing accreditation criteria for CAs.



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   $ accreditation boundary
      (O) Synonym for "security perimeter". [C4009]

   $ accreditor
      (N) A management official who has been designated to have the
      formal authority to "accredit" an information system, i.e., to
      authorize the operation of, and the processing of sensitive data
      in, the system and to accept the residual risk associated with the
      system. (See: accreditation, residual risk.)

   $ ACES
      (O) See: Access Certificate for Electronic Services.

   $ ACL
      (I) See: access control list.

   $ acquirer
      1. (O) /SET/ "The financial institution that establishes an
      account with a merchant and processes payment card authorizations
      and payments." [SET1]

      2. (O) /SET/ "The institution (or its agent) that acquires from
      the card acceptor the financial data relating to the transaction
      and initiates that data into an interchange system." [SET2]

   $ activation data
      (N) Secret data, other than keys, that is required to access a
      cryptographic module.

   $ active attack
      (I) See: (secondary secondary definition under) attack. under "attack".

   $ active content
      (O) "Electronic documents that can carry out or trigger actions
      automatically on a computer platform without the intervention of a
      user. [This technology enables] mobile code associated with a
      document to execute as the document is rendered." [SP28] (See:
      mobile code.)

   $ active user
      (I) See: secondary definition under "attack".

   $ active wiretapping
      (I) A wiretapping attack that attempts to alter data being
      communicated or otherwise affect data flow. (See: wiretapping.
      Compare: active attack, passive wiretapping.)

   $ add-on security
      (N) The retrofitting of protection mechanisms, implemented by
      hardware or software, in an information system after the system
      has become operational. [FP039] (Compare: baked-in security.)



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   $ adequate security
      (O) /U.S. DoD/ "Security commensurate with the risk and magnitude
      of harm resulting from the loss, misuse, or unauthorized access to
      or modification of information." (See: acceptable risk, residual


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      risk.)

   $ administrative security
      1. (I) Management procedures and constraints to prevent
      unauthorized access to a system. (See: (third law under)
      Courtney's laws, "third law" under
      "Courtney's laws", operational security, procedural security,
      security architecture. Compare: technical security.)

      Examples: Clear delineation and separation of duties;
      configuration control.

      Usage: Administrative security is usually understood to consist of
      methods and mechanisms that are implemented and executed primarily
      by people, rather than by automated systems.

      2. (O) "The management constraints, operational procedures,
      accountability procedures, and supplemental controls established
      to provide an acceptable level of protection for sensitive data."
      [FP039]

   $ administrator
      1. (O) /Common Criteria/ A person that is responsible for
      configuring, maintaining, and administering the TOE in a correct
      manner for maximum security. (See: administrative security.)

      2. (O) /ITSEC/ A person in contact with the TOE, who is
      responsible for maintaining its operational capability.

   $ Advanced Encryption Standard (AES)
      (N) A U.S. Government standard [FP197] (the successor to DES) that
      (a) specifies the "the AES algorithm", which is a symmetric block
      cipher that is based on Rijndael and uses key sizes of 128, 192,
      or 256 bits to operate on a 128-bit block, and (b) states policy
      for using that algorithm to protect unclassified, sensitive data.

      Tutorial: Rijndael was designed to handle additional block sizes
      and key lengths that were not adopted in the AES. Rijndael was
      selected by NIST through a public competition that was held to
      find a successor to the DEA; the other finalists were MARS, RC6,
      Serpent, and Twofish.

   $ adversary
      1. (I) An entity that attacks a system. (Compare: intruder.)

      2. (I) An entity that is a threat to a system.

   $ AES
      (N) See: Advanced Encryption Standard.


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   $ Affirm
      (O) A formal methodology, language, and integrated set of software
      tools developed at the University of Southern California's


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      Information Sciences Institute for specifying, coding, and
      verifying software to produce correct and reliable programs.
      [Cheh]

   $ aggregation
      (I) A circumstance in which a collection of information items is
      required to be classified at a higher security level than any of
      the items is classified individually. (See: classification.)

   $ AH
      (I) See: Authentication Header

   $ air gap
      (I) An interface between two systems at which (a) they are not
      connected physically and (b) any logical connection is not
      automated (i.e., data is transferred through the interface only
      manually, under human control). (See: sneaker net.) net. Compare:
      gateway.)

      Example: Computer A and computer B are on opposite sides of a
      room. To move data from A to B, a person carries a floppy disk
      across the room. If A and B operate in different security domains,
      than moving data across the air gap may involve an upgrade or
      downgrade operation.

   $ ALC
      (O) See: accounting legend code.

   $ algorithm
      (I) A finite set of step-by-step instructions for a problem-
      solving or computation procedure, especially one that can be
      implemented by a computer. (See: cryptographic algorithm.)

   $ alias
      (I) A name that an entity uses in place of its real name, usually
      for the purpose of either anonymity or masquerade.

   $ Alice and Bob
      (I) The parties that are most often called upon to illustrate the
      operation of bipartite security protocols. These and other
      dramatis personae are listed by Schneier [Schn].

   $ American National Standards Institute (ANSI)
      (N) A private, not-for-profit association that administers U.S.
      private sector voluntary standards.

      Tutorial: ANSI has approximately 1,000 member organizations,
      including equipment users, manufacturers, and others. These


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      include commercial firms, government agencies, and other
      institutions and international entities.

      ANSI is the sole U.S. representative to the two major non-treaty
      international standards organizations, (1) ISO and, via and (2) (via the
      U.S.


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      Commission (IEC). (IEC), which are the two major, non-treaty,
      international standards organizations.

      ANSI provides a forum for ANSI-accredited standards development
      groups. Among those groups, the following are especially relevant
      to Internet security:
      -  International Committee for Information Technology
         Standardization (INCITS) (formerly X3): Primary U.S. focus of
         standardization in information and communications technologies,
         encompassing storage, processing, transfer, display,
         management, organization, and retrieval of information.
         Example: [A3092].
      -  Accredited Standards Committee X9: Develops, establishes,
         maintains, and promotes standards for the financial services
         industry. Example: [A9009].
      -  Alliance for Telecommunications Industry Solutions (ATIS):
         Develops standards, specifications, guidelines, requirements,
         technical reports, industry processes, and verification tests
         for interoperability and reliability of telecommunications
         networks, equipment, and software. Example: [A1523].

   $ American Standard Code for Information Interchange (ASCII)
      (N) A scheme that encodes 128 specified characters -- the numbers
      0-9, the letters a-z and A-Z, some basic punctuation symbols, some
      control codes that originated with Teletype machines, and a blank
      space -- into the 7-bit binary numbers. Forms the basis of the
      character set representations used in most computers and many
      Internet standards. [FP001] (See: code.)

   $ Anderson report
      (O) A 1972 study of computer security that was written by James P.
      Anderson for the U.S. Air Force [Ande].

      Tutorial: Anderson collaborated with a panel of experts to study
      Air Force requirements for multilevel security. The study
      recommended research and development that was urgently needed to
      provide secure information processing for command and control
      systems and support systems. The report introduced the reference
      monitor concept and provided development impetus for computer and
      network security technology. However, many of the security
      problems that the 1972 report called "current" still plague
      information systems today.

   $ anomaly detection
      (I) A intrusion detection method that searches for activity that
      is different from the normal behavior of system entities and
      system resources. (Compare: (See: IDS. Compare: misuse detection. See: IDS.) detection.)


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   $ anonymity
      (I) The condition of having a name that is unknown or concealed.
      (Compare: privacy. See:
      (See: alias, anonymizer, anonymous credential, anonymous login,
      onion routing, persona certificate.) certificate. Compare: privacy.)

      Tutorial: An application may require security services that
      maintain anonymity of users or other system entities, perhaps to
      preserve their privacy or hide them from attack. To hide an
      entity's real name, an alias may be used. For example, a financial
      institution may assign an account number. Parties to a transaction
      can thus remain relatively anonymous, but can also accept the
      transaction as legitimate. Real names of the parties cannot be


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      easily determined by observers of the transaction, but an
      authorized third party may be able to map an alias to a real name,
      such as by presenting the institution with a court order. In other
      applications, anonymous entities may be completely untraceable.

   $ anonymizer
      (I) A internetwork service, usually provided via a proxy server,
      that provides anonymity and privacy for clients. That is, the
      service enables a client to access servers without allowing the
      anyone to gather information about which servers the client
      accesses and without allowing the accessed servers to gather
      information about the client, such as its IP address.

   $ anonymous credential
      (D) /U.S. Government/ An A credential that (a) can be used to
      authenticate a person as having a specific attribute or being a
      member of a specific group (e.g., military veterans or U.S.
      citizens) but (b) does not reveal the individual identity of the
      person that presents the credential. [M0404] (See: anonymity.)

      Deprecated term: ISDs SHOULD NOT use this term; it mixes concepts
      in a potentially misleading way. For example, when the credential
      is an X.509 certificate, the term could be misunderstood to mean
      that the certificate was signed by a CA that has a persona
      certificate. Instead, use "attribute certificate", "organizational
      certificate", or "persona" "persona certificate" depending on what is meant, with
      and provide additional explanations as needed.

   $ anonymous login
      (I) An access control feature (actually, an access control
      vulnerability) in many Internet hosts that enables users to gain
      access to general-purpose or public services and resources of a
      host (such as allowing any user to transfer data using File
      Transfer Protocol) without having a pre-established, identity-
      specific account (i.e., user name and password). (See: anonymity.)

      Tutorial: This feature exposes a system to more threats than when
      all the users are known, pre-registered entities that are
      individually accountable for their actions. A user logs in using a


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      special, publicly known user name (e.g., "anonymous", "guest", or
      "ftp"). To use the public login name, the user is not required to
      know a secret password and may not be required to input anything
      at all except the name. In other cases, to complete the normal
      sequence of steps in a login protocol, the system may require the
      user to input a matching, publicly known password (such as
      "anonymous") or may ask the user for an e-mail address or some
      other arbitrary character string.

   $ ANSI
      (I)
      (N) See: American National Standards Institute.




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   $ anti-jam
      (N) "Measures ensuring that transmitted information can be
      received despite deliberate jamming attempts." [C4009] (See:
      electronic security, frequency hopping, jam, spread spectrum.)

   $ apex trust anchor
      (N) The trust anchor that is superior to all other trust anchors
      in a particular system or context. (See: trust anchor, top CA.)

   $ API
      (I) See: application programming interface.

   $ APOP
      (I) See: POP3 APOP.

   $ application layer
      (I) Application Layer
      See: Open Systems Interconnection Reference Model (OSIRM). Internet Protocol Suite, OSIRM.

   $ application program
      (I) A computer program that performs a specific function directly
      for a user (as opposed to a program that is part of a computer
      operating system and exists to perform functions in support of
      application programs).

   $ archive
      1a. (I) /noun/ A collection of data that is stored for a
      relatively long period of time for historical and other purposes,
      such as to support audit service, availability service, or system
      integrity service. (Compare: backup, repository.)

      1b. (I) /verb/ To store data in such a way as to create an
      archive. (Compare: back up.)

      Tutorial: A digital signature may need to be verified many years
      after the signing occurs. The CA -- the one that issued the
      certificate containing the public key needed to verify that
      signature -- may not stay in operation that long. So every CA
      needs to provide for long-term storage of the information needed
      to verify the signatures of those to whom it issues certificates.



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   $ ARPANET
      (N)
      (I) Advanced Research Projects Agency (ARPA) Network, a pioneer
      packet-switched network that (a) was designed, implemented,
      operated, and maintained by BBN from January 1969 until July 1975
      under contract to the U.S. Government; (b) led to the development
      of today's Internet; and (c) was decommissioned in June 1990.
      [B4799, Hafn]

   $ ASCII
      (I)
      (N) See: American Standard Code for Information Interchange, a scheme
      that encodes 128 specified characters -- the numbers 0-9, the
      letters a-z and A-Z, some basic punctuation symbols, some control
      codes that originated with Teletype machines, and a blank space --
      into the 7-bit binary numbers. Forms the basis of the character
      set representations used in most computers and many Internet
      standards. (See: code.)



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   $ ASN.1
      (I)
      (N) See: Abstract Syntax Notation One.

   $ asset
      (I) A system resource that is (a) required to be protected by an
      information system's security policy, (b) intended to be protected
      by a countermeasure, or (c) required for a system's mission.

   $ association
      (I) A cooperative relationship between system entities, usually
      for the purpose of transferring information between them. (See:
      security association.)

   $ assurance
      See: security assurance.

   $ assurance level
      (I)
      (N) A rank on a hierarchical scale of that judges the confidence
      someone can have that a TOE adequately fulfills stated security
      requirements. (See: assurance, certificate policy, EAL, TCSEC.)

      Example: U.S. Government guidance [M0404] describes four assurance
      levels for identity authentication, where each level "describes
      the [Government] agency~Os agency's degree of certainty that the user has
      presented [a credential] that refers to [the user's] identity." In
      that guidance, "assurance is defined as (a) "the degree of
      confidence in the vetting process used to establish the identity
      of the individual to whom the credential was issued" and (b) "the
      degree of confidence that the individual who uses the credential
      is the individual to whom the credential was issued."

      The four levels are described as follows:
      -  Level 1: Little or no confidence in the asserted identity.
      -  Level 2: Some confidence in the asserted identity.
      -  Level 3: High confidence in the asserted identity.
      -  Level 4: Very high confidence in the asserted identity.

      Standards for determining these levels are provided in a NIST
      publication [SP12]. However, as noted there, an assurance level is
      "a degree of confidence, not a true measure of how secure the
      system actually is. This distinction is necessary because it is


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      extremely difficult -- and in many cases virtually impossible --
      to know exactly how secure a system is."

   $ asymmetric cryptography
      (I) A modern branch of cryptography (popularly known as "public-
      key cryptography") in which the algorithms use a pair of keys (a
      public key and a private key) and use a different component of the
      pair for each of two counterpart cryptographic operations (e.g.,
      encryption and decryption, or signature creation and signature
      verification). (See: key pair, symmetric cryptography.)

      Tutorial: Asymmetric algorithms have key management advantages


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      over equivalently strong symmetric ones. First, one key of the
      pair need not be known by anyone but its owner; so it can more
      easily be kept secret. Second, although the other key is shared by
      all entities that use the algorithm, that key need not be kept
      secret from other, non-using entities; thus, the key distribution key-distribution
      part of key management can be done more easily.

      Asymmetric cryptography can be used to create algorithms for
      encryption, digital signature, and key agreement:
      -  In an asymmetric encryption algorithm (e.g., see: RSA), when
         Alice wants to ensure confidentiality for data she sends to
         Bob, she encrypts the data with a public key provided by Bob.
         Only Bob has the matching private key that is needed to decrypt
         the data. (Compare: seal.)
      -  In an asymmetric digital signature algorithm (e.g., see: DSA),
         when Alice wants to ensure data integrity or provide
         authentication for data she sends to Bob, she uses her private
         key to sign the data (i.e., create a digital signature based on
         the data). To verify the signature, Bob uses the matching
         public key that Alice has provided.
      -  In an asymmetric key agreement key-agreement algorithm (e.g., see: Diffie-
         Hellman), Alice and Bob each send their own public key to the
         other party. Then each uses their own private key and the
         other's public key to compute the new key value.

   $ asymmetric key
      (I) A cryptographic key that is used in an asymmetric
      cryptographic algorithm. (See: asymmetric cryptography, private
      key, public key.)

   $ ATIS
      (N) See: (Alliance "Alliance for Telecommunications Industry Solutions
      under) ANSI. Solutions"
      under "ANSI".

   $ attack
      1. (I) An intentional act by which an entity attempts to evade
      security services and violate the security policy of a system.
      That is, an actual assault on system security that derives from an
      intelligent threat. (See: penetration, violation, vulnerability.)



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      2. (I) A method or technique used in an assault (e.g.,
      masquerade). (See: distributed attack.)

      Tutorial: Attacks can be characterized according to intent:
      -  An "active attack" attempts to alter system resources or affect
         their operation.
      -  A "passive attack" attempts to learn or make use of information
         from the system but does not affect system resources. (E.g.,
         see: wiretapping.)

      The object of a passive attack might be to obtain data that is
      needed for an off-line attack.
      -  An "off-line attack" is one in which the attacker obtains data
         from the target system and then analyzes the data on a
         different system of the attacker's own choosing, possibly in
         preparation for a second stage of attack on the target.



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      Attacks can be characterized according to point of initiation:
      -  An "inside attack" is one that is initiated by an entity inside
         the security perimeter (an "insider"), i.e., an entity that is
         authorized to access system resources but uses them in a way
         not approved by those who granted the authorization.
      -  An "outside attack" is initiated from outside the perimeter, by
         an unauthorized or illegitimate user of the system (an
         "outsider"). In the Internet, potential outside attackers range
         from amateur pranksters to organized criminals, international
         terrorists, and hostile governments.

      The term "attack" relates to some other basic security terms as
      shown in the following diagram:

      + - - - - - - - - - - - - +  + - - - - +  + - - - - - - - - - - -+
      | An Attack:              |  |Counter- |  | A System Resource:   |
      | i.e., A Threat Action   |  | measure |  | Target of the Attack |
      | +----------+            |  |         |  | +-----------------+  |
      | | Attacker |<==================||<=========                 |  |
      | |   i.e.,  |   Passive  |  |         |  | |  Vulnerability  |  |
      | | A Threat |<=================>||<========>                 |  |
      | |  Agent   |  or Active |  |         |  | +-------|||-------+  |
      | +----------+   Attack   |  |         |  |         VVV          |
      |                         |  |         |  | Threat Consequences  |
      + - - - - - - - - - - - - +  + - - - - +  + - - - - - - - - - - -+

   $ attack potential
      (I) The perceived likelihood of success should an attack be
      launched, expressed in terms of the attacker's capability ability (i.e.,
      expertise and resources) and motivation. (Compare: threat, risk.)

   $ attack sensing, warning, and response
      (I) A set of security services that cooperate with audit service
      to detect and react to indications of threat actions, including
      both inside and outside attacks. (See: indicator.)


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   $ attack tree
      (I) A branching, hierarchical data structure that represents a set
      of potential approaches to achieving an event in which system
      security is penetrated or compromised in a specified way. [Moor]

      Tutorial: Attack trees are special cases of fault trees. The
      security incident that is the goal of the attack is represented as
      the root node of the tree, and the ways that an attacker could
      reach that goal are iteratively and incrementally represented as
      branches and subnodes of the tree. Each subnode defines a subgoal,
      and each subgoal may have its own set of further subgoals, etc.
      The final nodes on the paths outward from the root, i.e., the leaf
      nodes, represent different ways to initiate an attack. Each node
      other than a leaf is either an AND-node or an OR-node. To achieve
      the goal represented by an AND-node, the subgoals represented by
      all of that node's subnodes must be achieved; and for an OR-node,


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      at least one of the subgoals must be achieved. Branches can be
      labeled with values representing difficulty, cost, or other attack
      attributes, so that alternative attacks can be compared.

   $ attribute
      1. (N) The information of a particular type concerning an
      identifiable system entity or object. An "attribute type" is the
      component of an attribute that indicates the class of information
      given by the attribute; and an "attribute value" is a particular
      instance of the class of information indicated by an attribute
      type. (See: attribute certificate.)

   $ attribute authority (AA)
      1. (I) (N) A CA that issues attribute certificates.

      2. (O) "An authority [that] assigns privileges by issuing
      attribute certificates." [X509]

      Usage:

      Deprecated Abbreviation: The abbreviation "AA" should not SHOULD NOT be used
      in an ISD unless it is first defined in the ISD.

   $ attribute certificate
      1. (I) A digital certificate that binds a set of descriptive data
      items, other than a public key, either directly to a subject name
      or to the identifier of another certificate that is a public-key
      certificate. (See: capability token.)

      2. (N) (O) "A data structure, digitally signed by an [a]ttribute
      [a]uthority, that binds some attribute values with identification
      information about its holder." [X509]

      Tutorial: A public-key certificate binds a subject name to a
      public key value, along with information needed to perform certain
      cryptographic functions. functions using that key. Other attributes of a
      subject, such as a security clearance, may be certified in a


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      separate kind of digital certificate, called an attribute
      certificate. A subject may have multiple attribute certificates
      associated with its name or with each of its public-key
      certificates.

      An attribute certificate might be issued to a subject in the
      following situations:
      -  Different lifetimes: When the lifetime of an attribute binding
         is shorter than that of the related public-key certificate, or
         when it is desirable not to need to revoke a subject's public
         key just to revoke an attribute.
      -  Different authorities: When the authority responsible for the
         attributes is different than the one that issues the public-key
         certificate for the subject. (There is no requirement that an
         attribute certificate be issued by the same CA that issued the
         associated public-key certificate.)




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   $ audit
      See: security audit.

   $ audit log
       (I) Synonym for "security audit trail".

   $ audit service
      (I) A security service that records information needed to
      establish accountability for system events and for the actions of
      system entities that cause them. (See: security audit.)

   $ audit trail
      (I) See: security audit trail.

   $ AUTH
      (I) See: POP3 AUTH.

   $ authentic signature
      (I) A signature (especially a digital signature) that can be
      trusted because it can be verified. (See: validate vs. verify.)

   $ authenticate
      (I) Verify (i.e., establish the truth of) an identity claimed by
      or for a system entity. (See: authentication, validate vs. verify,
      ("relationship
      "relationship between data integrity service and authentication
      services" under) data under "data integrity service.).) service".)

      Deprecated Usage: In general English usage, this term is used with
      the meaning "to prove genuine" (e.g., an art expert authenticates
      a Michelangelo painting); but this Internet definition restricts
      usage as follows:
      -  ISDs SHOULD NOT use this term to refer to proving or checking
         that data has not been changed, destroyed or lost in an
         unauthorized or accidental manner. Instead use "verify".
      -  ISDs SHOULD NOT use this term to refer to proving the truth or


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         accuracy of a fact or value such as a digital signature.
         Instead, use "verify".
      -  ISDs SHOULD NOT use this term to refer to establishing the
         soundness or correctness of a construct, such as a digital
         certificate. Instead, use "validate".

   $ authentication
      (I) The process of verifying an identity claimed by or for a
      system entity. (See: authenticate, authentication exchange,
      authentication information, credential, data origin
      authentication, peer entity authentication, simple authentication,
      strong authentication, X.509. Also see: ("relationship "relationship between
      data integrity service and authentication services" under) data under "data
      integrity service.) service", simple authentication, strong authentication,
      X.509.)

      Tutorial: An authentication process consists of two steps:
      -  Identification step: Presenting an identifier to the security


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         system. (Identifiers should be assigned carefully, because
         authenticated identities are the basis for other security
         services, such as access control service.)
      -  Verification step: Presenting or generating authentication
         information that acts as evidence to prove the binding between
         the claimant and the identifier. (See: verification.)

   $ authentication code
      (D) Synonym for a checksum based on cryptography. (Compare:
      Message Authentication Code.)

      Deprecated Term: ISDs SHOULD NOT use this term as a synonym for
      any form of checksum, cryptographic or not; the term mixes
      concepts in a potentially misleading way. not. Instead, use
      "checksum", "error detection code", "hash", "keyed hash", "Message
      Authentication Code", or "protected checksum", depending on what
      is meant.

      The term mixes concepts in a potentially misleading way. The word
      "authentication" is misleading because the checksum may be used to
      perform a data integrity function rather than a data origin
      authentication function. The word "code" is misleading because it
      suggests either that encoding or encryption is involved or that
      the term refers to computer software.

   $ authentication exchange
      1. (I) A mechanism to verify the identity of an entity by means of
      information exchange.

      2. (O) "A mechanism intended to ensure the identity of an entity
      by means of information exchange." [I7498 Part 2]

   $ Authentication Header (AH)
      (I) An Internet protocol [R2402] designed to provide
      connectionless data integrity service and connectionless data
      origin authentication service for IP datagrams, and (optionally)


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      to provide partial sequence integrity and protection against
      replay attacks. (See: IPsec. Compare: ESP.)

      Tutorial: Replay protection may be selected by the receiver when a
      security association is established. AH authenticates upper-layer
      protocol data units the upper-
      layer PDU that is carried as an IP SDU, and also authenticates as
      much of the IP header PCI (i.e., the IP header) as possible. However,
      some IP header fields may change in transit, and the value of
      these fields, when the packet arrives at the receiver, may not be
      predictable by the sender. Thus, the values of such fields cannot
      be protected end-to-end by AH; protection of the IP header by AH
      is only partial when such fields are present.

      AH may be used alone, or in combination with the ESP, or in a
      nested fashion with tunneling. Security services can be provided
      between a pair of communicating hosts, between a pair of
      communicating security gateways, or between a host and a gateway.
      ESP can provide nearly the same security services as AH, and ESP


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      can also provide data confidentiality service. The main difference
      between authentication services provided by ESP and AH is the
      extent of the coverage; ESP does not protect IP header fields
      unless they are encapsulated by AH.

   $ authentication information
      (I) Information used to verify an identity claimed by or for an
      entity. (See: authentication, credential, user. Compare:
      identification information.)

      Tutorial: Authentication information may exist as, or be derived
      from, one of the following: (a) Something the entity knows (see:
      password); (b) something the entity possesses (see: token); (c)
      something the entity is (see: biometric authentication).

   $ authentication service
      (I) A security service that verifies an identity claimed by or for
      an entity. (See: authentication.)

      Tutorial: In a network, there are two general forms of
      authentication service: data origin authentication service and
      peer entity authentication service.

   $ authenticity
      (I) The property of being genuine and able to be verified and be
      trusted. (See: authenticate, authentication, validate vs. verify.)

   $ authority
      (D) "An entity, responsible for the issuance of certificates."
      [X509]

      Deprecated Term: ISDs SHOULD NOT use this term as a synonym for
      attribute authority, certification authority, registration
      authority, or similar terms; the shortened form may cause


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      confusion. Instead, use the full term at the first instance of
      usage and then, if it is necessary to shorten text, use AA, CA,
      RA, and other abbreviations defined in this Glossary.

   $ authority certificate
      (D) "A certificate issued to an authority (e.g. either to a
      certification authority or to an attribute authority)." [X509]
      (See: authority.)

      Deprecated Term: ISDs SHOULD NOT use this term as defined here; it
      is ambiguous. Instead, use the full term "certification authority
      certificate", "attribute authority certificate", "registration
      authority certificate", etc. at the first instance of usage and
      then, if it is necessary to shorten text, use AA, CA, RA, and
      other abbreviations defined in this Glossary.

   $ Authority Information Access extension
      (I) The private extension defined by PKIX for X.509 certificates
      to indicate "how to access CA information and services for the
      issuer of the certificate in which the extension appears.
      Information and services may include on-line validation services
      and CA policy data." [R3280] (See: private extension.)

   $ authorization
      1a. (I) An approval that is granted to a system entity to access a


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      system resource. (Compare: permission, privilege.)

      Usage: Some synonyms are "permission" and "privilege". Specific
      terms are preferred in certain contexts:
      -  /PKI/ "Authorization" SHOULD be used, to align with
         "certification authority" in the standard [X509].
      -  /role-based access control/ "Permission" SHOULD be used, to
         align with the standard [ANSI].
      -  /computer operating systems/ "Privilege" SHOULD be used, to
         align with the literature. (See: privileged process, privileged
         user.)

      Tutorial: The semantics and granularity of authorizations depend
      on the application and implementation (see: (first law under)
      Courtney's laws). "first law" under
      "Courtney's laws"). An authorization may specify a particular
      access mode -- such as read, write, or execute -- for one or more
      system resources.

      1b. (I) A process for granting approval to a system entity to
      access a system resource.

      2. (O) /SET/ "The process by which a properly appointed person or
      persons grants permission to perform some action on behalf of an
      organization. This process assesses transaction risk, confirms
      that a given transaction does not raise the account holder's debt
      above the account's credit limit, and reserves the specified
      amount of credit. (When a merchant obtains authorization, payment


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      for the authorized amount is guaranteed -- provided, of course,
      that the merchant followed the rules associated with the
      authorization process.)" [SET2]

   $ authorization credential
      (I) See: ("access control" context under) /access control/ under "credential".

   $ authorize
      (I) Grant an authorization to a system entity.

   $ authorized user
      (I) /access control/ A system entity that accesses a system
      resource for which the entity has received an authorization.
      (Compare: insider, outsider, unauthorized user.)

      Deprecated Usage: The ISDs that use this term SHOULD state a
      definition for it because the term is used in many ways and could
      easily be
      misunderstood; ISD that use this term SHOULD state a definition
      for it. misunderstood.

   $ automated information system
      See: information system.

   $ availability
      1. (I) The property of a system or a system resource being
      accessible, or usable or operational upon demand, by an authorized
      system entity, according to performance specifications for the


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      system; i.e., a system is available if it provides services
      according to the system design whenever users request them. (See:
      critical, denial of service. Compare: precedence, reliability,
      survivability.)

      2. (O) "The property of being accessible and usable upon demand by
      an authorized entity." [I7498 Part 2]

      Tutorial: This service addresses the security concerns raised by
      denial-of-service attacks. It depends on proper management and
      control of system resources, and thus depends on access control
      service and other security services.

      Availability requirements can be specified by quantitative
      metrics, but sometimes are stated qualitatively, such as in the
      following:
      -  "Flexible tolerance for delay" may mean that brief system
         outages do not endanger mission accomplishment, but extended
         outages may endanger the mission.
      -  "Minimum tolerance for delay" may mean that mission
         accomplishment requires the system to provide requested
         services in a short time.

   $ availability service
      (I) A security service that protects a system to ensure its
      availability.


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      Tutorial: This service addresses the security concerns raised by
      denial-of-service attacks. It depends on proper management and
      control of system resources, and thus depends on access control
      service and other security services.

   $ B1 computer system, B2 computer system, avoidance
      (I) See: secondary definition under "security".

   $ B1, B2, or B3 computer system
      (O) /TCSEC/ See: TCSEC. Tutorial under "Trusted Computer System
      Evaluation Criteria".

   $ back door
      1. (I) /computer security/ A computer system feature -- which may
      be (a) an unintentional flaw, (b) a mechanism deliberately
      installed by the system's creator, or (c) a mechanism
      surreptitiously installed by an intruder -- that provides access
      to a system resource by other than the usual procedure and usually
      is hidden or otherwise not well-known. (Compare: Trojan Horse.
      See: (See: maintenance hook.) hook.
      Compare: Trojan Horse.)

      Example: A way to access a computer other than through a normal
      login. Such an access path is not necessarily designed with
      malicious intent; operating systems sometimes are shipped by the
      manufacturer with hidden accounts intended for use by field
      service technicians or the vendor's maintenance programmers.

      2. (I) /cryptography/ A feature of a cryptographic system that
      makes it easily possible to break or circumvent the protection
      that the system is designed to provided.

      Example: A feature that makes it possible to decrypt cipher text
      much more quickly than by brute force cryptanalysis, without
      having prior knowledge of the decryption key.

   $ back up
      (I) /verb/ Create a reserve copy of data (compare: archive) or, more generally,
      provide alternate means to perform system functions despite loss
      of system resources. (See: contingency
      plan.) plan. Compare: archive.)

   $ backup
      (I) /noun or adjective/ Refers to alternate means of performing
      system functions despite loss of system resources. (See:


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      contingency plan).

      Example: A reserve copy of data, preferably one that is stored
      separately from the original, for use if the original becomes lost
      or damaged. (Compare: archive.)

   $ baggage
      (O) /SET/ An "opaque encrypted tuple, which is included in a SET


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      message but appended as external data to the PKCS encapsulated
      data. This avoids superencryption of the previously encrypted
      tuple, but guarantees linkage with the PKCS portion of the
      message." [SET2]

      Deprecated Usage: ISDs SHOULD NOT use this term to describe a data
      element, except in the form "SET(trademark) baggage" with the
      meaning given above.

   $ baked-in security
      (I) The inclusion of security mechanisms in an information system
      beginning at an early point in the system's life cycle, i.e.,
      during the design phase, or at least early in the implementation
      phase. (Compare: add-on security.)

      Deprecated Term: It is likely that other cultures have use different
      metaphors for this concept. Therefore, to ensure avoid international
      understanding,
      misunderstanding, ISDs SHOULD NOT use this term. (See: (Deprecated Deprecated
      Usage under) Green Book.) under "Green Book".)

   $ bandwidth
      (I) The total width of the frequency band that is available to or
      used by a communication channel; usually expressed in Hertz (Hz).
      [R3753]
      (RFC 3753) (Compare: channel capacity.)

   $ bank identification number (BIN)
      1. (O) The digits of a credit card number that identify the
      issuing bank. (See: primary account number.)

      2. (O) /SET/ The first six digits of a primary account number.

   $ Basic Encoding Rules (BER)
      (I) A standard for representing ASN.1 data types as strings of
      octets. [X690] (See: Distinguished Encoding Rules.)

      Deprecated Usage: Sometimes incorrectly included under the term ASN.1, which treated as part of ASN.1.
      However, ASN.1 properly refers only to the a syntax description
      language, and not to the encoding rules for the language.

   $ Basic Security Option
      (I) See: (secondary secondary definition under) IPSO. under "IPSO".

   $ bastion host
      (I) A strongly protected computer that is in a network protected


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      by a firewall (or is part of a firewall) and is the only host (or
      one of only a few) in the network that can be directly accessed
      from networks on the other side of the firewall. (See: firewall.)

      Tutorial: Filtering routers in a firewall typically restrict
      traffic from the outside network to reaching just one host, the
      bastion host, which usually is part of the firewall. Since only
      this one host can be directly attacked, only this one host needs


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      to be very strongly protected, so security can be maintained more
      easily and less expensively. However, to allow legitimate internal
      and external users to access application resources through the
      firewall, higher layer protocols and services need to be relayed
      and forwarded by the bastion host. Some services (e.g., DNS and
      SMTP) have forwarding built in; other services (e.g., TELNET and
      FTP) require a proxy server on the bastion host.

   $ BBN Technologies
      (O) The research-and-development company (originally called Bolt
      Baranek and Newman, Inc.) that built the ARPANET.

   $ BCA
      (O) See: brand certification authority.

   $ BCR (black/crypto/red)
      (N) An experimental, end-to-end, network packet encryption system
      developed in a working prototype form by BBN and the Collins Radio
      division of Rockwell Corporation in the 1975-1980 time frame for
      the U.S. DoD. BCR was the first network security system to support
      TCP/IP traffic, and it incorporated the first DES chips that were
      validated by the U.S. National Bureau of Standards (now called
      NIST). BCR also was the first to use a KDC and an ACC to manage
      connections.
      (O) See: BLACK/Crypto/RED.

   $ BCI
      (O) See: brand CRL identifier.

   $ Bell-LaPadula model
      (N) A formal, mathematical, state-transition model of
      confidentiality policy for multilevel-secure computer systems
      [Bell]. (Compare: Biba model, Brewer-Nash model.)

      Tutorial: The model, devised by David Bell and Leonard LaPadula at
      The MITRE Corporation in 1973, characterizes computer system
      elements as subjects and objects. To determine whether or not a
      subject is authorized for a particular access mode on an object,
      the clearance of the subject is compared to the classification of
      the object. The model defines the notion of a "secure state", in
      which the only permitted access modes of subjects to objects are
      in accordance with a specified security policy. It is proven that
      each state transition preserves security by moving from secure
      state to secure state, thereby proving that the system is secure.
      In this model, a multilevel-secure system satisfies several rules,


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      including the "confinement property" (also called "*-property",
      pronounced "star property"), (a.k.a. the "*-property"),
      the "simple security property", and the "tranquillity property".

   $ benign
      (N) "Condition of cryptographic data [such] that [it] cannot be
      compromised by human access [to the data]." [C4009]

   $ benign fill
      (N) Process by which keying material is generated, distributed,
      and placed into an ECU without exposure to any human or other
      system entity, except the cryptographic module that consumes and
      uses the material.

   $ BER
      (I) See: Basic Encoding Rules.

   $ beyond


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     A1
      1. (O) /formal/ A level of security assurance that is beyond the
      highest level (level A1) of criteria specified by the TCSEC. (See:
      Tutorial under "Trusted Computer System Evaluation Criteria".)

      2. (O) /informal/ A level of trust so high that it is beyond
      state-of-the-art technology; i.e., it cannot be provided or
      verified by currently available assurance methods, and especially
      not by currently available formal methods.

   $ Biba integrity
      (N) Synonym for "source integrity".

   $ Biba model
      (N) A formal, mathematical, state-transition model of integrity
      policy for multilevel-secure computer systems [Biba]. (Compare: (See: source
      integrity. Compare: Bell-LaPadula model.)

      Tutorial: This model for integrity control is analogous to the
      Bell-LaPadula model for confidentiality control. Each subject and
      object is assigned an integrity level and, to determine whether or
      not a subject is authorized for a particular access mode on an
      object, the integrity level of the subject is compared to that of
      the object. The model prohibits the changing of information in an
      object by a subject with a lesser or incomparable level. The rules
      of the Biba model are duals of the corresponding rules in the
      Bell-LaPadula model.

   $ billet
      (N) A position or assignment that can be filled by one system
      entity at a time. [JCSP1] (Compare: principal, role, user.)

      Tutorial: In an organization, a "billet" is a populational
      position, of which there is exactly one instance; but a "role" is
      functional position, of which there can be multiple instances.
      System entities are in one-to-one relationships with their
      billets, but may be in many-to-one and one-to-many relationships
      with their roles.



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   $ BIN
      (O) See: bank identification number.

   $ bind
      (I) To inseparably associate by applying some mechanism.

      Example: A CA uses creates a public-key certificate by using a digital
      signature to bind together (a) a subject and name, (b) a public key,
      and possibly usually (c) some additional,
      secondary additional data items, to create a items (e.g., see "X.509
      public-key certificate. certificate").




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   $ biometric authentication
      (I) A method of generating authentication information for a person
      by digitizing measurements of a physical or behavioral
      characteristic, such as a fingerprint, hand shape, retina pattern,
      voiceprint, handwriting style, or face.

   $ birthday attack
      (I) A class of attacks against cryptographic functions, including
      both encryption functions and hash functions. The attacks take
      advantage of a statistical property: Given a cryptographic
      function having an N-bit output, the probability is greater than
      1/2 that for 2**(N/2) randomly chosen inputs, the function will
      produce at least two outputs that are identical. (See: (discussion
      under) hash function.) Tutorial
      under "hash function".)

      Derivation: From the somewhat surprising fact (often called the
      "birthday paradox") that although there are 365 days in a year,
      the probability is greater than 1/2 that two of more people share
      the same birthday in any randomly chosen group of 23 people.

      Birthday attacks enable an adversary to find two inputs for which
      a cryptographic function produces the same cipher text (or find
      two inputs for which a hash functions produces the same hash
      result) much faster than a brute force attack can; and a clever
      adversary can use such a capability to create considerable
      mischief. However, no birthday attack can enable an adversary to
      decrypt a given cipher text (or find a hash input that results in
      a given hash result) any faster than a brute force attack can.

   $ bit
      (I) A contraction of the term "binary digit", digit"; the smallest unit of
      information storage, which has two possible states or values. The
      values that
      are usually are represented by the symbols "0" (zero) and "1"
      (one). (See: block, byte, word.)

   $ bit string
      (I) A sequence of bits, each of which is either "0" or "1".

   $ BLACK
      1. (I) Designation for data that consists only of cipher text, and
      for information system equipment items or facilities that handle
      only cipher text. Example: "BLACK key".(Compare: RED. See: key".(See: color change,
      RED/BLACK separation.) separation. Compare: RED.)

      2. (O) /U.S. Government/ "Designation applied to information
      systems, and to associated areas, circuits, components, and
      equipment, in which national security information is encrypted or
      is not processed. [C4009]

   $ BLACK/Crypto/RED (BCR)
      (N) An experimental, end-to-end, network packet encryption system
      developed in a working prototype form by BBN and the Collins Radio


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      division of Rockwell Corporation in the 1975-1980 time frame for
      the U.S. DoD. BCR was the first network security system to support
      TCP/IP traffic, and it incorporated the first DES chips that were
      validated by the U.S. National Bureau of Standards (now called
      NIST). BCR also was the first to use a KDC and an ACC to manage
      connections.

   $ BLACK key
      (I) A key that is protected with a key-encrypting key and that


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      must be decrypted before use. (Compare: (See: BLACK. Compare: RED key. See: BLACK.) key.)

   $ BLACKER
      (N)
      (O) An end-to-end encryption system for computer data networks
      that was developed by the U.S. DoD in the 1980s to provide host-
      to-host data confidentiality service for datagrams at OSIRM layer Layer
      3. [Weis] (Compare: Caneware, IPsec.)

      Tutorial: Each user host connects to its own bump-in-the-wire
      encryption device called a BLACKER Front End (BFE, TSEC/KI-111),
      through which the host connects to the subnetwork. The system also
      includes two types of centralized devices: one or more KDCs
      connect to the subnetwork and communicate with assigned sets of
      BFEs, and one or more ACCs connect to the subnetwork and
      communicate with assigned KDCs. BLACKER uses only symmetric
      encryption. A KDC distributes session keys to BFE pairs as
      authorized by an ACC. Each ACC maintains a database for a set of
      BFEs, and the database determines which pairs from that set (i.e.,
      which pairs of user hosts behind the BFEs) are authorized to
      communicate and at what security levels.

      The BLACKER system is MLS in three ways: (a) The BFEs form a
      security perimeter around a subnetwork, separating user hosts from
      the subnetwork, so that the subnetwork can operate at a different
      security level (possibly a lower, less expensive level) than the
      hosts. (b) The BLACKER components are trusted to separate
      datagrams of different security levels, so that each datagram of a
      given security level can be received only by a host that is
      authorized for that security level; and thus BLACKER can separate
      host communities that operate at different security levels. (c)
      The host side of a BFE is itself MLS and can recognize a security
      label on each packet, so that an MLS user host can be authorized
      to successively transmit datagrams that are labeled with different
      security levels.

   $ block
      (I) A bit string or bit vector of finite length. (See: block
      cipher. Compare: byte, word.)

      Usage: An "N-bit block" contains N bits, which usually are
      numbered from left to right as 1, 2, 3, ..., N.




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   $ block cipher
      (I) An encryption algorithm that breaks plain text into fixed-size
      segments and uses the same key to transform each plaintext segment
      into a fixed-size segment of cipher text. Examples: AES, Blowfish,
      DEA, IDEA, RC2, and SKIPJACK. (See: block, mode. Compare: stream
      cipher.)

      Tutorial: A block cipher can be adapted to have a different
      external interface, such as that of a stream cipher, by using a
      mode of cryptographic operation to "package" package the basic algorithm.


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      (See: CBC, CFB, DEA, ECB, OFB.)

   $ Blowfish
      (N) A symmetric block cipher with variable-length key (32 to 448
      bits) designed in 1993 by Bruce Schneier as an unpatented,
      license-free, royalty-free replacement for DES or IDEA. [Schn]
      (See: Twofish.)

   $ brand
      1. (I) A distinctive mark or name that identifies a product or
      business entity.

      2. (O) /SET/ The name of a payment card. (See: BCA.)

      Tutorial: Financial institutions and other companies have founded
      payment card brands, protect and advertise the brands, establish
      and enforce rules for use and acceptance of their payment cards,
      and provide networks to interconnect the financial institutions.
      These brands combine the roles of issuer and acquirer in
      interactions with cardholders and merchants. [SET1]

   $ brand certification authority (BCA)
      (O) /SET/ A CA owned by a payment card brand, such as MasterCard,
      Visa, or American Express. [SET2] (See: certification hierarchy,
      SET.)

   $ brand CRL identifier (BCI)
      (O) /SET/ A digitally signed list, issued by a BCA, of the names
      of CAs for which CRLs need to be processed when verifying
      signatures in SET messages. [SET2]

   $ break
      (I) /cryptography/ To successfully perform cryptanalysis and thus
      succeed in decrypting data or performing some other cryptographic
      function, without initially having knowledge of the key that the
      function requires. (See: penetrate.)

      Usage: This term applies to encrypted data or, more generally, to
      a cryptographic algorithm or cryptographic system.

   $ Brewer-Nash model
      (N) A security model [BN89] to enforce the Chinese wall policy.


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      (Compare: Bell-LaPadula model, Clark-Wilson model.)

      Tutorial: All proprietary information in the set of commercial
      firms F(1), F(2), ..., F(N) is categorized into mutually exclusive
      conflict-of-interest classes I(1), I(2), ..., I(M) that apply
      across all firms. Each firm belongs to exactly one class. The
      Brewer-Nash model has the following mandatory rules:
      -  Brewer-Nash Read Rule: Subject S can read information object O
         from firm F(i) only if either (a) O is from the same firm as
         some object previously read by S *or* (b) O belongs to a class
         I(i) from which S has not previously read any object. (See:
         object, subject.)


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      -  Brewer-Nash Write Rule: Subject S can write information object
         O to firm F(i) only if (a) S can read O by the Brewer-Nash Read
         Rule *and* (b) no object can be read by S from a different firm
         F(j), no matter whether F(j) belongs to the same class as F(i)
         or to a different class.

   $ bridge
      (I) A gateway for traffic flowing at OSIRM layer Layer 2 between two
      networks (usually two LANs). (Compare: router, bridge CA.) CA, router.)

   $ bridge CA
      (I) A PKI consisting of only a CA that cross-certifies with CAs of
      some other PKIs. (See: cross-certification. Compare: bridge.)

      Tutorial: A bridge CA functions as a hub that enables a
      certificate user in any of the PKIs that attach to the bridge, to
      validate certficates certificates issued in the other attached PKIs.

      For example, a bridge CA (BCA)                 CA1
      could cross-certify with four                   ^
      PKIs that have the roots CA1,                   |
      CA2, CA3, and CA4. The cross-                   v
      certificates that the roots            CA2 <-> BCA <-> CA3
      exchange with the BCA enable an                 ^
      end entity EE1 certified under                  |
      under CA1 in PK1 to construct                   v
      a certification path needed to                 CA4
      validate the certificate of
      end entity EE2 under CA2,           CA1 -> BCA -> CA2 -> EE2
      or vice versa.                      CA2 -> BCA -> CA1 -> EE1

   $ British Standard 7799
      (N) Part 1 of the standard is a code of practice for how to secure
      an information system. Part 2 specifies the management framework,
      objectives, and control requirements for information security
      management systems. [BS7799] (See: ISO 17799.)

   $ browser
      (I) An client computer program that can retrieve and display
      information from servers on the World Wide Web. Examples:


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      Netscape's Navigator and Microsoft's Internet Explorer.

   $ brute force
      (I) A cryptanalysis technique or other kind of attack method
      involving an exhaustive procedure that tries a large number of
      possible solutions to the problem, one-by-one.

      Tutorial: In some cases, brute force involves trying all of the
      possibilities. For example, for cipher text where the analyst
      already knows the decryption algorithm, a brute force technique
      for finding matching plain text is to decrypt the message with
      every possible key. In other cases, brute force involves trying a


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      large number of possibilities but substantially fewer than all of
      them. For example, given a hash function that produces a N-bit
      hash result, the probability is greater than 1/2 that the analyst
      will find two inputs that have the same hash result after trying
      only 2**(N/2) random chosen inputs. (See: birthday attack.)

   $ BS7799
      (N) See: British Standard 7799.

   $ buffer overflow
      (I) Any attack technique that exploits a vulnerability resulting
      from computer software or hardware that does not check for
      exceeding the bounds of a storage area when data is written into a
      sequence of storage locations beginning in that area.

      Tutorial: By causing a normal system operation to write data
      beyond the bounds of a storage area, the attacker seeks to either
      disrupt system operation or cause the system to execute malicious
      software inserted by the attacker.

   $ buffer zone
      (I) A neutral internetwork segment used to connect other segments
      that each operate under a different security policy.

      Tutorial: To connect a private network to the Internet or some
      other relatively public network, one could construct a small,
      separate, isolated LAN and connect it to both the private network
      and the public network; one or both of the connections would
      implement a firewall to limit the traffic that could pass through
      the buffer zone.

   $ bulk encryption
      (N) "Simultaneous encryption of all channels of a multichannel
      telecommunications link." [C4009] (Compare: bulk keying material.)

   $ bulk key
      (D) In a few published descriptions of hybrid encryption for SSH,
      Windows 2000, and other applications, this term refers to a
      symmetric key that (a) is used to encrypt a relatively large
      amount of data and (b) is itself encrypted with a public key.


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      (Compare: bulk keying material.)

      Example: To send a large file to Bob, Alice (a) generates a
      symmetric key and uses it to encrypt the file (i.e., encrypt the
      bulk of the information that is to be sent) and then (b) encrypts
      that symmetric key (the "bulk key") with Bob's public key.

      Deprecated Term: ISDs SHOULD NOT use this term or definition; they
      are not well-established and could be confused with the
      established term "bulk keying material". Instead, use "symmetric
      key" and carefully explain how the key is applied.

   $ bulk keying material
      (O)
      (N) Refers to handling keying material in large quantities, e.g.,


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      as a dataset that contains many items of keying material. (See:
      type 0. Compare: bulk key, bulk encryption.)

   $ bump-in-the-stack
      (I) An implementation approach that places a network security
      mechanism inside the system that is to be protected. (Compare:
      bump-in-the-wire.)

      Example: IPsec can be implemented inboard, in the protocol stack
      of an existing system or existing system design, by placing a new
      layer placed between the existing IP layer and the OSIRM layer Layer 3 drivers.
      Source code access for the existing stack is not required, but the
      system that contains the stack does need to be modified [R1401]. [R2401].

   $ bump-in-the-wire
      (I) An implementation approach that places a network security
      mechanism outside of the system that is to be protected. (Compare:
      bump-in-the-stack.)

      Example: IPsec can be implemented outboard, in a physically
      separate device, so that the system that receives the IPsec
      protection does not need to be modified at all [R1401]. [R2401]. Military-
      grade link encryption has mainly been implemented as bump-in-the-
      wire devices.

   $ business case analysis
      (N) An extended form of cost-benefit analysis that considers
      factors beyond financial metrics, including security factors such
      as the requirement for security services, their technical and
      programmatic feasibility, their qualitative benefits, and
      associated risks. (See: risk analysis.)

   $ byte
      (I) A fundamental unit of computer storage; the smallest
      addressable unit in a computer's architecture. Usually holds one
      character of information and, today, usually means eight bits.
      (Compare: octet.)



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      Usage: Understood to be larger than a "bit", but smaller than a
      "word". Although "byte" almost always means "octet" today, some
      computer architectures have had bytes in other sizes (e.g., six
      bits, nine bits). Therefore, an STD SHOULD state the number of
      bits in a byte where the term is first used in the STD.

   $ C field
      (D) See: Compartments field.

   $ C1 computer system, or C2 computer system
      (O) /TCSEC/ See: TCSEC. Tutorial under "Trusted Computer System
      Evaluation Criteria".

   $ CA
      (I) See: certification authority.

   $ CA certificate
      (D) "A [digital] certificate for one CA issued by another CA."
      [X509]

      Deprecated Definition: An ISD that uses ISDs SHOULD NOT use the term SHOULD state


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      precisely with this
      definition; the definition is ambiguous with regard to how the
      certificate is constructed and how it is intended to be used; the X.509 used. ISDs
      that use this term SHOULD provide a technical definition is ambiguous with regard
      to those details. for it.
      (See: certificate profile.)

       - Constraints: A v3 X.509 public-key certificate may have a
         "basicConstraints"

      Tutorial: There is no single, obvious choice for a technical
      definition of this term. Different PKIs can use different
      certificate profiles, and X.509 provides several choices of how to
      issue certificates to CAs. For example, one possible definition is
      the following: A v3 X.509 public-key certificate that has a
      "basicConstraints" extension containing a "cA" value of "TRUE"
         that "TRUE".
      That would specifically indicates indicate that "the certified public key
      may be used to verify certificate signatures."
       - Key Usage: A v3 X.509 public-key certificate signatures", i.e., that the
      private key may be used by a CA.

      However, there also are other ways to indicate such usage. The
      certificate may have a "key Usage" extension which that indicates the
      purposes for which the public key may be used. One purpose used, and one of the
      values that X.509 defines for that extension is "keyCertSign", to
      indicate that the certificate may be used for verifying a CA's
      signature on certificates; and if this value certificates. If "keyCertSign" is present, present in a
      certificate that also has a "basicConstraints" extension, than
      "cA" is also set to "TRUE" if the certificate
         also has a "basicConstraints" in that extension.

      However, Alternatively, a CA could
      be issued a certificate in which "keyCertSign" is asserted without
      "basicConstraints" being present; and an entity that acts as a CA
      could be issued a certificate with "keyUsage" set to other values,
      either with or without "keyCertSign".

   $ Caesar cipher
      (I) A cipher that, given an alphabet of N characters, A(1), A(2),
      character A(i) by A(i+K, mod N) for some 0<K<N+1. [Schn]


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      Examples: (a) During the Gallic wars, Julius Caesar used a cipher
      with K=3. In a Caesar cipher with K=3 for the English alphabet, A
      is replaced by D, B by E, C by F, ..., W by Z, X by A, Y by B, Z
      by C. (b) UNIX systems sometimes include ROT13 "ROT13" software that
      implements a Caesar cipher with K=13 (i.e., ROTate by 13).

   $ call back
      (I) An authentication technique for terminals that remotely access
      a computer via telephone lines; the host system disconnects the
      caller and then reconnects on a telephone number that was
      previously authorized for that terminal.

   $ CAM
      (O) See: Certificate Arbitrator Module.

   $ CANEWARE
      (N)
      (O) A end-to-end encryption system for computer data networks that
      was developed by the U.S. DoD in the 1980s to provide host-to-host
      data confidentiality service for datagrams in OSIRM layer Layer 3.
      [Roge] (Compare: BLACKER, IPsec.)

      Tutorial: Each user host connects to its own bump-in-the-wire
      encryption device called a CANEWARE Front End (CFE), through which
      the host connects to the subnetwork. CANEWARE uses symmetric
      encryption for CFE-to-CFE traffic, but also uses FIREFLY to


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      establish those session keys. The public-key certificates issued
      by the FIREFLY system include credentials for mandatory access
      control. For discretionary access control, the system also
      includes one or more centralized CANEWARE Control Processors
      (CCPs) that connect to the subnetwork, maintain a database for
      discretionary access control authorizations, and communicate those
      authorizations to assigned sets of CFEs.

      The CANEWARE system is MLS in only two of the three ways that
      BLACKER is MLS: (a) Like BLACKER BFEs, CFEs form a security
      perimeter around a subnetwork, separating user hosts from the
      subnetwork, so that the subnetwork can operate at a different
      security level than the hosts. (b) Like BLACKER, the CANEWARE
      components are trusted to separate datagrams of different security
      levels, so that each datagram of a given security level can be
      received only by a host that is authorized for that security
      level; and thus CANEWARE can separate host communities that
      operate at different security levels. (c) Unlike a BFE, the host
      side of a CFE is not MLS, and treats all packets received from a
      user host as being at the same mandatory security level.

   $ capability list
      (I) /information system/ A mechanism that implements access
      control for a system entity by enumerating the system resources
      that the entity is permitted to access and, either implicitly or
      explicitly, the access modes granted for each resource. (Compare:


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      access control list, access control matrix, access profile,
      capability token.)

   $ capability token
      (I) A token, usually an unforgeable data object, that gives the
      bearer or holder the right to access a system resource. Possession
      of the token is accepted by a system as proof that the holder has
      been authorized to access the resource indicated by the token.
      (Compare: access control list. See:
      (See: attribute certificate, capability list, credential, digital
      certificate, ticket.) ticket, token.)

   $ Capability Maturity Model (CMM)
      (N) Method for judging the maturity of software processes in an
      organization and for identifying crucial practices needed to
      increase process maturity. [Chris] (Compare: Common Criteria.)

      Tutorial: The CMM does not specify security evaluation criteria
      (see: assurance level), but its use may improve security
      assurance. The CMM describes principles and practices that can
      improve software processes in terms of evolving from ad hoc
      processes to disciplined processes. The CMM has five levels:
      -  Initial: Software processes are ad hoc or chaotic, and few are
         well-defined. Success depends on individual effort and heroics.
      -  Repeatable: Basic project management processes are established
         to track cost, schedule, and functionality. Necessary process
         discipline is in place to repeat earlier successes on projects
         with similar applications.
      -  Defined: Software process for both management and engineering
         activities is documented, standardized, and integrated into a
         standard software process for the organization. All projects
         use Each project
         uses an approved, tailored version of the organization's
         standard
         software process for developing and maintaining software.
      -  Managed: Detailed measures of software process and product
         quality are collected. Both software process and products are


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         quantitatively understood and controlled.
      -  Optimizing: Continuous process improvement is enabled by
         quantitative feedback from the process and from piloting
         innovative ideas and technologies.

   $ CAPI
      (I) See: cryptographic application programming interface.

   $ CAPSTONE
      (N) An integrated microcircuit (in MYK-8x series manufactured by
      Mykotronx, Inc.) that implements SKIPJACK, KEA, DSA, SHA, and
      basic mathematical functions needed to support asymmetric
      cryptography; has non-deterministic random number generator; and
      supports key escrow. (See: FORTEZZA. Compare: CLIPPER.)

   $ card
      See: cryptographic card, FORTEZZA, payment card, PC card, smart
      card, token.


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   $ card backup
      See: token backup.

   $ card copy
      See: token copy.

   $ card restore
      See: token restore.

   $ cardholder
      1. (I) An entity to whom or to which a card has been issued.

      Usage: Usually refers to a living human being, but may refer to a
      position (see: billet, role) in an organization or to an automated
      process. (See: user.)

      2. (O) /SET/ "The holder of a valid payment card account and user
      of software supporting electronic commerce." [SET2] A cardholder
      is issued a payment card by an issuer. SET ensures that in the
      cardholder's interactions with merchants, the payment card account
      information remains confidential. [SET1]

   $ cardholder certificate
      (O) /SET/ A digital certificate that is issued to a cardholder
      upon approval of the cardholder's issuing financial institution
      and that is transmitted to merchants with purchase requests and
      encrypted payment instructions, carrying assurance that the
      account number has been validated by the issuing financial
      institution and cannot be altered by a third party. [SET1]

   $ cardholder certification authority (CCA)
      (O) /SET/ A CA responsible for issuing digital certificates to
      cardholders and operated on behalf of a payment card brand, an


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      issuer, or another party according to brand rules. A CCA maintains
      relationships with card issuers to allow for the verification of
      cardholder accounts. A CCA does not issue a CRL but does
      distribute CRLs issued by root CAs, brand CAs, geopolitical CAs,
      and payment gateway CAs. [SET2]

   $ CAST
      (N) A design procedure for symmetric encryption algorithms, and a
      resulting family of algorithms, invented by Carlisle Adams (C.A.)
      and Stafford Tavares (S.T.). [R2144, R2612]

   $ category
      (I) A grouping of sensitive information items to which a non-
      hierarchical restrictive security label is applied to increase
      protection of the data. (See: compartment. formal access approval. Compare:
      category, classification.)




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   $ CAW
      (O)
      (N) See: certification authority workstation.

   $ CBC
      (N) See: cipher block chaining.

   $ CCA
      (O) See: cardholder certification authority.

   $ CCEP
      (O) See: Commercial COMSEC Endorsement Program.

   $ CCI
      (O) See: Controlled Cryptographic Item.

   $ CCITT
      (N) Acronym for French translation of International Telephone and
      Telegraph Consultative Committee. Now renamed ITU-T.

   $ CERIAS
      (O) Purdue University's Center for Education and Research in
      Information Assurance and Security, which includes faculty from
      multiple schools and departments and takes a multidisciplinary
      approach to security problems ranging from technical to ethical,
      legal, educational, communicational, linguistic, and economic.

   $ CERT
      (I) See: computer emergency response team.

   $ certificate
      1. (I) /general English/ A document that attests to the truth of
      something or the ownership of something.

      2. (I) /general security/ See: capability, capability token, digital
      certificate.



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      3. (I) /PKI/ See: attribute certificate, public-key certificate.

   $ Certificate Arbitrator Module (CAM)
      (O) An open-source software module that is designed to be
      integrated with an application for the purpose of routing,
      replying to, and otherwise managing and meditating certificate
      validation requests between that application and the CAs in the
      ACES PKI.

   $ certificate authority
      (D) Synonym for "certification authority".

      Deprecated Term: ISDs SHOULD NOT use this term; it looks like
      sloppy suggests
      careless use of the term "certification authority", which is the term
      standardized by X.509. A person who uses this term probably has
      not
      never read the PKI basic technical standards for PKI [X509, R2459]. R3280].


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   $ certificate chain
      (D) Synonym for "certification path". (See: trust chain.)

      Deprecated Term: ISDs SHOULD NOT use this term; it duplicates the
      meaning of a standardized term. Instead, use "certification path".

   $ certificate chain validation
      (D) Synonym for "certificate validation" or "path validation".

      Deprecated Term: ISDs SHOULD NOT use this term; it duplicates the
      meaning of standardized terms and mixes concepts in a potentially
      misleading way. Instead, use "certificate validation" or "path
      validation", depending on what is meant. (See: validate vs.
      verify.)

   $ certificate creation
      (I) The act or process by which a CA sets the values of a digital
      certificate's data fields and signs it. (See: issue.)

   $ certificate expiration
      (I) The event that occurs when a certificate ceases to be valid
      because its assigned lifetime has been exceeded. (See: certificate
      revocation, validity period.)

   $ certificate extension
      (I) See: extension.

   $ certificate holder
      (D) Synonym for "certificate subject". (See: certificate owner.)

      Deprecated Term: ISDs SHOULD NOT use this term as a synonym for
      the subject of a digital certificate; the term is potentially
      ambiguous. For example, the term could refer to a system entity or
      component, such as a repository, that simply has possession of a
      copy of the certificate.


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   $ certificate management
      (I) The functions that a CA may perform during the life cycle of a
      digital certificate, including the following:
      -  Acquire and verify data items to bind into the certificate.
      -  Encode and sign the certificate.
      -  Store the certificate in a directory or repository.
      -  Renew, rekey, and update the certificate.
      -  Revoke the certificate and issue a CRL.
      (See: archive management, certificate management, key management,
      security architecture, token management.)

   $ certificate management authority (CMA)
      (D) /U.S. DoD/ Used to mean either a CA or an RA. [DoD3, SP32]

      Deprecated Term: ISDs SHOULD NOT use this term because it is


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      potentially ambiguous, such as in a context involve ICRLs.
      Instead, use CA, RA, or both, depending on what is meant.

   $ certificate owner
      (D) Synonym for "certificate subject". (See: certificate holder.)

      Deprecated Term: ISDs SHOULD NOT use this term as a synonym for
      the subject of a digital certificate; the term is potentially
      ambiguous. For example, the term could refer to a system entity,
      such as a corporation, that has acquired a certificate to operate
      equipment, such as a Web server.

   $ certificate path
      (D) Synonym for "certification path".

      Deprecated Term: ISDs SHOULD NOT use this term; it looks like
      sloppy suggests
      careless use of "certification path", which is the a term standardized
      by X.509. A person who uses this term probably has not never read the
      PKI
      basic technical standards for PKI [X509, R2459]. R3280].

   $ certificate policy
      (I) "A named set of rules that indicates the applicability of a
      certificate to a particular community and/or class of application
      with common security requirements." [X509] (Compare: CPS.)

      Example: The U.S. DoD's certificate policy [DoD3] defines four
      classes (i.e., assurance levels) for X.509 public-key certificates
      and defines the applicability of those classes. (See: class 2.)

      Tutorial: A certificate policy can help a certificate user to
      decide whether a certificate should be trusted in a particular
      application. "For example, a particular certificate policy might
      indicate applicability of a type of certificate for the
      authentication of electronic data interchange transactions for the
      trading of goods within a given price range." [R2527]



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      A v3 X.509 public-key certificate may have a "certificatePolicies"
      extension that lists certificate policies, recognized by the
      issuing CA, that apply to the certificate and govern its use. Each
      policy is denoted by an object identifier and may optionally have
      certificate policy qualifiers. (See: certificate profile.)

      Each SET certificate specifies at least one certificate policy,
      that of the SET root CA. SET uses certificate policy qualifiers to
      point to the actual policy statement and to add qualifying
      policies to the root policy. (See: SET qualifier.)

   $ certificate policy qualifier
      (I) Information that pertains to a certificate policy and is
      included in a "certificatePolicies" extension in a v3 X.509
      public-key certificate.



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   $ certificate profile
      (I) A specification (e.g., [DoD3, R2459]) R3280]) of the format and
      semantics of public-key certificates or attribute certificates,
      constructed for use in a specific application context by selecting
      from among options offered by a broader standard.

   $ certificate reactivation
      (I) The act or process by which a digital certificate, which a CA
      has designated for revocation but not yet listed on a CRL, is
      returned to the valid state.

   $ certificate rekey
      1. (I) The act or process by which an existing public-key
      certificate has its key value changed by issuing a new certificate
      with a different (usually new) public key. (See: certificate
      renewal, certificate update, rekey.)

      Tutorial: For an X.509 public-key certificate, the essence of
      rekey is that the subject stays the same and a new public key is
      bound to that subject. Other changes are made, and the old
      certificate is revoked, only as required by the PKI and CPS in
      support of the rekey. If changes go beyond that, the process is a
      "certificate update".

      2. (O) /MISSI/ The act or process by which a MISSI CA creates a
      new X.509 public-key certificate that is identical to the old one,
      except the new one has (a) a new, different KEA key or (b) a new,
      different DSS key or (c) new, different KEA and DSS keys. The new
      certificate also has a different serial number and may have a
      different validity period. A new key creation date and maximum key
      lifetime period are assigned to each newly generated key. If a new
      KEA key is generated, that key is assigned a new KMID. The old
      certificate remains valid until it expires, but may not be further
      renewed, rekeyed, or updated.




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   $ certificate renewal
      (I) The act or process by which the validity of the binding
      asserted by an existing public-key certificate is extended in time
      by issuing a new certificate. (See: certificate rekey, certificate
      update.)

      Tutorial: For an X.509 public-key certificate, this term means
      that the validity period is extended (and, of course, a new serial
      number is assigned) but the binding of the public key to the
      subject and to other data items stays the same. The other data
      items are changed, and the old certificate is revoked, only as
      required by the PKI and CPS to support the renewal. If changes go
      beyond that, the process is a "certificate rekey" or "certificate
      update".

   $ certificate request
      (D) Synonym for "certification request".


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      Deprecated Term: ISDs SHOULD NOT use this term; it looks like
      imprecise suggests
      careless use of a the term "certification request", which is
      standardized by PKCS #10 and used in PKIX. Instead, use
      "certification request".

   $ certificate revocation
      (I) The event that occurs when a CA declares that a previously
      valid digital certificate issued by that CA has become invalid;
      usually stated with a effective date.

      Tutorial: In X.509, a revocation is announced to potential
      certificate users by issuing a CRL that mentions the certificate.
      Revocation and listing on a CRL is only necessary prior to the
      certificate's scheduled expiration.

   $ certificate revocation list (CRL)
      1. (I) A data structure that enumerates digital certificates that
      have been invalidated by their issuer prior to when they were
      scheduled to expire. (See: certificate expiration, delta CRL,
      X.509 certificate revocation list.)

      2. (O) "A signed list indicating a set of certificates that are no
      longer considered valid by the certificate issuer. In addition to
      the generic term CRL, some specific CRL types are defined for CRLs
      that cover particular scopes." [X509]

   $ certificate revocation tree
      (I)
      (N) A mechanism for distributing notice of certificate
      revocations; uses a tree of hash results that is signed by the
      tree's issuer. Offers an alternative to issuing a CRL, but is not
      supported in X.509. (See: certificate status responder.)

   $ certificate serial number
      1. (I) An integer value that (a) is associated with, and may be
      carried in, a digital certificate; (b) is assigned to the


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      certificate by the certificate's issuer; and (c) is unique among
      all the certificates produced by that issuer.

      2. (O) "An integer value, unique within the issuing CA, which is
      unambiguously associated with a certificate issued by that CA."
      [X509]

   $ certificate status authority
      (D) /U.S. DoD/ "A trusted entity that provides on-line
      verification to a Relying Party of a subject certificate's
      trustworthiness [should instead say 'validity'], and may also
      provide additional attribute information for the subject
      certificate." [DoD3]

      Deprecated Term: ISDs SHOULD NOT use this term because it is not
      widely accepted; instead, use "certificate status responder" or


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      "OCSP server", or otherwise explain what is meant.

   $ certificate status responder
      (N) /FPKI/ A trusted on-line server that acts for a CA to provide
      authenticated certificate status information to certificate users
      [FPKI]. Offers an alternative to issuing a CRL, but is not
      supported in X.509. (See: certificate revocation tree, OCSP.)

   $ certificate update
      (I) The act or process by which non-key data items bound in an
      existing public-key certificate, especially authorizations granted
      to the subject, are changed by issuing a new certificate. (See:
      certificate rekey, certificate renewal.)

      Usage: For an X.509 public-key certificate, the essence of this
      process is that fundamental changes are made in the data that is
      bound to the public key, such that it is necessary to revoke the
      old certificate. (Otherwise, the process is only a "certificate
      rekey" or "certificate renewal".)

   $ certificate user
      1. (I) A system entity that depends on the validity of information
      (such as another entity's public key value) provided by a digital
      certificate. (See: relying party.)

      2. (O) "An entity that needs to know, with certainty, the public
      key of another entity." [X509]

      Usage: The system entity may be a human being or an organization,
      or a device or process controlled by a human or organization.
      (See: user.)

      3. (D) Synonym for "certificate subject".

      Deprecated Definition: ISDs SHOULD NOT use this term with this
      meaning; the term could be confused with one of the other two


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      definitions given above.

   $ certificate validation
      1. (I) An act or process by which a certificate user establishes
      that the assertions made by a digital certificate can be trusted.
      (See: valid certificate, validate vs. verify.)

      2. (O) "The process of ensuring that a certificate was valid at a
      given time, including possibly the construction and processing of
      a certification path, and ensuring that all certificates in that
      path were valid (i.e. were not expired or revoked) at that given
      time." [X509]

      Tutorial: To validate a certificate, a certificate user checks
      that the certificate is properly formed and signed and is
      currently in force:


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      -  Checks the syntax and semantics: Parses the certificate's
         syntax and interprets its semantics, applying rules specified
         for and by its data fields, such as for critical extensions in
         an X.509 certificate.
      -  Checks the signature: Uses the issuer's public key to verify
         the digital signature of the CA who issued the certificate in
         question. If the verifier obtains the issuer's public key from
         the issuer's own public-key certificate, that certificate
         should be validated, too. That validation may lead to yet
         another certificate to be validated, and so on. Thus, in
         general, certificate validation involves discovering and
         validating a certification path.
      -  Checks currency and revocation: Verifies that the certificate
         is currently in force by checking that the current date and
         time are within the validity period (if that is specified in
         the certificate) and that the certificate is not listed on a
         CRL or otherwise announced as invalid. (CRLs themselves require (The CRLs also must be
         checked by a similar validation process.)

   $ certification
      1. (I) /information system/ Comprehensive evaluation (usually made
      in support of an accreditation action) of an information system's
      technical security features and other safeguards to establish the
      extent to which the system's design and implementation meet a set
      of specified security requirements. [C4009, FP102, SP37] (See:
      accreditation. Compare: evaluation.)

      2. (I) /digital certificate/ The act or process of vouching for
      the truth and accuracy of the binding between data items in a
      certificate. (See: certify.)

      3. (I) /PKI/ The act or process of vouching for the ownership of a
      public key by issuing a public-key certificate that binds the key
      to the name of the entity that possesses the matching private key.
      In addition to binding a key with a name, a public-key certificate
      may bind those items with other restrictive or explanatory data


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      items. (See: X.509 public-key certificate.)

      4. (O) /SET/ "The process of ascertaining that a set of
      requirements or criteria has been fulfilled and attesting to that
      fact to others, usually with some written instrument. A system
      that has been inspected and evaluated as fully compliant with the
      SET protocol by duly authorized parties and process would be said
      to have been certified compliant." [SET2]

   $ certification authority (CA)
      1. (I) An entity that issues digital certificates (especially
      X.509 certificates) and vouches for the binding between the data
      items in a certificate.

      2. (O) "An authority trusted by one or more users to create and
      assign certificates. Optionally the certification authority may
      create


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      create the user's keys." [X509]

      Tutorial: Certificate users depend on the validity of information
      provided by a certificate. Thus, a CA should be someone that
      certificate users trust, and usually holds an official position
      created and granted power by a government, a corporation, or some
      other organization. A CA is responsible for managing the life
      cycle of certificates (see: certificate management) and, depending
      on the type of certificate and the CPS that applies, may be
      responsible for the life cycle of key pairs associated with the
      certificates (see: key management).

   $ certification authority workstation (CAW)
      (O)
      (N) A computer system that enables a CA to issue digital
      certificates and supports other certificate management functions
      as required.

   $ certification hierarchy
      1. (I) A tree-structured (loop-free) topology of relationships
      among CAs and the entities to whom the CAs issue public-key
      certificates. (See: hierarchical PKI, hierarchy management.)

      Tutorial: In this structure, one CA is the top CA, the highest
      level of the hierarchy. (See: root, top CA.) The top CA may issue
      public-key certificates to one or more additional CAs that form
      the second-highest level. Each of these CAs may issue certificates
      to more CAs at the third highest level, and so on. The CAs at the
      second-lowest level issue certificates only to non-CA entities
      that form the lowest level (see: end entity). Thus, all
      certification paths begin at the top CA and descend through zero
      or more levels of other CAs. All certificate users base path
      validations on the top CA's public key.

      2. (I) /PEM/ A certification hierarchy for PEM has three levels of
      CAs [R1422]:
      -  The highest level is the "Internet Policy Registration
         Authority".
      -  A CA at the second-highest level is a "policy certification
         authority".
      -  A CA at the third-highest level is a "certification authority".

      3. (O) /MISSI/ A certification hierarchy for MISSI has three or
      four levels of CAs:
      -  A CA at the highest level, the top CA, is a "policy approving


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         authority".
      -  A CA at the second-highest level is a "policy creation
         authority".
      -  A CA at the third-highest level is a local authority called a
         "certification authority".
      -  A CA at the fourth-highest (optional) level is a "subordinate
         certification authority".

      3. (O) /PEM/ A certification hierarchy for PEM has three levels of
      CAs [R1422]:
       - The highest level is the "Internet Policy Registration
         Authority".
       - A CA at the second-highest level is a "policy certification
         authority".
       - A CA at the third-highest level is a "certification authority".



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      4. (O) /SET/ A certification hierarchy for SET has three or four
      levels of CAs:
      -  The highest level is a "SET root CA".
      -  A CA at the second-highest level is a "brand certification
         authority".
      -  A CA at the third-highest (optional) level is a "geopolitical
         certification authority".
      -  A CA at the fourth-highest level is a "cardholder CA", a
         "merchant CA", or a "payment gateway CA".

   $ certification path
      1. (I) An ordered A linked sequence of one or more public-key certificates (or a
      sequence of certificates,
      or one or more public-key certificates followed by and one attribute
      certificate)
      certificate, that enables a certificate user to verify the
      signature on the last certificate in the path, and thus enables
      the user to obtain (from that last certificate) a certified public key (or
      key, or certified
      attributes) attributes, of the system entity that is the
      subject of that last certificate. (See: trust anchor, certificate
      validation, valid certificate.)

      2. (O) "An ordered sequence of certificates of objects in the
      [X.500 Directory Information Tree] which, together with the public
      key of the initial object in the path, can be processed to obtain
      that of the final object in the path." [R2527, [R3647, X509]

      Tutorial: The path is the "list of certificates needed to allow a
      particular user to obtain the public key of another." [X509] The list is "linked" in the sense that the digital
      signature of each certificate (except possibly the first) is
      verified by the public key contained in the preceding certificate;
      i.e., the private key used to sign a certificate and the public
      key contained in the preceding certificate form a key pair owned by that
      has previously been bound to the entity authority that signed.

      In

      The path is the X.509 quotation in "list of certificates needed to [enable] a
      particular user to obtain the previous paragraph, public key [or attributes] of
      another [user]." [X509] Here, the word "particular" points out
      that a certification path that can be validated by one certificate
      user might not be able to be


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      either the first certificate
      should needs to be a trusted certificate (it might be a root certificate)  or
      the signature on the first certificate should needs to be verified verifiable by a
      trusted key (it might be (e.g., a root key), but such trust is defined established only
      relative to each a "particular" (i.e., specific) user, not absolutely
      for all users.

   $ certification policy
      (D) Synonym for either "certificate policy" or "certification
      practice statement".

      Deprecated Term: ISDs SHOULD NOT use this term as a synonym for
      either of the terms given here. those terms; that would be duplicative and would mix
      concepts in a potentially misleading way. Instead, use either
      "certificate policy" or "certification practice statement",
      depending on what is meant.


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   $ certification practice statement (CPS)
      (I) "A statement of the practices which a certification authority
      employs in issuing certificates." [ABA96, R2527] R3647] (See: certificate
      policy.)

      Tutorial: A CPS is a published security policy that can help a
      certificate user to decide whether a certificate issued by a
      particular CA can be trusted enough to use in a particular
      application. A CPS may be (a) a declaration by a CA of the details
      of the system and practices it uses in its certificate management
      operations, (b) part of a contract between the CA and an entity to
      whom a certificate is issued, (c) a statute or regulation
      applicable to the CA, or (d) a combination of these types
      involving multiple documents. [ABA]

      A CPS is usually more detailed and procedurally oriented than a
      certificate policy. A CPS applies to a particular CA or CA
      community, while a certificate policy applies across CAs or
      communities. A CA with its single CPS may support multiple
      certificate policies, which may be used for different application
      purposes or by different user communities. On the other hand,
      multiple CAs, each with a different CPS, may support the same
      certificate policy. [R2527] [R3647]

   $ certification request
      (I) A algorithm-independent transaction format, defined by PCKS PKCS
      #10 and used in PKIX, that contains a DN, a public key, and
      optionally a set of attributes, collectively signed by the entity
      requesting certification, and sent to a CA, which transforms the
      request to an X.509 public-key certificate or another type of
      certificate.

   $ certify
      1. (I) Issue a digital certificate and thus vouch for the truth,
      accuracy, and binding between data items in the certificate (e.g.,
      see: X.509 public-key certificate), such as the identity of the
      certificate's subject and the ownership of a public key. (See:


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      certification.)

      Usage: To "certify a public key" means to issue a public-key
      certificate that vouches for the binding between the certificate's
      subject and the key.

      2. (I) The act by which a CA uses measures to verify the truth,
      accuracy, and binding between data items in a digital certificate.

      Tutorial: A description of the measures used for verification
      should be included in the CA's CPS.

   $ CFB
      (N) See: cipher feedback.


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   $ chain
      (D) See: trust chain.

   $ Challenge Handshake Authentication Protocol (CHAP)
      (I) A peer entity authentication method for PPP, using a randomly- randomly
      generated challenge and requiring a matching response that depends
      on a cryptographic hash of some combination of the challenge and a
      secret key. [R1994] (See: challenge-response, PAP.)

   $ challenge-response
      (I) An authentication process that verifies an identity by
      requiring correct authentication information to be provided in
      response to a challenge. In a computer system, the authentication
      information is usually a value that is required to be computed in
      response to an unpredictable challenge value, but it might be just
      password.

   $ Challenge-Response Authentication Mechanism (CRAM)
      (I) IMAP4 usage: /IMAP4/ A mechanism [R2195], intended for use with IMAP4
      AUTHENTICATE, by which an IMAP4 client uses a keyed hash [R2104]
      to authenticate itself to an IMAP4 server. (See: POP3 APOP.)

      Tutorial: The server includes a unique timestamp in its ready
      response to the client. The client replies with the client's name
      and the hash result of applying MD5 to a string formed from
      concatenating the timestamp with a shared secret that is known
      only to the client and the server.

   $ channel
      1. (I) An information transfer path within a system. (See: covert
      channel.)

      2. (I) A (O) "A subdivision of a the physical medium allowing possibly
      shared independent uses of the medium. [R3753] medium." (RFC 3753)

   $ channel capacity
      (I) The total capacity of a link to carry information; usually


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      expressed in bits per second. [R3753](Compare: (RFC 3753) (Compare: bandwidth.)

      Tutorial: Within a given bandwidth, the theoretical maximum
      channel capacity is given by Shannon~Os Shannon's Law. The actual channel
      capacity is determined by the bandwidth, the coding system used,
      and the signal-to-noise ratio.

   $ CHAP
      (I) See: Challenge Handshake Authentication Protocol.

   $ checksum
      (I) A value that (a) is computed by a function that is dependent
      on the contents of a data object and (b) is stored or transmitted
      together with the object, for the purpose of detecting changes in


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      the data. (See: cyclic redundancy check, data integrity service,
      error detection code, hash, keyed hash, parity bit, protected
      checksum.)

      Tutorial: To gain confidence that a data object has not been
      changed, an entity that later uses the data can compute a independently
      recompute the checksum value and compare it the result with the value
      that was stored or transmitted with the object.

      Computer systems and networks use checksums (and other mechanisms)
      to detect accidental changes in data. However, active wiretapping
      that changes data could also change an accompanying checksum to
      match the changed data. Thus, some checksum functions by
      themselves are not good countermeasures for active attacks. To
      protect against active attacks, the checksum function needs to be
      well-chosen (see: cryptographic hash), and the checksum result
      needs to be cryptographically protected (see: digital signature,
      keyed hash).

   $ Chinese wall policy
      (I) A security policy to prevent conflict of interest caused by an
      entity (e.g., a consultant) interacting with competing firms.
      (See: Brewer-Nash model.)

      Tutorial: All information is categorized into mutually exclusive
      conflict-of-interest classes I(1), I(2), ..., I(M), and each firm
      F(1), F(2), ..., F(N) belongs to exactly one class. The policy
      states that if a consultant has access to class I(i) information
      from a firm in that class, then the consultant may not access
      information from another firm in that same class, but may access
      information from another firm that is in a different class. Thus,
      the policy creates a barrier to communication between firms that
      are in the same conflict-of-interest class. Brewer and Nash
      modeled enforcement of this policy [BN89], including dealing with
      policy violations that could occur because two or more consultants
      work for the same firm.

   $ chosen-ciphertext attack
      (I) A cryptanalysis technique in which the analyst tries to


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      determine the key from knowledge of plain text that corresponds to
      cipher text selected (i.e., dictated) by the analyst.

   $ chosen-plaintext attack
      (I) A cryptanalysis technique in which the analyst tries to
      determine the key from knowledge of cipher text that corresponds
      to plain text selected (i.e., dictated) by the analyst.

   $ CIAC
      (O) See: Computer Incident Advisory Capability.

   $ CIK
      (I) See: cryptographic ignition key.


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   $ cipher
      (I) A cryptographic algorithm for encryption and decryption.

   $ cipher block chaining (CBC)
      (N) A block cipher mode that enhances ECB mode by chaining
      together blocks of cipher text it produces. [FP081] (See: [R1829],
      [R2405], [R2451].)

      Tutorial: This mode operates by combining (exclusive OR-ing) the
      algorithm's ciphertext output block with the next plaintext block
      to form the next input block for the algorithm.

   $ cipher feedback (CFB)
      (N) A block cipher mode that enhances ECB mode by chaining
      together the blocks of cipher text it produces and operating on
      plaintext segments of variable length less than or equal to the
      block length. [FP081]

      Tutorial: This mode operates by using the previously generated
      ciphertext segment as the algorithm's input (i.e., by "feeding
      back" the cipher text) to generate an output block, and then
      combining (exclusive OR-ing) that output block with the next
      plaintext segment (block length or less) to form the next
      ciphertext segment.

   $ cipher text
      1. (I) /noun/ Data that has been transformed by encryption so that
      its semantic information content (i.e., its meaning) is no longer
      intelligible or directly available. (See: ciphertext. Compare:
      clear text, plain text.)

      2. (O) "Data produced through the use of encipherment. The
      semantic content of the resulting data is not available." [I7498
      Part 2]

   $ ciphertext
      1a.
      1. (I) /adjective/ Referring to cipher text. (See: cipher text.)



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      1b. text,
      Compare: cleartext, plaintext.)

      2. (D) /noun/ A synonym for cipher text. (See: cleartext,
      plaintext.)

      Deprecated Usage: To avoid ambiguity, ISDs should not use this term as a synonym for
      cipher text. ISDs SHOULD differentiate distinguish between the adjective
      "ciphertext" and the noun phrase "cipher text" and the adjective
      "ciphertext". text".

   $ ciphertext auto-key (CTAK)
      (D) "Cryptographic logic that uses previous cipher text to
      generate a key stream." [C4009, A1523] (See: KAK.)

      Deprecated Term: IDS should not SHOULD NOT use this term; it is neither well-
      known nor precisely defined. Instead, use terms associated with


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      modes that are defined in standards, such as CBC, CFB, and OFB.

   $ ciphertext-only attack
      (I) A cryptanalysis technique in which the analyst tries to
      determine the key solely from knowledge of intercepted cipher text
      (although the analyst may also know other clues, such as the
      cryptographic algorithm, the language in which the plain text was
      written, the subject matter of the plain text, and some probable
      plaintext words.)

   $ ciphony
      (O) The process of encrypting audio information.

   $ CIPSO
      (I) See: Common IP Security Option.

   $ CKL
      (I) See: compromised key list.

   $ Clark-Wilson model
      (N) A security model [Clark] to maintain data integrity in the
      commercial world. (Compare: Bell-LaPadula model.)

   $ class 2, 3, 4, 5
      (O) /U.S. DoD/ Assurance levels for PKIs, and for X.509 public-key
      certificates issued by a PKI. [DoD3] (See: (first law under)
      Courtney's laws.) "first law" under
      "Courtney's laws".)
      -  "Class 2": Intended for applications handling unclassified,
         low-value data in minimally or moderately protected
         environments.
      -  "Class 3": Intended for applications handling unclassified,
         medium-value data in moderately protected environments, or
         handling unclassified or high-value data in highly protected
         environments, and for discretionary access control of
         classified data in highly protected environments.
      -  "Class 4": Intended for applications handling unclassified,
         high-value data in minimally protected environments.
      -  "Class 5": Intended for applications handling classified data
         in minimally protected environments, and for authentication of


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         material that would affect the security of classified systems.

      The environments are defined as follows:
      -  "Highly protected environment": Networks that are protected
         either with encryption devices approved by NSA for protection
         of classified data or via physical isolation, and that are
         certified for processing system-high classified data, where
         exposure of unencrypted data is limited to U.S. citizens
         holding appropriate security clearances.
      -  "Moderately protected environment":
         -- Physically isolated unclassified, unencrypted networks in
            which access is restricted based on legitimate need.
         -- Networks protected by NSA-approved, type 1 encryption,


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            accessible by U.S.-authorized foreign nationals.
      -  "Minimally protected environments": Unencrypted networks
         connected to either the Internet or NIPRNET, either directly or
         via a firewall.

   $ Class D A1, B3, B2, B1, C2, or C1 computer system
      (O) /TCSEC/ See: TCSEC. Tutorial under "Trusted Computer System
      Evaluation Criteria".

   $ classification
      1. (I) A grouping of classified information to which a
      hierarchical, restrictive security label is applied to increase
      protection of the data from unauthorized disclosure. (See:
      aggregation, classified, data confidentiality service. Compare:
      compartment.)

      2. (I) An authorized process by which information is determined to
      be classified and assigned to a security level. (See:
      declassification.)

      Usage: Usually understood to involve data confidentiality, but
      ISDs SHOULD make this clear when data also is sensitive in other
      ways and SHOULD use other terms for those other sensitivity
      concepts. (See: sensitive information, data integrity.)

   $ classification label
      (I) A security label that tells the degree of harm that will
      result from unauthorized disclosure of the labeled data, and may
      also tell what countermeasures are required to be applied to
      protect the data from unauthorized disclosure. Example: IPSO.
      (See: classified, data confidentiality service. Compare: integrity
      label.)

      Usage: Usually understood to involve data confidentiality, but
      ISDs SHOULD make this clear when data also is sensitive in other
      ways and SHOULD use other terms for those other sensitivity
      concepts. (See: sensitive information, data integrity.)

   $ classification level
      (I) A hierarchical level of protection (against unauthorized
      disclosure) that is required to be applied to certain classified
      data. (See: classified. Compare: security level.)

      Usage: Usually understood to involve data confidentiality, but
      ISDs SHOULD make this clear when data also is sensitive in other


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      ways and SHOULD use other terms for those other sensitivity
      concepts. (See: sensitive information, data integrity.)

   $ classified
      1. (I) Refers to information (stored or conveyed, in any form)
      that is formally required by a security policy to receive data
      confidentiality service and to be marked with a security label


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      (which in some cases might be implicit) to indicate its protected
      status. (See: classification, classification classify, security level. Compare: unclassified.)

      Usage: Usually understood to involve data confidentiality, but
      ISDs SHOULD make this clear when data also is sensitive in other
      ways and SHOULD use other terms for those other sensitivity
      concepts. (See: sensitive information, data integrity.)

      Tutorial: The term is mainly used in government, especially in the
      military, but the underlying concept also applies outside
      government.

      2. (O) /U.S. DoD/ Information that has been determined pursuant to
      Executive Order 12958 ("Classified National Security Information",
      20 April 1995) or any predecessor order to require protection
      against unauthorized disclosure and is marked to indicate its
      classified status when in documentary form.

   $ classify
      (I) To officially designate an information item or type of
      information as being classified and assigned to a specific
      security level. (See: classified, declassify, security level.)

   $ clean system
      (I) A computer system in which the operating system and
      application system software and files have been freshly installed
      from trusted software distribution media. (Compare: secure state.)

   $ clear
      (D) /verb/ Synonym for "erase". [C4009]

      Deprecated Definition: ISDs SHOULD NOT use the term with this
      definition; it could be confused with "clear text" in which
      information is directly recoverable.

   $ clear text
      1. (I) /noun/ Data in which the semantic information content
      (i.e., the meaning) is intelligible or is directly available,
      i.e., not encrypted. (Compare: cipher text, plain text. See: (See: cleartext, in the clear.) clear. Compare:
      cipher text, plain text.)

      2. (O) "Intelligible data, the semantic content of which is
      available." [I7498 Part 2]

      3. (D) Synonym for "plain text".

      Deprecated Definition: ISDs SHOULD NOT use this term as a synonym
      for "plain text", because the plain text that is input to an
      encryption process may itself be cipher text that was output from
      an encryption. (See: superencryption.)




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   $ clearance
      See: security clearance.

   $ clearance level
      (I) The security level of information to which a security
      clearance authorizes a person to have access.

   $ cleartext
      1a.
      1. (I) /adjective/ Referring to clear text. (Compare: (See: clear text.
      Compare: ciphertext,
      plaintext. See: plaintext.)

      2. (D) /noun/ A synonym for clear text.) text.

      Deprecated Usage: To avoid ambiguity, ISDs should not use this term as a synonym for
      clear text. ISDs SHOULD distinguish between the adjective
      "cleartext" and the noun phrase "clear text".

   $ CLEF
      (N) See: commercially licensed evaluation facility.

   $ client
      (I) A system entity that requests and uses a service provided by
      another system entity, called a "server". (See: server.)

      Tutorial: Usually, the requesting entity it is a computer process, understood that the client and it server are
      automated components of the system, and the client makes the
      request on behalf of a human user. In some cases, the server may
      itself be a client of some other server.

   $ client-server system
      (I) A distributed system in which one or more entities, called
      clients, request a specific service from one or more other
      entities, called servers, that provide the service to the clients.

      Example: The Word Wide Web, in which component servers provided provide
      information that is requested by component clients called browsers.
      "browsers".

   $ CLIPPER
      (N) An integrated microcircuit (in MYK-7x series manufactured by
      Mykotronx, Inc.) that implements SKIPJACK, has non-deterministic
      random number generator, and supports key escrow. (See: Escrowed
      Encryption Standard. Compare: CLIPPER.)

      Tutorial: The chip was mainly intended for protecting
      telecommunications over the public switched network. The key
      escrow scheme for the chip involves a SKIPJACK key that is common
      to all chips and that protects the unique serial number of the
      chip, and a second SKIPJACK key unique to the chip that protects
      all data encrypted by the chip. The second key is escrowed as
      split key components held by NIST and the U.S. Treasury
      Department.


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   $ closed security environment
      (O) /U.S. DoD/ A system environment that meets both of the


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      following conditions: (a) Application developers (including
      maintainers) have sufficient clearances and authorizations to
      provide an acceptable presumption that they have not introduced
      malicious logic. (b) Configuration control provides sufficient
      assurance that system applications and the equipment they run on
      are protected against the introduction of malicious logic prior to
      and during the operation of applications. [NCS04] (See: (first law
      under) Courtney's laws. "first
      law" under "Courtney's laws". Compare: open security environment.)

   $ CMA
      (D) See: certificate management authority.

   $ CMCS
      (O) See: COMSEC Material Control System.

   $ CMM
      (N) See: Capability Maturity Model.

   $ CMS
      (I) See: Cryptographic Message Syntax.

   $ code
      1. (I) A system of symbols used to represent information, which
      might originally have some other representation. Examples: ASCII,
      BER, country code, Morse code. (See: encode, object code, source
      code.)

      Deprecated usage: Abbreviation: To avoid confusion with definition 1,
      ISDs SHOULD NOT use "code" as an abbreviation for of "country code",
      "cyclic redundancy code", "Data Authentication Code", "error
      detection code", or "Message Authentication Code". To avoid
      misunderstanding, use the fully qualified term in these other
      cases, at least at the point of first usage.

      2. (I) /cryptography / /cryptography/ An encryption algorithm based on
      substitution; i.e., a system for providing data confidentiality by
      using arbitrary groups (called "code groups") of letters, numbers,
      or symbols to represent units of plain text of varying length.
      (See: codebook, cryptography.)

      Deprecated Usage: To avoid confusion with definition 1, ISDs
      SHOULD NOT use "code" as synonym for any of the following terms:
      (a) "cipher", "hash", or other words that mean "a cryptographic
      algorithm"; (b) "cipher text"; or (c) "encrypt", "hash", or other
      words that refer to applying a cryptographic algorithm.

      3. (I) An algorithm based on substitution, but used to shorten
      messages rather than to conceal their content.



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      4. (I) /computer programming/ To write computer software. (See:
      object code, source code.)



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      Deprecated Usage: Abbreviation: To avoid confusion with definition 1,
      ISDs SHOULD NOT use "code" as an abbreviation for of "object code" or
      "source code". To avoid misunderstanding, use the fully qualified
      term in these other cases, at least at the point of first usage.

   $ code book
      1. (I) Document containing a systematically arranged list of
      plaintext units and their ciphertext equivalents. [C4009]

      2. (I) An encryption algorithm that uses a word substitution
      technique. [C4009] (See: code, ECB.)

   $ code signing
      (I) A security mechanism that uses a digital signature to provide
      data origin authentication for software that is being distributed
      for use. (See: mobile code, trusted distribution.)

   $ COI
      (I) See: community of interest.

   $ cold start
      (N) /cryptographic module/ A procedure for initially keying
      cryptographic equipment. [C4009]

   $ color change
      (I) In a system being operated in periods processing mode, the act
      of purging all information from one processing period and then
      changing over to the next processing period. (See: BLACK, RED.)

   $ Commercial COMSEC Endorsement Program (CCEP)
      (N)
      (O) "Relationship between NSA and industry in which NSA provides
      the COMSEC expertise (i.e., standards, algorithms, evaluations,
      and guidance) and industry provides design, development, and
      production capabilities to produce a type 1 or type 2 product."
      [C4009]

   $ commercially licensed evaluation facility (CLEF)
      (N) An organization that has official approval to evaluate the
      security of products and systems in accordance with the Common
      Criteria, ITSEC, or some other standard.

   $ Committee on National Security Systems (CNSS)
      (O) A U.S. Government, interagency, standing committee of the
      President's Critical Infrastructure Protection Board. The CNSS is
      chaired by the Secretary of Defense and provides a forum for the
      discussion of policy issues, sets national policy, and promulgates
      direction, operational procedures, and guidance for the security
      of national security systems. The Secretary of Defense and the
      Director of Central Intelligence are responsible for developing


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      and overseeing the implementation of Government-wide policies,
      principles, standards, and guidelines for the security of systems
      that handle national security information.

   $ Common Criteria for Information Technology Security
      (N) A standard for evaluating information technology (IT) products
      and systems. It states requirements for security functions and for
      assurance measures. [CCIB] (See: CLEF, EAL, packages, protection
      profile, security target, TOE. Compare: CMM.)

      Tutorial: Canada, France, Germany, the Netherlands, the United
      Kingdom, and the United States (NIST and NSA) began developing
      this standard in 1993, based on the European ITSEC, the Canadian
      Trusted Computer Product Evaluation Criteria (CTCPEC), and the
      U.S. "Federal Criteria for Information Technology Security" and


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      its precursor, the TCSEC. Work was done in cooperation with
      ISO/IEC Joint Technical Committee 1 (Information Technology),
      Subcommittee 27 (Security Techniques), Working Group 3 (Security
      Criteria). Version 2.0 of the Criteria has been issued as ISO's
      International Standard 15408. The U.S. Government intends this
      standard to supersede both the TCSEC and FIPS PUB 140-1. (See:
      NIAP.)

      The standard addresses data confidentiality, data integrity, and
      availability and may apply to other aspects of security. It
      focuses on threats to information arising from human activities,
      malicious or otherwise, but may apply to non-human threats. It
      applies to security measures implemented in hardware, firmware, or
      software. It does not apply to (a) administrative security not
      related directly to technical security, (b) technical physical
      aspects of security such as electromagnetic emanation control, (c)
      evaluation methodology or administrative and legal framework under
      which the criteria may be applied, (d) procedures for use of
      evaluation results, or (e) assessment of inherent qualities of
      cryptographic algorithms.

      Part 1, Introduction and General Model, defines general concepts
      and principles of IT security evaluation; presents a general model
      of evaluation; and defines constructs for expressing IT security
      objectives, for selecting and defining IT security requirements,
      and for writing high-level specifications for products and
      systems.

      Part 2, Security Functional Requirements, contains a catalog of
      well-defined and understood security well-understood functional requirements requirement statements
      that are intended to be used as a standard way of expressing the
      security requirements for IT products and systems.

      Part 3, Security Assurance Requirements, contains a catalog of
      assurance components for use as a standard way of expressing the
      such requirements for IT products and systems, and defines
      evaluation criteria for protection profiles and security targets.


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   $ Common IP Security Option (CIPSO)
      (I) See: (secondary secondary definition under) IPSO. under "IPSO".

   $ common name
      (N) A character string that (a) may be a part of the X.500 DN of a
      Directory object ("commonName" attribute), (b) is a (possibly
      ambiguous) name by which the object is commonly known in some
      limited scope (such as an organization), and (c) conforms to the
      naming conventions of the country or culture with which it is
      associated. [X520] (See: ("subject" "subject" and "issuer" under) X.509 under "X.509
      public-key certificate.) certificate".)

      Examples: "Dr. Albert Einstein", "The United Nations", and "12-th
      Floor Laser Printer".


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   $ communications cover
      (N) "Concealing or altering of characteristic communications
      patterns to hide information that could be of value to an
      adversary." [C4009] (See: operations security, traffic-flow
      confidentiality, TRANSEC.)

   $ communication security (COMSEC)
      (I) Measures that implement and assure security services in a
      communication system, particularly those that provide data
      confidentiality and data integrity and that authenticate
      communicating entities.

      Usage: COMSEC is usually understood to include (a) cryptography
      and its related algorithms and key management methods and
      processes, devices that implement those algorithms and processes,
      and the life cycle management of the devices and keying material.
      Also, COMSEC is sometimes more broadly understood as further
      including (b) traffic-flow confidentiality, (c) TRANSEC, and (d)
      steganography [Kahn]. (See: cryptology, signal security.)

   $ community of interest (COI)
      1. (I) A set of entities that operate under a common security
      policy. (Compare: domain.)

      2. (O) /U.S. DoD/ "A collaborative group of users who exchange
      information in support of shared missions, business processes, and
      objectives."

   $ community risk
      (O)
      (N) Probability that a particular vulnerability will be exploited
      within an interacting population and adversely affect some members
      of that population. [C4009] (See: Morris worm.)

   $ community string
      (I) A community name in the form of an octet string that serves as
      a cleartext password in SNMP version 1. [R1157] (RFC 1157)


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   $ compartment
      1. (I) A grouping of sensitive information items that require
      special access controls beyond those normally provided for the
      basic classification level of the information. (See: category.) compartmented
      security mode. Compare: category, classification.)

      Usage: The term is usually understood to include the special
      handling procedures to be used for the information.

   $ Compartments field

      2. (I) A 16-bit field (the "C field") that specifies compartment
      values in the Synonym for "category".

      Deprecated Usage: This Glossary defines "category" with a slightly
      narrower meaning than "compartment". That is, a security option (option type 130) of version 4 IP's
      datagram header format. The valid field values are label is
      assigned by to a category because the
      U.S. Government, data owner needs to handle the
      data as specified compartment. However, a compartment could receive special
      protection in RFC 791.



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      Deprecated Definition: ISDs SHOULD NOT use the abbreviation "C
      field"; the abbreviation is potentially ambiguous. Instead, use
      "Compartments field".

   $ component
      See: a system component. without being assigned a category label.

   $ compression
      (I) compartmented security mode
      (N) A process that encodes information in a way that minimizes the
      number mode of resulting code symbols and thus reduces system operation wherein all users having access to
      the system have the necessary security clearance for the single,
      hierarchical classification level of all data handled by the
      system, but some users do not have the clearance for a non-
      hierarchical category of some data handled by the system. (See:
      category, /system operation/ under "mode", protection level,
      security clearance.)

      Usage: Usually abbreviated as "compartmented mode". This term was
      defined in U.S. Government policy on system accreditation. In this
      mode a system may hand (a) a single hierarchical classification
      level and (b) multiple non-hierarchical categories within that
      level.

   $ Compartments field
      (I) A 16-bit field (the "C field") that specifies compartment
      values in the security option (option type 130) of version 4 IP's
      datagram header format. The valid field values are assigned by the
      U.S. Government, as specified in RFC 791.

      Deprecated Abbreviation: ISDs SHOULD NOT use the abbreviation "C
      field"; the abbreviation is potentially ambiguous. Instead, use
      "Compartments field".

   $ component
      See: system component.

   $ compression
      (I) A process that encodes information in a way that minimizes the
      number of resulting code symbols and thus reduces storage space or
      transmission time.

      Tutorial: A data compression algorithm may be "lossless", i.e.,


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      retain all information that was encoded in the data, so that
      decompression can recover all the information; or an algorithm may
      be "lossy". Text usually needs to be compressed losslessly, but
      images are often compressed with lossy schemes.

      Not all schemes that encode information losslessly for machine
      processing are efficient in terms of minimizing the number of
      output bits. For example, ASCII encoding is lossless, but ASCII
      data can often be losslessly reencoded in fewer bits with other
      schemes. These more efficient schemes take advantage of some sort
      of inherent imbalance, redundancy, or repetition in the data, such
      as by replacing a character string in which all characters are the
      same by a shorter string consisting of only the single character
      and a character count.

      Lossless compression schemes cannot effectively reduce the number
      of bits in cipher text produced by a strong encryption algorithm,
      because the cipher text is essentially a pseudorandom bit string
      that does not contain patterns susceptible to reencoding.
      Therefore, protocols that offer both encryption and compression
      services (e.g., SSL) need to perform the compression operation
      before the encryption operation.

   $ compromise
      See: data compromise, security compromise.

   $ compromise recovery
      (I) The process of regaining a secure state for a system after
      detecting that the system has experienced a security compromise.

   $ compromised key list (CKL)
      (O)
      (N) /MISSI/ A list that identifies keys for which unauthorized
      disclosure or alteration may have occurred. (See: compromise.)

      Tutorial: A CKL is issued by an CA, like a CRL is issued. But a
      CKL lists only KMIDs, not subjects that hold the keys, and not
      certificates in which the keys are bound.




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   $ COMPUSEC
      (I) See: computer security.

   $ computer system
      (I) A synonym for "information system", or a component thereof.
      (Compare: computer platform.)

   $ computer emergency response team (CERT)
      (I) An organization that studies computer and network INFOSEC in
      order to provide incident response services to victims of attacks,
      publish alerts concerning vulnerabilities and threats, and offer
      other information to help improve computer and network security.
      (See: CSIRT, security incident.)



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      Examples: CERT Coordination Center at Carnegie-Mellon University
      (sometimes called "the" CERT); CIAC.

   $ Computer Incident Advisory Capability (CIAC)
      (O) The centralized CSIRT of the U.S Department of Energy; a
      member of FIRST.

   $ computer network
      (I) A collection of host computers together with the subnetwork or
      internetwork through which they can exchange data.

      Usage: This definition is intended to cover systems of all sizes
      and types, ranging from the complex Internet to a simple system
      composed of a personal computer dialing in as a remote terminal of
      another computer.

   $ computer platform
      (I) A combination of computer hardware and an operating system
      (which may consist of software, firmware, or both) for that
      hardware. (Compare: computer system.)

   $ computer security (COMPUSEC)
      (I) Measures to implement and assure security services in a
      computer system, particularly those that assure access control
      service.

      Usage: Usually refers to internal controls (functions, features,
      and technical characteristics) that are implemented in software
      (especially in operating systems); sometimes refers to internal
      controls implemented in hardware; rarely used to refer to external
      controls.

      (O) "The protection afforded to an automated information system in
      order to attain the applicable objectives of preserving the
      integrity, availability and confidentiality of information system
      resources (includes hardware, software, firmware,
      information/data, and telecommunications)." [SP12]

   $ computer security incident response team (CSIRT)
      (I) An organization "that coordinates and supports the response to
      security incidents that involve sites within a defined
      constituency." [R2350] (See: CERT, FIRST, security incident.)


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      Tutorial: To be considered a CSIRT, an organization must do as
      follows: (a) Provide a (secure) channel for receiving reports
      about suspected security incidents. (b) Provide assistance to
      members of its constituency in handling the incidents. (c)
      Disseminate incident-related information to its constituency and
      other involved parties.

   $ computer security object
      (I) The definition or representation of a resource, tool, or


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      mechanism used to maintain a condition of security in computerized
      environments. Includes many items referred to in standards that
      are either selected or defined by separate user communities.
      [CSOR] (See: object identifier, Computer Security Objects
      Register.)

   $ Computer Security Objects Register (CSOR)
      (N) A service operated by NIST is establishing a catalog for
      computer security objects to provide stable object definitions
      identified by unique names. The use of this register will enable
      the unambiguous specification of security parameters and
      algorithms to be used in secure data exchanges. (See: object
      identifier.)

      Tutorial: The CSOR follows registration guidelines established by
      the international standards community and ANSI. Those guidelines
      establish minimum responsibilities for registration authorities
      and assign the top branches of an international registration
      hierarchy. Under that international registration hierarchy the
      CSOR is responsible for the allocation of unique identifiers under
      the branch: {joint-iso-ccitt(2) country(16) us(840)
      organization(1) gov(101) csor(3)}.

   $ Computers At Risk
      (O) The 1991 report [NRC91] of the System Security Study
      Committee, sponsored by the U.S. National Academy of Sciences and
      supported by the Defense Advanced Research Projects Agency of the
      U.S. DoD. It made many recommendations for industry and Government
      to improve computer security and trustworthiness. Some of the most
      important recommendations (e.g., establishing an Information
      Security Foundation chartered by the U.S. Government) have not
      been implemented at all, and others (e.g., codifying Generally
      Accepted System Security Principles similar to accounting
      principles) have been implemented but not widely adopted [SP14,
      SP27].

   $ COMSEC
      (I) See: communication security.

   $ COMSEC account
      (N)
      (O) /U.S. Government/ "Administrative entity, identified by an
      account number, used to maintain accountability, custody, and


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      control of COMSEC material." [C4009] (See: COMSEC custodian.)

   $ COMSEC accounting
      (I) /U.S. Government/ The process of creating, collecting, and
      maintaining data records that describe the status and custody of
      designated items of COMSEC material. (See: accounting legend
      code.)

      Tutorial: Almost any secure information system needs to record a
      security audit trail, but a system that manages COMSEC material


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      needs to record additional data about the status and custody of
      COMSEC items.
      -  COMSEC tracking: The process of automatically collecting,
         recording, and managing information that describes the status
         of designated items of COMSEC material at all times during each
         product~Os
         product's lifecycle.
      -  COMSEC controlling: The process of supplementing tracking data
         with custody data, which consists of explicit acknowledgements
         of system entities that they (a) have received specific COMSEC
         items and (b) are responsible for preventing exposure of those
         items.

      For example, a key management system that serves a large customer
      base needs to record tracking data for the same reasons that a
      national parcel delivery system does, i.e., to answer the question
      "Where is that thing now?". If keys are encrypted immediately upon
      generation and handled only in BLACK form between the point of
      generation and the point of use, then tracking may be all that is
      needed. However, in cases where keys are handled at least partly
      in RED form and are potentially subject to exposure, then tracking
      needs to be supplemented by controlling.

      Data that is used purely for tracking need be retained only
      temporarily, until an item's status changes. Data that is used for
      controlling is retained indefinitely to ensure accountability and
      support compromise recovery.

   $ COMSEC boundary
      (N) "Definable perimeter encompassing all hardware, firmware, and
      software components performing critical COMSEC functions, such as
      key generation and key handling and storage." [C4009] [Compare:
      cryptographic boundary.]

   $ COMSEC custodian
      (N)
      (O) /U.S. Government/ "Individual designated by proper authority
      to be responsible for the receipt, transfer, accounting,
      safeguarding, and destruction of COMSEC material assigned to a
      COMSEC account." [C4009]

   $ COMSEC material
      (N) /U.S. Government/ "Item designed to secure or authenticate
      communications. [It] includes but is not limited to key,


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      equipment, devices, documents, firmware, or software that embodies
      or describes cryptographic logic and other items that perform
      COMSEC functions." [C4009] (Compare: keying material.)

   $ COMSEC Material Control System (CMCS)
      (O) /U.S. Government/ "Logistics and accounting system through
      which COMSEC material marked 'CRYPTO' is distributed, controlled,
      and safeguarded." [C4009] (See: COMSEC account, COMSEC custodian.)




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   $ confidentiality
      See: data confidentiality.

   $ configuration control
      (I) The process of regulating changes to hardware, firmware,
      software, and documentation throughout the development and
      operational life of a system. (See: administrative security,
      harden, trusted distribution.)

      Tutorial: Configuration control helps protect against unauthorized
      or malicious alteration of a system and thus provides assurance of
      system integrity. (See: malicious logic.)

   $ confinement property
      (N) /formal model/ Property of a system whereby a subject has
      write access to an object only if the classification of the object
      dominates the clearance of the subject. (See: *-property, Bell-
      LaPadula model.)

   $ connectionless data integrity service
      (I) A security service that provides data integrity service Synonym for an
      individual IP datagram, by detecting modification of the datagram,
      without regard to the ordering of the datagram in a stream of
      datagrams.

      Tutorial: In contrast, a connection-oriented data "datagram integrity
      service usually would be able to detect lost or reordered
      datagrams within a stream of datagrams. service".

   $ constraint
      (I) /access control/ A limitation on the function of an identity,
      role, or privilege. (See: rule-based access control.)

      Tutorial: In effect, a constraint is a form of security policy and
      may be either static or dynamic:
      -  "Static constraint": A constraint that must be satisfied at the
         time the policy is defined, and then continues to be satisfied
         until the constraint is removed.
      -  "Dynamic constraint": A constraint that may be defined to apply
         at various times that the identity, role, or other object of
         the constraint is active in the system.




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   $ content filter
      (I) /World Wide Web/ Application software used to prevent access
      to certain Web servers, such as by parents who do not want their
      children to access pornography. (See: filter, guard.)

      Tutorial: The filter is usually browser-based, but could be part
      of an intermediate cache server. The two basic content filtering
      techniques are (a) to block a specified list of URLs and (b) to
      block material that contains specified words and phrases.

   $ contingency plan
      (I) A plan for emergency response, backup operations, and post-
      disaster recovery in a system as part of a security program to
      ensure availability of critical system resources and facilitate
      continuity of operations in a crisis. [NCS04] (See: availability.)




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   $ controlled access protection
      (N)
      (O) /TCSEC/ The C2 level of evaluation criteria described in the TCSEC. for a C2 computer
      system.

      Tutorial: The major features of the C2 level are individual
      accountability, audit, access control, and object reuse.

   $ controlled cryptographic item (CCI)
      (O) /U.S. Government/ "Secure telecommunications or information
      handling equipment, or associated cryptographic component, that is
      unclassified but governed by a special set of control
      requirements." [C4009] (Compare: EUCI.)

      Tutorial: This category of equipment was established in 1985 to
      promote broad use of secure equipment for protecting both
      classified and unclassified information in the national interest.
      CCI equipment uses a classified cryptographic logic, but the
      hardware or firmware embodiment of that logic is unclassified.
      Drawings, software implementations, and other descriptions of that
      logic remain classified. [N4001]

   $ controlled interface
      (I) A mechanism that facilitates the adjudication of the different
      security policies of interconnected systems. (See: domain, guard.)

   $ controlled security mode
      (D) /U.S. DoD/ A mode of system operation wherein (a) two or more security
      levels of an information system,
      wherein at least are allowed to be handled concurrently
      within the same system when some users with having access to the system
      have neither a security clearance nor need to know need-to-know for all classified material
      contained in some of the system. However,
      data handled by the system, but (b) separation and control of the users and
      the classified material on the basis, respectively, of clearance
      and classification level are not essentially under dependent only on operating
      system control like (like they are in multilevel security mode. [DoD2] mode). (See:
      /system operation/ under "mode", protection level.)

      Deprecated Term: ISDs SHOULD NOT use this term. It was defined in
      a version of U.S. DoD Government policy on regarding system accreditation but was
      subsumed by "partitioned security mode" in a later version.


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      Tutorial: Controlled mode was intended to encourage ingenuity in
      meeting the security data confidentiality requirements of Defense policy in ways less restrictive
      than "dedicated security mode" and "system high "system-high security mode",
      but at a level of risk lower than that generally associated with
      the true "multilevel security mode". This was intended to be
      accomplished by implementation of explicit augmenting measures to
      reduce or remove a substantial measure of system software
      vulnerability together with specific limitation of the security
      clearance levels of users permitted having concurrent access to the system.

   $ controlling authority
      (O) /U.S. Government/ "Official responsible for directing the
      operation of a cryptonet and for managing the operational use


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      operation of a cryptonet and for managing the operational use and
      control of keying material assigned to the cryptonet." [C4009,
      N4006]

   $ cookie
      1. (I) /HTTP/ Data exchanged between an HTTP server and a browser
      (a client of the server) to store state information on the client
      side and retrieve it later for server use.

      Tutorial: An HTTP server, when sending data to a client, may send
      along a cookie, which the client retains after the HTTP connection
      closes. A server can use this mechanism to maintain persistent
      client-side state information for HTTP-based applications,
      retrieving the state information in later connections. A cookie
      may include a description of the range of URLs for which the state
      is valid. Future requests made by the client in that range will
      also send the current value of the cookie to the server. Cookies
      can be used to generate profiles of web usage habits, and thus may
      infringe on personal privacy.

      2. (I) /IPsec/ Data objects exchanged by ISAKMP to prevent certain
      denial-of-service attacks during the establishment of a security
      association.

      3. (D) /access control/ Synonym for "capability" "capability token" or "ticket.

      Deprecated Definition: ISDs SHOULD NOT use this term with this
      definition; that would duplicate the meaning of better-established
      terms and mix concepts in a potentially misleading way.

   $ Coordinated Universal Time (UTC)
      (N) UTC is derived from International Atomic Time (TAI) by adding
      a number of leap seconds. The International Bureau of Weights and
      Measures computes TAI once each month by averaging data from many
      laboratories. (See: GeneralizedTime, UTCTime.)

   $ copy
      See: card copy.


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      $ correction
      (I) See: secondary definition under "security".

   $ correctness
      (I) "The property of a system that is guaranteed as the result of
      formal verification activities." [Huff] (See: correctness proof,
      verification.)

   $ correctness integrity
      (I) Accuracy The property that the information represented by data is
      accurate and consistency consistent. (Compare: data integrity, source
      integrity.)



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      Tutorial: IDS SHOULD NOT use this term without providing a
      definition; the term is neither well-known nor precisely defined.
      Data integrity refers to the constancy of data values, and source
      integrity refers to confidence in data values. However,
      correctness integrity refers to confidence in the underlying
      information that data values represent, rather than of the data itself. Closely and this property is
      closely related to issues of accountability and error handling. (See: data integrity,
      source integrity.)

   $ correctness proof
      (I) A mathematical proof of consistency between a specification
      for system security and the implementation of that specification.
      (See: correctness, formal specification.)

   $ corruption
      (I) A type of threat action that undesirably alters system
      operation by adversely modifying system functions or data. (See:
      disruption.)

      Usage: This type includes the following subtypes:
      -  "Tampering": In context of corruption, deliberately altering a
         system's logic, data, or control information to interrupt or
         prevent correct operation of system functions. (See: (main misuse,
         main entry for) tampering.) for "tampering".)
      -  "Malicious logic": In context of corruption, any hardware,
         firmware, or software (e.g., a computer virus) intentionally
         introduced into a system to modify system functions or data.
         (See: (main incapacitation, main entry for) malicious logic.) for "malicious logic",
         masquerade, misuse.)
      -  "Human error": In context of corruption, human action or
         inaction that unintentionally results in the alteration of
         system functions or data.
      -  "Hardware or software error": In context of corruption, error
         that results in the alteration of system functions or data.
      -  "Natural disaster": In context of corruption, any "act of God"
         (e.g., power surge caused by lightning) that alters system
         functions or data. [FP031 section 2]

   $ counter-countermeasure
      (I) An action, device, procedure, or technique used by an attacker
      to offset a defensive countermeasure.

      Tutorial: For every countermeasure devised to protect computers
      and networks, some cracker probably will be able to devise a
      counter-countermeasure. Thus, systems must use "defense in depth".

   $ countermeasure
      (I) An action, device, procedure, or technique that reduces a
      threat, a vulnerability, or an attack by eliminating or preventing
      it, by minimizing the harm it can cause, or by discovering and


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      reporting it so that corrective action can be taken.

      Tutorial: In an Internet protocol, a countermeasure may take the


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      form of a protocol feature, an component function, or a usage
      constraint.

   $ country code
      (I) An identifier that is defined for a nation by ISO. [I3166]

      Tutorial: For each nation, ISO Standard 3166 defines a unique two-
      character alphabetic code, a unique three-character alphabetic
      code, and a three-digit code. Among many uses of these codes, the
      two-character codes are used as top-level domain names.

   $ Courtney's laws
      Tutorial: The following principles
      (N) Principles for managing system security that were stated by
      Robert H. Courtney, Jr.: Jr.

      Tutorial: Bill Murray codified Courtney's laws as follows: [Murr]
      -  Courtney's first law: You cannot say anything interesting
         (i.e., significant) about the security of a system except in
         the context of a particular application and environment.
      -  Courtney's second law: Never spend more money eliminating a
         security exposure than tolerating it will cost you. (See:
         acceptable risk, risk analysis.)
         -- First corollary: Perfect security has infinite cost.
         -- Second corollary: There is no such thing as zero risk.
      -  Courtney's third law: There are no technical solutions to
         management problems, but there are management solutions to
         technical problems.

   $ covert action
      (I) An operation that is planned and executed in a way that
      conceals the identity of the operator.

   $ covert channel
      1. (I) An unintended or unauthorized intra-system channel that
      enables two cooperating entities to transfer information in a way
      that violates the system's security policy but does not exceed the
      entities' access authorizations. (See: covert storage channel,
      covert timing channel, out of band.) out-of-band, tunnel.)

      2. (O) "A communications channel that allows two cooperating
      processes to transfer information in a manner that violates the
      system's security policy." [NCS04]

      Tutorial: The cooperating entities can be either two insiders or
      an insider and an outsider. Of course, an outsider has no access
      authorization at all. A covert channel is a system feature that
      the system architects neither designed nor intended for
      information transfer.

   $ covert storage channel
      (I) A system feature that enables one system entity to signal


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      storage location that is later directly or indirectly read by the
      second entity. (See: covert channel.)

   $ covert timing channel
      (I) A system feature that enable one system entity to signal
      information to another by modulating its own use of a system
      resource in such a way as to affect system response time observed
      by the second entity. (See: covert channel.)

   $ CPS
      (I) See: certification practice statement.

   $ cracker
      (I) Someone who tries to break the security of, and gain
      unauthorized access to, someone else's system without being invited. (Compare: hacker.
      See: system, often with
      malicious intent. (See: adversary, intruder, packet monkey, script kiddy.)
      kiddy. Compare: hacker.)

   $ CRAM
      (I) See: Challenge-Response Authentication Mechanism.

   $ CRC
      (I) See: cyclic redundancy check.

   $ credential
      1. (I) /authentication/ "Identity "identifier credential": A data object
      that is a portable representation of the association between an a
      identifier and a unit of authentication information, and that can
      be transferred or presented for use in proving a claim of verifying an identity claimed by an entity
      that
      identity. attempts to access a system. Example: X.509 public-key
      certificate. (See: anonymous credential.)

      2. (I) /access control/ "Authorization "authorization credential": A data object
      that is a portable representation of the association between an
      identifier and one or more access, access authorizations, and that can be transferred or
      presented for use when attempting to exercise in verifying those authorizations for an entity
      that attempts such access. Example: X.509 attribute certificate.
      (See: capability, capability token, ticket.)

      3. (D) /OSIRM/ "Data that is transferred to establish the claimed
      identity of an entity." [I7498 Part 2]

      Deprecated Definition: ISDs should not SHOULD NOT use the term with this
      definition. As explained in the tutorial below, an authentication
      process can involve the transfer of multiple data objects, and not
      all of those are credentials.

      4. (D) /U.S. Government/ "An object that is verified when
      presented to the verifier in an authentication transaction."
      [M0404]

      Deprecated Definition: ISDs should not SHOULD NOT use the term with this


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      definition; it mixes concepts in a potentially misleading way. For


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      example, in an authentication process, it is the identity that is
      "verified", not the credential; the credential is "validated".
      (See: validate vs. verify.)

      Tutorial: In general English, "credentials" are evidence or
      testimonials that (a) support a claim of identity or authorization
      and (b) usually are intended to be used more than once (i.e., a
      credential's life is long compared to the time needed for one
      use). Some examples are a policeman's badge, an automobile
      driver's license, and a national passport. An authentication or
      access control process that uses a badge, license, or passport is
      outwardly simple: the holder just shows the thing.

      The problem with adopting this term in Internet security is that
      an automation automated process for authentication or access control process usually
      requires multiple steps using multiple data objects, and it might
      not be immediately obvious which of those objects should get the
      name "credential".

      For example, if the verification step in a user authentication
      process employs public-key technology, then the process involves
      at least three data items: (a) the user's private key, (b) a
      signed value -- signed with that private key and passed to the
      system, perhaps in response to a challenge from the system -- and
      (c) the user's public-key certificate, which is validated by the
      system and provides the public key needed to verify the signature.
      -  Private key: The private key is *not* a credential, because it
         is never transferred or presented. Instead, the private key is
         "authentication information", which is associated with the
         user's identifier for a specified period of time and can be
         used in multiple authentications during that time.
      -  Signed value: The signed value is *not* a credential; the
         signed value is only ephemeral, not long lasting. The OSIRM
         definition could be interpreted to call the signed value a
         credential, but that would conflict with general English.
      - Certificate.  Certificate: The user's certificate *is* a credential. It can
         be "transferred" or "presented" to any person or process that
         needs it at any time. A public-key certificate may be used as
         an "identity credential", and an attribute certificate may be
         used as an "authorization credential".

   $ critical
      1. (I) /system resource/ A condition of a system resource such
      that denial of access to, or lack of availability of, that
      resource would jeopardize a system user's ability to perform a
      primary function or would result in other serious consequences,
      such as human injury or loss of life. (See: availability,
      precedence. Compare: sensitive.)

      2. (N) /extension/ An indication that an application is not
      permitted to ignore an extension. [X509]


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      Tutorial: Each extension of an X.509 certificate or CRL is flagged
      as either "critical" or "non-critical". In a certificate, if a
      computer program does not recognize an extension's type (i.e.,
      does not implement its semantics), then if the extension is
      critical, the program is required to treat the certificate as
      invalid; but if the extension is non-critical, the program is
      permitted to ignore the extension.

      In a CRL, if a program does not recognize a critical extension
      that is associated with a specific certificate, the program is
      required to assume that the listed certificate has been revoked
      and is no longer valid, and then take whatever action is required
      by local policy.

      When a program does not recognize a critical extension that is
      associated with the CRL as whole, the program is required to
      assume that all listed certificates have been revoked and are no
      longer valid. However, since failing to process the extension may
      mean that the list has not been completed, the program cannot
      assume that other certificates are valid, and the program needs to
      take whatever action is therefore required by local policy.

   $ critical information infrastructure
      (I) Those systems that are so vital to a nation that their
      incapacity or destruction would have a debilitating affect on
      national security, the economy, or public health and safety.

   $ CRL
      (I) See: certificate revocation list.

   $ CRL distribution point
      (I) See: distribution point.

   $ CRL extension
      (I) See: extension.

   $ cross-certificate
      (I) A public-key certificate issued by a CA in one PKI to a CA in
      another PKI. (See: cross-certification.)

   $ cross-certification
      (I) The act or process by which a CA in one PKI issues a public-
      key certificate to a CA in another PKI. [X509] (See: bridge CA.)

      Tutorial: X.509 says that a CA (say CA1) may issue a "cross-
      certificate" in which the subject is another CA (say CA2). X.509
      calls CA2 the "subject CA" and calls CA1 an "intermediate CA", but
      this Glossary deprecates those terms. (See: intermediate CA,
      subject CA).

      Cross-certification of CA2 by CA1 appears similar to certification


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      of a subordinate CA by a superior CA, but cross-certification


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      involves a different concept. The "subordinate CA" concept applies
      when both CAs are in the same PKI, i.e., when either (a) CA1 and
      CA2 are under the same root or (b) CA1 is itself a root. The
      "cross-certification" concept applies in other cases:

      First, cross-certification applies when two CAs are in different
      PKIs, i.e., when CA1 and CA2 are under different roots, or perhaps
      are both roots themselves. Issuing the cross-certificate enables
      end entities certified under CA1 in PK1 to construct the
      certification paths needed to validate the certificates of end
      entities certified under CA2 in PKI2. Sometimes, a pair of cross-
      certificates is issued -- by CA1 to CA2, and by CA2 to CA1 -- so
      that an end entity in either PKI can validate certificates issued
      in the other PKI.

      Second, X.509 says that two CAs in some complex, multi-CA PKI can
      cross-certify one another for the purpose of shortening the
      certification paths constructed by end entities. Whether or not a
      CA may perform this or any other form of cross-certification, and
      how such certificates may be used by end entities, should be
      addressed by the local certificate policy and CPS.

   $ cryptanalysis
      1. (I) The mathematical science that deals with analysis of a
      cryptographic system in order to gain knowledge needed to break or
      circumvent the protection that the system is designed to provide.
      (See: cryptology.)

      2. (O) "The analysis of a cryptographic system and/or its inputs
      and outputs to derive confidential variables and/or sensitive data
      including cleartext." [I7498 Part 2]

      Tutorial: Definition 2 states the traditional goal of
      cryptanalysis, i.e. convert cipher text to plain text (which
      usually is clear text) without knowing the key; but that
      definition applies only to encryption systems. Today, the term is
      used with reference to all kinds of cryptographic algorithms and
      key management, and definition 1 reflects that. In all cases,
      however, a cryptanalyst tries to uncover or reproduce someone
      else's sensitive data, such as clear text, a key, or an algorithm.
      The basic cryptanalytic attacks on encryption systems are
      ciphertext-only, known-plaintext, chosen-plaintext, and chosen-
      ciphertext; and these generalize to the other kinds of
      cryptography.

   $ crypto, CRYPTO
      1. (N) A prefix ("crypto-") that means "cryptographic".

      Usage: ISDs MAY use this prefix when it part of a term listed in
      this Glossary. Otherwise, ISDs SHOULD avoid this prefix; instead,
      use the adjective "cryptographic".


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      2. (D) /slang/ In lower case, "crypto" is a synonym an abbreviation for the
      adjective "cryptographic", or for the nouns "cryptography" or
      "cryptographic component".

      Deprecated Term: Abbreviation: ISDs SHOULD NOT use this slang term; term because it
      could easily be misunderstood.

      3. (O) /U.S. Government/ In upper case, "CRYPTO" is a marking or
      designator that identifies "COMSEC keying material used to secure
      or authenticate telecommunications carrying classified or
      sensitive U.S. Government or U.S. Government-derived information."
      [C4009]

   $ cryptographic
      (I) An adjective that refers to cryptography.

   $ cryptographic algorithm
      (I) An algorithm that uses the science of cryptography, including
      (a) encryption algorithms, (b) cryptographic hash algorithms, (c)
      digital signature algorithms, and (d) key agreement key-agreement algorithms.

   $ cryptographic application programming interface (CAPI)
      (I) The source code formats and procedures through which an
      application program accesses cryptographic services, which are
      defined abstractly compared to their actual implementation.
      Example, see: PKCS #11, [R2628].

   $ cryptographic association
      (I) A security association that involves the use of cryptography
      to provide security services for data exchanged by the associated
      entities. (See: ISAKMP.)

   $ cryptographic boundary
      (I) See: (secondary secondary definition under) cryptographic module. under "cryptographic module".

   $ cryptographic card
      (I) A cryptographic token in the form of a smart card or a PC
      card.

   $ cryptographic component
      (I) A generic term for any system component that involves
      cryptography. (See: cryptographic module.)

   $ cryptographic hash
      (I) See: (secondary secondary definition under) hash function. under "hash function".

   $ cryptographic ignition key (CIK)
      1. (I) A physical (usually electronic) token used to store,
      transport, and protect cryptographic keys. Usage: Sometimes
      abbreviated as "crypto-ignition key". (Compare: fill device.)



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      Tutorial: A typical use is to divide a split key between a CIK and


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      a cryptographic module, so that it is necessary to combine the two
      to regenerate a key-encrypting key and thus activate the module
      and other keys it contains.

      2. (O) "Device or electronic key used to unlock the secure mode of
      cryptographic equipment." [C4009]

   $ cryptographic key
      (I) See: key. Usage: Usually shortened to just "key".

   $ Cryptographic Message Syntax (CMS)
      (I) An encapsulation syntax (RFC 3852) for digital signatures,
      hashes, and encryption of arbitrary messages.

      Tutorial: CMS derives from PKCS #7. CMS values are specified with
      ASN.1 and use BER encoding. The syntax permits multiple
      encapsulation with nesting, permits arbitrary attributes to be
      signed along with message content, and supports a variety of
      architectures for digital certificate-based key management.

   $ cryptographic module
      (I) A set of hardware, software, firmware, or some combination
      thereof that implements cryptographic logic or processes,
      including cryptographic algorithms, and is contained within the
      module's "cryptographic boundary", which is an explicitly defined
      contiguous perimeter that establishes the physical bounds of the
      module. [FP140]

   $ cryptographic system
      1. (I) A set of cryptographic algorithms together with the key
      management processes that support use of the algorithms in some
      application context.

      Usage: ISDs SHOULD use definition 1 because it covers a wider
      range of algorithms than definition 2.

      2. (O) "A collection of transformations from plain text into
      cipher text and vice versa [which would exclude digital signature,
      cryptographic hash, and key agreement key-agreement algorithms], the particular
      transformation(s) to be used being selected by keys. The
      transformations are normally defined by a mathematical algorithm."
      [X509]

   $ cryptographic token
      1. (I) A portable, user-controlled, physical device (e.g., smart
      card or PCMCIA card) used to store cryptographic information and
      possibly also perform cryptographic functions. (See: cryptographic
      card, token.)

      Tutorial: A smart token might implement some set of cryptographic
      algorithms and might incorporate related key management functions,


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      such as a random number generator. A smart cryptographic token may


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      contain a cryptographic module or may not be explicitly designed
      that way.

   $ cryptography
      1. (I) The mathematical science that deals with transforming data
      to render its meaning unintelligible (i.e., to hide its semantic
      content), prevent its undetected alteration, or prevent its
      unauthorized use. If the transformation is reversible,
      cryptography also deals with restoring encrypted data to
      intelligible form. (See: cryptology, steganography.)

      2. (O) "The discipline which embodies principles, means, and
      methods for the transformation of data in order to hide its
      information content, prevent its undetected modification and/or
      prevent its unauthorized use ... . Cryptography determines the
      methods used in encipherment and decipherment." [I7498 Part 2]

      Tutorial: Comprehensive coverage of applied cryptographic
      protocols and algorithms is provided by Schneier [Schn].
      Businesses and governments use cryptography to make data
      incomprehensible to outsiders; to make data incomprehensible to
      both outsiders and insiders, the data is sent to lawyers for a
      rewrite.

   $ Cryptoki
      (N) See: (secondary definition under) A CAPI defined in PKCS #11. Pronunciation: "CRYPTO-key".
      Derivation: Abbreviation of "cryptographic token interface".

   $ cryptology
      (I) The science of secret communication, that includes both
      cryptography and cryptanalysis.

      Tutorial: Sometimes the term is used more broadly to denote
      activity that includes both rendering signals secure (see: signal
      security) and extracting information from signals (see: signal
      intelligence) [Kahn].

   $ cryptonet
      (I) A network (i.e., a communicating set) of system entities that
      share a secret cryptographic key for a symmetric algorithm. (See:
      controlling authority.)

      (O) "Stations holding a common key." [C4009]

   $ cryptoperiod
      (I) The time span during which a particular key value is
      authorized to be used in a cryptographic system. (See: key
      management.)

      Usage: This term is long-established in COMPUSEC usage. In the
      context of certificates and public keys, "key lifetime" and
      "validity period" are often used instead.


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      "validity period" are often used instead.

      Tutorial: A cryptoperiod is usually stated in terms of calendar or
      clock time, but sometimes is stated in terms of the maximum amount
      of data permitted to be processed by a cryptographic algorithm
      using the key. Specifying a cryptoperiod involves a tradeoff
      between the cost of rekeying and the risk of successful
      cryptoanalysis.

   $ cryptosystem
      (I) Contraction of "cryptographic system".

   $ cryptovariable
      (D) Synonym for "key".

      Deprecated Usage: In contemporary COMSEC usage, the term "key" has
      replaced the term "cryptovariable".

   $ CSIRT
      (I) See: computer security incident response team.

   $ CSOR
      (N) See: Computer Security Objects Register.

   $ CTAK
      (D) See: ciphertext auto-key.

   $ cut-and-paste attack
      (I) An active attack on the data integrity of cipher text,
      effected by replacing sections of cipher text with other cipher
      text, such that the result appears to decrypt correctly but
      actually decrypts to plain text that is forged to the satisfaction
      of the attacker.

   $ cyclic redundancy check (CRC)
      (I) A type of checksum algorithm that is not a cryptographic hash
      but is used to implement data integrity service where accidental
      changes to data are expected. Sometimes called "cyclic redundancy
      code".

   $ DAC
      (N) See: Data Authentication Code, discretionary access control.

      Deprecated Usage: This abbreviation is ambiguous; therefore, ISDs that use it this term SHOULD state a
      definition for it. it because this abbreviation is ambiguous.

   $ daemon
      (I) A computer program that is not invoked explicitly but waits
      until a specified condition occurs, and then runs with no
      associated user (principal), usually for an administrative
      purpose. (See: zombie.)



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   $ dangling threat
      (N)
      (O) A threat to a system for which there is no corresponding


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      vulnerability and, therefore, no implied risk. [C4009]

   $ dangling vulnerability
      (N)
      (O) A vulnerability of a system for which there is no
      corresponding threat and, therefore, no implied risk. [C4009]

   $ DASS
      (I) See: Distributed Authentication Security Service.

   $ data
      (I) Information in a specific representation, usually as a
      sequence of symbols that have meaning and especially a
      representation meaning.

      Usage: Refers to both (a) representations that can be processed recognized,
      processed, or produced by a computer. computer or other type of machine, and
      (b) representations that can be handled by a human.

   $ Data Authentication Algorithm, data authentication algorithm
      (N) /capitalized/ The ANSI standard for a keyed hash function that
      is equivalent to DES cipher block chaining with IV = 0. [A9009]

      (D) /not capitalized/ Synonym for "checksum".

      Deprecated Term: ISDs SHOULD NOT use the uncapitalized form, "data
      authentication algorithm", as a synonym for other kinds of
      checksums.

   $ Data Authentication Code, data authentication code
      1. (N) /capitalized/ A specific U.S. Government standard [FP113]
      for a checksum that is computed by the Data Authentication
      Algorithm. (Also known as the ANSI standard Usage: a.k.a. Message Authentication Code [A9009].)
      (See: DAC.)

      2. (D) /not capitalized/ Synonym for checksum.

      Deprecated Term: ISDs SHOULD NOT use "data authentication code" as
      a synonym for other kinds of checksums; that usage would mix
      concepts in a potentially misleading way (see: authentication
      code). Instead, use "checksum", "error detection code", "hash",
      "keyed hash", "Message Authentication Code", or "protected
      checksum", depending on what is meant.

   $ data compromise
      (I) A security incident in which information is exposed to
      potential unauthorized access, such that unauthorized disclosure,
      alteration, or use of the information may have occurred. (Compare:
      security compromise.)

      (O) A "compromise" is "A communication a "communication or physical transfer of
      information to an unauthorized recipient." [DoD5]


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   $ data confidentiality
      (I) The property that data is not disclosed to system entities
      unless they have been authorized to know the data. (See: Bell-
      LaPadula model, classification, data confidentiality service.


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      Compare: privacy.)

      (D) "The property that information is not made available or
      disclosed to unauthorized individuals, entities, or processes
      [i.e., to any unauthorized system entity]." [I7498 Part 2].

      Deprecated Definition: The phrase "made available" might be
      interpreted to mean that the data could be altered, and that would
      confuse this term with the concept of "data integrity".

   $ data confidentiality service
      (I) A security service that protects data against unauthorized
      disclosure. (See: access control, data confidentiality, datagram
      confidentiality service, flow control, inference control.)

      Deprecated Definition: ISDs SHOULD NOT use this term as a synonym
      for "privacy", which is a different concept.

   $ Data Encryption Algorithm (DEA)
      (N) A symmetric block cipher, defined in the U.S. Government's
      DES. DEA uses a 64-bit key, of which 56 bits are independently
      chosen and 8 are parity bits, and maps a 64-bit block into another
      64-bit block. [FP046] (See: AES, symmetric cryptography.)

      Usage: This algorithm is usually referred to as "DES". The
      algorithm has also been adopted in standards outside the
      Government (e.g., [A3092]).

   $ data encryption key (DEK)
      (I) A cryptographic key that is used to encipher application data.
      (Compare: key-encrypting key.)

   $ Data Encryption Standard (DES)
      (N) A U.S. Government standard [FP046] that specifies the DEA and
      states policy for using the algorithm to protect unclassified,
      sensitive data. (See: AES.)

   $ data integrity
      1. (I) The property that data has not been changed, destroyed, or
      lost in an unauthorized or accidental manner. (See: Biba model, data integrity service.)
      service. Compare: correctness integrity, source integrity.)

      2. (O) "The property that information has not been modified or
      destroyed in an unauthorized manner." [I7498 Part 2]

      Usage: Deals with (a) constancy of and confidence in data values,
      and not with either (b) information that the values represent


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      (see: correctness integrity) or (c) the trustworthiness of the
      source of the values (see: source integrity).

   $ data integrity service
      (I) A security service that protects against unauthorized changes


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      to data, including both intentional change or destruction and
      accidental change or loss, by ensuring that changes to data are
      detectable. (See: data integrity.) integrity, checksum, datagram integrity
      service.)

      Tutorial: A data integrity service can only detect a change and
      report it to an appropriate system entity; changes cannot be
      prevented unless the system is perfect (error-free) and no
      malicious user has access. However, a system that offers data
      integrity service might also attempt to correct and recover from
      changes.

      The ability of this service to detect changes is limited by the
      technology of the mechanisms used to implement the service. For
      example, if the mechanism were a one-bit parity check across each
      entire SDU, then changes to an odd number of bits in an SDU would
      be detected, but changes to an even number of bits would not.

      Relationship between data integrity service and authentication
      services: Although data integrity service is defined separately
      from data origin authentication service and peer entity
      authentication service, it is closely related to them.
      Authentication services depend, by definition, on companion data
      integrity services. Data origin authentication service provides
      verification that the identity of the original source of a
      received data unit is as claimed; there can be no such
      verification if the data unit has been altered. Peer entity
      authentication service provides verification that the identity of
      a peer entity in a current association is as claimed; there can be
      no such verification if the claimed identity has been altered.

   $ data origin authentication
      (I) "The corroboration that the source of data received is as
      claimed." [I7498 Part 2] (See: authentication.)

   $ data origin authentication service
      (I) A security service that verifies the identity of a system
      entity that is claimed to be the original source of received data.
      (See: authentication, authentication service.)

      Tutorial: This service is provided to any system entity that
      receives or holds the data. Unlike peer entity authentication
      service, this service is independent of any association between
      the originator and the recipient, and the data in question may
      have originated at any time in the past.

      A digital signature mechanism can be used to provide this service,


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      because someone who does not know the private key cannot forge the
      correct signature. However, by using the signer's public key,
      anyone can verify the origin of correctly signed data.

      This service is usually bundled with connectionless data integrity
      service. (See: ("relationship "relationship between data integrity service and
      authentication services" under) data under "data integrity service. service".

   $ data owner
      (O) /U.S. Government/
      (N) The organization that has the final statutory and operational
      authority for specified information.



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   $ data privacy
      (D) Synonym for "data confidentiality".

      Deprecated Term: ISDs SHOULD NOT use this term; it mixes concepts
      in a potentially misleading way. Instead, use either "data
      confidentiality" or "privacy" or both, depending on what is meant.

   $ data recovery
      1. (I) /cryptanalysis/ A process for learning, from some cipher
      text, the plain text that was previously encrypted to produce the
      cipher text. (See: recovery.)

      2. (I) /system integrity/ The process of restoring information
      following damage or destruction.

   $ data security
      (I) The protection of data from disclosure, alteration,
      destruction, or loss that either is accidental or is intentional
      but unauthorized.

      Tutorial: Both data confidentiality service and data integrity
      service are needed to achieve data security.

   $ datagram
      (I) "A self-contained, independent entity of data [i.e., a data
      object, a discrete set of bits] packet]
      carrying sufficient information to be routed from the source
      [computer] to the destination." destination computer without reliance on earlier
      exchanges between this source and destination computer and the
      transporting network." Example: A PDU of IP. [R1983]

   $ datagram confidentiality service
      (I) A data confidentiality service that preserves the
      confidentiality of data in a single, independent, packet; i.e.,
      the service applies to datagrams one-at-a-time. Example: ESP.
      (See: data confidentiality.)

      Usage: When a protocol is said to provide data confidentiality
      service, this is usually understood to mean that only the SDU is
      protected in each packet. ISDs that use the term to mean that the
      entire PDU is protected should include a highlighted definition.


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      Tutorial: This basic form of network confidentiality service
      suffices for protecting the data in a stream of packets in both
      connectionless and connection-oriented protocols. Except perhaps
      for traffic flow confidentiality, nothing further is needed to
      protect the confidentiality of data carried by a packet stream.
      The OSIRM distinguishes between connection confidentiality and
      connectionless confidentiality. The IPS need not make that
      distinction, because those services are just instances of the same
      service (i.e., datagram confidentiality) being offered in two
      different protocol contexts. (For data integrity service, however,
      additional effort is needed to protect a stream, and the IPS does
      need to distinguish between "datagram integrity service" and
      "stream integrity service".)

   $ datagram integrity service
      (I) A data integrity service that preserves the integrity of data
      in a single, independent, data packet (i.e., the service applies
      to datagrams one-at-a-time). (See: data integrity. Compare: stream
      integrity service.)

      Tutorial: The ability to provide appropriate data integrity is
      important in many Internet security situations, and so there are
      different kinds of data integrity services suited to different
      applications. This service is the simplest kind; it is suitable
      for connectionless data transfers.

      Datagram integrity service usually is designed only to attempt to
      detect changes to the SDU in each packet, but it might also
      attempt to detect changes to some or all of the PCI in each packet
      (see: selective field integrity). In contrast to this simple, one-
      at-a-time service, some security situations demand a more complex
      service that also attempts to detect deleted, inserted, or
      reordered datagrams within a stream of datagrams (see: stream
      integrity service).

   $ DEA
      (N) See: Data Encryption Algorithm.

   $ deception
      (I) A circumstance or event that may result in an authorized
      entity receiving false data and believing it to be true. (See:
      authentication.)

      Tutorial: This is a type of threat consequence, and it can be
      caused by the following types of threat actions: masquerade,
      falsification, and repudiation.

   $ decipher
      (D) Synonym for "decrypt".

      Deprecated Definition: ISDs SHOULD NOT use this term as a synonym
      for "decrypt". However,


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      for "decrypt". However, see usage note under "encryption".

   $ decipherment
      (D) Synonym for "decryption".

      Deprecated Definition: ISDs SHOULD NOT use this term as a synonym
      for "decryption". However, see the usage Usage note under "encryption".



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   $ declassification
      (I) An authorized process by which information is declassified.
      (See: classification.)

   $ declassify
      (I) To officially remove the security level designation of a
      classified information item or information type, such that the
      information is no longer classified (i.e., becomes unclassified).
      (See: classified, classify, security level. Compare: downgrade.)

   $ decode
      1. (I) Convert encoded data back to its original form of
      representation. (Compare: decrypt.)

      2. (D) Synonym for "decrypt".

      Deprecated Definition: Encoding is not usually meant to conceal
      meaning. Therefore, ISDs SHOULD NOT use this term as a synonym for
      "decrypt", because that would mix concepts in a potentially
      misleading way.

   $ decrypt
      (I) Cryptographically restore cipher text to the plaintext form it
      had before encryption.

   $ decryption
      (I) See: (secondary secondary definition under) encryption. under "encryption".

   $ dedicated security mode
      (I) A mode of system operation of an information system, wherein all users have the clearance or authorization, and having access to
      the need-to-know, system possess, for all data handled by the system. system, both (a)
      all necessary authorizations (i.e., security clearance and formal
      access approval) and (b) a need-to-know. (See: /system operation/
      under "mode", formal access approval, need to know, protection
      level, security clearance.)

      Usage: Usually abbreviated as "dedicated mode". This mode was
      defined in U.S. Government policy on system accreditation, but the
      term is also used outside the Government. In this mode, the system
      may handle either (a) a single classification level or category of
      information or (b) a range of levels and categories. [DoD2]

      Usage: This mode was defined in U.S. DoD policy on system
      accreditation, but the term is also used outside the Government.

   $ default account
      (I) A system login account (usually accessed with a user


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      identifier and password) that has been predefined in a
      manufactured system to permit initial access when the system is
      first put into service. (See: harden.]

      Tutorial: A default account becomes a serious vulnerability if not
      properly administered. Sometimes, the default user name identifier and
      password are well-known because they are the same in each copy of
      the system. In any case, when the a system is put into service, the any
      default password should immediately be changed or the default
      account should be disabled.

   $ defense in depth
      (I) An approach to constructing security architectures that uses
      layered and complementary security mechanisms and countermeasures,
      so that if one security mechanism is defeated, one or more other
      mechanisms (which are "behind" or "beneath" the first mechanism)
      still provide protection.

      Tutorial: This concept is appealing because it aligns with
      traditional warfare doctrine, which applies defense in depth to
      physical, geospatial structures. It is more difficult to apply the
      concept to logical, cyberspace structures of computer networks.
      The concept assumes that networks have a spatial or topological
      representation. It also assumes that there can be implemented --


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      from the "outer perimeter" of a network, through its various
      "layers" of components, to its "center" (i.e., to the subscriber
      application systems supported by the network) -- a varied series
      of countermeasures that together provide adequate protection.
      However, it is more difficult to map the topology of networks and
      make certain that no paths exist path exists by which an attacker could bypass
      all defensive layers.

   $ Defense Information Infrastructure (DII)
      (O) /U.S. DoD/ The U.S. DoD's shared or shared, interconnected system of
      computers, communications, data, applications, security, people,
      training, and other support structure, structures, serving local and worldwide information needs. needs
      worldwide. (See: DISN.) Usage: Has evolved to be called the GIG.

      Tutorial: The DII connects U.S. DoD mission support, command and control,
      and intelligence computers and users through voice, data, imagery,
      video, and multimedia services, and provides information
      processing and value-added services to subscribers over the DISN.
      Users' own data and application software are not considered part
      of the DII.

   $ Defense Information Systems Network (DISN)
      (O) /U.S. DoD/ The U.S. DoD's consolidated, worldwide, enterprise
      level telecommunications infrastructure that provides end-to-end
      information transfer for supporting military operations; a part of
      the DII. (Compare: GIG.)




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   $ degauss
      1a. (N) Apply a magnetic field to permanently remove, erase, or
      clear data from a magnetic storage medium, such as a tape or disk
      [NCS25].

      1b. (N) Reduce magnetic flux density to zero by applying a
      reversing magnetic field. (See: magnetic remanence.)

   $ degausser
      (N) An electrical device that can degauss magnetic storage media.

   $ DEK
      (I) See: data encryption key.

   $ delay
      (I) /packet/ See: secondary definition under "stream integrity
      service".

   $ deletion
      (I) /packet/ See: secondary definition under "stream integrity
      service".

   $ delta CRL
      (I) A partial CRL that only contains entries for X.509
      certificates that have been revoked since the issuance of a prior,
      base CRL. This method can be used to partition CRLs that become
      too large and unwieldy. (Compare: CRL distribution point.)

   $ demilitarized zone (DMZ)
      (D) Synonym for "buffer zone".

      Deprecated Term: Usage: ISDs SHOULD NOT use this term with this
      definition; that definition because such
      usage would mix concepts in a potentially misleading


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      Deprecated Usage under) Green Book.) under "Green Book".)

   $ denial of service
      (I) The prevention of authorized access to a system resource or
      the delaying of system operations and functions. (See:
      availability, critical, flooding.)

      Tutorial: A denial-of-service attack can prevent the normal
      conduct of business on the Internet. There are four types of
      solutions to this security problem:
      -  Awareness: Maintaining cognizance of security threats and
         vulnerabilities. (See: CERT.)
      -  Detection: Finding attacks on end systems and subnetworks.
         (See: intrusion detection.)
      -  Prevention: Following defensive practices on network-connected
         systems. (See: [RFC 2167].) [R2827].)
      -  Response: Reacting effectively when attacks occur. (See: CSIRT,
         contingency plan.)



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   $ DES
      (N) See: Data Encryption Standard.

   $ designated approving authority (DAA)
      (O) /U.S. Government/ Synonym for "accreditor".

   $ detection
      (I) See: secondary definition under "security".

   $ deterrence
      (I) See: secondary definition under "security".

   $ dictionary attack
      (I) An attack that uses a brute-force technique of successively
      trying all the words in some large, exhaustive list.

      Examples: An attack on Attack an authentication service by trying all possible
      passwords. An attack on Attack an encryption service by encrypting some known
      plaintext phrase with all possible keys so that the key for any
      given encrypted message containing that phrase may be obtained by
      lookup.

   $ Diffie-Hellman
      (N) A key-agreement algorithm published in 1976 by Whitfield
      Diffie and Martin Hellman [DH76, R2631].

      Tutorial: Diffie-Hellman does key establishment, not encryption.
      However, the key that it produces may be used for encryption, for
      further key management operations, or for any other cryptography.

      The algorithm is described in [R2631] and [Schn]. In brief, Alice
      and Bob together pick large integers that satisfy certain
      mathematical conditions, and then use the integers to each
      separately compute a public-private key pair. They send each other
      their public key. Each person uses their own private key and the
      other person's public key to compute a key, k, that, because of
      the mathematics of the algorithm, is the same for each of them.
      Passive wiretapping cannot learn the shared k, because k is not
      transmitted, and neither are the private keys needed to compute k.


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      The difficulty of breaking Diffie-Hellman is considered to be
      equal to the difficulty of computing discrete logarithms modulo a
      large prime. However, without additional mechanisms to
      authenticate each party to the other, a protocol based on the
      algorithm may be vulnerable to a man-in-the-middle attack.

   $ digest
      See: message digest.

   $ digital certificate
      (I) A certificate document in the form of a digital data object (a
      data object used by a computer) to which is appended a computed


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      digital signature value that depends on the data object. (See:
      attribute certificate, capability, public-key certificate.)

      Deprecated Usage: ISDs SHOULD NOT use this term to refer to a
      signed CRL or CKL. Although the recommended definition can be
      interpreted to include other signed items, the security community
      does not use the term with those meanings.

   $ digital certification
      (D) Synonym for "certification".

      Deprecated Definition: ISDs SHOULD NOT use this definition unless
      the context is not sufficient to distinguish between digital
      certification and another kind of certification, in which case it
      would be better to use "public-key certification" or another
      phrase that indicates what is being certified.

   $ digital document
      (I) An electronic data object that represents information
      originally written in a non-electronic, non-magnetic medium
      (usually ink on paper) or is an analogue of a document of that
      type.

   $ digital envelope
      (I) A combination of (a) encrypted content data (of any kind)
      intended for a recipient and (b) the content encryption key in an
      encrypted form that has been prepared for the use of the
      recipient.

      Usage: In ISDs, the term should SHOULD be defined at the point of first
      use because, although the term is defined in PKCS #7 and used in
      S/MIME, it is not widely known.

      Tutorial: Digital enveloping is not simply a synonym for
      implementing data confidentiality with encryption; digital
      enveloping is a hybrid encryption scheme to "seal" a message or
      other data, by encrypting the data and sending both it and a
      protected form of the key to the intended recipient, so that no
      one other than the intended recipient can "open" the message. In


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      PCKS
      PKCS #7, it means first encrypting the data using a symmetric
      encryption algorithm and a secret key, and then encrypting the
      secret key using an asymmetric encryption algorithm and the public
      key of the intended recipient. In S/MIME, additional methods are
      defined for encrypting the content encryption key.

   $ Digital ID(service mark)
      (D) Synonym for "digital certificate".

      Deprecated Term: ISDs SHOULD NOT use this term as a synonym for
      "digital certificate". The term (a) term. It is the a service
      mark of a commercial firm firm, and (b) it unnecessarily duplicates the
      meaning of
      other, well-established terms. a better-established term. (See: credential.)



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   $ digital key
      (D) A synonym for an input parameter of a cryptographic algorithm
      or other process.

      Deprecated Usage: The adjective "digital" need not be used with
      "key" or "cryptographic key", unless the context is insufficient
      to distinguish the digital key from another kind of key, such as a
      metal key for a door lock.

   $ digital notary
      (I) An electronic functionary analogous to a notary public.
      Provides a trusted time stamp for a digital document, so that
      someone can later prove that the document existed at that point in
      time; verifies the signature(s) on a signed document before
      applying the stamp. (See: notarization.)

   $ digital signature
      1. (I) A value computed with a cryptographic algorithm and
      appended to a data object in such a way that any recipient of the
      data can use the signature to verify the data's origin and
      integrity. (See: data origin authentication service, data
      integrity service, signer. Compare: digitized signature,
      electronic signature.)

      2. (I) "Data appended to, or a cryptographic transformation of, a
      data unit that allows a recipient of the data unit to prove the
      source and integrity of the data unit and protect against forgery,
      e.g. by the recipient." [I7498 Part 2]

      Tutorial: A digital signature should have these properties:
      -  Uniquely identify a system entity as being the signer.
      -  Be under the signer's sole control, so that it cannot be
         created by any other entity.
      -  Be capable of being verified. (See: validate vs. verify.)
      -  Be bound to the signed data object in such a way that if the
         data is changed, then when an attempt is made to verify the
         signature, it will be seen as not authentic.

      To achieve these properties, the data object is first input to a
      hash function, and then the hash result is cryptographically
      transformed using a private key of the signer. The final resulting
      value is called the digital signature of the data object. The
      signature value is a protected checksum, because the properties of


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      a cryptographic hash ensure that if the data object is changed,
      the digital signature will no longer match it. The digital
      signature is unforgeable because one cannot be certain of
      correctly creating or changing the signature without knowing the
      private key of the supposed signer.

      Some digital signature schemes use a an asymmetric encryption
      algorithm (e.g., see: RSA) to transform the hash result. Thus,
      when Alice needs to sign a message to send to Bob, she can use her


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      private key to encrypt the hash result. Bob receives both the
      message and the digital signature. Bob can use Alice's public key
      to decrypt the signature, and then compare the plaintext result to
      the hash result that he computes by hashing the message himself.
      If the values are equal, Bob accepts the message because he is
      certain that it is from Alice and has arrived unchanged. If the
      values are not equal, Bob rejects the message because either the
      message or the signature was altered in transit.

      Other digital signature schemes (e.g., see: DSS) transform the
      hash result with an algorithm (e.g., see: DSA, El Gamal) that
      cannot be directly used to encrypt data. Such a scheme creates a
      signature value from the hash and provides a way to verify the
      signature value, but does not provide a way to recover the hash
      result from the signature value. In some countries, such a scheme
      may improve exportability and avoid other legal constraints on
      usage. Alice sends the signature value to Bob along with both the
      message and its hash result. The algorithm enables Bob to use
      Alice's public signature key and the signature value to verify the
      hash result he receives. Then, as before, he compares that hash
      result she sent to the one that he computes by hashing the message
      himself.

   $ Digital Signature Algorithm (DSA)
      (N) An asymmetric cryptographic algorithm for a digital signature
      in the form of a pair of large numbers. The signature is computed
      using rules and parameters such that the identity of the signer
      and the integrity of the signed data can be verified. (See: DSS.)

   $ Digital Signature Standard (DSS)
      (N) The U.S. Government standard [FP186] that specifies the DSA.

   $ digital watermarking
      (I) Computing techniques for inseparably embedding unobtrusive
      marks or labels as bits in digital data -- text, graphics, images,
      video, or audio -- and for detecting or extracting the marks
      later.

      Tutorial: The set of embedded bits (the digital watermark) is
      sometimes hidden, usually imperceptible, and always intended to be
      unobtrusive. Depending on the particular technique that is used,
      digital watermarking can assist in proving ownership, controlling
      duplication, tracing distribution, ensuring data integrity, and


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      performing other functions to protect intellectual property
      rights. [ACM]

   $ digitized signature
      (D) Denotes various forms of digitized images of handwritten
      signatures. (Compare: digital signature).

      Deprecated Term: ISDs SHOULD NOT use this term; it looks like
      sloppy term without including
      this definition. This term suggests careless use of "digital


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      signature", which is the term standardized by [I7498 Part 2].
      (See: electronic signature.)

   $ DII
      (O) See: Defense Information Infrastructure.

   $ directory, Directory
      1. (I) /not capitalized/ Refers generically to a database server
      or other system that stores and provides information -- such as a digital
      certificate access to values of
      descriptive or CRL -- about an entity whose name is known.
      (Compare: operational data items that are associated with the
      components of a system. (Compare: repository.)

      2. (N) /capitalized/ Refers specifically to the X.500 Directory.
      (See: DN, X.500.)

   $ Directory Access Protocol (DAP)
      (N) An OSI protocol [X519] for communication between a Directory
      User Agent (a type of X.500 client) and a Directory System Agent
      (a type of X.500 server). (See: LDAP.)

   $ disaster plan
      (O) Synonym for "contingency plan".

      Deprecated Term: ISDs SHOULD NOT use this term; instead, for
      consistency and neutrality of language, ISDs SHOULD use
      "contingency plan".

   $ disclosure
      See: unauthorized disclosure. Compare: exposure.

   $ discretionary access control
      1a. (I) An access control service that (a) enforces a security
      policy based on the identity of system entities and the
      authorizations associated with those identities. the identities and (b) incorporates
      a concept of ownership in which access rights for a system
      resource may be granted and revoked by the entity that owns the
      resource. (See: access control list, DAC, identity-based security
      policy, mandatory access control.)

      Derivation: This service is termed "discretionary" because an
      entity can be granted access rights to a resource such that the
      entity can by its own volition enable other entities to access the
      resource. That is, the service can incorporate a concept of
      ownership in which access rights can be granted and revoked by the
      user that owns the resource.

      1b. (O) /formal model/ "A means of restricting access to objects


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      based on the identity of subjects and/or groups to which they
      belong. The controls are discretionary in the sense that a subject
      with a certain access permission is capable of passing that
      permission (perhaps indirectly) on to any other subject." [DoD1]

   $ DISN
      (O) See: Defense Information Systems Network (DISN).


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   $ disruption
      (I) A circumstance or event that interrupts or prevents the
      correct operation of system services and functions. (See:
      availability, critical, system integrity.) integrity, threat consequence.)

      Tutorial: Disruption is a type of threat consequence; it can be
      caused by the following types of threat actions: incapacitation,
      corruption, and obstruction.

   $ Distinguished Encoding Rules (DER)
      (N) A subset of the Basic Encoding Rules, which gives exactly Rules that always provides only
      one way to represent encode any ASN.1 value as data structure defined by ASN.1. [X690].

      Tutorial: For a data structure defined abstractly in ASN.1, BER
      often provides for encoding the structure into an octet string [X690].

      Tutorial: There usually is in
      more than one way to encode way, so that two separate BER implementations can
      legitimately produce different octet strings for the same ASN.1 in
      BER.
      definition. However, some applications require all encodings of a
      structure to be the same, so that encodings can be compared for
      equality. Therefore, DER is used in applications in which a unique
      encoding is needed, such as when a digital signature is computed
      on an ASN.1 value. a structure defined by ASN.1.

   $ distinguished name (DN)
      (N) An identifier that uniquely represents an object in the X.500
      Directory Information Tree (DIT) [X501]. (Compare: domain name,
      identity.)

      Tutorial: A DN is a set of attribute values that identify the path
      leading from the base of the DIT to the object that is named. An
      X.509 public-key certificate or CRL contains a DN that identifies
      its issuer, and an X.509 attribute certificate contains a DN or
      other form of name that identifies its subject.

   $ distributed attack
      1a. (I) An attack that is implemented with distributed computing.
      (See: zombie.)

      1b. (I) An attack that deploys multiple threat agents.

   $ Distributed Authentication Security Service (DASS)
      (I) An experimental Internet protocol [R1507] that uses
      cryptographic mechanisms to provide strong, mutual authentication
      services in a distributed environment.

   $ distributed computing
      (I) A technique that disperses a single, logically related set of
      tasks among a group of geographically separate yet cooperating
      computers. (See: distributed attack.)




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   $ distribution point
      (I) An X.500 Directory entry or other information source that is
      named in a v3 X.509 public-key certificate extension as a location
      from which to obtain a CRL that may list the certificate.

      Tutorial: A v3 X.509 public-key certificate may have a
      "cRLDistributionPoints" extension that names places to get CRLs on
      which the certificate might be listed. (See: certificate profile.)
      A CRL obtained from a distribution point may (a) cover either all
      reasons for which a certificate might be revoked or only some of
      the reasons, (b) be issued by either the authority that signed the
      certificate or some other authority, and (c) contain revocation
      entries for only a subset of the full set of certificates issued
      by one CA or (d) contain revocation entries for multiple CAs.

   $ DMZ
      (D) See: demilitarized zone.

   $ DN
      (N) See: distinguished name.

   $ DNS
      (I) See: Domain Name System.

   $ doctrine
      See: security doctrine.

   $ DoD
      (N) Department of Defense.

      Usage: To ensure avoid international understanding, misunderstanding, ISDs should SHOULD use
      this abbreviation only with a national qualifier (e.g., U.S. DoD).

   $ DOI
      (I) See: Domain of Interpretation.

   $ domain
      1a. (I) /general security/ An environment or context that is
      defined by a security policy, security model, or security
      architecture to include (a)
      includes a set of system resources and a set of system entities
      that have the right to access the resources. resources and (b) usually is
      defined by a security policy, security model, or security
      architecture. (See: domain of interpretation, security perimeter.
      Compare: COI, enclave.)

      Tutorial: A "controlled interface" or "guard" is required to
      transfer information between network domains that operate under
      different security policies.

      1b. (O) /security policy/ A set of users, their information
      objects, and a common security policy. [DGSA, SP33]

      1c. (O) /security policy/ A system or collection of systems that


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      (a) belongs to a community of interest that implements a
      consistent security policy and (b) is administered by a single
      authority.

      2. (N) (O) /computer security/ A operating state or mode of a set of
      computer hardware.

      Tutorial: Most computers have at least two hardware operating
      modes [Gass]:
      -  "Privileged" mode: Also called "executive", "master", "system",
         kernel", or "supervisor" mode. In this mode, software can
         execute any all machine instruction instructions and access any machine storage. all storage
         locations.
      -  "Unprivileged" mode: Also called "user", "application", or
         "problem" mode. In this mode, software is restricted to a
         subset of the instructions and a subset of the storage. storage
         locations.

      3. (O) "A distinct scope within which certain common
      characteristics are exhibited and common rules are observed."
      [CORBA]

      4. (O) /MISSI/ The domain of a MISSI CA is the set of MISSI users
      whose certificates are signed by the CA.

      5. (I) /Internet/ That part of the Internet domain tree-structured name space tree
      (RFC 1034) of
      the DNS that is at or below the name that specifies the domain. A
      domain is a subdomain of another domain if it is contained within
      that domain. For example, D.C.B.A is a subdomain of C.B.A.
      (See: Domain Name System.)

      4. (O) /MISSI/ The domain of a MISSI CA is the set of MISSI users
      whose certificates are signed by the CA.

      5. C.B.A

      6. (O) /OSI/ An administrative partition of a complex distributed
      OSI system.

      6. (O) "A distinct scope within which certain common
      characteristics are exhibited and common rules are observed."
      [CORBA]

   $ domain name
      (I) The style of identifier that is defined for subtrees in the
      Internet DNS -- i.e., a sequence of case-insensitive ASCII labels
      separated by dots (e.g., "bbn.com") -- defined for
      subtrees in the Internet DNS and also is used in other
      types of Internet identifiers, like such as host names (e.g.,
      "rosslyn.bbn.com"), mailbox names (e.g., "rshirey@bbn.com."), "rshirey@bbn.com.") and
      URLs (e.g., "http://www.rosslyn.bbn.com./foo"). (See: DN, domain.)

      Tutorial: The name space of the DNS (RFC 1591) is a tree structure in which
      each node and leaf holds records describing a resource. Each node
      has a label. The domain name of a node is the list of labels on
      the path from the node to the root of the tree. The labels in a
      domain name are printed or read left to right, from the most
      specific (lowest, farthest from the root) to the least specific
      (highest, closest to the root), but the root's label is the null
      string. (See: country code.)

   $ Domain Name System (DNS)
      (I) The main Internet operations database, which is distributed


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      over a collection of servers and used by client software for
      purposes such as (a) translating a domain name-style host name
      into an IP address (e.g., "rosslyn.bbn.com" is translates to
      "192.1.7.10") and (b) locating a host that accepts mail for some a
      given mailbox address. [R1034]



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      Tutorial: The DNS has three major components: (a)
      -  Domain name space and resource records: Specifications for the
         tree-structured domain name space, and data associated with the
         names. (b)
      -  Name servers: Programs that hold information about a subset of
         the tree's structure and data holdings, and also hold pointers
         to other name servers that can provide information from any
         part of the tree. (c)
      -  Resolvers: Programs that extract information from name servers
         in response to client requests; typically, system routines
         directly accessible to user programs.

      Extensions to the DNS [R2065, R2137, R2536] [R2535, R2536, R3007] support (a) key
      distribution for public keys needed for the DNS and for other
      protocols, (b) data origin authentication service and data
      integrity service for resource records, (c) data origin
      authentication service for transactions between resolvers and
      servers, and (d) access control of records.

   $ domain of interpretation (DOI)
      (I) /IPsec/ An ISAKMP/IKE DOI for ISAKMP or IKE defines payload formats,
      exchange types, and conventions for naming security-relevant
      information such as security policies or cryptographic algorithms
      and modes. Example: See [R2407].

      Derivation: The DOI concept is based on work by the TSIG's CIPSO
      Working Group.

   $ dominate
      (I) Security level A is said to "dominate" security level B if the
      hierarchical
      (hierarchical) classification level of A is greater (higher) than
      or equal to that of B B, and the nonhierarchical A's (nonhierarchical) categories of A
      include all of those of B. B's categories. (See: lattice, lattice model.)

   $ dongle
      (I) A portable, physical, usually electronic device that is
      required to be attached to a computer to enable a particular
      software program to run. (See: token.)

      Tutorial: A dongle is essentially a physical key used for copy
      protection of software, because software; that is, the program will not run unless
      the matching dongle is attached. When the software runs, it
      periodically queries the dongle and quits if the dongle does not
      reply with the proper authentication information. Dongles were
      originally constructed as an EPROM (erasable programmable read-
      only memory) to be connected to a serial input-output port of a


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      personal computer.

   $ downgrade
      (I) /data security/ Reduce the classification security level of data (especially
      the classification level) without changing the information content
      of the data. (Compare: (See: regrade, upgrade. See: regrade.)




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   $ draft RFC
      (D) A preliminary, temporary version of a document that is
      intended to become an RFC.

      Deprecated Term: ISDs SHOULD NOT use this term; the Request for
      Comment term. The RFC series is
      archival in nature and does not have a "draft"
      category. consists only of documents in permanent
      form. A document that is intended to become an RFC usually needs
      to be published first as an "Internet-Draft" (RFC 2026). (See: Internet Draft, (Draft Standard under) Internet
      Standard).)
      "Draft Standard" under "Internet Standard".)

   $ Draft Standard
      (I) See: (secondary secondary definition under) Internet Standard. under "Internet Standard".

   $ DSA
      (N) See: Digital Signature Algorithm.

   $ DSS
      (N) See: Digital Signature Standard.

   $ dual control
      (I) A procedure that uses two or more entities (usually persons)
      operating in concert to protect a system resource, such that no
      single entity acting alone can access that resource. (See: no-lone
      zone, separation of duties, split knowledge.)

   $ dual signature
      (O) /SET/ A single digital signature that protects two separate
      messages by including the hash results for both sets in a single
      encrypted value. [SET2]

      Deprecated Term: Usage: ISDs SHOULD NOT use this term except when
      qualified as "SET(trademark) dual signature" with this definition.

      Tutorial: Generated by hashing each message separately,
      concatenating the two hash results, and then hashing that value
      and encrypting the result with the signer's private key. Done to
      reduce the number of encryption operations and to enable
      verification of data integrity without complete disclosure of the
      data.

   $ dual-use certificate
      (I)
      (O) A certificate that is intended for use with both digital
      signature and data encryption services. [SP32]

      Usage: An ISD ISDs that uses the use this term SHOULD state a definition for it by


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      identifying the intended uses of the certificate, because there
      are more than just these two. two uses mentioned in the NIST
      publication. A v3 X.509 public-key certificate may have a "key
      Usage" extension, which indicates the purposes for which the
      public key may be used. (See: certificate profile.)

   $ duty
      (I) An attribute of a role that obligates an entity playing the
      role to perform one or more tasks, which usually are essential for
      the functioning of the system. [Sand] (Compare authorization,
      privilege. See: role, billet.)



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   $ e-cash
      (D)
      (O) Electronic cash; money that is in the form of data and can be
      used as a payment mechanism on the Internet.

      Deprecated Usage: Many ISDs that use this term SHOULD state a
      definition for it because many different types of electronic cash
      have been devised, using devised with a variety of security mechanisms; therefore,
      ISDs that use the term SHOULD state a definition for it. mechanisms.

   $ EAP
      (I) See: Extensible Authentication Protocol.

   $ EAL
      (O) See: evaluation assurance level.

   $ Easter egg
      (D) "Hidden functionality within an application program, which
      becomes activated when an undocumented, and often convoluted, set
      of commands and keystrokes is entered. Easter eggs are typically
      used to display the credits for the development team and [are]
      intended to be non-threatening" [SP28], but Easter eggs have the
      potential to contain malicious code.

      Deprecated Usage: It is likely that other cultures have use different
      metaphors for this concept. Therefore, to ensure avoid international
      understanding,
      misunderstanding, ISDs SHOULD NOT use this term. (See: (Deprecated Deprecated
      Usage under) Green Book.) under "Green Book".)

   $ eavesdropping
      (I) Passive wiretapping done secretly, i.e., without the knowledge
      of the originator or the intended recipients of the communication.

   $ ECB
      (N) See: electronic codebook.

   $ ECDSA
      (N) See: Elliptic Curve Digital Signature Algorithm.

   $ economy of alternatives
      (I) The principle that a security mechanism should be designed to
      minimize the number of alternative ways of achieving a service.


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      (Compare: economy of mechanism.)

   $ economy of mechanism
      (I) The principle that a security mechanism should be designed to
      be as simple as possible, so that (a) the mechanism can be
      correctly implemented and (b) it can be verified that the
      operation of the mechanism enforces the system's security policy.
      (Compare: economy of alternatives, least privilege.)

   $ ECU
      (N) See: end cryptographic unit.



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   $ EDI
      (I) See: electronic data interchange.

   $ EDIFACT
      (N) See: (secondary secondary definition under) electronic under "electronic data interchange. interchange".

   $ EE
      (D) Abbreviation of "end entity" and other terms.

      Deprecated Term: Abbreviation: ISDs SHOULD NOT use this abbreviation;
      there could be confusion among "end entity", "end-to-end
      encryption", "escrowed encryption standard", and other terms.

   $ EES
      (O) See: Escrowed Encryption Standard.

   $ effective key length
      (O) "A measure of strength of a cryptographic algorithm,
      regardless of actual key length." [IATF]

   $ effectiveness
      (O) /ITSEC/ A property of a TOE representing how well it provides
      security in the context of its actual or proposed operational use.

   $ El Gamal algorithm
      (N) An algorithm for asymmetric cryptography, invented in 1985 by
      Taher El Gamal, that is based on the difficulty of calculating
      discrete logarithms and can be used for both encryption and
      digital signatures.

   $ electronic codebook (ECB)
      (N) An block cipher mode in which a plaintext block is used
      directly as input to the encryption algorithm and the resultant
      output block is used directly as cipher text [FP081]. (See: block
      cipher.)

   $ electronic commerce
      1. (I) Business conducted through paperless exchanges of
      information, using electronic data interchange, electronic funds
      transfer (EFT), electronic mail, computer bulletin boards,


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      facsimile, and other paperless technologies.

      2. (O) /SET/ "The exchange of goods and services for payment
      between the cardholder and merchant when some or all of the
      transaction is performed via electronic communication." [SET2]

   $ electronic data interchange (EDI)
      (I) Computer-to-computer exchange, between trading partners, of
      business data in standardized document formats.

      Tutorial: EDI formats have been standardized primarily by ANSI X12
      and by EDIFACT (EDI for Administration, Commerce, and
      Transportation), which is an international, UN-sponsored standard
      primarily used in Europe and Asia. X12 and EDIFACT are aligning to
      create a single, global EDI standard.


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   $ Electronic Key Management System (EKMS)
      (O) "Interoperable collection of systems developed by ... the U.S.
      Government to automate the planning, ordering, generating,
      distributing, storing, filling, using, and destroying of
      electronic keying material and the management of other types of
      COMSEC material." [C4009]

   $ electronic signature
      (D) Synonym for "digital signature" or "digitized signature".

      Deprecated Term: ISDs SHOULD NOT use this term; there is no
      current consensus on its definition. Instead, use "digital
      signature", if that is what was intended. (See: digitized
      signature.) intended

   $ electronic wallet
      (D) A secure container to hold, in digitized form, some sensitive
      data objects that belong to the owner, such as electronic money,
      authentication material, and various types of personal
      information.

      Deprecated Term: ISDs SHOULD NOT use this term; there term. There is no
      current consensus on its definition. Meanings range from "digital
      certificate" to "smartcard", definition; and some uses and definitions
      may be proprietary. Meanings range from virtual wallets
      implemented by data structures to physical wallets implemented by
      cryptographic tokens. (See: (Deprecated Deprecated Usage under) Green Book.) under "Green Book".)

   $ elliptic curve cryptography (ECC)
      (I) A type of asymmetric cryptography based on mathematics of
      groups that are defined by the points on a curve, where the curve
      is defined by a quadratic equation in a finite field. [Schn]

      Tutorial: The most efficient implementation of ECC is claimed to
      be stronger per bit of key (against cryptanalysis that uses a
      brute force attack) than any other known form of asymmetric
      cryptography. ECC is based on mathematics different than the kinds
      originally used to define the Diffie-Hellman algorithm and the


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      Digital Signature Algorithm, but ECC can be used to define an
      algorithm for key agreement that is an analog of Diffie-Hellman
      [A9063] and an algorithm for digital signature that is an analog
      of DSA [A9062]. (See: ECDSA.)

   $ Elliptic Curve Digital Signature Algorithm (ECDSA)
      (N) A standard [A9062] that is the analog, in elliptic curve
      cryptography, of the Digital Signature Algorithm.

   $ emanation
      (I) An signal (e.g., electromagnetic or acoustic) that is emitted
      by a system (e.g., through radiation or conductance) as a
      consequence (i.e., byproduct) of the system's operation, and that
      may contain information. (See: emanations security.)

   $ emanations security (EMSEC)
      (I) Physical security measures to protect against data compromise
      that could occur because of emanations that might be received and
      read by an unauthorized party. (See: emanation, TEMPEST.)

      Usage: Refers both to preventing or limiting emanations from a
      system and to preventing or limiting the ability of unauthorized


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      parties to receive the emissions.

   $ embedded cryptography
      (N) "Cryptography engineered into an equipment or system whose
      basic function is not cryptographic." [C4009]

   $ emergency plan
      (D) Synonym for "contingency plan".

      Deprecated Term: ISDs SHOULD NOT use this term. Instead, for
      neutrality and consistency of language, use "contingency plan".

   $ emergency response
      (O) An urgent response to a fire, flood, civil commotion, natural
      disaster, bomb threat, or other serious situation, with the intent
      of protecting lives, limiting damage to property, and minimizing
      disruption of system operations. [FP087] (See: availability,
      CERT.) CERT,
      emergency plan.)

   $ EMSEC
      (I) See: emanations security.

   $ EMV
      (N) An abbreviation Abbreviation of "Europay, MasterCard, Visa". Refers to a
      specification for smart cards that are used as payment cards, and
      for related terminals and applications. [EMV1, EMV2, EMV3]

   $ Encapsulating Security Payload (ESP)
      (I) An Internet protocol [R2406] designed to provide data
      confidentiality service and other security services for IP


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      datagrams. (See: IPsec. Compare: AH.)

      Tutorial: ESP may be used alone, or in combination with AH, or in
      a nested fashion with tunneling. Security services can be provided
      between a pair of communicating hosts, between a pair of
      communicating security gateways, or between a host and a gateway.
      The ESP header is encapsulated by the IP header, and the ESP
      header encapsulates either the upper layer protocol header
      (transport mode) or an IP header (tunnel mode). ESP can provide
      data confidentiality service, data origin authentication service,
      connectionless data integrity service, an anti-replay service, and
      limited traffic-flow confidentiality. The set of services depends
      on the placement of the implementation and on options selected
      when the security association is established.

   $ encipher
      (D) Synonym for "encrypt".

      Deprecated Definition: ISDs SHOULD NOT use this term as a synonym
      for "encrypt". However, see usage Usage note under "encryption".




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   $ encipherment
      (D) Synonym for "encryption".

      Deprecated Definition: ISDs SHOULD NOT use this term as a synonym
      for "encryption". However, see usage Usage note under "encryption".

   $ enclave
      1. (I) A set of system resources that operate in the same security
      domain and that share the protection of a common, continuous
      security perimeter. (Compare: domain.)

      2. (O) /U.S. Government/ "Collection of computing environments
      connected by one or more internal networks under the control of a
      single authority and security policy, including personnel and
      physical security." [C4009]

   $ encode
      1. (I) Use a system of symbols to represent information, which
      might originally have some other representation. Example: Morse
      code. (See: ASCII, BER.) (See: code, decode.)

      2. (D) Synonym for "encrypt".

      Deprecated Definition: ISDs SHOULD NOT use this term as a synonym
      for "encrypt"; encoding is not always meant to conceal meaning.

   $ encrypt
      (I) Cryptographically transform data to produce cipher text. (See:
      encryption. Compare: seal.)




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   $ encryption
      1. (I) Cryptographic transformation of data (called "plain text")
      into a different form (called "cipher text") that conceals the
      data's original meaning to prevent it and prevents the original form from being known or
      used. If the transformation is reversible, the corresponding
      reversal process is called "decryption", which is a transformation
      that restores encrypted data to its original state. (See:
      cryptography.)

      2. (O) "The cryptographic transformation of data to produce
      ciphertext." [I7498 Part 2]

      Usage: For this concept, ISDs SHOULD use the verb "to encrypt"
      (and related variations: encryption, decrypt, and decryption).
      However, because of cultural biases involving human burial, some
      international documents (particularly ISO and CCITT standards)
      avoid "to encrypt" and instead use the verb "to encipher" (and
      related variations: encipherment, decipher, decipherment).

      Tutorial: Usually, the plaintext input to an encryption operation
      is clear text. But in some cases, the plain text may be cipher
      text that was output from another encryption operation. (See:
      superencryption.)


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      Encryption and decryption involve a mathematical algorithm for
      transforming data. In addition to the data to be transformed, the
      algorithm has one or more inputs that are control parameters: (a)
      a key that varies the transformation and, in some cases, (b) an IV
      that establishes the starting state of the algorithm.

   $ encryption certificate
      (I) A public-key certificate that contains a public key that is
      intended to be used for decrypting data, rather than for verifying
      digital signatures or performing other cryptographic functions.

      Tutorial: A v3 X.509 public-key certificate may have a "keyUsage"
      extension that indicates the purpose for which the certified
      public key is intended. (See: certificate profile.)

   $ end cryptographic unit (ECU)
      1. (N) Final destination device into which a key is loaded for
      operational use.

      2. (N) A device that (a) performs cryptographic functions, (b)
      typically is part of a larger system for which the device provides
      security services, and (c), from the viewpoint of a supporting
      security infrastructure such as a key management system, is the
      lowest level of identifiable component with which a management
      transaction can be conducted

   $ end entity
      1. (I) A system entity that is the subject of a public-key


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      certificate and that is using, or is permitted and able to use,
      the matching private key only for purposes other than signing a
      digital certificate; i.e., an entity that is not a CA.

      2. (O) "A certificate subject which uses its public [sic] key for
      purposes other than signing certificates." [X509]

      Deprecated Definition: ISDs SHOULD NOT use the X.509 definition,
      which is misleading and incomplete. First, that definition should
      have said "private key" rather than "public key" because
      certificates are not usefully signed with a public key. Second,
      the X.509 definition is ambiguous regarding whether an end entity
      may or may not use the private key to sign a certificate, i.e.,
      whether the subject may be a CA. The intent of X.509's authors was
      that an end entity certificate is not valid for use in verifying a
      signature on an X.509 certificate or X.509 CRL. Thus, it would
      have been better for the X.509 definition to have said "only for
      purposes other than signing certificates".

      Usage: Despite the problems in the X.509 definition, the term
      itself is useful in describing applications of asymmetric
      cryptography. The way the term is used in X.509 implies that it
      was meant to be defined, as we have done here, relative to roles


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      that an entity (which is associated with an OSI end system) is
      playing or is permitted to play in applications of asymmetric
      cryptography other than the PKI that supports applications.

      Tutorial: Whether a subject can play both CA and non-CA roles,
      with either the same or different certificates, is a matter of
      policy. (See: CPS.) A v3 X.509 public-key certificate may have a
      "basicConstraints" extension containing a "cA" value that
      specifically "indicates whether or not the public key may be used
      to verify certificate signatures". (See: certificate profile.)

   $ end system
      (N) /OSIRM/ A computer that implements all seven layers of the
      OSIRM and may attach to a subnetwork. Usage: In the IPS context, a
      an end system is called a "host".

   $ end-to-end encryption
      (I) Continuous protection of data that flows between two points in
      a network, effected by encrypting data when it leaves its source,
      leaving
      keeping it encrypted while it passes through any intermediate
      computers (such as routers), and decrypting it only when the data it
      arrives at the intended final destination. (See: wiretapping.
      Compare: link encryption.)

      Examples: BLACKER, CANEWARE, IPLI, IPsec, PLI, SDNS, SILS.

      Tutorial: When two points are separated by multiple communication
      links that are connected by one or more intermediate relays, end-
      to-end encryption enables the source and destination systems to


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      protect their communications without depending on the intermediate
      systems to provide the protection.

   $ end user
      1. (I) /information system/ A system entity, usually a human
      individual, that makes use of system resources, primarily for
      application purposes as opposed to system management purposes.

      2. (D) /PKI/ Synonym for "end entity".

      Deprecated Definition: ISDs SHOULD NOT use "end user" as a synonym
      for "end entity", because that would mix concepts in a potentially
      misleading way.

   $ endorsed-for-unclassified cryptographic item (EUCI)
      (O) /U.S. Government/ "Unclassified cryptographic equipment that
      embodies a U.S. Government classified cryptographic logic and is
      endorsed by NSA for the protection of national security
      information." [C4009] (Compare: CCI, type 2 product.)

   $ entity
      See: system entity.



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   $ entrapment
      (I) "The deliberate planting of apparent flaws in a system for the
      purpose of detecting attempted penetrations or confusing an
      intruder about which flaws to exploit." [FP039] (See: honey pot.)

   $ entropy
      1. (I) An information-theoretic measure (usually stated as a
      number of bits) of the amount of uncertainty that an attacker
      faces to determine the value of a secret. [SP63] (See: strength.)

      Example: If a password is said to contain at least 20 bits of
      entropy, that means that it must be as hard to find the password
      as to guess an a 20-bit random number.

      2. (I) An information-theoretic measure (usually stated as a
      number of bits) of the amount of information in a message; i.e.,
      the minimum number of bits needed to encode all possible meanings
      of that message. [Schn] (See: uncertainty.)

   $ ephemeral
      (I) /adjective/ Refers to a cryptographic key or other
      cryptographic parameter or data object that is short-lived,
      temporary, or used one time. (See: session key. Compare: static.)

   $ erase
      (I) Delete magnetically stored data in such a way that the data is
      irretrievable by ordinary means, but might be recovered using
      laboratory methods. [C4009] (Compare: purge.)



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   $ error detection code
      (I) A checksum designed to detect, but not correct, accidental
      (i.e., unintentional) changes in data.

   $ Escrowed Encryption Standard (EES)
      (N) A U.S. Government standard [FP185] that specifies how to use of a
      symmetric encryption algorithm (SKIPJACK) and create a Law
      Enforcement Access Field (LEAF) creation method to implement for implementing part of a key
      escrow system that provides for enables decryption of telecommunications when
      interception is lawfully authorized.

      Tutorial: Both SKIPJACK and the LEAF are intended for use in
      equipment used to encrypt and decrypt sensitive, unclassified, sensitive
      telecommunications data.

   $ ESP
      (I) See: Encapsulating Security Payload.

   $ Estelle
      (N) A language (ISO 9074-1989) for formal specification of
      computer network protocols.




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   $ ETSI
      (N) See: European Telecommunication Standards Institute.

   $ EUCI
      (O) See: endorsed-for-unclassified cryptographic item.

   $ European Telecommunication Standards Institute (ETSI)
      (N) An independent, non-profit organization, based in France, that
      is officially recognized by the European Commission and
      responsible for standardization of information and communication
      technologies within Europe.

      Tutorial: ETSI is maintains the custodian of standards for a number of security
      algorithms, including encryption algorithms for mobile telephone
      systems in Europe.

   $ evaluated products list, Evaluated Products List
      1. (I) /not capitalized/ A list of information system equipment
      items that have been evaluated against, and found to be compliant
      with, a particular set of criteria.

      2. (N) /capitalized, U.S. Government/ The Evaluated Products List
      (http://www.radium.ncsc.mil/tpep/epl/) contains items that have
      been evaluated against the TCSEC by the NCSC, or against the
      Common Criteria by the NIAP or one of its partner agencies in
      another county. This List forms Chapter 4 of NSA's "Information
      Systems Security Products and Services Catalogue". [C4009]

   $ evaluated system
      (I) A system that has been evaluated against security criteria


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      such as the TCSEC or the Common Criteria.

   $ evaluation
      (I) Assessment of an information system against defined security
      criteria, such as the TCSEC or the Common Criteria. (Compare:
      certification.)

   $ evaluation assurance level (EAL)
      (N) A predefined package of assurance components that represents a
      point on the Common Criteria's scale for rating confidence in the
      security of information technology products and systems.

      Tutorial: The Common Criteria defines a scale of seven,
      hierarchically ordered EALs for rating a TOE. From highest to
      lowest, they are as follows:
      -  EAL7. Formally verified design and tested.
      -  EAL6. Semiformally verified design and tested.
      -  EAL5. Semiformally designed and tested.
      -  EAL4. Methodically designed, tested, and reviewed.
      -  EAL3. Methodically tested and checked.
      -  EAL2. Structurally tested.
      -  EAL1. Functionally tested.


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      An EAL is a consistent, baseline set of requirements. The increase
      in assurance from EAL to EAL is accomplished by substituting
      higher assurance components (i.e. criteria of increasing rigor,
      scope, or depth) from seven assurance classes: (a) configuration
      management, (b) delivery and operation, (c) development, (d)
      guidance documents, (e) life cycle support, (f) tests, and (g)
      vulnerability assessment.

      The EALs were developed with the goal of preserving concepts of
      assurance that were adopted from earlier criteria, so that results
      of previous evaluations would remain relevant. For example, EALs
      levels 2-7 are generally equivalent to the assurance portions of
      the TCSEC C2-A1 scale. However, this equivalency should be used
      with caution. The levels do not derive assurance in the same
      manner, and exact mappings do not exist.

   $ expire
      (I) See: certificate expiration.

   $ exposure
      (I) A type of threat action whereby sensitive data is directly
      released to an unauthorized entity. (See: unauthorized
      disclosure.)

      Usage: This type includes the following subtypes:
      -  "Deliberate Exposure": Intentional release of sensitive data to
         an unauthorized entity.
      -  "Scavenging": Searching through data residue in a system to
         gain unauthorized knowledge of sensitive data.


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      -  "Human error": In context of exposure, human action or inaction
         that unintentionally results in an entity gaining unauthorized
         knowledge of sensitive data. (Compare: corruption,
         incapacitation.)
      -  "Hardware or software error": In context of exposure, system
         failure that unintentionally results in an entity gaining
         unauthorized knowledge of sensitive data. (Compare: corruption,
         incapacitation.)

   $ Extended Security Option
      (I) See: (secondary secondary definition under) IPSO. under "IPSO".

   $ Extensible Authentication Protocol (EAP)
      (I) A extension framework for PPP that supports multiple, optional
      authentication mechanisms, including cleartext passwords,
      challenge-response, and arbitrary dialog sequences. [R3748]

      Tutorial: This protocol is intended for use primarily by a host or
      router that connects to a network server via switched circuits or
      dial-up lines. EAP typically runs directly over IPS data link
      protocols or OSIRM layer Layer 2 protocols, such as PPP or IEEE 802,
      without requiring IP.




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   $ Extensible Markup Language (XML)
      (N) A version of Standard Generalized Markup Language (ISO 8879),
      which separately represents both a document's content and its
      structure. XML was designed by W3C for use on the World Wide Web.

   $ extension
      (I) A data item defined for optional inclusion in a v3 X.509
      public-key certificate or a v2 X.509 CRL.

      Tutorial: The formats defined in X.509 can be extended to provide
      methods for associating additional attributes with subjects and
      public keys and for managing a certification hierarchy:
      - "Certificate  A "certificate extension": X.509 defines standard extensions
         that may be included in v3 certificates to provide additional
         key and security policy information, subject and issuer
         attributes, and certification path constraints.
      -  A "CRL extension": X.509 defines extensions that may be
         included in v2 CRLs to provide additional issuer key and name
         information, revocation reasons and constraints, and
         information about distribution points and delta CRLs.
      - "Private  A "private extension": Additional extensions, each named by an
         OID, can be locally defined as needed by applications or
         communities. (See: PKIX private Authority Information Access extension, SET
         private extensions.)

   $ external controls
      (I) /computer security/ Refers to administrative security,
      personnel security, and physical security. (Compare: internal
      controls.)


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   $ extranet
      (I) A computer network that an organization uses for application
      data traffic between the organization and its business partners.
      (Compare: intranet.)

      Tutorial: An extranet can be implemented securely, either on the
      Internet or using Internet technology, by constructing the
      extranet as a VPN.

   $ extraction resistance
      (O) Capability Ability of cryptographic equipment to resist efforts to
      extract keying material directly from the equipment (as opposed to
      gaining knowledge of keying material by cryptanalysis). [C4009]

   $ fail safe
      (I) A mode of system termination of system functions (when a failure
      occurs or is detected in the system) that automatically leaves
      system processes and components in a secure state when a failure occurs
      or is detected in the system. state.

   $ fail soft
      (I) Selective termination of affected affected, non-essential system
      functions and processes when a failure occurs or is detected in


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   $ failure control
      (I) A methodology used to provide fail-safe or fail-soft
      termination and recovery of functions and processes when failures
      occur or are detected in a system. system functions. [FP039]

   $ fairness
      (I) A property of an access protocol for a system resource whereby
      the resource is made equitably or impartially available to all
      eligible users. [R3753] (RFC 3753)

      Tutorial: Fairness can prevent flooding, be used to defend against some types of
      denial-of-service attacks on a system connected to a network.
      However, this technique assumes that the system can properly
      receive and process inputs from the network. Therefore, the
      technique can mitigate flooding but not is ineffective against
      jamming.

   $ falsification
      (I) A type of threat action whereby false data deceives an
      authorized entity. (See: active wiretapping, deception.)

      Usage: This type includes the following subtypes:
      -  "Substitution": Altering or replacing valid data with false
         data that serves to deceive an authorized entity.
      -  "Insertion": Introducing false data that serves to deceive an
         authorized entity.

   $ fault tree
      (I) A branching, hierarchical data structure that is used to


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      represent events and to determine the various combinations of
      component failures and human acts that could result in a specified
      undesirable system event. (See: attack tree, flaw hypothesis
      methodology.)

      Tutorial: "Fault-tree analysis" is a technique in which an
      undesired state of a system is specified and the system is studied
      in the context of its environment and operation to find all
      credible ways in which the event could occur. The specified fault
      event is represented as the root of the tree. The remainder of the
      tree represents AND or OR combinations of subevents, and
      sequential combinations of subevents, that could cause the root
      event to occur. The main purpose of a fault-tree analysis is to
      calculate the probability of the root event, using statistics or
      other analytical methods and incorporating actual or predicted
      quantitative reliability and maintainability data. When the root
      event is a security violation, and some of the subevents are
      deliberate acts intended to achieve the root event, then the fault
      tree is an attack tree.

   $ FEAL
      (O) A family of symmetric block ciphers that was developed in
      Japan; uses a 64-bit block, keys of either 64 or 128 bits, and a
      variable number of rounds; and has been successfully attacked by
      cryptanalysts. [Schn]



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   $ Federal Information Processing Standards (FIPS)
      (N) The Federal Information Processing Standards Publication (FIPS
      PUB) series issued by NIST as technical guidelines for U.S.
      Government procurements of information processing system equipment
      and services. [FP031, FP039, FP041, FP046, FP074, FP081, FP087,
      FP102, FP113, FP140, FP151, FP180, FP185, FP186, FP188, FP191,
      FP197]

      Tutorial: Issued under the provisions of section 111(d) of the
      Federal Property and Administrative Services Act of 1949 as
      amended by the Computer Security Act of 1987 (Public Law 100-235).

   $ Federal Public-key Infrastructure (FPKI)
      (O) A PKI being planned to establish facilities, specifications,
      and policies needed by the U.S. Government to use public-key
      certificates in systems involving unclassified but sensitive
      applications and interactions between Federal agencies as well as
      with entities of other branches of the Federal Government, state,
      and local governments, business, and the public. [FPKI]

   $ Federal Standard 1027
      (N) An U.S. Government document defining emanation, anti-tamper,
      security fault analysis, and manual key management criteria for
      DES encryption devices, primary for OSIRM layer Layer 2. Was renamed
      "FIPS PUB 140" when responsibility for protecting unclassified,
      sensitive information was transferred from NSA to NIST, and has


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      since been superseded by newer versions of that standard [FP140].

   $ File Transfer Protocol (FTP)
      (I) A TCP-based, application-level, Application-Layer, Internet Standard protocol
      (RFC 959) for moving data files from one computer to another.

   $ fill device
      (N) /COMSEC/ A device used to transfer or store keying material in
      electronic form or to insert keying material into cryptographic
      equipment.

   $ filter
      1. (I) /noun/ Synonym for "guard". (Compare: content filter,
      filtering router.)

      2. (I) /verb/ To process a flow of data and selectively block
      passage or permit passage of individual data items in accordance
      with a security policy.

   $ filtering router
      (I) An internetwork router that selectively prevents the passage
      of data packets according to a security policy. (See: guard.)

      Tutorial: A router usually has two or more physical connections to
      networks or other systems; and when the router receives a packet from a network and
      decides where to forward
      on one of those connections, it forwards the packet on a second network.
      connection. A filtering router does the same, same; but it first decides
      decides, according to some security policy, whether the packet
      should be forwarded at all, according to some security policy. all. The policy is implemented by rules
      (packet filters) loaded into the router. The rules mostly involve
      values of data packet control fields (especially IP source and
      destination addresses and TCP port


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      router may be used alone as a simple firewall or
      part be used as a
      component of a more complex firewall.

   $ financial institution
      (N) "An establishment responsible for facilitating customer-
      initiated transactions or transmission of funds for the extension
      of credit or the custody, loan, exchange, or issuance of money."
      [SET2]

   $ fingerprint
      1. (I) A pattern of curves formed by the ridges on a fingertip.
      (See: biometric authentication, authentication. Compare: thumbprint.)

      2. (O) PGP usage: (D) /PGP/ A hash result ("key fingerprint") used to
      authenticate a public key
      (key fingerprint) or other data. [PGP]

      Deprecated Definition: ISDs SHOULD NOT use this term with the
      specific PGP definition, and SHOULD NOT use this term as a synonym
      for "hash result" of *any* kind, because either kind. Either use would mix concepts in
      a potentially misleading way.


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   $ FIPS
      (N) See: Federal Information Processing Standards.

   $ FIPS PUB 140-1
      (N) The U.S. Government standard [FP140] for security requirements
      to be met by a cryptographic module when the module is used to
      protect unclassified information in computer and communication
      systems. (See: Common Criteria, FIPS, Federal Standard 1027.)

      Tutorial: The standard specifies four increasing levels (from
      "Level 1" to "Level 4") of requirements to cover a wide range of
      potential applications and environments. The requirements address
      basic design and documentation, module interfaces, authorized
      roles and services, physical security, software security,
      operating system security, key management, cryptographic
      algorithms, electromagnetic interference and electromagnetic
      compatibility (EMI/EMC), and self-testing. NIST and the Canadian
      Communication Security Establishment jointly certify modules.

   $ FIREFLY
      (O) /U.S. Government/ "Key management protocol based on public-key
      cryptography." [C4009]

   $ firewall
      1. (I) An internetwork gateway that restricts data communication
      traffic to and from one of the connected networks (the one said to
      be "inside" the firewall) and thus protects that network's system
      resources against threats from the other network (the one that is
      said to be "outside" the firewall). (See: guard, security
      gateway.)



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      2. (O) A device or system that controls the flow of traffic
      between networks using differing security postures. [SP41]

      Tutorial: A firewall typically protects a smaller, secure network
      (such as a corporate LAN, or even just one host) from a larger
      network (such as the Internet). The firewall is installed at the
      point where the networks connect, and the firewall applies
      security policy
      rules to control traffic that flows in and out of the protected
      network.

      A firewall is not always a single computer. For example, a
      firewall may consist of a pair of filtering routers and one or
      more proxy servers running on one or more bastion hosts, all
      connected to a small, dedicated LAN (see: DMZ) buffer zone) between the
      two routers. The external router blocks attacks that use IP to
      break security (IP address spoofing, source routing, packet
      fragments), while proxy servers block attacks that would exploit a
      vulnerability in a higher layer protocol or service. The internal
      router blocks traffic from leaving the protected network except
      through the proxy servers. The difficult part is defining criteria


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      by which packets are denied passage through the firewall, because
      a firewall not only needs to keep intruders unauthorized traffic (i.e.,
      intruders) out, but usually also needs to let authorized users traffic
      pass both in and out.

   $ firmware
      (I) Computer programs and data stored in hardware -- typically in
      read-only memory (ROM) or programmable read-only memory (PROM) --
      such that the programs and data cannot be dynamically written or
      modified during execution of the programs. (See: hardware,
      software.)

   $ FIRST
      (N) See: Forum of Incident Response and Security Teams.

   $ flaw
      (I) An error of commission, omission, or oversight in the design,
      implementation, or operation of an information system. A flaw may
      result in a vulnerability. (Compare: vulnerability.)

   $ flaw hypothesis methodology
      (I) An evaluation or attack technique in which specifications and
      documentation for a system are analyzed to hypothesize flaws in
      the system. The list of hypothetical flaws is prioritized on the
      basis of the estimated probability that a flaw exists and,
      assuming it does, on the ease of exploiting it and the extent of
      control or compromise it would provide. The prioritized list is
      used to direct a penetration test or attack against the system.
      [NCS04] (See: fault tree.) tree, flaw.)

   $ flooding
      1. (I) An attack that attempts to cause a failure in a system by
      providing more input than the system can process properly. (See:


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      denial of service, fairness. Compare: jamming.)

      Tutorial: Flooding uses "overload" as a type of "obstruction"
      intended to cause "disruption".

      2. (I) The process of delivering data or control messages to every
      node of a network. [R3753] (RFC 3753)

   $ flow analysis
      (I) An analysis performed on a nonprocedural formal nonprocedural, formal, system
      specification that locates potential flows of information between
      system variables. By assigning security levels to the variables,
      the analysis can find some types of covert channels. [Huff]

   $ flow control
      (I) A procedure or technique to ensure that information transfers
      within a system are not made from one security level to another
      security level, and especially not from a higher level to a lower
      level. [Denns] (See: covert channel, confinement property,


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      information flow policy, simple security property.)

   $ For Official Use Only (FOUO)
      (O) /U.S. DoD/ A U.S. Government designation for information that
      has not been given a security classification pursuant to the
      criteria of an Executive Order dealing with national security, but
      which may be withheld from the public because disclosure would
      cause a foreseeable harm to an interest protected by one of the
      exemptions stated in the Freedom of Information Act (Section 552
      of title 5, United States Code). (See: security label, security
      marking. Compare: classified.)

   $ formal
      (I) Expressed in a restricted syntax language with defined
      semantics based on well-established mathematical concepts. [CCIB]
      (Compare: informal, semiformal.)

   $ formal access approval
      (O) /U.S. Government/ Documented approval by a data owner to allow
      access to a particular category of information in a system. (See:
      category.)

   $ Formal Development Methodology
      (O) See: Ina Jo.

   $ formal model
      (I) A security model that is formal. Example: Bell-LaPadula model.
      [Land] (See: formal, security model.) [Land]

   $ formal proof
      (I) A complete and convincing mathematical argument presenting the
      full logical justification for each step in the proof of the truth
      of a theorem or set of theorems.

   $ formal specification
      (I) A specification of hardware or software functionality in a
      computer-readable language; usually a precise mathematical
      description of the behavior of the system with the aim of


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      providing a correctness proof. [Huff] (See: Affirm, Gypsy, HDM,
      Ina Jo.)

   $ formulary
      (I) A technique for enabling a decision to grant or deny access to
      be made dynamically at the time the access is attempted, rather
      than earlier when an access control list or ticket is created.

   $ FORTEZZA(trademark)
      (N)
      (O) A registered trademark of NSA, used for a family of
      interoperable security products that implement a NIST/NSA-approved
      suite of cryptographic algorithms for digital signature, hash,
      encryption, and key exchange. The products include a PC card (that
      contains a CAPSTONE chip), and compatible serial port modems,


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      server boards, and software implementations.

   $ Forum of Incident Response and Security Teams (FIRST)
      (N) An international consortium of CSIRTs (e.g., CIAC) that work
      together to handle computer security incidents and promote
      preventive activities. (See: CSIRT, security incident.)

      Tutorial: FIRST was founded in 1990 and, as of July 2004, had more
      than 100 members spanning the globe. Its mission includes:
      -  Provide members with technical information, tools, methods,
         assistance, and guidance.
      -  Coordinate proactive liaison activities and analytical support.
      -  Encourage development of quality products and services.
      -  Improve national and international information security for
         government, private industry, academia, and the individual.
      -  Enhance the image and status of the CSIRT community.

   $ forward secrecy
      See: public-key forward secrecy.

   $ FOUO
      (O) See: For Official Use Only.

   $ FPKI
      (O) See: Federal Public-Key Infrastructure.

   $ frequency hopping
      (N) "Repeated switching of frequencies during radio transmission
      according to a specified algorithm." [C4009] (See: spread
      spectrum.)

      Tutorial: Frequency hopping is a TRANSEC technique to minimize the
      potential for unauthorized interception or jamming.

   $ FTP
      (I) See: File Transfer Protocol.




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   $ gateway
      (I) An intermediate system (interface, relay) that attaches to two
      (or more) computer networks that have similar functions but
      dissimilar implementations and that enables inter-network
      communication. either one-way or two-
      way communication between the networks. (See: bridge, firewall,
      guard, internetwork, proxy server, router, and subnetwork.)

      Tutorial: The networks may differ in any of several aspects,
      including protocols and security mechanisms. When two computer
      networks differ in the protocol by which they offer service to
      hosts, a gateway may translate one protocol into the other or
      otherwise facilitate interoperation of hosts (see: Internet
      Protocol). In theory, gateways between computer networks are
      conceivable at any OSIRM layer. In practice, they usually operate
      at OSIRM layer Layer 2 (see: bridge), 3 (see: router), or 7 (see: proxy


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      server).

   $ GCA
      (O) See: geopolitical certificate authority.

   $ GDOI
      (O) See: Group Domain of Interpretation.

   $ GeldKarte
      (O) A smartcard-based smartcard-based, electronic money system that is maintained
      by the German banking industry, incorporates cryptography, and can
      be used to make payments via the Internet. (See: IOTP.)

   $ GeneralizedTime
      (N) The ASN.1 data type "GeneralizedTime" (ISO 8601) contains a
      calendar date (YYYYMMDD) and a time of day, which is either (a)
      the local time, (b) the Coordinated Universal Time, or (c) both
      the local time and an offset allowing that enables Coordinated Universal
      Time to be calculated. (See: Coordinated Universal Time, UTCTime.)

   $ Generic Security Service Application Program Interface (GSS-API)
      (I) An Internet Standard protocol [R2078] that specifies calling
      conventions by which an application (typically another
      communication protocol) can obtain authentication, integrity, and
      confidentiality security services independently of the underlying
      security mechanisms and technologies, thus allowing enabling the
      application source code to be ported to different environments.

      Tutorial: "A GSS-API caller accepts tokens provided to it by its
      local GSS-API implementation and transfers the tokens to a peer on
      a remote system; that peer passes the received tokens to its local
      GSS-API implementation for processing. The security services
      available through GSS-API in this fashion are implementable (and
      have been implemented) over a range of underlying mechanisms based
      on [symmetric] and [asymmetric cryptography]." [R2078]




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   $ geopolitical certificate authority (GCA)
      (O) /SET/ In a SET certification hierarchy, an optional level that
      is certified by a BCA and that may certify cardholder CAs,
      merchant CAs, and payment gateway CAs. Using GCAs enables a brand
      to distribute responsibility for managing certificates to
      geographic or political regions, so that brand policies can vary
      between regions as needed.

   $ GIG
      (O) See: Global Information Grid.

   $ Global Information Grid.
      (O) /U.S. DoD/ "A globally interconnected, end-to-end set of
      information capabilities, associated processes and personnel for
      collecting, processing, storing, disseminating, and managing
      information on demand to warfighters, policy makers, and support


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      personnel." [IATF] Usage: Formerly called the DII.

   $ granularity
      1. good engineering practice(s)
      (N) "Relative fineness A term used to which specify or characterize design, implementation,
      installation, or operating practices for an access control mechanism can
      be adjusted." [C4009]

      2. (O) "The size of the smallest protectable unit of information"
      in information system,
      when a more explicit specification is not possible. Generally
      understood to refer to the state of the engineering art for
      commercial systems that have problems and solutions equivalent to
      the system in question.

   $ granularity
      1. (N) "Relative fineness to which an access control mechanism can
      be adjusted." [C4009]

      2. (O) "The size of the smallest protectable unit of information"
      in a trusted computer system. [Huff]

   $ Green Book
      (D) /slang/ Synonym for "Defense Password Management Guideline"
      [CSC2].

      Deprecated Term: Except as an explanatory appositive, ISDs SHOULD
      NOT use this term, regardless of the associated definition.
      Instead, use the full proper name of the document or, in
      subsequent references, a conventional abbreviation. (See: Rainbow
      Series.)

      Deprecated Usage: To improve international comprehensibility of
      Internet Standards and the Internet Standards Process, ISDs SHOULD
      NOT use "cute" synonyms. No matter how clearly understood or
      popular a nickname may be in one community, it is likely to cause
      confusion or offense in others. For example, several other
      information system standards also are called "the Green Book". The Book"; the
      following are some examples:
      -  Each volume of 1992 ITU-T (known at that time as CCITT)
         standards.
      -  "PostScript Language Program Design", Adobe Systems, Addison-
         Wesley, 1988.
      -  IEEE 1003.1 POSIX Operating Systems Interface.
      -  "Smalltalk-80: Bits of History, Words of Advice", Glenn
         Krasner, Addison-Wesley, 1983.
      -  "X/Open Compatibility Guide".
      -  A particular CD-ROM format developed by Phillips.




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   $ GRIP
      (I) A contraction of "Guidelines and Recommendations for Security
      Incident Processing", the name of the IETF working group that
      seeks to facilitate consistent handling of security incidents in
      the Internet community. (See: security incident.)

      Tutorial: Guidelines to be produced by the WG will address
      technology vendors, network service providers, and response teams


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      in their roles assisting organizations in resolving security
      incidents. These relationships are functional and can exist within
      and across organizational boundaries.

   $ Group Domain of Interpretation (GDOI)
      (I) An ISAMKP/IKE domain of interpretation for group key
      management; i.e., a phase 2 protocol in ISAKMP. [R3547] (See:
      secure multicast.)

      Tutorial: In this group key management model that extends the
      ISAKMP standard, the protocol is run between a group member and a
      "group controller/key server", which establishes security
      associations [R2401] among authorized group members. The GDOI
      protocol is itself protected by an ISAKMP phase 1 association.

      For example, multicast applications may use ESP to protect their
      data traffic. GDOI carries the needed security association
      parameters for ESP. In this way, GDOI supports multicast ESP with
      group authentication of ESP packets using a shared, group key.

   $ group identity
      (I) See: (secondary secondary definition under) identity. under "identity".

   $ group security association
      (I) "A bundling of [security associations] (SAs) that together
      define how a group communicates securely. The [group SA] may
      include a registration protocol SA, a rekey protocol SA, and one
      or more data security protocol SAs." [R3740]

   $ GSS-API
      (I) See: Generic Security Service Application Program Interface.

   $ guard
      (I) A computer system that (a) acts as gateway between two
      information systems operating under different security policies
      and (b) is trusted to mediate information data transfers between
      the two systems. two. (See: controlled interface, domain.) domain, filter. Compare:
      firewall.)

      Usage: Frequently understood to mean that one system is operating
      at a higher security level than the other, and that the gateway's
      purpose is to prevent unauthorized disclosure of data from the
      higher system to the lower. However, the purpose might also be to
      protect the data integrity, availability, or general system
      integrity of one system from threats posed by connecting to the


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      other system. The mediation may be entirely automated or may
      involve reliable human review. (See: filter, firewall.)

   $ guest login
      (I) See: anonymous login.




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   $ GULS
      (I) Generic Upper Layer Security service element (ISO 11586), a
      five-part standard for the exchange of security information and
      security-transformation functions that protect confidentiality and
      integrity of application data.

   $ Gypsy verification environment
      (O) A methodology, language, and integrated set of software tools
      developed at the University of Texas for specifying, coding, and
      verifying software to produce correct and reliable programs.
      [Cheh]

   $ H field
      (D) See: Handling "Deprecated Usage" under "Handling Restrictions field. field".

   $ hack
      1a. (I) /verb/ To work on something, especially to program a
      computer. (See: hacker.)

      1b. (I) /verb/ To do some kind of mischief, especially to play a
      prank on, or penetrate, a system. (See: hacker, cracker.)

      2. (I) /noun/ An item of completed work or an instance of dealing
      with a problem, especially when that involves computer programming
      or other use of a computer.

   $ hacker
      1. (I) Someone with a strong interest in computers, who enjoys
      learning about them them, programming them, and experimenting and
      otherwise working with them. (See: hack. Compare: cracker.)

      Usage: The recommended This first definition is the original meaning of the term
      (circa 1960), which 1960); it then had a neutral or positive connotation of
      "someone who figures things out and makes something cool happen".

      2. (D) Synonym for "cracker".

      Deprecated Usage: Today, the term is frequently misused, especially misused
      (especially by
      journalists, to have the pejorative meaning of "cracker". journalists) with this second meaning.

   $ handle
      1. (I) /verb/ Perform processing operations on data, such as
      receive and transmit, collect and disseminate, create and delete,
      store and retrieve, read and write, and compare. (See: access.)

      2. (I) /noun/ An on-line pseudonym, particularly one used by a
      cracker; derived from citizens band radio culture.

   $ handling restriction
      (I) A type of access control other than (a) the rule-based
      protections of mandatory access control and (b) the identity-based
      protections of discretionary access control; usually procedural in
      nature. involves


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      administrative security.

   $ Handling Restrictions field
      (I) A 16-bit field (the "H field") that specifies a control and release marking in
      the security option (option type 130) of IP's datagram header
      format. The valid field values are alphanumeric digraphs assigned
      by the U.S. Government, as specified in RFC 791.

      Deprecated Abbreviation: ISDs SHOULD NOT use the abbreviation "H


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      field" because it is potentially ambiguous. Instead, use "Handling
      Restrictions field".

   $ handshake
      (I) Protocol dialogue between two systems for identifying and
      authenticating themselves to each other, or for synchronizing
      their operations with each other.

   $ Handshake Protocol
      (I) /TLS/ The TLS Handshake Protocol consists of three sub-
      protocols parts
      (i.e., subprotocols) that enable peer entities to agree upon
      security parameters for the record layer, authenticate themselves
      to each other, instantiate negotiated security parameters, and
      report error conditions to each other. [R2246]

   $ harden
      (I) To protect a system by configuring it to operate in a way that
      eliminates or mitigates known vulnerabilities. Example: [RSCG].
      (See: default account.)

   $ hardware
      (I) The material physical components of an information system.
      (See: firmware, software.)

   $ hardware token
      See: token.

   $ hash code
      (D) Synonym for "hash result" or "hash function".

      Deprecated Term: ISDs SHOULD NOT use this term (especially not as
      a synonym for "hash result" or "hash function"); the term term; it mixes concepts
      in a potentially misleading way. A hash result is not a "code",
      and a hash function does not "encode" in any sense defined by this
      glossary. (See: hash value, message digest.)

   $ hash function
      1. (I) A function H that maps an arbitrary, variable-length bit
      string, s, into a fixed-length string, h = H(s) (called the "hash
      result"). For most computing applications, it is desirable that
      given a string s with H(s) = h, any change to s that creates a
      different string s' will result in an unpredictable hash result
      H(s') that is, with high probability, not equal to H(s).



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      2. (O) "A (mathematical) function which maps values from a large
      (possibly very large) domain into a smaller range. A 'good' hash
      function is such that the results of applying the function to a
      (large) set of values in the domain will be evenly distributed
      (and apparently at random) over the range." [X509]

      Tutorial: A hash function operates on variable-length input (e.g.,
      a message or a file) and outputs a fixed-length output, which
      typically is much shorter than most input values. If the algorithm
      is "good" as described in the "O" definition, then the hash
      function may be a candidate for use in a security mechanism to
      detect


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      mechanism to detect changes made by active wiretapping (See: (discussion under)
      checksum).
      Tutorial under "checksum".)

      Security mechanisms require a "cryptographic hash function" (e.g.,
      MD2, MD4, MD5, SHA-1, Snefru), i.e., a good hash function that
      also has the one-way property and one of the two collision-free
      properties:
      -  "One-way property": Given H and a hash result h = H(s), it is
         hard (i.e., computationally infeasible) to find s. (Of course,
         given H and an input s, it must be relatively easy to compute
         the hash result H(s).)
      -  "Weakly collision-free property": Given H and an input s, it is
         hard to find a different input, s', such that H(s) = H(s').
      -  "Strongly collision-free property": Given H, it is hard to find
         any pair of inputs s and s' such that H(s) = H(s').

      If H produces a hash result N bits long, then to find an s' where
      H(s') = H(s) for a specific given s, the amount of computation
      required is O(2**n); i.e., it is necessary to try on the order of
      2 to the power n values of s' before finding a collision. However,
      to simply find any pair of values s and s' that collide, the
      amount of computation required is only O(2**(n/2)); i.e., after
      computing H(s) for 2 to the power n/2 randomly chosen values of s,
      the probability is greater than 1/2 that two of those values have
      the same hash result. (See: birthday attack.)

   $ hash result
      1. (I) The output of a hash function. (See: hash code, hash value.
      Compare: hash value.)

      Usage: The "I" definition is recommended to avoid the unusual
      usage of "message" that is seen in the following "O" definition.

      2. (O) "The output produced by a hash function upon processing a
      message" (where "message" is broadly defined as "a digital
      representation of data"). [ABA]

      Usage: ISDs SHOULD avoid the unusual usage of "message" that is
      seen in the "O" definition.

   $ hash value
      (D) Synonym for "hash result".



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      Deprecated Term: ISDs SHOULD NOT use this term; it term for the output of a
      hash function; the term could easily be confused with "hashed
      value", which is means the input to a hash function. (See: hash code,
      hash result, message digest.)

   $ HDM
      (O) See: Hierarchical Development Methodology.

   $ Hierarchical Development Methodology (HDM)
      (O) A methodology, language, and integrated set of software tools
      developed at SRI International for specifying, coding, and
      verifying software to produce correct and reliable programs.


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      [Cheh]

   $ hierarchical PKI
      (I) A PKI architecture based on a certification hierarchy.
      (Compare: mesh PKI, trust-file PKI.)

   $ hierarchy management
      (I) The process of generating configuration data and issuing
      public-key certificates to build and operate a certification
      hierarchy. (See: certificate management.)

   $ hierarchy of trust
      (D) Synonym for "certification hierarchy".

      Deprecated Term: ISDs SHOULD NOT use this term; it mixes concepts
      in a potentially misleading way. (See: certification hierarchy,
      trust, web of trust.)

   $ high-assurance guard
      (N)
      (O) "An oxymoron," said Lt. Gen. William H. Campbell, former U.S.
      Army chief information officer, speaking at an Armed Forces
      Communications and Electronics Association conference.

      Deprecated

      Usage: This term mixes concepts and could easily be
      misunderstood; therefore, ISDs that use this term SHOULD state a definition for it. it
      because the term mixes concepts and could easily be misunderstood.

   $ hijack attack
      (I) A form of active wiretapping in which the attacker seizes
      control of a previously established communication association.
      (See: man-in-the-middle attack, pagejacking, piggyback attack.)

   $ HIPAA
      (N) Health Information Portability and Accountability Act of 1996,
      a U.S. law (Public Law 104-191) that protects the privacy of
      patients' medical records and other health information in all
      forms, and mandates security for that information, including for
      its electronic storage and transmission.

   $ HMAC
      (I) A keyed hash [R2104] that can be based on any iterated


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      cryptographic hash (e.g., MD5 or SHA-1), so that the cryptographic
      strength of HMAC depends on the properties of the selected
      cryptographic hash. (See: [R2202, R2403, R2404].)

      Tutorial: Assume that H is a generic cryptographic hash in which a
      function is iterated on data blocks of length B bytes. L is the
      length of the of hash result of H. K is a secret key of length L
      <= K <= B. The values IPAD and OPAD are fixed strings used as
      inner and outer padding and defined as follows: IPAD = the byte
      0x36 repeated B times, and OPAD = the byte 0x5C repeated B times.
      HMAC is computed by H(K XOR OPAD, H(K XOR IPAD, inputdata)).


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      HMAC has the following goals:
      -  To use available cryptographic hash functions without
         modification, particularly functions that perform well in
         software and for which software is freely and widely available.
      -  To preserve the original performance of the selected hash
         without significant degradation.
      -  To use and handle keys in a simple way.
      -  To have a well-understood cryptographic analysis of the
         strength of the mechanism based on reasonable assumptions about
         the underlying hash function.
      -  To enable easy replacement of the hash function in case a
         faster or stronger hash is found or required.

   $ honey pot
      (D) A system (e.g., a web server) or a system resource (e.g., a file
      on a server), server) that is designed to be attractive to potential
      crackers and intruders, like honey is attractive to bears. (See:
      entrapment.)

      Deprecated Term: It is likely that other cultures have use different
      metaphors for this concept. Therefore, to ensure avoid international
      understanding,
      misunderstanding, ISDs SHOULD NOT use this term. (See: (Deprecated Deprecated
      Usage under) Green Book.) under "Green Book.")

   $ host
      1. (I) /general/ A computer that is attached to a communication
      subnetwork or internetwork and can use services provided by the
      network to exchange data with other attached systems. (See: end
      system. Compare: server.)

      2. (I) /IPS/ A networked computer that does not forward IP packets
      that are not addressed to the computer itself. (Compare: router.)

      Derivation: As viewed by its users, a host "entertains" them,
      providing application layer Application-Layer services or access to other computers
      attached to the network. However, even though some traditional
      peripheral service devices, such as printers, can now be
      independently connected to networks, they are not usually called
      hosts.



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   $ HTML
      (I) See: Hypertext Markup Language.

   $ HTTP
      (I) See: Hypertext Transfer Protocol.

   $ https
      (I) When used in the first part of a URL (the part that precedes
      the colon and specifies an access scheme or protocol), this term
      specifies the use of HTTP enhanced by a security mechanism, which
      is usually SSL. (Compare: S-HTTP.)


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   $ hybrid encryption
      (I) An application of cryptography that combines two or more
      encryption algorithms, particularly a combination of symmetric and
      asymmetric encryption. Examples: digital envelope, MSP, PEM, PGP.
      (Compare: superencryption.)

      Tutorial: Asymmetric algorithms require more computation than
      equivalently strong symmetric ones. Thus, asymmetric encryption is
      not normally used for data confidentiality except to distribute a
      symmetric keys key in a hybrid encryption scheme, where the symmetric
      key is usually very short (in terms of bits) compared to the data
      file it protects. (See: bulk key.)

   $ hyperlink
      (I) In hypertext or hypermedia, an information object (such as a
      word, a phrase, or an image; image, which usually is highlighted by color
      or underscoring) that points (indicates (i.e., indicates how to connect) to
      related information that is located elsewhere and can be retrieved
      by activating the link (e.g., by selecting the object with a mouse
      pointer and then clicking).

   $ hypermedia
      (I) A generalization of hypertext; any media that contain
      hyperlinks that point to material in the same or another data
      object.

   $ hypertext
      (I) A computer document, or part of a document, that contains
      hyperlinks to other documents; i.e., text that contains active
      pointers to other text. Usually written in HTML and accessed using
      a web browser. (See: hypermedia.)

   $ Hypertext Markup Language (HTML)
      (I) A platform-independent system of syntax and semantics (RFC
      1866) for adding characters to data files (particularly text
      files) to represent the data's structure and to point to related
      data, thus creating hypertext for use in the World Wide Web and
      other applications. (Compare: XML.)




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   $ Hypertext Transfer Protocol (HTTP)
      (I) An TCP-based, application-level, Application-Layer, client-server, Internet
      protocol (RFC 2616) that is used to carry data requests and
      responses in the World Wide Web. (See: hypertext.)

   $ IAB
      (I) See: Internet Architecture Board.

   $ IANA
      (I) See: Internet Assigned Numbers Authority.




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   $ IATF
      (O) See: Information Assurance Technical Framework.

   $ ICANN
      (I) See: Internet Corporation for Assigned Names and Numbers.

   $ ICMP
      (I) See: Internet Control Message Protocol.

   $ ICMP flood
      (I) A denial-of-service attack that sends a host more ICMP echo
      request ("ping") packets than the protocol implementation can
      handle. (See: flooding, smurf.)

   $ ICRL
      (N) See: indirect certificate revocation list.

   $ IDEA
      (N) See: International Data Encryption Algorithm.

   $ identification
      (I) An act or process that presents an identifier to a system so
      that the system can recognize a system entity and distinguish it
      from other entities. (See: authentication.)

   $ identification information
      (D) Synonym for either "identifier" or "authentication
      information". (See: authentication.)

      Deprecated Term: Definition: ISDs SHOULD NOT use this term; it duplicates the
      meaning term as a synonym
      for either of standardized terms those terms; that would be duplicative and mixes would mix
      concepts in a potentially misleading way. Instead, use
      "identifier" or "authentication information ", depending on what
      is meant.

   $ Identification Protocol
      (I) An client-server Internet protocol [R1413] for learning the
      identity of a user of a particular TCP connection.

      Tutorial: Given a TCP port number pair, the server returns a
      character string that identifies the owner of that connection on


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      the server's system. The protocol does not provide an
      authentication service and is not intended for authorization or
      access control; at control. At best, it provides additional auditing
      information with respect to TCP.

   $ identifier
      (I) A data object -- often, a printable, non-blank character
      string -- that definitively represents a specific identity of a
      system entity, distinguishing that identity from all others.
      (Compare: identity.)

   $ identifier credential
      1. (I) See: /authentication/ under "credential".

      2. (D) Synonym for "signature certificate".

      Usage: ISDs that use this term SHOULD state a definition for it
      because the term is used in many ways and could easily be
      misunderstood.

   $ identity
      (I) The collective aspect of a set of attribute values (i.e.,


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      characteristics) by which a system entity is recognizable or
      known, and which is sufficient to (1) distinguish the entity from
      all other entities in the system, system and also sufficient to (2) distinguish the identity
      from any other identities of the same entity. (See:
      authenticate. authenticate,
      registration. Compare: identifier.)

      Tutorial: When At the time when a user's identity is being registered
      in a system, the system may require presentation of evidence that
      proves both the user's eligibility to register and the identity's
      authenticity (i.e., that the user has the right to claim the
      identity).

      The set of attributes used for to recognize identities must, of
      course, be sufficient to uniquely represent each entity, i.e., to
      distinguish each entity from all others in the system. However, a
      PKI or other system may permit a subscriber to have two or more
      concurrent identities. (This is different from concurrently
      associating two different identifiers with the same identity, and
      also different from a single identity concurrently accessing the
      system in two different roles. (See: principal, role-based access
      control.)) Having two or more identities registered in a system
      for the same entity implies that the entity has two separate
      justifications for registration eligibility. In that case, the set
      of attributes used for identities must be able to uniquely
      represent multiple identities for a single entity.

      Tutorial: This

      An ISD may apply this term relates to some other basic security terms as
      shown in a user that is an individual entity
      or one that is a set. If an ISD involves both meanings, the ISD
      SHOULD use the following diagram: definitions to avoid ambiguity:
      -  "Singular identity": An identity that is registered for a user


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         that is exactly one person or one process.
      -  "Shared identity": An identity that is registered for a user
         that is a set of entities of which each member is authorized to
         assume the identity individually and for which the registering
         system maintains a record of the singular entities that
         comprise the set. In this case, we would expect each member
         entity to be registered with a singular identity.
      -  "Group identity": An identity that is registered for a user
         that is a set of entities for which the registering system does
         not maintain a record of the singular entities that comprise
         the set.

      The following diagram illustrates how this term relates to some
      other terms in a PKI system: authentication information,
      identifier, identifier credential, registration, registered user,
      subscriber, and user.

      Relationships:  === One-To-One, one-to-one, ==> One-To-Many, one-to-many, <=> Many-to-Many. many-to-many.
                  +- - - - - - - - - - - - - - - - - - - - - - - - - - +
                  |                      PKI System                    |
      + - - - - + | +------------------+   +-------------------------+ |
      |  User   |  User,  | | Subscriber, i.e. |Subscriber, i.e., |   |   Subscriber Identity of Subscriber  | |
      | +-----+ |
      |i.e., one| | | Registered User User, |   |    is system-unique     | |
      | |Human| of the  | | |(Is System-Unique)| |   (Is System-Unique) is system-unique |   | +---------------------+ | |Being| |
      |following| | | +--------------+ |   | +---------------------+ |     Subscriber      | | |
      | +-----+         | | | | User's Core core  | |   | |     Subscriber     Identity's      | | |
      |    ^ +-----+ |===| | Registration | |==>| |     Identity's      |  Registration data  | | |
      | |human| | | | | Data, data, i.e.,  | |   | |  Registration Data  | | |+-------------------+| | |
      | |being| | | | |  An Entity's an entity's  | |   | |+-------------------+| ||  same core data   || | |
      |    v +-----+ | | | |Distinguishing|========|  Same Core Data |distinguishing|========|for all Identities || | |
      | +-----+   or    | | | |  Attribute  attribute   | |   | ||For All Identities || of the same User  || | |
      | | Set | +-----+ | | | |   Values   values     | | +===|| Of The Same User  || +===|+-------------------+| | |
      | +-----+ |auto-| | | | +--------------+ | | | |+-------------------+| +---------------------+ | |
      |    ^ |mated| | | +------------------+ | | +---------------------+ | +------------|------------+ |
      | |pro- | | |         |    +=======+ +------------|------------+              |              |
      | |cess | | | +-------v----|----------------------|------------+ |
      |    v +-----+ | | | +----------v-----+ +----------v---+     +------------v----------+ | |
      | +-----+ | | |   or    | Authentication |<=>| Subscriber Identifier | | |Authentication|<===>|Identifier of Identity | | |Auto-| |
      |+-------+| | | | Information  |     |   (Is System Unique)  | |    is system-unique   | | |mated| |
      || a set || | | +----------------+ +--------------+     +-----------------------+ | |
      | |Pro- | |
      ||  of   || | |              Identity Identifier Credential that associates unit of  | |
      | |cess |
      || either|| | | |(Associates Authentication Info. and Identifier)| | Information with the Identifier | +-----+ |
      |+-------+| | +------------------------------------------------+ |
      + - - - - + + - - - - - - - - - - - - - - - - - - - - - - - - - -+

      An ISD may apply this term to

   $ identity-based security policy
      (I) "A security policy based on the identities and/or attributes
      of users, a user that is an individual entity group of users, or one that is a set. If an ISD involves both meanings, entities acting on behalf of the ISD
      SHOULD use the following definitions to avoid ambiguity:
       - "Singular identity": An identity that is registered for a user
         that is exactly one person or one process.
       - "Shared identity": An identity that is registered for a user
         that is a set of entities of which each member is authorized to
         assume the identity individually and for which the registering
         system maintains a record of the singular entities that
         comprise the set. In this case, we would expect each member
         entity to be registered with a singular identity.
       - "Group identity": An identity that is registered for a user
         that is a set of entities for which the registering system does
         not maintain a record of the singular entities that comprise
         the set.

   $ identity-based security policy
      (I) "A security policy based on the identities and/or attributes
      of users, a group of users, or entities acting on behalf of the
      users and
      users and the resources/objects being accessed." [I7498 Part 2]
      (See: rule-based security policy.)

   $ identity credential
      1. (I) See: ("authentication" context under) "credential".




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      2. (I) Synonym for "signature certificate.

      Usage: The term is used in many ways and could easily be
      misunderstood; therefore, ISDs that use this term SHOULD state a
      definition for it.     9 March 2005


   $ identity proofing
      (I) A process that vets and verifies the information that is used
      to establish the identity of a system entity. (See: registration.)

   $ IDS
      (I) See: intrusion detection system.

   $ IEEE
      (N) See: Institute of Electrical and Electronics Engineers, Inc.

   $ IEEE 802.10
      (N) An IEEE committee developing security standards for local area
      networks. (See: SILS.)

   $ IEEE P1363
      (N) An IEEE working group, Standard for Public-Key Cryptography,
      engaged in developing a comprehensive reference standard for
      asymmetric cryptography. Covers discrete logarithm (e.g., DSA),
      elliptic curve, and integer factorization (e.g., RSA); and covers
      key agreement, digital signature, and encryption.

   $ IESG
      (I) See: Internet Engineering Steering Group.

   $ IETF
      (I) See: Internet Engineering Task Force.

   $ IKE
      (I) See: IPsec Key Exchange.

   $ IMAP4
      (I) See: Internet Message Access Protocol, version 4.

   $ IMAP4 AUTHENTICATE
      (I) A IMAP4 "command" command (better described as a transaction type, or
      a protocol-within-a-protocol)
      subprotocol) by which an IMAP4 client optionally proposes a
      mechanism to an IMAP4 server to authenticate the client to the
      server and provide other security services. (See: POP3.)

      Tutorial: If the server accepts the proposal, the command is
      followed by performing a challenge-response authentication
      protocol and, optionally, negotiating a protection mechanism for
      subsequent POP3 interactions. The security mechanisms that are
      used by IMAP4 AUTHENTICATE -- including Kerberos, GSSAPI, and
      S/Key -- are described in [R1731].


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   $ in the clear
      (I) Not encrypted. (See: clear text.)

   $ Ina Jo
      (O) A methodology, language, and integrated set of software tools
      developed at the System Development Corporation for specifying,


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      coding, and verifying software to produce correct and reliable
      programs. Also known as Usage: a.k.a. the Formal Development Methodology. [Cheh]

   $ incapacitation
      (I) A type of threat action that prevents or interrupts system
      operation by disabling a system component. (See: disruption.)

      Usage: This type includes the following subtypes:
      -  "Malicious logic": In context of incapacitation, any hardware,
         firmware, or software (e.g., logic bomb) intentionally
         introduced into a system to destroy system functions or
         resources. (See: (main corruption, main entry for) malicious logic.) for "malicious logic",
         masquerade, misuse.)
      -  "Physical destruction": Deliberate destruction of a system
         component to interrupt or prevent system operation.
      -  "Human error": In context of incapacitation, action or inaction
         that unintentionally disables a system component. (See:
         corruption, exposure.)
      -  "Hardware or software error": In context of incapacitation,
         error that unintentionally causes failure of a system component
         and leads to disruption of system operation. (See: corruption,
         exposure.)
      -  "Natural disaster": In context of incapacitation, any "act of
         God" (e.g., fire, flood, earthquake, lightning, or wind) that
         disables a system component. [FP031 section 2]

   $ incident
      See: security incident.

   $ INCITS
      (N) See: (International "International Committee for Information Technology
      Standardization under) ANSI.
      Standardization" under "ANSI".

   $ indicator
      (N) An action -- either specific, generalized, or theoretical --
      that an adversary might be expected to take in preparation for an
      attack. [C4009] (See: attack sensing, warning, and response.)

   $ indirect certificate revocation list (ICRL)
      (N) In X.509, a CRL that may contain certificate revocation
      notifications for certificates issued by CAs other than the issuer
      (i.e., signer) of the ICRL.

   $ indistinguishability
      (I) An attribute of an encryption algorithm that is a
      formalization of the notion that the encryption of some string is
      indistinguishable from the encryption of an equal-length string of
      nonsense. (Compare: semantic security.)


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   $ inference
      1. (I) A type of threat action that reasons from characteristics
      or byproducts of communication and thereby indirectly accesses


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      sensitive data, but not necessarily the data contained in the
      communication. (See: traffic analysis, signal analysis.)

      2. (I) A type of threat action that indirectly gains unauthorized
      access to sensitive information in a database management system by
      correlating query responses with information that is already
      known.

   $ inference control
      (I) Protection of data confidentiality against inference attack.
      (See: traffic-flow confidentiality.)

      Tutorial: A database management system containing N records about
      individuals may be required to provide statistical summaries about
      subsets of the population, while not revealing sensitive
      information about a single individual. An attacker may try to
      obtain sensitive information about an individual by isolating a
      desired record at the intersection of a set of overlapping
      queries. A system can attempt to prevent this by restricting the
      size and overlap of query sets, distorting responses by rounding
      or otherwise perturbing database values, and limiting queries to
      random samples. However, these techniques may be impractical to
      implement or use, and no technique is totally effective. For
      example, restricting the minimum size of a query set -- that is,
      not responding to queries for which there are fewer than K or more
      than N-K records that satisfy the query -- usually cannot prevent
      unauthorized disclosure. An attacker can pad small query sets with
      extra records, and then remove the effect of the extra records.
      The formula for identifying the extra records is called the
      "tracker". [Denns]

   $ INFOCON
      (O) See: information operations condition

   $ informal
      (N) Expressed in natural language. [CCIB] (Compare: formal,
      semiformal.)

   $ information
      (I) Facts and ideas, which can be represented (encoded) as various
      forms of data.

   $ information assurance
      (N) /U.S. Government/ "Measures that protect and defend
      information and information systems by ensuring their availability
      integrity, authentication, confidentiality, and non-repudiation.
      These measures include providing for restoration of information
      systems by incorporating protection, detection, and reaction


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      capabilities." [C4009]

   $ Information Assurance Technical Framework (IATF)
      (O) A publicly available document [IATF], developed through a


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      collaborative effort by organizations in the U.S. Government and
      industry, and issued by NSA. Intended for security managers and
      system security engineers as a tutorial and reference document
      about security problems in information systems and networks, to
      improve awareness of tradeoffs among available technology
      solutions and of desired characteristics of security approaches
      for particular problems. (See: ISO 17799, [SP14].)

   $ information domain
      (O) See: (secondary secondary definition under) domain. under "domain".

   $ information domain security policy
      (O) See: (secondary secondary definition under) domain. under "domain".

   $ information flow policy
      (N) /formal model/ A triple consisting of a set of security
      levels (or their equivalent security labels), a binary operator
      that maps each pair of security levels into a security level, and
      a binary relation on the set that selects a set of pairs of levels
      such that information is permitted to flow from an object of the
      first level to an object of the second level. (See: flow control,
      lattice model.)

   $ information operations condition (INFOCON)
      (O) /U.S. DoD/ A comprehensive defense posture and response based
      on the status of information systems, military operations, and
      intelligence assessments of adversary capabilities and intent.
      (See: threat)

      Derivation: From DEFCON, i.e., defense condition.

      Tutorial: The U.S. DoD defines five INFOCON levels are: levels: NORMAL (normal
      activity), ALPHA (increased risk of attack), BRAVO (specific risk
      of attack), CHARLIE (limited attack), and DELTA (general attack).

   $ information security (INFOSEC)
      (N) Measures that implement and assure security services in
      information systems, including in computer systems (see: COMPUSEC)
      and in communication systems (see: COMSEC).

   $ information system
      (I) An organized assembly of computing and communication resources
      and procedures -- i.e., equipment and services, together with
      their supporting infrastructure, facilities, and personnel -- that
      collect, record, process, store, transport, retrieve, display,
      disseminate, or dispose of information to accomplish a specified
      set of functions. (See: system entity, system resource.)



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   $ Information Technology Security Evaluation Criteria (ITSEC)
      (N) A Standard [ITSEC] jointly developed by France, Germany, the
      Netherlands, and the United Kingdom for use in the European Union;
      accommodates a wider range of security assurance and functionality


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      combinations than the TCSEC. Superseded by the Common Criteria.

   $ INFOSEC
      (I) See: information security.

   $ ingress filtering
      (I) A method [R2267] [R2827] for countering attacks that use packets with
      false IP source addresses, by blocking such packets at the
      boundary between connected networks.

      Tutorial: Suppose network A of an internet service provider (ISP)
      includes a filtering router that is connected to customer network
      B, and an attacker in B at IP source address "foo" attempts to
      send packets with false source address "bar" into A. The false
      address may be either fixed or randomly changing, and it may
      either be unreachable or be a forged address that legitimately
      exists within either B or some other network C. In ingress
      filtering, the ISP's router blocks all inbound packet that arrive
      from B with a source address that is not within the range of
      legitimately advertised addresses for B. This method does not
      prevent all attacks that can originate from B, but the actual
      source of such attacks can be more easily traced because the
      originating network is known.

   $ initialization value (IV)
      (I) /cryptography/ An input parameter that sets the starting state
      of a cryptographic algorithm or mode.

      Usage: Sometimes called "initialization vector" or "message
      indicator", but ISDs SHOULD NOT use these synonyms because they
      mix concepts in potentially confusing ways.

      Tutorial: An IV can be used to synchronize one cryptographic
      process with another; e.g., CBC, CFB, and OFB use IVs. An IV also
      can be used to introduce cryptographic variance (see: salt) in
      addition to that provided by a key.

   $ initialization vector
      (D) /cryptographic function/ Synonym for "initialization value".

      Deprecated Term: For consistency, ISDs SHOULD NOT use this term in
      the context of cryptographic functions.

   $ insertion
      (I) /packet/ See: secondary definition under "stream integrity
      service".

   $ inside attack
      (I) See: (secondary secondary definition under) attack. under "attack". Compare: insider.) insider.

   $ insider
      1. (I) A user (usually a person) that accesses a system from a


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      position that is inside the system's security perimeter. (Compare:
      authorized user, outsider, unauthorized user.)

      Tutorial: An insider has been assigned a role that has more
      privileges to access system resources than do some other types of
      users, or can access those resources without being constrained by
      some access controls that are applied to outside users. For
      example, a salesclerk is an insider who has access to the cash
      register, but a store customer is an outsider.

      The actions performed by an insider in accessing the system may be
      either authorized or unauthorized; i.e., an insider may act either
      as an authorized user or as an unauthorized user.

      2. (O) A person with authorized physical access to the system.
      Example: In this sense, an office janitor is an insider, but a
      burglar or casual visitor is not. [NRC98]

      3. (O) A person with an organizational status that causes the
      system or members of the organization to view access requests as
      being authorized. Example: In this sense, a purchasing agent is an
      insider but a vendor is not. [NRC98]

   $ inspectable space
      (O) /EMSEC/ "Three-dimensional space surrounding equipment that
      process classified and/or sensitive information within which
      TEMPEST exploitation is not considered practical or where legal
      authority to identify and/or remove a potential TEMPEST
      exploitation exists." [C4009]

   $ Institute of Electrical and Electronics Engineers, Inc. (IEEE)
      (N) The IEEE is a not-for-profit association of approximately
      300,000 individual members in 150 countries. The IEEE produces
      nearly one third of the world's published literature in electrical
      engineering, computers, and control technology; holds hundreds of
      major, annual conferences; and maintains more than 800 active
      standards, with many more under development. (See: SILS.)

   $ integrity
      See: data integrity, datagram integrity service, correctness
      integrity, source integrity, stream integrity service, system
      integrity.

   $ integrity check
      (D) A computation that is part of a mechanism to provide data
      integrity service or data origin authentication service. (Compare:
      checksum.)

      Deprecated Term: ISDs SHOULD NOT use this term as a synonym for
      "cryptographic hash" or "protected checksum. This term
      unnecessarily duplicates the meaning of other, well-established
      terms; this term only mentions integrity, even though the intended


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      service may be data origin authentication; and not every checksum


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      is cryptographically protected.

   $ integrity label
      (I) A security label that tells the degree of confidence that may
      be placed in the data, and may also tell what countermeasures are
      required to be applied to protect the data against from alteration
      and destruction. (See: integrity. Compare: classification label.)

   $ intelligent threat
      (I) A circumstance in which an adversary has the technical and
      operational capability ability to detect and exploit a vulnerability and also
      has the demonstrated, presumed, or inferred intent to do so. (See:
      threat.)

   $ interception
      (I) A type of threat action whereby an unauthorized entity
      directly accesses sensitive data while the data is traveling
      between authorized sources and destinations. (See: unauthorized
      disclosure.)

      Usage: This type includes the following subtypes:
      -  "Theft": Gaining access to sensitive data by stealing a
         shipment of a physical medium, such as a magnetic tape or disk,
         that holds the data.
      -  "Wiretapping (passive)": Monitoring and recording data that is
         flowing between two points in a communication system. (See:
         wiretapping.)
      -  "Emanations analysis": Gaining direct knowledge of communicated
         data by monitoring and resolving a signal that is emitted by a
         system and that contains the data but is was not intended to
         communicate the data. (See: emanation.)

   $ interference
      (I) /threat action/ See: (secondary secondary definition under) obstruction. under "obstruction".

   $ intermediate CA
      (D) The CA that issues a cross-certificate to another CA. [X509]
      (See: cross-certification.)

      Deprecated Term: ISDs SHOULD NOT use this term because it is not
      widely known and mixes concepts in a potentially misleading way.
      For example, suppose that end entity 1 ("EE1) is in one PKI
      ("PKI1"), end entity 2 ("EE2) is in another PKI ("PKI2"), and the
      root in PKI1 ("CA1") cross-certifies the root CA in PKI2 ("CA2").
      Then if EE1 constructs the certification path CA1-to-CA2-to-EE2 to
      validate a certificate of EE2, conventional English usage would
      describe CA2 as being in the "intermediate" position in that path,
      not CA1.

   $ internal controls
      (I) /computer security/ Functions, features, and technical
      characteristics of computer hardware and software, especially of


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      characteristics of computer hardware and software, especially of
      operating systems. Includes mechanisms to regulate the operation
      of a computer system with regard to access control, flow control,
      and inference control. (Compare: external controls.)

   $ International Data Encryption Algorithm (IDEA)
      (N) A patented, symmetric block cipher that uses a 128-bit key and
      operates on 64-bit blocks. [Schn] (See: symmetric cryptography.)

   $ International Standard
      (N) See: (secondary secondary definition under) ISO. under "ISO".

   $ International Traffic in Arms Regulations (ITAR)
      (O) Rules issued by the U.S. State Department, by authority of the
      Arms Export Control Act (22 U.S.C. 2778), to control export and
      import of defense articles and defense services, including
      information security systems, such as cryptographic systems, and
      TEMPEST suppression technology. (See: type 1 product, Wassenaar
      Arrangement.)

   $ internet, Internet
      1. (I) /not capitalized/ The term "internet" is a popular short
      synonym for Abbreviation of "internetwork".

      2. (I) /capitalized/ "The Internet" The Internet is the single, interconnected,
      worldwide system of commercial, government, educational, and other
      computer networks that share (a) the protocol suite specified by
      the IAB [R2026] (RFC 2026) and (b) the name and address spaces managed by
      the ICANN.

      Tutorial: The set of protocols (See: Internet Layer, Internet Protocol Suite.)

      Usage: Use with definite article "the" when using as a noun. E.g.,
      say "My LAN is called small, but the "Internet Protocol
      Suite" (IPS). It also Internet is popularly known as "TCP/IP", because TCP
      and IP are two of its most important protocols. The IPS makes it
      possible for users of any one large." Don't say "My
      LAN is small, but Internet is large."

   $ Internet Architecture Board (IAB)
      (I) A technical advisory group of the networks in ISOC, chartered by the Internet ISOC
      Trustees to
      communicate with, or use services located on, any of the other
      networks.

      Although the Internet does have architectural principles
      (described in RFC 1958), no Internet Standard defines a layered
      reference model for the IPS that is similar to the OSIRM. However,
      Internet community documents do refer (inconsistently) to layers:
      application, socket, transport, internetwork, network, data link,
      and physical.

      Usage: In this Glossary, Internet protocol layers are referred to
      by name to avoid confusing them with OSIRM layers, which are
      referred to by number. (See: OSI.)

   $ Internet Architecture Board (IAB)
      (I) A technical advisory group of the ISOC, chartered by the ISOC
      Trustees to provide oversight provide oversight of Internet architecture and
      protocols and, in the context of Internet Standards, a body to
      which decisions of the IESG may be appealed. Responsible for
      approving appointments to the IESG from among nominees submitted


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      by the IETF nominating committee. [R2026] (RFC 2026)

   $ Internet Assigned Numbers Authority (IANA)
      (I) From the early days of the Internet, the IANA was chartered by
      the ISOC and the U.S. Government's Federal Network Council to be
      the central coordination, allocation, and registration body for
      parameters for Internet protocols. Superseded by ICANN.

   $ Internet Control Message Protocol (ICMP)
      (I) An Internet Standard protocol (RFC 792) that is used to report
      error conditions during IP datagram processing and to exchange
      other information concerning the state of the IP network.



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   $ Internet Corporation for Assigned Names and Numbers (ICANN)
      (I) The non-profit, private corporation that has assumed
      responsibility for the IP address space allocation, protocol
      parameter assignment, DNS management, and root server system
      management functions formerly performed under U.S. Government
      contract by IANA and other entities.

      Tutorial: The IPS, as defined by the IETF and the IESG, contains
      numerous parameters, such as internet addresses, domain names,
      autonomous system numbers, protocol numbers, port numbers,
      management information base OIDs, including private enterprise
      numbers, and many others. The Internet community requires that the
      values used in these parameter fields be assigned uniquely. ICANN
      makes those assignments as requested and maintains a registry of
      the current values.

      ICANN was formed in October 1998, by a coalition of the Internet's
      business, technical, and academic communities. The U.S. Government
      designated ICANN to serve as the global consensus entity with
      responsibility for coordinating four key functions for the
      Internet: the allocation of IP address space, the assignment of protocol
      parameters, and the management of the DNS DNS, and management of the DNS root
      server system.

   $ Internet Draft Internet-Draft
      (I) A working document of the IETF, its areas, and its working
      groups. (Other groups may also distribute working documents (RFC 2026)

      Usage: The term is customarily hyphenated when used either as
      Internet Drafts.) a
      adjective or a noun, even though the latter is not standard
      English punctuation.

      Tutorial: An Internet Draft Internet-Draft is not an archival document like an
      RFC is. Instead, an Internet Draft Internet-Draft is a preliminary or working
      document that is valid for a maximum of six months and may be
      updated, replaced, or made obsolete by other documents at any
      time. It is inappropriate to use an Internet Draft as reference
      material or to cite it other than as "work in progress". Although
      most of the Internet-Drafts are produced by the IETF, any
      interested organization may request to have its working documents
      published as Internet-Drafts.

   $ Internet Engineering Steering Group (IESG)
      (I) The part of the ISOC responsible for technical management of
      IETF activities and administration of the Internet Standards
      Process according to procedures approved by the ISOC Trustees.
      Directly responsible for actions along the "standards track",


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      including final approval of specifications as Internet Standards.
      Composed of IETF Area Directors and the IETF chairperson, who also
      chairs the IESG. [R2026] (RFC 2026)




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   $ Internet Engineering Task Force (IETF)
      (I) A self-organized group of people who make contributions to the
      development of Internet technology. The principal body engaged in
      developing Internet Standards, although not itself a part of the
      ISOC. Composed of Working Groups, which are arranged into Areas
      (such as the Security Area), each coordinated by one or more Area
      Directors. Nominations to the IAB and the IESG are made by a
      committee selected at random from regular IETF meeting attendees
      who have volunteered. [R2026, R2323] (RFC 2026) [RFC 2323]

   $ Internet Layer
      (I) See: Internet Protocol Suite.

   $ Internet Message Access Protocol, version 4 (IMAP4)
      (I) An Internet protocol (RFC 2060) by which a client workstation
      can dynamically access a mailbox on a server host to manipulate
      and retrieve mail messages that the server has received and is
      holding for the client. (See: POP3.)

      Tutorial: IMAP4 has mechanisms for optionally authenticating a
      client to a server and providing other security services. (See:
      IMAP4 AUTHENTICATE.)

   $ Internet Open Trading Protocol (IOTP)
      (I) An Internet protocol (RFC 2801) proposed as a general
      framework for Internet commerce, able to encapsulate transactions
      of various proprietary payment systems (e.g., GeldKarte, Mondex,
      SET, VisaCash). Provides optional security services by
      incorporating various Internet security mechanisms (e.g., MD5) and
      protocols (e.g., TLS).

   $ Internet Policy Registration Authority (IPRA)
      (I) An X.509-compliant CA that is the top CA of the Internet
      certification hierarchy operated under the auspices of the ISOC
      [R1422]. (See: (PEM usage under) certification hierarchy.) /PEM/ under "certification hierarchy".)

   $ Internet Private Line Interface (IPLI)
      (I)
      (O) A successor to the PLI, updated to use TCP/IP and newer
      military-grade COMSEC equipment (TSEC/KG-84). The IPLI was a
      portable, modular system that was developed for use in tactical,
      packet-radio networks.

   $ Internet Protocol (IP)
      (I) A Internet Standard Standard, Internet-Layer protocol (version 4 is specified in RFC
      791, and version 6 in RFC 2460) that moves
      datagrams (discrete sets of bits) from one computer to another
      across an internetwork but does not provide reliable delivery,
      flow control, sequencing, or other end-to-end services that TCP
      provides. IP version 4 (IPv4) is specified in RFC 791, and IP
      version 6 (IPv6) is specified in RFC 2460. (See: IP address,
      TCP/IP.)

      Tutorial: In the OSIRM, If IP were used in an OSIRM stack, IP would be located placed at the top of layer 3.


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      the top of Layer 3, above other Layer 3 protocols in the stack.

      In any IPS stack, IP is always present in the Internet Layer and
      is always placed at the top of that layer, on top of any other
      protocols that are used in that layer. In some sense, IP is the
      only protocol specified for the IPS Internet Layer; other
      protocols used there, such as AH and ESP, are just IP variations.

   $ Internet Protocol security
      See: IPsec.

   $ Internet Protocol Security Option (IPSO)
      (I) Refers to one of three types of IP security options, which are
      fields that may be added to an IP datagram for the purpose of
      carrying security information about the datagram. (Compare:
      IPsec.)

      Deprecated Usage: ISDs SHOULD NOT use this term without a modifier
      to indicate which of the following three types is meant.
      -  "DoD Basic Security Option" (IP option type 130): Defined for
         use on U.S. DoD common-use data networks. Identifies the DoD
         classification level at which the datagram is to be protected
         and the protection authorities whose rules apply to the
         datagram. (A "protection authority" is a National Access
         Program (e.g., GENSER, SIOP-ESI, SCI, NSA, Department of
         Energy) or Special Access Program that specifies protection
         rules for transmission and processing of the information
         contained in the datagram.) [R1108]
      -  "DoD Extended Security Option" (IP option type 133): Permits
         additional security labeling information, beyond that present
         in the Basic Security Option, to be supplied in the datagram to
         meet the needs of registered authorities. [R1108]
      -  "Common IP Security Option" (CIPSO) (IP option type 134):
         Designed by TSIG to carry hierarchic and non-hierarchic
         security labels. (Formerly called "Commercial IP Security
         Option"; a version 2.3 draft was published 9 Mar March 1993 as an
         Internet-Draft but did not advance to RFC form.) [CIPSO]

   $ Internet Protocol Suite (IPS)
      (I) See: (secondary definition under) Internet.

   $ Internet Security Association The set of network communication protocols that are specified
      by the IETF, and Key Management Protocol (ISAKMP)
      (I) An approved as Internet IPsec protocol [R2408] to negotiate, establish,
      modify, and delete security associations, and to exchange key
      generation and authentication data, independent of Standards by the details IESG,
      within the oversight of
      any specific key generation technique, key establishment protocol,
      encryption algorithm, or authentication mechanism.

      Tutorial: ISAKMP supports negotiation the IAB. (See: OSIRM Security
      Architecture. Compare: OSIRM.)

      Usage: This set of security associations for protocols at all TCP/IP layers. By centralizing management of
      security associations, ISAKMP reduces duplicated functionality
      within each protocol. ISAKMP can also reduce connection setup
      time, by negotiating a whole stack of services at once. Strong
      authentication is required on ISAKMP exchanges, popularly known as "TCP/IP"
      because TCP and a digital
      signature algorithm based on asymmetric cryptography is used
      within ISAKMP's authentication component.

      ISAKMP includes two "phases" of negotiation: the phase 1
      negotiation establishes a IP are its most basic security association and important components.

      For clarity, this Glossary refers to be used IPS protocol layers by name
      and capitalizes those names, and refers to OSIRM protocol layers
      by number.

      Tutorial: The IPS does have architectural principles [R1958], but


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      for ISAKMP operations. Then, protected by the phase 1 association,
      phase 2 negotiations are used to establish security associations
      for other protocols, such as ESP.

   $ Internet Society (ISOC)
      (I) A professional society concerned with Internet development
      (including technical     9 March 2005


      there is no Internet Standards); with how Standard that defines a layered IPS reference
      model like the OSIRM. Still, Internet is
      and can be used; and with social, political, and technical issues
      that result. The ISOC Board of Trustees approves appointments community literature has
      referred (inconsistently) to IPS layers since early in the IAB from among nominees submitted by the IETF nominating
      committee. [R2026]

   $ Internet Standard
      (I) A specification, approved by
      Internet's development [Padl].

      This Glossary treats the IESG and published IPS as an RFC,
      that is stable and well-understood, is technically competent, has
      multiple, independent, and interoperable implementations with
      substantial operational experience, enjoys significant public
      support, having five protocol layers --
      Application, Transport, Internet, Network Interface, and is recognizably useful Network
      Hardware (or Network Substrate) -- which are illustrated in some or all parts of the
      Internet. [R2026] (See: RFC.)

      Tutorial:
      following diagram:

      OSIRM Layers       Examples          IPS Layers     Examples
      ------------------ ---------------  --------------- --------------
      Message Format:    P2   [X420]      Message Format: ARPA (RFC 822)
      +----------------+                  +-------------+
      |7.Application   | P1   [X419]      | Application | SMTP (RFC 821)
      +----------------+ -  -  -  -  -  - |             |
      |6.Presentatation|      [I8823]     |             |
      +----------------+ -  -  -  -  -  - |             |
      |5.Session       |      [I8327]     +-------------+
      +----------------+ -  -  -  -  -  - |  Transport  | TCP  (RFC 793)
      |4.Transport     | TP4  [I8073]     |             |
      +----------------+ -  -  -  -  -  - +-------------+
      |3.Network       | CLNP [I8473]     |  Internet   | IP   (RFC 791)
      |                |                  +-------------+
      |                |                  |   Network   | IP over IEEE
      +----------------+ -  -  -  -  -  - |  Interface  | 802 (RFC 1042)
      |2.Data Link     |                  +-------------+
      |                | LLC  [I8802-2]   -   Network   - The "Internet Standards Process" is an activity of the
      ISOC and is organized and managed by the IAB and the IESG. IPS does
      |                | MAC  [I8802-3]   -  Hardware   - not include
      +----------------+                  - (or Network - standards for
      |1.Physical      | Baseband         -  Substrate) - this layer.
      +----------------+ Signaling [Stal] + - - - - - - +

      The
      process is concerned diagram approximates how the five IPS layers align with all protocols, procedures, and
      conventions used in or by the Internet, whether or not they are
      part
      seven OSIRM layers, and it offers examples of the IPS. protocol stacks that
      provide roughly equivalent electronic mail service over a private
      local area network that uses baseband signaling.

      -  IPS Application Layer: The "Internet Standards Track" has three levels
      of increasing maturity: Proposed Standard, Draft Standard, and
      Standard. (Compare: ISO, W3C.)

   $ Internet Standards document (ISD)
      (I) An RFC or user runs an Internet-Draft that is produced as part of the
      Internet Standards Process [R2026]. (See: Internet Standard.)

      Deprecated Usage: Neither the term nor application program.
         The program selects the abbreviation is widely
      accepted; therefore, ISDs that use this term SHOULD state data transport service it needs --
         either a
      definition for it.

   $ internetwork
      (I) A system sequence of interconnected networks; data messages or a network continuous stream of networks.
      Usually shortened to "internet". (See: internet.)

      Tutorial: An internet is usually built using OSIRM layer 3
      gateways
         data -- and hands application data to connect a set of subnetworks. When the subnetworks
      differ in the Transport Layer for
         delivery.

      -  IPS Transport Layer: This layer 3 protocol service they provide, the gateways
      sometimes implement divides application data into
         packets, adds a uniform internetwork protocol (e.g., IP)
      that operates at the top of layer 3 destination address to each, and hides the underlying
      heterogeneity communicates
         them end-to-end -- from hosts that use communication services provided
      by the internet. (See: router.)

   $ intranet
      (I) A computer network, especially one based on Internet
      technology, that an organization uses for its own internal, application program to another --
         optionally regulating the flow and
      usually private, purposes ensuring reliable (error-
         free and that is closed to outsiders. (See: sequenced) delivery.

      -  IPS Internet Layer: This layer carries transport packets in IP
         datagrams. It moves each datagram independently, from its


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      extranet, virtual private network.)

   $ intruder
      (I) An entity that gains or attempts to gain access to a system or
      system resource without having authorization to do so. (See:
      intrusion. Compare: adversary, cracker.)

   $ intrusion
      1. (I) A security event, or a combination of multiple security
      events, that constitutes a security incident in which an intruder
      gains, or attempts to gain, access     9 March 2005


         source computer to its addressed destination computer, routing
         the datagram through a system or system resource
      without having authorization to do so. (See: IDS.)

      2. (I) A type sequence of threat action whereby an unauthorized entity
      gains access to sensitive data by circumventing networks and relays and
         selecting appropriate network interfaces en route.

      -  IPS Network Interface Layer: This layer accepts datagrams for
         transmission over a system's
      security protections. (See: unauthorized disclosure.)

      Usage: specific network. This type includes the following subtypes: layer specifies
         interface conventions for carrying IP over OSIRM Layer 3
         protocols and over Media Access Control sublayer protocols of
         OSIRM Layer 2. An example is IP over IEEE 802 (RFD 1042).

      - "Trespass": Gaining  IPS Network Hardware Layer: This layer consists of specific,
         physical access to sensitive data by
         circumventing a system's protections.
       - "Penetration": Gaining logical access to sensitive data communication media. However, the IPS does not specify
         its own peer-to-peer protocols in this layer. Instead, the
         layering conventions specified by
         circumventing a system's protections.
       - "Reverse engineering": Acquiring sensitive data the Network Interface Layer
         use Layer 2 and Layer 3 protocols that are specified by
         disassembling bodies
         other than the IETF. That it, the IPS addresses *inter*-network
         functions and analyzing does not address *intra*-network functions.

      The two models are most dissimilar in the design of a system component. upper layers, where the
      IPS model does not include Session and Presentation layers.
      However, this omission causes fewer functional differences between
      the models than might be imagined, and the differences have
      relatively few security implications:

      - "Cryptanalysis": Transforming encrypted data into plain text
         without having prior knowledge  Formal separation of encryption parameters or
         processes. (See: (main Glossary entry for) cryptanalysis.)

   $ intrusion detection
      (I) Sensing OSIRM Layers 5, 6, and analyzing system events for 7 is not needed in
         implementations; the purpose functions of
      noticing (i.e., becoming aware of) attempts to access system
      resources these layers sometimes are
         mixed in a single software unit, even in protocols in an unauthorized manner. (See: anomaly detection, IDS,
      misuse detection.) [IDSAN, IDSSC, IDSSE, IDSSY]

      Usage: This includes the following subtypes: OSI
         suite.

      - "Active detection": Real-time or near-real-time analysis of
         system event data to detect current intrusions, which result in
         an immediate protective response.
       - "Passive detection": Off-line analysis of audit data to detect
         past intrusions, which  Some OSIRM Layer 5 services -- for example, connection
         termination -- are reported to built into TCP, and the system security
         officer for corrective action. (Compare: remaining Layer 5
         and 6 functions are built into IPS Application-Layer protocols
         where needed.

      -  The OSIRM does not place any security audit.)

   $ intrusion detection system (IDS)
      1. (N) A process or subsystem, implemented services in software or
      hardware, that automates the tasks Layer 5 (see:
         OSIRM Security Architecture).

      -  The lack of (a) monitoring events that
      occur an explicit Presentation Layer in the IPS sometimes
         makes it simpler to implement security in IPS applications. For
         example, a computer network and (b) analyzing them for signs primary function of
      security problems. [SP31] (See: intrusion detection.)

      2. (N) A security alarm system Layer 6 is to detect unauthorized entry.
      [DC6/9].

      Tutorial: Active intrusion detection processes can be either host-


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      based or network-based:
       - "Host-based": Intrusion detection components -- traffic sensors convert data
         between internal and analyzers -- run directly on the hosts that they are
         intended external forms, using a transfer syntax to protect.
       - "Network-based": Sensors are placed on subnetwork components,
         and analysis components run either on subnetwork components or
         hosts.

   $ invalidity date
      (N) An X.509 CRL entry extension that "indicates the date at which
      it is known or suspected that the [revoked certificate's private
      key] was compromised or that
         unambiguously encode data for transmission. If an OSIRM
         application encrypts data to protect against disclosure during
         transmission, the certificate should otherwise be
      considered invalid." [X509].

      Tutorial: This date may transfer encoding must be earlier than done before the revocation date
         encryption. If an application does encryption, as is done in the
      CRL entry,
         OSI message handling and may even directory service protocols, then
         Layer 6 functions must be earlier than the date of issue of
      earlier CRLs. However, the invalidity date is not, by itself,
      sufficient for purposes of non-repudiation service. For example,
      to fraudulently repudiate a validly-generated signature, a private
      key holder may falsely claim that the key was compromised at some
      time replicated in Layer 7. [X400, X500].

      The two models are most alike at the past.

   $ IOTP
      (I) See: Internet Open Trading Protocol.

   $ IP
      (I) See: Internet Protocol.

   $ IP address
      (I) A computer's internetwork address that is assigned for use by
      IP and other protocols.

      Tutorial: An IP version 4 address (RFC 791) is written as a series top of four 8-bit numbers separated by periods. For example, OSIRM Layer 3, where
      the
      address of OSI Connectionless Network Layer Protocol (CLNP) and the host named "rosslyn.bbn.com" is 192.1.7.10.

      An IPS
      IP version 6 address (RFC 2373) is written as x:x:x:x:x:x:x:x,
      where each "x" is the hexadecimal value of one of are quite similar. Connection-oriented security services
      offered in OSIRM Layer 3 are inapplicable in the eight 16-bit
      parts of IPS, because the address. For example, 1080:0:0:0:8:800:200C:417A and
      FEDC:BA98:7654:3210:FEDC:BA98:7654:3210.

   $ IP Security Option
      (I) See: Internet Protocol Security Option.

   $ IPLI
      (I) See: Internet Private Line Interface.

   $ IPRA
      (I) See: Internet Policy Registration Authority.

   $ IPS
      (I) See: Internet Protocol Suite.


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      IPS Internet Layer lacks the explicit, connection-oriented service
      offered in the OSIRM.

   $ IPsec
      1a. Internet Security Association and Key Management Protocol (ISAKMP)
      (I) A contraction An Internet IPsec protocol [R2408] to negotiate, establish,
      modify, and delete security associations, and to exchange key
      generation and authentication data, independent of "Internet Protocol security", the name details of
      the IETF working group that is specifying an architecture [R2401]
      and set
      any specific key generation technique, key establishment protocol,
      encryption algorithm, or authentication mechanism.

      Tutorial: ISAKMP supports negotiation of protocols to provide security services for IP traffic.
      (See: AH, ESP, IKE, SAD, SPD. Compare: IPSO.)

      1b. (I) A collective name associations for that IP
      protocols at all IPS layers. By centralizing management of
      security architecture and
      associated set associations, ISAKMP reduces duplicated functionality
      within each protocol. ISAKMP can also reduce connection setup
      time, by negotiating a whole stack of protocols.

      Usage: Note that the letters "sec" services at once. Strong
      authentication is required on ISAKMP exchanges, and a digital
      signature algorithm based on asymmetric cryptography is used
      within ISAKMP's authentication component.

      ISAKMP negotiations are conducted in lower case in "IPsec".

      Tutorial: The two "phases":
      -  "Phase 1 negotiation". A phase 1 negotiation establishes a
         security services provided association to be used by ISAKMP to protect its own
         protocol operations.
      -  "Phase 2 negotiation". A phase 2 negotiation (which is
         protected by IPsec include access
      control service, connectionless data integrity service, data
      origin authentication service, protection against replays
      (detection of the arrival of duplicate datagrams, within a
      constrained window), data confidentiality service, and limited
      traffic-flow confidentiality. IPsec specifies (a) security
      protocols (AH and ESP), (b) association that was established by a
         phase 1 negotiation) establishes a security associations (what they are,
      how they work, how they are managed, and associated processing),
      (c) key management (IKE), and (d) algorithms for authentication
      and encryption. Implementation association to be
         used to protect the operations of IPsec is optional for IP version
      4, but mandatory for IP version 6.

   $ IPsec Key Exchange (IKE)
      (I) An Internet, IPsec, key-establishment a protocol [R2409] for
      putting in place authenticated keying material (a) for use with
      ISAKMP and (b) for other security associations, than ISAKMP,
         such as in AH and ESP.

      Tutorial: IKE is based on three earlier protocol designs: ISAKMP,
      OAKLEY, and SKEME.

   $ IPSO
      (I) See: Internet Protocol Security Option.

   $ ISAKMP Society (ISOC)
      (I) See: A professional society concerned with Internet Security Association development
      (including technical Internet Standards); with how the Internet is
      and Key Management
      Protocol. can be used; and with social, political, and technical issues
      that result. The ISOC Board of Trustees approves appointments to
      the IAB from among nominees submitted by the IETF nominating
      committee. (RFC 2026)

   $ ISD
      (I) See: Internet Standards document.

   $ ISO Standard
      (I) International Organization for Standardization, a voluntary,
      non-treaty, non-government organization, established in 1947, with
      voting members A specification, approved by the IESG and published as an RFC,
      that are designated standards bodies of
      participating nations is stable and non-voting observer organizations.
      (Compare: ANSI, IETF, ITU-T, W3C.)

      Tutorial: Legally, ISO well-understood, is a Swiss, non-profit, private
      organization. ISO technically competent, has
      multiple, independent, and interoperable implementations with
      substantial operational experience, enjoys significant public
      support, and is recognizably useful in some or all parts of the IEC (the International Electrotechnical


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      Commission) form the specialized system for worldwide
      standardization. National bodies that are members
      Internet. (RFC 2026) (Compare: RFC.)

      Tutorial: The "Internet Standards Process" is an activity of ISO or IEC
      participate in developing international standards through ISO the
      ISOC and
      IEC technical committees that deal with particular fields of
      activity. Other international governmental is organized and non-governmental
      organizations, in liaison with ISO managed by the IAB and IEC, also take part. (ANSI
      is the U.S. voting member of ISO. ISO IESG. The
      process is a class D member concerned with all protocols, procedures, and
      conventions used in or by the Internet, whether or not they are
      part of
      ITU-T.) the IPS. The ISO standards development process "Internet Standards Track" has four three levels
      of increasing maturity: Working Draft (WD), Committee Draft (CD), Proposed Standard, Draft International Standard (DIS), Standard, and International Standard
      (IS).
      Standard. (Compare: (standards track levels under) ISO, W3C.)


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      In information technology, ISO and IEC have a joint technical
      committee, ISO/IEC JTC 1. DISs adopted by JTC 1 are circulated to
      national bodies for voting, and publication as an IS requires
      approval by at least 75% of the national bodies casting a vote. Security Glossary, Version 2     9 March 2005



   $ ISO 17799
      (N) Internet Standards document (ISD)
      (I) An International Standard RFC or an Internet-Draft that is a code of practice, derived
      from Part 1 produced as part of British Standard 7799, for managing the security of
      information systems in an organization. This standard does not
      provide definitive or specific material on any security topic. It
      provides general guidance on a wide variety of topics, but
      typically does not go into depth. (See: IATF, [SP14].)

   $ ISOC
      (I) See:
      Internet Society.

   $ issue (a digital certificate or CRL)
      (I) Generate and sign a digital certificate (or CRL) and, usually,
      distribute it and make it available to potential certificate users
      (or CRL users). Standards Process (RFC 2026). (See: certificate creation.) Internet Standard.)

      Deprecated Usage: The ABA Guidelines [ABA] explicitly limit ISDs that use this term to
      certificate creation, and exclude the act of publishing. In
      general usage, however, "issuing" SHOULD state a digital certificate (or CRL)
      includes not only certificate creation but also making it
      available to potential users, such as by storing
      definition for it in a
      repository or other directory or otherwise publishing it. because neither the term nor the abbreviation is
      widely accepted.

   $ issuer
      1. internetwork
      (I) /certificate, CRL/ The CA that signs A system of interconnected networks; a digital certificate
      or CRL. network of networks.
      Usually shortened to "internet". (See: internet, Internet.)

      Tutorial: An X.509 certificate always includes internet can be built using OSIRM Layer 3 gateways to
      implement connections between a set of similar subnetworks. With
      dissimilar subnetworks, i.e., subnetworks that differ in the issuer's name.
      The name may include Layer
      3 protocol service they offer, an internet can be built by
      implementing a common name value.

      2. (O) /payment card, SET/ "The financial institution or its agent uniform internetwork protocol (e.g., IP) that issues
      operates at the unique primary account number to top of Layer 3 and hides the cardholder
      for underlying
      subnetworks' heterogeneity from hosts that use communication
      services provided by the payment card brand." [SET2]



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      Tutorial: The institution internet. (See: router.)

   $ intranet
      (I) A computer network, especially one based on Internet
      technology, that establishes the account for a
      cardholder and issues the payment card also guarantees payment an organization uses for
      authorized transactions that use the card in accordance with card
      brand regulations its own internal (and
      usually private) purposes and local legislation. [SET1]

   $ ITAR
      (O) See: International Traffic in Arms Regulations.

   $ ITSEC
      (N) See: Information Technology System Evaluation Criteria.

   $ ITU-T
      (N) International Telecommunications Union, Telecommunication
      Standardization Sector (formerly "CCITT"), a United Nations treaty
      organization that is composed mainly of postal, telephone, and
      telegraph authorities of the member countries and that publishes
      standards called "Recommendations". closed to outsiders. (See: X.400, X.500.)

      Tutorial: The Department of State represents the United States.
      ITU-T works on many kinds of communication systems. ITU-T
      cooperates with ISO on communication protocol standards, and many
      Recommendations in that area are also published as an ISO standard
      with an ISO name and number.

   $ IV
      (I) See: initialization value.
      extranet, virtual private network.)

   $ jamming intruder
      (I) An attack entity that gains or attempts to interfere with the reception of
      broadcast communications. gain access to a system or
      system resource without having authorization to do so. (See: anti-jam, denial of service.
      intrusion. Compare: flooding.)

      Tutorial: Jamming uses "interference" as adversary, cracker.)

   $ intrusion
      1. (I) A security event, or a type combination of "obstruction"
      intended multiple security
      events, that constitutes a security incident in which an intruder
      gains, or attempts to gain, access to cause "disruption". Jamming a broadcast signal is
      typically done system or system resource
      without having authorization to do so. (See: IDS.)

      2. (I) A type of threat action whereby an unauthorized entity
      gains access to sensitive data by broadcasting circumventing a second signal that receivers
      cannot separate from system's
      security protections. (See: unauthorized disclosure.)

      Usage: This type includes the first one. Jamming is mainly thought of
      in following subtypes:
      -  "Trespass": Gaining physical access to sensitive data by
         circumventing a system's protections.
      -  "Penetration": Gaining logical access to sensitive data by
         circumventing a system's protections.
      -  "Reverse engineering": Acquiring sensitive data by
         disassembling and analyzing the context design of wireless communication, but also can be done in
      some wired technologies, such as LANs that use contention
      techniques to share a broadcast medium.

   $ KAK
      (D) See: key-auto-key. (Compare: KEK.)

   $ KDC
      (I) See: Key Distribution Center.

   $ KEA
      (N) See: Key Exchange Algorithm.

   $ KEK
      (I) See: key-encrypting key. (Compare: KAK.) system component.
      -  "Cryptanalysis": Transforming encrypted data into plain text
         without having prior knowledge of encryption parameters or


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         processes. (See: main entry for "cryptanalysis".)

   $ Kerberos
      (N) A intrusion detection
      (I) Sensing and analyzing system developed at events for the Massachusetts Institute purpose of
      Technology that depends on passwords and symmetric cryptography
      (DES)
      noticing (i.e., becoming aware of) attempts to implement ticket-based, peer entity authentication
      service and access control service distributed in a client-server
      network environment. [R1510, Stei]

      Tutorial: Kerberos was developed by Project Athena and is named
      for the three-headed dog guarding Hades. The system architecture
      includes servers that function as
      resources in an ACC and a KDC.

   $ kernel
      (I) A small, trusted part of a system that provides services on
      which unauthorized manner. (See: anomaly detection, IDS,
      misuse detection.) [IDSAN, IDSSC, IDSSE, IDSSY]

      Usage: This includes the other parts following subtypes:
      -  "Active detection": Real-time or near-real-time analysis of
         system event data to detect current intrusions, which result in
         an immediate protective response.
      -  "Passive detection": Off-line analysis of audit data to detect
         past intrusions, which are reported to the system depend. (See: security
      kernel.)
         officer for corrective action. (Compare: security audit.)

   $ Kernelized Secure Operating System (KSOS)
      (O) An MLS computer operating system, designed to be intrusion detection system (IDS)
      1. (N) A process or subsystem, implemented in software or
      hardware, that automates the tasks of (a) monitoring events that
      occur in a provably
      secure replacement for UNIX Version 6, computer network and consisting (b) analyzing them for signs of a
      security kernel, non-kernel security-related utility programs, and
      optional UNIX application development and support environments.
      [Perr] problems. [SP31] (See: intrusion detection.)

      2. (N) A security alarm system to detect unauthorized entry.
      [DC6/9].

      Tutorial: KSOS-6 was the implementation on a SCOMP. KSOS-11 was
      the implementation by Ford Aerospace Active intrusion detection processes can be either host-
      based or network-based:
      -  "Host-based": Intrusion detection components -- traffic sensors
         and Communications
      Corporation analyzers -- run directly on the DEC PDP-11/45 hosts that they are
         intended to protect.
      -  "Network-based": Sensors are placed on subnetwork components,
         and PDP-111/70 computers. analysis components run either on subnetwork components or
         hosts.

   $ key
      1. (I) /cryptography/ An input parameter used to vary a
      transformation function performed by a cryptographic algorithm.
      (Compare: initialization value.)

      2. (I) /anti-jam/ invalidity date
      (N) An input parameter used to vary a process X.509 CRL entry extension that
      determines patterns for an anti-jam measure. (See: frequency
      hopping, spread spectrum.)

      Tutorial: A key "indicates the date at which
      it is usually specified as a sequence of bits known or
      other symbols. If a key value needs to be kept secret, suspected that the
      sequence of symbols [revoked certificate's private
      key] was compromised or that comprise it the certificate should otherwise be random, or at least
      pseudorandom, because that makes
      considered invalid." [X509].

      Tutorial: This date may be earlier than the key hard revocation date in the
      CRL entry, and may even be earlier than the date of issue of
      earlier CRLs. However, the invalidity date is not, by itself,
      sufficient for an adversary purposes of non-repudiation service. For example,
      to
      guess. (See: cryptanalysis, brute force attack.)

   $ key agreement (algorithm or protocol)
      1. (I) A key establishment method (especially one involving
      asymmetric cryptography) by which two or more entities, without
      prior arrangement except fraudulently repudiate a public exchange of data (such as public
      keys), each can generate the same key value. That is, the method
      does not send validly generated signature, a secret from one entity to the other (compare: private
      key
      transport); instead, both entities, without prior arrangement
      except a public exchange of data, can compute the same secret
      value, but holder may falsely claim that value cannot be computed by other, unauthorized
      entities. (See: Diffie-Hellman, the key establishment, KEA, MQV.) was compromised at some
      time in the past.

   $ IOTP
      (I) See: Internet Open Trading Protocol.




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      2. (O) "A method for negotiating a key value on line without
      transferring the key, even in an encrypted form, e.g., the Diffie-
      Hellman technique." [X509]

      3. (O) "The procedure whereby two different parties generate
      shared symmetric keys such     9 March 2005


   $ IP
      (I) See: Internet Protocol.

   $ IP address
      (I) A computer's internetwork address that any of the shared symmetric keys is assigned for use by
      IP and other protocols.

      Tutorial: An IP version 4 address (RFC 791) has four 8-bit parts
      and is written as a function series of the information contributed four decimal numbers separated by all legitimate
      participants, so that no party [alone] can predetermine the value
      periods. Example: The address of the key." [A9042]

      Example: A message originator host named "rosslyn.bbn.com"
      is 192.1.7.10.

      An IP version 6 address (RFC 2373) has eight 16-bit parts and the intended recipient can each
      use their own private key is
      written as eight hexadecimal numbers separated by colons.
      Examples: 1080:0:0:0:8:800:200C:417A and the other's public key with the
      Diffie-Hellman algorithm to first compute a shared secret value
      and, from that value, derive a session key to encrypt the message.
      FEDC:BA98:7654:3210:FEDC:BA98:7654:3210.

   $ key authentication
      (N) "The assurance IP Security Option
      (I) See: Internet Protocol Security Option.

   $ IP Security Protocol (IPsec)
      1a. (I) The name of the legitimate participants in a key
      agreement IETF working group that no non-legitimate party possesses the shared
      symmetric key." [A9042]

   $ key-auto-key (KAK)
      (D) "Cryptographic logic using previous key is specifying an
      architecture [R2401] and set of protocols to produce key."
      [C4009, A1523] provide security
      services for IP traffic. (See: CTAK.)

      Deprecated Term: IDS should not use this term; it is neither well-
      known nor precisely defined. Instead, use terms AH, ESP, IKE, SAD, SPD. Compare:
      IPSO.)

      1b. (I) A collective name for the IP security architecture and
      associated with
      modes set of protocols (primarily AH, ESP, and IKE).

      Usage: Note that the letters "sec" are defined in standards, such as CBC, CFB, and OFB.

   $ key center
      (I) A centralized key distribution process (used in symmetric
      cryptography), usually a separate computer system, that uses
      master keys (i.e., KEKs) to encrypt and distribute session keys
      needed lower case in a community of users. "IPsec".

      Tutorial: An ANSI standard [A9017] defines two types The security services provided by IPsec include access
      control service, connectionless data integrity service, data
      origin authentication service, protection against replays
      (detection of key
      center: key distribution center and key translation center.

   $ key confirmation
      (N) "The assurance [provided to] the legitimate participants in arrival of duplicate datagrams, within a
      key establishment protocol that the [parties that
      constrained window), data confidentiality service, and limited
      traffic-flow confidentiality. IPsec specifies (a) security
      protocols (AH and ESP), (b) security associations (what they are,
      how they work, how they are intended to
      share] the symmetric managed, and associated processing),
      (c) key actually possess the shared symmetric
      key." [A9042] management (IKE), and (d) algorithms for authentication
      and encryption. Implementation of IPsec is optional for IP version
      4, but mandatory for IP version 6.

   $ key distribution IPLI
      (I) A process that delivers a cryptographic key from the location
      where it is generated to the locations where it is used in a
      cryptographic algorithm. (See: key management.) See: Internet Private Line Interface.

   $ key distribution center (KDC)
      1. IPRA
      (I) A type of key center (used in symmetric cryptography) that
      implements a key distribution protocol to provide keys (usually, See: Internet Policy Registration Authority.

   $ IPS
      (I) See: Internet Protocol Suite.



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