PKIX Working Group                                      D. Pinkas (Bull)
INTERNET-DRAFT                                           T. Gindin (IBM)
Expires: December 2002                                         June 2002
Target category: Standard Track



                 Internet X.509 Public Key Infrastructure

                          Permanent Identifier

                       <draft-ietf-pkix-pi-05.txt>


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of [RFC 2026].

   Internet-Drafts are working documents of the Internet Engineering
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   Copyright (C) The Internet Society (2002). All Rights Reserved.

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

Abstract

   This document define a new form of name, called permanent
   identifier, that may be included in the subjectAltName extension
   of a public key certificate issued to an entity.

   The permanent identifier is an optional feature that may be used
   by a CA to indicate that the certificate relates to the same
   entity even if the name or the affiliation of that entity stored
   in the subject or another name form in the subjectAltName extension
   has changed.

   The subject name, carried in the subject field, is only unique
   for each subject entity certified by the one CA as defined by the
   issuer name field. Also, the new name form can carry a
   name that is unique for each subject entity certified by a CA.

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  Introduction

   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.

   This specification is one part of a family of standards for the
   X.509 Public Key Infrastructure (PKI) for the Internet. It is based
   on RFC 3280, which defines underlying certificate formats and
   semantics needed for a full implementation of this standard.

   The subject field of a public key certificate identifies the entity
   associated with the public key stored in the subject public key
   field. Names and identities of a subject may be carried in the
   subject field and/or the subjectAltName extension. Where subject
   field is non-empty, it MUST contain an X.500 distinguished
   name (DN). The DN MUST be unique for each subject entity certified
   by a single CA as defined by the issuer name field.

   The subject name changes whenever any of the components of that
   name gets changed. There are several reasons for such a change to
   happen.

         For employees of a company or organization, the person may get
         a different position within the same company and thus will
         move from one organization unit to another one. Including the
         organization unit in the name may however be very useful to
         allow the relying parties (RP's) using that certificate to
         identify the right individual.

         For citizens, an individual may change their name by legal
         processes, especially women as a result of marriage.

         Any certificate subject identified by geographical location may
         relocate and change at least some of the location attributes
         (e.g. country name, state or province, locality, or street).

   A permanent identifier may be useful in three contexts: access
   control, non-repudiation and audit records.

         For access control, the permanent identifier may be used in
         an ACL (Access Control List) instead of the DN or any other
         form of name and would not need to be changed, even if the
         subject name of the entity changes.

         For non-repudiation, the permanent identifier may be used to
         link different transactions to the same entity, even when
         the subject name of the entity changes.

         For audit records, the permanent identifier may be used to
         link different audit records to the same entity, even when
         the subject name of the entity changes.



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   When two certificates from different CA's contain both the same
   permanent identifier value and the same type of permanent
   identifier from a given Assigner Authority, then these
   certificates relate to the same entity, whatever the content of
   the DN or other subjectAltName components may be.

. Definition of a Permanent Identifier

   A CA which includes a permanent identifier in a certificate is
   certifying that any public key certificate containing that
   identifier refers to the same entity, whatever the content of
   the DN or other subjectAltName components may be.

   The use of a permanent identifier is OPTIONAL. This name is
   defined as a form of otherName from the GeneralName structure in
   SubjectAltName. The permanent identifier is defined as follows:

   id-on-permanentIdentifier   OBJECT IDENTIFIER ::= { id-on 3 }

     PermanentIdentifier ::=     SEQUENCE {
        identifierValue              IdentifierValue,
        identifierType               IdentifierType OPTIONAL,
        matchingRule        [0]      IMPLICIT OBJECT IDENTIFIER OPTIONAL
     }

     IdentifierValue ::= CHOICE {
            iA5String            IA5String,
            uTF8String           UTF8String
     }

     IdentifierType ::= CHOICE {
            registeredOID                   OBJECT IDENTIFIER,
            uri                             IA5String
     }

   The IdentifierValue supports two syntaxes: IA5String or UTF8String.
   IA5String is variable length data of ASCII octets. UTF8String is
   variable length data of octets. UTF-8 is an ASCII-preserving
   encoding method for Unicode (ISO 10646), the Universal Character Set
   (UCS). The UCS allows to support most of the world's writing systems
   using a single character set.

   The IdentifierType field, when present, identifies both the
   organization responsible for assigning the content of the identifier
   field and the type of that field.

   When the IdentifierType field is missing, then it is assumed that
   the organization responsible for assigning the content of the
   identifier field is the CA itself and that there is only one type
   of such identifier for the CA.





Pinkas, Gindin                                                 [ Page 3]


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   The IdentifierType field may contain either:

           a) an Object Identifier (i.e. an OID), or
           b) a permanent URI using IA5String.

   Characteristically, when an OID is used, the prefix of the OID
   identifies the organization, and a suffix is used to identify the
   type of permanent identifier being identified. Essentially the
   same thing is true of URI's.

   Note: the full arc of the object identifier used to identify the
   permanent identifier name form is derived using:

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

     id-on OBJECT IDENTIFIER ::= { id-pkix 8 }   -- other name forms

   If identifierType is missing, then the permanent identifier is
   locally unique to the CA.

   If identifierType is present, then the permanent identifier is
   globally unique among all CAs.

   The matchingRule is an OID. When the OID is missing the
   following matching rule SHALL be used:

      The Alphanumeric Identifier Match rule compares for equality a
      presented value with an attribute value of type UTF8String
      or IA5String, which is interpreted as a series of alphanumeric
      characters.  The rules for matching are that a working comparison
      value is constructed from each of the two values by including
      only the digits and alphabetic characters appearing in the value;
      and then the two comparison values are compared using
      CaseIgnoreMatch.  This rule is intended for use only with
      identifiers in variants of the Latin, Greek, and Cyrillic scripts.

   Note: other matching rules can be used (see in chapter 6 of X.520).
   Two such examples are:

     caseIgnoreMatch {2 5 13 2} defined in section 6.1.1 of X.520, and
     caseExactMatch  {2 5 13 5} defined in section 6.1.4 of X.520.

. Security considerations

   A given entity may have at an instant of time or at different
   instants of time multiple forms of identities.

   If the permanent identifier is locally unique to the CA (i.e.
   identifierType is not present), then two certificates from the
   same CA can be compared. When they contain two identical permanent
   identifiers, then a relying party may determine that they refer to
   the same entity.


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   If the permanent identifier is globally unique among all CAs (i.e.
   identifierType is present), then two certificates from different
   CAs can be compared. When they contain two identical permanent
   identifiers, then a relying party may determine that they refer to
   the same entity.

   The permanent identifier identifies the entity, irrespective of any
   attribute extension. When a public key certificate contains
   attribute extensions, the permanent identifier, if present, should
   not be used for access control purposes but only for audit purposes.
   The reason is that since these attributes may change, access could
   be granted on attributes that were originally present in a
   certificate issued to that entity but are no more present in the
   current certificate.

   The content and the format of the IdentifierValue is defined by the
   Assigner Authority. An Assigner Authority who wishes to permit
   IdentifierValues to be matched using a matching rule different from
   the one specified in this document would be required to specify a
   matching rule. Many such matching rules are specified in ITU-T X.520.

   Subject names in certificates are chosen by the issuing CA and are
   mandated to be unique for each CA; so there can be no name collision
   between subject names from the same CA. These names may be an
   end-entity name, when the certificate is a leaf certificate or a
   CA name, when it is a CA certificate.

   Since a name is only unique towards its superior CA, unless some
   naming constraints are being used, a name would only be guaranteed
   to be globally unique when considered to include a sequence of all
   the names of the superior CAs.  Thus, two certificates which contain
   a permanent identifier extension without a identifierType may have
   their permanent identifier extensions compared for equality either
   by comparing the public key values of the two CAs which have issued
   these two certificates or by comparing the sequence of CA names in
   the certification path from the trust anchor to the CA, inclusive.

   The certification of different CAs with the same DN by different
   CAs has other negative consequences in various parts of the PKI,
   notably rendering the IssuerAndSerialNumber structure in RFC 2630
   section 5.3 ambiguous.

. References

4.1. Normative

   [RFC 2026] S. Bradner, "The Internet Standards Process - Revision 3"
   November 1996.

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



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   [RFC 3280] R. Housley, W. Ford, W. Polk, and D. Solo, "Internet X.509
   Public Key Infrastructure: Certificate and CRL Profile", April 2002.

4.2. Informative

   [X.501]  ITU-T Recommendation X.501 (1997 E): Information Technology
   - Open Systems Interconnection - The Directory: Models, June 1997.

   [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,
   June 1997.

   [X.660]  ITU-T Recommendation X.660: Information Technology -
   Open Systems Interconnection - Procedures for the Operation of
   OSI Registration Authorities: General Procedures, 1992.

   [X.680]  ITU-T Recommendation X.680: Information Technology -
   Abstract Syntax Notation One, 1997.

. Author's Addresses

   Denis Pinkas
   Bull
   68, Route de Versailles
   78434 Louveciennes Cedex
   FRANCE
   Email: Denis.Pinkas@bull.net

   Thomas Gindin
   IBM Corporation
   6710 Rockledge Drive
   Bethesda, MD 20817
   USA
   Email: tgindin@us.ibm.com

. Intellectual Property 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.

Pinkas, Gindin                                                 [ Page 6]


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   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard.  Please address the information to the IETF Executive
   Director.

















































Pinkas, Gindin                                                 [ Page 7]


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APPENDIX

ASN.1 definitions

A.1. 1988 ASN.1  Module

PKIXpermanentidentifier88 {iso(1) identified-organization(3) dod(6)
       internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
       id-mod-permanent-identifier-88(14) }

DEFINITIONS EXPLICIT TAGS ::=

   BEGIN

   -- EXPORTS ALL --

   IMPORTS

        id-pkix, AttributeType,
                FROM PKIX1Explicit88 {iso(1) identified-organization(3)
                dod(6) internet(1) security(5) mechanisms(5) pkix(7)
                id-mod(0) id-pkix1-explicit-88(1)}

   -- Object Identifiers

-- Externally defined OIDs

   -- Arc for other name forms
   id-on   OBJECT IDENTIFIER ::= { id-pkix 8 }

   -- permanent identifier

   id-on-permanentIdentifier   OBJECT IDENTIFIER ::= { id-on 3 }

     PermanentIdentifier ::=     SEQUENCE {
        identifierValue             IdentifierValue,
        identifierType              IdentifierType             OPTIONAL,
        matchingRule        [0]     IMPLICIT OBJECT IDENTIFIER OPTIONAL
     }

     IdentifierValue ::= CHOICE {
            iA5String            IA5String,
            uTF8String           UTF8String
     }

     IdentifierType ::= CHOICE {
            registeredOID                   OBJECT IDENTIFIER,
            uri                             IA5String
     }

END



Pinkas, Gindin                                                 [ Page 8]


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A.2. 1993 ASN.1  Module

PKIXpermanentidentifier93 {iso(1) identified-organization(3) dod(6)
       internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
       id-mod-permanent-identifier-93(15) }

   DEFINITIONS EXPLICIT TAGS ::=

   BEGIN

   -- EXPORTS ALL --

   IMPORTS

id-pkix, ATTRIBUTE
       FROM PKIX1Explicit93 {iso(1) identified-organization(3) dod(6)
       internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
       id-pkix1-explicit-93(3)};

   -- Object Identifiers

-- Externally defined OIDs

   -- Arc for other name forms
   id-on   OBJECT IDENTIFIER ::= { id-pkix 8 }

-- Locally defined OIDs

id-on-permanentIdentifier     OBJECT IDENTIFIER ::= { id-on 3 }

   -- permanent identifier

   permanentIdentifier ATTRIBUTE ::= {
          WITH SYNTAX     PermanentIdentifier
          ID              id-on-permanentIdentifier }

     PermanentIdentifier ::=     SEQUENCE {
        identifierValue             IdentifierValue,
        identifierType              IdentifierType             OPTIONAL,
        matchingRule        [0]     IMPLICIT OBJECT IDENTIFIER OPTIONAL
     }

     IdentifierValue ::= CHOICE {
            iA5String            IA5String,
            uTF8String           UTF8String
     }

     IdentifierType ::= CHOICE {
            registeredOID                   OBJECT IDENTIFIER,
            uri                             IA5String,
     }

END


Pinkas, Gindin                                                 [ Page 9]


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B. OID's for organizations

In order to obtain an OID for an identifier type, organizations need
first to have a registered OID for themselves (or must use a permanent
URI). In some cases, OID's are provided for free. In other cases a
one-time fee is required. The main difference lies in the nature of
the information that is collected at the time of registration and how
this information is verified for its accuracy.

B.1. Using IANA (Internet Assigned Numbers Authority)

The application form for a Private Enterprise Number in the IANA's
OID list is: http://www.iana.org/cgi-bin/enterprise.pl.

Currently IANA assigns numbers for free. The IANA-registered Private
Enterprises prefix is: iso.org.dod.internet.private.enterprise
(1.3.6.1.4.1)

These numbers are used, among other things, for defining private
SNMP MIBs.

The official assignments under this OID are stored in the IANA file
"enterprise-numbers" available at:
ftp://ftp.isi.edu/in-notes/iana/assignments/enterprise-numbers

B.2. Using an ISO member body

ISO has defined the OID structure in a such a way so that every ISO
member-body has its own unique OID. Then every ISO member-body is free
to allocate its own arc space below.

Organizations and enterprises may contact the ISO member-body where
their organization or enterprise is established to obtain an
organization/enterprise OID.

Currently, ISO members do not assign organization/enterprise OID's for
free.

Most of them do not publish registries of such OID's which they have
assigned, sometimes restricting the access to registered organizations
or preferring to charge inquirers for the assignee of an OID on a
per-inquiry basis. The use of OID's from an ISO member organization
which does not publish such a registry may impose extra costs on the
CA that needs to make sure that the OID corresponds to the registered
organization.

As an example, AFNOR (Association Francaise de Normalisation - the
French organization that is a member of ISO) has defined an arc to
allocate OID's for companies:

{iso (1) member-body (2) fr (250) type-org (1) organisation (n)}



Pinkas, Gindin                                                [ Page 10]


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C.  Full Copyright Statement

   Copyright (C) The Internet Society (2002). 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
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   The limited permissions granted above are perpetual and will not be
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Pinkas, Gindin                                                [ Page 11]