PKIX Working Group                         R. Housley (RSA Laboratories)
Internet Draft                                        W. Ford (VeriSign)
                                                          W. Polk (NIST)
                                                     D. Solo (Citigroup)
expires in six months                                         April 2001


                Internet X.509 Public Key Infrastructure

                      Certificate and CRL Profile

                   <draft-ietf-pkix-new-part1-06.txt>


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.  Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
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   working documents as Internet-Drafts.

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   Copyright (C) The Internet Society (2001).  All Rights Reserved.


Abstract

   This is the sixth draft of a specification based upon RFC 2459.  When
   complete, this specification will obsolete RFC 2459.  This
   specification includes minor edits and clarifications.  The most
   notable departures from RFC 2459 are found in Section 6, Path
   Validation.  In RFC 2459, the reader was expected to augment the path
   validation algorithm, which concentrated upon policy processing, with
   information embedded in earlier sections.  For example, parameter
   inheritance is discussed in Section 7, Algorithm Support, and can
   certainly affect the validity of a certification path.  However,
   parameter inheritance was omitted from the path validation algorithm



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   in RFC 2459.  In this draft, the path validation algorithm has a
   comprehensive and extremely detailed description.  Details such as
   parameter inheritance are covered thoroughly.  In addition, this
   draft anticipates certain corrections proposed in the X.509 standard
   for the policy processing aspects of path validation.

   A new section 6.3, CRL validation, has been added as well.  This
   section provides a supplement to the path validation algorithm that
   determines if a particular CRL may be used to verify the status of a
   particular certificate.  (The basic path validation algorithm is, by
   design, independent of the type and format of status information.)

   The most significant enhancement in draft five is a refinement of the
   processing rules for path length constraints when applied to CA
   certificates.  This draft also completes the removal of processing
   rules for unique identifiers.  This was generally performed in the
   fourth draft, but some details were overlooked.  This draft also
   incorporates significant corrections to the ASN.1 modules in the
   appendices.

   This memo profiles the X.509 v3 certificate and X.509 v2 CRL for use
   in the Internet.  An overview of the approach and model are provided
   as an introduction.  The X.509 v3 certificate format is described in
   detail, with additional information regarding the format and
   semantics of Internet name forms (e.g., IP addresses).  Standard
   certificate extensions are described and one new Internet-specific
   extension is defined.  A required set of certificate extensions is
   specified.  The X.509 v2 CRL format is described and a required
   extension set is defined as well.  An algorithm for X.509 certificate
   path validation is described. Supplemental information is provided
   describing the format of public keys and digital signatures in X.509
   certificates for common Internet public key encryption algorithms
   (i.e., RSA, DSA, and Diffie-Hellman).  ASN.1 modules and examples are
   provided in the appendices.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119.

   Please send comments on this document to the ietf-pkix@imc.org mail
   list.










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                             Table of Contents

1  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
2  Requirements and Assumptions  . . . . . . . . . . . . . . . . . .   7
2.1  Communication and Topology  . . . . . . . . . . . . . . . . . .   7
2.2  Acceptability Criteria  . . . . . . . . . . . . . . . . . . . .   8
2.3  User Expectations . . . . . . . . . . . . . . . . . . . . . . .   8
2.4  Administrator Expectations  . . . . . . . . . . . . . . . . . .   8
3  Overview of Approach  . . . . . . . . . . . . . . . . . . . . . .   8
3.1  X.509 Version 3 Certificate . . . . . . . . . . . . . . . . . .  10
3.2  Certification Paths and Trust . . . . . . . . . . . . . . . . .  11
3.3  Revocation  . . . . . . . . . . . . . . . . . . . . . . . . . .  13
3.4  Operational Protocols . . . . . . . . . . . . . . . . . . . . .  14
3.5  Management Protocols  . . . . . . . . . . . . . . . . . . . . .  14
4  Certificate and Certificate Extensions Profile  . . . . . . . . .  15
4.1  Basic Certificate Fields  . . . . . . . . . . . . . . . . . . .  16
4.1.1  Certificate Fields  . . . . . . . . . . . . . . . . . . . . .  17
4.1.1.1  tbsCertificate  . . . . . . . . . . . . . . . . . . . . . .  17
4.1.1.2  signatureAlgorithm  . . . . . . . . . . . . . . . . . . . .  17
4.1.1.3  signatureValue  . . . . . . . . . . . . . . . . . . . . . .  18
4.1.2  TBSCertificate  . . . . . . . . . . . . . . . . . . . . . . .  18
4.1.2.1  Version . . . . . . . . . . . . . . . . . . . . . . . . . .  18
4.1.2.2  Serial number . . . . . . . . . . . . . . . . . . . . . . .  19
4.1.2.3  Signature . . . . . . . . . . . . . . . . . . . . . . . . .  19
4.1.2.4  Issuer  . . . . . . . . . . . . . . . . . . . . . . . . . .  19
4.1.2.5  Validity  . . . . . . . . . . . . . . . . . . . . . . . . .  23
4.1.2.5.1  UTCTime . . . . . . . . . . . . . . . . . . . . . . . . .  23
4.1.2.5.2  GeneralizedTime . . . . . . . . . . . . . . . . . . . . .  23
4.1.2.6  Subject . . . . . . . . . . . . . . . . . . . . . . . . . .  24
4.1.2.7  Subject Public Key Info . . . . . . . . . . . . . . . . . .  25
4.1.2.8  Unique Identifiers  . . . . . . . . . . . . . . . . . . . .  25
4.1.2.9 Extensions . . . . . . . . . . . . . . . . . . . . . . . . .  25
4.2  Certificate Extensions  . . . . . . . . . . . . . . . . . . . .  25
4.2.1  Standard Extensions . . . . . . . . . . . . . . . . . . . . .  26
4.2.1.1  Authority Key Identifier  . . . . . . . . . . . . . . . . .  27
4.2.1.2  Subject Key Identifier  . . . . . . . . . . . . . . . . . .  27
4.2.1.3  Key Usage . . . . . . . . . . . . . . . . . . . . . . . . .  29
4.2.1.4  Private Key Usage Period  . . . . . . . . . . . . . . . . .  30
4.2.1.5  Certificate Policies  . . . . . . . . . . . . . . . . . . .  31
4.2.1.6  Policy Mappings . . . . . . . . . . . . . . . . . . . . . .  33
4.2.1.7  Subject Alternative Name  . . . . . . . . . . . . . . . . .  34
4.2.1.8  Issuer Alternative Name . . . . . . . . . . . . . . . . . .  36
4.2.1.9  Subject Directory Attributes  . . . . . . . . . . . . . . .  37
4.2.1.10  Basic Constraints  . . . . . . . . . . . . . . . . . . . .  37
4.2.1.11  Name Constraints . . . . . . . . . . . . . . . . . . . . .  38
4.2.1.12  Policy Constraints . . . . . . . . . . . . . . . . . . . .  40
4.2.1.13  Extended key usage field . . . . . . . . . . . . . . . . .  41
4.2.1.14  CRL Distribution Points  . . . . . . . . . . . . . . . . .  42



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4.2.1.15  Inhibit Any-Policy . . . . . . . . . . . . . . . . . . . .  43
4.2.1.16  Freshest CRL . . . . . . . . . . . . . . . . . . . . . . .  43
4.2.2  Internet Certificate Extensions . . . . . . . . . . . . . . .  44
4.2.2.1  Authority Information Access  . . . . . . . . . . . . . . .  44
4.2.2.2  Subject Information Access  . . . . . . . . . . . . . . . .  45
5  CRL and CRL Extensions Profile  . . . . . . . . . . . . . . . . .  47
5.1  CRL Fields  . . . . . . . . . . . . . . . . . . . . . . . . . .  47
5.1.1  CertificateList Fields  . . . . . . . . . . . . . . . . . . .  48
5.1.1.1  tbsCertList . . . . . . . . . . . . . . . . . . . . . . . .  48
5.1.1.2  signatureAlgorithm  . . . . . . . . . . . . . . . . . . . .  49
5.1.1.3  signatureValue  . . . . . . . . . . . . . . . . . . . . . .  49
5.1.2  Certificate List "To Be Signed" . . . . . . . . . . . . . . .  49
5.1.2.1  Version . . . . . . . . . . . . . . . . . . . . . . . . . .  49
5.1.2.2  Signature . . . . . . . . . . . . . . . . . . . . . . . . .  49
5.1.2.3  Issuer Name . . . . . . . . . . . . . . . . . . . . . . . .  50
5.1.2.4  This Update . . . . . . . . . . . . . . . . . . . . . . . .  50
5.1.2.5  Next Update . . . . . . . . . . . . . . . . . . . . . . . .  50
5.1.2.6  Revoked Certificates  . . . . . . . . . . . . . . . . . . .  51
5.1.2.7  Extensions  . . . . . . . . . . . . . . . . . . . . . . . .  51
5.2  CRL Extensions  . . . . . . . . . . . . . . . . . . . . . . . .  51
5.2.1  Authority Key Identifier  . . . . . . . . . . . . . . . . . .  51
5.2.2  Issuer Alternative Name . . . . . . . . . . . . . . . . . . .  52
5.2.3  CRL Number  . . . . . . . . . . . . . . . . . . . . . . . . .  52
5.2.4  Delta CRL Indicator . . . . . . . . . . . . . . . . . . . . .  52
5.2.5  Issuing Distribution Point  . . . . . . . . . . . . . . . . .  54
5.2.6  Freshest CRL  . . . . . . . . . . . . . . . . . . . . . . . .  55
5.3  CRL Entry Extensions  . . . . . . . . . . . . . . . . . . . . .  55
5.3.1  Reason Code . . . . . . . . . . . . . . . . . . . . . . . . .  56
5.3.2  Hold Instruction Code . . . . . . . . . . . . . . . . . . . .  56
5.3.3  Invalidity Date . . . . . . . . . . . . . . . . . . . . . . .  57
5.3.4  Certificate Issuer  . . . . . . . . . . . . . . . . . . . . .  57
6  Certificate Path Validation . . . . . . . . . . . . . . . . . . .  58
6.1  Basic Path Validation . . . . . . . . . . . . . . . . . . . . .  58
6.1.1 Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . .  61
6.1.2 Initialization . . . . . . . . . . . . . . . . . . . . . . . .  62
6.1.3 Basic Certificate Processing . . . . . . . . . . . . . . . . .  65
6.1.4 Preparation for Certificate i+1  . . . . . . . . . . . . . . .  70
6.1.5 Wrap-up procedure  . . . . . . . . . . . . . . . . . . . . . .  73
6.1.6 Outputs  . . . . . . . . . . . . . . . . . . . . . . . . . . .  74
6.2  Extending Path Validation . . . . . . . . . . . . . . . . . . .  75
6.3  CRL Validation  . . . . . . . . . . . . . . . . . . . . . . . .  75
6.3.1  Revocation Inputs . . . . . . . . . . . . . . . . . . . . . .  76
6.3.2  Initialization and Revocation State Variables . . . . . . . .  76
6.3.3  CRL Processing  . . . . . . . . . . . . . . . . . . . . . . .  77
7  References  . . . . . . . . . . . . . . . . . . . . . . . . . . .  79
8  Intellectual Property Rights  . . . . . . . . . . . . . . . . . .  81
9  Security Considerations . . . . . . . . . . . . . . . . . . . . .  81
Appendix A.  ASN.1 Structures and OIDs . . . . . . . . . . . . . . .  85



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A.1 Explicitly Tagged Module, 1988 Syntax  . . . . . . . . . . . . .  85
A.2 Implicitly Tagged Module, 1988 Syntax  . . . . . . . . . . . . .  98
Appendix B.  ASN.1 Notes . . . . . . . . . . . . . . . . . . . . . . 105
Appendix C.  Examples  . . . . . . . . . . . . . . . . . . . . . . . 106
C.1  Certificate . . . . . . . . . . . . . . . . . . . . . . . . . . 107
C.2  Certificate . . . . . . . . . . . . . . . . . . . . . . . . . . 110
C.3  End-Entity Certificate Using RSA  . . . . . . . . . . . . . . . 113
C.4  Certificate Revocation List . . . . . . . . . . . . . . . . . . 116
Appendix D.  Author Addresses  . . . . . . . . . . . . . . . . . . . 118
Appendix E.  Full Copyright Statement  . . . . . . . . . . . . . . . 118









































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1  Introduction

   This specification is one part of a family of standards for the X.509
   Public Key Infrastructure (PKI) for the Internet.  This specification
   is a standalone document; implementations of this standard may
   proceed independent from the other parts.

   This specification profiles the format and semantics of certificates
   and certificate revocation lists for the Internet PKI.  Procedures
   are described for processing of certification paths in the Internet
   environment.  Encoding rules are provided for popular cryptographic
   algorithms.  Finally, ASN.1 modules are provided in the appendices
   for all data structures defined or referenced.

   The specification describes the requirements which inspire the
   creation of this document and the assumptions which affect its scope
   in Section 2.  Section 3 presents an architectural model and
   describes its relationship to previous IETF and ISO/IEC/ITU
   standards.  In particular, this document's relationship with the IETF
   PEM specifications and the ISO/IEC/ITU X.509 documents are described.

   The specification profiles the X.509 version 3 certificate in Section
   4, and the X.509 version 2 certificate revocation list (CRL) in
   Section 5.  The profiles include the identification of ISO/IEC/ITU
   and ANSI extensions which may be useful in the Internet PKI.  The
   profiles are presented in the 1988 Abstract Syntax Notation One
   (ASN.1) rather than the 1994 syntax used in the ISO/IEC/ITU
   standards.

   This specification also includes path validation procedures in
   Section 6.  These procedures are based upon the ISO/IEC/ITU
   definition, but the presentation assumes one or more self-signed
   trusted CA certificates.  Implementations are required to derive the
   same results but are not required to use the specified procedures.

   Procedures for identification and encoding of public key materials
   and digital signatures are defined in [PKIX ALGS]. Implementations of
   this specification are not required to use any particular
   cryptographic algorithms.  However, conforming implementations which
   use the algorithms identified in [PKIX ALGS] are required to identify
   and encode the public key materials and digital signatures as
   described in that specification.

   Finally, three appendices are provided to aid implementers.  Appendix
   A contains all ASN.1 structures defined or referenced within this
   specification.  As above, the material is presented in the 1988
   Abstract Syntax Notation One (ASN.1) rather than the 1994 syntax.
   Appendix B contains notes on less familiar features of the ASN.1



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   notation used within this specification.  Appendix C contains
   examples of a conforming certificate and a conforming CRL.

2  Requirements and Assumptions

   The goal of this specification is to develop a profile to facilitate
   the 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,
   and IPsec.  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.

   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).

   A certificate user should review the certificate policy generated by
   the certification authority (CA) before relying on the authentication
   or non-repudiation services associated with the public key in a
   particular certificate.  To this end, this standard does not
   prescribe legally binding rules or duties.

   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 provide more appropriate methods 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
   availability.  In addition, the profile allows for the presence of
   firewall or other filtered communication.

   This profile does not assume the deployment of an X.500 Directory
   system.  The profile does not prohibit the use of an X.500 Directory,
   but other means of distributing certificates and certificate
   revocation lists (CRLs) may be used.



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2.2  Acceptability Criteria

   The goal of the Internet Public Key Infrastructure (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.

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, WWW servers, and the key manager for IPsec within a router.
   This profile recognizes the limitations of the platforms these users
   employ and the limitations in sophistication and attentiveness of the
   users themselves.  This manifests itself in minimal user
   configuration responsibility (e.g., trusted CA 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 user expectations, the Internet PKI profile is structured to
   support the individuals who generally operate CAs.  Providing
   administrators with unbounded choices increases the chances that a
   subtle CA administrator mistake will result in broad compromise.
   Also, unbounded choices greatly complicate the software that process
   and validate the certificates created by the CA.

3  Overview of Approach

   Following is a simplified view of the architectural model assumed by
   the PKIX specifications.















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       +---+
       | C |                       +------------+
       | e | <-------------------->| End entity |
       | r |       Operational     +------------+
       | t |       transactions          ^
       |   |      and management         |  Management
       | / |       transactions          |  transactions
       |   |                             |                PKI users
       | C |                             v
       | R |       -------------------+--+-----------+----------------
       | L |                          ^              ^
       |   |                          |              |  PKI management
       |   |                          v              |      entities
       | R |                       +------+          |
       | e | <---------------------| RA   | <---+    |
       | p |  Publish certificate  +------+     |    |
       | o |                                    |    |
       | s |                                    |    |
       | I |                                    v    v
       | t |                                +------------+
       | o | <------------------------------|     CA     |
       | r |   Publish certificate          +------------+
       | y |   Publish CRL                         ^
       |   |                                       |
       +---+                        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
                is the subject of a certificate;
   CA:          certification authority;
   RA:          registration authority, i.e., an optional system to
                which a CA delegates certain management 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
                entities.







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3.1  X.509 Version 3 Certificate

   Users of a public key require confidence that the associated private
   key is owned by 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 subjects.  The binding is asserted by having a trusted CA
   digitally sign each certificate. The CA may base this assertion upon
   technical means (a.k.a., proof of posession through a challenge-
   response protocol), presentation of the private key, or on an
   assertion by the subject.  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.

   ITU-T X.509 (formerly CCITT X.509) or ISO/IEC/ITU 9594-8, which was
   first published in 1988 as part of the X.500 Directory
   recommendations, defines a standard certificate format [X.509].  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.

   The Internet Privacy Enhanced Mail (PEM) RFCs, 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/ITU 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 June 1996,
   standardization of the basic v3 format was completed [X.509].

   ISO/IEC/ITU and ANSI X9 have also developed standard extensions for
   use in the v3 extensions field [X.509][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/ITU and ANSI X9 standard extensions are very
   broad in their applicability.  In order to develop interoperable
   implementations of X.509 v3 systems for Internet use, it is necessary



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   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,
   the CA's name, and related information (such as the validity period
   or name constraints), 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 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:

      (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
      shall 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 digital 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 uses the X.509 v1 certificate formats. The limitations
   of X.509 v1 required imposition of several structural restrictions to
   clearly associate policy information or restrict the utility of
   certificates.  These restrictions included:

      (a) a pure top-down hierarchy, with all certification paths
      starting from IPRA;

      (b) a naming subordination rule restricting the names of a CA's
      subjects; and

      (c) use of the PCA concept, which requires knowledge of individual
      PCAs to be built into certificate chain verification logic.
      Knowledge of individual PCAs was required to determine if a chain
      could be accepted.

   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.  As a result, this document supports a more flexible
   architecture, including:

      (a) Certification paths may start with a public key of a CA in a
      user's own domain, or with the public key of the top of a
      hierarchy.  Starting with the public key of a CA in a user's own
      domain has certain advantages.  In some environments, the local
      domain is the most trusted.

      (b)  Name constraints may be imposed through explicit inclusion of
      a name constraints extension in a certificate, but are not
      required.

      (c)  Policy extensions and policy mappings replace the PCA
      concept, which permits a greater degree of automation.  The
      application can determine if the certification path is acceptable



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      based on the contents of the certificates instead of a priori
      knowledge of PCAs. This permits automation of certificate chain
      processing.

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 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).  An entry is added to the CRL as part of the next update
   following notification of revocation. An entry may be removed from
   the CRL after appearing on one regularly scheduled CRL issued beyond
   the revoked certificate's validity period.

   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 all currently issued CRLs
   are updated -- this may be up to one hour, one day, or one week
   depending on the frequency that the CA issues CRLs.

   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



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   document to specify that profile.  However, this profile does not
   require CAs to issue CRLs.  Message formats and protocols supporting
   on-line revocation notification may be defined in other PKIX
   specifications.  On-line methods of revocation notification may be
   applicable in some environments as an alternative to the X.509 CRL.
   On-line revocation checking may significantly reduce the latency
   between a revocation report and the distribution of the information
   to relying parties.  Once the CA accepts the report as authentic and
   valid, any query to the on-line service will correctly reflect the
   certificate validation impacts of the revocation.  However, these
   methods impose new security requirements: the certificate validator
   needs to trust the on-line validation service while the repository
   does not need to be trusted.

3.4  Operational Protocols

   Operational protocols are required to deliver certificates and CRLs
   (or status information) to certificate using client systems.
   Provision is needed for a variety of different means of certificate
   and CRL delivery, including distribution procedures based on LDAP,
   HTTP, FTP, and X.500.  Operational protocols supporting these
   functions are defined in other PKIX specifications.  These
   specifications may include definitions of 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 PKI user and management entities.  For example, a 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 (directly, or through an RA), prior to that
      CA issuing  a certificate or certificates for that user.

      (b)  initialization:  Before a client system can operate securely
      it is necessary to install 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 and other assured information of
      the trusted CA(s), to be used in validating certificate paths.
      Furthermore, a client typically needs to be initialized with its
      own key pair(s).



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      (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
      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.  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
      abnormal situation requiring certificate revocation.

      (g)  cross-certification:  Two CAs exchange information used in
      establishing a cross-certificate. A cross-certificate is a
      certificate issued by one CA to another CA which contains a CA
      signature key used for issuing certificates.

   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 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.

   The PKIX series of specifications may define a set of standard
   message formats supporting the above functions in future
   specifications.  In that case, the protocols for conveying these
   messages in different environments (e.g., on-line, file transfer, e-
   mail, and WWW) will also be described in those specifications.

4  Certificate and Certificate Extensions Profile

   This section presents a profile for public key certificates that will
   foster interoperability and a reusable PKI.  This section is based
   upon the X.509 v3 certificate format and the standard certificate
   extensions defined in [X.509].  The ISO/IEC/ITU documents use the
   1993 version of ASN.1; while this document uses the 1988 ASN.1
   syntax, the encoded certificate and standard extensions are
   equivalent.  This section also defines private extensions required to



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   support a PKI for the Internet community.

   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 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.

4.1  Basic Certificate Fields

   The X.509 v3 certificate basic syntax is as follows.  For signature
   calculation, the certificate is encoded using the ASN.1 distinguished
   encoding rules (DER) [X.208].  ASN.1 DER encoding is a tag, length,
   value encoding system for each element.

   Certificate  ::=  SEQUENCE  {
        tbsCertificate       TBSCertificate,
        signatureAlgorithm   AlgorithmIdentifier,
        signatureValue       BIT STRING  }

   TBSCertificate  ::=  SEQUENCE  {
        version         [0]  EXPLICIT 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]  EXPLICIT Extensions OPTIONAL
                             -- If present, version MUST be v3
        }

   Version  ::=  INTEGER  {  v1(0), v2(1), v3(2)  }

   CertificateSerialNumber  ::=  INTEGER

   Validity ::= SEQUENCE {
        notBefore      Time,
        notAfter       Time }

   Time ::= CHOICE {



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        utcTime        UTCTime,
        generalTime    GeneralizedTime }

   UniqueIdentifier  ::=  BIT STRING

   SubjectPublicKeyInfo  ::=  SEQUENCE  {
        algorithm            AlgorithmIdentifier,
        subjectPublicKey     BIT STRING  }

   Extensions  ::=  SEQUENCE SIZE (1..MAX) OF Extension

   Extension  ::=  SEQUENCE  {
        extnID      OBJECT IDENTIFIER,
        critical    BOOLEAN DEFAULT FALSE,
        extnValue   OCTET STRING  }

   The following items describe the X.509 v3 certificate for use in the
   Internet.

4.1.1  Certificate Fields

   The Certificate is a SEQUENCE of three required fields. The fields
   are described in detail in the following subsections.

4.1.1.1  tbsCertificate

   The field contains the names of the subject and issuer, a public key
   associated with the subject, a validity period, and other associated
   information.  The fields are described in detail in section 4.1.2;
   the tbscertificate may also include extensions which are described in
   section 4.2.

4.1.1.2  signatureAlgorithm

   The signatureAlgorithm field contains the identifier for the
   cryptographic algorithm used by the CA to sign this certificate.
   [PKIX ALGS] lists the supported signature algorithms.

   An algorithm identifier is defined by the following ASN.1 structure:

   AlgorithmIdentifier  ::=  SEQUENCE  {
        algorithm               OBJECT IDENTIFIER,
        parameters              ANY DEFINED BY algorithm OPTIONAL  }

   The algorithm identifier is used to identify a cryptographic
   algorithm.  The OBJECT IDENTIFIER component identifies the algorithm
   (such as DSA with SHA-1).  The contents of the optional parameters
   field will vary according to the algorithm identified. [PKIX ALGS]



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   lists the supported algorithms for this specification.

   This field MUST contain the same algorithm identifier as the
   signature field in the sequence tbsCertificate (see sec. 4.1.2.3).

4.1.1.3  signatureValue

   The signatureValue field contains a digital signature computed upon
   the ASN.1 DER encoded tbsCertificate.  The ASN.1 DER encoded
   tbsCertificate is used as the input to the signature function. This
   signature value is then ASN.1 encoded as a BIT STRING and included in
   the Certificate's signature field. The details of this process are
   specified for each of the supported algorithms in [PKIX ALGS].

   By generating this signature, a CA certifies the validity of the
   information in the tbsCertificate field.  In particular, the CA
   certifies the binding between the public key material and the subject
   of the certificate.

4.1.2  TBSCertificate

   The sequence TBSCertificate contains information associated with the
   subject of the certificate and the CA who issued it.  Every
   TBSCertificate contains the names of the subject and issuer, a public
   key associated with the subject, a validity period, a version number,
   and a serial number; some may contain optional unique identifier
   fields.  The remainder of this section describes the syntax and
   semantics of these fields.  A TBSCertificate may also include
   extensions.  Extensions for the Internet PKI are described in Section
   4.2.

4.1.2.1  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 omitted from the certificate as
   the default value).

   Implementations SHOULD be prepared to accept any version certificate.
   At a minimum, conforming implementations MUST recognize version 3
   certificates.

   Generation of version 2 certificates is not expected by
   implementations based on this profile.





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4.1.2.2  Serial number

   The serial number MUST be a positive integer assigned by the CA 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).  CAs MUST force the serialNumber to be a non-negative
   integer.

   Given the uniqueness requirements above serial numbers can be
   expected to contain long integers. Certificate users MUST be able to
   handle serialNumber values up to 20 octets. Conformant CAs MUST NOT
   use serialNumber values longer than 20 octets.

   Note: Non-conforming CAs may issue certificates with serial numbers
   that are negative, or zero.  Certificate users SHOULD be prepared to
   handle such certificates.

4.1.2.3  Signature

   This field contains the algorithm identifier for the algorithm used
   by the CA to sign the certificate.

   This field MUST contain the same algorithm identifier as the
   signatureAlgorithm field in the sequence Certificate (see sec.
   4.1.1.2).  The contents of the optional parameters field will vary
   according to the algorithm identified.  [PKIX ALGS] lists the
   supported signature algorithms.

4.1.2.4  Issuer

   The issuer field identifies the entity who has signed and issued the
   certificate.  The issuer field MUST contain a non-empty distinguished
   name (DN).  The issuer field is defined as the X.501 type Name.
   [X.501] Name is defined by the following ASN.1 structures:

   Name ::= CHOICE {
     RDNSequence }

   RDNSequence ::= SEQUENCE OF RelativeDistinguishedName

   RelativeDistinguishedName ::=
     SET OF AttributeTypeAndValue

   AttributeTypeAndValue ::= SEQUENCE {
     type     AttributeType,
     value    AttributeValue }

   AttributeType ::= OBJECT IDENTIFIER



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   AttributeValue ::= ANY DEFINED BY AttributeType

   DirectoryString ::= CHOICE {
         teletexString           TeletexString (SIZE (1..MAX)),
         printableString         PrintableString (SIZE (1..MAX)),
         universalString         UniversalString (SIZE (1..MAX)),
         utf8String              UTF8String (SIZE (1.. MAX)),
         bmpString               BMPString (SIZE (1..MAX)) }

   The Name describes a hierarchical name composed of attributes, such
   as country name, and corresponding values, such as US.  The type of
   the component AttributeValue is determined by the AttributeType; in
   general it will be a DirectoryString.

   The DirectoryString type is defined as a choice of PrintableString,
   TeletexString, BMPString, UTF8String, and UniversalString.  The
   UTF8String encoding is the preferred encoding, and all certificates
   issued after December 31, 2003 MUST use the UTF8String encoding of
   DirectoryString (except as noted below).  Until that date, conforming
   CAs MUST choose from the following options when creating a
   distinguished name, including their own:

      (a) if the character set is sufficient, the string MAY be
      represented as a PrintableString;

      (b) failing (a), if the BMPString character set is sufficient the
      string MAY be represented as a BMPString; and

      (c) failing (a) and (b), the string MUST be represented as a
      UTF8String.  If (a) or (b) is satisfied, the CA MAY still choose
      to represent the string as a UTF8String.

   Exceptions to the December 31, 2003 UTF8 encoding requirements are as
   follows:

      (a) CAs MAY issue "name rollover" certificates to support an
      orderly migration to UTF8String encoding.  Such certificates would
      include the CA's UTF8String encoded name as issuer and and the old
      name encoding as subject, or vice-versa.

      (b) As stated in section 4.1.2.6, the subject field MUST be
      populated with a non-empty distinguished name matching the
      contents of the issuer field in all certificates issued by the
      subject CA regardless of encoding.

   The TeletexString and UniversalString are included for backward
   compatibility, and should not be used for certificates for new



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   subjects.  However, these types may be used in certificates where the
   name was previously established.  Certificate users SHOULD be
   prepared to receive certificates with these types.

   In addition, many legacy implementations support names encoded in the
   ISO 8859-1 character set (Latin1String) but tag them as
   TeletexString.  The Latin1String includes characters used in Western
   European countries which are not part of the TeletexString charcter
   set.  Implementations that process TeletexString SHOULD be prepared
   to handle the entire ISO 8859-1 character set.[ISO 8859-1]

   As noted above, distinguished names are composed of attributes.  This
   specification does not restrict the set of attribute types that may
   appear in names.  However, conforming implementations MUST be
   prepared to receive certificates with issuer names containing the set
   of attribute types defined below.  This specification also recommends
   support for additional attribute types.

   Standard sets of attributes have been defined in the X.500 series of
   specifications.[X.520]  Implementations of this specification MUST be
   prepared to receive the following standard attribute types in issuer
   and subject (see 4.1.2.6) names:

      * country,
      * organization,
      * organizational-unit,
      * distinguished name qualifier,
      * state or province name,
      * common name (e.g., "Susan Housley"), and
      * serial number.

   In addition, implementations of this specification SHOULD be prepared
   to receive the following standard attribute types in issuer and
   subject names:

      * locality,
      * title,
      * surname,
      * given name,
      * initials,
      * pseudonym, and
      * generation qualifier (e.g., "Jr.", "3rd", or "IV").

   The syntax and associated object identifiers (OIDs) for these
   attribute types are provided in the ASN.1 modules in Appendices A and
   B.

   In addition, implementations of this specification MUST be prepared



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   to receive the domainComponent attribute, as defined in [RFC 2247].
   The Domain (Nameserver) System (DNS) provides a hierarchical resource
   labeling system.  This attribute provides is a convenient mechanism
   for organizations that wish to use DNs that parallel their DNS names.
   This is not a replacement for the dNSName component of the
   alternative name field. Implementations are not required to convert
   such names into DNS names. The syntax and associated OID for this
   attribute type is provided in the ASN.1 modules in Appendices A and
   B.

   Certificate users MUST be prepared to process the issuer
   distinguished name and subject distinguished name (see sec. 4.1.2.6)
   fields to perform name chaining for certification path validation
   (see section 6). Name chaining is performed by matching the issuer
   distinguished name in one certificate with the subject name in a CA
   certificate.

   This specification requires only a subset of the name comparison
   functionality specified in the X.500 series of specifications.  The
   requirements for conforming implementations are as follows:

      (a) attribute values encoded in different types (e.g.,
      PrintableString and BMPString) may be assumed to represent
      different strings;

      (b) attribute values in types other than PrintableString are case
      sensitive (this permits matching of attribute values as binary
      objects);

      (c) attribute values in PrintableString are not case sensitive
      (e.g., "Marianne Swanson" is the same as "MARIANNE SWANSON"); and

      (d) attribute values in PrintableString are compared after
      removing leading and trailing white space and converting internal
      substrings of one or more consecutive white space characters to a
      single space.

   These name comparison rules permit a certificate user to validate
   certificates issued using languages or encodings unfamiliar to the
   certificate user.

   In addition, implementations of this specification MAY use these
   comparison rules to process unfamiliar attribute types for name
   chaining. This allows implementations to process certificates with
   unfamiliar attributes in the issuer name.

   Note that the comparison rules defined in the X.500 series of
   specifications indicate that the character sets used to encode data



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   in distinguished names are irrelevant.  The characters themselves are
   compared without regard to encoding. Implementations of the profile
   are permitted to use the comparison algorithm defined in the X.500
   series.  Such an implementation will recognize a superset of name
   matches recognized by the algorithm specified above.

4.1.2.5  Validity

   The certificate validity period is the time interval during which the
   CA warrants that it will maintain information about the status of the
   certificate. The field is represented as a SEQUENCE of two dates: the
   date on which the certificate validity period begins (notBefore) and
   the date on which the certificate validity period ends (notAfter).
   Both notBefore and notAfter may be encoded as UTCTime or
   GeneralizedTime.

   CAs conforming to this profile MUST always encode certificate
   validity dates through the year 2049 as UTCTime; certificate validity
   dates in 2050 or later MUST be encoded as GeneralizedTime.

   The validity period for a certificate is the period of time from
   notBefore through notAfter, inclusive.

4.1.2.5.1  UTCTime

   The universal time type, UTCTime, is a standard ASN.1 type intended
   for representation of dates and time.  UTCTime specifies the year
   through the two low order digits and time is specified to the
   precision of one minute or one second.  UTCTime includes either Z
   (for Zulu, or Greenwich Mean Time) or a time differential.

   For the purposes of this profile, UTCTime values MUST be expressed
   Greenwich Mean Time (Zulu) and MUST include seconds (i.e., times are
   YYMMDDHHMMSSZ), even where the number of seconds is zero.  Conforming
   systems MUST interpret the year field (YY) as follows:

      Where YY is greater than or equal to 50, the year SHALL be
      interpreted as 19YY; and

      Where YY is less than 50, the year SHALL be interpreted as 20YY.

4.1.2.5.2  GeneralizedTime

   The generalized time type, GeneralizedTime, is a standard ASN.1 type
   for variable precision representation of time.  Optionally, the
   GeneralizedTime field can include a representation of the time
   differential between local and Greenwich Mean Time.




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   For the purposes of this profile, GeneralizedTime values MUST be
   expressed Greenwich Mean Time (Zulu) and MUST include seconds (i.e.,
   times are YYYYMMDDHHMMSSZ), even where the number of seconds is zero.
   GeneralizedTime values MUST NOT include fractional seconds.

4.1.2.6  Subject

   The subject field identifies the entity associated with the public
   key stored in the subject public key field.  The subject name may be
   carried in the subject field and/or the subjectAltName extension.  If
   the subject is a CA (e.g., the basic constraints extension, as
   discussed in 4.2.1.10, is present and the value of cA is TRUE,) then
   the subject field MUST be populated with a non-empty distinguished
   name matching the contents of the issuer field (see sec. 4.1.2.4) in
   all certificates issued by the subject CA.  If subject naming
   information is present only in the subjectAltName extension (e.g., a
   key bound only to an email address or URI), then the subject name
   MUST be an empty sequence and the subjectAltName extension MUST be
   critical.

   Where it is non-empty, the subject field MUST contain an X.500
   distinguished name (DN). The DN MUST be unique for each subject
   entity certified by the one CA as defined by the issuer name field. A
   CA may issue more than one certificate with the same DN to the same
   subject entity.

   The subject name field is defined as the X.501 type Name.
   Implementation requirements for this field are those defined for the
   issuer field (see sec.  4.1.2.4).  When encoding attribute values of
   type DirectoryString, the encoding rules for the issuer field MUST be
   implemented.  Implementations of this specification MUST be prepared
   to receive subject names containing the attribute types required for
   the issuer field.  Implementations of this specification SHOULD be
   prepared to receive subject names containing the recommended
   attribute types for the issuer field.  The syntax and associated
   object identifiers (OIDs) for these attribute types are provided in
   the ASN.1 modules in Appendices A and B.  Implementations of this
   specification MAY use these comparison rules to process unfamiliar
   attribute types (i.e., for name chaining). This allows
   implementations to process certificates with unfamiliar attributes in
   the subject name.

   In addition, legacy implementations exist where an RFC 822 name is
   embedded in the subject distinguished name as an EmailAddress
   attribute.  The attribute value for EmailAddress is of type IA5String
   to permit inclusion of the character '@', which is not part of the
   PrintableString character set.  EmailAddress attribute values are not
   case sensitive (e.g., "fanfeedback@redsox.com" is the same as



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   "FANFEEDBACK@REDSOX.COM").

   Conforming implementations generating new certificates with
   electronic mail addresses MUST use the rfc822Name in the subject
   alternative name field (see sec. 4.2.1.7) to describe such
   identities.  Simultaneous inclusion of the EmailAddress attribute in
   the subject distinguished name to support legacy implementations is
   deprecated but permitted.

4.1.2.7  Subject Public Key Info

   This field is used to carry the public key and identify the algorithm
   with which the key is used. The algorithm is identified using the
   AlgorithmIdentifier structure specified in section 4.1.1.2. The
   object identifiers for the supported algorithms and the methods for
   encoding the public key materials (public key and parameters) are
   specified in [PKIX ALGS].

4.1.2.8  Unique Identifiers

   These fields may only appear if the version is 2 or 3 (see sec.
   4.1.2.1).  These fields MUST NOT appear if the version is 1.  The
   subject and issuer unique identifiers are present in the certificate
   to handle the possibility of reuse of subject and/or issuer names
   over time.  This profile RECOMMENDS that names not be reused for
   different entities and that Internet certificates not make use of
   unique identifiers.  CAs conforming to this profile SHOULD NOT
   generate certificates with unique identifiers.  Applications
   conforming to this profile SHOULD be capable of parsing unique
   identifiers and making comparisons.

4.1.2.9  Extensions

   This field may only appear if the version is 3 (see sec. 4.1.2.1).
   If present, this field is a SEQUENCE of one or more certificate
   extensions.  The format and content of certificate extensions in the
   Internet PKI is defined in section 4.2.

4.2  Standard Certificate Extensions

   The extensions defined for X.509 v3 certificates provide methods for
   associating additional attributes with users or public keys and for
   managing the certification hierarchy.  The X.509 v3 certificate
   format also allows communities to define private extensions to carry
   information unique to those communities.  Each extension in a
   certificate may be designated as critical or non-critical.  A
   certificate using system MUST reject the certificate if it encounters
   a critical extension it does not recognize; however, a non-critical



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   extension may be ignored if it is not recognized.  The following
   sections present 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 prevent use in a general context.

   Each extension includes an OID and an ASN.1 structure.  When an
   extension appears in a certificate, the OID appears as the field
   extnID and the corresponding ASN.1 encoded structure is the value of
   the octet string extnValue.  Only one instance of a particular
   extension may appear in a particular certificate. For example, a
   certificate may contain only one authority key identifier extension
   (see sec. 4.2.1.1).  An extension includes the boolean critical, with
   a default value of FALSE.  The text for each extension specifies the
   acceptable values for the critical field.

   Conforming CAs MUST support key identifiers (see sec. 4.2.1.1 and
   4.2.1.2), basic constraints (see sec. 4.2.1.10), key usage (see sec.
   4.2.1.3), and certificate policies (see sec. 4.2.1.5) extensions. If
   the CA issues certificates with an empty sequence for the subject
   field, the CA MUST support the subject alternative name extension
   (see sec. 4.2.1.7).  Support for the remaining extensions is
   OPTIONAL. Conforming CAs may support extensions that are not
   identified within this specification; certificate issuers are
   cautioned that marking such extensions as critical may inhibit
   interoperability.

   At a minimum, applications conforming to this profile MUST recognize
   the following extensions: key usage (see sec. 4.2.1.3), certificate
   policies (see sec. 4.2.1.5), the subject alternative name (see sec.
   4.2.1.7), basic constraints (see sec. 4.2.1.10), name constraints
   (see sec. 4.2.1.11), policy constraints (see sec. 4.2.1.12), extended
   key usage (see sec. 4.2.1.13), and inhibit any-policy (see sec.
   4.2.1.15).

   In addition, this profile RECOMMENDS application support for the
   authority and subject key identifier (see sec. 4.2.1.1 and 4.2.1.2),
   and policy mapping (see sec. 4.2.1.6) extensions.

4.2.1  Standard Extensions

   This section identifies standard certificate extensions defined in
   [X.509] for use in the Internet PKI.  Each extension is associated
   with an OID defined in [X.509].  These OIDs are members of the id-ce
   arc, which is defined by the following:

   id-ce   OBJECT IDENTIFIER ::=  {joint-iso-ccitt(2) ds(5) 29}



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4.2.1.1  Authority Key Identifier

   The authority key identifier extension provides a means of
   identifying the public key corresponding to the private key used to
   sign a certificate. This extension is used where an issuer has
   multiple signing keys (either due to multiple concurrent key pairs or
   due to changeover).  The identification may be based on either the
   key identifier (the subject key identifier in the issuer's
   certificate) or on the issuer name and serial number.

   The keyIdentifier field of the authorityKeyIdentifier extension MUST
   be included in all certificates generated by conforming CAs to
   facilitate chain building.  There is one exception; where a CA
   distributes its public key in the form of a "self-signed"
   certificate, the authority key identifier may be omitted.  In this
   case, the subject and authority key identifiers would be identical.

   The value of the keyIdentifier field SHOULD be derived from the
   public key used to verify the certificate's signature or a method
   that generates unique values.  Two common methods for generating key
   identifiers from the public key are described in (sec. 4.2.1.2). One
   common method for generating unique values is described in (sec.
   4.2.1.2).  Where a key identifier has not been previously
   established, this specification recommends use of one of these
   methods for generating keyIdentifiers.

   This profile recommends support for the key identifier method by all
   certificate users.

   This extension MUST NOT be marked critical.

   id-ce-authorityKeyIdentifier OBJECT IDENTIFIER ::=  { id-ce 35 }

   AuthorityKeyIdentifier ::= SEQUENCE {
      keyIdentifier             [0] KeyIdentifier           OPTIONAL,
      authorityCertIssuer       [1] GeneralNames            OPTIONAL,
      authorityCertSerialNumber [2] CertificateSerialNumber OPTIONAL  }

   KeyIdentifier ::= OCTET STRING

4.2.1.2  Subject Key Identifier

   The subject key identifier extension provides a means of identifying
   certificates that contain a particular public key.

   To facilitate chain building, this extension MUST appear in all con-
   forming CA certificates, that is, all certificates including the
   basic constraints extension (see sec. 4.2.1.10) where the value of cA



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   is TRUE.  The value of the subject key identifier MUST be the value
   placed in the key identifier field of the Authority Key Identifier
   extension (see sec. 4.2.1.1) of certificates issued by the subject of
   this certificate.

   For CA certificates, subject key identifiers SHOULD be derived from
   the public key or a method that generates unique values.  The key
   identifier is an explicit value placed in the certificate by the
   issuer, not a value generated by a certificate user.  Two common
   methods for generating key identifiers from the public key are:

      (1) The keyIdentifier is composed of the 160-bit SHA-1 hash of the
      value of the BIT STRING subjectPublicKey (excluding the tag,
      length, and number of unused bits).

      (2) The keyIdentifier is composed of a four bit type field with
      the value 0100 followed by the least significant 60 bits of the
      SHA-1 hash of the value of the BIT STRING subjectPublicKey.

   One common method for generating unique values is a monotonically
   increasing sequence of integers.

   For end entity certificates, the subject key identifier extension
   provides a means for identifying certificates containing the
   particular public key used in an application. Where an end entity has
   obtained multiple certificates, especially from multiple CAs, the
   subject key identifier provides a means to quickly identify the set
   of certificates containing a particular public key. To assist
   applications in identifying the appropriate end entity certificate,
   this extension SHOULD be included in all end entity certificates.

   For end entity certificates, subject key identifiers SHOULD be
   derived from the public key.  Two common methods for generating key
   identifiers from the public key are identifed above.

   Where a key identifier has not been previously established, this
   specification recommends use of one of these methods for generating
   keyIdentifiers.

   This extension MUST NOT be marked critical.

   id-ce-subjectKeyIdentifier OBJECT IDENTIFIER ::=  { id-ce 14 }

   SubjectKeyIdentifier ::= KeyIdentifier







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4.2.1.3  Key Usage

   The key usage extension defines the purpose (e.g., encipherment,
   signature, certificate signing) of the key contained in the
   certificate.  The usage restriction might be employed when a key that
   could be used for more than one operation is to be restricted.  For
   example, when an RSA key should be used only for signing, the
   digitalSignature and/or nonRepudiation bits would be asserted.
   Likewise, when an RSA key should be used only for key management, the
   keyEncipherment bit would be asserted. When used, this extension
   SHOULD be marked critical.

      id-ce-keyUsage OBJECT IDENTIFIER ::=  { id-ce 15 }

      KeyUsage ::= BIT STRING {
           digitalSignature        (0),
           nonRepudiation          (1),
           keyEncipherment         (2),
           dataEncipherment        (3),
           keyAgreement            (4),
           keyCertSign             (5),
           cRLSign                 (6),
           encipherOnly            (7),
           decipherOnly            (8) }


   Bits in the KeyUsage type are used as follows:

      The digitalSignature bit is asserted when the subject public key
      is used with a digital signature mechanism to support security
      services other than non-repudiation (bit 1), certificate signing
      (bit 5), or revocation information signing (bit 6). Digital
      signature mechanisms are often used for entity authentication and
      data origin authentication with integrity.

      The nonRepudiation bit is asserted when the subject public key is
      used to verify digital signatures used to provide a non-
      repudiation service which protects against the signing entity
      falsely denying some action, excluding certificate or CRL signing.
      In the case of later conflict, a reliable third party may
      determine the authenticity of the signed data.

      Further distinctions between the digitalSignature and
      nonRepudiation bits may be provided in specific certificate
      policies.

      The keyEncipherment bit is asserted when the subject public key is
      used for key transport.  For example, when an RSA key is to be



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      used for key management, then this bit is set.

      The dataEncipherment bit is asserted when the subject public key
      is used for enciphering user data, other than cryptographic keys.

      The keyAgreement bit is asserted when the subject public key is
      used for key agreement.  For example, when a Diffie-Hellman key is
      to be used for key management, then this bit is set.

      The keyCertSign bit is asserted when the subject public key is
      used for verifying a signature on certificates.  This bit may only
      be asserted in CA certificates.  If the keyCertSign bit is
      asserted, then the cA bit in the basic constraints extension (see
      4.2.1.10) MUST also be asserted.  If neither the cRLSign bit nor
      the keyCertSign bit are asserted, then the cA bit in the basic
      constraints extension MUST NOT be asserted.

      The cRLSign bit is asserted when the subject public key is used
      for verifying a signature on revocation information (e.g., a CRL).
      This bit may only be asserted in CA certificates.  If the cRLSign
      bit is asserted, then the cA bit in the basic constraints
      extension (see 4.2.1.10) MUST also be asserted.  If neither the
      cRLSign bit nor the keyCertSign bit are asserted, then the cA bit
      in the basic constraints extension MUST NOT be asserted.

      The meaning of the encipherOnly bit is undefined in the absence of
      the keyAgreement bit.  When the encipherOnly bit is asserted and
      the keyAgreement bit is also set, the subject public key may be
      used only for enciphering data while performing key agreement.

      The meaning of the decipherOnly bit is undefined in the absence of
      the keyAgreement bit.  When the decipherOnly bit is asserted and
      the keyAgreement bit is also set, the subject public key may be
      used only for deciphering data while performing key agreement.

   This profile does not restrict the combinations of bits that may be
   set in An instantiation of the keyUsage extension.  However,
   appropriate values for keyUsage extensions for particular algorithms
   are specified in [PKIX ALGS].

4.2.1.4  Private Key Usage Period

   This profile RECOMMENDS against the use of this extension.  CAs
   conforming to this profile MUST NOT generate certificates with
   critical private key usage period extensions.

   The private key usage period extension allows the certificate issuer
   to specify a different validity period for the private key than the



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   certificate. This extension is intended for use with digital
   signature keys.  This extension consists of two optional components,
   notBefore and notAfter.  The private key associated with the
   certificate should not be used to sign objects before or after the
   times specified by the two components, respectively. CAs conforming
   to this profile MUST NOT generate certificates with private key usage
   period extensions unless at least one of the two components is
   present.

   Where used, notBefore and notAfter are represented as GeneralizedTime
   and MUST be specified and interpreted as defined in section
   4.1.2.5.2.

   id-ce-privateKeyUsagePeriod OBJECT IDENTIFIER ::=  { id-ce 16 }

   PrivateKeyUsagePeriod ::= SEQUENCE {
        notBefore       [0]     GeneralizedTime OPTIONAL,
        notAfter        [1]     GeneralizedTime OPTIONAL }

4.2.1.5  Certificate Policies

   The certificate policies extension contains a sequence of one or more
   policy information terms, each of which consists of an object
   identifier (OID) and optional qualifiers.  Optional qualifiers, which
   may be present, are not expected to change the definition of the
   policy.

   In an end-entity certificate, these policy information terms indicate
   the policy under which the certificate has been issued and the
   purposes for which the certificate may be used.  In a CA certificate,
   these policy information terms limit the set of policies for
   certification paths which include this certificate.  When a CA does
   not wish to limit the set of policies for certification paths which
   include this certificate, they may assert the special policy
   anyPolicy, with a value of {2 5 29 32 0}.

   Applications with specific policy requirements are expected to have a
   list of those policies which they will accept and to compare the
   policy OIDs in the certificate to that list.  If this extension is
   critical, the path validation software MUST be able to interpret this
   extension (including the optional qualifier), or MUST reject the
   certificate.

   To promote interoperability, this profile RECOMMENDS that policy
   information terms consist of only an OID.  Where an OID alone is
   insufficient, this profile strongly recommends that use of qualifiers
   be limited to those identified in this section.  When qualifiers are
   used with the special policy anyPolicy, they MUST be limited to the



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   qualifers identified in this section.

   This specification defines two policy qualifier types for use by
   certificate policy writers and certificate issuers. The qualifier
   types are the CPS Pointer and User Notice qualifiers.

   The CPS Pointer qualifier contains a pointer to a Certification
   Practice Statement (CPS) published by the CA.  The pointer is in the
   form of a URI.  Processing requirements for this qualifier are a
   local matter.  No action is mandated by this specification regardless
   of the criticality value asserted for the extension.

   User notice is intended for display to a relying party when a
   certificate is used.  The application software SHOULD display all
   user notices in all certificates of the certification path used,
   except that if a notice is duplicated only one copy need be
   displayed.  To prevent such duplication, this qualifier SHOULD only
   be present in end-entity certificates and CA certificates issued to
   other organizations.

   The user notice has two optional fields: the noticeRef field and the
   explicitText field.

      The noticeRef field, if used, names an organization and
      identifies, by number, a particular textual statement prepared by
      that organization.  For example, it might identify the
      organization "CertsRUs" and notice number 1.  In a typical
      implementation, the application software will have a notice file
      containing the current set of notices for CertsRUs; the
      application will extract the notice text from the file and display
      it.  Messages may be multilingual, allowing the software to select
      the particular language message for its own environment.

      An explicitText field includes the textual statement directly in
      the certificate.  The explicitText field is a string with a
      maximum size of 200 characters.

   If both the noticeRef and explicitText options are included in the
   one qualifier and if the application software can locate the notice
   text indicated by the noticeRef option then that text should be
   displayed; otherwise, the explicitText string should be displayed.

   id-ce-certificatePolicies OBJECT IDENTIFIER ::=  { id-ce 32 }

   anyPolicy OBJECT IDENTIFIER ::= {id-ce-certificate-policies 0}

   certificatePolicies ::= SEQUENCE SIZE (1..MAX) OF PolicyInformation




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   PolicyInformation ::= SEQUENCE {
        policyIdentifier   CertPolicyId,
        policyQualifiers   SEQUENCE SIZE (1..MAX) OF
                                PolicyQualifierInfo OPTIONAL }

   CertPolicyId ::= OBJECT IDENTIFIER

   PolicyQualifierInfo ::= SEQUENCE {
        policyQualifierId  PolicyQualifierId,
        qualifier          ANY DEFINED BY policyQualifierId }

   -- policyQualifierIds for Internet policy qualifiers

   id-qt          OBJECT IDENTIFIER ::=  { id-pkix 2 }
   id-qt-cps      OBJECT IDENTIFIER ::=  { id-qt 1 }
   id-qt-unotice  OBJECT IDENTIFIER ::=  { id-qt 2 }

   PolicyQualifierId ::=
        OBJECT IDENTIFIER ( id-qt-cps | id-qt-unotice )

   Qualifier ::= CHOICE {
        cPSuri           CPSuri,
        userNotice       UserNotice }

   CPSuri ::= IA5String

   UserNotice ::= SEQUENCE {
        noticeRef        NoticeReference OPTIONAL,
        explicitText     DisplayText OPTIONAL}

   NoticeReference ::= SEQUENCE {
        organization     DisplayText,
        noticeNumbers    SEQUENCE OF INTEGER }

   DisplayText ::= CHOICE {
        ia5String        IA5String      (SIZE (1..200)),
        visibleString    VisibleString  (SIZE (1..200)),
        bmpString        BMPString      (SIZE (1..200)),
        utf8String       UTF8String     (SIZE (1..200)) }

4.2.1.6  Policy Mappings

   This extension is used in CA certificates.  It lists one or more
   pairs of OIDs; each pair includes an issuerDomainPolicy and a
   subjectDomainPolicy. The pairing indicates the issuing CA considers
   its issuerDomainPolicy equivalent to the subject CA's
   subjectDomainPolicy.




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   The issuing CA's users may accept an issuerDomainPolicy for certain
   applications. The policy mapping tells the issuing CA's users which
   policies associated with the subject CA are comparable to the policy
   they accept.

   Each issuerDomainPolicy named in the the policy mapping extension
   should also be asserted in a certificate policies extension in the
   same certificate.  Policies should not be mapped either to or from
   the special value anyPolicy. (See 4.2.1.5 certificate policies).

   This extension may be supported by CAs and/or applications, and it
   MUST be non-critical.

   id-ce-policyMappings OBJECT IDENTIFIER ::=  { id-ce 33 }

   PolicyMappings ::= SEQUENCE SIZE (1..MAX) OF SEQUENCE {
        issuerDomainPolicy      CertPolicyId,
        subjectDomainPolicy     CertPolicyId }

4.2.1.7  Subject Alternative Name

   The subject alternative names extension allows additional identities
   to be bound to the subject of the certificate.  Defined options
   include an Internet electronic mail address, a DNS name, an IP
   address, and a uniform resource identifier (URI).  Other options
   exist, including completely local definitions.  Multiple name forms,
   and multiple instances of each name form, may be included.  Whenever
   such identities are to be bound into a certificate, the subject
   alternative name (or issuer alternative name) extension MUST be used.

   Because the subject alternative name is considered to be definitively
   bound to the public key, all parts of the subject alternative name
   MUST be verified by the CA.

   Further, if the only subject identity included in the certificate is
   an alternative name form (e.g., an electronic mail address), then the
   subject distinguished name MUST be empty (an empty sequence), and the
   subjectAltName extension MUST be present. If the subject field
   contains an empty sequence, the subjectAltName extension MUST be
   marked critical.

   When the subjectAltName extension contains an Internet mail address,
   the address MUST be included as an rfc822Name.  The format of an
   rfc822Name is an "addr-spec" as defined in RFC 822 [RFC 822]. An
   addr-spec has the form "local-part@domain". Note that an addr-spec
   has no phrase (such as a common name) before it, has no comment (text
   surrounded in parentheses) after it, and is not surrounded by "<" and
   ">".  Note that while upper and lower case letters are allowed in an



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   RFC 822 addr-spec, no significance is attached to the case.

   When the subjectAltName extension contains a iPAddress, the address
   MUST be stored in the octet string in "network byte order," as
   specified in RFC 791 [RFC 791]. The least significant bit (LSB) of
   each octet is the LSB of the corresponding byte in the network
   address. For IP Version 4, as specified in RFC 791, the octet string
   MUST contain exactly four octets.  For IP Version 6, as specified in
   RFC 1883, the octet string MUST contain exactly sixteen octets [RFC
   1883].

   When the subjectAltName extension contains a domain name service
   label, the domain name MUST be stored in the dNSName (an IA5String).
   The name MUST be in the "preferred name syntax," as specified by RFC
   1034 [RFC 1034]. Note that while upper and lower case letters are
   allowed in domain names, no signifigance is attached to the case.  In
   addition, while the string " " is a legal domain name, subjectAltName
   extensions with a dNSName " " are not permitted.  Finally, the use of
   the DNS representation for Internet mail addresses (wpolk.nist.gov
   instead of wpolk@nist.gov) MUST NOT be used; such identities are to
   be encoded as rfc822Name.

   Note: work is currently underway to specify domain names in
   international character sets.  This names will likely not be
   accomodated by IA5String.  Once this work is complete, this profile
   will be revisited and the appropriate functionality will be added.

   When the subjectAltName extension contains a URI, the name MUST be
   stored in the uniformResourceIdentifier (an IA5String). The name MUST
   be a non-relative URL, and MUST follow the URL syntax and encoding
   rules specified in [RFC 1738].  The name must include both a scheme
   (e.g., "http" or "ftp") and a scheme-specific-part.  The scheme-
   specific-part must include a fully qualified domain name or IP
   address as the host.

   As specified in [RFC 1738], the scheme name is not case-sensitive
   (e.g., "http" is equivalent to "HTTP").  The host part is also not
   case-sensitive, but other components of the scheme-specific-part may
   be case-sensitive.  When comparing URIs, conforming implementations
   MUST compare the scheme and host without regard to case, but assume
   the remainder of the scheme-specific-part is case sensitive.

   When the subjectAltName extension contains a DN in the directoryName,
   the DN MUST be unique for each subject entity certified by the one CA
   as defined by the issuer name field. A CA may issue more than one
   certificate with the same DN to the same subject entity.

   The subjectAltName may carry additional name types through the use of



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   the otherName field.  The format and semantics of the name are
   indicated through the OBJECT IDENTIFIER in the type-id field.  The
   name itself is conveyed as value field in otherName.  For example,
   Kerberos [RFC 1510] format names can be encoded into the otherName,
   using the krb5PrincipalName OID and the KerberosName syntax as
   defined in [PKINIT].

   Subject alternative names may be constrained in the same manner as
   subject distinguished names using the name constraints extension as
   described in section 4.2.1.11.

   If the subjectAltName extension is present, the sequence MUST contain
   at least one entry.  Unlike the subject field, conforming CAs MUST
   NOT issue certificates with subjectAltNames containing empty
   GeneralName fields. For example, an rfc822Name is represented as an
   IA5String. While an empty string is a valid IA5String, such an
   rfc822Name is not permitted by this profile.  The behavior of clients
   that encounter such a certificate when processing a certificication
   path is not defined by this profile.

   Finally, the semantics of subject alternative names that include
   wildcard characters (e.g., as a placeholder for a set of names) are
   not addressed by this specification.  Applications with specific
   requirements may use such names but MUST define the semantics.


      id-ce-subjectAltName OBJECT IDENTIFIER ::=  { id-ce 17 }

      SubjectAltName ::= GeneralNames

      GeneralNames ::= SEQUENCE SIZE (1..MAX) OF GeneralName

      GeneralName ::= CHOICE {
           otherName                       [0]     OtherName,
           rfc822Name                      [1]     IA5String,
           dNSName                         [2]     IA5String,
           x400Address                     [3]     ORAddress,
           directoryName                   [4]     Name,
           ediPartyName                    [5]     EDIPartyName,
           uniformResourceIdentifier       [6]     IA5String,
           iPAddress                       [7]     OCTET STRING,
           registeredID                    [8]     OBJECT IDENTIFIER}

      OtherName ::= SEQUENCE {
           type-id    OBJECT IDENTIFIER,
           value      [0] EXPLICIT ANY DEFINED BY type-id }

      EDIPartyName ::= SEQUENCE {



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           nameAssigner            [0]     DirectoryString OPTIONAL,
           partyName               [1]     DirectoryString }

4.2.1.8  Issuer Alternative Names

   As with 4.2.1.7, this extension is used to associate Internet style
   identities with the certificate issuer. Issuer alternative names MUST
   be encoded as in 4.2.1.7.

   Where present, this extension SHOULD NOT be marked critical.

      id-ce-issuerAltName OBJECT IDENTIFIER ::=  { id-ce 18 }

      IssuerAltName ::= GeneralNames

4.2.1.9  Subject Directory Attributes

   The subject directory attributes extension is used to convey
   identification attributes (e.g.,nationality) of the subject.  The
   extension is defined as a sequence of one or more attributes.  This
   extension MUST be non-critical.

   id-ce-subjectDirectoryAttributes OBJECT IDENTIFIER ::=  { id-ce 9 }

   SubjectDirectoryAttributes ::= SEQUENCE SIZE (1..MAX) OF Attribute

4.2.1.10  Basic Constraints

   The basic constraints extension identifies whether the subject of the
   certificate is a CA and how deep a certification path may exist
   through that CA.

   The cA bit indicates if the certified public key may be used to
   verify signatures on other certificates.  If the cA bit is asserted,
   then either the keyCertSign bit or the cRLSign bit in the key usage
   extension (see 4.2.1.3) MUST also be asserted. If the cA bit is not
   asserted, then both the keyCertSign bit and the cRLSign in the key
   usage extension MUST NOT be asserted.

   The pathLenConstraint field is meaningful only if cA is set to TRUE.
   In this case, it gives the maximum number of CA certificates that may
   follow this certificate in a certification path.  (Note: The last
   certificate in the certification path is not included in this limit.
   Usually, the last certificate is an end-entity certificate, but it
   can be a CA certificate.)  A pathLenConstraint of zero indicates that
   only one more certificate may follow in the certification path.
   Where it appears, the pathLenConstraint field MUST be greater than or
   equal to zero.  Where pathLenConstraint does not appear, there is no



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   limit to the allowed length of the certification path.

   This extension MUST appear as a critical extension in all CA
   certificates.  This extension MAY appear as a critical or non-
   critical extension in end entity certificates.

   id-ce-basicConstraints OBJECT IDENTIFIER ::=  { id-ce 19 }

   BasicConstraints ::= SEQUENCE {
        cA                      BOOLEAN DEFAULT FALSE,
        pathLenConstraint       INTEGER (0..MAX) OPTIONAL }

4.2.1.11  Name Constraints

   The name constraints extension, which MUST be used only in a CA
   certificate, indicates a name space within which all subject names in
   subsequent certificates in a certification path MUST be located.
   Restrictions apply to the subject distinguished name and apply to
   subject alternative names.  Restrictions apply only when the
   specified name form is present.  If no name of the type is in the
   certificate, the certificate is acceptable.

   Name constraints are not applied to certificates whose issuer and
   subject are identical.  (This could prevent CAs that use name
   constraints from issuing self-signed certificates to implement key
   rollover.)

   Restrictions are defined in terms of permitted or excluded name
   subtrees.  Any name matching a restriction in the excludedSubtrees
   field is invalid regardless of information appearing in the
   permittedSubtrees.  This extension MUST be critical.

   Within this profile, the minimum and maximum fields are not used with
   any name forms, thus minimum is always zero, and maximum is always
   absent.

   For URIs, the constraint applies to the host part of the name. The
   constraint may specify a host or a domain.  Examples would be
   "foo.bar.com";  and ".xyz.com".  When the the constraint begins with
   a period, it may be expanded with one or more subdomains.  That is,
   the constraint ".xyz.com" is satisfied by both abc.xyz.com and
   abc.def.xyz.com.  However, the constraint ".xyz.com" is not satisfied
   by "xyz.com".  When the constraint does not begin with a period, it
   specifies a host.

   A name constraint for Internet mail addresses may specify a
   particular mailbox, all addresses at a particular host, or all
   mailboxes in a domain.  To indicate a particular mailbox, the



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   constraint is the complete mail address.  For example, "root@xyz.com"
   indicates the root mailbox on the host "xyz.com". To indicate all
   Internet mail addresses on a particular host, the constraint is
   specified as the host name.  For example, the constraint "xyz.com" is
   satisfied by any mail address at the host "xyz.com". To specify any
   address within a domain, the constraint is specified with a leading
   period (as with URIs).  For example, ".xyz.com" indicates all the
   Internet mail addresses in the domain "xyz.com", but not Internet
   mail addresses on the host "xyz.com".

   DNS name restrictions are expressed as foo.bar.com. Any DNS name that
   can be constructed by simply adding to the left hand side of the name
   satisfies the name constraint. For example, www.foo.bar.com would
   satisfy the constraint but foo1.bar.com would not.

   Legacy implementations exist where an RFC 822 name is embedded in the
   subject distinguished name in an attribute of type EmailAddress (see
   sec. 4.1.2.6). When rfc822 names are constrained, but the certificate
   does not include a subject alternative name, the rfc822 name
   constraint MUST be applied to the attribute of type EmailAddress in
   the subject distinguished name.  The ASN.1 syntax for EmailAddress
   and the corresponding OID are supplied in Appendix A and B.

   Restrictions of the form directoryName MUST be applied to the subject
   field in the certificate and to the subjectAltName extensions of type
   directoryName.  Restrictions of the form x400Address MUST be applied
   to subjectAltName extensions of type x400Address.

   When applying restrictions of the form directoryName, an
   implementation MUST compare DN attributes.  At a minimum,
   implementations MUST perform the DN comparison rules specified in
   Section 4.1.2.4.  CAs issuing certificates with a restriction of the
   form directoryName SHOULD NOT rely on implementation of the full ISO
   DN name comparison algorithm.  This implies name restrictions MUST be
   stated identically to the encoding used in the subject field or
   subjectAltName extension.

   The syntax of iPAddress MUST be as described in section 4.2.1.7 with
   the following additions specifically for Name Constraints.  For IPv4
   addresses, the ipAddress field of generalName MUST contain eight (8)
   octets, encoded in the style of RFC 1519 (CIDR) to represent an
   address range.[RFC 1519]  For IPv6 addresses, the ipAddress field
   MUST contain 32 octets similarly encoded.  For example, a name
   constraint for "class C" subnet 10.9.8.0 is represented as the octets
   0A 09 08 00 FF FF FF 00, representing the CIDR notation
   10.9.8.0/255.255.255.0.

   The syntax and semantics for name constraints for otherName,



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   ediPartyName, and registeredID are not defined by this specification.

      id-ce-nameConstraints OBJECT IDENTIFIER ::=  { id-ce 30 }

      NameConstraints ::= SEQUENCE {
           permittedSubtrees       [0]     GeneralSubtrees OPTIONAL,
           excludedSubtrees        [1]     GeneralSubtrees OPTIONAL }

      GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree

      GeneralSubtree ::= SEQUENCE {
           base                    GeneralName,
           minimum         [0]     BaseDistance DEFAULT 0,
           maximum         [1]     BaseDistance OPTIONAL }

      BaseDistance ::= INTEGER (0..MAX)

4.2.1.12  Policy Constraints

   The policy constraints extension can be used in certificates issued
   to CAs. The policy constraints extension constrains path validation
   in two ways. It can be used to prohibit policy mapping or require
   that each certificate in a path contain an acceptable policy
   identifier.

   If the inhibitPolicyMapping field is present, the value indicates the
   number of additional certificates that may appear in the path before
   policy mapping is no longer permitted.  For example, a value of one
   indicates that policy mapping may be processed in certificates issued
   by the subject of this certificate, but not in additional
   certificates in the path.

   If the requireExplicitPolicy field is present, subsequent
   certificates MUST include an acceptable policy identifier.  The value
   of requireExplicitPolicy indicates the number of additional
   certificates that may appear in the path before an explicit policy is
   required.  An acceptable policy identifier is the identifier of a
   policy required by the user of the certification path or the
   identifier of a policy which has been declared equivalent through
   policy mapping.

   Conforming CAs MUST NOT issue certificates where policy constraints
   is a null sequence. That is, at least one of the inhibitPolicyMapping
   field or the requireExplicitPolicy field MUST be present. The
   behavior of clients that encounter a null policy constraints field is
   not addressed in this profile.

   This extension may be critical or non-critical.



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   id-ce-policyConstraints OBJECT IDENTIFIER ::=  { id-ce 36 }

   PolicyConstraints ::= SEQUENCE {
        requireExplicitPolicy           [0] SkipCerts OPTIONAL,
        inhibitPolicyMapping            [1] SkipCerts OPTIONAL }

   SkipCerts ::= INTEGER (0..MAX)

4.2.1.13  Extended key usage field

   This field indicates one or more purposes for which the certified
   public key may be used, in addition to or in place of the basic
   purposes indicated in the key usage extension field.  In general,
   this extension will appear only in end entity certificates.  This
   field is defined as follows:

   id-ce-extKeyUsage OBJECT IDENTIFIER ::= {id-ce 37}

   ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId

   KeyPurposeId ::= OBJECT IDENTIFIER

   Key purposes may be defined by any organization with a need.  Object
   identifiers used to identify key purposes MUST be assigned in
   accordance with IANA or ITU-T Rec. X.660 | ISO/IEC/ITU 9834-1.

   This extension may, at the option of the certificate issuer, be
   either critical or non-critical.

   If the extension is flagged critical, then the certificate MUST only
   be used for one of the purposes indicated.  If multiple purposes are
   indicated the application need not recognize all purposes indicated,
   as long as the intended purpose is present and recognized.

   If the extension is flagged non-critical, then it indicates the
   intended purpose or purposes of the key, and may be used in finding
   the correct key/certificate of an entity that has multiple
   keys/certificates. It is an advisory field and does not imply that
   usage of the key is restricted by the certification authority to the
   purpose indicated. Certificate using applications may nevertheless
   require that a particular purpose be indicated in order for the
   certificate to be acceptable to that application.

   If a certificate contains both a critical key usage field and a
   critical extended key usage field, then both fields MUST be processed
   independently and the certificate MUST only be used for a purpose
   consistent with both fields.  If there is no purpose consistent with
   both fields, then the certificate MUST NOT be used for any purpose.



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   The following key usage purposes are defined by this profile:

   id-kp OBJECT IDENTIFIER ::= { id-pkix 3 }

   id-kp-serverAuth              OBJECT IDENTIFIER   ::=   {id-kp 1}
   -- TLS Web server authentication
   -- Key usage bits that may be consistent: digitalSignature,
   --                         keyEncipherment or keyAgreement
   --
   id-kp-clientAuth              OBJECT IDENTIFIER   ::=   {id-kp 2}
   -- TLS Web client authentication
   -- Key usage bits that may be consistent: digitalSignature and/or
   --                            keyAgreement
   --
   id-kp-codeSigning             OBJECT IDENTIFIER   ::=   {id-kp 3}
   -- Signing of downloadable executable code
   -- Key usage bits that may be consistent: digitalSignature
   --
   id-kp-emailProtection         OBJECT IDENTIFIER   ::=   {id-kp 4}
   -- E-mail protection
   -- Key usage bits that may be consistent: digitalSignature,
   --                         nonRepudiation, and/or (keyEncipherment
   --                         or keyAgreement)
   --
   id-kp-timeStamping    OBJECT IDENTIFIER ::= { id-kp 8 }
   -- Binding the hash of an object to a time from an agreed-upon time
   -- source. Key usage bits that may be consistent: digitalSignature,
   --                         nonRepudiation

4.2.1.14  CRL Distribution Points

   The CRL distribution points extension identifies how CRL information
   is obtained.  The extension SHOULD be non-critical, but this profile
   RECOMMENDS support for this extension by CAs and applications.
   Further discussion of CRL management is contained in section 5.

   The cRLDistributionPoints extension is a SEQUENCE of
   DistributionPoint.  A DistributionPoint consists of three fields,
   each of which is optional: the name of the DistributionPoint,
   ReasonsFlags, and the cRLIssuer.  While each component is optional, a
   DistributionPoint MUST NOT consist of only the ReasonsFlags field.
   If the distributionPoint omits cRLIssuer, the CRL MUST be issued by
   the CA that issued the certificate.  If the distributionPointName is
   absent, cRLIssuer MUST be present and include a Name corresponding to
   an X.500 or LDAP directory entry where the CRL is located.

   If the cRLDistributionPoints extension contains a
   DistributionPointName of type URI, the following semantics MUST be



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   assumed: the URI is a pointer to the current CRL for the associated
   reasons and will be issued by the associated cRLIssuer.  The expected
   values for the URI are those defined in 4.2.1.7. Processing rules for
   other values are not defined by this specification.  If the
   distributionPoint omits reasons, the CRL MUST include revocations for
   all reasons.

   id-ce-cRLDistributionPoints OBJECT IDENTIFIER ::=  { id-ce 31 }

   CRLDistributionPoints ::= SEQUENCE SIZE (1..MAX) OF DistributionPoint

   DistributionPoint ::= SEQUENCE {
        distributionPoint       [0]     DistributionPointName OPTIONAL,
        reasons                 [1]     ReasonFlags OPTIONAL,
        cRLIssuer               [2]     GeneralNames OPTIONAL }

   DistributionPointName ::= CHOICE {
        fullName                [0]     GeneralNames,
        nameRelativeToCRLIssuer [1]     RelativeDistinguishedName }

   ReasonFlags ::= BIT STRING {
        unused                  (0),
        keyCompromise           (1),
        cACompromise            (2),
        affiliationChanged      (3),
        superseded              (4),
        cessationOfOperation    (5),
        certificateHold         (6) }

4.2.1.15 Inhibit Any-Policy

   The inhibit any-policy extension can be used in certificates issued
   to CAs. The inhibit any-policy indicates that the special any-policy
   OID, with the value {2 5 29 32 0}, is not considered an explicit
   match for other certificate policies.  The value indicates the number
   of additional certificates that may appear in the path before any-
   policy is no longer permitted.  For example, a value of one indicates
   that any-policy may be processed in certificates issued by the
   subject of this certificate, but not in additional certificates in
   the path.

   This extension MUST be critical.

   id-ce-inhibitAnyPolicy OBJECT IDENTIFIER ::=  { id-ce 54 }

   InhibitAnyPolicy ::= SkipCerts

   SkipCerts ::= INTEGER (0..MAX)



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4.2.1.16 Freshest CRL (a.k.a. Delta CRL Distribution Point)

   The freshest CRL extension identifies how delta-CRL information is
   obtained.  The extension MUST be non-critical.  Further discussion of
   CRL management is contained in section 5.

   The same syntax is used for this extension and the
   cRLDistributionPoints extension, and is described in section
   4.2.1.14.  The same conventions apply to both extensions.

   id-ce-freshestCRL OBJECT IDENTIFIER ::=  { id-ce 46 }

   FreshestCRL ::= CRLDistributionPoints

4.2.2  Private Internet Extensions

   This section defines one new extension for use in the Internet Public
   Key Infrastructure.  This extension may be used to direct
   applications to identify an on-line validation service supporting the
   issuing CA.  As the information may be available in multiple forms,
   each extension is a sequence of IA5String values, each of which
   represents a URI.  The URI implicitly specifies the location and
   format of the information and the method for obtaining the
   information.

   An object identifier is defined for the private extension.  The
   object identifier associated with the private extension is defined
   under the arc id-pe within the id-pkix name space.  Any future
   extensions defined for the Internet PKI will also be defined under
   the arc id-pe.

      id-pkix  OBJECT IDENTIFIER  ::=
               { iso(1) identified-organization(3) dod(6) internet(1)
                       security(5) mechanisms(5) pkix(7) }

      id-pe  OBJECT IDENTIFIER  ::=  { id-pkix 1 }

4.2.2.1  Authority Information Access

   The authority information access extension indicates how to access CA
   information and services for the issuer of the certificate in which
   the extension appears. Information and services may include on-line
   validation services and CA policy data.  (The location of CRLs is not
   specified in this extension; that information is provided by the
   cRLDistributionPoints extension.)  This extension may be included in
   subject or CA certificates, and it MUST be non-critical.

   id-pe-authorityInfoAccess OBJECT IDENTIFIER ::= { id-pe 1 }



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   AuthorityInfoAccessSyntax  ::=
           SEQUENCE SIZE (1..MAX) OF AccessDescription

   AccessDescription  ::=  SEQUENCE {
           accessMethod          OBJECT IDENTIFIER,
           accessLocation        GeneralName  }

   id-ad OBJECT IDENTIFIER ::= { id-pkix 48 }

   id-ad-caIssuers OBJECT IDENTIFIER ::= { id-ad 2 }

   Each entry in the sequence AuthorityInfoAccessSyntax describes the
   format and location of additional information provided by the CA who
   issued the certificate in which this extension appears.  The type and
   format of the information is specified by the accessMethod field; the
   accessLocation field specifies the location of the information.  The
   retrieval mechanism may be implied by the accessMethod or specified
   by accessLocation.

   This profile defines one OID for accessMethod. The id-ad-caIssuers
   OID is used when the additional information lists CAs that have
   issued certificates superior to the CA that issued the certificate
   containing this extension.  The referenced CA Issuers description is
   intended to aid certificate users in the selection of a certification
   path that terminates at a point trusted by the certificate user.

   When id-ad-caIssuers appears as accessInfoType, the accessLocation
   field describes the referenced description server and the access
   protocol to obtain the referenced description.  The accessLocation
   field is defined as a GeneralName, which can take several forms.
   Where the information is available via http, ftp, or ldap,
   accessLocation MUST be a uniformResourceIdentifier.  Where the
   information is available via the directory access protocol (dap),
   accessLocation MUST be a directoryName. When the information is
   available via electronic mail, accessLocation MUST be an rfc822Name.
   The semantics of other name forms of accessLocation (when
   accessMethod is id-ad-caIssuers) are not defined by this
   specification.

   [RFC 2560] defines the access descriptor for the Online Certificate
   Status Protocol.  When this access descriptor appears in the
   authority information access extension, this indicates the issuer
   provides revocation information for this certificate through the
   named OCSP service.  Additional access descriptors may be defined in
   other PKIX specifications.






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4.2.2.2 Subject Information Access

   The subject information access extension indicates how to access
   information and services for the subject of the certificate in which
   the extension appears. When the subject is a CA, information and
   services may include certificate validation services and CA policy
   data.  When the subject is an end entity, the information describes
   the type of services offered and how to access them.  In this case,
   the contents of this extension are defined in the protocol
   specifications for the suported services.  This extension may be
   included in subject or CA certificates, and it MUST be non-critical.

   id-pe-subjectInfoAccess OBJECT IDENTIFIER ::= { id-pe 11 }

   SubjectInfoAccessSyntax  ::=
           SEQUENCE SIZE (1..MAX) OF AccessDescription

   AccessDescription  ::=  SEQUENCE {
           accessMethod          OBJECT IDENTIFIER,
           accessLocation        GeneralName  }

   Each entry in the sequence SubjectInfoAccessSyntax describes the
   format and location of additional information provided by the subject
   of the certificate in which this extension appears.  The type and
   format of the information is specified by the accessMethod field; the
   accessLocation field specifies the location of the information.  The
   retrieval mechanism may be implied by the accessMethod or specified
   by accessLocation.

   This profile defines one access method to be used when the subject is
   a CA, and one access method to be used when the subject is an end
   entity.  Additional access methods may be defined in the future in
   the protocol specifications for other services.

   The id-ad-caRepository OID is used when the subject is a CA, and
   publishes its certificates and CRLs (if issued) in a repository.  The
   accessLocation field is defined as a GeneralName, which can take
   several forms.  Where the information is available via http, ftp, or
   ldap, accessLocation MUST be a uniformResourceIdentifier.  Where the
   information is available via the directory access protocol (dap),
   accessLocation MUST be a directoryName. When the information is
   available via electronic mail, accessLocation MUST be an rfc822Name.
   The semantics of other name forms of of accessLocation (when
   accessMethod is id-ad-caRepository) are not defined by this
   specification.

   The id-ad-timeStamping OID is used when the subject offers
   timestamping services using the Time Stamp Protocol defined in [PKIX



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   TSA].  Where the timestamping services are available via http or ftp,
   accessLocation MUST be a uniformResourceIdentifier.  Where the
   timestamping services are available via electronic mail,
   accessLocation MUST be an rfc822Name.  Where timestamping services
   are available using TCP/IP, the dNSName and ipAddress name forms may
   be used.  The semantics of other name forms of accessLocation (when
   accessMethod is id-ad-timeStamping) are not defined by this
   specification.

   Additional access descriptors may be defined in other PKIX
   specifications.

   id-ad OBJECT IDENTIFIER ::= { id-pkix 48 }

   id-ad-caRepository OBJECT IDENTIFIER ::= { id-ad 5 }

   id-ad-timeStamping OBJECT IDENTIFIER ::= { id-ad 3 }

5  CRL and CRL Extensions Profile

   As described above, one goal of this X.509 v2 CRL profile is to
   foster the creation of an interoperable and reusable Internet PKI.
   To achieve this goal, guidelines for the use of extensions are
   specified, and some assumptions are made about the nature of
   information included in the CRL.

   CRLs may be used in a 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.  The profile defines a baseline set
   of information that can be expected in every CRL.  Also, the profile
   defines common locations within the CRL for frequently used
   attributes as well as common representations for these attributes.

   This profile does not define any private Internet CRL extensions or
   CRL entry extensions.

   Environments with additional or special purpose requirements may
   build on this profile or may replace it.

   Conforming CAs are not required to issue CRLs if other revocation or
   certificate status mechanisms are provided.  Conforming CAs that
   issue CRLs MUST issue version 2 CRLs, and CAs MUST include the date
   by which the next CRL will be issued in the nextUpdate field (see
   sec. 5.1.2.5), the CRL number extension (see sec. 5.2.3) and the
   authority key identifier extension (see sec. 5.2.1).  Conforming
   applications are required to process version 1 and 2 CRLs.



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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.

   CertificateList  ::=  SEQUENCE  {
        tbsCertList          TBSCertList,
        signatureAlgorithm   AlgorithmIdentifier,
        signatureValue       BIT STRING  }

   TBSCertList  ::=  SEQUENCE  {
        version                 Version OPTIONAL,
                                     -- if present, MUST be v2
        signature               AlgorithmIdentifier,
        issuer                  Name,
        thisUpdate              Time,
        nextUpdate              Time OPTIONAL,
        revokedCertificates     SEQUENCE OF SEQUENCE  {
             userCertificate         CertificateSerialNumber,
             revocationDate          Time,
             crlEntryExtensions      Extensions OPTIONAL
                                           -- if present, MUST be v2
                                  }  OPTIONAL,
        crlExtensions           [0]  EXPLICIT Extensions OPTIONAL
                                           -- if present, MUST be v2
                                  }

   -- Version, Time, CertificateSerialNumber, and Extensions
   -- are all defined in the ASN.1 in section 4.1

   -- AlgorithmIdentifier is defined in section 4.1.1.2

   The following items describe the use of the X.509 v2 CRL in the
   Internet PKI.

5.1.1  CertificateList Fields

   The CertificateList is a SEQUENCE of three required fields. The
   fields are described in detail in the following subsections.

5.1.1.1  tbsCertList

   The first field in the sequence is the tbsCertList.  This field is
   itself a sequence containing the name of the issuer, issue date,
   issue date of the next list, the optional list of revoked
   certificates, and optional CRL extensions.  When there are no revoked
   certificates, the revoked certificates list is absent.  When one or



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   more certificates are revoked, each entry on the revoked certificate
   list is defined by a sequence of user certificate serial number,
   revocation date, and optional CRL entry extensions.

5.1.1.2  signatureAlgorithm

   The signatureAlgorithm field contains the algorithm identifier for
   the algorithm used by the CA to sign the CertificateList.  The field
   is of type AlgorithmIdentifier, which is defined in section 4.1.1.2.
   [PKIX ALGS] lists the supported algorithms for this specification.
   Conforming CAs MUST use the algorithm identifiers presented in [PKIX
   ALGS] when signing with a supported signature algorithm.

   This field MUST contain the same algorithm identifier as the
   signature field in the sequence tbsCertList (see sec. 5.1.2.2).

5.1.1.3  signatureValue

   The signatureValue field contains a digital signature computed upon
   the ASN.1 DER encoded tbsCertList.  The ASN.1 DER encoded tbsCertList
   is used as the input to the signature function.  This signature value
   is then ASN.1 encoded as a BIT STRING and included in the CRL's
   signatureValue field.  The details of this process are specified for
   each of the supported algorithms in [PKIX ALGS].

   CAs MAY use one private key to digitally sign certificates and CRLs,
   or CAs MAY use separate private keys to digitally sign certificates
   and CRLs.  When separate private keys are employed, each of the
   public keys associated with these private keys is placed in a
   separate certificate, one with the keyCertSign bit set in the key
   usage extension, and one with the cRLSign bit set in the key usage
   extension (see sec. 4.2.1.3).  When separate private keys are
   employed, certificates issued by the CA contain one authority key
   identifier, and the corresponding CRLs contain a different authority
   key identifier.  The use of separate CA certificates for validation
   of certificate signatures and CRL signatures can offer improved
   security characteristics; however, it imposes a burden on
   applications, and it might limit interoperability.  Many applications
   construct a certification path, and then validate the certification
   path (see sec. 6).  CRL checking in turn requires a separate
   certification path to be constructed and validated for the CA's CRL
   signature validation certificate.  Applications that perform CRL
   checking MUST support certification path validation when certificates
   and CRLs are digitally signed with the same CA private key.  These
   applications SHOULD support certification path validation when
   certificates and CRLs are digitally signed with different CA private
   keys.




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5.1.2  Certificate List "To Be Signed"

   The certificate list to be signed, or TBSCertList, is a SEQUENCE of
   required and optional fields.  The required fields identify the CRL
   issuer, the algorithm used to sign the CRL, the date and time the CRL
   was issued, and the date and time by which the CA will issue the next
   CRL.

   Optional fields include lists of revoked certificates and CRL
   extensions.  The revoked certificate list is optional to support the
   case where a CA has not revoked any unexpired certificates that it
   has issued.  The profile requires conforming CAs to use the CRL
   extension cRLNumber in all CRLs issued.

5.1.2.1  Version

   This optional field describes the version of the encoded CRL.  When
   extensions are used, as required by this profile, this field MUST be
   present and MUST specify version 2 (the integer value is 1).

5.1.2.2  Signature

   This field contains the algorithm identifier for the algorithm used
   to sign the CRL.  [PKIX ALGS] lists OIDs for the most popular
   signature algorithms used in the Internet PKI.

   This field MUST contain the same algorithm identifier as the
   signatureAlgorithm field in the sequence CertificateList (see section
   5.1.1.2).

5.1.2.3  Issuer Name

   The issuer name identifies the entity who has signed and issued the
   CRL.  The issuer identity is carried in the issuer name field.
   Alternative name forms may also appear in the issuerAltName extension
   (see sec. 5.2.2).  The issuer name field MUST contain an X.500
   distinguished name (DN).  The issuer name field is defined as the
   X.501 type Name, and MUST follow the encoding rules for the issuer
   name field in the certificate (see sec. 4.1.2.4).

5.1.2.4  This Update

   This field indicates the issue date of this CRL. ThisUpdate may be
   encoded as UTCTime or GeneralizedTime.

   CAs conforming to this profile that issue CRLs MUST encode thisUpdate
   as UTCTime for dates through the year 2049.  CAs conforming to this
   profile that issue CRLs MUST encode thisUpdate as GeneralizedTime for



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   dates in the year 2050 or later.

   Where encoded as UTCTime, thisUpdate MUST be specified and
   interpreted as defined in section 4.1.2.5.1.  Where encoded as
   GeneralizedTime, thisUpdate MUST be specified and interpreted as
   defined in section 4.1.2.5.2.

5.1.2.5  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.  CAs SHOULD issue
   CRLs with a nextUpdate time equal to or later than all previous CRLs.
   nextUpdate may be encoded as UTCTime or GeneralizedTime.

   This profile requires inclusion of nextUpdate in all CRLs issued by
   conforming CAs. Note that the ASN.1 syntax of TBSCertList describes
   this field as OPTIONAL, which is consistent with the ASN.1 structure
   defined in [X.509]. The behavior of clients processing CRLs which
   omit nextUpdate is not specified by this profile.

   CAs conforming to this profile that issue CRLs MUST encode nextUpdate
   as UTCTime for dates through the year 2049.  CAs conforming to this
   profile that issue CRLs MUST encode nextUpdate as GeneralizedTime for
   dates in the year 2050 or later.

   Where encoded as UTCTime, nextUpdate MUST be specified and
   interpreted as defined in section 4.1.2.5.1.  Where encoded as
   GeneralizedTime, nextUpdate MUST be specified and interpreted as
   defined in section 4.1.2.5.2.

5.1.2.6  Revoked Certificates

   When there are no revoked certificates, the revoked certificates list
   is absent.  Otherwise, revoked certificates are listed by their
   serial numbers.  Certificates revoked by the CA are uniquely
   identified by the certificate serial number.  The date on which the
   revocation occurred is specified.  The time for revocationDate MUST
   be expressed as described in section 5.1.2.4. Additional information
   may be supplied in CRL entry extensions; CRL entry extensions are
   discussed in section 5.3.

5.1.2.7  Extensions

   This field may only appear if the version is 2 (see sec. 5.1.2.1).
   If present, this field is a SEQUENCE of one or more CRL extensions.
   CRL extensions are discussed in section 5.2.




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5.2  CRL Extensions

   The extensions defined by ANSI X9 and ISO/IEC/ITU for X.509 v2 CRLs
   [X.509] [X9.55] 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 in a CRL may be designated as critical or non-
   critical.  A CRL validation MUST fail if it encounters a critical
   extension which it does not know how to process.  However, an
   unrecognized non-critical extension may be ignored.  The following
   subsections present those extensions used within Internet CRLs.
   Communities may elect to include extensions in CRLs which are not
   defined in this specification. However, caution should be exercised
   in adopting any critical extensions in CRLs which might be used in a
   general context.

   Conforming CAs that issue CRLs are required to include the authority
   key identifier (see sec. 5.2.1) and the CRL number (see sec. 5.2.3)
   extensions in all CRLs issued.

5.2.1  Authority Key Identifier

   The authority key identifier extension provides a means of
   identifying the public key corresponding to the private key used to
   sign a CRL.  The identification can be based on either the key
   identifier (the subject key identifier in the CRL signer's
   certificate) or on the issuer name and serial number. This extension
   is especially useful where an issuer has more than one signing key,
   either due to multiple concurrent key pairs or due to changeover.

   Conforming CAs MUST use the key identifier method, and MUST include
   this extension in all CRLs issued.

   The syntax for this CRL extension is defined in section 4.2.1.1.

5.2.2  Issuer Alternative Name

   The issuer alternative names extension allows additional identities
   to be associated with the 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 issuer
   alternative name extension MUST be used.

   The issuerAltName extension SHOULD NOT be marked critical.

   The OID and syntax for this CRL extension are defined in section
   4.2.1.8.



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5.2.3  CRL Number

   The CRL number is a non-critical CRL extension which conveys a
   monotonically increasing sequence number for each CRL issued by a CA.
   This extension allows users to easily determine when a particular CRL
   supersedes another CRL.  CAs conforming to this profile MUST include
   this extension in all CRLs.

   id-ce-cRLNumber OBJECT IDENTIFIER ::= { id-ce 20 }

   cRLNumber ::= INTEGER (0..MAX)

5.2.4  Delta CRL Indicator

   The delta CRL indicator is a critical CRL extension that identifies a
   CRL as being a delta CRL.  Delta CRLs contain updates to revocation
   information previously distributed, rather than all the information
   that would appear in a complete CRL.  The use of delta CRLs can
   significantly reduce network load and processing time in some
   environments.  Delta CRLs are generally smaller than the CRLs they
   update, so applications that obtain delta CRLs consume less network
   bandwidth than applications that obtain the corresponding complete
   CRLs.  Applications which store revocation information in a format
   other than the CRL structure can add new revocation information to
   the local database without reprocessing information.

   The delta CRL indicator extension contains a single value of type
   BaseCRLNumber.  This value identifies the CRL number of the base CRL
   that was used as the foundation in the generation of this delta CRL.
   The referenced base CRL is a CRL that was explicitly issued as a CRL
   that is complete for a given scope (e.g., a set of revocation reasons
   or a particular distribution point.) The CRL containing the delta CRL
   indicator extension contains all updates to the certificate
   revocation status for that same scope.  The combination of a CRL
   containing the delta CRL indicator extension plus the CRL referenced
   in the BaseCRLNumber component of this extension is equivalent to a
   full CRL, for the applicable scope, at the time of publication of the
   delta CRL.

   When a conforming CA issues a delta CRL, the CA MUST also issue a CRL
   that is complete for the given scope.  Both the delta CRL and the
   complete CRL MUST include the CRL number extension (see sec. 5.2.3).
   The CRL number extension in the delta CRL and the complete CRL MUST
   contain the same value.  When a delta CRL is issued, it MUST cover
   the same set of reasons and same set of certificates that were
   covered by the base CRL it references.

   An application can construct a CRL that is complete for a given



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   scope, at the current time, in either of the following ways:

      (a) by retrieving the current delta CRL for that scope, and
      combining it with an issued CRL that is complete for that scope
      and that has a cRLNumber greater than or equal to the cRLNumber of
      the base CRL referenced in the delta CRL; or

      (b) by retrieving the current delta CRL for that scope and
      combining it with a locally constructed CRL whose cRLNumber is
      greater than or equal to the cRLNumber of the base CRL referenced
      in the current delta CRL.

   The constructed CRL has the CRL number specified in the CRL number
   extension found in the delta CRL used in its construction.

   CAs must ensure that application of a delta CRL to the referenced
   base revocation information accurately reflects the current status of
   revocation.  If a CA supports the certificateHold revocation reason
   the following rules must be applied when generating delta CRLs:

      (a) If a certificate was listed as revoked with revocation reason
      certificateHold on a CRL (either a delta CRL or a CRL that is
      complete for a given scope), whose cRLNumber is n, and the hold is
      subsequently released, the certificate must be included in all
      delta CRLs issued after the hold is released where the cRLNumber
      of the referenced base CRL is less than or equal to n. The
      certificate must be listed with revocation reason removeFromCRL
      unless the certificate is subsequently revoked again for one of
      the revocation reasons covered by the delta CRL, in which case the
      certificate must be listed with the revocation reason appropriate
      for the subsequent revocation.

      (b) If the certificate was not removed from hold, but was
      permanently revoked, then it must be listed on all subsequent
      delta CRLs where the cRLNumber of the referenced base CRL is less
      than the cRLNumber of the CRL (either a delta CRL or a CRL that is
      complete for the given scope) on which the permanent revocation
      notice first appeared.

   id-ce-deltaCRLIndicator OBJECT IDENTIFIER ::= { id-ce 27 }

   BaseCRLNumber ::= CRLNumber

5.2.5  Issuing Distribution Point

   The issuing distribution point is a critical CRL extension that
   identifies the CRL distribution point for a particular CRL, and it
   indicates whether the CRL covers revocation for end entity



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   certificates only, CA  certificates only, or a limited set of reason
   codes.  Although the extension is critical, conforming
   implementations are not required to support this extension.

   The CRL is signed using the CA's private key.  CRL Distribution
   Points do not have their own key pairs.  If the CRL is stored in the
   X.500 Directory, it is stored in the Directory entry corresponding to
   the CRL distribution point, which may be different than the Directory
   entry of the CA.

   The reason codes associated with a distribution point MUST be
   specified in onlySomeReasons.  If onlySomeReasons does not appear,
   the distribution point shall contain revocations for all reason
   codes.  CAs MAY use CRL distribution points to partition the CRL on
   the basis of compromise and routine revocation.  In this case, the
   revocations with reason code keyCompromise (1) and cACompromise (2)
   appear in one distribution point, and the revocations with other
   reason codes appear in another distribution point.

   Where the issuingDistributionPoint extension contains a URL, the
   following semantics MUST be assumed: the object is a pointer to the
   most current CRL issued by this CA.  The URI schemes ftp, http,
   mailto [RFC1738] and ldap [RFC1778] are defined for this purpose.
   The URI MUST be an absolute, not relative, pathname and MUST specify
   the host.

   id-ce-issuingDistributionPoint OBJECT IDENTIFIER ::= { id-ce 28 }

   issuingDistributionPoint ::= SEQUENCE {
        distributionPoint       [0] DistributionPointName OPTIONAL,
        onlyContainsUserCerts   [1] BOOLEAN DEFAULT FALSE,
        onlyContainsCACerts     [2] BOOLEAN DEFAULT FALSE,
        onlySomeReasons         [3] ReasonFlags OPTIONAL,
        indirectCRL             [4] BOOLEAN DEFAULT FALSE }

5.2.6 Freshest CRL (a.k.a. Delta CRL Distribution Point)

   The freshest CRL extension identifies how delta-CRL information for
   this CRL is obtained.  The extension MUST be non-critical.

   The same syntax is used for this extension as the
   cRLDistributionPoints certificate extension, and is described in
   section 4.2.1.14.  The same conventions apply to both extensions.

   id-ce-freshestCRL OBJECT IDENTIFIER ::=  { id-ce 46 }

   FreshestCRL ::= CRLDistributionPoints




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5.3  CRL Entry Extensions

   The CRL entry extensions already defined by ANSI X9 and ISO/IEC/ITU
   for X.509 v2 CRLs provide methods for associating additional
   attributes with CRL entries [X.509] [X9.55].  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.  A CRL
   validation MUST fail if it encounters a critical CRL entry extension
   which it does not know how to process.  However, an unrecognized non-
   critical CRL entry extension may be ignored.  The following
   subsections present recommended extensions used within Internet CRL
   entries and 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 general context.

   All CRL entry extensions used in this specification are non-critical.
   Support for these extensions is optional for conforming CAs and
   applications.  However, CAs that issue CRLs SHOULD include reason
   codes (see sec. 5.3.1) and invalidity dates (see sec. 5.3.3) whenever
   this information is available.

5.3.1  Reason Code

   The reasonCode is a non-critical CRL entry extension that identifies
   the reason for the certificate revocation.  CAs are strongly
   encouraged to include meaningful reason codes in CRL entries;
   however, the reason code CRL entry extension SHOULD be absent instead
   of using the unspecified (0) reasonCode value.

   id-ce-cRLReason OBJECT IDENTIFIER ::= { id-ce 21 }

   -- reasonCode ::= { CRLReason }

   CRLReason ::= ENUMERATED {
        unspecified             (0),
        keyCompromise           (1),
        cACompromise            (2),
        affiliationChanged      (3),
        superseded              (4),
        cessationOfOperation    (5),
        certificateHold         (6),
        removeFromCRL           (8) }







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5.3.2  Hold Instruction Code

   The hold instruction code is a non-critical CRL entry extension that
   provides a registered instruction identifier which indicates the
   action to be taken after encountering a certificate that has been
   placed on hold.

   id-ce-holdInstructionCode OBJECT IDENTIFIER ::= { id-ce 23 }

   holdInstructionCode ::= OBJECT IDENTIFIER

   The following instruction codes have been defined.  Conforming
   applications that process this extension MUST recognize the following
   instruction codes.

   holdInstruction    OBJECT IDENTIFIER ::=
                    { iso(1) member-body(2) us(840) x9-57(10040) 2 }

   id-holdinstruction-none   OBJECT IDENTIFIER ::= {holdInstruction 1}
   id-holdinstruction-callissuer
                             OBJECT IDENTIFIER ::= {holdInstruction 2}
   id-holdinstruction-reject OBJECT IDENTIFIER ::= {holdInstruction 3}

   Conforming applications which encounter an id-holdinstruction-
   callissuer MUST call the certificate issuer or reject the
   certificate.  Conforming applications which encounter an id-
   holdinstruction-reject MUST reject the certificate. The hold
   instruction id-holdinstruction-none is semantically equivalent to the
   absence of a holdInstructionCode, and its use is strongly deprecated
   for the Internet PKI.

5.3.3  Invalidity Date

   The invalidity date is a non-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 the CRL entry,
   which is the date at which the CA processed the revocation. When a
   revocation is first posted by a CA in a CRL, the invalidity date may
   precede the date of issue of earlier CRLs, but the revocation date
   SHOULD NOT precede the date of issue of earlier CRLs.  Whenever this
   information is available, CAs are strongly encouraged to share it
   with CRL users.

   The GeneralizedTime values included in this field MUST be expressed
   in Greenwich Mean Time (Zulu), and MUST be specified and interpreted
   as defined in section 4.1.2.5.2.




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   id-ce-invalidityDate OBJECT IDENTIFIER ::= { id-ce 24 }

   invalidityDate ::=  GeneralizedTime

5.3.4  Certificate Issuer

   This CRL entry extension identifies the certificate issuer associated
   with an entry in an indirect CRL, i.e. a CRL that has the indirectCRL
   indicator set in its issuing distribution point extension. If this
   extension is not present on the first entry in an indirect CRL, the
   certificate issuer defaults to the CRL issuer. On subsequent entries
   in an indirect CRL, if this extension is not present, the certificate
   issuer for the entry is the same as that for the preceding entry.
   This field is defined as follows:

   id-ce-certificateIssuer   OBJECT IDENTIFIER ::= { id-ce 29 }

   certificateIssuer ::=     GeneralNames

   If used by conforming CAs that issue CRLs, this extension MUST always
   be critical.  If an implementation ignored this extension it could
   not correctly attribute CRL entries to certificates.  This
   specification RECOMMENDS that implementations recognize this
   extension.

6  Certification Path Validation

   Certification path validation procedures for the Internet PKI are
   based on the algorithm supplied in [X.509].  Certification path
   processing verifies the binding between the subject distinguished
   name and/or subject alternative name and subject public key.  The
   binding is limited by constraints which are specified in the
   certificates which comprise the path and inputs which are specified
   by the relying party. The basic constraints and policy constraints
   extensions allow the certification path processing logic to automate
   the decision making process.

   This section describes an algorithm for validating certification
   paths.  Conforming implementations of this specification are not
   required to implement this algorithm, but MUST provide functionality
   equivalent to the external behavior resulting from this procedure.
   Any algorithm may be used by a particular implementation so long as
   it derives the correct result.

   In section 6.1, the text describes basic path validation.  Valid
   paths begin with certificates issued by a "most-trusted CA".  The
   algorithm requires the public key of the CA, the CA's name, and any
   constraints upon the set of paths which may be validated using this



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   key.

   The selection of a "most-trusted CA" is a matter of policy: it could
   be the top CA in a hierarchical PKI; the CA that issued the
   verifier's own certificate(s); or any other CA in a network PKI.  The
   path validation procedure is the same regardless of the choice of
   "most-trusted CA."  In addition, different applications may rely on
   different "most-trusted CA", or may accept paths that begin with any
   of a set of "most-trusted CAs."

   Section 6.2 describes methods for using the path validation algorithm
   in specific implementations.  Two specific cases are discussed: the
   case where paths may begin with one of several trusted CAs; and where
   compatibility with the PEM architecture is required.

   Section 6.3 describes the steps necessary to determine if a
   certificate is revoked or on hold status when CRLs are the revocation
   mechanism used by the certificate issuer.

   6.1 Basic Path Validation

   This text describes an algorithm for X.509 path processing.  A
   conformant implementation MUST include an X.509 path processing
   procedure that is functionally equivalent to the external behavior of
   this algorithm.  However, some of the certificate fields processed in
   this algorithm are optional for compliant implementations. Clients
   that do not support these fields may omit the corresponding steps in
   the path validation algorithm.

   For example, clients are not required to support the policy mapping
   extension.  Clients that do not support this extension may omit the
   path validation steps where policy mappings are processed.  Note that
   clients MUST reject the certificate if it contains critical
   extensions that are not supported.

   This text describes the trust anchor as an input to the algorithm.
   There is no requirement that the same trust anchor be used to
   validate all certification paths.  Different trust anchors may be
   used to validate different paths, as discussed further in Section
   6.2.

   The primary goal of path validation is to verify the binding between
   a subject distinguished name or subject alternative name and subject
   public key, as represented in the end entity certificate, based on
   the public key of the trust anchor.  This requires obtaining a
   sequence of certificates that support that binding.  The procedure
   performed to obtain this sequence of certificates is outside the
   scope of this section.



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   To meet this goal, the path validation process verifies, among other
   things, that a prospective certification path (a sequence of n
   certificates) satisfies the following conditions:

      (a) for all x in {1, ..., n-1}, the subject of certificate x is
      the issuer of certificate x+1;

      (b) certificate 1 is issued by the trust anchor;

      (c) certificate n is the end entity certificate; and

      (d) for all x in {1, ..., n}, the certificate was valid at the
      time in question.

   A particular certification path may not, however, be appropriate for
   all applications.  The path validation process also determines the
   set of certificate policies that are valid for this path, based on
   the certificate policies extension, policy mapping extension, policy
   constraints extension, and inhibit any-policy extension. To achieve
   this, the path validation algorithm constructs a valid policy tree.
   If the set of certificate policies that are valid for this path is
   not empty, then the result will be a valid policy tree of depth n,
   otherwise the result will be a NULL valid policy tree.

   A certificate is termed self-issued if the DNs that appear in the
   subject and issuer fields are identical and are not empty.  In
   general, the issuer and subject of the certificates that make up a
   path are different for each certificate.  However, a CA may issue a
   certificate to itself to support key rollover or changes in
   certificate policies.  These self-issued certificates are not counted
   when evaluating path length or name constraints.

   This section presents the algorithm in four basic steps: (1)
   initialization, (2) basic certificate processing, (3) preparation for
   the next certificate, and (4) wrap-up.  Steps (1) and (4) are
   performed exactly once.  Step (2) is performed for all certificates
   in the path.  Step (3) is performed for all certificates in the path
   except the final certificate.  Figure 2 provides a high-level
   flowchart of this algorithm.












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                         +-------+
                         | START |
                         +-------+
                             |
                             V
                     +----------------+
                     | Initialization |
                     +----------------+
                             |
                             +<--------------------+
                             |                     |
                             V                     |
                     +----------------+            |
                     |  Process Cert  |            |
                     +----------------+            |
                             |                     |
                             V                     |
                     +================+            |
                     |  IF Last Cert  |            |
                     |    in Path     |            |
                     +================+            |
                       |            |              |
                  THEN |            | ELSE         |
                       V            V              |
            +----------------+ +----------------+  |
            |    Wrap up     | |  Prepare for   |  |
            +----------------+ |   Next Cert    |  |
                    |          +----------------+  |
                    V               |              |
                +-------+           +--------------+
                | STOP  |
                +-------+

            Figure 2.  Path Processing Flowchart

   6.1.1 Inputs

   This algorithm assumes the following seven inputs are provided to the
   path processing logic:

      (a) a prospective certification path of length n;

      (b) the time, T, for which the validity of the path should be
      determined.  This may be the current date/time, or some point in
      the past.

      (c) user-initial-policy-set:  A set of certificate policy
      identifiers naming the policies that are acceptable to the



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      certificate user. The user-initial-policy-set contains the special
      value any-policy if the user is not concerned about certificate
      policy.

      (d) trust anchor information, describing a CA that serves as a
      trust anchor for the certification path.  The trust anchor
      information includes:

         (1) the trusted issuer name,

         (2) the trusted public key algorithm,

         (3) the trusted public key, and

         (4) optionally, the trusted public key parameters associated
         with the public key.

      The trust anchor information may be provided to the path
      processing procedure in the form of a self-signed certificate.
      The trusted anchor information is trusted because it was delivered
      to the path processing procedure by some trustworthy out-of-band
      procedure.  If the trusted public key algorithm requires
      parameters, then the parameters are provided along with the
      trusted public key.

      (e) initial-policy-mapping-inhibit, which indicates if policy
      mapping is allowed in the certification path.

      (f) initial-explicit-policy, which indicates if the path must be
      valid for at least one of the certificate policies in the user-
      initial-policy-set.

      (g) initial-any-policy-inhibit, which indicates whether the any-
      policy OID should be processed if it is included in a certificate.

   6.1.2 Initialization

   The initialization phase establishes eleven state variables based
   upon the seven inputs:

      (a) valid_policy_tree:  A tree of certificate policies with their
      optional qualifiers; each of the leaves of the tree represents a
      valid policy at this stage in the certification path validation.
      If valid policies exist at this stage in the certification path
      validation, the depth of the tree is equal to the number of
      certificates in the chain that have been processed. If valid
      policies do not exist at this stage in the certification path
      validation, the tree is set to NULL. Once the tree is set to NULL,



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      policy processing ceases.

      Each node in the valid_policy_tree includes four data objects: the
      valid policy, a set of associated policy qualifiers, a set of one
      or more expected policy values, and a criticality indicator.  If
      the node is at depth x, the components of the node have the
      following semantics:

         (1) The valid_policy is a single policy OID representing a
         valid policy for the path of length x.

         (2) The qualifier_set is a set of policy qualifiers associated
         with the valid policy in certificate x.

         (3) The criticality_indicator indicates whether the certificate
         policy extension in certificate x was marked as critical.

         (4) The expected_policy_set contains one or more policy OIDs
         that would satisfy this policy in the certificate x+1.

      The initial value of the valid_policy_tree is a single node with
      valid_policy any-policy, an empty qualifier_set, an
      expected_policy_set with the single value any-policy, and a
      criticality_indicator of FALSE.  This node is considered to be at
      depth zero.

      Figure 3 is a graphic representation of the initial state of the
      valid_policy_tree.  Additional figures will use this format to
      describe changes in the valid_policy_tree during path processing.

              +----------------+
              |   any-policy   |   <---- valid_policy
              +----------------+
              |       {}       |   <---- qualifier_set
              +----------------+
              |     FALSE      |   <---- criticality_indicator
              +----------------+
              |  {any-policy}  |   <---- expected_policy_set
              +----------------+

      Figure 3. Initial value of the valid_policy_tree state variable

      (b) permitted_subtrees:  A set of root names for each name type
      (e.g., X.500 distinguished names, email addresses, or ip
      addresses) defining a set of subtrees within which all subject
      names in subsequent certificates in the certification path MUST
      fall.  This variable includes a set for each name type: the
      initial value for the set for Distinguished Names is the set of



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      all Distinguished names; the initial value for the set of RFC822
      names is the set of all RFC822 names, etc.

      (c) excluded_subtrees:  A set of root names for each name type
      (e.g., X.500 distinguished names, email addresses, or ip
      addresses) defining a set of subtrees within which no subject name
      in subsequent certificates in the certification path may fall.
      This variable includes a set for each name type, and the initial
      value for each set is empty.

      (d) explicit_policy: an integer which indicates if a non-NULL
      valid_policy_tree is required. The integer indicates the number of
      non-self-issued certificates to be processed before this
      requirement is imposed.  Once set, this variable may be decreased,
      but may not be increased. That is, if a certificate in the path
      requires a non-NULL valid_policy_tree, a later certificate can not
      remove this requirement. If initial-explicit-policy is set, then
      the initial value is 0, otherwise the initial value is n+1.

      (e) inhibit_any-policy: an integer which indicates whether the
      any-policy policy identifier is considered a match. The integer
      indicates the number of non-self-issued certificates to be
      processed before the any-policy OID, if asserted in a certificate,
      is ignored. Once set, this variable may be decreased, but may not
      be increased. That is, if a certificate in the path inhibits
      processing of any-policy, a later certificate can not permit it.
      If initial-any-policy-inhibit is set, then the initial value is 0,
      otherwise the initial value is n+1.

      (f) policy_mapping: an integer which indicates if policy mapping
      is permitted.  The integer indicates the number of non-self-issued
      certificates to be processed before policy mapping is inhibited.
      Once set, this variable may be decreased, but may not be
      increased. That is, if a certificate in the path specifies policy
      mapping is not permitted, it can not be overridden by a later
      certificate. If initial-policy-mapping-inhibit is set, then the
      initial value is 0, otherwise the initial value is n+1.

      (g) working_public_key_algorithm: the digital signature algorithm
      used to verify the signature of a certificate.  The
      working_public_key_algorithm is initialized from the trusted
      public key algorithm provided in the trust anchor information.

      (h) working_public_key: the public key used to verify the
      signature of a certificate.  The working_public_key is initialized
      from the trusted public key provided in the trust anchor
      information.




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      (i) working_public_key_parameters:  parameters associated with the
      current public key, that may required to verify a signature
      (depending upon the algorithm).  The working_public_key_parameters
      variable is initialized from the trusted public key parameters
      provided in the trust anchor information.

      (j) working_issuer_name:  the issuer distinguished name expected
      in the next certificate in the chain.  The working_issuer_name is
      initialized to the trusted issuer provided in the trust anchor
      information.

      (k) max_path_length:  this integer is initialized to n, and is
      reset by the path length constraint field within the basic
      constraints extension of a CA certificate.

   Upon completion of the initialization steps, perform the basic
   certificate processing steps specified in 6.1.3.

   6.1.3 Basic Certificate Processing

   The basic path processing actions to be performed for certificate i
   are listed below.

      (a) Verify the basic certificate information.  The certificate
      must satisfy each of the following:

         (1) The certificate was signed with the
         working_public_key_algorithm using the working_public_key and
         the working_public_key_parameters.

         (2) The certificate validity period includes time T.

         (3) At time T, the certificate is not revoked and is not on
         hold status.  This may be determined by obtaining the
         appropriate CRL (see section 6.3), status information, or by
         out-of-band mechanisms.

         (4) The certificate issuer name is the working_issuer_name.

      (b) If certificate i is not self-issued, verify that the subject
      name is within one of the permitted_subtrees for X.500
      distinguished names, and verify that each of the alternative names
      in the subjectAltName extension (critical or non-critical) is
      within one of the permitted_subtrees for that name type.

      (c) If certificate i is not self-issued, verify that the subject
      name is not within one of the excluded_subtrees for X.500
      distinguished names, and verify that each of the alternative names



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      in the subjectAltName extension (critical or non-critical) is not
      within one of the excluded_subtrees for that name type.

      (d) If the certificate policies extension is present in the
      certificiate and the valid_policy_tree is not NULL, process the
      policy information by performing the following steps in order:

         (1) For each policy P not equal to any-policy in the
         certificate policies extension, let P-OID denote the OID in
         policy P and P-Q denote the qualifier set for policy P.
         Perform the following steps in order:

            (i) If the valid_policy_tree includes a node of depth i-1
            where P-OID is in the expected_policy_set, create a child
            node as follows: set the valid_policy to OID- P; set the
            qualifier_set to P-Q, and set the expected_policy_set to {P-
            OID}.

            For example, consider a valid_policy_tree with a node of
            depth i-1 where the expected_policy_set is {Gold, White}.
            Assume the certificate policies Gold and Silver appear in
            the certificate policies extension of certificate i.  The
            Gold policy is matched but the Silver policy is not.  This
            rule will generate a child node of depth i for the Gold
            policy. The result is shown as Figure 4.


























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                          |-----------------|
                          |       Red       |
                          |-----------------|
                          |       {}        |
                          |-----------------|   node of depth i-1
                          |      FALSE      |
                          |-----------------|
                          |  {Gold, White}  |
                          |-----------------|
                                   |
                                   |
                                   |
                                   V
                          |-----------------|
                          |      Gold       |
                          |-----------------|
                          |       {}        |
                          |-----------------| node of depth i
                          |  uninitialized  |
                          |-----------------|
                          |     {Gold}      |
                          |-----------------|

                  Figure 4. Processing an exact match

            (ii) If there was no match in step (i) and the
            valid_policy_tree includes a node of depth i-1 with the
            valid policy any-policy, generate a child node with the
            following values: set the valid_policy to P-OID; set the
            qualifier_set to P-Q, and set the expected_policy_set to {P-
            OID}.

            For example, consider a valid_policy_tree with a node of
            depth i-1 where the valid_policy is any-policy.  Assume the
            certificate policies Gold and Silver appear in the
            certificate policies extension of certificate i.  The Gold
            policy does not have a qualifier, but the Silver policy has
            the qualifier Q-Silver.  If Gold and Silver were not matched
            in (i) above, this rule will generate two child nodes of
            depth i, one for each policy.  The result is shown as Figure
            5.










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                          |-----------------|
                          |   any-policy    |
                          |-----------------|
                          |       {}        |
                          |-----------------| node of depth i-1
                          |      FALSE      |
                          |-----------------|
                          |  {any-policy}   |
                          |-----------------|
                             /           \
                            /             \
                           /               \
                          /                 \
            |-----------------|          |-----------------|
            |      Gold       |          |     Silver      |
            |-----------------|          |-----------------|
            |       {}        |          |   {Q-Silver}    |
            |-----------------| nodes of |-----------------|
            | uninitialized   | depth i  | uninitialized   |
            |-----------------|          |-----------------|
            |     {Gold}      |          |    {Silver}     |
            |-----------------|          |-----------------|

         Figure 5. Processing unmatched policies when a leaf node
         specifies any-policy

         (2) If the certificate policies extension includes the policy
         any-policy with the qualifier set AP-Q and inhibit_any-policy
         is greater than 0, then:

         For each node in the valid_policy_tree of depth i-1, for each
         value in the expected_policy_set (including any-policy) that
         does not appear in a child node, create a child node with the
         following values: set the valid_policy to the value from the
         expected_policy_set in the parent node; set the qualifier_set
         to AP-Q, and set the expected_policy_set to the value in the
         valid_policy from this node.

         For example, consider a valid_policy_tree with a node of depth
         i-1 where the expected_policy_set = {Gold, Silver}.  Assume
         any-policy appears in the certificate policies extension of
         certificate i, but Gold and Silver do not.  This rule will
         generate two child nodes of depth i, one for each policy.  The
         result is shown below as Figure 6.







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                          |-----------------|
                          |      Red        |
                          |-----------------|
                          |       {}        |
                          |-----------------| node of depth i-1
                          |      FALSE      |
                          |-----------------|
                          |  {Gold, Silver} |
                          |-----------------|
                             /           \
                            /             \
                           /               \
                          /                 \
            |-----------------|          |-----------------|
            |      Gold       |          |     Silver      |
            |-----------------|          |-----------------|
            |       {}        |          |       {}        |
            |-----------------| nodes of |-----------------|
            |  uninitialized  | depth i  |  uninitialized  |
            |-----------------|          |-----------------|
            |     {Gold}      |          |    {Silver}     |
            |-----------------|          |-----------------|

         Figure 6. Processing unmatched policies when the certificate
         policies extension specifies any-policy

         (3) If there is a node in the valid_policy_tree of depth i-1 or
         less without any child nodes, delete that node. Repeat this
         step until there are no nodes of depth i-1 or less without
         children.

         For example, consider the valid_policy_tree shown in Figure 7
         below.  The two nodes at depth i-1 that are marked with an 'X'
         have no children, and are deleted.  Applying this rule to the
         resulting tree will cause the node at depth i-2 that is marked
         with an 'Y' to be deleted.  The following application of the
         rule does not cause any nodes to be deleted, and this step is
         complete.













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                                 +-----------+
                                 |           | node of depth i-3
                                 +-----------+
                                 /     |     \
                                /      |      \
                               /       |       \
                   +-----------+ +-----------+ +-----------+
                   |           | |           | |     Y     | nodes of
                   +-----------+ +-----------+ +-----------+ depth i-2
                   /   \              ||             ||
                  /     \             ||             ||
                 /       \            ||             ||
      +-----------+ +-----------+ +-----------+ +-----------+ nodes of
      |           | |     X     | |           | |   X       |  depth
      +-----------+ +-----------+ +-----------+ +-----------+   i-1
            |                      /    |    \
            |                     /     |     \
            |                    /      |      \
      +-----------+ +-----------+ +-----------+ +-----------+ nodes of
      |           | |           | |           | |           |  depth
      +-----------+ +-----------+ +-----------+ +-----------+   i

             Figure 7.  Pruning the valid_policy_tree

         (4) If the certificate policies extension was marked as
         critical, set the criticality_indicator in all nodes of depth i
         to TRUE. If the certificate policies extension was not marked
         critical, set the criticality_indicator in all nodes of depth i
         to FALSE.

      (e) If the certificate policies extension is not present, set the
      valid_policy_tree to NULL.

      (f) verify that either explicit_policy is greater than 0 or the
      valid_policy_tree is not equal to NULL;

   If any of steps (a), (b), (c), or (f) fails, the procedure
   terminates, returning a failure indication and an appropriate reason.

   If i is not equal to n, continue by performing the preparatory steps
   listed in 6.1.4.  If i is equal to n, perform the wrap-up steps
   listed in 6.1.5.

   6.1.4 Preparation for Certificate i+1

   To prepare for processing of certificate i+1, perform the following
   steps for certificate i:




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      (a) If a policy mapping extension is present, verify that the
      special value any-policy does not appear as an issuerDomainPolicy
      or a subjectDomainPolicy.

      (b) If a policy mapping extension is present, then for each
      issuerDomainPolicy ID-P in the policy mapping extension:

         (1) If the policy_mapping variable is greater than 0, for each
         node in the valid_policy_tree of depth i where ID-P is the
         valid_policy, set expected_policy_set to the set of
         subjectDomainPolicy values that are specified as equivalent to
         ID-P by the policy mapping extension.

         If no node of depth i in the valid_policy_tree has a
         valid_policy of ID-P but there is a node of depth i with a
         valid_policy of any-policy, then generate a child node of the
         node of depth i-1 that has a valid_policy of any-policy as
         follows:

            (i) set the valid_policy to ID-P;

            (ii) set the qualifier_set to the qualifier set of the
            policy any-policy in the certificate policies extension of
            certificate i;

            (iii) set the criticality_indicator to the criticality of
            the certificate policies extension of certificate i;

            (iv) and set the expected_policy_set to the set of
            subjectDomainPolicy values that are specified as equivalent
            to ID-P by the policy mappings extension.

         (2) If the policy_mapping variable is equal to 0:

            (i) delete each node of depth i in the valid_policy_tree
            where ID-P is the valid_policy.

            (ii) If there is a node in the valid_policy_tree of depth
            i-1 or less without any child nodes, delete that node.
            Repeat this step until there are no nodes of depth i-1 or
            less without children.

      (c) Assign the certificate subject name to working_issuer_name.

      (d) Assign the certificate subjectPublicKey to working_public_key.

      (e) If the subjectPublicKeyInfo field of the certificate contains
      an algorithm field with non-null parameters, assign the parameters



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      to the working_public_key_parameters variable.

      If the subjectPublicKeyInfo field of the certificate contains an
      algorithm field with null parameters or parameters are omitted,
      compare the certificate subjectPublicKey algorithm to the
      working_public_key_algorithm.  If the certificate subjectPublicKey
      algorithm and the working_public_key_algorithm are different, set
      the working_public_key_parameters to null.

      (f) Assign the certificate subjectPublicKey algorithm to the
      working_public_key_algorithm variable.

      (g) If a name constraints extension is included in the
      certificate, modify the permitted_subtrees and excluded_subtrees
      state variables as follows:

         (1) If permittedSubtrees is present in the certificate, set the
         permitted_subtrees state variable to the intersection of its
         previous value and the value indicated in the extension field.
         If permittedSubtrees does not include a particular name type,
         the permitted_subtrees state variable is unchanged for that
         name type.

         (2) If excludedSubtrees is present in the certificate, set the
         excluded_subtrees state variable to the union of its previous
         value and the value indicated in the extension field. If
         excludedSubtrees does not include a particular name type, the
         excluded_subtrees state variable is unchanged for that name
         type.

      (h) If the issuer and subject names are not identical:

         (1) If explicit_policy is not 0, decrement explicit_policy by
         1.

         (2) If policy_mapping is not 0, decrement policy_mapping by 1.

         (3) If inhibit_any-policy is not 0, decrement inhibit_any-
         policy by 1.

      (i) If a policy constraints extension is included in the
      certificate, modify the explicit_policy and policy_mapping state
      variables as follows:

         (1) If requireExplicitPolicy is present and is less than
         explicit_policy, set explicit_policy to the value of
         requireExplicitPolicy.




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         (2) If inhibitPolicyMapping is present and is less than
         policy_mapping, set policy_mapping to the value of
         inhibitPolicyMapping.

      (j) If the inhibitAnyPolicy extension is included in the
      certificate and is less than inhibit_any-policy, set inhibit_any-
      policy to the value of inhibitAnyPolicy.

      (k) Verify that the certificate is a CA certificate (as specified
      in a basicConstraints extension or as verified out-of-band).

      (l) If the certificate was not self-issued, verify that
      max_path_length is greater than zero and decrement max_path_length
      by 1.

      (m) If pathLengthConstraint is present in the certificate and is
      less than max_path_length, set max_path_length to the value of
      pathLengthConstraint.

      (n) If a key usage extension is present and marked critical,
      verify that the keyCertSign bit is set.

      (o) Recognize and process any other critical extension present in
      the certificate.

   If check (a), (k), (l), (n) or (o) fails, the procedure terminates,
   returning a failure indication and an appropriate reason.

   If (a), (k), (l), (n) and (o) have completed successfully, increment
   i and perform the basic certificate processing specified in 6.1.2.

   6.1.5 Wrap-up procedure

   To complete the processing of the end entity certificate, perform the
   following steps for certificate n:

      (a) If certificate n was not self-issued and explicit_policy is
      not 0, decrement explicit_policy by 1.

      (b) If a policy constraints extension is included in the
      certificate and requireExplicitPolicy is present and has a value
      of 0, set the explicit_policy state variable to 0.

      (c) Assign the certificate subjectPublicKey to working_public_key.

      (d) If the subjectPublicKeyInfo field of the certificate contains
      an algorithm field with non-null parameters, assign the parameters
      to the working_public_key_parameters variable.



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      If the subjectPublicKeyInfo field of the certificate contains an
      algorithm field with null parameters or parameters are omitted,
      compare the certificate subjectPublicKey algorithm to the
      working_public_key_algorithm.  If the certificate subjectPublicKey
      algorithm and the working_public_key_algorithm are different, set
      the working_public_key_parameters to null.

      (e) Assign the certificate subjectPublicKey algorithm to the
      working_public_key_algorithm variable.

      (f) Recognize and process any other critical extension present in
      the certificate n.

      (g) Calculate the intersection of the valid_policy_tree and the
      user-initial-policy-set, as follows:

         (i) If the valid_policy_tree is NULL, the intersection is NULL.

         (ii) If the valid_policy_tree is not NULL and the user-initial-
         policy-set is any-policy, the intersection is the entire
         valid_policy_tree.

         (iii) If the valid_policy_tree is not NULL and the user-
         initial-policy-set is not any-policy, calculate the
         intersection of the valid_policy_tree and the user-initial-
         policy-set as follows:

            1. Determine the set of policy nodes whose parent nodes have
            a valid_policy of any-policy.  This is the
            valid_policy_node_set.

            2. If the valid_policy of any node in the
            valid_policy_node_set is not in the user-initial-policy-set
            and is not any-policy, delete this node and all its
            children.

            3. If there is a node in the valid_policy_tree of depth n-1
            or less without any child nodes, delete that node. Repeat
            this step until there are no nodes of depth n-1 or less
            without children.

   If either (1) the value of explicit_policy variable is greater than
   zero, or (2) the valid_policy_tree is not NULL, then path processing
   has succeeded.

6.1.6 Outputs

   If path processing succeeds, the procedure terminates, returning a



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   success indication together with final value of the
   valid_policy_tree, the working_public_key, the
   working_public_key_algorithm, and the working_public_key_parameters.

6.2 Using the Path Validation Algorithm

   The path validation algorithm describes the process of validating a
   single certification path.  While each path begins with a specific
   trust anchor, there is no requirement that all paths validated by a
   particular system share a single trust anchor.  An implementation
   that supports multiple trust anchors may augment the algorithm
   prresented in section 6.1 to further limit the set of valid paths
   which begin with a particular trust anchor.  For example, an
   implementation may specify name constraints that apply to a specific
   trust anchor.

   The selection of one or more trusted CAs is a local decision.  A
   system may provide any one of its trusted CAs as the trust anchor for
   a particular path.  The inputs to the path validation algorithm may
   be different for each path.  The inputs used to process a path may
   reflect application-specific requirements or limitations in the trust
   accorded a particular trust anchor.  For example, a trusted CA may
   only be trusted for a particular certificate policy.  This
   restriction can be expressed through the inputs to the path
   validation procedure.

   It is also possible to specify an extended version of the above
   certification path processing procedure which results in default
   behavior identical to the rules of PEM [RFC 1422].  In this extended
   version, additional inputs to the procedure are a list of one or more
   Policy Certification Authorities (PCAs) names and an indicator of the
   position in 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 no valid PCA name is
   found, and if the certification path cannot be validated on the basis
   of identified policies, then the certification path is considered
   invalid.

6.3 CRL Validation

   This section describes the steps necessary to determine if a
   certificate is revoked or on hold status when CRLs are the revocation
   mechanism used by the certificate issuer.  Conforming implementations
   of this specification are not required to implement this algorithm,
   but MUST be functionally equivalent to the external behavior
   resulting from this procedure.  Any algorithm may be used by a



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   particular implementation so long as it derives the correct result.

   This algorithm defines a set of inputs, a set of state variables, and
   processing steps that are performed for each certificate in the path.

6.3.1 Revocation Inputs

   To support revocation processing, the algorithm requires two inputs:

      (a) certificate:  the algorithm requires the certificate serial
      number and issuer name to determine if a certificate is on a
      particular CRL.  The basicConstraints extension is used to
      determine whether the supplied certificate is associated with a CA
      or an end-entity.  If present, the algorithm may use the
      cRLDistributionsPoint and freshestCRL extensions to determine
      revocation status.

      (b) use-deltas: This boolean input determines if the delta needs
      to be checked if the CRL is still valid.

      Note that implementations supporting legacy PKIs, such as RFC 1422
      and X.509 version 1, will need an additional input indicating
      whether the supplied certificate is associated with a CA or an
      end-entity.

6.3.2 Initialization and Revocation State Variables

   To support CRL processing, the algorithm requires the following state
   variables:

      (a) reasons_mask: This variable contains the set of revocation
      reasons supported by the CRLs and delta CRLs processed so far.
      The legal members of the set are the possible values for
      reasonflags: unspecified; keyCompromise; caCompromise;
      affiliationChanged; superseded; cessationOfOperation; and
      certificateHold.  The special value all-reasons is used to denote
      the set of all legal members.  This variable is initialized to the
      empty set.

      (b) cert_status: This variable contains the status of the
      certificate.  Legal values are unspecified; keyCompromise;
      caCompromise; affiliationChanged; superseded;
      cessationOfOperation; and certificateHold, the special value
      UNREVOKED, or the special value UNDETERMINED.  This variable is
      initialized to the special value UNREVOKED.

      (c) interim_reasons_mask: This contains the set of revocation
      reasons supported by the CRL or delta CRL currently being



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      processed.

   Note: In some environments, it is not necessary to check all reason
   codes.  For example, some envornments only are concerned with
   caCompromise and keyCompromise for CA certificates.  This algorithnm
   checks all reason codes.  Additional processing and state variables
   may be necessary to limit the checking to a subset of the reason
   codes.

6.3.3 CRL Processing

   This algorithm begins by assuming the certificate is not revoked.
   The algorithm checks one or more CRLs until either the certificate
   status is determined to be revoked or sufficent CRLs have been
   checked to cover all reason codes.

   For each distribution point (DP) in the crl distribution points
   extension while ((reasons_mask is not all-reasons) and (cert_status
   is UNREVOKED))

      (1) locate the corresponding CRL in CRL cache, and perform the
      following verifications:

         (a) compute the interim_reasons_mask for this CRL as follows:

            1. if the CRL includes reasons and the DP includes reasons,
            then set interim_reasons_mask to the intersection of of
            reasons in the DP and reasons in CRL reasons extension.

            2. if the CRL includes reasons but the DP omits reasons,
            then set interim_reasons_mask to the value of CRL reasons.

            3. if the CRL omits reasons but the DP includes reasons,
            then set interim_reasons_mask to the value of DP reasons.

            4. if the CRL omits reasons and the DP omits reasons, then
            set interim_reasons_mask to the special value all-reasons.

         Verify that interim_reasons_mask includes one or more reasons
         that is not included in the reasons_mask.

         (b) Verify the issuer of the CRL as follows:

            if the DP includes cRLIssuer, then verify that the CRL
            issuer matches cRLIssuer else verify that the CRL issuer
            matches the certificate issuer.

            (c) obtain and validate the certification path for the CRL



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            issuer.

            (d) validate the signature on the CRL.

      (2) If each of the verifications (a) through (d) succeeds, then
      perform the following steps:

         (a) If the value of next update field is before the current-
         time, otain an appropriate delta CRL or discard the CRL.

         (b) If the user wants freshest available info AND the freshest
         CRL extension is present, check for a corresponding delta for
         this base.

         (c) If a delta was obtained in (a) or (b), verify that the
         delta CRL addresses the same set of certificates and the same
         set of reasons as the CRL.

         (d) Perform the checks in step 1 (b) and (c):

            1. obtain and validate the certification path for the delta
            issuer

            2. validate the signature on the delta CRL

            (e) If a delta CRL was obtained in (a) or (b), and the
            verifications (c) and (d) suceeded, combine the base and
            delta to form a complete CRL.

      (3) If steps and (1) and (2) succeed, then set reasons_mask to the
      union of reasons_mask and interim_reasons_mask

      (4) Search for the certificate on the CRL

         (a) search for the serial number on the CRL

         (b) if (a) succeeds, verify that (1) the CRL entry extension
         Certificate issuer is not present or (2) the issuer identified
         in the CRL entry extension Certificate issuer is the issuer of
         the certificate.

         (c) if (a) and (b) succeeded, set the cert_status variable as
         appropriate:

            1. if the reasons extension is present, set the cert_status
            variable to the value of the reasons extension

            2. if the reasons extension is not present, set the



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            cert_status variable to the special value not-specified.

      if ((reasons_mask is all-reasons) OR (if cert_status is not
      UNREVOKED) return cert_status

      If all CRLs named in the crl distribution points extension have
      been exhausted, and the reasons_mask is not all-reasons and the
      cert_status is still UNREVOKED, the verifier must obtain
      additional CRLs.

      The verifier must repeat the process above with the additional
      CRLs not specified in a distribution point.

      If all CRLs are exhausted and the reasons_mask is not all-reasons
      return the cert_status UNDETERMINED.

7 References

   [RFC 791] J. Postel, "Internet Protocol", September 1981.

   [RFC 822] D. Crocker, "Standard for the format of ARPA Internet text
            messages", August 1982.

   [RFC 1034] P.V. Mockapetris, "Domain names - concepts and
            facilities", November 1987.

   [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.

   [RFC 1510] Kohl, J., and C. Neuman, "The Kerberos Network
            Authentication Service (V5)," RFC 1510, September 1993.

   [RFC 1519] V. Fuller, T. Li, J. Yu, and K. Varadhan. "Classless
            Inter-Domain Routing (CIDR): an Address Assignment and
            Aggregation Strategy", September 1993.

   [RFC 1738] Berners-Lee, T., Masinter L., and M. McCahill.
            "Uniform Resource Locators (URL)", RFC 1738, December 1994.

   [RFC 1778] Howes, T., Kille S., Yeong, W. and C. Robbins. "The
         String Representation of Standard Attribute Syntaxes,"
         RFC 1778, March 1995.




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   [RFC 1883] S. Deering and R. Hinden. "Internet Protocol, Version 6
            (IPv6) Specification", December 1995.

   [RFC 2119] S. Bradner, "Key words for use in RFCs to Indicate
            Requirement Levels", March 1997.

   [RFC 2247] Kille, S., Wahl, M., Grimstad, A., Huber, R. and S.
         Sataluri. "Using Domains in LDAP/X.500 Distinguished Names",
         RFC 2247, January 1998.

   [RFC 2277] H. Alvestrand, "IETF Policy on Character Sets and
            Languages", January 1998.

   [RFC 2279] F. Yergeau, "UTF-8, a transformation format of ISO 10646",
            January 1998.

   [RFC 2560] Myers, M., Ankney R., Malpani A., Galperin S., and
            C. Adams, "Online Certificate Status Protocal - OCSP",
         June 1999.

   [SDN.701] SDN.701, "Message Security Protocol 4.0", Revision A
            1997-02-06.

   [X.208]  CCITT Recommendation X.208: Specification of Abstract
           Syntax Notation One (ASN.1), 1988.

   [X.501]  ITU-T Recommendation X.501: Information
            Technology - Open Systems Interconnection - The
            Directory: Models, 1993.

   [X.509]  ITU-T Recommendation X.509 (1997 E): Information
            Technology - Open Systems Interconnection - The
            Directory: Authentication Framework, June 1997.

   [X.520]  ITU-T Recommendation X.520: Information
            Technology - Open Systems Interconnection - The
            Directory: Selected Attribute Types, 1993.

   [X9.55]  ANSI X9.55-1995, Public Key Cryptography For The Financial
            Services Industry: Extensions To Public Key Certificates
            And Certificate Revocation Lists, 8 December, 1995.

   [PKINIT] Tung, B., Neuman C., Hur M., Medvinsky A., Medvinsky S.,
         Wray J., and J. Trostle, "Public Key Cryptography for
         Initial Authentciaion in Kerberos,"
         draft-ietf-cat-kerberos-pk-init-11.txt, March 15, 2000.

   [PKIX ALGS] Bassham, L., Housley, R., and W. Polk, "Internet X.509



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            Public Key Infrastructure Representation of Public Keys
         and Digital Signatures,"
         draft-ietf-pkix-ipki-pkalgs-00.txt, July 14, 2000.

   [PKIX TSA] Cain, P., Pinkas, D., and R. Zuccherato, "Internet X.509
            Public Key Infrastructure Time Stamp Protocol,"
         draft-ietf-pkix-time-stamp-12.txt, November, 2000.

8  Intellectual Property Rights

   The IETF has been notified of intellectual property rights claimed in
   regard to some or all of the specification contained in this
   document.  For more information consult the online list of claimed
   rights.

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights. Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11. Copies of
   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to
   obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification can
   be obtained from the IETF Secretariat.

9  Security Considerations

   The majority of this specification is devoted to the format and
   content of certificates and CRLs.  Since certificates and CRLs are
   digitally signed, no additional integrity service is necessary.
   Neither certificates nor CRLs need be kept secret, and unrestricted
   and anonymous access to certificates and CRLs has no security
   implications.

   However, security factors outside the scope of this specification
   will affect the assurance provided to certificate users.  This
   section highlights critical issues that should be considered by
   implementors, administrators, and users.

   The procedures performed by CAs and RAs to validate the binding of
   the subject's identity of their public key greatly affect the
   assurance that should be placed in the certificate.  Relying parties
   may wish to review the CA's certificate practice statement.  This may
   be particularly important when issuing certificates to other CAs.



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   The use of a single key pair for both signature and other purposes is
   strongly discouraged. Use of separate key pairs for signature and key
   management provides several benefits to the users. The ramifications
   associated with loss or disclosure of a signature key are different
   from loss or disclosure of a key management key. Using separate key
   pairs permits a balanced and flexible response.  Similarly, different
   validity periods or key lengths for each key pair may be appropriate
   in some application environments. Unfortunately, some legacy
   applications (e.g., SSL) use a single key pair for signature and key
   management.

   The protection afforded private keys is a critical factor in
   maintaining security.  On a small scale, failure of users to protect
   their private keys will permit an attacker to masquerade as them, or
   decrypt their personal information. On a larger scale, compromise of
   a CA's private signing key may have a catastrophic effect.  If an
   attacker obtains the private key unnoticed, the attacker may issue
   bogus certificates and CRLs.  Existence of bogus certificates and
   CRLs will undermine confidence in the system.  If the compromise is
   detected, all certificates issued to the CA MUST be revoked,
   preventing services between its users and users of other CAs.
   Rebuilding after such a compromise will be problematic, so CAs are
   advised to implement a combination of strong technical measures
   (e.g., tamper-resistant cryptographic modules) and appropriate
   management procedures (e.g., separation of duties) to avoid such an
   incident.

   Loss of a CA's private signing key may also be problematic.  The CA
   would not be able to produce CRLs or perform normal key rollover.
   CAs are advised to maintain secure backup for signing keys.  The
   security of the key backup procedures is a critical factor in
   avoiding key compromise.

   The availability and freshness of revocation information will affect
   the degree of assurance that should be placed in a certificate.
   While certificates expire naturally, events may occur during its
   natural lifetime which negate the binding between the subject and
   public key.  If revocation information is untimely or unavailable,
   the assurance associated with the binding is clearly reduced.
   Similarly, implementations of the Path Validation mechanism described
   in section 6 that omit revocation checking provide less assurance
   than those that support it.

   The path validation algorithm depends on the certain knowledge of the
   public keys (and other information) about one or more trusted CAs.
   The decision to trust a CA is an important decision as it ultimately
   determines the trust afforded a certificate. The authenticated
   distribution of trusted CA public keys (usually in the form of a



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   "self-signed" certificate) is a security critical out of band process
   that is beyond the scope of this specification.

   In addition, where a key compromise or CA failure occurs for a
   trusted CA, the user will need to modify the information provided to
   the path validation routine.  Selection of too many trusted CAs will
   make the trusted CA information difficult to maintain.  On the other
   hand, selection of only one trusted CA may limit users to a closed
   community of users until a global PKI emerges.

   The quality of implementations that process certificates may also
   affect the degree of assurance provided.  The path validation
   algorithm described in section 6 relies upon the integrity of the
   trusted CA information, and especially the integrity of the public
   keys associated with the trusted CAs.  By substituting public keys
   for which an attacker has the private key, an attacker could trick
   the user into accepting false certificates.

   The binding between a key and certificate subject cannot be stronger
   than the cryptographic module implementation and algorithms used to
   generate the signature.  Short key lengths or weak hash algorithms
   will limit the utility of a certificate.  CAs are encouraged to note
   advances in cryptology so they can employ strong cryptographic
   techniques.  In addition, CAs should decline to issue certificates to
   CAs or end entities that generate weak signatures.

   Inconsistent application of name comparison rules may result in
   acceptance of invalid X.509 certification paths, or rejection of
   valid ones.  The X.500 series of specifications defines rules for
   comparing distinguished names require comparison of strings without
   regard to case, character set, multi-character white space substring,
   or leading and trailing white space.  This specification relaxes
   these requirements, requiring support for binary comparison at a
   minimum.

   CAs MUST encode the distinguished name in the subject field of a CA
   certificate identically to the distinguished name in the issuer field
   in certificates issued by the latter CA.  If CAs use different
   encodings, implementations of this specification may fail to
   recognize name chains for paths that include this certificate.  As a
   consequence, valid paths could be rejected.

   In addition, name constraints for distinguished names MUST be stated
   identically to the encoding used in the subject field or
   subjectAltName extension.  If not, (1) name constraints stated as
   excludedSubTrees will not match and invalid paths will be accepted
   and (2) name constraints expressed as permittedSubtrees will not
   match and valid paths will be rejected.  To avoid acceptance of



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   invalid paths, CAs should state name constraints for distinguished
   names as permittedSubtrees where ever possible.

















































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Appendix A. Psuedo-ASN.1 Structures and OIDs

   This section describes data objects used by conforming PKI components
   in an "ASN.1-like" syntax.  This syntax is a hybrid of the 1988 and
   1993 ASN.1 syntaxes.  The 1988 ASN.1 syntax is augmented with 1993
   UNIVERSAL Types UniversalString, BMPString and UTF8String.

   The ASN.1 syntax does not permit the inclusion of type statements in
   the ASN.1 module, and the 1993 ASN.1 standard does not permit use of
   the new UNIVERSAL types in modules using the 1988 syntax.  As a
   result, this module does not conform to either version of the ASN.1
   standard.

   This appendix may be converted into 1988 ASN.1 by replacing the
   defintions for the UNIVERSAL Types with the 1988 catch-all "ANY".

A.1 Explicitly Tagged Module, 1988 Syntax

PKIX1Explicit88 {iso(1) identified-organization(3) dod(6) internet(1)
  security(5) mechanisms(5) pkix(7) id-mod(0) id-pkix1-explicit(18)}


DEFINITIONS EXPLICIT TAGS ::=

BEGIN

-- EXPORTS ALL --

-- IMPORTS NONE --

-- UNIVERSAL Types defined in '93 and '98 ASN.1
-- but required by this specification

UniversalString ::= [UNIVERSAL 28] IMPLICIT OCTET STRING
        -- UniversalString is defined in ASN.1:1993

BMPString ::= [UNIVERSAL 30] IMPLICIT OCTET STRING
      -- BMPString is the subtype of UniversalString and models
     -- the Basic Multilingual Plane of ISO/IEC/ITU 10646-1

UTF8String ::= [UNIVERSAL 12] IMPLICIT OCTET STRING
     -- The content of this type conforms to RFC 2279.

--
-- PKIX specific OIDs

id-pkix  OBJECT IDENTIFIER  ::=
         { iso(1) identified-organization(3) dod(6) internet(1)



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                    security(5) mechanisms(5) pkix(7) }
-- PKIX arcs

id-pe OBJECT IDENTIFIER  ::=  { id-pkix 1 }
     -- arc for private certificate extensions
id-qt OBJECT IDENTIFIER ::= { id-pkix 2 }
     -- arc for policy qualifier types
id-kp OBJECT IDENTIFIER ::= { id-pkix 3 }
     -- arc for extended key purpose OIDS
id-ad OBJECT IDENTIFIER ::= { id-pkix 48 }
     -- arc for access descriptors

-- policyQualifierIds for Internet policy qualifiers

id-qt-cps      OBJECT IDENTIFIER ::=  { id-qt 1 }
     -- OID for CPS qualifier
id-qt-unotice  OBJECT IDENTIFIER ::=  { id-qt 2 }
     -- OID for user notice qualifier

-- access descriptor definitions

id-ad-ocsp      OBJECT IDENTIFIER ::= { id-ad 1 }
id-ad-caIssuers OBJECT IDENTIFIER ::= { id-ad 2 }
id-ad-timeStamping OBJECT IDENTIFIER ::= { id-ad 3 }
id-ad-caRepository OBJECT IDENTIFIER ::= { id-ad 5 }

-- attribute data types --

Attribute ::=  SEQUENCE {
     type      AttributeType,
     values    SET OF AttributeValue
          -- at least one value is required -- }

AttributeType       ::=   OBJECT IDENTIFIER

AttributeValue      ::=   ANY

AttributeTypeAndValue         ::=  SEQUENCE {
     type AttributeType,
     value     AttributeValue }

-- suggested naming attributes: Definition of the following
--  information object set may be augmented to meet local
--  requirements.  Note that deleting members of the set may
--  prevent interoperability with conforming implementations.
--  presented in pairs: the AttributeType followed by the
--  type definition for the corresponding AttributeValue




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--Arc for standard naming attributes
id-at          OBJECT IDENTIFIER ::= {joint-iso-ccitt(2) ds(5) 4}

-- Naming attributes of type X520name

id-at-name          AttributeType  ::=  {id-at 41}
id-at-surname       AttributeType  ::=  {id-at 4}
id-at-givenName     AttributeType  ::=  {id-at 42}
id-at-initials           AttributeType  ::=  {id-at 43}
id-at-generationQualifier     AttributeType  ::=  {id-at 44}


X520name  ::= CHOICE {
      teletexString     TeletexString (SIZE (1..ub-name)),
      printableString        PrintableString (SIZE (1..ub-name)),
      universalString        UniversalString (SIZE (1..ub-name)),
      utf8String            UTF8String (SIZE (1..ub-name)),
      bmpString             BMPString (SIZE(1..ub-name))   }

-- Naming attributes of type X520CommonName

id-at-commonName    AttributeType  ::=  {id-at 3}

X520CommonName      ::=   CHOICE {
      teletexString     TeletexString (SIZE (1..ub-common-name)),
      printableString        PrintableString (SIZE (1..ub-common-name)),
      universalString        UniversalString (SIZE (1..ub-common-name)),
      utf8String            UTF8String (SIZE (1..ub-common-name)),
      bmpString             BMPString (SIZE(1..ub-common-name))   }

-- Naming attributes of type X520LocalityName

id-at-localityName  AttributeType  ::=  {id-at 7}

X520LocalityName ::= CHOICE {
      teletexString   TeletexString (SIZE (1..ub-locality-name)),
      printableString      PrintableString (SIZE (1..ub-locality-name)),
      universalString      UniversalString (SIZE (1..ub-locality-name)),
      utf8String          UTF8String (SIZE (1..ub-locality-name)),
      bmpString           BMPString (SIZE(1..ub-locality-name))   }

-- Naming attributes of type X520StateOrProvinceName

id-at-stateOrProvinceName     AttributeType  ::=  {id-at 8}

X520StateOrProvinceName  ::= CHOICE {
      teletexString   TeletexString (SIZE (1..ub-state-name)),
      printableString      PrintableString (SIZE (1..ub-state-name)),



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      universalString      UniversalString (SIZE (1..ub-state-name)),
      utf8String          UTF8String (SIZE (1..ub-state-name)),
      bmpString           BMPString (SIZE(1..ub-state-name))   }

-- Naming attributes of type X520OrganizationName

id-at-organizationName        AttributeType  ::=  {id-at 10}

X520OrganizationName ::= CHOICE {
  teletexString         TeletexString (SIZE (1..ub-organization-name)),
  printableString   PrintableString (SIZE (1..ub-organization-name)),
  universalString   UniversalString (SIZE (1..ub-organization-name)),
  utf8String        UTF8String (SIZE (1..ub-organization-name)),
  bmpString         BMPString (SIZE(1..ub-organization-name))   }

-- Naming attributes of type X520OrganizationalUnitName

id-at-organizationalUnitName  AttributeType  ::=  {id-at 11}

X520OrganizationalUnitName ::= CHOICE {
 teletexString    TeletexString (SIZE (1..ub-organizational-unit-name)),
 printableString    PrintableString
                      (SIZE (1..ub-organizational-unit-name)),
 universalString    UniversalString
                      (SIZE (1..ub-organizational-unit-name)),
 utf8String       UTF8String (SIZE (1..ub-organizational-unit-name)),
 bmpString        BMPString (SIZE(1..ub-organizational-unit-name))   }

-- Naming attributes of type X520Title

id-at-title    AttributeType  ::=  {id-at 12}

X520Title ::=  CHOICE {
      teletexString     TeletexString (SIZE (1..ub-title)),
      printableString        PrintableString (SIZE (1..ub-title)),
      universalString        UniversalString (SIZE (1..ub-title)),
      utf8String            UTF8String (SIZE (1..ub-title)),
      bmpString             BMPString (SIZE(1..ub-title))   }

-- Naming attributes of type X520dnQualifier

id-at-dnQualifier   AttributeType  ::=  {id-at 46}

X520dnQualifier ::= PrintableString

-- Naming attributes of type X520countryName

id-at-countryName   AttributeType  ::=  {id-at 6}



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X520countryName ::= PrintableString (SIZE (2)) -- IS 3166 codes

-- Naming attributes of type X520SerialNumber

id-at-serialNumber      AttributeType ::= { id-at 5 }

X520SerialNumber ::=     PrintableString (SIZE (1..ub-serial-number))

-- Naming attributes of type DomainComponent (from RFC 2247)

id-domainComponent     OBJECT IDENTIFIER  ::=
                                    { 0 9 2342 19200300 100 1 25 }

DomainComponent ::=     IA5String

-- Legacy attributes

pkcs-9 OBJECT IDENTIFIER ::=
       { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) 9 }

id-emailAddress AttributeType ::= { pkcs-9 1 }

EmailAddress ::= IA5String (SIZE (1..ub-emailaddress-length))

-- naming data types --

Name      ::=   CHOICE { -- only one possibility for now --
                        rdnSequence  RDNSequence }

RDNSequence    ::=   SEQUENCE OF RelativeDistinguishedName

DistinguishedName   ::=   RDNSequence

RelativeDistinguishedName  ::=
                    SET SIZE (1 .. MAX) OF AttributeTypeAndValue

-- Directory string type --

DirectoryString ::= CHOICE {
      teletexString      TeletexString (SIZE (1..MAX)),
      printableString         PrintableString (SIZE (1..MAX)),
      universalString         UniversalString (SIZE (1..MAX)),
      utf8String              UTF8String (SIZE (1..MAX)),
      bmpString               BMPString (SIZE(1..MAX))   }

-- certificate and CRL specific structures begin here

Certificate  ::=  SEQUENCE  {



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     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)  }

CertificateSerialNumber  ::=  INTEGER

Validity ::= SEQUENCE {
     notBefore      Time,
     notAfter       Time }

Time ::= CHOICE {
     utcTime        UTCTime,
     generalTime    GeneralizedTime }

UniqueIdentifier  ::=  BIT STRING

SubjectPublicKeyInfo  ::=  SEQUENCE  {
     algorithm            AlgorithmIdentifier,
     subjectPublicKey     BIT STRING  }

Extensions  ::=  SEQUENCE SIZE (1..MAX) OF Extension

Extension  ::=  SEQUENCE  {
     extnID      OBJECT IDENTIFIER,
     critical    BOOLEAN DEFAULT FALSE,
     extnValue   OCTET STRING  }

-- CRL structures

CertificateList  ::=  SEQUENCE  {
     tbsCertList          TBSCertList,



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     signatureAlgorithm   AlgorithmIdentifier,
     signature            BIT STRING  }

TBSCertList  ::=  SEQUENCE  {
     version                 Version OPTIONAL,
                                  -- if present, MUST be v2
     signature               AlgorithmIdentifier,
     issuer                  Name,
     thisUpdate              Time,
     nextUpdate              Time OPTIONAL,
     revokedCertificates     SEQUENCE OF SEQUENCE  {
          userCertificate         CertificateSerialNumber,
          revocationDate          Time,
          crlEntryExtensions      Extensions OPTIONAL
                                         -- if present, MUST be v2
                               }  OPTIONAL,
     crlExtensions           [0] Extensions OPTIONAL
                                         -- if present, MUST be v2 -- }

-- Version, Time, CertificateSerialNumber, and Extensions were
-- defined earlier for use in the certificate structure

AlgorithmIdentifier  ::=  SEQUENCE  {
     algorithm               OBJECT IDENTIFIER,
     parameters              ANY DEFINED BY algorithm OPTIONAL  }
                                -- contains a value of the type
                                -- registered for use with the
                                -- algorithm object identifier value

-- x400 address syntax starts here
--   OR Names

ORAddress ::= SEQUENCE {
   built-in-standard-attributes BuiltInStandardAttributes,
   built-in-domain-defined-attributes
               BuiltInDomainDefinedAttributes OPTIONAL,
   -- see also teletex-domain-defined-attributes
   extension-attributes ExtensionAttributes OPTIONAL }
--   The OR-address is semantically absent from the OR-name if the
--   built-in-standard-attribute sequence is empty and the
--   built-in-domain-defined-attributes and extension-attributes are
--   both omitted.

--   Built-in Standard Attributes

BuiltInStandardAttributes ::= SEQUENCE {
   country-name CountryName OPTIONAL,
   administration-domain-name AdministrationDomainName OPTIONAL,



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   network-address  [0] NetworkAddress OPTIONAL,
   -- see also extended-network-address
   terminal-identifier   [1] TerminalIdentifier OPTIONAL,
   private-domain-name   [2] PrivateDomainName OPTIONAL,
   organization-name     [3] OrganizationName OPTIONAL,
   -- see also teletex-organization-name
   numeric-user-identifier    [4] NumericUserIdentifier OPTIONAL,
   personal-name    [5] PersonalName OPTIONAL,
   -- see also teletex-personal-name
   organizational-unit-names  [6] OrganizationalUnitNames OPTIONAL
   -- see also teletex-organizational-unit-names -- }

CountryName ::= [APPLICATION 1] CHOICE {
   x121-dcc-code NumericString
          (SIZE (ub-country-name-numeric-length)),
   iso-3166-alpha2-code PrintableString
          (SIZE (ub-country-name-alpha-length)) }

AdministrationDomainName ::= [APPLICATION 2] CHOICE {
   numeric NumericString (SIZE (0..ub-domain-name-length)),
   printable PrintableString (SIZE (0..ub-domain-name-length)) }

NetworkAddress ::= X121Address  -- see also extended-network-address

X121Address ::= NumericString (SIZE (1..ub-x121-address-length))

TerminalIdentifier ::= PrintableString (SIZE (1..ub-terminal-id-length))

PrivateDomainName ::= CHOICE {
   numeric NumericString (SIZE (1..ub-domain-name-length)),
   printable PrintableString (SIZE (1..ub-domain-name-length)) }

OrganizationName ::= PrintableString
                            (SIZE (1..ub-organization-name-length))
-- see also teletex-organization-name

NumericUserIdentifier ::= NumericString
                            (SIZE (1..ub-numeric-user-id-length))

PersonalName ::= SET {
   surname [0] PrintableString (SIZE (1..ub-surname-length)),
   given-name [1] PrintableString
               (SIZE (1..ub-given-name-length)) OPTIONAL,
   initials [2] PrintableString (SIZE (1..ub-initials-length)) OPTIONAL,
   generation-qualifier [3] PrintableString
          (SIZE (1..ub-generation-qualifier-length)) OPTIONAL }
-- see also teletex-personal-name




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OrganizationalUnitNames ::= SEQUENCE SIZE (1..ub-organizational-units)
                         OF OrganizationalUnitName
-- see also teletex-organizational-unit-names

OrganizationalUnitName ::= PrintableString (SIZE
               (1..ub-organizational-unit-name-length))

--   Built-in Domain-defined Attributes

BuiltInDomainDefinedAttributes ::= SEQUENCE SIZE
                    (1..ub-domain-defined-attributes) OF
                    BuiltInDomainDefinedAttribute

BuiltInDomainDefinedAttribute ::= SEQUENCE {
   type PrintableString (SIZE
               (1..ub-domain-defined-attribute-type-length)),
   value PrintableString (SIZE
               (1..ub-domain-defined-attribute-value-length))}

--   Extension Attributes

ExtensionAttributes ::= SET SIZE (1..ub-extension-attributes) OF
               ExtensionAttribute

ExtensionAttribute ::=  SEQUENCE {
   extension-attribute-type [0] INTEGER (0..ub-extension-attributes),
   extension-attribute-value [1]
                        ANY DEFINED BY extension-attribute-type }

-- Extension types and attribute values
--

common-name INTEGER ::= 1

CommonName ::= PrintableString (SIZE (1..ub-common-name-length))

teletex-common-name INTEGER ::= 2

TeletexCommonName ::= TeletexString (SIZE (1..ub-common-name-length))

teletex-organization-name INTEGER ::= 3

TeletexOrganizationName ::=
                TeletexString (SIZE (1..ub-organization-name-length))

teletex-personal-name INTEGER ::= 4

TeletexPersonalName ::= SET {



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   surname [0] TeletexString (SIZE (1..ub-surname-length)),
   given-name [1] TeletexString
                (SIZE (1..ub-given-name-length)) OPTIONAL,
   initials [2] TeletexString (SIZE (1..ub-initials-length)) OPTIONAL,
   generation-qualifier [3] TeletexString (SIZE
                (1..ub-generation-qualifier-length)) OPTIONAL }

teletex-organizational-unit-names INTEGER ::= 5

TeletexOrganizationalUnitNames ::= SEQUENCE SIZE
     (1..ub-organizational-units) OF TeletexOrganizationalUnitName

TeletexOrganizationalUnitName ::= TeletexString
               (SIZE (1..ub-organizational-unit-name-length))

pds-name INTEGER ::= 7

PDSName ::= PrintableString (SIZE (1..ub-pds-name-length))

physical-delivery-country-name INTEGER ::= 8

PhysicalDeliveryCountryName ::= CHOICE {
   x121-dcc-code NumericString (SIZE (ub-country-name-numeric-length)),
   iso-3166-alpha2-code PrintableString
               (SIZE (ub-country-name-alpha-length)) }

postal-code INTEGER ::= 9

PostalCode ::= CHOICE {
   numeric-code NumericString (SIZE (1..ub-postal-code-length)),
   printable-code PrintableString (SIZE (1..ub-postal-code-length)) }

physical-delivery-office-name INTEGER ::= 10

PhysicalDeliveryOfficeName ::= PDSParameter

physical-delivery-office-number INTEGER ::= 11

PhysicalDeliveryOfficeNumber ::= PDSParameter

extension-OR-address-components INTEGER ::= 12

ExtensionORAddressComponents ::= PDSParameter

physical-delivery-personal-name INTEGER ::= 13

PhysicalDeliveryPersonalName ::= PDSParameter




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physical-delivery-organization-name INTEGER ::= 14

PhysicalDeliveryOrganizationName ::= PDSParameter

extension-physical-delivery-address-components INTEGER ::= 15

ExtensionPhysicalDeliveryAddressComponents ::= PDSParameter

unformatted-postal-address INTEGER ::= 16

UnformattedPostalAddress ::= SET {
   printable-address SEQUENCE SIZE (1..ub-pds-physical-address-lines) OF
        PrintableString (SIZE (1..ub-pds-parameter-length)) OPTIONAL,
   teletex-string TeletexString
         (SIZE (1..ub-unformatted-address-length)) OPTIONAL }

street-address INTEGER ::= 17

StreetAddress ::= PDSParameter

post-office-box-address INTEGER ::= 18

PostOfficeBoxAddress ::= PDSParameter

poste-restante-address INTEGER ::= 19

PosteRestanteAddress ::= PDSParameter

unique-postal-name INTEGER ::= 20

UniquePostalName ::= PDSParameter

local-postal-attributes INTEGER ::= 21

LocalPostalAttributes ::= PDSParameter

PDSParameter ::= SET {
   printable-string PrintableString
                (SIZE(1..ub-pds-parameter-length)) OPTIONAL,
   teletex-string TeletexString
                (SIZE(1..ub-pds-parameter-length)) OPTIONAL }

extended-network-address INTEGER ::= 22

ExtendedNetworkAddress ::= CHOICE {
   e163-4-address SEQUENCE {
     number [0] NumericString (SIZE (1..ub-e163-4-number-length)),
     sub-address [1] NumericString



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          (SIZE (1..ub-e163-4-sub-address-length)) OPTIONAL },
   psap-address [0] PresentationAddress }

PresentationAddress ::= SEQUENCE {
     pSelector [0] EXPLICIT OCTET STRING OPTIONAL,
     sSelector [1] EXPLICIT OCTET STRING OPTIONAL,
     tSelector [2] EXPLICIT OCTET STRING OPTIONAL,
     nAddresses     [3] EXPLICIT SET SIZE (1..MAX) OF OCTET STRING }

terminal-type  INTEGER ::= 23

TerminalType ::= INTEGER {
   telex (3),
   teletex (4),
   g3-facsimile (5),
   g4-facsimile (6),
   ia5-terminal (7),
   videotex (8) } (0..ub-integer-options)

--   Extension Domain-defined Attributes

teletex-domain-defined-attributes INTEGER ::= 6

TeletexDomainDefinedAttributes ::= SEQUENCE SIZE
   (1..ub-domain-defined-attributes) OF TeletexDomainDefinedAttribute

TeletexDomainDefinedAttribute ::= SEQUENCE {
        type TeletexString
            (SIZE (1..ub-domain-defined-attribute-type-length)),
        value TeletexString
            (SIZE (1..ub-domain-defined-attribute-value-length)) }

--  specifications of Upper Bounds MUST be regarded as mandatory
--  from Annex B of ITU-T X.411 Reference Definition of MTS Parameter
--  Upper Bounds

--   Upper Bounds
ub-name INTEGER ::= 32768
ub-common-name INTEGER ::= 64
ub-locality-name INTEGER ::= 128
ub-state-name INTEGER ::= 128
ub-organization-name INTEGER ::= 64
ub-organizational-unit-name INTEGER ::= 64
ub-title INTEGER ::= 64
ub-serial-number INTEGER ::= 64
ub-match INTEGER ::= 128
ub-emailaddress-length INTEGER ::= 128
ub-common-name-length INTEGER ::= 64



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ub-country-name-alpha-length INTEGER ::= 2
ub-country-name-numeric-length INTEGER ::= 3
ub-domain-defined-attributes INTEGER ::= 4
ub-domain-defined-attribute-type-length INTEGER ::= 8
ub-domain-defined-attribute-value-length INTEGER ::= 128
ub-domain-name-length INTEGER ::= 16
ub-extension-attributes INTEGER ::= 256
ub-e163-4-number-length INTEGER ::= 15
ub-e163-4-sub-address-length INTEGER ::= 40
ub-generation-qualifier-length INTEGER ::= 3
ub-given-name-length INTEGER ::= 16
ub-initials-length INTEGER ::= 5
ub-integer-options INTEGER ::= 256
ub-numeric-user-id-length INTEGER ::= 32
ub-organization-name-length INTEGER ::= 64
ub-organizational-unit-name-length INTEGER ::= 32
ub-organizational-units INTEGER ::= 4
ub-pds-name-length INTEGER ::= 16
ub-pds-parameter-length INTEGER ::= 30
ub-pds-physical-address-lines INTEGER ::= 6
ub-postal-code-length INTEGER ::= 16
ub-surname-length INTEGER ::= 40
ub-terminal-id-length INTEGER ::= 24
ub-unformatted-address-length INTEGER ::= 180
ub-x121-address-length INTEGER ::= 16

-- Note - upper bounds on string types, such as TeletexString, are
-- measured in characters.  Excepting PrintableString or IA5String, a
-- significantly greater number of octets will be required to hold
-- such a value.  As a minimum, 16 octets, or twice the specified upper
-- bound, whichever is the larger, should be allowed for TeletexString.
-- For UTF8String or UniversalString at least four times the upper
-- bound should be allowed.

END
















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A.2 Implicitly Tagged Module, 1988 Syntax

PKIX1Implicit88 {iso(1) identified-organization(3) dod(6) internet(1)
  security(5) mechanisms(5) pkix(7) id-mod(0) id-pkix1-implicit(19)}

DEFINITIONS IMPLICIT TAGS ::=

BEGIN

-- EXPORTS ALL --

IMPORTS
      id-pe, id-kp, id-qt-unotice, id-qt-cps, id-ad,
      -- delete following line if "new" types are supported --
      BMPString, UTF8String, -- end "new" types --
      ORAddress, Name, RelativeDistinguishedName,
      CertificateSerialNumber, Attribute, DirectoryString
      FROM PKIX1Explicit88 {iso(1) identified-organization(3)
            dod(6) internet(1) security(5) mechanisms(5) pkix(7)
            id-mod(0) id-pkix1-explicit(18)};


-- ISO arc for standard certificate and CRL extensions

id-ce OBJECT IDENTIFIER  ::=  {joint-iso-ccitt(2) ds(5) 29}

-- authority key identifier OID and syntax

id-ce-authorityKeyIdentifier OBJECT IDENTIFIER ::=  { id-ce 35 }

AuthorityKeyIdentifier ::= SEQUENCE {
      keyIdentifier             [0] KeyIdentifier            OPTIONAL,
      authorityCertIssuer       [1] GeneralNames             OPTIONAL,
      authorityCertSerialNumber [2] CertificateSerialNumber  OPTIONAL }
    -- authorityCertIssuer and authorityCertSerialNumber MUST both
    -- be present or both be absent

KeyIdentifier ::= OCTET STRING

-- subject key identifier OID and syntax

id-ce-subjectKeyIdentifier OBJECT IDENTIFIER ::=  { id-ce 14 }

SubjectKeyIdentifier ::= KeyIdentifier

-- key usage extension OID and syntax

id-ce-keyUsage OBJECT IDENTIFIER ::=  { id-ce 15 }



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KeyUsage ::= BIT STRING {
     digitalSignature        (0),
     nonRepudiation          (1),
     keyEncipherment         (2),
     dataEncipherment        (3),
     keyAgreement            (4),
     keyCertSign             (5),
     cRLSign                 (6),
     encipherOnly            (7),
     decipherOnly            (8) }

-- private key usage period extension OID and syntax

id-ce-privateKeyUsagePeriod OBJECT IDENTIFIER ::=  { id-ce 16 }

PrivateKeyUsagePeriod ::= SEQUENCE {
     notBefore       [0]     GeneralizedTime OPTIONAL,
     notAfter        [1]     GeneralizedTime OPTIONAL }
     -- either notBefore or notAfter MUST be present

-- certificate policies extension OID and syntax

id-ce-certificatePolicies OBJECT IDENTIFIER ::=  { id-ce 32 }

anyPolicy OBJECT IDENTIFIER ::= {id-ce-certificatePolicies 0}

CertificatePolicies ::= SEQUENCE SIZE (1..MAX) OF PolicyInformation

PolicyInformation ::= SEQUENCE {
     policyIdentifier   CertPolicyId,
     policyQualifiers   SEQUENCE SIZE (1..MAX) OF
             PolicyQualifierInfo OPTIONAL }

CertPolicyId ::= OBJECT IDENTIFIER

PolicyQualifierInfo ::= SEQUENCE {
       policyQualifierId  PolicyQualifierId,
       qualifier    ANY DEFINED BY policyQualifierId }

-- Implementations that recognize additional policy qualifiers MUST
-- augment the following definition for PolicyQualifierId

PolicyQualifierId ::=
    OBJECT IDENTIFIER ( id-qt-cps | id-qt-unotice )

-- CPS pointer qualifier

CPSuri ::= IA5String



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-- user notice qualifier

UserNotice ::= SEQUENCE {
     noticeRef        NoticeReference OPTIONAL,
     explicitText     DisplayText OPTIONAL}

NoticeReference ::= SEQUENCE {
     organization     DisplayText,
     noticeNumbers    SEQUENCE OF INTEGER }

DisplayText ::= CHOICE {
     ia5String        IA5String      (SIZE (1..200)),
     visibleString    VisibleString  (SIZE (1..200)),
     bmpString        BMPString      (SIZE (1..200)),
     utf8String       UTF8String     (SIZE (1..200)) }

-- policy mapping extension OID and syntax

id-ce-policyMappings OBJECT IDENTIFIER ::=  { id-ce 33 }

PolicyMappings ::= SEQUENCE SIZE (1..MAX) OF SEQUENCE {
     issuerDomainPolicy      CertPolicyId,
     subjectDomainPolicy     CertPolicyId }

-- subject alternative name extension OID and syntax

id-ce-subjectAltName OBJECT IDENTIFIER ::=  { id-ce 17 }

SubjectAltName ::= GeneralNames

GeneralNames ::= SEQUENCE SIZE (1..MAX) OF GeneralName

GeneralName ::= CHOICE {
     otherName                       [0]     AnotherName,
     rfc822Name                      [1]     IA5String,
     dNSName                         [2]     IA5String,
     x400Address                     [3]     ORAddress,
     directoryName                   [4]     Name,
     ediPartyName                    [5]     EDIPartyName,
     uniformResourceIdentifier       [6]     IA5String,
     iPAddress                       [7]     OCTET STRING,
     registeredID                    [8]     OBJECT IDENTIFIER }

-- AnotherName replaces OTHER-NAME ::= TYPE-IDENTIFIER, as
-- TYPE-IDENTIFIER is not supported in the '88 ASN.1 syntax

AnotherName ::= SEQUENCE {
     type-id   OBJECT IDENTIFIER,



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     value     [0] EXPLICIT ANY DEFINED BY type-id }

EDIPartyName ::= SEQUENCE {
     nameAssigner            [0]     DirectoryString OPTIONAL,
     partyName               [1]     DirectoryString }

-- issuer alternative name extension OID and syntax

id-ce-issuerAltName OBJECT IDENTIFIER ::=  { id-ce 18 }

IssuerAltName ::= GeneralNames

id-ce-subjectDirectoryAttributes OBJECT IDENTIFIER ::=  { id-ce 9 }

SubjectDirectoryAttributes ::= SEQUENCE SIZE (1..MAX) OF Attribute

-- basic constraints extension OID and syntax

id-ce-basicConstraints OBJECT IDENTIFIER ::=  { id-ce 19 }

BasicConstraints ::= SEQUENCE {
     cA                      BOOLEAN DEFAULT FALSE,
     pathLenConstraint       INTEGER (0..MAX) OPTIONAL }

-- name constraints extension OID and syntax

id-ce-nameConstraints OBJECT IDENTIFIER ::=  { id-ce 30 }

NameConstraints ::= SEQUENCE {
     permittedSubtrees       [0]     GeneralSubtrees OPTIONAL,
     excludedSubtrees        [1]     GeneralSubtrees OPTIONAL }

GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree

GeneralSubtree ::= SEQUENCE {
     base                    GeneralName,
     minimum         [0]     BaseDistance DEFAULT 0,
     maximum         [1]     BaseDistance OPTIONAL }

BaseDistance ::= INTEGER (0..MAX)

-- policy constraints extension OID and syntax

id-ce-policyConstraints OBJECT IDENTIFIER ::=  { id-ce 36 }

PolicyConstraints ::= SEQUENCE {
     requireExplicitPolicy           [0] SkipCerts OPTIONAL,
     inhibitPolicyMapping            [1] SkipCerts OPTIONAL }



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SkipCerts ::= INTEGER (0..MAX)

-- CRL distribution points extension OID and syntax

id-ce-cRLDistributionPoints   OBJECT IDENTIFIER  ::=   {id-ce 31}

CRLDistributionPoints ::= SEQUENCE SIZE (1..MAX) OF DistributionPoint

DistributionPoint ::= SEQUENCE {
     distributionPoint       [0]     DistributionPointName OPTIONAL,
     reasons                 [1]     ReasonFlags OPTIONAL,
     cRLIssuer               [2]     GeneralNames OPTIONAL }

DistributionPointName ::= CHOICE {
     fullName                [0]     GeneralNames,
     nameRelativeToCRLIssuer [1]     RelativeDistinguishedName }

ReasonFlags ::= BIT STRING {
     unused                  (0),
     keyCompromise           (1),
     cACompromise            (2),
     affiliationChanged      (3),
     superseded              (4),
     cessationOfOperation    (5),
     certificateHold         (6) }

-- extended key usage extension OID and syntax

id-ce-extKeyUsage OBJECT IDENTIFIER ::= {id-ce 37}

ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId

KeyPurposeId ::= OBJECT IDENTIFIER

-- extended key purpose OIDs
id-kp-serverAuth      OBJECT IDENTIFIER ::= { id-kp 1 }
id-kp-clientAuth      OBJECT IDENTIFIER ::= { id-kp 2 }
id-kp-codeSigning     OBJECT IDENTIFIER ::= { id-kp 3 }
id-kp-emailProtection OBJECT IDENTIFIER ::= { id-kp 4 }
id-kp-ipsecEndSystem  OBJECT IDENTIFIER ::= { id-kp 5 }
id-kp-ipsecTunnel     OBJECT IDENTIFIER ::= { id-kp 6 }
id-kp-ipsecUser       OBJECT IDENTIFIER ::= { id-kp 7 }
id-kp-timeStamping    OBJECT IDENTIFIER ::= { id-kp 8 }

-- inhibit any policy OID and syntax

id-ce-inhibitAnyPolicy OBJECT IDENTIFIER ::=  { id-ce 54 }




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InhibitAnyPolicy ::= SkipCerts

-- freshest (delta-)CRL extension OID and syntax

id-ce-freshestCRL OBJECT IDENTIFIER ::=  { id-ce 46 }

FreshestCRL ::= CRLDistributionPoints

-- authority info access

id-pe-authorityInfoAccess OBJECT IDENTIFIER ::= { id-pe 1 }

AuthorityInfoAccessSyntax  ::=
        SEQUENCE SIZE (1..MAX) OF AccessDescription

AccessDescription  ::=  SEQUENCE {
        accessMethod          OBJECT IDENTIFIER,
        accessLocation        GeneralName  }

-- CRL number extension OID and syntax

id-ce-cRLNumber OBJECT IDENTIFIER ::= { id-ce 20 }

CRLNumber ::= INTEGER (0..MAX)

-- issuing distribution point extension OID and syntax

id-ce-issuingDistributionPoint OBJECT IDENTIFIER ::= { id-ce 28 }

IssuingDistributionPoint ::= SEQUENCE {
     distributionPoint       [0] DistributionPointName OPTIONAL,
     onlyContainsUserCerts   [1] BOOLEAN DEFAULT FALSE,
     onlyContainsCACerts     [2] BOOLEAN DEFAULT FALSE,
     onlySomeReasons         [3] ReasonFlags OPTIONAL,
     indirectCRL             [4] BOOLEAN DEFAULT FALSE }

id-ce-deltaCRLIndicator OBJECT IDENTIFIER ::= { id-ce 27 }

BaseCRLNumber ::= CRLNumber

-- CRL reasons extension OID and syntax

id-ce-cRLReasons OBJECT IDENTIFIER ::= { id-ce 21 }

CRLReason ::= ENUMERATED {
     unspecified             (0),
     keyCompromise           (1),
     cACompromise            (2),



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     affiliationChanged      (3),
     superseded              (4),
     cessationOfOperation    (5),
     certificateHold         (6),
     removeFromCRL           (8) }

-- certificate issuer CRL entry extension OID and syntax

id-ce-certificateIssuer OBJECT IDENTIFIER ::= { id-ce 29 }

CertificateIssuer ::= GeneralNames

-- hold instruction extension OID and syntax

id-ce-holdInstructionCode OBJECT IDENTIFIER ::= { id-ce 23 }

HoldInstructionCode ::= OBJECT IDENTIFIER

-- ANSI x9 holdinstructions

-- ANSI x9 arc holdinstruction arc
holdInstruction OBJECT IDENTIFIER ::=
          {joint-iso-itu-t(2) member-body(2) us(840) x9cm(10040) 2}

-- ANSI X9 holdinstructions referenced by this standard
id-holdinstruction-none OBJECT IDENTIFIER  ::=
          {holdInstruction 1} -- deprecated
id-holdinstruction-callissuer OBJECT IDENTIFIER ::=
          {holdInstruction 2}
id-holdinstruction-reject OBJECT IDENTIFIER ::=
          {holdInstruction 3}

-- invalidity date CRL entry extension OID and syntax

id-ce-invalidityDate OBJECT IDENTIFIER ::= { id-ce 24 }

InvalidityDate ::=  GeneralizedTime

END












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Appendix B. ASN.1 Notes

   CAs MUST force the serialNumber to be a non-negative integer, that
   is, the sign bit in the DER encoding of the INTEGER value MUST be
   zero - this can be done by adding a leading (leftmost) `00'H octet if
   necessary. This removes a potential ambiguity in mapping between a
   string of octets and an integer value.

   As noted in section 4.1.2.2,  serial numbers can be expected to
   contain long integers. Certificate users MUST be able to handle
   serialNumber values up to 20 octets in length. Conformant CAs MUST
   NOT use serialNumber values longer than 20 octets.

   The construct "SEQUENCE SIZE (1..MAX) OF" appears in several ASN.1
   constructs. A valid ASN.1 sequence will have zero or more entries.
   The SIZE (1..MAX) construct constrains the sequence to have at least
   one entry. MAX indicates the upper bound is unspecified.
   Implementations are free to choose an upper bound that suits their
   environment.

   The construct "positiveInt ::= INTEGER (0..MAX)" defines positiveInt
   as a subtype of INTEGER containing integers greater than or equal to
   zero.  The upper bound is unspecified. Implementations are free to
   select an upper bound that suits their environment.

   The character string type PrintableString supports a very basic Latin
   character set: the lower case letters 'a' through 'z', upper case
   letters 'A' through 'Z', the digits '0' through '9', eleven special
   characters ' = ( ) + , - . / : ? and space.

   The character string type TeletexString is a superset of
   PrintableString.  TeletexString supports a fairly standard (ascii-
   like) Latin character set, Latin characters with non-spacing accents
   and Japanese characters.

   The character string type UniversalString supports any of the
   characters allowed by ISO 10646-1. ISO 10646 is the Universal
   multiple-octet coded Character Set (UCS).  ISO 10646-1 specifes the
   architecture and the "basic multilingual plane" - a large standard
   character set which includes all major world character standards.

   The character string type UTF8String was introduced in the 1997
   version of ASN.1, and UTF8String was added to the list of choices for
   DirectoryString in the 2001 version of X.520.  UTF8String is a
   universal type and has been assigned tag number 12.  The content of
   UTF8String was defined by RFC 2044 and updated in RFC 2279, "UTF-8, a
   transformation format of ISO 10646."




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   In anticipation of these changes, and in conformance with IETF Best
   Practices codified in RFC 2277, IETF Policy on Character Sets and
   Languages, this document includes UTF8String as a choice in
   DirectoryString and the CPS qualifier extensions.

   Implementers should note that the DER encoding of the SET OF values
   requires ordering of the encodings of the values. In particular, this
   issue arises with respect to distinguished names.

   Object Identifiers (OIDs) are used throught this specification to
   identify certificate policies, public key and signature algorithms,
   certificate extensions, etc.  There is no maximum size for OIDs.
   This specification mandates support for OIDs which have arc elements
   with values that are less than 2^28, i.e. they MUST be between 0 and
   268,435,455 inclusive. This allows each arc element to be represented
   within a single 32 bit word.  Implementations MUST also support OIDs
   where the length of the dotted decimal (see [LDAP], section 4.1.2)
   string representation can be up to 100 bytes (inclusive).
   Implementations MUST be able to handle OIDs with up to 20 elements
   (inclusive). CAs SHOULD NOT issue certificates which contain OIDs
   that breach these requirements.

Appendix C. Examples

   This section contains four examples: three certificates and a CRL.
   The first two certificates and the CRL comprise a minimal
   certification path.

   Section C.1 contains an annotated hex dump of a "self-signed"
   certificate issued by a CA whose distinguished name is
   cn=us,o=gov,ou=nist.  The certificate contains a DSA public key with
   parameters, and is signed by the corresponding DSA private key.

   Section C.2 contains an annotated hex dump of an end-entity
   certificate.  The end entity certificate contains a DSA public key,
   and is signed by the private key corresponding to the "self-signed"
   certificate in section C.1.

   Section C.3 contains a dump of an end entity certificate which
   contains an RSA public key and is signed with RSA and MD5.  This
   certificate is not part of the minimal certification path.

   Section C.4 contains an annotated hex dump of a CRL.  The CRL is
   issued by the CA whose distinguished name is cn=us,o=gov,ou=nist and
   the list of revoked certificates includes the end entity certificate
   presented in C.2.

   The certificates were processed using Peter Gutman's dumpasn1 utility



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   to generate the output.  The source for the dumpasn1 utility is
   available at <http://www.cs.auckland.ac.nz/~pgut001/dumpasn1.c>.  The
   binaries for the certificates and CRLs are available at
   <http://csrc.nist.gov/pki/pkixtools>.

C.1 Certificate

   This section contains an annotated hex dump of a 699 byte version 3
   certificate.  The certificate contains the following information:
   (a) the serial number is 23 (17 hex);
   (b) the certificate is signed with DSA and the SHA-1 hash algorithm;
   (c) the issuer's distinguished name is OU=NIST; O=gov; C=US
   (d) and the subject's distinguished name is OU=NIST; O=gov; C=US
   (e) the certificate was issued on June 30, 1997 and will expire on
   December 31, 1997;
   (f) the certificate contains a 1024 bit DSA public key with
   parameters;
   (g) the certificate contains a subject key identifier extension; and
   (h) the certificate is a CA certificate (as indicated through the
   basic constraints extension.)


   0 30  701: SEQUENCE {
   4 30  637:   SEQUENCE {
   8 A0    3:     [0] {
  10 02    1:       INTEGER 2
            :       }
  13 02    1:     INTEGER 23
  16 30    9:     SEQUENCE {
  18 06    7:       OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3)
            :       }
  27 30   42:     SEQUENCE {
  29 31   11:       SET {
  31 30    9:         SEQUENCE {
  33 06    3:           OBJECT IDENTIFIER countryName (2 5 4 6)
  38 13    2:           PrintableString 'US'
            :           }
            :         }
  42 31   12:       SET {
  44 30   10:         SEQUENCE {
  46 06    3:           OBJECT IDENTIFIER organizationName (2 5 4 10)
  51 13    3:           PrintableString 'gov'
            :           }
            :         }
  56 31   13:       SET {
  58 30   11:         SEQUENCE {
  60 06    3:           OBJECT IDENTIFIER
                               organizationalUnitName (2 5 4 11)



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  65 13    4:           PrintableString 'NIST'
            :           }
            :         }
            :       }
  71 30   30:     SEQUENCE {
  73 17   13:       UTCTime '970630000000Z'
  88 17   13:       UTCTime '971231000000Z'
            :       }
 103 30   42:     SEQUENCE {
 105 31   11:       SET {
 107 30    9:         SEQUENCE {
 109 06    3:           OBJECT IDENTIFIER countryName (2 5 4 6)
 114 13    2:           PrintableString 'US'
            :           }
            :         }
 118 31   12:       SET {
 120 30   10:         SEQUENCE {
 122 06    3:           OBJECT IDENTIFIER organizationName (2 5 4 10)
 127 13    3:           PrintableString 'gov'
            :           }
            :         }
 132 31   13:       SET {
 134 30   11:         SEQUENCE {
 136 06    3:           OBJECT IDENTIFIER
                               organizationalUnitName (2 5 4 11)
 141 13    4:           PrintableString 'NIST'
            :           }
            :         }
            :       }
 147 30  440:     SEQUENCE {
 151 30  300:       SEQUENCE {
 155 06    7:         OBJECT IDENTIFIER dsa (1 2 840 10040 4 1)
 164 30  287:         SEQUENCE {
 168 02  129:           INTEGER
            :            00 B6 8B 0F 94 2B 9A CE A5 25 C6 F2 ED FC FB 95
            :            32 AC 01 12 33 B9 E0 1C AD 90 9B BC 48 54 9E F3
            :            94 77 3C 2C 71 35 55 E6 FE 4F 22 CB D5 D8 3E 89
            :            93 33 4D FC BD 4F 41 64 3E A2 98 70 EC 31 B4 50
            :            DE EB F1 98 28 0A C9 3E 44 B3 FD 22 97 96 83 D0
            :            18 A3 E3 BD 35 5B FF EE A3 21 72 6A 7B 96 DA B9
            :            3F 1E 5A 90 AF 24 D6 20 F0 0D 21 A7 D4 02 B9 1A
            :            FC AC 21 FB 9E 94 9E 4B 42 45 9E 6A B2 48 63 FE
            :            43
 300 02   21:           INTEGER
            :            00 B2 0D B0 B1 01 DF 0C 66 24 FC 13 92 BA 55 F7
            :            7D 57 74 81 E5
 323 02  129:           INTEGER
            :            00 9A BF 46 B1 F5 3F 44 3D C9 A5 65 FB 91 C0 8E



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            :            47 F1 0A C3 01 47 C2 44 42 36 A9 92 81 DE 57 C5
            :            E0 68 86 58 00 7B 1F F9 9B 77 A1 C5 10 A5 80 91
            :            78 51 51 3C F6 FC FC CC 46 C6 81 78 92 84 3D F4
            :            93 3D 0C 38 7E 1A 5B 99 4E AB 14 64 F6 0C 21 22
            :            4E 28 08 9C 92 B9 66 9F 40 E8 95 F6 D5 31 2A EF
            :            39 A2 62 C7 B2 6D 9E 58 C4 3A A8 11 81 84 6D AF
            :            F8 B4 19 B4 C2 11 AE D0 22 3B AA 20 7F EE 1E 57
            :            18
            :           }
            :         }
 455 03  133:       BIT STRING 0 unused bits
            :         02 81 81 00 B5 9E 1F 49 04 47 D1 DB F5 3A DD CA
            :         04 75 E8 DD 75 F6 9B 8A B1 97 D6 59 69 82 D3 03
            :         4D FD 3B 36 5F 4A F2 D1 4E C1 07 F5 D1 2A D3 78
            :         77 63 56 EA 96 61 4D 42 0B 7A 1D FB AB 91 A4 CE
            :         DE EF 77 C8 E5 EF 20 AE A6 28 48 AF BE 69 C3 6A
            :         A5 30 F2 C2 B9 D9 82 2B 7D D9 C4 84 1F DE 0D E8
            :         54 D7 1B 99 2E B3 D0 88 F6 D6 63 9B A7 E2 0E 82
            :         D4 3B 8A 68 1B 06 56 31 59 0B 49 EB 99 A5 D5 81
            :         41 7B C9 55
            :       }
 591 A3   52:     [3] {
 593 30   50:       SEQUENCE {
 595 30   31:         SEQUENCE {
 597 06    3:           OBJECT IDENTIFIER
                               subjectKeyIdentifier (2 5 29 14)
 602 04   24:           OCTET STRING
            :            04 16 04 14 E7 26 C5 54 CD 5B A3 6F 35 68 95 AA
            :            D5 FF 1C 21 E4 22 75 D6
            :           }
 628 30   15:         SEQUENCE {
 630 06    3:           OBJECT IDENTIFIER basicConstraints (2 5 29 19)
 635 01    1:           BOOLEAN TRUE
 638 04    5:           OCTET STRING
            :             30 03 01 01 FF
            :           }
            :         }
            :       }
            :     }
 645 30    9:   SEQUENCE {
 647 06    7:     OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3)
            :     }
 656 03   47:   BIT STRING 0 unused bits
            :     30 2C 02 14 6A F9 3F 72 30 7F 45 DC E5 50 C1 5E
            :     94 A0 6D C7 92 4C E5 E1 02 14 6F 61 B8 65 F7 AA
            :     DF 46 1B F7 39 0D 0D 88 9E FE B6 83 F7 1A
            :   }




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C.2 Certificate

   This section contains an annotated hex dump of a 730 byte version 3
   certificate.  The certificate contains the following information:
   (a) the serial number is 18 (12 hex);
   (b) the certificate is signed with DSA and the SHA-1 hash algorithm;
   (c) the issuer's distinguished name is OU=nist; O=gov; C=US
   (d) and the subject's distinguished name is CN=Tim Polk; OU=nist;
   O=gov; C=US
   (e) the certificate was valid from July 30, 1997 through December 1,
   1997;
   (f) the certificate contains a 1024 bit DSA public key;
   (g) the certificate is an end entity certificate, as the basic
   constraints extension is not present;
   (h) the certificate contains an authority key identifier extension;
   and
   (i) the certificate includes one alternative name - an RFC 822
   address.

   0 30  734: SEQUENCE {
   4 30  669:   SEQUENCE {
   8 A0    3:     [0] {
  10 02    1:       INTEGER 2
            :       }
  13 02    1:     INTEGER 18
  16 30    9:     SEQUENCE {
  18 06    7:       OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3)
            :       }
  27 30   42:     SEQUENCE {
  29 31   11:       SET {
  31 30    9:         SEQUENCE {
  33 06    3:           OBJECT IDENTIFIER countryName (2 5 4 6)
  38 13    2:           PrintableString 'US'
            :           }
            :         }
  42 31   12:       SET {
  44 30   10:         SEQUENCE {
  46 06    3:           OBJECT IDENTIFIER organizationName (2 5 4 10)
  51 13    3:           PrintableString 'gov'
            :           }
            :         }
  56 31   13:       SET {
  58 30   11:         SEQUENCE {
  60 06    3:           OBJECT IDENTIFIER
                               organizationalUnitName (2 5 4 11)
  65 13    4:           PrintableString 'NIST'
            :           }
            :         }



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            :       }
  71 30   30:     SEQUENCE {
  73 17   13:       UTCTime '970730000000Z'
  88 17   13:       UTCTime '971201000000Z'
            :       }
 103 30   61:     SEQUENCE {
 105 31   11:       SET {
 107 30    9:         SEQUENCE {
 109 06    3:           OBJECT IDENTIFIER countryName (2 5 4 6)
 114 13    2:           PrintableString 'US'
            :           }
            :         }
 118 31   12:       SET {
 120 30   10:         SEQUENCE {
 122 06    3:           OBJECT IDENTIFIER organizationName (2 5 4 10)
 127 13    3:           PrintableString 'gov'
            :           }
            :         }
 132 31   13:       SET {
 134 30   11:         SEQUENCE {
 136 06    3:           OBJECT IDENTIFIER
                               organizationalUnitName (2 5 4 11)
 141 13    4:           PrintableString 'NIST'
            :           }
            :         }
 147 31   17:       SET {
 149 30   15:         SEQUENCE {
 151 06    3:           OBJECT IDENTIFIER commonName (2 5 4 3)
 156 13    8:           PrintableString 'Tim Polk'
            :           }
            :         }
            :       }
 166 30  439:     SEQUENCE {
 170 30  300:       SEQUENCE {
 174 06    7:         OBJECT IDENTIFIER dsa (1 2 840 10040 4 1)
 183 30  287:         SEQUENCE {
 187 02  129:           INTEGER
            :            00 B6 8B 0F 94 2B 9A CE A5 25 C6 F2 ED FC FB 95
            :            32 AC 01 12 33 B9 E0 1C AD 90 9B BC 48 54 9E F3
            :            94 77 3C 2C 71 35 55 E6 FE 4F 22 CB D5 D8 3E 89
            :            93 33 4D FC BD 4F 41 64 3E A2 98 70 EC 31 B4 50
            :            DE EB F1 98 28 0A C9 3E 44 B3 FD 22 97 96 83 D0
            :            18 A3 E3 BD 35 5B FF EE A3 21 72 6A 7B 96 DA B9
            :            3F 1E 5A 90 AF 24 D6 20 F0 0D 21 A7 D4 02 B9 1A
            :            FC AC 21 FB 9E 94 9E 4B 42 45 9E 6A B2 48 63 FE
            :            43
 319 02   21:           INTEGER
            :            00 B2 0D B0 B1 01 DF 0C 66 24 FC 13 92 BA 55 F7



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            :            7D 57 74 81 E5
 342 02  129:           INTEGER
            :            00 9A BF 46 B1 F5 3F 44 3D C9 A5 65 FB 91 C0 8E
            :            47 F1 0A C3 01 47 C2 44 42 36 A9 92 81 DE 57 C5
            :            E0 68 86 58 00 7B 1F F9 9B 77 A1 C5 10 A5 80 91
            :            78 51 51 3C F6 FC FC CC 46 C6 81 78 92 84 3D F4
            :            93 3D 0C 38 7E 1A 5B 99 4E AB 14 64 F6 0C 21 22
            :            4E 28 08 9C 92 B9 66 9F 40 E8 95 F6 D5 31 2A EF
            :            39 A2 62 C7 B2 6D 9E 58 C4 3A A8 11 81 84 6D AF
            :            F8 B4 19 B4 C2 11 AE D0 22 3B AA 20 7F EE 1E 57
            :            18
            :           }
            :         }
 474 03  132:       BIT STRING 0 unused bits
            :         02 81 80 30 B6 75 F7 7C 20 31 AE 38 BB 7E 0D 2B
            :         AB A0 9C 4B DF 20 D5 24 13 3C CD 98 E5 5F 6C B7
            :         C1 BA 4A BA A9 95 80 53 F0 0D 72 DC 33 37 F4 01
            :         0B F5 04 1F 9D 2E 1F 62 D8 84 3A 9B 25 09 5A 2D
            :         C8 46 8E 2B D4 F5 0D 3B C7 2D C6 6C B9 98 C1 25
            :         3A 44 4E 8E CA 95 61 35 7C CE 15 31 5C 23 13 1E
            :         A2 05 D1 7A 24 1C CB D3 72 09 90 FF 9B 9D 28 C0
            :         A1 0A EC 46 9F 0D B8 D0 DC D0 18 A6 2B 5E F9 8F
            :         B5 95 BE
            :       }
 609 A3   66:     [3] {
 611 30   64:       SEQUENCE {
 613 30   25:         SEQUENCE {
 615 06    3:           OBJECT IDENTIFIER subjectAltName (2 5 29 17)
 620 04   18:           OCTET STRING
            :            30 10 81 0E 77 70 6F 6C 6B 40 6E 69 73 74 2E 67
            :            6F 76
            :           }
 640 30   35:         SEQUENCE {
 642 06    3:           OBJECT IDENTIFIER
                               authorityKeyIdentifier (2 5 29 35)
 647 04   28:           OCTET STRING
            :            30 1A 80 18 04 16 04 14 E7 26 C5 54 CD 5B A3 6F
            :            35 68 95 AA D5 FF 1C 21 E4 22 75 D6
            :           }
            :         }
            :       }
            :     }
 677 30    9:   SEQUENCE {
 679 06    7:     OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3)
            :     }
 688 03   48:   BIT STRING 0 unused bits
            :     30 2D 02 14 37 FC 44 BF 7F 8D 18 1F 40 04 2F CF
            :     EA CC 22 B2 16 01 FF 13 02 15 00 97 D0 24 96 0F



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            :     64 8A C3 8D 41 B2 0E B9 26 D5 31 D1 A0 F1 BC
            :   }

C.3 End-Entity Certificate Using RSA

   This section contains an annotated hex dump of a 675 byte version 3
   certificate.  The certificate contains the following information:
   (a) the serial number is 256;
   (b) the certificate is signed with RSA and the MD2 hash algorithm;
   (c) the issuer's distinguished name is OU=Dept. Arquitectura de
   Computadors; O=Universitat Politecnica de Catalunya; C=ES
   (d) and the subject's distinguished name is CN=Francisco Jordan;
   OU=Dept. Arquitectura de Computadors; O=Universitat Politecnica de
   Catalunya; C=ES
   (e) the certificate was issued on May 21, 1996 and expired on May 21,
   1997;
   (f) the certificate contains a 768 bit RSA public key;
   (g) the certificate is an end entity certificate (not a CA
   certificate);
   (h) the certificate includes an alternative subject name and an
   alternative issuer name - bothe are URLs;
   (i) the certificate include an authority key identifier and
   certificate policies extensions; and
   (j) the certificate includes a critical key usage extension
   specifying the public is intended for generation of digital
   signatures.

   0 30  654: SEQUENCE {
   4 30  503:   SEQUENCE {
   8 A0    3:     [0] {
  10 02    1:       INTEGER 2
            :       }
  13 02    2:     INTEGER 256
  17 30   13:     SEQUENCE {
  19 06    9:       OBJECT IDENTIFIER
            :         sha1withRSAEncryption (1 2 840 113549 1 1 5)
  30 05    0:       NULL
            :       }
  32 30   42:     SEQUENCE {
  34 31   11:       SET {
  36 30    9:         SEQUENCE {
  38 06    3:           OBJECT IDENTIFIER countryName (2 5 4 6)
  43 13    2:           PrintableString 'US'
            :           }
            :         }
  47 31   12:       SET {
  49 30   10:         SEQUENCE {
  51 06    3:           OBJECT IDENTIFIER



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                               organizationalUnitName (2 5 4 11)
  56 13    3:           PrintableString 'gov'
            :           }
            :         }
  61 31   13:       SET {
  63 30   11:         SEQUENCE {
  65 06    3:           OBJECT IDENTIFIER organizationName (2 5 4 10)
  70 13    4:           PrintableString 'NIST'
            :           }
            :         }
            :       }
  76 30   30:     SEQUENCE {
  78 17   13:       UTCTime '960521095826Z'
  93 17   13:       UTCTime '970521095826Z'
            :       }
 108 30   61:     SEQUENCE {
 110 31   11:       SET {
 112 30    9:         SEQUENCE {
 114 06    3:           OBJECT IDENTIFIER countryName (2 5 4 6)
 119 13    2:           PrintableString 'US'
            :           }
            :         }
 123 31   12:       SET {
 125 30   10:         SEQUENCE {
 127 06    3:           OBJECT IDENTIFIER
                               organizationalUnitName (2 5 4 11)
 132 13    3:           PrintableString 'gov'
            :           }
            :         }
 137 31   13:       SET {
 139 30   11:         SEQUENCE {
 141 06    3:           OBJECT IDENTIFIER organizationName (2 5 4 10)
 146 13    4:           PrintableString 'NIST'
            :           }
            :         }
 152 31   17:       SET {
 154 30   15:         SEQUENCE {
 156 06    3:           OBJECT IDENTIFIER commonName (2 5 4 3)
 161 13    8:           PrintableString 'Tim Polk'
            :           }
            :         }
            :       }
 171 30  159:     SEQUENCE {
 174 30   13:       SEQUENCE {
 176 06    9:         OBJECT IDENTIFIER
                             rsaEncryption (1 2 840 113549 1 1 1)
 187 05    0:         NULL
            :         }



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 189 03  141:       BIT STRING 0 unused bits
            :         30 81 89 02 81 81 00 E1 CE 06 C9 D7 00 DF 65 27
            :         45 1E 63 6A 09 A0 A0 10 4B AF DF 9D 36 1D 44 1F
            :         B7 07 5D 36 92 09 6A 1A 96 C7 4E D9 86 0D 0F 77
            :         94 F5 82 62 68 9A F2 D7 76 F5 9A 35 C7 B3 7F 4F
            :         BE 64 CF A3 0C B3 84 32 80 F5 CA 77 29 C9 76 0B
            :         4C 38 19 EE 61 6F BA 68 E0 03 85 46 34 AB 84 64
            :         7F 43 69 02 C0 20 86 BD B1 D4 AD 21 A9 1A 8F CF
            :         96 83 86 92 57 5B 43 09 28 4C F2 5A 04 AD E5 DE
            :         9E 4F E8 38 3C F0 89 02 03 01 00 01
            :       }
 333 A3  175:     [3] {
 336 30  172:       SEQUENCE {
 339 30   63:         SEQUENCE {
 341 06    3:           OBJECT IDENTIFIER subjectAltName (2 5 29 17)
 346 04   56:           OCTET STRING
            :            30 36 86 34 68 74 74 70 3A 2F 2F 77 77 77 2E 69
            :            74 6C 2E 6E 69 73 74 2E 67 6F 76 2F 64 69 76 38
            :            39 33 2F 73 74 61 66 66 2F 70 6F 6C 6B 2F 69 6E
            :            64 65 78 2E 68 74 6D 6C
            :           }
 404 30   31:         SEQUENCE {
 406 06    3:           OBJECT IDENTIFIER issuerAltName (2 5 29 18)
 411 04   24:           OCTET STRING
            :            30 16 86 14 68 74 74 70 3A 2F 2F 77 77 77 2E 6E
            :            69 73 74 2E 67 6F 76 2F
            :           }
 437 30   31:         SEQUENCE {
 439 06    3:           OBJECT IDENTIFIER
                               authorityKeyIdentifier (2 5 29 35)
 444 04   24:           OCTET STRING
            :            30 16 80 14 30 12 80 10 0E 6B 3A BF 04 EA 04 C3
            :            0E 6B 3A BF 04 EA 04 C3
            :           }
 470 30   23:         SEQUENCE {
 472 06    3:           OBJECT IDENTIFIER
                               certificatePolicies (2 5 29 32)
 477 04   16:           OCTET STRING
            :            30 0E 30 0C 06 0A 60 86 48 01 65 03 02 01 30 09
            :           }
 495 30   14:         SEQUENCE {
 497 06    3:           OBJECT IDENTIFIER keyUsage (2 5 29 15)
 502 01    1:           BOOLEAN TRUE
 505 04    4:           OCTET STRING
            :            03 02 07 80
            :           }
            :         }
            :       }



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            :     }
 511 30   13:   SEQUENCE {
 513 06    9:     OBJECT IDENTIFIER
            :       sha1withRSAEncryption (1 2 840 113549 1 1 5)
 524 05    0:     NULL
            :     }
 526 03  129:   BIT STRING 0 unused bits
            :     C1 25 6F AB 72 C0 5D DA E4 2F D5 E1 B0 25 D8 B4
            :     F1 82 95 D6 0D A5 4E 4F A1 23 E1 13 A4 9C 3D C5
            :     7F FD 05 EC 75 06 30 66 97 75 A6 5D 8F 97 BA B4
            :     EC A9 43 19 8D B7 54 FD E9 AD 43 B8 3C 8B D3 9E
            :     C7 C7 27 E3 1A AD D3 79 AC 65 5A 52 78 C4 D0 43
            :     81 50 F7 8A BA E2 30 1A 6D D0 78 A0 4E AE 2E 79
            :     37 0C 93 05 5C D1 9C 1B B2 62 73 D1 EA 50 B7 84
            :     29 92 74 34 CF BA AA 2C 4D 43 59 EF 98 0C 41 6C
            :   }

C.4 Certificate Revocation List

   This section contains an annotated hex dump of a version 2 CRL with
   one extension (cRLNumber). The CRL was issued by OU=nist;O=gov;C=us
   on July 7, 1996; the next scheduled issuance was August 7, 1996.  The
   CRL includes one revoked certificates: serial number 18 (12 hex).
   The CRL itself is number 18, and it was signed with DSA and SHA-1.

   0 30  203: SEQUENCE {
   3 30  140:   SEQUENCE {
   6 02    1:     INTEGER 1
   9 30    9:     SEQUENCE {
  11 06    7:       OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3)
            :       }
  20 30   42:     SEQUENCE {
  22 31   11:       SET {
  24 30    9:         SEQUENCE {
  26 06    3:           OBJECT IDENTIFIER countryName (2 5 4 6)
  31 13    2:           PrintableString 'US'
            :           }
            :         }
  35 31   12:       SET {
  37 30   10:         SEQUENCE {
  39 06    3:           OBJECT IDENTIFIER organizationName (2 5 4 10)
  44 13    3:           PrintableString 'gov'
            :           }
            :         }
  49 31   13:       SET {
  51 30   11:         SEQUENCE {
  53 06    3:           OBJECT IDENTIFIER
                               organizationalUnitName (2 5 4 11)



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  58 13    4:           PrintableString 'NIST'
            :           }
            :         }
            :       }
  64 17   13:     UTCTime '970807000000Z'
  79 17   13:     UTCTime '970907000000Z'
  94 30   34:     SEQUENCE {
  96 30   32:       SEQUENCE {
  98 02    1:         INTEGER 18
 101 17   13:         UTCTime '970731000000Z'
 116 30   12:         SEQUENCE {
 118 30   10:           SEQUENCE {
 120 06    3:             OBJECT IDENTIFIER cRLReason (2 5 29 21)
 125 04    3:             OCTET STRING
            :               0A 01 01
            :             }
            :           }
            :         }
            :       }
 130 A0   14:     [0] {
 132 30   12:       SEQUENCE {
 134 30   10:         SEQUENCE {
 136 06    3:           OBJECT IDENTIFIER cRLNumber (2 5 29 20)
 141 04    3:           OCTET STRING
            :             02 01 12
            :           }
            :         }
            :       }
            :     }
 146 30    9:   SEQUENCE {
 148 06    7:     OBJECT IDENTIFIER dsaWithSha1 (1 2 840 10040 4 3)
            :     }
 157 03   47:   BIT STRING 0 unused bits
            :     30 2C 02 14 79 1F F6 93 0B 84 06 D6 A0 7C 8D 68
            :     A7 52 2E 5F 3F 89 9B 4B 02 14 66 D4 B5 2A 68 36
            :     9B 72 88 58 E3 89 19 AD 81 89 2E 96 BB CC
            :   }














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Appendix D. Author Addresses:

   Russell Housley
   RSA Laboratories
   918 Spring Knoll Drive
   Herndon, VA 20170
   USA
   rhousley@rsasecurity.com

   Warwick Ford
   VeriSign, Inc.
   One Alewife Center
   Cambridge, MA 02140
   USA
   wford@verisign.com

   Tim Polk
   NIST
   Building 820, Room 426
   Gaithersburg, MD 20899
   USA
   wpolk@nist.gov

   David Solo
   Citigroup
   909 Third Ave, 16th Floor
   New York, NY 10043
   USA
   dsolo@alum.mit.edu

Appendix E.  Full Copyright Statement

   Copyright (C) The Internet Society (date). All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  In addition, the
   ASN.1 modules presented in Appendices A and B may be used in whole or
   in part without inclusion of the copyright notice.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process shall be
   followed, or as required to translate it into languages other than



Housley, Ford, Polk, & Solo                                   [Page 118]


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   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns. This
   document and the information contained herein is provided on an "AS
   IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK
   FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
   LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL
   NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY
   OR FITNESS FOR A PARTICULAR PURPOSE.









































Housley, Ford, Polk, & Solo                                   [Page 119]