INTERNET-DRAFT R. W. Shirey Obsoletes: RFC 2828 (if approved) BBN Technologies Expiration Date: 20 February 2004 20 August 2004 Internet Security Glossary, Version 2 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 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). All Rights Reserved. Abstract This Glossary has 1,500 entries that give definitions, abbreviations, and explanations for terminology concerning information system security. It makes recommendations to improve the clarity of Internet Standards documents (ISDs) and the ease with which international readers can understand ISDs. Its 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. Shirey Informational [Page 1] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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 . . . . . . . . . . . . . . . . . . . . . 6 3.1 Type "I": Recommended Definition with Internet Basis . . . 6 3.2 Type "N": Recommended Definition with Non-Internet Basis . 7 3.3 Type "O": Other Definitions. . . . . . . . . . . . . . . . 7 2.4 Type "D": Deprecated Definitions . . . . . . . . . . . . . 7 2.5 Definition Substitutions . . . . . . . . . . . . . . . . . 7 4. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 9 5. Informative References . . . . . . . . . . . . . . . . . . . 276 6. Security Considerations . . . . . . . . . . . . . . . . . . . 293 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 293 8. Author's Address . . . . . . . . . . . . . . . . . . . . . . . 293 9. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 293 Shirey Informational [Page 2] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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] -- and of all other Internet-related material, too. 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- 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 Shirey Informational [Page 3] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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.". Shirey Informational [Page 4] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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 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)", 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. Shirey Informational [Page 5] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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 [Raym]: Programmers use pairs of quotation marks the same way they use pairs of parentheses, i.e., as balanced delimiters. For example, if " 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 Each entry in this Glossary is marked as type I, N, O, or D: 3.1 Type "I": Recommended Term or Definition with Internet Basis 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 Shirey Informational [Page 6] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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 1) for the standardization status of the protocol. 3.2 Type "N": Recommended Term or Definition with Non-Internet Basis 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 non-Internet basis 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 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. Shirey Informational [Page 7] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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 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 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. Shirey Informational [Page 8] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 4. Definitions $ *-property (N) Synonym for "confinement property" in the context of the Bell- LaPadula model. Pronunciation: star property. $ 3DES See: Triple Data Encryption Algorithm. $ A1 computer system (O) See: TCSEC. $ 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.) Usage: This term is often incorrectly used to refer to BER. 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 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.) Shirey Informational [Page 9] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ 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, might be treated as not having "access" (and, therefore, be exempt from security policy requirements, such as the need for a security clearance). 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. Tutorial: An ACC is sometimes used in conjunction with a key center to implement access control in a key distribution system Shirey Informational [Page 10] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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, either implicitly or explicitly, the types of access granted to each. (Compare: access control matrix, access list, access profile, capability.) $ 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 -- that a subject can potentially perform on an object in an information system. [Huff] $ access policy (I) A kind of "security policy". (See: access, access control.) $ access profile (O) /information system/ A mechanism that implements access Shirey Informational [Page 11] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 control 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.) Usage: The definition is not widely known; therefore, ISDs that use this term SHOULD state a definition for it. $ 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 "individual accountability") typically involves a system capability to positively associate the identity of a user with the time, method, and mode of the user's access to the system. This capability 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. Shirey Informational [Page 12] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ 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 definition 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] $ 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.) $ 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 Shirey Informational [Page 13] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 risk.) $ administrative security 1. (I) Management procedures and constraints to prevent unauthorized access to a system. (See: (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. $ Affirm (O) A formal methodology, language, and integrated set of software tools developed at the University of Southern California's Shirey Informational [Page 14] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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. $ 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.) 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 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, ISO and, via the U.S. Shirey Informational [Page 15] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 National Committee (USNC), the International Electrotechnical Commission (IEC). 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]. $ 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: misuse detection. See: IDS.) $ anonymity (I) The condition of having a name that is unknown or concealed. (Compare: privacy. See: alias, anonymizer, anonymous credential, anonymous login, persona certificate.) 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 Shirey Informational [Page 16] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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 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] 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" certificate" depending on what is meant, with 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). 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 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) See: American National Standards Institute. Shirey Informational [Page 17] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ anti-jam (N) "Measures ensuring that transmitted information can be received despite deliberate jamming attempts." [C4009] (See: electronic security, frequency hopping, jam, spread spectrum.) $ API (I) See: application programming interface. $ APOP (I) See: POP3 APOP. $ application layer (I) See: Open Systems Interconnection Reference Model (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. $ ARPANET (N) Advanced Research Projects Agency (ARPA) Network, a pioneer packet-switched network that was designed, implemented, operated, and maintained by BBN from January 1969 until July 1975 under contract to the U.S. Government; led to the development of today's Internet; and was decommissioned in June 1990. [B4799, Hafn] $ ASCII (I) 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.) Shirey Informational [Page 18] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ ASN.1 (I) 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) A rank on a hierarchical scale of confidence 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 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 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 Shirey Informational [Page 19] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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 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 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. $ ATIS (N) See: (Alliance for Telecommunications Industry 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.) 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. Shirey Informational [Page 20] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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 (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.) $ 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, Shirey Informational [Page 21] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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) A CA that issues attribute certificates. 2. (O) "An authority [that] assigns privileges by issuing attribute certificates." [X509] Usage: The abbreviation "AA" 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. 2. (N) "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. Other attributes of a subject, such as a security clearance, may be certified in a 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.) Shirey Informational [Page 22] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ 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 between data integrity service and authentication services" under) data integrity 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 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 between data integrity service and authentication services" under) data integrity service.) Tutorial: An authentication process consists of two steps: - Identification step: Presenting an identifier to the security Shirey Informational [Page 23] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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. Instead, use "checksum", "error detection code", "hash", "keyed hash", "Message Authentication Code", or "protected checksum", depending on what is meant. 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) 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 and as much of 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 Shirey Informational [Page 24] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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 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. $ authorization 1a. (I) An approval that is granted to a system entity to access a Shirey Informational [Page 25] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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. Tutorial: The semantics and granularity of authorizations depend on the application and implementation (see: (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 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) "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.) Usage: The term is used in many ways and could easily be misunderstood; ISD that use this term SHOULD state a definition for it. $ 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 Shirey Informational [Page 26] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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] $ availability service (I) A security service that protects a system to ensure its availability. 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, B3 computer system (O) See: TCSEC. $ 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: maintenance hook.) 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.) $ backup (I) /noun or adjective/ Refers to alternate means of performing system functions despite loss of system resources. (See: Shirey Informational [Page 27] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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 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 different metaphors for this concept. Therefore, to ensure international understanding, ISDs SHOULD NOT use this term. (See: (Deprecated Usage 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] (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.) Usage: Sometimes incorrectly included under the term ASN.1, which properly refers only to the syntax description language, and not to the encoding rules for the language. $ Basic Security Option (I) See: (secondary definition under) IPSO. $ bastion host (I) A strongly protected computer that is in a network protected Shirey Informational [Page 28] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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 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. $ 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, Shirey Informational [Page 29] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 including the "confinement property" (also called "*-property", pronounced "star 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 A1 1. (O) /formal/ A level of security assurance that is beyond the highest level (level A1) of criteria specified by the TCSEC. 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 model (N) A formal, mathematical, state-transition model of integrity policy for multilevel-secure computer systems [Biba]. (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. Shirey Informational [Page 30] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ BIN (O) See: bank identification number. $ bind (I) To inseparably associate by applying some mechanism. Example: A CA uses a digital signature to bind together (a) a subject and (b) a public key, and possibly some additional, secondary data items, to create a public-key certificate. $ 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.) 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. $ bit (I) A contraction of the term "binary digit", the smallest unit of information storage, which has two possible states or values that are usually 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: color change, RED/BLACK separation.) 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 key (I) A key that is protected with a key-encrypting key and that Shirey Informational [Page 31] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 must be decrypted before use. (Compare: RED key. See: BLACK.) $ BLACKER (N) 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 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. $ 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: 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 operation to "package" the basic algorithm. Shirey Informational [Page 32] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ 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] $ brand 1. (I) A distinctive mark or name that identifies a product or business entity. 2. (O) /SET/ The name of a payment card. 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. (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.) Shirey Informational [Page 33] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 - 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 2 between two networks (usually two LANs). (Compare: router, bridge CA.) $ 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 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: 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 Shirey Informational [Page 34] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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. 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) Refers to handling keying material in large quantities, e.g., Shirey Informational [Page 35] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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 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]. $ 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]. Military- grade link encryption has mainly been implemented as bump-in-the- wire devices. $ 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.) 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, C2 computer system (O) See: TCSEC. $ 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 the term SHOULD state Shirey Informational [Page 36] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 precisely how the certificate is constructed and how it is intended to be used; the X.509 definition is ambiguous with regard to those details. (See: certificate profile.) - Constraints: A v3 X.509 public-key certificate may have a "basicConstraints" extension containing a "cA" value of "TRUE" that specifically indicates that "the certified public key may be used to verify certificate signatures." - Key Usage: A v3 X.509 public-key certificate also may have a "key Usage" extension which indicates the purposes for which the public key may be used. One purpose is "keyCertSign", for verifying a CA's signature on certificates; and if this value is present, than "cA" is also set to "TRUE" if the certificate also has a "basicConstraints" extension. However, 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 One-To-Many, <=> Many-to-Many. +- - - - - - - - - - - - - - - - - - - - - - - - - - + | PKI System | + - - - - + | +------------------+ +-------------------------+ | | User | | | Subscriber, i.e. | | Subscriber Identity | | | +-----+ | | | Registered User | | | | | |Human| | | |(Is System-Unique)| | (Is System-Unique) | | | |Being| | | | +--------------+ | | +---------------------+ | | | +-----+ | | | | User's Core | | | | Subscriber | | | | ^ |===| | Registration | |==>| | Identity's | | | | | | | | | Data, i.e., | | | | Registration Data | | | | | | | | | An Entity's | | | |+-------------------+| | | | v | | | |Distinguishing|========| Same Core Data || | | | +-----+ | | | | Attribute | | | ||For All Identities || | | | | Set | | | | | Values | | +===|| Of The Same User || | | | +-----+ | | | +--------------+ | | | |+-------------------+| | | | ^ | | +------------------+ | | +---------------------+ | | | | | | | +=======+ +------------|------------+ | | | | | +-------v----|----------------------|------------+ | | v | | | +----------v-----+ +------------v----------+ | | | +-----+ | | | | Authentication |<=>| Subscriber Identifier | | | | |Auto-| | | | | Information | | (Is System Unique) | | | | |mated| | | | +----------------+ +-----------------------+ | | | |Pro- | | | | Identity Credential | | | |cess | | | |(Associates Authentication Info. and Identifier)| | | +-----+ | | +------------------------------------------------+ | + - - - - + + - - - - - - - - - - - - - - - - - - - - - - - - - -+ An ISD may apply this term to 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 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 the resources/objects being accessed." [I7498 Part 2] (See: rule-based security policy.) $ identity credential 1. (I) See: ("authentication" context under) "credential". Shirey Informational [Page 122] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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. $ identity proofing (I) A process that vets and verifies the information that is used to establish the identity of a system entity. $ 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" (better described as a transaction type, or a protocol-within-a-protocol) 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]. Shirey Informational [Page 123] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ 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, coding, and verifying software to produce correct and reliable programs. Also known as 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 entry for) malicious logic.) - "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. - "Hardware or software error": In context of incapacitation, error that unintentionally causes failure of a system component and leads to disruption of system operation. - "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 See: (International Committee for Information Technology 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.) Shirey Informational [Page 124] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ inference 1. (I) A type of threat action that reasons from characteristics or byproducts of communication and thereby indirectly accesses 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 Shirey Informational [Page 125] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 capabilities." [C4009] $ Information Assurance Technical Framework (IATF) (O) A publicly available document [IATF], developed through a 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 definition under) domain. $ information domain security policy (O) See: (secondary definition 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 INFOCON levels are: 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.) Shirey Informational [Page 126] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ 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 combinations than the TCSEC. Superseded by the Common Criteria. $ INFOSEC (I) See: information security. $ ingress filtering (I) A method [R2267] 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) 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. $ inside attack (I) See: (secondary definition under) attack. Compare: insider.) $ insider 1. (I) A user (usually a person) that accesses a system from a Shirey Informational [Page 127] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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, correctness integrity, source integrity, 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 service may be data origin authentication; and not every checksum Shirey Informational [Page 128] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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 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 not intended to communicate the data. (See: emanation.) $ interference See: (secondary definition 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 Shirey Informational [Page 129] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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 definition 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 "internetwork". 2. (I) /capitalized/ "The Internet" is the single, interconnected, worldwide system of commercial, government, educational, and other computer networks that share the protocol suite specified by the IAB [R2026] and the name and address spaces managed by the ICANN. Tutorial: The set of protocols is called the "Internet Protocol Suite" (IPS). It also 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 of the networks in the Internet 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 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 Shirey Informational [Page 130] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 by the IETF nominating committee. [R2026] $ 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. $ 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 and the DNS root server system. $ Internet Draft (I) A working document of the IETF, its areas, and its working groups. (Other groups may also distribute working documents as Internet Drafts.) An Internet Draft is not an archival document like an RFC is. Instead, an 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". $ 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", Shirey Informational [Page 131] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 including final approval of specifications as Internet Standards. Composed of IETF Area Directors and the IETF chairperson, who also chairs the IESG. [R2026] $ 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] $ 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.) $ Internet Private Line Interface (IPLI) (I) 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 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. (See: IP address, TCP/IP.) Tutorial: In the OSIRM, IP would be located at the top of layer 3. Shirey Informational [Page 132] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ 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 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 and Key Management Protocol (ISAKMP) (I) An Internet IPsec protocol [R2408] to negotiate, establish, modify, and delete security associations, and to exchange key generation and authentication data, independent of the details of any specific key generation technique, key establishment protocol, encryption algorithm, or authentication mechanism. Tutorial: ISAKMP supports negotiation 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, 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 basic security association to be used Shirey Informational [Page 133] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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 Internet Standards); with how the Internet is and 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. [R2026] $ Internet Standard (I) A specification, approved by the IESG and published 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, and is recognizably useful in some or all parts of the Internet. [R2026] (See: RFC.) Tutorial: The "Internet Standards Process" is an activity of the ISOC and is organized and managed by the IAB and the IESG. The process is concerned with all protocols, procedures, and conventions used in or by the Internet, whether or not they are part of the IPS. 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 an Internet-Draft that is produced as part of the Internet Standards Process [R2026]. (See: Internet Standard.) Deprecated Usage: Neither the term nor the abbreviation is widely accepted; therefore, ISDs that use this term SHOULD state a definition for it. $ internetwork (I) A system of interconnected networks; a network of networks. Usually shortened to "internet". (See: internet.) Tutorial: An internet is usually built using OSIRM layer 3 gateways to connect a set of subnetworks. When the subnetworks differ in the layer 3 protocol service they provide, the gateways sometimes implement a uniform internetwork protocol (e.g., IP) that operates at the top of layer 3 and hides the underlying heterogeneity 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, and usually private, purposes and that is closed to outsiders. (See: Shirey Informational [Page 134] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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 to a 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 circumventing a system's security protections. (See: unauthorized disclosure.) Usage: This type includes the 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 design of a system component. - "Cryptanalysis": Transforming encrypted data into plain text without having prior knowledge of encryption parameters or processes. (See: (main Glossary entry for) cryptanalysis.) $ intrusion detection (I) Sensing and analyzing system events for the purpose of noticing (i.e., becoming aware of) attempts to access system resources in an unauthorized manner. (See: anomaly detection, IDS, misuse detection.) [IDSAN, IDSSC, IDSSE, IDSSY] Usage: This includes the 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 security officer for corrective action. (Compare: security audit.) $ 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 computer network and (b) analyzing them for signs of security problems. [SP31] (See: intrusion detection.) 2. (N) A security alarm system to detect unauthorized entry. [DC6/9]. Tutorial: Active intrusion detection processes can be either host- Shirey Informational [Page 135] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 based or network-based: - "Host-based": Intrusion detection components -- traffic sensors and analyzers -- run directly on the hosts that they are intended 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 the certificate should otherwise be considered invalid." [X509]. Tutorial: This date may be earlier than the 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 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 in 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 of four 8-bit numbers separated by periods. For example, the address of the host named "rosslyn.bbn.com" is 192.1.7.10. An 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 the eight 16-bit parts of 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. Shirey Informational [Page 136] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ IPsec 1a. (I) A contraction of "Internet Protocol security", the name of the IETF working group that is specifying an architecture [R2401] and set of protocols to provide security services for IP traffic. (See: AH, ESP, IKE, SAD, SPD. Compare: IPSO.) 1b. (I) A collective name for that IP security architecture and associated set of protocols. Usage: Note that the letters "sec" are in lower case in "IPsec". Tutorial: The security services provided 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) 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 of IPsec is optional for IP version 4, but mandatory for IP version 6. $ IPsec Key Exchange (IKE) (I) An Internet, IPsec, key-establishment protocol [R2409] for putting in place authenticated keying material (a) for use with ISAKMP and (b) for other security associations, 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 (I) See: Internet Security Association and Key Management Protocol. $ ISD (I) See: Internet Standards document. $ ISO (I) International Organization for Standardization, a voluntary, non-treaty, non-government organization, established in 1947, with voting members that are designated standards bodies of participating nations and non-voting observer organizations. (Compare: ANSI, IETF, ITU-T, W3C.) Tutorial: Legally, ISO is a Swiss, non-profit, private organization. ISO and the IEC (the International Electrotechnical Shirey Informational [Page 137] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 Commission) form the specialized system for worldwide standardization. National bodies that are members of ISO or IEC participate in developing international standards through ISO and IEC technical committees that deal with particular fields of activity. Other international governmental and non-governmental organizations, in liaison with ISO and IEC, also take part. (ANSI is the U.S. voting member of ISO. ISO is a class D member of ITU-T.) The ISO standards development process has four levels of increasing maturity: Working Draft (WD), Committee Draft (CD), Draft International Standard (DIS), and International Standard (IS). (Compare: (standards track levels under) Internet Standard.) 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. $ ISO 17799 (N) An International Standard that is a code of practice, derived from Part 1 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). (See: certificate creation.) Usage: The ABA Guidelines [ABA] explicitly limit this term to certificate creation, and exclude the act of publishing. In general usage, however, "issuing" a digital certificate (or CRL) includes not only certificate creation but also making it available to potential users, such as by storing it in a repository or other directory or otherwise publishing it. $ issuer 1. (I) /certificate, CRL/ The CA that signs a digital certificate or CRL. Tutorial: An X.509 certificate always includes the issuer's name. The name may include a common name value. 2. (O) /payment card, SET/ "The financial institution or its agent that issues the unique primary account number to the cardholder for the payment card brand." [SET2] Shirey Informational [Page 138] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 Tutorial: The institution that establishes the account for a cardholder and issues the payment card also guarantees payment for authorized transactions that use the card in accordance with card brand regulations 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". (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. $ jamming (I) An attack that attempts to interfere with the reception of broadcast communications. (See: anti-jam, denial of service. Compare: flooding.) Tutorial: Jamming uses "interference" as a type of "obstruction" intended to cause "disruption". Jamming a broadcast signal is typically done by broadcasting a second signal that receivers cannot separate from the first one. Jamming is mainly thought of in the context 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.) Shirey Informational [Page 139] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ Kerberos (N) A system developed at the Massachusetts Institute of Technology that depends on passwords and symmetric cryptography (DES) 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 an ACC and a KDC. $ kernel (I) A small, trusted part of a system that provides services on which the other parts of the system depend. (See: security kernel.) $ Kernelized Secure Operating System (KSOS) (O) An MLS computer operating system, designed to be a provably secure replacement for UNIX Version 6, and consisting of a security kernel, non-kernel security-related utility programs, and optional UNIX application development and support environments. [Perr] Tutorial: KSOS-6 was the implementation on a SCOMP. KSOS-11 was the implementation by Ford Aerospace and Communications Corporation on the DEC PDP-11/45 and PDP-111/70 computers. $ 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/ An input parameter used to vary a process that determines patterns for an anti-jam measure. (See: frequency hopping, spread spectrum.) Tutorial: A key is usually specified as a sequence of bits or other symbols. If a key value needs to be kept secret, the sequence of symbols that comprise it should be random, or at least pseudorandom, because that makes the key hard for an adversary 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 a public exchange of data (such as public keys), each can generate the same key value. That is, the method does not send a secret from one entity to the other (compare: key transport); instead, both entities, without prior arrangement except a public exchange of data, can compute the same secret value, but that value cannot be computed by other, unauthorized entities. (See: Diffie-Hellman, key establishment, KEA, MQV.) Shirey Informational [Page 140] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 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 that any of the shared symmetric keys is a function of the information contributed by all legitimate participants, so that no party [alone] can predetermine the value of the key." [A9042] Example: A message originator and the intended recipient can each use their own private key 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. $ key authentication (N) "The assurance of the legitimate participants in a key agreement that no non-legitimate party possesses the shared symmetric key." [A9042] $ key-auto-key (KAK) (D) "Cryptographic logic using previous key to produce key." [C4009, A1523] (See: CTAK.) Deprecated Term: IDS should not use this term; it is neither well- known nor precisely defined. Instead, use terms associated with modes that 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 in a community of users. Tutorial: An ANSI standard [A9017] defines two types of key center: key distribution center and key translation center. $ key confirmation (N) "The assurance [provided to] the legitimate participants in a key establishment protocol that the [parties that are intended to share] the symmetric key actually possess the shared symmetric key." [A9042] $ key distribution (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.) $ key distribution center (KDC) 1. (I) A type of key center (used in symmetric cryptography) that implements a key distribution protocol to provide keys (usually, Shirey Informational [Page 141] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 session keys) to two (or more) entities that wish to communicate securely. (Compare: key translation center.) 2. (N) "COMSEC facility generating and distributing key in electrical form." [C4009] Tutorial: A KDC distributes keys to Alice and Bob, who (a) wish to communicate with each other but do not currently share keys, (b) each share a KEK with the KDC, and (c) may not be able to generate or acquire keys by themselves. Alice requests the keys from the KDC. The KDC generates or acquires the keys and makes two identical sets. The KDC encrypts one set in the KEK it shares with Alice, and sends that encrypted set to Alice. The KDC encrypts the second set in the KEK it shares with Bob, and either (a) sends that encrypted set to Alice for her to forward to Bob or (b) sends it directly to Bob (although the latter option is not supported in the ANSI standard [A9017]). $ key encapsulation (N) A key recovery technique for storing knowledge of a cryptographic key by encrypting it with another key and ensuring that that only certain third parties called "recovery agents" can perform the decryption operation to retrieve the stored key. Key encapsulation typically permits direct retrieval of a secret key used to provide data confidentiality. (Compare: key escrow.) $ key-encrypting key (KEK) (I) A cryptographic key that (a) is used to encrypt other keys (either DEKs or other TEKs) for transmission or storage but (b) usually is not used to encrypt application data. Usage: Sometimes called "key-encryption key". $ key escrow (N) A key recovery technique for storing knowledge of a cryptographic key or parts thereof in the custody of one or more third parties called "escrow agents", so that the key can be recovered and used in specified circumstances. (Compare: key encapsulation.) Tutorial: Key escrow is typically implemented with split knowledge techniques. For example, the Escrowed Encryption Standard [FP185] entrusts two components of a device-unique split key to separate escrow agents. The agents provide the components only to someone legally authorized to conduct electronic surveillance of telecommunications encrypted by that specific device. The components are used to reconstruct the device-unique key, and it is used to obtain the session key needed to decrypt communications. $ key establishment (algorithm or protocol) 1. (I) A procedure that combines the key generation and key distribution steps needed to set up or install a secure Shirey Informational [Page 142] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 communication association. 2. (I) A procedure that results in keying material being shared among two or more system entities. [A9042, SP56] Tutorial: The two basic techniques for key establishment are "key agreement" and "key transport". $ Key Exchange Algorithm (KEA) (N) A key-agreement method [SKIP, R2773] based on the Diffie- Hellman algorithm and uses 1024-bit asymmetric keys. (See: CAPSTONE, CLIPPER, FORTEZZA, SKIPJACK.) Tutorial: KEA was developed by NSA and formerly classified at the U.S. DoD "Secret" level. On 23 June 1998, the NSA announced that KEA had been declassified. $ key generation (I) A process that creates the sequence of symbols that comprise a cryptographic key. (See: key management.) $ key generator 1. (I) An algorithm that uses mathematical rules to deterministically produce a pseudorandom sequence of cryptographic key values. 2. (I) An encryption device that incorporates a key generation mechanism and applies the key to plain text to produce cipher text (e.g., by exclusive OR-ing (a) a bit string representation of the key with (b) a bit string representation of the plaintext). $ key length (I) The number of symbols (usually stated as a number of bits) needed to be able to represent any of the possible values of a cryptographic key. (See: key space.) $ key lifetime (N) /MISSI/ An attribute of a MISSI key pair that specifies a time span that bounds the validity period of any MISSI X.509 public-key certificate that contains the public component of the pair. (See: cryptoperiod.) $ key loader (N) Synonym for "fill device". $ key management 1a. (I) The process of handling keying material during its life cycle in a cryptographic system; and the supervision and control of that process. (See: key distribution, key escrow, keying material, public-key infrastructure.) Usage: Usually understood to include ordering, generating, Shirey Informational [Page 143] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 storing, archiving, escrowing, distributing, loading, destroying, auditing, and accounting for the material. 1b. (O) /NIST/ "The activities involving the handling of cryptographic keys and other related security parameters (e.g., IVs, counters) during the entire life cycle of the keys, including their generation, storage, distribution, entry and use, deletion or destruction, and archiving." [FP140, SP57] 2. (O) /OSIRM/ "The generation, storage, distribution, deletion, archiving and application of keys in accordance with a security policy." [I7498 Part 2] $ Key Management Protocol (KMP) (N) A protocol to establish a shared symmetric key between a pair (or a group) of users. (One version of KMP was developed by SDNS, and another by SILS.) Superseded by ISAKMP and IKE. $ key material (D) A synonym for "keying material". Deprecated Usage: ISDs SHOULD NOT use this term as a synonym for "keying material". $ key pair (I) A set of mathematically related keys -- a public key and a private key -- that are used for asymmetric cryptography and are generated in a way that makes it computationally infeasible to derive the private key from knowledge of the public key. (See: Diffie-Hellman, RSA.) Tutorial: A key pair's owner discloses the public key to other system entities so they can use the key to (a) encrypt data, (b) verify a digital signature, (c) compute a protected checksum, or (d) generate a key in a key agreement algorithm. The matching private key is kept secret by the owner, who uses it to (a') decrypt data, (b') generate a digital signature, (c') verify a protected checksum, or (d') generate a key in a key agreement algorithm. $ key recovery 1. (I) /cryptanalysis/ A process for learning the value of a cryptographic key that was previously used to perform some cryptographic operation. (See: cryptanalysis, recovery.) 2. (I) /backup/ Techniques that provide an intentional, alternate, means to access the key used for data confidentiality service in an encrypted association. [DoD4] (Compare: recovery.) Tutorial: It is assumed that the cryptographic system includes a primary means of obtaining the key through a key establishment algorithm or protocol. For the secondary means, there are two Shirey Informational [Page 144] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 classes of key recovery techniques: key encapsulation and key escrow. $ key space (I) The range of possible values of a cryptographic key; or the number of distinct transformations supported by a particular cryptographic algorithm. (See: key length.) $ key translation center (I) A type of key center that implements a key distribution protocol (based on symmetric cryptography) to convey keys between two (or more) parties who wish to communicate securely. (Compare: key distribution center.) Tutorial: A key translation center transfers keys for future communication between Bob and Alice, who (a) wish to communicate with each other but do not currently share keys, (b) each share a KEK with the center, and (c) have the ability to generate or acquire keys by themselves. Alice generates or acquires a set of keys for communication with Bob. Alice encrypts the set in the KEK she shares with the center and sends the encrypted set to the center. The center decrypts the set, reencrypts the set in the KEK it shares with Bob, and either (a) sends that reencrypted set to Alice for her to forward to Bob or (b) sends it directly to Bob (although direct distribution is not supported in the ANSI standard [A9017]). $ key transport (algorithm or protocol) 1. (I) A key establishment method by which a secret key is generated by a system entity in a communication association and securely sent to another entity in the association. (Compare: key agreement.) Tutorial: Either (a) one entity generates a secret key and securely sends it to the other entity, or (b) each entity generates a secret value and securely sends it to the other entity, where the two values are combined to form a secret key. For example, a message originator can generate a random session key and then use the RSA algorithm to encrypt that key with the public key of the intended recipient. 2. (O) "The procedure to send a symmetric key from one party to other parties. As a result, all legitimate participants share a common symmetric key in such a way that the symmetric key is determined entirely by one party." [A9042] $ key update 1. (I) Derive a new key from an existing key. (Compare: rekey.) 2. (O) Irreversible cryptographic process that modifies a key to produce a new key. [C4009] Shirey Informational [Page 145] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ key validation 1. (I) "The procedure for the receiver of a public key to check that the key conforms to the arithmetic requirements for such a key in order to thwart certain types of attacks." [A9042] (See: weak key) 2. (D) A synonym for "certificate validation". Deprecated Usage: ISDs SHOULD NOT use the term as a synonym for "certificate validation"; that would unnecessarily duplicate the meaning of the latter term and mix concepts in a potentially misleading way. In validating an X.509 public-key certificate, the public key contained in the certificate is normally treated as an opaque data object. $ keyed hash (I) A cryptographic hash (e.g., [R1828]) in which the mapping to a hash result is varied by a second input parameter that is a cryptographic key. (See: checksum.) Tutorial: If the input data object is changed, a new, corresponding hash result cannot be correctly computed without knowledge of the secret key. Thus, the secret key protects the hash result so it can be used as a checksum even when there is a threat of an active attack on the data. There are two basic types of keyed hash: - A function based on a keyed encryption algorithm. Example: Data Authentication Code. - A function based on a keyless hash that is enhanced by combining (e.g., by concatenating) the input data object parameter with a key parameter before mapping to the hash result. Example: HMAC. $ keying material (I) Data that is needed to establish and maintain a cryptographic security association, such as keys, key pairs, and IVs. (O) "Key, code, or authentication information in physical or magnetic form." [C4009] (Compare: COMSEC material.) $ keying material identifier (KMID) 1. (I) An identifier assigned to an item of keying material. 2. (O) /MISSI/ A 64-bit identifier that is assigned to a key pair when the public key is bound in a MISSI X.509 public-key certificate. $ Khafre (N) A patented, symmetric block cipher designed by Ralph C. Merkle as a plug-in replacement for DES. [Schn] Shirey Informational [Page 146] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 Tutorial: Khafre was designed for efficient encryption of small amounts of data. However, because Khafre does not precompute tables used for encryption, it is slower than Khufu for large amounts of data. $ Khufu (N) A patented, symmetric block cipher designed by Ralph C. Merkle as a plug-in replacement for DES. [Schn] Tutorial: Khufu was designed for fast encryption of large amounts of data. However, because Khufu precomputes tables used in encryption, it is less efficient that Khafre for small amounts of data. $ KMID (I) See: keying material identifier. $ known-plaintext attack (I) A cryptanalysis technique in which the analyst tries to determine the key from knowledge of some plaintext-ciphertext pairs (although the analyst may also have other clues, such as the knowing the cryptographic algorithm). $ KSOS, KSOS-6, KSOS-11 (O) See: Kernelized Secure Operating System. $ L2F (N) See: Layer 2 Forwarding Protocol. $ L2TP (N) See: Layer 2 Tunneling Protocol. $ label See: time stamp, security label. $ laboratory attack (O) "Use of sophisticated signal recovery equipment in a laboratory environment to recover information from data storage media." [C4009] $ LAN (I) Local area network. $ land attack (I) A denial-of-service attack that sends an IP packet that (a) has the same address in both the Source Address and Destination Address fields and (b) contains a TCP SYN packet that has the same port number in both the Source Port and Destination Port fields. Derivation: This single-packet attack was named for "land", the program originally published by the cracker who invented this Shirey Informational [Page 147] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 exploit. Perhaps that name was chosen because the inventor thought of multi-packet (i.e., flooding) attacks as arriving by "sea". $ Language of Temporal Ordering Specification (LOTOS) (N) A language (ISO 8807-1990) for formal specification of computer network protocols; describes the order in which events occur. $ lattice (I) A finite set together with a partial ordering on its elements such that for every pair of elements there is a least upper bound and a greatest lower bound. Example: A lattice is formed by a finite set S of security levels -- i.e., a set S of all ordered pairs (x,c), where x is one of a finite set X of hierarchically ordered classification levels X(1), non-hierarchical categories C(1), ..., C(M) -- together with the "dominate" relation. Security level (x,c) is said to "dominate" (x',c') if and only if (a) x is greater (higher) than or equal to x' and (b) c includes at least all of the elements of c'. (See: dominate, lattice model.) $ lattice model 1. (I) A description of the semantic structure formed by a finite set of security levels, such as those used in military organizations. (See: dominate, security model.) 2. (I) /formal model/ A model for flow control in a system, based on the lattice that is formed by the finite security levels in a system and their partial ordering. [Denn] $ Law Enforcement Access Field (LEAF) (N) A data item that is automatically embedded in data encrypted by devices (e.g., CLIPPER chip) that implement the Escrowed Encryption Standard. $ layer 1, 2, 3, 4, 5, 6, 7 (N) See: OSIRM. $ Layer 2 Forwarding Protocol (L2F) (N) An Internet protocol (originally developed by Cisco Corporation) that uses tunneling of PPP over IP to create a virtual extension of a dial-up link across a network, initiated by the dial-up server and transparent to the dial-up user. (See: L2TP.) $ Layer 2 Tunneling Protocol (L2TP) (N) An Internet client-server protocol that combines aspects of PPTP and L2F and supports tunneling of PPP over an IP network or over frame relay or other switched network. (See: virtual private network.) Shirey Informational [Page 148] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 Tutorial: PPP can in turn encapsulate any OSIRM layer 3 protocol. Thus, L2TP does not specify security services; it depends on protocols layered above and below it to provide any needed security. $ LDAP (I) See: Lightweight Directory Access Protocol. $ least common mechanism (I) The principle that a security architecture should minimize reliance on mechanisms that are shared by many users. Tutorial: Shared mechanisms may include cross-talk paths that permit a breach of data security, and it is difficult to make a single mechanism operate in a correct and trusted manner to the satisfaction of a wide range of users. $ least privilege (I) The principle that a security architecture should be designed so that each system entity is granted the minimum system resources and authorizations that the entity needs to do its work. (Compare: economy of mechanism, least trust.) Tutorial: This principle tends to limit damage that can be caused by an accident, error, or unauthorized act. This principle also tends to reduce complexity and promote modularity, which can make certification easier and more effective. This principle is similar to the principle of protocol layering, wherein each layer provides specific, limited communication services, and the functions in one layer are independent of those in other layers. $ least trust (I) The principle that a security architecture should be designed in a way that minimizes (a) the number of components that require trust and (b) the extent to which each component is trusted. (Compare: least privilege, trust level.) $ legacy system (I) A system that is in operation but will not be improved or expanded while a new system is being developed to supersede it. $ legal non-repudiation (I) See: (secondary definition under) non-repudiation. $ level of concern (N) /U.S. DoD/ A rating assigned to an information system that indicates the extent to which protective measures, techniques, and procedures must be applied. (See: level of robustness.) $ level of robustness (N) /U.S. DoD/ A characterization of the strength of a security function, mechanism, service, or solution, and the assurance (or Shirey Informational [Page 149] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 confidence) that is implemented and functioning correctly to support the level of concern assigned to a particular information system. $ Lightweight Directory Access Protocol (LDAP) (I) An Internet client-server protocol (RFC 3377) that supports basic use of the X.500 Directory (or other directory servers) without incurring the resource requirements of the full Directory Access Protocol (DAP). Tutorial: Designed for simple management and browser applications that provide simple read/write interactive directory service. Supports both simple authentication and strong authentication of the client to the directory server. $ link 1a. (I) A communication facility or physical medium that can sustain data communications between multiple network nodes, in the protocol layer immediately below IP. [R3573] 1b. (I) /subnetwork/ A communication channel connecting subnetwork relays (especially one between two packet switches) that is implemented at OSIRM layer 2. (See: link encryption.) Tutorial: The relay computers assume that links are logically passive. If a computer at one end of a link sends a sequence of bits, the sequence simply arrives at the other end after a finite time, although some bits may have been changed either accidentally (errors) or by active wiretapping. 2. (I) /World Wide Web/ See: hyperlink. $ link encryption (I) Stepwise (link-by-link) protection of data that flows between two points in a network, provided by encrypting data separately on each network link, i.e., by encrypting data when it leaves a host or subnetwork relay and decrypting when it arrives at the next host or relay. Each link may use a different key or even a different algorithm. [R1455] (Compare: end-to-end encryption.) $ logic bomb (I) Malicious logic that activates when specified conditions are met. Usually intended to cause denial of service or otherwise damage system resources. (See: Trojan horse, virus, worm.) $ login (I) The act by which a system entity establishes a session in which the entity can use system resources. (See: principal, session.) Usage: Usually understood to be accomplished by providing a user name and password to an access control system that authenticates Shirey Informational [Page 150] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 the user, but sometimes refers to establishing a connection with a server when no authentication or specific authorization is involved. Derivation: Refers to "log" file", a security audit trail that records (a) security events, such as the beginning of a session, and (b) the names of the system entities that initiate events. $ long title (O) /U.S. Government/ "Descriptive title of [an item of COMSEC material]." [C4009] (Compare: short title.) $ low probability of detection (I) Result of TRANSEC measures used to hide or disguise a communication. $ low probability of intercept (I) Result of TRANSEC measures used to prevent interception of a communication. $ LOTOS (N) See: Language of Temporal Ordering Specification. $ MAC (N) See: mandatory access control, Message Authentication Code. Deprecated Usage: This abbreviation is ambiguous; therefore, ISDs that use it SHOULD state a definition for it. $ magnetic remanence (N) Magnetic representation of residual information remaining on a magnetic medium after the medium has been cleared. [NCS25] (See: clear, degauss, purge.) $ maintenance hook (N) "Special instructions (trapdoors) in software allowing easy maintenance and additional feature development. Since maintenance hooks frequently allow entry into the code without the usual checks, they are a serious security risk if they are not removed prior to live implementation." [C4009] (See: back door.) $ malicious logic (I) Hardware, software, or firmware that is intentionally included or inserted in a system for a harmful purpose. (See: logic bomb, Trojan horse, spyware, virus, worm. Compare: (secondary definitions under) corruption, incapacitation, masquerade, and misuse.) $ malware (D) A contraction of "malicious software". (See: malicious logic.) Deprecated Term: ISDs SHOULD NOT use this term; it is not listed Shirey Informational [Page 151] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 in most dictionaries and could confuse international readers. $ MAN (I) metropolitan area network. $ man-in-the-middle attack (I) A form of active wiretapping attack in which the attacker intercepts and selectively modifies communicated data in order to masquerade as one or more of the entities involved in a communication association. (See: hijack attack, piggyback attack.) Tutorial: For example, suppose Alice and Bob try to establish a session key by using the Diffie-Hellman algorithm without data origin authentication service. A "man in the middle" could (a) block direct communication between Alice and Bob and then (b) masquerade as Alice sending data to Bob, (c) masquerade as Bob sending data to Alice, (d) establish separate session keys with each of them, and (e) function as a clandestine proxy server between them in order to capture or modify sensitive information that Alice and Bob think they are sending only to each other. $ manager (I) A person who controls the service configuration of a system or the functional privileges of operators and other users. $ mandatory access control 1. (I) An access control service that enforces a security policy based on comparing (a) security labels, which indicate how sensitive or critical system resources are, with (b) security clearances, which indicate that system entities are eligible to access certain resources. (See: discretionary access control, MAC, rule-based security policy.) Derivation: This kind of access control is called "mandatory" because an entity that has clearance to access a resource is not permitted, just by its own volition, to enable another entity to access that resource. 2. (O) "A means of restricting access to objects based on the sensitivity (as represented by a label) of the information contained in the objects and the formal authorization (i.e., clearance) of subjects to access information of such sensitivity." [DoD1] $ manipulation detection code (D) Synonym for "checksum". Deprecated Term: ISDs SHOULD NOT use this term as a synonym for "checksum"; the word "manipulation" implies protection against active attacks, which an ordinary checksum might not provide. Instead, if such protection is intended, use "protected checksum" or some particular type thereof, depending on which is meant. If Shirey Informational [Page 152] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 such protection is not intended, use "error detection code" or some specific type of checksum that is not protected. $ marking See: time stamp, security marking. $ Martian (D) A packet that arrives unexpectedly at the wrong address or on the wrong network because of incorrect routing or because it has a non-registered or ill-formed IP address. Deprecated Term: It is likely that other cultures have different metaphors for this concept. Therefore, to ensure international understanding, ISDs SHOULD NOT use this term. (See: (Deprecated Usage under) Green Book.) $ masquerade (I) A type of threat action whereby an unauthorized entity gains access to a system or performs a malicious act by illegitimately posing as an authorized entity. (See: deception.) Usage: This type includes the following subtypes: - "Spoof": Attempt by an unauthorized entity to gain access to a system by posing as an authorized user. - "Malicious logic": In context of masquerade, any hardware, firmware, or software (e.g., Trojan horse) that appears to perform a useful or desirable function, but actually gains unauthorized access to system resources or tricks a user into executing other malicious logic. (See: (main entry for) malicious logic.) $ MCA (O) See: merchant certification authority. $ MD2 (N) A cryptographic hash [R1319] that produces a 128-bit hash result, was designed by Ron Rivest, and is similar to MD4 and MD5 but slower. Derivation: Apparently an abbreviation of "message digest", but that term is deprecated by this Glossary. $ MD4 (N) A cryptographic hash [R1320] that produces a 128-bit hash result and was designed by Ron Rivest. (See: SHA-1, (Derivation under) MD2.) $ MD5 (N) A cryptographic hash [R1321] that produces a 128-bit hash result and was designed by Ron Rivest to be an improved version of MD4. (See: (Derivation under) MD2.) Shirey Informational [Page 153] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ merchant (O) /SET/ "A seller of goods, services, and/or other information who accepts payment for these items electronically." [SET2] A merchant may also provide electronic selling services and/or electronic delivery of items for sale. With SET, the merchant can offer its cardholders secure electronic interactions, but a merchant that accepts payment cards is required to have a relationship with an acquirer. [SET1, SET2] $ merchant certificate (O) /SET/ A public-key certificate issued to a merchant. Sometimes used to refer to a pair of such certificates where one is for digital signature use and the other is for encryption. $ merchant certification authority (MCA) (O) /SET/ A CA that issues digital certificates to merchants and is operated on behalf of a payment card brand, an acquirer, or another party according to brand rules. Acquirers verify and approve requests for merchant certificates prior to issuance by the MCA. An MCA does not issue a CRL, but does distribute CRLs issued by root CAs, brand CAs, geopolitical CAs, and payment gateway CAs. [SET2] $ mesh PKI (I) A non-hierarchical PKI architecture in which there are several trusted CAs rather than a single root. Each certificate user bases path validations on the public key of one of the trusted CAs, usually the one that issued that user's own public-key certificate. Rather than having superior-to-subordinate relationships between CAs, the relationships are peer-to-peer, and CAs issue cross-certificates to each other. (Compare: hierarchical PKI, trust-file PKI.) $ Message Authentication Code, message authentication code (N) /capitalized/ A specific ANSI standard for a checksum that is computed with a keyed hash that is based on DES. [A9009] Also known as the U.S. Government standard Data Authentication Code. [FP113] (See: MAC.) (D) /not capitalized/ Synonym for "error detection code". Deprecated Term: ISDs SHOULD NOT use the uncapitalized form "message authentication code"; that form mixes concepts in a potentially misleading way. Instead, use "checksum", "error detection code", "hash", "keyed hash", "Message Authentication Code", or "protected checksum", depending on what is meant. (See: authentication code.) In the uncapitalized form, the word "message" is misleading because it implies that the mechanism is particularly suitable for or limited to electronic mail (see: Message Handling Systems), the word "authentication" is misleading because the mechanism Shirey Informational [Page 154] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 primarily serves a data integrity function rather than an authentication function, and the word "code" is misleading because it implies that either encoding or encryption is involved or that the term refers to computer software. $ message digest (D) Synonym for "hash result". (See: cryptographic hash.) Deprecated Term: ISDs SHOULD NOT use this term as a synonym for "hash result"; the term unnecessarily duplicates the meaning of the other, more general term and mixes concepts in a potentially misleading way. The word "message" is misleading because it implies that the mechanism is particularly suitable for or limited to electronic mail (see: Message Handling Systems). $ message handling system (D) A synonym for the Internet electronic mail system. Deprecated Term: ISDs SHOULD NOT use this term, because it could be confused with Message Handling System. Instead, use "Internet electronic mail" or some other, more specific term. $ Message Handling System (O) A ITU-T system concept that encompasses the notion of electronic mail but defines more comprehensive OSI systems and services that enable users to exchange messages on a store-and- forward basis. (The ISO equivalent is "Message Oriented Text Interchange System".) (See: X.400.) $ message indicator 1. (D) /cryptographic function/ Synonym for "initialization value". 2. (D) "Sequence of bits transmitted over a communications system for synchronizing cryptographic equipment." [C4009] Deprecated Term: ISDs SHOULD NOT use this term as a synonym for "initialization value"; the term mixes concepts in a potentially misleading way. The word "message" is misleading because it suggests that the mechanism is limited to electronic mail. (See: Message Handling System.) $ message integrity check $ message integrity code (MIC) (D) Synonyms for some form of "checksum". Deprecated Term: ISDs SHOULD NOT use these terms for any form of checksum. Instead, use "checksum", "error detection code", "hash", "keyed hash", "Message Authentication Code", or "protected checksum", depending on what is meant. The terms mix concepts in potentially misleading ways. The word Shirey Informational [Page 155] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 "message" is misleading because it suggests that the mechanism is particularly suitable for or limited to electronic mail. The word "integrity" is misleading because the checksum may be used to perform a data origin authentication function rather than an integrity function. The word "code" is misleading because it suggests either that either encoding or encryption is involved or that the term refers to computer software. $ Message Security Protocol (MSP) (N) A secure message handling protocol [SDNS7] for use with X.400 and Internet mail protocols. Developed by NSA's SDNS program and used in the U.S. DoD's Defense Message System. $ meta-data (I) Descriptive information about a data object; i.e., data about data, or data labels that describe other data. (See: security label. Compare: metadata) Tutorial: Meta-data can serve various management purposes: - System management: File name, type, size, creation date. - Application management: Document title, version, author. - Usage management: Data categories, keywords, classifications. Meta-data can be associated with a data object in two basic ways: - Explicitly: Be part of the data object (e.g., a header field of a data file or packet) or be linked to the object. - Implicitly: Be associated with the data object because of some other, explicit attribute of the object. $ metadata, Metadata(trademark), METADATA(trademark) (O) A proprietary variant of "meta-data". (See: SPAM(trademark).) Deprecated Usage: The terms "Metadata" and "METADATA" are claimed as registered trademarks (numbers 1,409,260 and 2,185,504) owned by The Metadata Company, originally known as Metadata Information Partners, a company founded by Jack Myers. To avoid litigation, this Glossary recommends a hyphenated form, "meta-data". $ MHS (N) See: message handling system. $ MIC (D) See: message integrity code. $ MIME (I) See: Multipurpose Internet Mail Extensions. $ MIME Object Security Services (MOSS) (I) An Internet protocol [R1848] that applies end-to-end encryption and digital signature to MIME message content, using symmetric cryptography for encryption and asymmetric cryptography for key distribution and signature. MOSS is based on features and Shirey Informational [Page 156] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 specifications of PEM. (See: S/MIME.) $ Minimum Interoperability Specification for PKI Components (MISPC) (N) A technical description to provide a basis for interoperation between PKI components from different vendors; consists primarily of a profile of certificate and CRL extensions and a set of transactions for PKI operation. [SP15] $ misappropriation (I) A type of threat action whereby an entity assumes unauthorized logical or physical control of a system resource. (See: usurpation.) Usage: This type includes the following subtypes: - Theft of data: Unauthorized acquisition and use of data contained in a system. - Theft of service: Unauthorized use of a system service. - Theft of functionality: Unauthorized acquisition of actual hardware, software, or firmware of a system component. $ MISPC (N) See: Minimum Interoperability Specification for PKI Components. $ MISSI (N) Multilevel Information System Security Initiative, an NSA program to encourage development of interoperable, modular products for constructing secure network information systems in support of a wide variety of Government missions. (See: MSP, SP3, SP4.) $ MISSI user (O) /MISSI/ A system entity that is the subject of one or more MISSI X.509 public-key certificates issued under a MISSI certification hierarchy. (See: personality.) Tutorial: MISSI users include both end users and the authorities that issue certificates. A MISSI user is usually a person but may be a machine or other automated process. Some machines are required to operate non-stop. To avoid downtime needed to exchange the FORTEZZA cards of machine operators at shift changes, the machines may be issued their own cards, as if they were persons. $ mission (I) A statement of a (relatively long-term) duty or (relatively short-term) task that is assigned to an organization or system, indicates the purpose and objectives of the duty or task, and may indicate the actions to be taken to achieve it. $ mission critical (I) A condition of a system service or other system resource such that denial of access to, or lack of availability of, the resource Shirey Informational [Page 157] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 would jeopardize a system user~Os ability to perform a primary mission function or would result in other serious consequences. (Compare: mission essential.) $ mission essential (O) /DoD/ Refers to materiel that is authorized and available to combat, combat support, combat service support, and combat readiness training forces to accomplish their assigned missions. [JCSP1] (Compare: mission critical.) $ misuse 1. (I) The intentional use (by authorized users) of system resources for other than authorized purposes. Example: An authorized system administrator creates an unauthorized account for a friend. 2. (I) A type of threat action that causes a system component to perform a function or service that is detrimental to system security. (See: usurpation.) Usage: This type includes the following subtypes: - "Tampering": In context of misuse, deliberately altering a system's logic, data, or control information to cause the system to perform unauthorized functions or services. (See: (main entry for) tampering.) - "Malicious logic": In context of misuse, any hardware, software, or firmware intentionally introduced into a system to perform or control execution of an unauthorized function or service. (See: (main entry for) malicious logic.) - "Violation of authorizations": Action by an entity that exceeds the entity's system privileges by executing an unauthorized function. (See: authorization.) $ misuse detection (I) An intrusion detection method that is based on rules that specify system events, sequences of events, or observable properties of a system that are believed to be symptomatic of security incidents. (See: IDS. Compare: anomaly detection.) $ MLS (I) See: multilevel secure $ mobile code 1a. (I) Software that originates from a remote server or is embedded in a document or other application file, is transmitted across a network, and is loaded onto and executed on a local client system. 1b. (O) /U.S. DoD/ "Software obtained from remote systems outside the enclave boundary, transferred across a network, and then downloaded and executed on a local system without explicit installation or execution by the recipient." Shirey Informational [Page 158] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 2a. (O) /U.S. DoD/ "Technology that enables the creation of executable information that can be delivered to an information system and directly executed on any hardware/software architecture that has an appropriate host execution environment." 2b. (O) "Programs (e.g., script, macro, or other portable instruction) that can be shipped unchanged to a heterogeneous collection of platforms and execute with identical semantics" [SP- 28]. (See: active content.) Tutorial: Mobile code might be malicious. Using techniques such as "code signing" and a "sandbox" can reduce the risks of receiving and executing mobile code. $ mode $ mode of operation 1. (I) /encryption/ A technique for enhancing the effect of a cryptographic algorithm or adapting the algorithm for an application, such as applying a block cipher to a sequence of data blocks or a data stream. (See: ECB, CBC, CFB, OFB.) 2. (I) /system operation/ A type of security policy that states the range of classification levels of information that a system is permitted to handle and the range of clearances and authorizations of users who are permitted to access the system. (See: dedicated security mode, multilevel security mode, partitioned security mode, system high security mode.) $ modulus (I) The defining constant in modular arithmetic, and usually a part of the public key in asymmetric cryptography that is based on modular arithmetic. (See: Diffie-Hellman, RSA.) $ Mondex (O) A smartcard-based electronic money system that incorporates cryptography and can be used to make payments via the Internet. (See: IOTP.) $ Morris Worm (I) A worm program that flooded the ARPANET in November, 1988, causing problems for thousands of hosts. [R1135] (See: worm.) $ MOSS (I) See: MIME Object Security Services. $ MQV (N) A key-agreement protocol [Mene] that was proposed by A.J. Menezes, M. Qu, and S.A. Vanstone in 1995 and is based on the Diffie-Hellman algorithm. Shirey Informational [Page 159] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ MSP (N) See: Message Security Protocol. $ multicast security See: secure multicast $ Multics (N) MULTiplexed Information and Computing Service, an MLS computer timesharing system designed and implemented during 1965-69 by a consortium including Massachusetts Institute of Technology, General Electric, and Bell Laboratories, and later offered commercially by Honeywell. Tutorial: Multics was one of the first large, general-purpose, operating systems to include security as a primary goal from the inception of the design and development and was rated in TCSEC Class B2. Its many innovative hardware and software security mechanisms (e.g., protection ring) were adopted by later systems. $ multilevel secure (MLS) (I) Describes an information system that is trusted to contain, and maintain separation between, resources (particularly stored data) of different security levels. (Examples: BLACKER, CANEWARE, KSOS, Multics, SCOMP.) Usage: Usually understood to mean that the system permits concurrent access by users who differ in their access authorizations, while denying users access to resources for which they lack authorization. $ multilevel security mode 1. (N) A mode of system operation that allows two or more security levels of information to be handled concurrently within the same system when not all users have a clearance or specific access authorization for all data handled by the system. [DoD2] Usage: This term was defined in U.S. DoD policy regarding system accreditation [DoD2], but the term is also used outside the Defense Department and outside government. This term can be defined more precisely as follows: 2. (N) A mode of system operation in which all three of the following statements are true: (a) Some authorized users do not have a security clearance for all the information handled in the system. (b) All authorized users have the proper security clearance and appropriate specific access approval for the information to which they have access. (c) All authorized users have a need-to-know only for information to which they have access. [C4009] $ Multipurpose Internet Mail Extensions (MIME) (I) An Internet protocol (RFC 2045) that enhances the basic format Shirey Informational [Page 160] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 of Internet electronic mail messages (RFC 822) to be able to use character sets other than U.S. ASCII for textual headers and text content, and to carry non-textual and multi-part content. (See: S/MIME.) $ mutual suspicion (I) The state that exists between two interacting system entities in which neither entity can trust the other to function correctly with regard to some security requirement. $ name (I) Synonym for "identifier". $ National Computer Security Center (NCSC) (O) A U.S. DoD organization, housed in NSA, that has responsibility for encouraging widespread availability of trusted computer systems throughout the Federal Government. It has established criteria for, and performed evaluations of, computer and network systems that have a TCB. (See: Evaluated Products List, Rainbow Series, TCSEC.) $ National Information Assurance Partnership (NIAP) (N) An joint initiative of NIST and NSA to enhance the quality of commercial products for information security and increase consumer confidence in those products through objective evaluation and testing methods. Tutorial: NIAP is registered, through the U.S. DoD, as a National Performance Review Reinvention Laboratory. NIAP functions include the following: - Developing tests, test methods, and other tools that developers and testing laboratories may use to improve and evaluate security products. - Collaborating with industry and others on research and testing programs. - Using the Common Criteria to develop protection profiles and associated test sets for security products and systems. - Cooperating with the NIST National Voluntary Laboratory Accreditation Program to develop a program to accredit private- sector laboratories for the testing of information security products using the Common Criteria. - Working to establish a formal, international mutual recognition scheme for a Common Criteria-based evaluation. $ National Institute of Standards and Technology (NIST) (N) A U.S. Department of Commerce organization that promotes U.S. economic growth by working with industry to develop and apply technology, measurements, and standards. Has primary Government responsibility for INFOSEC standards for unclassified but sensitive information. (See: ANSI, DES, DSA, DSS, FIPS, NIAP, NSA.) Shirey Informational [Page 161] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ National Security Agency (NSA) (N) A U.S. DoD organization that has primary Government responsibility for INFOSEC standards for classified information and for unclassified but sensitive information handled by national security systems. (See: FORTEZZA, KEA, MISSI, NIAP, NIST, SKIPJACK.) $ national security information (N) /U.S. Government/ Information that has been determined, pursuant to Executive Order 12958 or any predecessor order, to require protection against unauthorized disclosure. [C4009] $ national security system (O) /U.S. Government/ Any Government-operated information system for which the function, operation, or use (a) involves intelligence activities; (b) involves cryptologic activities related to national security; (c) involves command and control of military forces; (d) involves equipment that is an integral part of a weapon or weapon system; or (c) is critical to the direct fulfillment of military or intelligence missions and does not include a system that is to be used for routine administrative and business applications (including payroll, finance, logistics, and personnel management applications). [Title 40 U.S.C. Section 1552, Information Technology Management Reform Act of 1996.] (See: type 2 product.) $ NCSC (O) See: National Computer Security Center. $ need to know (I) The necessity for access to, knowledge of, or possession of specific information required to carry out official duties. Tutorial: The need-to-know criterion is used in security procedures that require a custodian of sensitive information, prior to disclosing the information to someone else, to establish that the intended recipient has proper authorization to access the information. $ network (I) An information system comprised of a collection of interconnected modes. (See: computer network.) $ Network Layer Security Protocol (NLSP). (N) An OSI protocol (IS0 11577) for end-to-end encryption services at the top of OSIRM layer 3. NLSP is derived from SP3 but is more complex. (Compare: IPsec.) $ network weaving (I) A penetration technique in which an intruder avoids detection and traceback by using multiple linked communication networks to access and attack a system. [C4009] Shirey Informational [Page 162] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ NIAP (N) See: National Information Assurance Partnership. $ nibble (D) Half of a byte (i.e., usually, 4 bits). Deprecated Term: To ensure international understanding, ISDs SHOULD NOT use this term; instead, state the size of the block explicitly (e.g., "4-bit block"). (See: (Deprecated Usage under) Green Book.) $ NIPRNET (O) The U.S. DoD~Os common-use Non-Classified Internet Protocol Router Network; the part of the Internet that is wholly controlled by the U.S. DoD and is used for official DoD business. $ NIST (N) See: National Institute of Standards and Technology. $ NLSP (N) See: Network Layer Security Protocol $ no-lone zone (I) A room or other space or area to which no person may have unaccompanied access and that, when occupied, is required to be occupied by two or more appropriately authorized persons. [C4009] (See: dual control.) $ no-PIN ORA (NORA) (O) /MISSI/ An organizational RA that operates in a mode in which the ORA performs no card management functions and, therefore, does not require knowledge of either the SSO PIN or user PIN for an end user's FORTEZZA PC card. $ node (I) A collection of related subsystems located on one or more computer platforms at a single system site. $ nonce (I) A random or non-repeating value that is included in data exchanged by a protocol, usually for the purpose of guaranteeing liveness and thus detecting and protecting against replay attacks. $ non-critical See: critical. $ non-repudiation service 1. (I) A security service that provide protection against false denial of involvement in a communication. (See: repudiation, time stamp.) Shirey Informational [Page 163] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 2. (O) "Assurance [that] the sender of data is provided with proof of delivery and the recipient is provided with proof of the sender's identity, so neither can later deny having processed the data." [NS4009] Deprecated Definition: ISDs SHOULD NOT use the "O" definition because it bundles two security services -- non-repudiation with proof of origin, and non-repudiation with proof of receipt -- that can be provided independently of each other. Usage: ISDs SHOULD distinguish between the technical aspects and the legal aspects of a non-repudiation service: - "Technical non-repudiation": Refers to the assurance a relying party has that if a public key is used to validate a digital signature, that signature had to have been made by the corresponding private signature key. [SP32] -"Legal non-repudiation": Refers to how well possession or control of the private signature key can be established. [SP32] Tutorial: Non-repudiation service does not prevent an entity from repudiating a communication. Instead, the service provides evidence that can be stored and later presented to a third party to resolve disputes that arise if and when a communication is repudiated by one of the entities involved. Ford describes the six phases of a complete non-repudiation service and uses "critical action" to refer to the act of communication that is the subject of the service [For94, For97]: -------- -------- -------- -------- -------- . -------- Phase 1: Phase 2: Phase 3: Phase 4: Phase 5: . Phase 6: Request Generate Transfer Verify Retain . Resolve Service Evidence Evidence Evidence Evidence . Dispute -------- -------- -------- -------- -------- . -------- Service Critical Evidence Evidence Archive . Evidence Request => Action => Stored => Is => Evidence . Is Is Made Occurs For Later Tested In Case . Verified and Use | ^ Critical . ^ Evidence v | Action Is . | Is +-------------------+ Repudiated . | Generated |Verifiable Evidence|------> ... . ----+ +-------------------+ Phase / Explanation ------------------- 1. Request service: Before the critical action, the service requester asks, either implicitly or explicitly, to have evidence of the action be generated. 2. Generate evidence: When the critical action occurs, evidence is generated by a process involving the potential repudiator and possibly also a trusted third party. Shirey Informational [Page 164] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 3. Transfer evidence: The evidence is transferred to the requester or stored by a third party, for later use (if needed.) 4. Verify evidence: The entity that holds the evidence tests it to be sure that it will suffice if a dispute arises. 5. Retain evidence: The evidence is retained for possible future retrieval and use. 6. Resolve dispute: In this phase, which occurs only if the critical action is repudiated, the evidence is retrieved from storage, presented, and verified to resolve the dispute. $ non-repudiation with proof of origin (I) A security service that provides the recipient of data with evidence that proves the origin of the data, and thus protects the recipient against an attempt by the originator to falsely deny sending the data. This service can be viewed as a strong version of data origin authentication service, in that it proves authenticity to a third party. (See: non-repudiation service.) $ non-repudiation with proof of receipt (I) A security service that provides the originator of data with evidence that proves the data was received as addressed, and thus protects the originator against an attempt by the recipient to falsely deny receiving the data. (See: non-repudiation service.) $ non-volatile media (I) Storage media that, once written into, provide stable storage of information without an external power supply. (Compare: volatile media, permanent storage.) $ NORA (O) See: no-PIN ORA. $ notarization (I) Registration of data under the authority or in the care of a trusted third party, thus making it possible to provide subsequent assurance of the accuracy of characteristics claimed for the data, such as content, origin, time of existence, and delivery. [I7498 Part 2] (See: digital notary.) $ NSA (N) See: National Security Agency $ null (N) /encryption/ "Dummy letter, letter symbol, or code group inserted into an encrypted message to delay or prevent its decryption or to complete encrypted groups for transmission or transmission security purposes." [C4009] $ NULL encryption algorithm (I) An algorithm [R2410] that is specified as doing nothing to transform plaintext data; i.e., a no-op. It originated because ESP always specifies the use of an encryption algorithm for Shirey Informational [Page 165] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 confidentiality. The NULL encryption algorithm is a convenient way to represent the option of not applying encryption in ESP (or in any other context where a no-op is needed). (Compare: null.) $ OAKLEY (I) A key establishment protocol (proposed for IPsec but superseded by IKE) based on the Diffie-Hellman algorithm and designed to be a compatible component of ISAKMP. [R2412] Tutorial: OAKLEY establishes a shared key with an assigned identifier and associated authenticated identities for parties; i.e., OAKLEY provides authentication service to ensure the entities of each other's identity, even if the Diffie-Hellman exchange is threatened by active wiretapping. Also, it provides public-key forward secrecy for the shared key and supports key updates, incorporation of keys distributed by out-of-band mechanisms, and user-defined abstract group structures for use with Diffie-Hellman. $ object (I) /formal model/ Trusted computer system modeling usage: A system component that contains or receives information. (See: Bell-LaPadula model, trusted computer system.) $ object identifier (OID) 1. (N) An official, globally unique name for a thing, written as a sequence of integers (which are formed and assigned as defined in the ASN.1 standard) and used to reference the thing in abstract specifications and during negotiation of security services in a protocol. 2. (O) "A value (distinguishable from all other such values) which is associated with an object." [X680] Tutorial: Objects named by OIDs are leaves of the object identifier tree (which is similar to but different from the X.500 Directory Information Tree). Each arc (i.e., each branch of the tree) is labeled with a non-negative integer. An OID is the sequence of integers on the path leading from the root of the tree to a named object. The OID tree has three arcs immediately below the root: {0} for use by ITU-T, {1} for use by ISO, and {2} for use by both jointly. Below ITU-T are four arcs, where {0 0} is for ITU-T recommendations. Below {0 0} are 26 arcs, one for each series of recommendations starting with the letters A to Z, and below these are arcs for each recommendation. Thus, the OID for ITU-T Recommendation X.509 is {0 0 24 509}. Below ISO are four arcs, where {1 0 }is for ISO standards, and below these are arcs for each ISO standard. Thus, the OID for ISO/IEC 9594-8 (the ISO number for X.509) is {1 0 9594 8}. Shirey Informational [Page 166] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 ANSI registers organization names below the branch {joint-iso- ccitt(2) country(16) US(840) organization(1) gov(101) csor(3)}. The NIST CSOR records PKI objects below the branch {joint-iso-itu- t(2) country(16) us(840) organization (1) gov(101) csor(3)}. The U.S. DoD registers INFOSEC objects below the branch {joint-iso- itu-t(2) country(16) us(840) organization(1) gov(101) dod(2) infosec(1)}. The IETF's Public-Key Infrastructure (pkix) Working Group registers PKI objects below the branch {iso(1) identified- organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7)}. [R2459] $ object reuse (N) /COMPUSEC/ Reassignment and reuse of an area of a storage medium (e.g., random-access memory, floppy disk, magnetic tape) that once contained sensitive data objects. Before being reassigned for use by a new subject, the area must erased or, in some cases, purged. [NCS04] $ obstruction (I) A type of threat action that interrupts delivery of system services by hindering system operations. (See: disruption.) Tutorial: This type includes the following subtypes: - "Interference": Disruption of system operations by blocking communications or user data or control information. (See: jamming.) - "Overload": Hindrance of system operation by placing excess burden on the performance capabilities of a system component. (See: flooding.) $ OCSP (I) See: On-line Certificate Status Protocol. $ octet (I) A data unit of eight bits. (Compare: byte.) Usage: This term is used in networking (especially in OSI standards) in preference to "byte", because some systems use "byte" for data storage units of a size other than eight bits. $ OFB (N) See: output feedback. $ off-line attack (I) See: (secondary definition under) attack. $ ohnosecond (D) That minuscule fraction of time in which you realize that your private key has been compromised. Shirey Informational [Page 167] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 Deprecated Usage: This is a joke for English speakers. (See: (Deprecated Usage under) Green Book.) $ OID (N) See: object identifier. $ On-line Certificate Status Protocol (OCSP) (I) An Internet protocol [R2560] used by a client to obtain from a server the validity status and other information concerning a digital certificate. Tutorial: In some applications, such as those involving high-value commercial transactions, it may be necessary either (a) to obtain certificate revocation status that is more timely than is possible with CRLs or (b) to obtain other kinds of status information. OCSP may be used to determine the current revocation status of a digital certificate, in lieu of or as a supplement to checking against a periodic CRL. An OCSP client issues a status request to an OCSP server and suspends acceptance of the certificate in question until the server provides a response. $ one-time pad 1. (N) A manual encryption system in the form of a paper pad for one-time use. 2. (I) An encryption algorithm in which the key is a random sequence of symbols and each symbol is used for encryption only one time -- to encrypt only one plaintext symbol to produce only one ciphertext symbol -- and a copy of the key is used similarly for decryption. Tutorial: To ensure one-time use, the copy of the key used for encryption is destroyed after use, as is the copy used for decryption. This is the only encryption algorithm that is truly unbreakable, even given unlimited resources for cryptanalysis [Schn], but key management costs and synchronization problems make it impractical except in special situations. $ one-time password, One-Time Password (OTP) 1. (I) /not capitalized/ A "one-time password" is a simple authentication technique in which each password is used only once as authentication information that verifies an identity. This technique counters the threat of a replay attack that uses passwords captured by wiretapping. 2. (I) /capitalized/ "One-Time Password" is an Internet protocol [R1938] that is based on S/KEY and uses a cryptographic hash function to generate one-time passwords for use as authentication information in system login and in other processes that need protection against replay attacks. Shirey Informational [Page 168] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ one-way encryption (I) Irreversible transformation of plain text to cipher text, such that the plain text cannot be recovered from the cipher text by other than exhaustive procedures even if the cryptographic key is known. (See: encryption.) $ one-way function (I) "A (mathematical) function, f, which is easy to compute, but which for a general value y in the range, it is computationally difficult to find a value x in the domain such that f(x) = y. There may be a few values of y for which finding x is not computationally difficult." [X509] Deprecated Usage: ISDs SHOULD NOT use this term as a synonym for "cryptographic hash". $ onion routing (I) A system that can be used to provide both (a) data confidentiality and (b) traffic-flow confidentiality for network packets, and also provide (c) anonymity for the source of the packets. Tutorial: The source, instead of sending a packet directly to the intended destination, sends it to an "onion routing proxy" that builds an anonymous connection through several other "onion routers" to the destination. The proxy defines a route through the "onion routing network" by encapsulating the original payload in a layered data packet called an "onion", in which each layer defines the next hop in the route and each layer is also encrypted. Along the route, each onion router that receives the onion peels off one layer; decrypts that layer and reads from it the address of the next onion router on the route; pads the remaining onion to some constant size; and sends the padded onion to that next router. $ open security environment (O) /U.S. DoD/ A system environment that meets at least one of the following two conditions: (a) Application developers (including maintainers) do not have sufficient clearance or authorization to provide an acceptable presumption that they have not introduced malicious logic. (b) Configuration control does not provide sufficient assurance that applications and the equipment are protected against the introduction of malicious logic prior to and during the operation of system applications. [NCS04] (See: (first law under) Courtney's laws. Compare: closed security environment.) $ open storage (N) /U.S. Government/ "Storage of classified information within an accredited facility, but not in General Services Administration approved secure containers, while the facility is unoccupied by authorized personnel." [C4009] Shirey Informational [Page 169] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ Open Systems Interconnection (OSI) Reference Model (OSIRM) (N) A joint ISO/ITU-T standard [I7498 Part 1] for a seven-layer, architectural communication framework for interconnection of computers in networks. Tutorial: OSIRM-based standards include communication protocols that are mostly incompatible with the IPS, but also include security models, such as X.509, that are used in the Internet. The OSIRM layers, from highest to lowest, are (7) Application, (6) Presentation, (5) Session, (4) Transport, (3) Network, (2) Data Link, and (1) Physical. Usage: In other Glossary entries, OSIRM layers are referred to by number to avoid confusing them with IPS layers, which are referred to by name. Some unknown person described how the OSIRM layers correspond to the seven deadly sins: 7. Wrath: Application is always angry at the mess it sees below itself. (Hey! Who is it to be pointing fingers?) 6. Sloth: Presentation is too lazy to do anything productive by itself. 5. Lust: Session is always craving and demanding what truly belongs to Application's functionality. 4. Avarice: Transport wants all of the end-to-end functionality. (Of course, it deserves it, but life isn't fair.) 3. Gluttony: (Connection-Oriented) Network is overweight and overbearing after trying too often to eat Transport's lunch. 2. Envy: Poor Data Link is always starved for attention. (With Asynchronous Transfer Mode, maybe now it is feeling less neglected.) 1. Pride: Physical has managed to avoid much of the controversy, and nearly all of the embarrassment, suffered by the others. John G. Fletcher described how the OSIRM layers correspond to Snow White's dwarf friends: 7. Doc: Application acts as if it is in charge, but sometimes muddles its syntax. 6. Sleepy: Presentation is indolent, being guilty of the sin of Sloth. 5. Dopey: Session is confused because its charter is not very clear. 4. Grumpy: Transport is irritated because Network has encroached on Transport's turf. 3. Happy: Network smiles for the same reason that Transport is irritated. 2. Sneezy: Data Link makes loud noises in the hope of attracting attention. 1. Bashful: Physical quietly does its work, unnoticed by the Shirey Informational [Page 170] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 others. $ operational integrity (I) Synonym for "system integrity"; this synonym emphasizes the actual performance of system functions rather than just the ability to perform them. $ operational security (D) Synonym for "administrative security". (Compare: OPSEC.) Deprecated Definition: ISDs SHOULD NOT use this term as a synonym for "administrative security". Any type of security may affect system operations; therefore, the term may be misleading. Instead, use "administrative security", "communication security", "computer security", "emanations security", "personnel security", "physical security", or whatever specific type is meant. (Compare: OPSEC. See: security architecture.) $ operations security (OPSEC) (I) A process to identify, control, and protect evidence of the planning and execution of sensitive activities and operations, and thereby prevent potential adversaries from gaining knowledge of capabilities and intentions. (See: communications cover. Compare: operational security.) $ operator (I) A person who has been authorized to direct selected functions of a system. (Compare: manager.) Usage: A system operator may or may not be treated as a "user"; therefore, ISDs that use this term SHOULD state a definition for it. $ OPSEC (I) See: operations security. $ ORA See: organizational registration authority. $ Orange Book (D) Synonym for "Trusted Computer System Evaluation Criteria" [CSC001, DoD1]. Deprecated Usage: ISDs SHOULD NOT use this term as a synonym for "Trusted Computer System Evaluation Criteria" [CSC001, DoD1]. Instead, use the full, proper name of the document or, in subsequent references, the abbreviation "TCSEC". (See: (Deprecated Usage under) Green Book.) $ organizational certificate (I) A X.509 certificate in which the "subject" field contains the name of an institution or set (e.g., a business, government, Shirey Informational [Page 171] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 school, labor union, club, ethnic group, nationality, system, or group of individuals playing the same role), rather than the name of an individual person or device. (Compare: persona certificate, role certificate.) Tutorial: Such a certificate might be issued for one of the following purposes: - To enable an individual to prove membership in the organization. - To enable an individual to represent the organization, i.e., to act in its name and with it powers or permissions. (O) /MISSI/ A type of MISSI X.509 public-key certificate that is issued to support organizational message handling for the U.S. DoD's Defense Message System. $ organizational registration authority (ORA) 1. (I) /PKI/ An RA for an organization. 2. (O) /MISSI/ An end entity that (a) assists a PCA, CA, or SCA to register other end entities, by gathering, verifying, and entering data and forwarding it to the signing authority and (b) may also assist with card management functions. An ORA is a local administrative authority, and the term refers both to the role and to the person who plays that role. An ORA does not sign certificates, CRLs, or CKLs. (See: no-PIN ORA, SSO-PIN ORA, user- PIN ORA.) $ origin authentication Deprecated Term: ISDs SHOULD NOT use this term; it looks like careless use of the internationally standardized term "data origin authentication", and also could be confused with "peer entity authentication." (See: authentication.) $ origin authenticity Deprecated Term: ISDs SHOULD NOT use this term; it looks like careless use of the internationally standardized term "data origin authentication", and mixes concepts in a potentially misleading way. (See: authenticity, origin authentication.) $ OSI $ OSIRM (N) See: Open Systems Interconnection Reference Model. $ OTAR (N) See: over-the-air rekeying. $ OTP (I) See: One-Time Password. $ out of band 1a. (I) Transfer of information using a channel that is outside Shirey Informational [Page 172] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 (i.e., separate from) the main or normal channel. 1b. (I) Transfer of information using a means or method that differs from the main or normal method of communication.(See: covert channel.) Tutorial: Out-of-band mechanisms are often used to distribute shared secrets (e.g., a symmetric key) or other sensitive information items (e.g., a root key) that are needed to initialize or otherwise enable the operation of cryptography or other security mechanisms. Example: Using postal mail to distribute printed or magnetic media containing symmetric cryptographic keys for use in Internet encryption devices. (See: key distribution.) $ output feedback (OFB) (N) A block cipher mode [FP081] that modifies ECB mode to operate on plaintext segments of variable length less than or equal to the block length. Tutorial: This mode operates by directly using the algorithm's previously generated output block as the algorithm's next input block (i.e., by "feeding back" the output block) and combining (exclusive OR-ing) the output block with the next plaintext segment (of block length or less) to form the next ciphertext segment. $ outside attack (I) See: (secondary definition under) attack. Compare: outsider.) $ outsider (I) A user (usually a person) that accesses a system from a position that is outside the system's security perimeter. (Compare: authorized user, insider, unauthorized user.) Tutorial: The actions performed by an outsider in accessing the system may be either authorized or unauthorized; i.e., an outsider may act either as an authorized user or as an unauthorized user. $ over-the-air rekeying (OTAR) (N) Changing a key in a remote cryptographic device by sending a new key directly to the device via a channel that the device is protecting. [C4009] $ overload (I) See: (secondary definition under) obstruction. $ P1363 (N) See: IEEE P1363. $ PAA (O) See: policy approving authority. Shirey Informational [Page 173] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ package (N) /Common Criteria/ A reusable set of either functional or assurance components (e.g. an EAL), combined in a single unit to satisfy a set of identified security objectives. Tutorial: A package is a combination of security requirement components and is intended to be reusable in the construction of either more complex packages or protection profiles and security targets. A package expresses a set of either functional or assurance requirements that meet some particular need, expressed as a set of security objectives. Example: The seven EALs defined in Part 3 of the Common Criteria are predefined assurance packages. $ packet filter (I) See: (secondary definition under) filtering router. $ packet monkey (D) Someone who floods a system with packets, creating a denial- of-service condition for the system's users.(See: cracker.) $ pagejacking (D) A contraction of "Web page hijacking". A masquerade attack in which the attacker copies (steals) a home page or other material from the target server, rehosts the page on a server the attacker controls, and causes the rehosted page to be indexed by the major Web search services, thereby diverting browsers from the target server to the attacker's server. Deprecated Term: ISDs SHOULD NOT use this contraction. The term is not listed in most dictionaries and could confuse international readers. (See: (Deprecated Usage under) Green Book.) $ PAN (O) See: primary account number. $ PAP (I) See: Password Authentication Protocol. $ parity bit (I) A checksum that is computed on a block of bits by computing the binary sum of the individual bits in the block and then discarding all but the low-order bit of the sum. $ partitioned security mode (N) A mode of operation of an information system, wherein all users have the clearance, but not necessarily formal access authorization and need-to-know, for all data handled by the system. This mode is defined in U.S. DoD policy regarding system accreditation. [DoD2] Shirey Informational [Page 174] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ PASS (N) See: personnel authentication system string. $ passive attack (I) See: (secondary definition under) attack. $ passive wiretapping (I) A wiretapping attack that attempts only to observer communication flow and gain knowledge of the data it contains, but does not alter or otherwise affect that flow. (See: wiretapping. Compare: passive attack, active wiretapping.) $ password (I) A secret data value, usually a character string, that is presented to a system by a user to authenticate the user's identity. (See: challenge-response, PIN, simple authentication.) (O) "A character string used to authenticate an identity." [CSC2] (O) "A string of characters (letters, numbers, and other symbols) used to authenticate an identity or to verify access authorization." [FP140] (O) "A secret that a claimant memorizes and uses to authenticate his or her identity. Passwords are typically character strings." [SP63] Tutorial: A password is usually paired with a user identifier that is explicit in the authentication process, although in some cases the identifier may be implicit. A password is usually verified by matching it to a stored value held by the access control system for that identifier. Using a password as authentication information is based on assuming that the password is known only by the system entity for which the identity is being authenticated. Therefore, in a network environment where wiretapping is possible, simple authentication that relies on transmission of static (i.e., repetitively used) passwords in cleartext form is inadequate. (See: one-time password, strong authentication.) $ Password Authentication Protocol (PAP) (I) A simple authentication mechanism in PPP. In PAP, a user identifier and password are transmitted in cleartext form. [R1334] (See: CHAP.) $ password sniffing (I) Passive wiretapping, usually on a LAN, to gain knowledge of passwords. (See: (Deprecated Usage note under) sniffing.) $ path discovery (I) For a digital certificate, the process of finding a set of Shirey Informational [Page 175] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 public-key certificates that comprise a certification path from a trusted key to that specific certificate. $ path validation (I) The process of validating (a) all of the digital certificates in a certification path and (b) the required relationships between those certificates, thus validating the contents of the last certificate on the path. (See: certificate validation.) Tutorial: To promote interoperable PKI applications in the Internet, RFC 3280 specifies a detailed algorithm for validation of a certification path. $ payment card (N) /SET/ Collectively refers "to credit cards, debit cards, charge cards, and bank cards issued by a financial institution and which reflects a relationship between the cardholder and the financial institution." [SET2] $ payment gateway (O) /SET/ A system operated by an acquirer, or a third party designated by an acquirer, for the purpose of providing electronic commerce services to the merchants in support of the acquirer, and which interfaces to the acquirer to support the authorization, capture, and processing of merchant payment messages, including payment instructions from cardholders. [SET1, SET2] $ payment gateway certification authority (SET PCA) (O) /SET/ A CA that issues digital certificates to payment gateways and is operated on behalf of a payment card brand, an acquirer, or another party according to brand rules. A SET PCA issues a CRL for compromised payment gateway certificates. [SET2] (See: PCA.) $ PC card (N) A type of credit card-sized, plug-in peripheral device that was originally developed to provide memory expansion for portable computers, but is also used for other kinds of functional expansion. (See: FORTEZZA, PCMCIA.) Tutorial: The international PC Card Standard defines a non- proprietary form factor in three sizes -- Types I, II and III -- each of which have a 68-pin interface between the card and the socket into which it plugs. All three types have the same length and width, roughly the size of a credit card, but differ in their thickness from 3.3 to 10.5 mm. Examples include storage modules, modems, device interface adapters, and cryptographic modules. $ PCA Deprecated Term: ISDs SHOULD NOT use this acronym without a qualifying adjective; that would be ambiguous. (See: Internet policy certification authority, (MISSI) policy creation authority, Shirey Informational [Page 176] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 (SET) payment gateway certification authority.) $ PCMCIA (N) Personal Computer Memory Card International Association, a group of manufacturers, developers, and vendors, founded in 1989 to standardize plug-in peripheral memory cards for personal computers and now extended to deal with any technology that works in the PC Card form factor. (See: PC card.) $ PDS (N) See: protective distribution system. $ peer entity authentication (I) "The corroboration that a peer entity in an association is the one claimed." [I7498 Part 2] (See: authentication.) $ peer entity authentication service (I) A security service that verifies an identity claimed by or for a system entity in an association. (See: authentication, authentication service.) Tutorial: This service is used at the establishment of, or at times during, an association to confirm the identity of one entity to another, thus protecting against a masquerade by the first entity. However, unlike data origin authentication service, this service requires an association to exist between the two entities, and the corroboration provided by the service is valid only at the current time that the service is provided. (See: ("relationship between data integrity service and authentication services" under) data integrity service). $ PEM (I) See: Privacy Enhanced Mail. $ penetrate 1a. Circumvent a system's security protections. (See: attack, break, violation.) 1b. (I) Successfully and repeatedly gain unauthorized access to a protected system resource. [Huff] $ penetration test (I) A system test, often part of system certification, in which evaluators attempt to circumvent the security features of a system. [NCS04, SP42] (See: tiger team.) Tutorial: Penetration testing evaluates the relative vulnerability of a system to attacks and identifies methods of gaining access to a system by using tools and techniques that are available to adversaries. Testing may be performed under various constraints and conditions, including a specified level of knowledge of the system design and implementation. For a TCSEC evaluation, testers Shirey Informational [Page 177] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 are assumed to have all system design and implementation documentation, including source code, manuals, and circuit diagrams, and to work under no greater constraints than those applied to ordinary users. $ perfect forward secrecy (I) See: (usage discussion under) public-key forward secrecy. $ perimeter See: security perimeter. $ periods processing (I) A mode of system operation in which information of different sensitivities is processed at distinctly different times by the same system, with the system being properly purged or sanitized between periods. (See: color change.) Tutorial: The security mode of operation and maximum classification of data handled by the system is established for an interval of time and then is changed for the following interval of time. A period extends from the secure initialization of the system to the completion of any purging of sensitive data handled by the system during the period. $ permanent storage (I) Non-volatile media that, once written into, can never be completely erased. $ permission 1a. (I) A synonym for "authorization". (Compare: privilege.) 1b. (I) An authorization or set of authorizations to perform security-relevant functions in the context of role-based access control. [ANSI] Tutorial: A permission is a positively-stated authorization for access that (a) can be associated with one or more roles and (b) enables a user in a role to access a specified set of system resources by causing a specific set of system actions to be performed on the resources. $ persona certificate (I) An X.509 certificate issued to a system entity that wishes to use a persona to conceal its true identity when using PEM or other Internet services that depend on PKI support. (See: anonymity.) [R1422] Tutorial: PEM designers intended that (a) a CA issuing persona certificates would explicitly not be vouching for the identity of the system entity to whom the certificate is issued, (b) such certificates would be issued only by CAs subordinate to a policy CA having a policy stating that purpose (i.e., that would warn Shirey Informational [Page 178] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 relying parties that the "subject" field DN represented only a persona and not a true, vetted user identity), and (c) the CA would not need to maintain records binding the true identity of the subject to the certificate. However, the PEM designers also intended that a CA issuing persona certificates would establish procedures (d) to enable "the holder of a PERSONA certificate to request that his certificate be revoked" and (e) to ensure that it did not issue the same subject DN to multiple users. The latter condition implies that a persona certificate is not an organizational certificate unless the organization has just one member or representative. $ personal identification number (PIN) 1a. (I) A character string used as a password to gain access to a system resource. (See: authentication information.) 1b. (O) An alphanumeric code or password used to authenticate an identity. Tutorial: Despite the words "identification" and "number", a PIN seldom serves as a user identifier, and a PIN's characters are not necessarily all numeric. Retail banking applications use 4-digit numeric user PINs, but the FORTEZZA PC card uses 12-character alphanumeric SSO PINs. Thus, a better name for this concept would have been "personnel authentication system string" (PASS), in which case an alphanumeric character string for this purpose would have been called, obviously, a "PASSword". $ personality 1. (I) Synonym for "principal". 2. (O) /MISSI/ A set of MISSI X.509 public-key certificates that have the same subject DN, together with their associated private keys and usage specifications, that is stored on a FORTEZZA PC card to support a role played by the card's user. Tutorial: When a card's user selects a personality to use in a FORTEZZA-aware application, the data determines behavior traits (the personality) of the application. A card's user may have multiple personalities on the card. Each has a "personality label", a user-friendly character string that applications can display to the user for selecting or changing the personality to be used. For example, a military user's card might contain three personalities: GENERAL HALFTRACK, COMMANDER FORT SWAMPY, and NEW YEAR'S EVE PARTY CHAIRMAN. Each personality includes one or more certificates of different types (such as DSA versus RSA), for different purposes (such as digital signature versus encryption), or with different authorizations. Shirey Informational [Page 179] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ personnel authentication system string (PASS) (N) See: (Tutorial under) personal identification number. $ personnel security (I) Procedures to ensure that persons who access a system have proper clearance, authorization, and need-to-know as required by the system's security policy. $ PGP(trademark) (O) See: Pretty Good Privacy(trademark). $ Photuris (I) A UDP-based, key establishment protocol for session keys, designed for use with the IPsec protocols AH and ESP. Superseded by IKE. $ phreaking (D) A contraction of "telephone breaking". An attack on or penetration of a telephone system or, by extension, any other communication or information system. [Raym] Deprecated Term: ISDs SHOULD NOT use this contraction; it is not listed in most dictionaries and could confuse international readers. $ physical security (I) Tangible means of preventing unauthorized physical access to a system. Examples: Fences, walls, and other barriers; locks, safes, and vaults; dogs and armed guards; sensors and alarm bells. [FP031, R1455] $ piggyback attack (I) A form of active wiretapping in which the attacker gains access to a system via intervals of inactivity in another user's legitimate communication connection. Sometimes called a "between- the-lines" attack. (See: hijack attack, man-in-the-middle attack.) Deprecated Usage: This term could confuse international readers; therefore, ISDs that use it SHOULD state a definition for it. $ PIN (I) See: personal identification number. $ ping of death (D) A denial-of-service attack that sends an improperly large ICMP echo request packet (a "ping") with the intent of causing the destination system to fail. (See: ping sweep, teardrop.) Deprecated Term: ISDs SHOULD NOT use this term; instead, use "ping packet overflow attack" or some other term that is specific with regard to the attack mechanism. Shirey Informational [Page 180] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 Tutorial: This attack seeks to exploit an implementation vulnerability. The IP specification requires hosts to be prepared to accept datagrams of up to 576 octets, but also permits IP datagrams to be up to 65,535 octets long. If an IP implementation does not properly handle very long IP packets, the ping packet may overflow the input buffer and cause a fatal system error. $ ping sweep (I) An attack that sends ICMP echo requests ("pings") to a range of IP addresses, with the goal of finding hosts that can be probed for vulnerabilities. (See: ping of death. Compare: port scan.) $ PKCS (N) See: Public-Key Cryptography Standards. $ PKCS #5 (N) A standard [PKC05, R2898] from the PKCS series; defines a method for encrypting an octet string with a secret key derived from a password. Tutorial: Although the method can be used for arbitrary octet strings, its intended primary application in public-key cryptography is for encrypting private keys when transferring them from one computer system to another, as described in PKCS #8. $ PKCS #7 (N) A standard [PKC07, R2315] from the PKCS series; defines a syntax for data that may have cryptography applied to it, such as for digital signatures and digital envelopes. (See: CMS.) $ PKCS #10 (N) A standard [PKC10] from the PKCS series; defines a syntax for requests for public-key certificates. (See: certification request.) Tutorial: A PKCS #10 request contains a DN and a public key, and may contain other attributes, and is signed by the entity making the request. The request is sent to a CA, who converts it to an X.509 public-key certificate (or some other form), and returns it, possibly in PKCS #7 format. $ PKCS #11 (N) A standard [PKC11] from the PKCS series; defines a software CAPI called Cryptoki (an abbreviation of "cryptographic token interface", pronounced "CRYPTO-key") for devices that hold cryptographic information and perform cryptographic functions. $ PKI (I) See: public-key infrastructure. $ PKIX 1a. (I) A contraction of "Public-Key Infrastructure (X.509)", the Shirey Informational [Page 181] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 name of the IETF working group that is specifying an architecture [R3280] and set of protocols [R2510] to provide X.509-based PKI services for the Internet. 1b. (I) A collective name for that Internet PKI architecture and associated set of protocols. Tutorial: The goal of PKIX is to facilitate the use of X.509 public-key certificates in multiple Internet applications and to promote interoperability between different implementations that use those certificates. The resulting PKI is intended to provide a framework that supports a range of trust and hierarchy environments and a range of usage environments. PKIX specifies (a) profiles of the v3 X.509 public-key certificate standards and the v2 X.509 CRL standards for the Internet, (b) operational protocols used by relying parties to obtain information such as certificates or certificate status, (c) management protocols used by system entities to exchange information needed for proper management of the PKI, and (d) information about certificate policies and CPSs, covering the areas of PKI security not directly addressed in the rest of PKIX. $ PKIX private extension (I) PKIX defines an private extension to identify an on-line verification service supporting the issuing CA. $ plain text (I) /noun/ Data that is input to and transformed by an encryption process, or that is output from a decryption process. (Compare: plaintext.) Tutorial: Usually, the plain text that is the input to an encryption operation is clear text. But in some cases, the input is cipher text that was output from another encryption operation. (See: superencryption.) $ plaintext 1a. (I) /adjective/ Referring to plain text. (See: plain text.) 1b. (D) /noun/ A synonym for plain text. Deprecated Usage: To avoid ambiguity, ISDs SHOULD differentiate between the noun phrase "plain text" and adjective "plaintext". $ PLI (I) See: Private Line Interface. $ Point-to-Point Protocol (PPP) (I) An Internet Standard protocol (RFC 1661) for encapsulation and full-duplex transportation of protocol data packets in OSIRM layer 3 over an OSIRM layer 2 link between two peers, and for multiplexing different layer 3 protocols over the same link. Shirey Informational [Page 182] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 Includes optional negotiation to select and use a peer entity authentication protocol to authenticate the peers to each other before they exchange layer 3 data. (See: CHAP, EAP, PAP.) $ Point-to-Point Tunneling Protocol (PPTP) (I) An Internet client-server protocol (RFC 2637) (originally developed by Ascend and Microsoft) that enables a dial-up user to create a virtual extension of the dial-up link across a network by tunneling PPP over IP. (See: L2TP.) Tutorial: PPP can encapsulate any IPS network layer protocol or OSIRM layer 3 protocol. Therefore, PPTP does not specify security services; it depends on protocols above and below it to provide any needed security. PPTP makes it possible to divorce the location of the initial dial-up server (i.e., the PPTP Access Concentrator, the client, which runs on a special-purpose host) from the location at which the dial-up protocol (PPP) connection is terminated and access to the network is provided (i.e., at the PPTP Network Server, which runs on a general-purpose host). $ policy 1a. (I) A plan or course of action that is stated for a system or organization and is intended to affect and direct the decisions and deeds of that entity's components or members. (See: security policy.) 1b. (O) A definite goal, course, or method of action to guide and determine present and future decisions, that is implemented or executed within a particular context, such as within a business unit. [R3198] Deprecated Usage: ISDs SHOULD NOT use "policy" as an abbreviation for either "security policy" or "certificate policy". Instead, to avoid misunderstanding, use a fully qualified term, at least at the point of first usage. Tutorial: The introduction of new technology to replace traditional systems can result in new systems being deployed without adequate policy definition and before the implications of the new technology are fully understand. In some cases, it can be difficult to establish policies for new technology before the technology has been operationally tested and evaluated. Thus, policy changes tend to lag behind technological changes, such that either old policies impede the technical innovation, or the new technology is deployed without adequate policies to govern its use. When new technology changes the ways that things are done, new "procedures" must be defined to establish operational guidelines for using the technology and achieving satisfactory results, and new "practices" must be established for managing new systems and monitoring results. Practices and procedures are more directly Shirey Informational [Page 183] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 coupled to actual systems and business operations than are polices, which tend to be more abstract. - "Practices" define how a system is to be managed and what controls are in place to monitor the system and detect abnormal behavior or quality problems. Practices are established to ensure that a system is managed in compliance with stated policies. System audits are primarily concerned with whether or not practices are being followed. Auditors evaluate the controls to make sure they conform to accepted industry standards, and then confirm that controls are in place and that control measurements are being gathered. Audit trails are examples of control measurements that are recorded as part of system operations. - "Procedures" define how a system is operated, and relate closely to issues of what technology is used, who the operators are, and how the system is deployed physically. Procedures define both normal and abnormal operating circumstances. For every control defined by a practice statement, there should be corresponding procedures to implement the control and provide ongoing measurement of the control parameters. Conversely, procedures require management practices to insure consistent and correct operational behavior. $ policy approving authority (PAA) (O) /MISSI/ The top-level signing authority of a MISSI certification hierarchy. The term refers both to that authoritative office or role and to the person who plays that role. (See: root registry.) Tutorial: A PAA registers MISSI PCAs and signs their X.509 public- key certificates. A PAA issues CRLs but does not issue a CKL. A PAA may issue cross-certificates to other PAAs. $ policy certification authority (Internet PCA) (I) An X.509-compliant CA at the second level of the Internet certification hierarchy, under the IPRA. Each PCA operates in accordance with its published security policy (see: certificate policy, CPS) and within constraints established by the IPRA for all PCAs. [R1422]. (See: policy creation authority.) $ policy creation authority (MISSI PCA) (O) /MISSI/ The second level of a MISSI certification hierarchy; the administrative root of a security policy domain of MISSI users and other, subsidiary authorities. The term refers both to that authoritative office or role and to the person who fills that office. (See: policy certification authority.) Tutorial: A MISSI PCA's certificate is issued by a PAA. The PCA registers the CAs in its domain, defines their configurations, and issues their X.509 public-key certificates. (The PCA may also issue certificates for SCAs, ORAs, and other end entities, but a PCA does not usually do this.) The PCA periodically issues CRLs Shirey Informational [Page 184] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 and CKLs for its domain. $ Policy Management Authority (N) Canadian usage: An organization responsible for PKI oversight and policy management in the Government of Canada. $ policy mapping (I) "Recognizing that, when a CA in one domain certifies a CA in another domain, a particular certificate policy in the second domain may be considered by the authority of the first domain to be equivalent (but not necessarily identical in all respects) to a particular certificate policy in the first domain." [X509] $ POP3 (I) See: Post Office Protocol, version 3. $ POP3 APOP (I) A POP3 command (i.e., a transaction type, or a protocol- within-a-protocol) by which a POP3 client optionally uses a keyed hash (based on MD5) to authenticate itself to a POP3 server and, depending on the server implementation, to protect against replay attacks. (See: CRAM, POP3 AUTH, IMAP4 AUTHENTICATE.) Tutorial: The server includes a unique timestamp in its greeting to the client. The subsequent APOP command sent by the client to the server contains the client's name and the hash result of applying MD5 to a string formed from both the timestamp and a shared secret that is known only to the client and the server. APOP was designed to provide an alternative to using POP3's USER and PASS (i.e., password) command pair, in which the client sends a cleartext password to the server. $ POP3 AUTH (I) A POP3 command [R1734] (i.e., a transaction type, or a protocol-within-a-protocol) by which a POP3 client optionally proposes a mechanism to a POP3 server to authenticate the client to the server and provide other security services. (See: POP3 APOP, IMAP4 AUTHENTICATE.) 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 used by POP3 AUTH are those used by IMAP4. $ port scan (I) An attack that sends client requests to a range of server port addresses on a host, with the goal of finding an active port and exploiting a known vulnerability of that service. (Compare: ping sweep.) $ positive authorization Shirey Informational [Page 185] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 (I) The principle that a security architecture should be designed so that access to system resources is granted only in a positive way; i.e., in the absence of an explicit authorization that grants access, the default action shall be to refuse access. $ POSIX (N) Portable Operating System Interface for Computer Environments, a standard [FP151, IS9945-1] (originally IEEE Standard P1003.1) that defines an operating system interface and environment to support application portability at the source code level. It is intended to be used by both application developers and system implementers. Tutorial: P1003.1 supports security functionality like that on most UNIX systems, including discretionary access control and privileges. IEEE Draft Standard P1003.6 specifies additional functionality not provided in the base standard, including (a) discretionary access control, (b) audit trail mechanisms, (c) privilege mechanisms, (d) mandatory access control, and (e) information label mechanisms. $ Post Office Protocol, version 3 (POP3) (I) An Internet Standard protocol (RFC 1939) by which a client workstation can dynamically access a mailbox on a server host to retrieve mail messages that the server has received and is holding for the client. (See: IMAP4.) Tutorial: POP3 has mechanisms for optionally authenticating a client to a server and providing other security services. (See: POP3 APOP, POP3 AUTH.) $ PPP (I) See: Point-to-Point Protocol. $ PPTP (I) See: Point-to-Point Tunneling Protocol. $ preauthorization (I) A CAW capability that enables certification requests to be automatically validated against data provided in advance to the CA by an authorizing entity. $ precedence (N) A designation assigned to a communication (i.e., packet, message, data stream, connection, etc.) by the originator to state the importance or urgency of that communication versus other communications, and thus indicate to the transmission system the relative order of handling, and indicate to the receiver the order in which the communication is to be noted. [F1037] (See: availability, critical, preemption.) Example: The "Precedence" subfield of the "Type of Service" field Shirey Informational [Page 186] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 of the IPv4 header supports the following designations (in descending order of importance): 111 Network Control, 110 Internetwork Control, 101 CRITIC/ECP (Critical Intelligence Communication/Emergency Command Precedence), 100 Flash Override, 011 Flash, 010 Immediate, 001 Priority, and 000 Routine. These designations were adopted from U.S. DoD systems that existed before ARPANET. $ preemption (N) The seizure, usually automatic, of system resources that are being used to serve a lower precedence communication, in order to serve immediately a higher precedence communication. [F1037] $ Pretty Good Privacy(trademark) (PGP(trademark)) (O) Trademarks of Network Associates, Inc., referring to a computer program (and related protocols) that uses cryptography to provide data security for electronic mail and other applications on the Internet. (Compare: MOSS, MSP, PEM, S/MIME.) Tutorial: PGP encrypts messages with IDEA in CFB mode, distributes the IDEA keys by encrypting them with RSA, and creates digital signatures on messages with MD5 and RSA. To establish ownership of public keys, PGP depends on the web of trust. $ primary account number (PAN) (O) /SET/ "The assigned number that identifies the card issuer and cardholder. This account number is composed of an issuer identification number, an individual account number identification, and an accompanying check digit as defined by ISO 7812-1985." [SET2, IS7812] (See: bank identification number.) Tutorial: The PAN is embossed, encoded, or both on a magnetic- strip-based credit card. The PAN identifies the issuer to which a transaction is to be routed and the account to which it is to be applied unless specific instructions indicate otherwise. The authority that assigns the BIN part of the PAN is the American Bankers Association. $ principal (I) A specific identity claimed by a user when accessing a system. Usage: Usually understood to be an identity that is registered in and authenticated by the system; equivalent to the notion of login account identifier. Each principal is normally assigned to a single user, but a single user may be assigned (or attempt to use) more than one principal. Each principal can spawn one or more subjects, but each subject is associated with only one principal. (Compare: role, subject, user.) (N) /Kerberos/ A uniquely named client or server instance that participates in a network communication. Shirey Informational [Page 187] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ privacy 1. (I) The right of an entity (normally a person), acting in its own behalf, to determine the degree to which it will interact with its environment, including the degree to which the entity is willing to share information about itself with others. (See: HIPAA, Privacy Act of 1974. Compare: anonymity, data confidentiality.) 2. (O) "The right of individuals to control or influence what information related to them may be collected and stored and by whom and to whom that information may be disclosed." [I7498 Part 2] 3. (D) Synonym for "data confidentiality". Deprecated Definition: ISDs SHOULD NOT use this term as a synonym for "data confidentiality" or "data confidentiality service", which are different concepts. Privacy is a reason for security rather than a kind of security. For example, a system that stores personal data needs to protect the data to prevent harm, embarrassment, inconvenience, or unfairness to any person about whom data is maintained, and to protect the person's privacy. For that reason, the system may need to provide data confidentiality service. $ Privacy Act of 1974 (O) A U.S. Federal law (Section 552a of Title 5, United States Code) that seeks to balance the U.S. Government's need to maintain data about individuals with the rights of individuals to be protected against unwarranted invasions of their privacy stemming from federal agencies' collection, maintenance, use, and disclosure of personal data. (See: privacy.) Tutorial: In 1974, the U.S. Congress was concerned with the potential for abuses that could arise from the Government's increasing use of computers to store and retrieve personal data. Therefore, the Act has four basic policy objectives: - To restrict disclosure of personally identifiable records maintained by Federal agencies. - To grant individuals increased rights of access to Federal agency records maintained on themselves. - To grant individuals the right to seek amendment of agency records maintained on themselves upon a showing that the records are not accurate, relevant, timely, or complete. - To establish a code of "fair information practices" that requires agencies to comply with statutory norms for collection, maintenance, and dissemination of records. $ Privacy Enhanced Mail (PEM) (I) An Internet protocol to provide data confidentiality, data integrity, and data origin authentication for electronic mail. [R1421, R1422]. (Compare: MOSS, MSP, PGP, S/MIME.) Shirey Informational [Page 188] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 Tutorial: PEM encrypts messages with DES in CBC mode, provides key distribution of DES keys by encrypting them with RSA, and signs messages with RSA over either MD2 or MD5. To establish ownership of public keys, PEM uses a certification hierarchy, with X.509 public-key certificates and X.509 CRLs that are signed with RSA and MD2. PEM is designed to be compatible with a wide range of key management methods, but is limited to specifying security services only for text messages and, like MOSS, has not been widely implemented in the Internet. $ private component (I) Synonym for "private key". Deprecated Usage: In most cases, ISDs SHOULD NOT use this term; instead, to avoid confusing readers, use "private key". However, the term MAY be used when discussing a key pair; e.g., "A key pair has a public component and a private component." $ private extension (I) See: (secondary definition under) extension. $ private key 1. (I) The secret component of a pair of cryptographic keys used for asymmetric cryptography. (See: key pair, public key.) 2. (O) In a public key cryptosystem, "that key of a user's key pair which is known only by that user." [X509] $ Private Line Interface (PLI) (I) The first end-to-end packet encryption system for a computer network, developed by BBN starting in 1975 for the U.S. DoD, incorporating Government-furnished, military-grade COMSEC equipment (TSEC/KG-34). [B1822] (Compare: IPLI.) $ privilege 1a. (I) A synonym for "authorization". (Compare: permission.) 1b. (I) An authorization or set of authorizations to perform security-relevant functions in the context of computer operating systems. Tutorial: A privilege can be modeled as (a) an action acting upon (b) an object that contains (c) attributes that can be constrained by (d) domains. $ privilege management infrastructure (O) "The infrastructure able to support the management of privileges in support of a comprehensive authorization service and in relationship with a" PKI; i.e., processes concerned with Shirey Informational [Page 189] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 attribute certificates. [X509] Deprecated Usage: ISDs SHOULD NOT use this term; this definition is vague and there is no consensus on a more specific definition. $ privileged process (I) An computer process that is authorized (and, therefore, trusted) to perform some security-relevant functions that ordinary processes are not. (See: privilege, trusted process.) $ probe (I) /verb/ To access an information system in an attempt to gather information about the system for the purpose of circumventing the system's security measures. $ procedural security (I) Synonym for "administrative security". Deprecated Definition: ISDs SHOULD NOT use this term as a synonym for "administrative security". Any type of security may involve procedures; therefore, the term may be misleading. Instead, use "administrative security", "communication security", "computer security", "emanations security", "personnel security", "physical security", or whatever specific type is meant. (See: security architecture.) $ profile See: certificate profile, protection profile. $ proof-of-possession protocol (I) A protocol whereby a system entity proves to another that it possesses and controls a cryptographic key or other secret information. (See: zero-knowledge proof.) $ proprietary (I) Refers to information (or other property) that is owned by an individual or organization and for which the use is restricted by that entity. $ protected checksum (I) A checksum that is computed for a data object by means that protect against active attacks that would attempt to change the checksum to make it match changes made to the data object. (See: digital signature, keyed hash, (discussion under) checksum. $ protective packaging (N) Packaging techniques for COMSEC material that discourage penetration, reveal a penetration has occurred or was attempted, or inhibit viewing or copying of keying material prior to the time it is exposed for use. [C4008] (Compare: QUADRANT. See: tamper evident, tamper resistant.) Shirey Informational [Page 190] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ protection authority (I) See: (secondary definition under) Internet Protocol Security Option. $ protection profile (N) /Common Criteria/ An implementation-independent set of security requirements for a category of targets of evaluation that meet specific consumer needs. [CCIB] Example: [IDSAN]. Tutorial: A protection profile (PP) is intended to be a reusable statement of product security needs, which are known to be useful and effective, for a set of information technology security products that could be built. A PP contains a set of security requirements, preferably taken from the catalogs in Parts 2 and 3 of the Common Criteria, and should include an EAL. A PP could be developed by user communities, product developers, or any other parties interested in defining a common set of requirements. $ protection ring (I) One of a hierarchy of privileged operation modes of a system that gives certain access rights to processes authorized to operate in that mode. (See: Multics.) $ protective distribution system (PDS) (N) A wireline or fiber-optic communication system used to transmit cleartext classified information through an area of lesser classification or control. [N7003] $ protocol 1a. (I) A set of rules (i.e., formats and procedures) to implement and control some type of association (e.g., communication) between systems. Example: Internet Protocol. 1b. (I) A series of ordered computing and communication steps that are performed by two or more system entities to achieve a joint objective. [A9042] $ protocol suite (I) A complementary collection of communication protocols used in a computer network. (See: Internet, OSI.) $ proxy 1. (I) A computer process that acts on behalf of a user or client. 2. (I) A computer process -- often used as, or as part of, a firewall -- that relays a protocol between client and server computer systems, by appearing to the client to be the server and appearing to the server to be the client. (See: SOCKS.) Tutorial: In a firewall, a proxy server usually runs on a bastion host, which may support proxies for several protocols (e.g., FTP, HTTP, and TELNET). Instead of a client in the protected enclave Shirey Informational [Page 191] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 connecting directly to an external server, the internal client connects to the proxy server which in turn connects to the external server. The proxy server waits for a request from inside the firewall, forwards the request to the server outside the firewall, gets the response, then sends the response back to the client. The proxy may be transparent to the clients, or they may need to connect first to the proxy server, and then use that association to also initiate a connection to the real server. Proxies are generally preferred over SOCKS for their ability to perform caching, high-level logging, and access control. A proxy can provide security service beyond that which is normally part of the relayed protocol, such as access control based on peer entity authentication of clients, or peer entity authentication of servers when clients do not have that capability. A proxy at OSIRM layer 7 can also provide finer-grained security service than can a filtering router at layer 3. For example, an FTP proxy could permit transfers out of, but not into, a protected network. $ proxy certificate (I) An X.509 public-key certificate derived from a end-entity certificate, or from another proxy certificate, for the purpose of establishing proxies and delegating authorizations in the context of a PKI-based authentication system. [R3280] Tutorial: A proxy certificate has the following properties: - It contains an critical extension that (a) identifies it as a proxy certificate and (b) may contain a certification path length constraint and policy constraints. - It contains the public component of a key pair that is distinct from that associated with any other certificate. - It is signed by the private component of a key pair that is associated with an end-entity certificate or another proxy certificate. - Its associated private key can be used to sign only other proxy certificates (not end-entity certificates). - Its "subject" DN is derived from its "issuer" DN and is unique. - Its "issuer" DN is the "subject" DN of an end-entity certificate or another proxy certificate. $ pseudorandom (I) A sequence of values that appears to be random (i.e., unpredictable) but is actually generated by a deterministic algorithm. (See: compression, random, random number generator.) $ pseudorandom number generator See: random number generator. $ public component (I) Synonym for "public key". Deprecated Usage: In most cases, ISDs SHOULD NOT use this term; to Shirey Informational [Page 192] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 avoid confusing readers, use "private key" instead. However, the term MAY be used when discussing a key pair; e.g., "A key pair has a public component and a private component." $ public key 1. (I) The publicly-disclosable component of a pair of cryptographic keys used for asymmetric cryptography. (See: key pair, private key.) 2. (O) In a public key cryptosystem, "that key of a user's key pair which is publicly known." [X509] $ public-key certificate 1. (I) A digital certificate that binds a system entity's identity to a public key value, and possibly to additional, secondary data items; i.e., a digitally-signed data structure that attests to the ownership of a public key. (See: X.509 public-key certificate.) 2. (O) "The public key of a user, together with some other information, rendered unforgeable by encipherment with the private key of the certification authority which issued it." [X509] Tutorial: The digital signature on a public-key certificate is unforgeable. Thus, the certificate can be published, such as by posting it in a directory, without the directory having to protect the certificate's data integrity. $ public-key cryptography (I) The popular synonym for "asymmetric cryptography". $ Public-Key Cryptography Standards (PKCS) (N) A series of specifications published by RSA Laboratories for data structures and algorithm used in basic applications of asymmetric cryptography. (See: PKCS #5 through PKCS #11.) Tutorial: The PKCS were begun in 1991 in cooperation with industry and academia, originally including Apple, Digital, Lotus, Microsoft, Northern Telecom, Sun, and MIT. Today, the specifications are widely used, but they are not sanctioned by an official standards organization, such as ANSI, ITU-T, or IETF. RSA Laboratories retains sole decision-making authority over the PKCS. $ public-key forward secrecy (PFS) (I) For a key agreement protocol based on asymmetric cryptography, the property that ensures that a session key derived from a set of long-term public and private keys will not be compromised if one of the private keys is compromised in the future. Usage: Some existing RFCs use the term "perfect forward secrecy" but either do not define it or do not define it precisely. While preparing this Glossary, we tried to find a good definition for that term, but found this to be a muddled area. Experts did not Shirey Informational [Page 193] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 agree. For all practical purposes, the literature defines "perfect forward secrecy" by stating the Diffie-Hellman algorithm. The term "public-key forward secrecy" (suggested by Hilarie Orman) and the "I" definition stated for it here were crafted to be compatible with current Internet documents, yet be narrow and leave room for improved terminology. Challenge to the Internet security community: We need a taxonomy -- a family of mutually exclusive and collectively exhaustive terms and definitions to cover the basic properties discussed here -- for the full range of cryptographic algorithms and protocols used in Internet Standards: Involvement of session keys vs. long-term keys: Experts disagree about the basic ideas involved: - One concept of "forward secrecy" is that, given observations of the operation of a key establishment protocol up to time t, and given some of the session keys derived from those protocol runs, you cannot derive unknown past session keys or future session keys. - A related property is that, given observations of the protocol and knowledge of the derived session keys, you cannot derive one or more of the long-term private keys. - The "I" definition presented above involves a third concept of "forward secrecy" that refers to the effect of the compromise of long-term keys. - All three concepts involve the idea that a compromise of "this" encryption key is not supposed to compromise the "next" one. There also is the idea that compromise of a single key will compromise only the data protected by the single key. In Internet literature, the focus has been on protection against decryption of back traffic in the event of a compromise of secret key material held by one or both parties to a communication. Forward vs. backward: Experts are unhappy with the word "forward", because compromise of "this" encryption key also is not supposed to compromise the "previous" one, which is "backward" rather than forward. In S/KEY, if the key used at time t is compromised, then all keys used prior to that are compromised. If the "long-term" key (i.e., the base of the hashing scheme) is compromised, then all keys past and future are compromised; thus, you could say that S/KEY has neither forward nor backward secrecy. Asymmetric cryptography vs. symmetric: Experts disagree about forward secrecy in the context of symmetric cryptographic systems. In the absence of asymmetric cryptography, compromise of any long- term key seems to compromise any session key derived from the long-term key. For example, Kerberos isn't forward secret, because compromising a client's password (thus compromising the key shared by the client and the authentication server) compromises future session keys shared by the client and the ticket-granting server. Shirey Informational [Page 194] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 Ordinary forward secrecy vs. "perfect" forward secret: Experts disagree about the difference between these two. Some say there is no difference, and some say that the initial naming was unfortunate and suggest dropping the word "perfect". Some suggest using "forward secrecy" for the case where one long-term private key is compromised, and adding "perfect" for when both private keys (or, when the protocol is multi-party, all private keys) are compromised. Acknowledgements: Bill Burr, Burt Kaliski, Steve Kent, Paul Van Oorschot, Michael Wiener, and, especially, Hilarie Orman contributed ideas to this discussion. $ public-key infrastructure (PKI) 1. (I) A system of CAs (and, optionally, RAs and other supporting servers and agents) that perform some set of certificate management, archive management, key management, and token management functions for a community of users in an application of asymmetric cryptography. (See: hierarchical PKI, mesh PKI, security management infrastructure, trust-file PKI.) 2. (I) /PKIX/ The set of hardware, software, people, policies, and procedures needed to create, manage, store, distribute, and revoke digital certificates based on asymmetric cryptography. Tutorial: The core PKI functions are (a) to register users and issue their public-key certificates, (b) to revoke certificates when required, and (c) to archive data needed to validate certificates at a much later time. Key pairs for data confidentiality may be generated (and perhaps escrowed) by CAs or RAs, but requiring a PKI client to generate its own digital signature key pair helps maintain system integrity of the cryptographic system, because then only the client ever possesses the private key it uses. Also, an authority may be established to approve or coordinate CPSs, which are security policies under which components of a PKI operate. A number of other servers and agents may support the core PKI, and PKI clients may obtain services from them. The full range of such services is not yet fully understood and is evolving, but supporting roles may include archive agent, certified delivery agent, confirmation agent, digital notary, directory, key escrow agent, key generation agent, naming agent who ensures that issuers and subjects have unique identifiers within the PKI, repository, ticket-granting agent, and time stamp agent. $ purge (I) Use degaussing or other means to render (magnetically) stored data unusable and unrecoverable by any means, including laboratory methods. [C4009] (See: zeroize. Compare: erase, sanitize.) Shirey Informational [Page 195] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ QUADRANT (O) /U.S. Government/ Short name for technology and methods that protect cryptographic equipment by making the equipment tamper- resistant. [C4009] (Compare: protective packaging, TEMPEST.) Tutorial: Equipment cannot be made completely tamper-proof, but it can be made tamper-resistant or tamper-evident. $ qualified certificate (I) A public-key certificate that has the primary purpose of identifying a person with a high level of assurance, where the certificate meets some qualification requirements defined by an applicable legal framework, such as the European Directive on Electronic Signature [EU-ESDIR]. [R3739]. $ RA (I) See: registration authority. $ RA domains (I) A capability of a CAW that allows a CA to divide the responsibility for certificate requests among multiple RAs. Tutorial: This capability might be used to restrict access to private authorization data that is provided with a certificate request, and to distribute the responsibility to review and approve certificate requests in high volume environments. RA domains might segregate certificate requests according to an attribute of the certificate subject, such as an organizational unit. $ RADIUS (I) See: Remote Authentication Dial-In User Service. $ Rainbow Series (O) A set of more than 30 technical and policy documents with colored covers, issued by the NCSC, that discuss in detail the TCSEC and provide guidance for meeting and applying the criteria. (See: Green Book, Orange Book, Red Book, Yellow Book.) $ random (I) In essence, "random" means "unpredictable". [SP22, Knut, R1750] (See: cryptographic key, pseudorandom.) - "Random sequence": A sequence in which each successive value is obtained merely by chance and does not depend on the preceding values of the sequence. In a random sequence of bits, each bit is unpredictable; i.e., (a) the probability of each bit being a "0" or "1" is 1/2, and (b) the value of each bit is independent of any other bit in the sequence. - "Random value": A individual value that is unpredictable; i.e., each value in the total population of possibilities has equal probability of being selected. Shirey Informational [Page 196] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ random number generator (I) A process that is invoked to generate a random sequence of values (usually a sequence of bits) or an individual random value. Tutorial: There are two basic types of generators. [SP22] - (True) random number generator: Uses one or more non- deterministic bit sources (usually physical phenomena; e.g., electrical circuit noise, timing of user processes such as key strokes or mouse movements, semiconductor quantum effects) and some processing function that formats the bits; and outputs an sequence of values that is unpredictable and uniformly distributed. - Pseudorandom number generator: Uses a deterministic computational process (usually implemented by software) that has one or more inputs called "seeds"; and outputs a sequence of values that appears to be random according to specified statistical tests. $ RBAC (N) See: role-based access control, rule-based access control. Deprecated Usage: This abbreviation is ambiguous; therefore, ISDs that use it SHOULD state a definition for it. $ RC2, RC4, RC6 (N) See: Rivest Cipher #2, #4, #6. $ read (I) A fundamental operation in an information system that results only in the flow of information from an object to a subject. (See: access mode.) $ realm (O) /Kerberos/ The domain of authority of a Kerberos server (consisting of an authentication server and a ticket-granting server), including the Kerberized clients and the Kerberized application servers $ recovery 1. (I) /cryptography/ The process of learning or obtaining cryptographic data or plain text through cryptanalysis. (See: key recovery, data recovery.) 2a. (I) /system integrity/ The process of restoring a secure state in a system after there has been an accidental failure or a successful attack. (See: system integrity.) 2b. (I) /system integrity/ The process of restoring an information system's assets and operation following damage or destruction. (See: contingency plan.) Shirey Informational [Page 197] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ RED 1. (I) Designation for data that consists only of clear text, and for information system equipment items and facilities that handle only clear text. Example: "RED key". (Compare: BLACK. See: color change, RED/BLACK separation.) Derivation: From the practice of marking equipment with colors to prevent operational errors. 2. (O) /U.S. Government/ Designation applied to information systems, and to associated areas, circuits, components, and equipment, "in which unencrypted national security information is being processed." [C4009] $ RED/BLACK separation (I) An architectural concept for cryptographic systems that strictly separates the parts of a system that handle plain text (i.e., RED information) from the parts that handle cipher text (i.e., BLACK information). (See: BLACK, RED.) $ Red Book (D) Synonym for "Trusted Network Interpretation of the Trusted Computer System Evaluation Criteria" [NCS05]. Deprecated Term: ISDs SHOULD NOT use this term as a synonym for "Trusted Network Interpretation of the Trusted Computer System Evaluation Criteria". Instead, use the full proper name of the document or, in subsequent references, a more conventional abbreviation. (See: TCSEC, Rainbow Series, (Deprecated Usage under) Green Book.) $ RED key (I) A key that is usable in its present form without any additional decryption. (Compare: BLACK key. See: RED.) $ reference monitor (I) "An access control concept that refers to an abstract machine that mediates all accesses to objects by subjects." [NCS04] (See: security kernel.) Tutorial: This concept was described in the Anderson report. A reference monitor should be (a) complete (i.e., it mediates every access), (b) isolated (i.e., it cannot be modified by other system entities), and (c) verifiable (i.e., small enough to be subjected to analysis and tests to ensure that it is correct). $ reflection attack (I) An attack in which a valid data transmission is maliciously or fraudulently retransmitted, either by an adversary who intercepts the data or by its originator. (Compare: replay attack.) Shirey Informational [Page 198] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 $ registration 1. (I) A system process that (a) initializes an identity in the system, (b) establishes an identifier for that identity, (c) may associate authentication information with that identifier, and (d) may issue an identifier credential (depending on the type of authentication mechanism being used). (See: authentication information, credential, identifier, identity.) 2. (I) /PKI/ An administrative act or process whereby an entity's name and other attributes are established for the first time at a CA, prior to the CA issuing a digital certificate that has the entity's name as the subject. (See: registration authority.) Tutorial: Registration may be accomplished either directly, by the CA, or indirectly, by a separate RA. An entity is presented to the CA or RA, and the authority either records the name(s) claimed for the entity or assigns the entity's name(s). The authority also determines and records other attributes of the entity that are to be bound in a certificate (such as a public key or authorizations) or maintained in the authority's database (such as street address and telephone number). The authority is responsible, possibly assisted by an RA, for verifying the entity's identity and vetting the other attributes, in accordance with the CA's CPS. Among the registration issues that a CPS may address are the following [R2527]: - How a claimed identity and other attributes are verified. - How organization affiliation or representation is verified. - What forms of names are permitted, such as X.500 DN, domain name, or IP address. - Whether names are required to be meaningful or unique, and within what domain. - How naming disputes are resolved, including the role of trademarks. - Whether certificates are issued to entities that are not persons. - Whether a person is required to appear before the CA or RA, or can instead be represented by an agent. - Whether and how an entity proves possession of the private key matching a public key. $ registration authority (RA) 1. (I) An optional PKI entity (separate from the CAs) that does not sign either digital certificates or CRLs but has responsibility for recording or verifying some or all of the information (particularly the identities of subjects) needed by a CA to issue certificates and CRLs and to perform other certificate management functions. (See: ORA, registration.) 2. (I) /PKIX/ An optional PKI component, separate from the CA(s). The functions that the RA performs will vary from case to case but may include identity authentication and name assignment, key Shirey Informational [Page 199] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 generation and archiving of key pairs, token distribution, and revocation reporting. [R2510] Tutorial: Sometimes, a CA may perform all certificate management functions for all end users for which the CA signs certificates. Other times, such as in a large or geographically dispersed community, it may be necessary or desirable to offload secondary CA functions and delegate them to an assistant, while the CA retains the primary functions (signing certificates and CRLs). The tasks that are delegated to an RA by a CA may include personal authentication, name assignment, token distribution, revocation reporting, key generation, and archiving. An RA is an optional PKI component, separate from the CA, that is assigned secondary functions. The duties assigned to RAs vary from case to case but may include the following: - Verifying a subject's identity, i.e., performing personal authentication functions. - Assigning a name to a subject. (See: distinguished name.) - Verifying that a subject is entitled to have the attributes requested for a certificate. - Verifying that a subject possesses the private key that matches the public key requested for a certificate. - Performing functions beyond mere registration, such as generating key pairs, distributing tokens, and handling revocation reports. (Such functions may be assigned to a PKI component that is separate from both the CA and the RA.) 3. (O) /SET/ "An independent third-party organization that processes payment card applications for multiple payment card brands and forwards applications to the appropriate financial institutions." [SET2] $ regrade (I) Deliberately change the classification level of information in an authorized manner. (See: downgrade, upgrade.) $ rekey (I) Change the value of a cryptographic key that is being used in an application of a cryptographic system. (See: certificate rekey.) Tutorial: Rekey is required at the end of a cryptoperiod or key lifetime. $ reliability (I) The ability of a system to perform a required function under stated conditions for a specified period of time. (Compare: availability, survivability.) $ reliable human review (I) Any manual, automated, or hybrid process or procedure for opening and reviewing a digital object, such as text or an image, Shirey Informational [Page 200] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 to determine whether the object may be permitted, according to some security policy, to be transferred across a controlled interface. (See: guard.) $ relying party (I) Synonym for "certificate user". Usage: Used in a legal context to mean a recipient of a certificate who acts in reliance on that certificate. (See: ABA Guidelines.) $ remanence (I) Residual information that can be recovered from a storage medium after clearing. (See: clear, magnetic remanence, purge.) $ Remote Authentication Dial-In User Service (RADIUS) (I) An Internet protocol [R2138] for carrying dial-in users' authentication information and configuration information between a shared, centralized authentication server (the RADIUS server) and a network access server (the RADIUS client) that needs to authenticate the users of its network access ports. (See: TACACS.) Tutorial: A user of the RADIUS client presents authentication information to the client, and the client passes that information to the RADIUS server. The server authenticates the client using a shared secret value, then checks the user's authentication information, and finally returns to the client all authorization and configuration information needed by the client to deliver service to the user. $ renew See: certificate renewal. $ replay attack (I) An attack in which a valid data transmission is maliciously or fraudulently repeated, either by the originator or by an adversary who intercepts the data and retransmits it, possibly as part of a masquerade attack. (See: active wiretapping. Compare: reflection attack.) $ repository 1. (I) A system for storing and distributing digital certificates and related information (including CRLs, CPSs, and certificate policies) to certificate users. (See: archive, directory.) 2. (O) "A trustworthy system for storing and retrieving certificates or other information relevant to certificates." [ABA] Tutorial: A certificate is published to those who might need it by putting it in a repository. The repository usually is a publicly accessible, on-line server. In the Federal Public-key Infrastructure, for example, the expected repository is a Shirey Informational [Page 201] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 directory that uses LDAP, but also may be the X.500 Directory that uses DAP, or an HTTP server, or an FTP server that permits anonymous login. $ repudiation 1. (I) Denial by a system entity that was involved in an association (especially an association that transfers information) of having participated in the relationship. (See: accountability, non-repudiation service.) 2. (I) A type of threat action whereby an entity deceives another by falsely denying responsibility for an act. (See: deception.) Usage: This type of threat action includes the following subtypes: - False denial of origin: Action whereby an originator denies responsibility for sending data. - False denial of receipt: Action whereby a recipient denies receiving and possessing data. 3. (O) /OSIRM/ "Denial by one of the entities involved in a communication of having participated in all or part of the communication." [I7498 Part 2] $ Request for Comment (RFC) (I) One of the documents in the archival series that is the official channel for ISDs and other publications of the Internet Engineering Steering Group, the Internet Architecture Board, and the Internet community in general. [R2026, R2223] (See: Internet Standard.) Deprecated Usage: This term is NOT a synonym for "Internet Standard". $ residual risk (I) The portion of an original risk or set of risks that remains after countermeasures have been applied. (Compare: acceptable risk, risk analysis.) $ restore See: card restore. $ revocation See: certificate revocation. $ revocation date (N) /X.509/ In a CRL entry, a date-time field that states when the certificate revocation occurred, i.e., when the CA declared the digital certificate to be invalid. (See: invalidity date.) Tutorial: The revocation date may not resolve some disputes because, in the worst case, all signatures made during the validity period of the certificate may have to be considered Shirey Informational [Page 202] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 invalid. However, it may be desirable to treat a digital signature as valid even though the private key used to sign was compromised after the signing. If more is known about when the compromise actually occurred, a second date-time, an "invalidity date", can be included in an extension of the CRL entry. $ revocation list See: certificate revocation list. $ revoke (I) See: certificate revocation. $ RFC (I) See: Request for Comment. $ Rijndael (I) A block cipher, designed by Joan Daemen and Vincent Rijmen as a candidate algorithm for the AES. [Daem] $ risk 1. (I) An expectation of loss expressed as the probability that a particular threat will exploit a particular vulnerability with a particular harmful result. 2. (O) /SET/ "The possibility of loss because of one or more threats to information (not to be confused with financial or business risk)." [SET2] $ risk analysis (I) An assessment process that systematically (a) identifies valuable system resources and threats to those resources, (b) quantifies loss exposures (i.e., loss potential) based on estimated frequencies and costs of occurrence, and (c) (optionally) recommends how to allocate resources to countermeasures so as to minimize total exposure. (See: risk management.) Tutorial: There are four basic options for dealing with a risk [SP30]: - Risk avoidance: Eliminate the risk either by countering the threat or removing the vulnerability. - Risk transference: Shift the risk to another system or system entity, such as by buying insurance to compensate for loss. - Risk limitation: Limit the risk by implementing controls that minimize the resulting loss. - Risk assumption: Accept the potential for loss and continue operating the system. Usually, it is financially and technically infeasible to avoid or transfer all risks (see: (first corollary of second law under) Courtney's laws), and so some residual risk will remain, even after all available countermeasures have been deployed (see: Shirey Informational [Page 203] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 (second corollary of second law under) Courtney's laws). Thus, a risk analysis typically lists risks in order of cost and criticality, thereby determining where countermeasures should be applied first. [FP031, R2196] In some contexts, it is infeasible to do a risk analysis because needed data and resources are not available, or it is inadvisable. Instead, answers to questions about threats and risks may be already built into basic institutional security policies. For example, U.S. DoD policies for data confidentiality "do not explicitly itemize the range of expected threats" but instead "reflect an operational approach ... by stating the particular management controls that must be used to achieve [confidentiality] severe risk in itself, and avoid the risk of poor security design implicit in taking a fresh approach to each new problem". [NRC91] $ risk management 1. (I) The process of identifying, measuring, and controlling (i.e., mitigating) risks in information systems so as to reduce the risks to a level commensurate with the value of the assets protected. (See: risk analysis.) 2. (I) The process of controlling uncertain events that may affect information system resources. 3. (O) "The total process of identifying, controlling, and mitigating information system-Drelated risks. It includes risk assessment; cost-benefit analysis; and the selection, implementation, test, and security evaluation of safeguards. This overall system security review considers both effectiveness and efficiency, including impact on the mission and constraints due to policy, regulations, and laws." [SP30] $ Rivest Cipher #2 (RC2) (N) A proprietary, variable-key-length block cipher invented by Ron Rivest for RSA Data Security, Inc. $ Rivest Cipher #4 (RC4) (N) A proprietary, variable-key-length stream cipher invented by Ron Rivest for RSA Data Security, Inc. $ Rivest Cipher #6 (RC6) (N) A block cipher with 128-bit or higher key size; invented by Ron Rivest for RSA Data Security, Inc. A finalist in the competition for AES. $ Rivest-Shamir-Adleman (RSA) (N) An algorithm for asymmetric cryptography, invented in 1977 by Ron Rivest, Adi Shamir, and Leonard Adleman [RSA78]. Tutorial: RSA uses exponentiation modulo the product of two large prime numbers. The difficulty of breaking RSA is believed to be Shirey Informational [Page 204] Internet-Draft Internet Security Glossary, Version 2 20 July 2004 equivalent to the difficulty of factoring integers that are the product of two large prime numbers of approximately equal size. To create an RSA key pair, randomly choose tw