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PKIX Working Group R. Housley (SPYRUS)
Internet Draft W. Ford (Nortel)
D. Solo (BBN)
expires in six months February June 1996
Internet Public Key Infrastructure
Part I: X.509 Certificate and CRL Profile
<draft-ietf-pkix-ipki-part1-01.txt>
<draft-ietf-pkix-ipki-part1-02.txt>
Status of this Memo
This document is an Internet-Draft. 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
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To learn the current status of any Internet-Draft, please check the
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Abstract
This is the second draft of the Internet Public Key Infrastructure
X.509 Certificate and CRL Profile. This document Since the first version was sections 1
through 5
distributed, ISO has completed work on X.509 Version 3 Certificates
and section 11 X.509 Version 2 Certificate Revocation Lists (CRLs). Many of draft-ietf-pkix-ipki-00.txt. That
original document has been divided into four parts; it was simply too
big. This is the first part. Many changes are
Internet community requirements that were in the result previous version of
discussion at the Dallas IETF
this document have been included in December 1995 and discussion the final ISO document. As a
result, this document has gotten simpler. Please send comments on
this document to the ietf-pkix@tandem.com mail list. The intent of this document is to
generate further productive discussion and build concensus.
1 Executive Summary
<< Write this last. >>
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2 Requirements and Assumptions
Goal is to develop a profile and associated management structure to
facilitate the adoption/use of X.509 certificates within Internet
applications for those communities wishing to make use of X.509
technology. Such applications may include WWW, electronic mail, user
authentication, electronic payment systems, IPSEC, as well as others.
In order to relieve some of the obstacles to using X.509
certificates, this document defines a profile to promote the
development of certificate management systems; development of
application tools; and interoperability determined by policy, as
opposed to syntax.
Some communities will need to supplement, or possibly replace, this
profile in order to meet the requirements of specialized application
domains or environments with additional authorization, assurance, or
operational requirements. However, for basic applications, common
representations of frequently used attributes are defined so that
application developers can obtain necessary information without
regard to the issuer of a particular certificate or certificate
revocation list (CRL).
As supplemental authorization and attribute management tools emerge,
such as attribute certificates, it may be appropriate to limit the
authenticated attributes that are included in a certificate. These
other management tools may be more appropriate method of conveying
many authenticated attributes.
2.1 Communication and Topology
The users of certificates will operate in a wide range of
environments with respect to their communication topology, especially
users of secure electronic mail. This profile supports users without
high bandwidth, real-time IP connectivity, or high connection
availablity. In addition, the profile allows for the presence of
firewall or other filtered communication.
2.2 Acceptability Criteria
The goal of the Internet Public Key Infrstructure (PKI) is to meet
the needs of deterministic, automated identification, authentication,
access control, and authorization functions. Support for these
services determines the attributes contained in the certificate as
well as the ancillary control information in the certificate such as
policy data and certification path constraints.
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2.3 User Expectations
Users of the Internet PKI are people and processes who use client
software and are the subjects named in certificates. These uses
include readers and writers of electronic mail, the clients for WWW
browsers, and the key manager for IPSEC within a router. This
profile recognizes the limitations of the platforms these users
employ and the sophistication/attentiveness of the users themselves.
This manifests itself in minimal user configuration responsibility
(e.g., root keys, rules), explicit platform usage constraints within
the certificate, certification path constraints which shield the user
from many malicious actions, and applications which sensibly automate
validation functions.
2.4 Administrator Expectations
As with users, the Internet PKI profile is structured to support the
individuals who generally operate Certification Authorities (CAs).
Providing administrators with unbounded choices increases the chances
that a subtle CA administrator mistake will result in broad
compromise. Also, unbounded choices greatly complicates the software
that must process and validate the certificates created by the CA.
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3 Overview of Approach
Following is a simplified view of the architectural model assumed by
the PKIX specifications.
+---+
| C | +------------+
| e | <-------------------->| End entity |
| r | Operational +------------+
| t | transactions ^
| | and management | Management
| / | transactions | transactions
| | |
| C | PKI users v
| R | -------+-------+--------+------
| L | PKI management ^ ^
| | entities | |
| | v |
| R | +------+ |
| e | <-------------- | RA | <-----+ |
| p | certificate | | | |
| o | publish +------+ | |
| s | | |
| i | v v
| t | +------------+
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| o | <--------------------------| CA |
| r | certificate publish +------------+
| y | CRL publish ^
| | |
+---+ | Management
| transactions
v
+------+
| CA |
+------+
Figure 1 - PKI Entities
The components in this model are:
end entity: user of PKI certificates and/or end user system that
the PKI certifies;
CA: certification authority;
RA: registration authority, i.e., an optional system to
which a CA delegates certain manaagement functions;
repository: a system or collection of distributed systems that
store certificates and CRLs and serves as a means of
distributing these certificates and CRLs to end
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entities.
3.1 X.509 Version 3 Certificate
Application of public key technology requires the user of a public
key to be confident that the public key belongs to the correct remote
subject (person or system) with which an encryption or digital
signature mechanism will be used. This confidence is obtained
through the use of public key certificates, which are data structures
that bind public key values to subject identities. The binding is
achieved by having a trusted certification authority (CA) digitally
sign each certificate. A certificate has a limited valid lifetime
which is indicated in its signed contents. Because a certificate's
signature and timeliness can be independently checked by a
certificate-using client, certificates can be distributed via
untrusted communications and server systems, and can be cached in
unsecured storage in certificate-using systems.
The standard known as ITU-T X.509 (formerly CCITT X.509) or ISO/IEC
9594-8, which was first published in 1988 as part of the X.500
Directory recommendations, defines a standard certificate format. The
certificate format in the 1988 standard is called the version 1 (v1)
format. When X.500 was revised in 1993, two more fields were added,
resulting in the version 2 (v2) format. These two fields are used to
support directory access control.
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The Internet Privacy Enhanced Mail (PEM) proposals, published in
1993, include specifications for a public key infrastructure based on
X.509 v1 certificates [RFC 1422]. The experience gained in attempts
to deploy RFC 1422 made it clear that the v1 and v2 certificate
formats are deficient in several respects. Most importantly, more
fields were needed to carry information which PEM design and
implementation experience has proven necessary. In response to these
new requirements, ISO/IEC and ANSI X9 developed the X.509 version 3
(v3) certificate format. The v3 format extends the v2 format by
adding provision for additional extension fields. Particular
extension field types may be specified in standards or may be defined
and registered by any organization or community. In August 1995, June 1996,
standardization of the basic v3 format was completed [ISO TC]. [X.509-AM].
ISO/IEC and ANSI X9 have also developed a set of standard extensions
for use in the v3 extensions field [ISO DAM, ANSI X9.55]. [X.509-AM][X9.55]. These
extensions can convey such data as additional subject identification
information, key attribute information, policy information, and
certification path constraints.
However, the ISO/IEC and ANSI standard extensions are very broad in
their applicability. In order to develop interoperable
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implementations of X.509 v3 systems for Internet use, it is necessary
to specify a profile for use of the X.509 v3 extensions tailored for
the Internet. It is one goal of this document to specify a profile
for Internet WWW, electronic mail, and IPSEC applications.
Environments with additional requirements may build on this profile
or may replace it.
3.2 Certification Paths and Trust
A user of a security service requiring knowledge of a public key
generally needs to obtain and validate a certificate containing the
required public key. If the public-key user does not already hold an
assured copy of the public key of the CA that signed the certificate,
then it might need an additional certificate to obtain that public
key. In general, a chain of multiple certificates may be needed,
comprising a certificate of the public key owner (the end entity)
signed by one CA, and zero or more additional certificates of CAs
signed by other CAs. Such chains, called certification paths, are
required because a public key user is only initialized with a limited
number (often one) of assured CA public keys.
There are different ways in which CAs might be configured in order
for public key users to be able to find certification paths. For
PEM, RFC 1422 defined a rigid hierarchical structure of CAs. There
are three types of PEM certification authority:
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(a) Internet Policy Registration Authority (IPRA): This authority,
operated under the auspices of the Internet Society, acts as the root
of the PEM certification hierarchy at level 1. It issues
certificates only for the next level of authorities, PCAs. All
certification paths start with the IPRA.
(b) Policy Certification Authorities (PCAs): PCAs are at level 2 of
the hierarchy, each PCA being certified by the IPRA. A PCA must
establish and publish a statement of its policy with respect to
certifying users or subordinate certification authorities. Distinct
PCAs aim to satisfy different user needs. For example, one PCA (an
organizational PCA) might support the general electronic mail needs
of commercial organizations, and another PCA (a high-assurance PCA)
might have a more stringent policy designed for satisfying legally
binding signature requirements.
(c) Certification Authorities (CAs): CAs are at level 3 of the
hierarchy and can also be at lower levels. Those at level 3 are
certified by PCAs. CAs represent, for example, particular
organizations, particular organizational units (e.g., departments,
groups, sections), or particular geographical areas.
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RFC 1422 furthermore has a name subordination rule which requires
that a CA can only issue certificates for entities whose names are
subordinate (in the X.500 naming tree) to the name of the CA itself.
The trust associated with a PEM certification path is implied by the
PCA name. The name subordination rule ensures that CAs below the PCA
are sensibly constrained as to the set of subordinate entities they
can certify (e.g., a CA for an organization can only certify entities
in that organization's name tree). Certificate user systems are able
to mechanically check that the name subordination rule has been
followed.
The RFC 1422 CA hierarchical model has been found to have several
deficiencies, including:
(a) The pure top-down hierarchy, with all ertification paths
starting from the root, is too restrictive for many purposes. For
some applications, verification of certification paths should start
with a public key of a CA in a user's own domain, rather than
mandating that verification commence at the top of a hierarchy. In
many environments, the local domain is often the most trusted. Also,
initialization and key-pair-update operations can be more effectively
conducted between an end entity and a local management system.
(b) The name subordination rule introduces undesirable constraints
upon the X.500 naming system an organization may use.
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(c) Use of the PCA concept requires knowledge of individual PCAs to
be built into certificate chain verification logic. In the
particular case of Internet mail, this is not a major problem -- the
PCA name can always be displayed to the human user who can make a
decision as to what trust to imply from a particular chain. However,
in many commercial applications, such as electronic commerce or EDI,
operator intervention to make policy decisions is impractical. The
process needs to be automated to a much higher degree. In fact, the
full process of certificate chain processing needs to be
implementable in trusted software.
Because of the above shortcomings, it is proposed that more flexible
CA structures than the RFC 1422 hierarchy be supported by the PKIX
specifications. In fact, the main reason for the structural
restrictions imposed by RFC 1422 was the restricted certificate
format provided with X.509 v1. With X.509 v3, most of the
requirements addressed by RFC 1422 can be addressed using certificate
extensions, without a need to restrict the CA structures used. In
particular, the certificate extensions relating to certificate
policies obviate the need for PCAs and the constraint extensions
obviate the need for the name subordination rule.
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3.3 Revocation
When a certificate is issued, it is expected to be in use for its
entire validity period. However, various circumstances may cause a
certificate to become invalid prior to the expiration of the validity
period. Such circumstances might include change of name, change of
association between subject and CA (e.g., an employee terminates
employment with an organization), and compromise or suspected
compromise of the corresponding private key. Under such
circumstances, the CA needs to revoke the certificate.
X.509 defines one method of certificate revocation. This method
involves each CA periodically issuing a signed data structure called
a certificate revocation list (CRL). A CRL is a time stamped list
identifying revoked certificates which is signed by a CA and made
freely available in a public repository. Each revoked certificate is
identified in a CRL by its certificate serial number. When a
certificate-using system uses a certificate (e.g., for verifying a
remote user's digital signature), that system not only checks the
certificate signature and validity but also acquires a suitably-
recent CRL and checks that the certificate serial number is not on
that CRL. The meaning of "suitably-recent" may vary with local
policy, but it usually means the most recently-issued CRL. A CA
issues a new CRL on a regular periodic basis (e.g., hourly, daily, or
weekly). Entries are added to CRLs as revocations occur, and an
entry may be removed when the certificate expiration date is reached.
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An advantage of this revocation method is that CRLs may be
distributed by exactly the same means as certificates themselves,
namely, via untrusted communications and server systems.
One limitation of the CRL revocation method, using untrusted
communications and servers, is that the time granularity of
revocation is limited to the CRL issue period. For example, if a
revocation is reported now, that revocation will not be reliably
notified to certificate-using systems until the next periodic CRL is
issued -- this may be up to one hour, one day, or one week depending
on the frequency that the CA issues CRLs.
Another potential problem with CRLs is the risk of a CRL growing to
an entirely unacceptable size. In the 1988 and 1993 versions of
X.509, the CRL for the end-user certificates needed to cover the
entire population of end-users for one CA. It is desirable to allow
such populations to be in the range of thousands, tens of thousands,
or possibly even hundreds of thousands of users. The end-user CRL is
therefore at risk of growing to such sizes, which present major
communication and storage overhead problems. With the version 2 CRL
format, introduced along with the v3 certificate format, it becomes
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possible to arbitrarily divide the population of certificates for one
CA into a number of partitions, each partition being associated with
one CRL distribution point (e.g., directory entry or URL) from which
CRLs are distributed. Therefore, the maximum CRL size can be
controlled by a CA. Separate CRL distribution points can also exist
for different revocation reasons. For example, routine revocations
(e.g., name change) may be placed on a different CRL to revocations
resulting from suspected key compromises, and policy may specify that
the latter CRL be updated and issued more frequently than the former.
As with the X.509 v3 certificate format, in order to facilitate
interoperable implementations from multiple vendors, the X.509 v2 CRL
format needs to be profiled for Internet use. It is one goal of this
document to specify such profiles.
Furthermore, it is recognized that on-line methods of revocation
notification may be applicable in some environments as an alternative
to the X.509 CRL. On-line revocation checking eliminates the latency
between a revocation report and CRL the next issue. Once the
revocation is reported, any query to the on- line service will
correctly reflect the certificate validation impacts of the
revocation. Therefore, this document will also consider standard
approaches to on-line revocation notification.
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3.4 Operational Protocols
Operational protocols are required to deliver certificates and CRLs
to certificate using client systems. Provision is needed for a
variety of different means of certificate and CRL delivery, including
request/delivery procedures based on E-mail, http, X.500, and
WHOIS++. These specifications include definitions of, and/or
references to, message formats and procedures for supporting all of
the above operational environments, including definitions of or
references to appropriate MIME content types.
3.5 Management Protocols
Management protocols are required to support on-line interactions
between Public Key Infrastructure (PKI) components. For example,
management protocol might be used between a CA and a client system
with which a key pair is associated, or between two CAs which cross-
certify each other. The set of functions which potentially need to
be supported by management protocols include:
(a) registration: This is the process whereby a user first makes
itself known to a CA, prior to that CA issuing a certificate or
certificates for that user.
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(b) initialization: Before a client system can operate securely it
is necessary to install in it necessary key materials which have the
appropriate relationship with keys stored elsewhere in the
infrastructure. For example, the client needs to be securely
initialized with the public key of a CA, to be used in validating
certificate paths. Furthermore, a client typically needs to be
initialized with its own key pair(s).
(c) certification: This is the process in which a CA issues a
certificate for a user's public key, and returns that certificate to
the user's client system and/or posts that certificate in a public
repository.
(d) key pair recovery: As an option, user client key materials
(e.g., a user's private key used for encryption purposes) may be
backed up by a CA or a key backup system associated with a CA. If a
user needs to recover these backed up key materials (e.g., as a
result of a forgotten password or a lost key chain file), an on-line
protocol exchange may be needed to support such recovery.
(e) key pair update: All key pairs need to be updated regularly,
i.e., replaced with a new key pair, and new certificates issued.
(f) revocation request: An authorized person advises a CA of an
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abnormal situation requiring certificate revocation.
(g) cross-certification: Two CAs exchange the information necessary
to establish cross-certificates between those CAs.
Note that on-line protocols are not the only way of implementing the
above functions. For all functions there are off-line methods of
achieving the same result, and this specification does not mandate
use of on- line protocols. For example, when hardware tokens are
used, many of the functions may be achieved through as part of the
physical token delivery. Furthermore, some of the above functions
may be combined into one protocol exchange. In particular, two or
more of the registration, initialization, and certification functions
can be combined into one protocol exchange.
Part 3 of the PKIX series of specifications defines a set of standard
message formats supporting the above functions. The protocols for
conveying these messages in different environments (on-line, e-mail,
and WWW) are also specified.
4 Certificate and Certificate Extensions Profile
As described above, the
The goal of this section document is to create a profile for X.509 v3
certificates that will foster interoperability and a reusable public
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key infrastructure. To achieve Since the publication of earlier versions of
this goal, some
assumptions need to be draft, substantial changes have been made about to the nature of information Amendment
[X.509-AM] to be
included along X.509 defining version 3 and certificate extensions.
Those changes have brought the base document into close alignment
with guidelines for how extensibility will be
employed. the recommendations of earlier versions of this draft. As a
result, this document provides a concise profile rather than
attempting to recreate the Amendment as a standalone document.
Certificates may be used in a wide range of applications and
environments covering a broad spectrum of interoperability goals and
a broader spectrum of operational and assurance requirements. The
goal of this section document is to establish a common baseline for generic
applications requiring broad interoperability and limited special
purpose requirements. In particular, the emphasis will be on
supporting the use of X.509 v3 certificates for informal internet
electronic mail, IPSEC, and WWW applications. This section defines a
baseline set of information, common locations within a Other efforts are
looking at certificate profiles for this information, and common representations for this
information. Environments with additional requirements may build on
this profile or may replace it. payment systems.
4.1 Basic Certificate Fields
The X.509 v3 certificate Basic basic syntax is as follows. For signature
calculation, the certificate is ASN.1 DER encoded [reference X.509?]. using the ASN.1 distinguished
encoding rules (DER) [X.208]. ASN.1 DER encoding is a tag, length,
value encoding system for each element.
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Certificate ::= SIGNED SEQUENCE {
tbsCertificate TBSCertificate,
signatureAlgorithm AlgorithmIdentifier,
signature BIT STRING }
TBSCertificate ::= SEQUENCE {
version [0] Version DEFAULT v1,
serialNumber CertificateSerialNumber,
signature AlgorithmIdentifier,
issuer Name,
validity Validity,
subject Name,
subjectPublicKeyInfo SubjectPublicKeyInfo,
issuerUniqueID [1] IMPLICIT UniqueIdentifier OPTIONAL,
-- If present, version must be v2 or v3
subjectUniqueID [2] IMPLICIT UniqueIdentifier OPTIONAL,
-- If present, version must be v2 or v3
extensions [3] Extensions OPTIONAL
-- If present, version must be v3
} }
Version ::= INTEGER { v1(0), v2(1), v3(2) }
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CertificateSerialNumber ::= INTEGER
Validity ::= SEQUENCE {
notBefore UTCTime,
notAfter UTCTime }
UniqueIdentifier ::= BIT STRING
SubjectPublicKeyInfo ::= SEQUENCE {
algorithm AlgorithmIdentifier,
subjectPublicKey BIT STRING }
Extensions ::= SEQUENCE OF Extension
Extension ::= SEQUENCE {
extnID OBJECT IDENTIFIER,
critical BOOLEAN DEFAULT FALSE,
extnValue OCTET STRING }
The following items describe a proposed use of the X.509 v3
certificate for the Internet.
4.1.1 Version
This field describes the version of the encoded certificate. When
extensions are used, as expected in this profile, use X.509 version 3
(value is 2). If no extensions are present, but a UniqueIdentifier
is present, use version 2 (value is 1). If only basic fields are
present, use version 1 (the value is absent). omitted from the certificate as
the default value).
Implementations should be prepared to accept any version certificate.
In particular, at a minimum, implementations should recognize version
3 certificates; determine whether any critical extensions are
present; and accept certificates without critical extensions even if
they don't recognize any extensions. A certificate with an
unrecognized critical extension must always be rejected.
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Generation of version 2 certificates is not expected by CAs using
implementations based on this profile.
4.1.2 Serial number
The serial number is an integer assigned by the CA certification
authority to each certificate. It must be unique for each
certificate issued by a given CA (i.e., the issuer name and serial
number identify a unique certificate).
<< Do we want to define a maximum value for the serial number? >>
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4.1.3 Signature
This field contains the algorithm identifier for the algorithm used
by the CA to sign the certificate. Section 7.2 of this profile lists the supported
signature algorithms.
4.1.4 Issuer Name
The issuer name (combined with the IssuerUniqueID, if present)
provides a globally unique identifier of the authority signing identifies the
certificate. Reliance on entity who has signed (and issued the IssuerUniqueID is strongly discouraged.
certificate). The syntax of issuer identity may be carried in the issuer name
field and/or the issuerAltName extension. If identity information is an X.500 distinguished name. A name
present only in the certificate may provide semantic information, issuerAltName extension, then the issuer name may provide a
reference to
be an external information store or service, provides a
unique identifier, may provide authorization information, or may
provide a basis for managing the CA relationships empty sequence and certificate
paths (other purposes are also possible). This strawman suggests
that the issuer (and subject) name fields must provide a globally
unique identifier. In addition, they should contain semantic
information identifying the issuer/subject (e.g. a full name,
organization name, etc.). Access information will be provided in a
separate issuerAltName extension (when other than via X.500 directory) and internet
specific identities (electronic mail address, DNS name, and URLs)
will must be carried in alternative name extensions.
critical.
<< Further discussion of naming guidelines for internet use is
needed. Should we say anything about name constraints here? >>
4.1.5 Validity
This field indicates the dates on which the certificate becomes valid
(notBefore) and on which the certificate ceases to be valid
(notAfter).
The It is strongly recommended that UTCTime (Coordinated Universal Time) values included in this
field shall be
expressed in Greenwich Mean Time (Zulu) and include
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granularity to the minute, even though finer granularity can be
expressed in the UTCTime format. That is, UTCTime should be
expressed as YYMMDDHHMMZ.
Implementors are warned that no DER is defined for UTCTime, thus
transformation between local time representations and the DER
transfer syntax must be performed carefully when computing the hash
value for a certificate signature. For example, a UTCTime value
which includes explict, zero values for seconds will not produce the
same hash value as one in which the use seconds (i.e., times
are YYMMDDHHMMZ). If seconds are omitted. UTCTime
expresses the value of used, a year modulo 100, with no indication value of
century, hence comparisons involving dates in different centuries
must 00 seconds should
never be performed with care. encoded.
4.1.6 Subject Name
The purpose of the subject name (combined identifies the entity associated with the SubjectUniqueID,
if present) is to provide a unique identifier of public key
stored in the subject of the
certificate. Reliance on the IssuerUniqueID is discouraged. public key field. The
syntax of subject identity may be
carried in the subject name field and/or the subjectAltName extension. If
identity information is an X.500 distinguished name. The
discussion present only in section 4.1.4 on issuer names applies to subject names
as well.
<< How do we bind the subjectAltName extension
(e.g., a public key bound only to an Internet e-mail address? One
alternative is to make Subject Name as a unique identifier. Or, it
could be legal to have a null Subject Name. Either way email address or URI), then the
SubjectAltName contains subject
name may be an empty sequence and the e-mail address. subjectAltName extension must
be critical.
<< Should we say anything about name constraints here? >>
4.1.7 Subject Public Key Info
This field is used to carry the public key and identify the algorithm
with which the key is used.
4.1.8 Unique Identifiers
The subject and issuer unique identifier are present in the
certificate to handle the possibility of reuse of subject and/or
issuer names over time. This profile strongly recommends that names not be reused, thus
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reused and that Internet certificates not make use of unique
identifiers. CA's conforming to this profile do should not
make use of generate
certificates with unique identifiers. Applications conforming to
this profile should be capable of parsing unique identifiers and
making comparisons.
4.2 Certificate Extensions
The extensions already defined by ANSI X9 and ISO for X.509 v3 certificates provide methods for
associating additional attributes with users or public keys and keys, for
managing the certification
hierarchy. hierarchy, and for managing CRL
distribution. The X.509 v3 certificate format also allows
communities to define private extensions to carry information unique
to those
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designated as critical or non-critical. A certificate using system
(an application validating a certificate) must reject the certificate
if it encounters a critical extension it does not recognize. A non-
critical extension may be ignored if it is not recognized. The
following presents recommended extensions used within Internet
certificates and standard locations for information. Communities may
elect to use additional extensions; however, caution should be
exercised in adopting any critical extensions in certificates which
might be used in a general context.
<< Need to add table of OIDs for all
The extensions from X.509 and X9.55.
Say which referenced below are allowed defined in this profile, detail in the X.509
Amendment along with the specification of syntax and which are prohibited object
identifiers. Because the intent is to align exactly with those
definitions, the material is not reproduced here. The following
sections describe Internet profiling decisions and Internet private
extensions.
<< Once finalized, the certificate ASN.1 definition will be included
in an appendix to this profile. document. >>
4.2.1 Subject Alternative Name Standard Extensions
4.2.1.1 Authority Key Identifier
The altNames authority key identifier extension allows additional identities provides a means of
identifying the particular public key used to sign a certificate.
The identification can be bound to based on either the key identifier (the
subject of key identifier in the certificate. Defined options include an rfc822 issuer's certificate) or on the issuer
name (electronic mail address), a DNS name, and a URL. Each of these
are IA5 strings. Multiple instances may be included. Whenever such
identities are to be bound in a certificate, the subject alternative
name (or issuer alternative name) field shall be used. A form of
such an identifier may also be present in the subject distinguished
name; however, the altName field is the preferred location for
finding such information. serial number. The following definition key identifier method is an enhanced version of the X9.55
definition of GeneralName. recommended in
this profile. This definition is anticipated to extension would be used
in the X.509 Amendment.
rfc822Name, dNSName, url, and ipAddress are name forms expected where an issuer has
multiple signing keys (either due to be
used with this profile. Such names are subject multiple concurrent key pairs or
due to the basic
constraint changeover). In general, this extension for issuers which may restrict the names a given
CA can certify (see section on Basic Constraint extension).
The use of otherName should not be used included in conjunction with this
profile.
AltNames ::= SEQUENCE OF GeneralName
GeneralName ::= CHOICE {
otherName [0] INSTANCE OF OTHER-NAME,
rfc822Name [1] IA5String,
dNSName [2] IA5String,
x400Address [3] ORAddress,
directoryName [4] Name,
ediPartyName [5] IA5String,
certificates.
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url [6] IA5String,
ipAddress [7] OCTET STRING }
4.2.2 Issuer Alternative Name
As with 4.2.1, this
4.2.1.2 Subject Key Identifier
The subject key identifier extension is provides a means of identifying
the particular public key used in an application. Where a reference
to bind Internet style
identities to the issuer name.
4.2.3 Certificate Policies
The certificatePolicies extension contains a public key identifier is needed (as with an Authority Key
Identifier) and one or more object
identifiers (OIDs). Each OID indicates the policy under which is not included in the
certificate has been issued. This profile expects that associated certificate, a simple OID
will
SHA-1 hash of the subject public key shall be present in each PolicyElementInfo. used. The qualifier within the
PolicyElementInfo should hash shall
be absent.
Implementations processing certificate policy fields are expected to
have lists of those policies which they will accept. The
implementations compare the policy identifier(s) in the certificate
to that list. This field provides information to be used at calculated over the
discretion value (excluding tag and length) of a relying party. In contrast, the policy identifier(s)
subject public key field in the keyUsageRestriction is a mandate by the issuer that a
certificate certificate. This extension should
be used only in particular environments.
CertificatePolicies ::= SEQUENCE OF PolicyInformation
PolicyInformation ::= SEQUENCE OF PolicyElementInfo
PolicyElementInfo ::= SEQUENCE {
policyElementId OBJECT IDENTIFIER,
qualifier ANY DEFINED BY policyElementId OPTIONAL }
4.2.4 marked non-critical.
4.2.1.3 Key Attributes Usage
The keyAttributes extension contains information about the key itself
including a unique key identifier, a key usage period (lifetime of
the private key as opposed to the lifetime of extension defines the certificate), and
an intended key usage. The Internet purpose (e.g., encipherment,
signature, certificate should use signing) of the
keyAttributes extension and contain a key identifier and private key
validity to aid contained in system management. the
certificate. The key usage field in this
extension restriction might be employed when a
multipurpose key is intended to be advisory (as contrasted with the key
usage restriction extension which imposes mandatory restrictions).
The restricted (e.g., when an RSA key usage field in this extension should be
used to differentiate
certificates containing public keys only for validating CA certificate
signatures, signing or only for validating CA CRL signatures, and validating
signatures on on-line transactions. However, the nonrepudiation and
dataEncipherment values should not key encipherment). The profile
recommends that when used, this be used. Where a reference to marked as a
public key identifier is needed (as with an Authority critical extension.
4.2.1.4 Private Key ID) and is
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not included in an attribute in Usage Period
This profile recommends against the associated certificate, an SHA-1
hash use of the public key shall be used.
The GeneralizedTime values included in this field shall be expressed
in Greenwich Mean Time (Zulu) and include granularity extension. CA's
conforming to the minute,
even though finer granularity can be expressed in the GeneralizedTime
format. That is, GeneralizedTime this profile should be expressed as
YYYYMMDDHHMMZ.
Implementors are warned that no DER is defined for GeneralizedTime,
thus transformation between local time representations not generate certificates with
private key usage period extensions.
4.2.1.5 Certificate Policies
The certificate policies extension contains a sequence of policy
information terms, each of which consists of an object identifier
(OID) and optional qualifiers. These policy information terms
indicate the DER
transfer syntax must be performed carefully when computing policy under which the hash
value for a certificate signature. For example, a GeneralizedTime
value which includes explict, zero values has been issued and
the purposes for seconds will not
produce which the same hash value as one certificate may be used. This profile
strongly recommends that a simple OID be present in this field.
Optional qualifiers which the seconds may be present are omitted.
GeneralizedTime expresses the using four digits. Remember that
UTCTime represents expected to provide
information about obtaining CA rules, not change the value of a year modulo 100, with no indication definition of century.
KeyAttributes ::= SEQUENCE {
keyIdentifier KeyIdentifier OPTIONAL,
intendedKeyUsage KeyUsage OPTIONAL,
privateKeyUsagePeriod PrivateKeyValidity OPTIONAL }
KeyIdentifier ::= OCTET STRING
PrivateKeyValidity ::= SEQUENCE {
notBefore [0] GeneralizedTime OPTIONAL,
notAfter [1] GeneralizedTime OPTIONAL }
KeyUsage ::= BIT STRING {
digitalSignature (0),
nonRepudiation (1),
keyEncipherment (2),
dataEncipherment (3),
keyAgreement (4),
keyCertSign (5),
offLineCRLSign (6) }
4.2.5 Key Usage Restriction
The keyUsageRestriction extension defines mandatory restrictions on
the use policy. Applications are expected to have a list of those
policies which they will accept and to compare the key contained policy OIDs in the
certificate based on policy
and/or usage (e.g., signature, encryption). to that list.
<< Do we want to say anything about criticality? >>
4.2.1.6 Policy Mappings
This field should extension may be
used whenever the use of the key supported by CAs and/or applications, and it is to be restricted based on either
usage or policy (see discussion in policies). The usage restriction
would be employed when a multipurpose key is to be restricted (e.g.,
when an RSA key should be used only for signing or only for key
always non-critical.
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encipherment).
4.2.1.7 Subject Alternative Name
The policy restriction in this field provides a mandate by subject alternative names extension allows additional identities
to be bound to the issuer
that subject of the certificate. Defined options
include an rfc822 name (electronic mail address), a certificate DNS name, an IP
address, and a URI. Other options exist, including completely local
definitions. Multiple instances of a name and multiple name forms
may be used only in selected environments (for
example, that included. Whenever such identities are to be bound into a certificate
certificate, the subject alternative name (or issuer alternative
name) extension shall be used only for used. (Note: a given type form of
financial transaction). In contrast, the policy such an identifier
may also be present in the
certificatePolicies subject distinguished name; however, the
alternative name extension is information which may be used at the
discretion of a relying party.
keyUsageRestriction ::= SEQUENCE {
certPolicySet SEQUENCE OF CertPolicyId OPTIONAL,
restrictedKeyUsage KeyUsage OPTIONAL }
4.2.6 Basic Constraints
The basicConstraints extension identifies whether preferred location for finding such
information.) Further, if the only subject of identity included in the
certificate is a CA or an end user. In addition, this field can
limit alternative name form (e.g., an electronic mail
address), then the authority of a subject CA in terms of distinguished name should be empty (an
empty sequence), the certificates it
can issue. Discussion of certification path restriction is covered
elsewhere in this draft. subjectAltName extension should be used, and the
subjectAltName extension must be marked critical.
<< In the previous version we said: The subject type field use of otherName should not
be present used in conjunction with this profile. Should we put this
restriction back? >>
Alternative names may be constrained in
all Internet certificates.
basicConstraints ::= SEQUENCE {
subjectType SubjectType,
pathLenConstraint INTEGER OPTIONAL,
permittedSubtrees [0] SEQUENCE OF GeneralName OPTIONAL,
excludedSubtrees [1] SEQUENCE OF GeneralName OPTIONAL }
SubjectType ::= BIT STRING {
cA (0),
endEntity (1) }
4.2.7 CRL Distribution Points
The cRLDistributionPoints extension identifies the CRL distribution
point or points to which a certificate user should refer to acertain
if the certificate has been revoked. This extenstion provides a
mechanism to divide the CRL inot manageable pieces if same manner as subject
distinguished names using the CA has a
large constituency. Further discussion of CRL management is
contained name constraints extension as described
in section 5.
4.2.8 Authority Key Identifier
The authority key identifier 4.2.1.11.
4.2.1.8 Issuer Alternative Name
As with 4.2.1.7, this extension provides a means of
identifying the particular public key is used to sign a certificate.
The identification can be based on either the key identifier (from associate Internet style
identities with the key Attributes extension) or on certificate issuer. If the only issuer name and serial
number. The key identifier method is recommended identity
included in this profile.
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This extension would be used where the certificate is an alternative name form (e.g., an
electronic mail address), then the issuer has multiple signing
keys (either due to multiple concurrent key pairs or due to
changeover). In general, this extension distinguished name should
be included in
certificates. If empty (an empty sequence), the issuer name/serial number approach is issuerAltName extension should be
used, both
the certIssuer and certSerialNumber fields the issuerAltName extension must be present.
authorityKeyId ::= SEQUENCE {
keyIdentifier [0] KeyIdentifier OPTIONAL,
certIssuer [1] Name OPTIONAL,
certSerialNumber [2] CertificateSerialNumber OPTIONAL }
4.2.9 marked critical.
4.2.1.9 Subject Directory Attributes
The DAM provides an extension for subject directory attributes. This
extension may hold any information about the subject where that
information has a defined X.500 Directory attribute. This attributes extension is not recommended as an
essential part of this profile profile, but it may be used in local
environments. This extension is always non-critical.
subjectDirectoryAttributes ::= SEQUENCE OF Attribute
4.2.10 Information Access
The informationAccess field
4.2.1.10 Basic Constraints
The basic constraints extension identifies whether the subject of the
certificate is proposed as a private extension to
tell CA and how information about deep a subject or CA (or ancillary CA services) certification path may be accessed. For example, this field might provide a pointer to
information about a user (e.g., a URL) or might tell how to access CA
information such as certificate status or on-line validation
services.
In many cases, exist
through that CA. This profile requires the accuracy use of this information is not certified by
the CA.
<< Can IssuerAltNames extension,
and SubjectAltNames be used instead of some of
this information? If not, then add a paragraph describing each of
the optional components? >>
informationAccess ::= SEQUENCE {
certRetrieval GeneralName OPTIONAL,
certValidation GeneralName OPTIONAL,
caInfo GeneralName OPTIONAL,
userInfo GeneralName OPTIONAL }
Url ::= IA5String it shall critical for all certificates issued to CAs.
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4.2.11 Other extensions
4.2.1.11 Name Constraints
The X.509 DAM defines additional extensions; however, this
specification does not include them name constraints extension provides permitted and excluded
subtrees that place restrictions on names that may be included within
a certificate issued by a given CA. Restrictions may apply to the
subject distringuished name or subject alternative names. Any name
matching a restriction in the profile.
<< policyMappings? We could say this optional. It excluded subtrees field is non-critical,
so not problematical. >>
<< nameConstraints. We should add a paragraph that strictly forbids
use invalid
regardless of this extensions. >>
<< policyConstraints? We should encourage support information appearing in the permitted subtrees.
Restrictions for the rfc822, dNSName, and uri name forms are all
expressed in terms of this extension.
Since it strings with wild card matching. An "*" is critical, we should include it the
wildcard character. The minimum and maximum fields in our profile so that all
implementations general
subtree are prepared to process it. It will be needed not used for
interoperability in these name forms. For uris and rfc822 names,
the future. >>
4.3 Examples
<< Certificate samples including descriptive text and ASN.1 encoded
blobs will be inserted. >>
5 CRL and CRL Extensions Profile
As described above, one goal of this X.509 v2 CRL profile is restriction applies to
foster the creation host part of an interoperable the name. Examples would
be foo.bar.com; www*.bar.com; *.xyz.com.
<< X.208 (1988) defines is IA5String as PrintableString plus
NumericString plus SPACE and reusable Internet PKI.
To achieve this goal, guidelines DELETE. Thus, it does not allow the for
the * character. What should we use of extensions are
specified, instead? >>
4.2.1.12 Policy Constraints
The policy constraints extension may be used by CAs.
4.2.1.13 CRL Distribution Points
The CRL distribution points extension identifies how CRL information
is obtained. The profile recommends support for this extension by
CAs and some assumptions are made about the nature applications. Further discussion of CRL management is
contained in section 5.
4.2.2 Private Internet Extensions
4.2.2.1 Subject Information Access
The name information included in the CRL.
CRLs certificate identifies the entity to
which the public key is bound. In some instances, it may also be used in a wide range
necessary to know where to find additional information about the
named entity. In the case of applications and environments
covering X.500 names, this relationship is
automatic. The subject information access extension provides a broad spectrum of interoperability goals and an even
broader spectrum means
of operational identifying where and assurance requirements. This
profile establishes a common baseline for generic applications
requiring broad interoperability. Emphasis is placed on support for
X.509 v2 CRLs. how to find information about the subject.
The profile defines extension specifies a baseline set method of obtaining information
that can be expected in every CRL. Also, the profile defines common
locations within the CRL for frequently used attributes, and common
representations for these attributes.
Environments with additional or special purpose requirements may
build on this profile or may replace it.
5.1 CRL Fields
The X.509 v2 CRL syntax is as follows. For signature calculation,
the data that is to be signed is ASN.1 DER encoded. ASN.1 DER
encoding is a tag, length, value encoding system for each element.
general name form indicating where. This extension should always be
non-critical.
subjectInfoAccess EXTENSION ::= {
SYNTAX SubjectInfoAccessSyntax
IDENTIFIED BY { TBD-OID-1 } }
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CertificateList
SubjectInfoAccessSyntax ::= SIGNED { SEQUENCE {
version Version OPTIONAL,
-- if present, must be v2
signature AlgorithmIdentifier,
issuer Name,
thisUpdate UTCTime,
nextUpdate UTCTime,
revokedCertificates SEQUENCE SIZE (1..MAX) OF SEQUENCE {
userCertificate CertificateSerialNumber,
revocationDate UTCTime,
crlEntryExtensions Extensions OPTIONAL } OPTIONAL,
crlExtensions [0] Extensions OPTIONAL } }
Version ::= INTEGER { v1(0), v2(1), v3(2) }
AlgorithmIdentifier AccessDescription
AccessDescription ::= SEQUENCE {
algorithm
accessMethod OBJECT IDENTIFIER,
parameters ANY DEFINED BY algorithm OPTIONAL
accessLocation GeneralName }
-- contains a value of the type
-- registered
<< What upper bound should be assigned for use with MAX? >>
<< Where is the
-- algorithm object identifier value
CertificateSerialNumber ::= INTEGER
Extensions ::= SEQUENCE OF Extension
Extension ::= SEQUENCE {
extnId OBJECT IDENTIFIER,
critical BOOLEAN DEFAULT FALSE,
extnValue OCTET STRING }
-- contains a DER encoding of a value
-- list of the type registered for use with
-- the extnId object identifier value access method OIDs going to be specified? >>
4.2.2.2 Authority Information Access
The following items describe authority information access extension indicates how to access CA
information and services for the proposed use issuer of the X.509 v2 CRL for certificate in Internet PKI.
5.1.1 Version
This field describes which
the version of extension appears. Information and services include certificate
status or on-line validation services, certificate retrieval, CA
policy data, and CA certificates (certificates certifying the encoded CRL. When extensions
are used, as expected in this profile, use version 2 (the integer
value is 1). If neither CRL extensions nor CRL entry extensions are
present, use version 1 (the integer value must be omitted).
5.1.2 Signature
This field contains the algorithm identifier for the algorithm used
to sign the CRL. Section 7.2 lists the signature algorithms used in
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the Internet PKI.
5.1.3 Issuer Name
The issuer name provides a globally unique identifier of the
certification authority signing the CRL. The syntax of the issuer
name is an X.500 distinguished name.
5.1.4 Last Update
This field indicates the issue date of this CRL.
The UTCTime (Coordinated Universal Time) value included in this field
shall be expressed in Greenwich Mean Time (Zulu) and include
granularity to the minute, even though finer granularity can be
expressed in the UTCTime format. That is, UTCTime should be
expressed as YYMMDDHHMMZ.
Implementors are warned that no DER is defined for UTCTime, thus
transformation between local time representations and the DER
transfer syntax must be performed carefully when computing the hash
value for a CRL signature. For example, a UTCTime value which
includes explict, zero values for seconds will not produce the same
hash value as one in which the seconds are omitted. UTCTime
expresses the value of a year modulo 100, with no indication of
century, hence comparisons involving dates in different centuries
must be performed with care.
5.1.5 Next Update
This field indicates the date by which the next CRL will be issued.
The next CRL could be issued before the indicated date, but it will
not be issued any later than the indicated date.
The same restrictions associated with UTCTime for Last Update apply
to Next Update.
5.1.6 Revoked Certificates
Revoked certificates are listed. The revoked certificates are named
by their serial numbers. Certificates are uniquely identified by the
combination of the issuer name and the user certificate serial
number. The date on which the revocation occured is specified. The
same restrictions associated with UTCTime for Last Update apply to
the revocation date. CRL entry extensions are discussed in section
5.3.
When a CA wishes to revoke a certificate that it issued to another
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CA, the revocation shall appear on the CRL. The revocation should
also appear on the ARL. The target
CA is revoking a certificate that it
issued.
5.2 CRL Extensions
The extensions already defined by ANSI X9 and ISO for X.509 v2 CRLs
provide methods for associating additional attributes with CRLs. The
X.509 v2 CRL format also allows communities to define private
extensions to carry information unique to those communities. Each
extension aid in a CRL may be designated as critical or non-critical. A
CRL validation must fail if it encounters an critical extension which
it does not know how to process. However, an unrecognized non-
critical certification path navigation). This extension may be ignored. The following presents those
extensions used within Internet CRLs. Communities
included in subject or CA certificates and may elect to use
additional extensions; however, caution should be exercised in
adopting any critical extensions in CRLs which might be used in a
general context. or non-
critical.
<< Need What does it mean to add table of OIDs for all extensions from X.509 and X9.55.
Say which are allowed in this profile, and which are prohibited in mark this profile. extension critical? >>
5.2.1 Authority Key Identifier
authorityInfoAccess EXTENSION ::= {
SYNTAX AuthorityInfoAccessSyntax
IDENTIFIED BY { TBD-OID-2 } }
AuthorityInfoAccessSyntax ::= SEQUENCE {
certStatus [0] SEQUENCE OF AccessDescription,
certRetrieval [1] SEQUENCE OF AccessDescription,
caPolicy [2] SEQUENCE OF AccessDescription,
caCerts [3] SEQUENCE OF AccessDescription }
4.2.2.3 CA Information Access
The authorityKeyIdentifier is a non-critical CRL CA information access extension that
identifies the CA's key used indicates how to sign access CA
information and services for the subject of the certificate in which
the CRL. This extension is
useful when a appears. Information and services include certificate
status or on-line validation services, certificate retrieval, CA uses more than one key; it allows distinct keys
differentiated (e.g., as key updating occurs). The key
policy data, and CA certificates (certificates certifying the target
CA to aid in cert path navigation). This extension may be
identified by included
only in CA certificates and may be critical or non-critical. CA
certificates may include both an explicit key identifier, by identification of authority and a
certificate caInfoAccess
extension to describe access methods for the key (giving certificate issuer and certificate
serial number), or both. If both are used then the CA issuer shall
ensure that all three fields are consistent.
AuthorityKeyId and its issuer.
caInfoAccess EXTENSION ::= SEQUENCE {
keyIdentifier [0] KeyIdentifier OPTIONAL,
certIssuer [1] Name OPTIONAL,
certSerialNumber [2] CertificateSerialNumber OPTIONAL
SYNTAX CAInfoAccessSyntax
IDENTIFIED BY { TBD-OID-2 } }
-- certIssuer and certSerialNumber constitute a logical pair,
-- and if either is present both must be present. Either this
-- pair or the keyIdentifier field or all shall be present
KeyIdentifier ::= OCTET STRING
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5.2.2 Issuer Alternative Name
The issuerAltName is a non-critical CRL extension that provides
additional CA names. Multiple instances may
CAInfoAccessSyntax ::= SEQUENCE {
certStatus [0] SEQUENCE OF AccessDescription,
certRetrieval [1] SEQUENCE OF AccessDescription,
caPolicy [2] SEQUENCE OF AccessDescription,
caCerts [3] SEQUENCE OF AccessDescription }
4.3 Examples
<< Certificate samples including descriptive text and ASN.1 encoded
blobs will be included. The syntax
for the issuerAltName is the same as inserted. >>
5 CRL and CRL Extensions Profile
As described in section 4.2.1.
Whenever such alternative names are included in a CRL, the issuer
alternative name field shall be used. Implementations which
recognize above, one goal of this extension are not required to be able X.509 v2 CRL profile is to process all
foster the alternative name formats. Unrecognized alternative name formats
may be ignored by an implementation.
The following definition is creation of an enhanced version interoperable and reusable Internet PKI.
To achieve this goal, guidelines for the use of extensions are
specified, and some assumptions are made about the X9.55
definition nature of GeneralName. This definition is anticipated to be used
information included in the X.509 Amendment.
rfc822Name, dNSName, url, and ipAddress are name forms expected to CRL.
CRLs may be used with this profile. Such names are subject to the basic
constraint extension for issuers which may restrict the names in a given
CA can certify (see section wide range of applications and environments
covering a broad spectrum of interoperability goals and an even
broader spectrum of operational and assurance requirements. This
profile establishes a common baseline for generic applications
requiring broad interoperability. Emphasis is placed on Basic Constraint extension). support for
X.509 v2 CRLs. The use profile defines a baseline set of otherName should not information
that can be used expected in conjunction with this
profile.
AltNames ::= SEQUENCE OF GeneralName
GeneralName ::= CHOICE {
otherName [0] INSTANCE OF OTHER-NAME,
rfc822Name [1] IA5String,
dNSName [2] IA5String,
x400Address [3] ORAddress,
directoryName [4] Name,
ediPartyName [5] IA5String,
url [6] IA5String,
ipAddress [7] OCTET STRING }
5.2.3 CRL Number
The cRLNumber is a non-critical every CRL. Also, the profile defines common
locations within the CRL extension which conveys a
monotonically increacing sequence number for each frequently used attributes, and common
representations for these attributes.
This profile does not define any private Internet CRL extensions or
CRL issued by a
given CA through a specific CA X.500 Directory entry extensions.
Environments with additional or special purpose requirements may
build on this profile or may replace it.
5.1 CRL
distribution point. This extension allows users to easily determine
when a particular Fields
The X.509 v2 CRL superceeds another CRL. CAs conforming syntax is as follows. For signature calculation,
the data that is to this
profile shall include this CRL.
CRLNumber be signed is ASN.1 DER encoded. ASN.1 DER
encoding is a tag, length, value encoding system for each element.
CertificateList ::= SEQUENCE {
tbsCertList TBSCertList,
signatureAlgorithm AlgorithmIdentifier,
signature BIT STRING }
TBSCertList ::= INTEGER SEQUENCE {
version Version OPTIONAL,
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5.2.4 Issuing Distribution Point
The issuingDistributionPoint is
-- if present, must be v2
signature AlgorithmIdentifier,
issuer Name,
thisUpdate UTCTime,
nextUpdate UTCTime,
revokedCertificates SEQUENCE OF SEQUENCE {
userCertificate CertificateSerialNumber,
revocationDate UTCTime,
crlEntryExtensions Extensions OPTIONAL } OPTIONAL,
crlExtensions [0] Extensions OPTIONAL }
Version ::= INTEGER { v1(0), v2(1), v3(2) }
AlgorithmIdentifier ::= SEQUENCE {
algorithm OBJECT IDENTIFIER,
parameters ANY DEFINED BY algorithm OPTIONAL }
-- contains a critical CRL extension that
identifiers value of the CRL distribution point type
-- registered for this particular CRL, and
it indicates whether use with the CRL covers revocation for end entity
certificates only, CA certificates only, or
-- algorithm object identifier value
CertificateSerialNumber ::= INTEGER
Extensions ::= SEQUENCE OF Extension
Extension ::= SEQUENCE {
extnId OBJECT IDENTIFIER,
critical BOOLEAN DEFAULT FALSE,
extnValue OCTET STRING }
-- contains a limitied set DER encoding of reason
codes. Support for CRL distribution points is strongly encouraged.
The use a value
-- of certificateHold is strictly prohibited in this profile.
Only the following reason codes may be used in conjunction with this
profile. The type registered for use of keyCompromise (1) shall be used to indicate
compromise or suspected compromise. with
-- the extnId object identifier value
The following items describe the proposed use of affiliationChanged
(3), superseded (4), or cessationOfOperation (5)shall be used to
indicate routine compromise.
<< Does anyone see a use for (2)? >>
The CRL is signed by the CA's key. CRL Distribution Points do not
have their own key pairs. If the CRL is stored in the X.500
Directory, it is stored entry corresponding to the CRL distribution
point, which may be different that X.509 v2 CRL for
in Internet PKI.
5.1.1 Version
This field describes the directory entry version of the CA.
CRL distribution points, if encoded CRL. When extensions
are used, should as expected in this profile, use version 2 (the integer
value is 1). If neither CRL extensions nor CRL entry extensions are
present, use version 1 (the integer value must be partitioned omitted).
5.1.2 Signature
This field contains the CRL on algorithm identifier for the basis of compromise and routine revocation. That is, algorithm used
to sign the
revocations with reason code (1) shall appear in one distribution
point, and CRL. Section 7.2 lists the revocations with reason codes (3), (4), and (5) shall
appear signature algorithms used in another distribution point.
DistributionPoint ::= SEQUENCE {
distributionPoint DistributionPointName,
reasons ReasonFlags OPTIONAL }
DistributionPointName ::= CHOICE {
fullName [0] Name,
nameRelativeToCA [1] RelativeDistinguishedName,
generalName [2] GeneralName }
GeneralName ::= CHOICE {
otherName [0] INSTANCE OF OTHER-NAME,
rfc822Name [1] IA5String,
dNSName [2] IA5String,
x400Address [3] ORAddress,
directoryName [4] Name,
ediPartyName [5] IA5String,
uniformResourceLocator [6] IA5String }
OTHER-NAME ::= TYPE-IDENTIFIER
the Internet PKI.
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ReasonFlags ::= BIT STRING {
unused (0),
keyCompromise (1),
caCompromise (2),
affiliationChanged (3),
superseded (4),
cessationOfOperation (5),
certificateHold (6) }
5.2.5 Delta CRL Indicator
5.1.3 Issuer Name
The deltaCRLIndicator is a critical CRL extension that issuer name identifies a
delta-CRL. the entity who has signed (and issued the
CRL). The use of delta-CRLs can significantly improve
processing time for applications which store revocation issuer identity may be carried in the issuer name field
and/or the issuerAltName extension. If identity information is
present only in a format other than the CRLstructure. issuerAltName extension, then the issuer name may
be an empty sequence and the issuerAltName extension must be
critical.
5.1.4 This allows changes to Update
This field indicates the issue date of this CRL.. It is strongly
recommended that UTCTime values be expressed Greenwich Mean Time
(Zulu) and not use seconds (i.e., times are YYMMDDHHMMZ). If seconds
are used, a value of 00 seconds should never be
added to encoded.
5.1.5 Next Update
This field indicates the local database while ignoring unchanged information that
is already in date by which the local databse.
CAs are shall always issue a complete next CRL when a delta-CRL is will be issued.
The value of BaseCRLNumber identifies the next CRL number of could be issued before the base CRL
that was used as indicated date, but it will
not be issued any later than the starting point indicated date.
As described in the generation of this delta-
CRL. The delta-CRL contains the changes between previous section, the base CRL UTCTime for Next Update
should be expressed Greenwich Mean Time (Zulu) and not use seconds.
5.1.6 Revoked Certificates
Revoked certificates are listed. The revoked certificates are named
by their serial numbers. Certificates are uniquely identified by the
current CRL issued
combination of the issuer name or issuer alternative name along with
the delta-CRL. It user certificate serial number. The date on which the revocation
occured is specified. As described in section 5.1.4, the decision of UTCTime for
revocationDate should be expressed Greenwich Mean Time (Zulu) and not
use seconds.. CRL entry extensions are discussed in section 5.3.
When a CA as to whether wishes to provide delta-CRLs. Again, revoke a delta-CRL shall not
be certificate that it issued without a corresponding CRL. The value of CRLNumber for
both the delta-CRL and to another
CA, the corresponding CRL shall be identical.
A CRL user constructing a locally held CRL from delta-CRLs revocation shall
consider the constructed CRL incomplete and unusable if the CRLNumber
of the received delta-CRL is more that one greater that appear on the CRLnumber
of CRL. The revocation should
also appear on the delta-CRL last processed.
5.3 authority revocation list (ARL). The CA is
revoking a certificate that it issued.
5.2 CRL Entry Extensions
The CRL entry extensions already defined by ANSI X9 and ISO for X.509 v2 CRLs [X.509-
AM] [X9.55] provide methods for associating additional attributes
with
CRL entries. CRLs. The X.509 v2 CRL format also allows communities to define
private CRL entry extensions to carry information unique to those communities.
Each extension in a CRL entry may be designated as critical or non-critical. non-
critical. A CRL validation must fail if it encounters an critical CRL entry
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extension which it does not know how to process. However, an
unrecognized non-critical CRL entry extension may be ignored. The following
presents recommended those extensions used within Internet CRL entries and standard locations
for information. CRLs. Communities may
elect to use additional CRL entry extensions; however, caution should be
exercised in adopting any critical extensions in CRL entries CRLs which might be
used in a general
Housley, Ford, & Solo [Page 25]
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<< Need to add table
5.2.1 Authority Key Identifier
The authority key identifier extension provides a means of OIDs for all extensions from X.509 and X9.55.
Say which are allowed
identifying the particular public key used to sign a CRL. The
identification can be based on either the key identifier (the subject
key identifier in this profile, the CRL signer's certificate) or on the issuer name
and which are prohibited serial number. The key identifier method is recommended in this
profile. >>
5.3.1 Reason Code
The reasonCode is a non-critical CRL entry This extension that identifies
the reason for the certificate revocation. CAs are strongly
encouraged would be used where an issuer has multiple
signing keys, either due to include reason codes multiple concurrent key pairs or due to
changeover. In general, this non-critical extension should be
included in CRL entries; however, some
reasonCode values are strictly prohibited. certificates.
5.2.2 Issuer Alternative Name
The reason code issuer alternative names extension
permits certificates allows additional identities
to placed on hold or suspended. The processing be associated with suspended certificates greatly complicates
certificate validation, therefore the use of reasonCode values
certificateHold (6), certHoldRelease (7), and removeFromCRL (8) issuer of the CRL. Defined options include
an rfc822 name (electronic mail address), a DNS name, an IP address,
and a URI. Multiple instances of a name and multiple name forms may
be included. Whenever such identities are used, the issuere
alternative name extension shall
not be used. Also, Further, if the only
issuer identity included in the reasonCode CRL entry is an alternative name form
(e.g., an electronic mail address), then the issuer distinguished
name should be empty (an empty sequence), the issuerAltName extension
should be
absent instead of using used, and the unspecified (0) reasonCode value.
<< Again, is there any reason to permit caCompromise (2)? >>
CRLReason ::= ENUMERATED {
unspecified (0),
keyCompromise (1),
caCompromise (2),
affiliationChanged (3),
superseded (4),
cessationOfOperation (5),
certificateHold (6),
certHoldRelease (7),
removeFromCRL (8) }
5.3.2 Expiration Date issuerAltName extension must be marked
critical.
5.2.3 CRL Number
The expirationDate CRL number is a non-critical CRL entry extension that
indicates the expiration of a hold entry in which conveys a CRL. The use of this
extension is strictly prohibited
monotonically increacing sequence number for each CRL issued by this profile.
5.3.3 Instruction Code
The instructionCode is a non-critical CRL
given CA through a specific CA X.500 Directory entry or CRL
distribution point. This extension that
provides a registered instruction identifier which indicates the
action allows users to be taken after encountering easily determine
when a certificate that has been
placed on hold. The use of particular CRL superceeds another CRL. CAs conforming to this extension is strictly prohibited by
profile shall include this profile.
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5.3.4 Invalidity Date CRL.
5.2.4 Issuing Distribution Point
The invalidityDate issuing distribution point is a non-critical critical CRL entry extension that
provides the date on which it is known or suspected that the private
key was compromised or that the certificate otherwise became invalid.
This date may be earlier than the revocation date in
identifies the CRL entry,
but distribution point for a particular CRL, and it must be later than the issue date of the previously issued
CRL. Remember that the revocation date in
indicates whether the CRL entry specifies
the date that the covers revocation for end entity
certificates only, CA revoked the certificate. Whenever certificates only, or a limitied set of reason
codes. Since this
information extension is available, CAs are strongly encouraged critical, all certificate users must
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be prepared to share it receive CRLs with CRL users.
The GeneralizedTime values included in this field shall be expressed
in Greenwich Mean Time (Zulu) and include granularity to the minute,
even though finer granularity can be expressed in the GeneralizedTime
format. That is, GeneralizedTime should be expressed as
YYYYMMDDHHMMZ.
Implementors are warned that no DER extension.
The CRL is defined for GeneralizedTime,
thus transformation between local time representations and the DER
transfer syntax must be performed carefully when computing signed using the hash
value for a certificate signature. For example, a GeneralizedTime
value which includes explict, zero values for seconds will CA's private key. CRL Distribution
Points do not
produce have their own key pairs. If the same hash value as one CRL is stored in which the seconds are omitted.
GeneralizedTime expresses
X.500 Directory, it is stored in the using four digits. Remember that
UTCTime represents Directory entry corresponding to
the value of a year modulo 100, with no indication
of century.
InvalidityDate ::= GeneralizedTime
5.4 Examples
<< CRL samples including descriptive text and ASN.1 encoded blobs
will distribution point, which may be inserted. >>
6 Certificate Path Validation
Certification path processing verifies the binding between different that the
subject distinguished name and subject public key. The basic
constraints and policy constraints extensions facilitate automated,
self-contained implementation of certification path processing logic.
The following is an outline Directory
entry of a procedure for validating
certification paths. An implementation shall be functionally
equivalent to the external behaviour resulting from this procedure.
Any algorithm may be CA.
CRL distribution points, if used by a particular implementation so long as
it derives CA, should be partition the correct result.
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The inputs to CRL
on the certification path processing procedure are:
(a) a set basis of certificates comprising a certification path;
(b) a CA name compromise and trusted public key value (or an identifier of
such a key if the key is stored internally to routine revocation. That is, the certification
path processing module) for use
revocations with reason code keyCompromise (1) shall appear in verifying one
distribution point, and the first certificate revocations with other reason codes shall
appear in the certification path;
(c) a set of initial-policy identifiers (each comprising another distribution point.
5.2.5 Delta CRL Indicator
The delta CRL indicator is a
sequence of policy element identifiers), which critical CRL extension that identifies one or
more certificate policies, any one a
delta-CRL. The use of delta-CRLs can significantly improve
processing time for applications which would store revocation information
in a format other than the CRL structure. This allows changes to be acceptable
for
added to the purposes of certification path processing; and
(d) local database while ignoring unchanged information that
is already in the current date/time (if not available internally to local databse.
When a delta-CRL is issued, the
certification path processing module). CAs shall also issue a complete CRL.
The outputs value of BaseCRLNumber identifies the procedure are:
(a) an indication of success or failure CRL number of certification path
validation;
(b) if validation failed, a reason for failure; and
(c) if validation the base CRL
that was successful, a (possibly empty) set of
policy qualifiers obtained from CAs on used as the path.
The procedure makes use of starting point in the following set of state variables:
(a) acceptable policy set: A set generation of certificate policy identifiers
comprising this delta-
CRL. The delta-CRL contains the changes between the policy or policies recognized by base CRL and the public key user
together
current CRL issued along with policies deemed equivalent through policy mapping;
(b) constrained subtrees: A set of root names defining a set of
subtrees within which all subject names in subsequent certificates in the certification path shall fall; if no restriction delta-CRL. It is in force this
state variable takes the special decision of a
CA as to whether to provide delta-CRLs. Again, a delta-CRL shall not
be issued without a corresponding CRL. The value unbounded; of CRLNumber for
both the delta-CRL and
(c) excluded subtrees: the corresponding CRL shall be identical.
A set of root names defining CRL user constructing a set of
subtrees within which no subject name in subsequent certificates in locally held CRL from delta-CRLs shall
consider the certification path may fall; constructed CRL incomplete and unusable if no restriction the CRLNumber
of the received delta-CRL is in force this
state variable takes more that one greater that the special value empty. CRLnumber
of the delta-CRL last processed.
5.3 CRL Entry Extensions
The procedure involves an initialization step, followed CRL entry extensions already defined by a series
of certificate-processing steps. ANSI X9 and ISO for X.509
v2 CRLs [X.509-AM] [X9.55] provide methods for associating additional
attributes with CRL entries. The initialization step comprises:
(a) Initialize the constrained subtress X.509 v2 CRL format also allows
communities to unbounded;
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(b) Initialize the excluded subtrees indicator define private CRL entry extensions to empty; and
(c) Initialize the acceptable policy set carry
information unique to the set of initial-
policy identifiers. those communities. Each certificate is then processed extension in turn, starting with the
certificate signed using the trusted CA public key a CRL
entry may be designated as critical or non-critical. A CRL
validation must fail if it encounters an critical CRL entry extension
which was input it does not know how to
this procedure. The last certificate is processed as process. However, an end-entity
certificate; all other certificates (if any) are processed as CA-
certificates. unrecognized
non-critical CRL entry extension may be ignored. The following checks are applied to all certificates:
(a) Check that the signature verifies, that dates are valid, that
the subject and issuer names chain correctly,
Housley, Ford, & Solo [Page 23]
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presents recommended extensions used within Internet CRL entries and that the
certificate has not been revoked;
(b) If
standard locations for information. Communities may elect to use
additional CRL entry extensions; however, caution should be exercised
in adopting any critical extensions in CRL entries which might be
used in a key usage restriction extension general context.
5.3.1 Reason Code
The reasonCode is present in the
certificate and contains a certPolicySet component, check non-critical CRL entry extension that at
least one member of identifies
the acceptable policy set appears reason for the certificate revocation. As are strongly encouraged
to include reason codes in CRL entries; however, the
field;
(c) Check that reason code CRL
entry extension should be absent instead of using the subject name unspecified (0)
reasonCode value.
5.3.2 Hold Instruction Code
The hold instruction code is consistent with the
constrained subtrees state variables; and
(d) Check a non-critical CRL entry extension that the subject name is consistent with the excluded
subtrees state variables.
If any one of the above checks fails, the procedure terminates,
returning
provides a failure indication and an appropriate reason. If none of
the above checks fail on the end-entity certificate, registered instruction identifier which indicates the procedure
terminates, returning
action to be taken after encountering a success indication together with the set of
all policy qualifier values encountered in certificate that has been
placed on hold.
<< The Directory Specification does not define any standard hold
instruction codes. Where will they be defined? Are any specific to
the set of certificates.
For Internet environment? >>
5.3.3 Invalidity Date
The invalidity date is a CA-certificate, non-critical CRL entry extension that
provides the following constraint recording actions are
then performed, in order to correctly set up date on which it is known or suspected that the state variables for private
key was compromised or that the processing of certificate otherwise became invalid.
This date may be earlier than the next certificate:
(a) If permittedSubtrees is present revocation date in the certificate, set the
constrained subtrees state variable to CRL entry,
but it must be later than the intersection issue date of its
previous value and the value indicated in previously issued
CRL. Remember that the extension field.
(b) If excludedSubtrees is present revocation date in the certificate, set the
excluded subtrees state variable to CRL entry specifies
the union of its previous
value and date that the value indicated in CA revoked the extension field.
Note: It certificate. Whenever this
information is possible available, CAs are strongly encouraged to specify an extended version of the above
certification path processing procedure which results share it
with CRL users.
The GeneralizedTime values included in default
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behaviour identical to the rules of Privacy Enhanced Mail [RFC 1422].
In this extended version, additional inputs to the procedure are a
list of one or more Policy Certification Authority (PCA) names and an
indicator of the position field shall be expressed
in Greenwich Mean Time (Zulu) and omit trailing zeros in fractional
seconds. Normally, GeneralizedTime will be expressed as
YYYYMMDDHHMMSSZ.
5.4 Examples
<< CRL samples including descriptive text and ASN.1 encoded blobs
will be inserted. >>
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6 Certificate Path Validation
<< There used to be long section here that contained the
certification path where the PCA is
expected. At the nominated PCA position, the CA name is compared
against this list. If a recognized PCA name is found, then a
constraint of SubordinateToCA is implicitly assumed for the remainder
of the certification path and processing continues. If validation procedures. The major deviations from
the procedures outlined in [X.509-AM] were due to certificate hold
processing. These procedures are no valid PCA
name longer onerous, so there is found, and if the certification path cannot be validated on no
reason to prohibit the basis use of identified policies, then the certification path is
considered invalid. hold facility. Does anyone see a
reason to reatin this section? >>
7 Algorithm Support
7.1 One-way Hash Functions
One-way hash functions are also called message digest algorithms.
SHA-1 is be the most popular one-way hash function used in the
Internet PKI. However, PEM uses MD2 for certificates [RFC1422,
RFC1423]. [RFC 1422] [RFC
1423]. For this reason, MD2 may continue to be used is included in
certificates for many years. this profile.
7.1.1 MD2 One-way Hash Function
MD2 was also developed by Ron Rivest, but RSA Data Security has not
placed the MD2 algorithm in the public domain. Rather, RSA Data
Security has granted license to use MD2 for non-commerical Internet
Privacy-Enhanced Mail. For this reason, MD2 may continue to be used
with PEM certificates, but MD5 SHA-1 is preferred. MD2 is fully
described in RFC 1319.
<< Add a paragraph about 1319 [RFC 1319].
At the Selected Areas in Cryptography '95 conference in May 1995,
Rogier and Chauvaud presented an attack on MD2 flaw that was recently discovered.
Urge can nearly find
collisions [RC95]. Collisions occur when two different messages
generate the same message digest. A checksum operation in MD2 replacement with SHA-1. is the
only remaining obstacle to the success of the attack. For this
reason, the use of MD2 for new applications is discouraged. It is
still reasonable to use MD2 to verify existing signatures, as the
ability to find collisions in MD2 does not enable an attacker to find
new messages having a previously computed hash value.
<< More information on the attack and its implications can be
obtained from a RSA Laboratories security bulletin. These bulletins
are available from <http://www.rsa.com/>. >>
7.1.2 SHA-1 One-way Hash Function
SHA-1 was developed by the U.S. Government. SHA-1 is fully described
in FIPS 180-1. 180-1 [FIPS 180-1].
SHA-1 is the one-way hash function of choice for use with both RSA
the DSA signature algorithms.
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7.2 Signature Algorithms
RSA and DSA are the most popular signature algorithms used in the
Internet.
There is some ambiguity in 1988 X.509 document regarding with respect to the
Housley, Ford, & Solo [Page 30]
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definition of the SIGNED macro regarding, and the representation of a signature
in a certificate or a CRL. The interpretation selected for the
Internet requires that the data to be signed (e.g., the one-way hash
function output value) is first ASN.1 encoded as an OCTET STRING and
the result is encrypted (e.g., using RSA Encryption) to form the
signed quantity, which quantity. Asd part of the SIGNED macro, this signature value
is then ASN.1 encoded as a BIT STRING.
7.2.1 RSA Signature Algorithm
A patent statement regarding the RSA algorithm can be found at the
end of this profile.
The RSA algorithm is named for it's inventors: Rivest, Shamir, and
Adleman. The RSA signature algorithm is defined in PKCS #1. #1 [PKCS#1].
It combines the either the MD2 or the SHA-1 one-way hash function with
the RSA asymmetric encryption algorithm. As defined in PKCS #1, the
ASN.1 object identifiers used to identify these signature algorithms
are:
md2WithRSAEncryption OBJECT IDENTIFIER ::= {
iso(1) member-body(2) US(840) rsadsi(113549) pkcs(1)
pkcs-1(1) 2 }
sha-1WithRSAEncryption OBJECT IDENTIFIER ::= {
iso(1) identified-organization(3) oiw(14) secsig(3)
algorithm(2) 29 }
When either of these object identifiers is used within the ASN.1 type
AlgorithmIdentifier, the parameters component of that type shall be
absent or the
ASN.1 type NULL.
7.2.2 DSA Signature Algorithm
A patent statement regarding the DSA can be found at the end of this
profile.
The Digital Signature Algorithm (DSA) is also called the Digital
Signature Standard (DSS). DSA was developed by the U.S. Government,
and DSA is used in conjunction with the the SHA-1 one-way hash
function. DSA is fully described in FIPS 186. 186 [FIPS 186]. The ASN.1
object identifiers used to identify this signature algorithm is:
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dsaWithSHA-1 OBJECT IDENTIFIER ::= {
joint-iso-ccitt(2) country(16) US(840) organization(1)
us-government(101) dod(2) infosec(1) algorithms(1) 2
iso(1) identified-organization(3) oiw(14) secsig(3)
algorithm(2) 27 }
When this object identifier
The DSA algorithm syntax includes optional parameters. These
parameters are commonly referred to as p, q, and g. The
AlgorithmIdentifier within subjectPublicKeyInfo is used with the ASN.1 type
AlgorithmIdentifier, the only place
within a certificate where these parameters component of that type is
Housley, Ford, & Solo [Page 31]
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optional. shall be present. If it is absent, the
DSA algorithm parameters p, q, and g are
assumed absent from the subjectPublicKeyInfo
AlgorithmIdentifier and the CA signed the subject certificate using
DSA, then the certificate issuer's DSA parameters apply to be known, otherwise the
subject's DSA key. If the DSA algorithm parameters are absent from
the subjectPublicKeyInfo AlgorithmIdentifier and the CA signed the
subject certificate using a signature algorithm other than DSA, then
the subject's DSA parameters are distributed by other means. The
parameters are included using the following ASN.1 structure:
Dss-Parms ::= SEQUENCE {
p OCTET STRING, INTEGER,
q OCTET STRING, INTEGER,
g OCTET STRING INTEGER }
When signing, DSA algorithm generates two values. These values are
commonly referred to as r and s. To easily transfer these two values
as one siganture, they are ASN.1 encoded using the following ASN.1
structure:
Dss-Sig-Value ::= SEQUENCE {
r INTEGER,
s INTEGER }
7.3 Subject Public Key Algorithms
<< Add a section that lists the public key algorithms that are
supported by this profile. Obviously, RSA, DSA, Diffie-Hellman, and
KEA will be included. Are there others? >>
<< Should a different algorithm identifier be assigned to RSA
signature keys and RSA key management keys? If so, there will be one
subsection for each within this section.>>
References
[FIPS 180-1] Federal Information Processing Standards Publication
(FIPS PUB) 180-1, Secure Hash Standard, 17 April 1995.
[Supersedes FIPS PUB 180 dated 11 May 1993.]
[FIPS 186] Federal Information Processing Standards Publication
(FIPS PUB) 186, Digital Signature Standard, 18 May 1994.
Housley, Ford, & Solo [Page 27]
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[PKCS#1] PKCS #1: RSA Encryption Standard, Version 1.4, RSA Data
Security, Inc., 3 June 1991.
[RC95] Rogier, N. and Chauvaud, P., "The compression function of
MD2 is not collision free," Presented at Selected Areas in
Cryptography '95, Carleton University, Ottawa, Canada,
18-19 May 1995.
[RFC 1319] Kaliski, B., "The MD2 Message-Digest Algorithm," RFC 1319,
RSA Laboratories, April 1992.
[RFC 1422] Kent, S., "Privacy Enhancement for Internet Electronic
Mail: Part II: Certificate-Based Key Management," RFC
1422,
BBN Communications, February 1993.
[RFC 1423] Balenson, D., "Privacy Enhancement for Internet Electronic
Mail: Part III: Algorithms, Modes, and Identifiers,"
RFC 1423, Trusted Information Systems, February 1993.
[X.208] << Do we want to reference the 1988 or 1993 version? >>
[X.509-AM] << Need final reference >>
[X9.55] << Need final reference >>
Patent Statements
The Internet PKI relies on the use of patented public key technology.
The Internet Standards Process as defined in RFC 1310 requires a
written statement from the Patent holder that a license will be made
available to applicants under reasonable terms and conditions prior
to approving a specification as a Proposed, Draft or Internet
Standard.
Patent statements for DSA, RSA, and Diffie-Hellman follow. These
statements have been supplied by the patent holders, not the authors
of this profile.
Digital Signature Algorithm (DSA)
The U.S. Government holds patent 5,231,668 on the Digital
Signature Algorithm (DSA), which has been incorporated into
Federal Information Processing Standard (FIPS) 186. The patent
was issued on July 27, 1993.
The National Institute of Standards and Technology (NIST) has a
long tradition of supplying U.S. Government-developed techniques
Housley, Ford, & Solo [Page 28]
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to committees and working groups for inclusion into standards on a
royalty-free basis. NIST has made the DSA patent available
royalty-free to users worldwide.
Regarding patent infringement, FIPS 186 summarizes our position;
the Department of Commerce is not aware of any patents that would
be infringed by the DSA. Questions regarding this matter may be
Housley, Ford, & Solo [Page 32]
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directed to the Deputy Chief Counsel for NIST.
RSA Signature and Encryption
<< Now that PKP has dissolved, a revised patent statement for RSA
from RSADSI is needed. >>
Diffie-Hellman Key Agreement
<< Now that PKP has dissolved, a revised patent statement for
Diffie-Hellman from Cylink is needed. >>
Obsolete PKP Patent Statement
<< This statement is included here until a replacement from RSADSI
and Cylink can be obtained. >>
The Massachusetts Institute of Technology and the Board of
Trustees of the Leland Stanford Junior University have granted
Public Key Partners (PKP) exclusive sub-licensing rights to the
following patents issued in the United States, and all of their
corresponding foreign patents:
Cryptographic Apparatus and Method
("Diffie-Hellman")......................... No. 4,200,770
Public Key Cryptographic Apparatus
and Method ("Hellman-Merkle").............. No. 4,218,582
Cryptographic Communications System and
Method ("RSA")............................. No. 4,405,829
Exponential Cryptographic Apparatus
and Method ("Hellman-Pohlig").............. No. 4,424,414
These patents are stated by PKP to cover all known methods of
practicing the art of Public Key encryption, including the
variations collectively known as El Gamal.
Public Key Partners has provided written assurance to the Internet
Society that parties will be able to obtain, under reasonable,
Housley, Ford, & Solo [Page 29]
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nondiscriminatory terms, the right to use the technology covered
by these patents. This assurance is documented in RFC 1170 titled
"Public Key Standards and Licenses". A copy of the written
assurance dated April 20, 1990, may be obtained from the Internet
Assigned Number Authority (IANA).
The Internet Society, Internet Architecture Board, Internet
Housley, Ford, & Solo [Page 33]
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Engineering Steering Group and the Corporation for National
Research Initiatives take no position on the validity or scope of
the patents and patent applications, nor on the appropriateness of
the terms of the assurance. The Internet Society and other groups
mentioned above have not made any determination as to any other
intellectual property rights which may apply to the practice of
this standard. Any further consideration of these matters is the
user's own responsibility.
Security Considerations
This entire memo is about security mechanisms.
Author Addresses:
Russell Housley
SPYRUS
PO Box 1198
Herndon, VA 22070
USA
housley@spyrus.com
Warwick Ford
Nortel Secure Networks
PO Box 3511, Station C
Ottawa, Ontario
Canada KY 4H7
wford@bnr.ca
David Solo
BBN
150 CambridgePark Drive
Cambridge, MA 02140
USA
solo@bbn.com
Housley, Ford, & Solo [Page 34] 30]
----