PKIX Working Group                                      D. Pinkas (Bull)INTERNET-DRAFT                                           T. Gindin (IBM)Expires: June 2003                                         December 2002Target category: Standard Track                 Internet X.509 Public Key Infrastructure                          Permanent Identifier                       <draft-ietf-pkix-pi-06.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   Task Force (IETF), its areas, and its working groups. Note that other   groups may also distribute working documents as Internet-Drafts.   Internet-Drafts are draft documents valid for a maximum of six months   and may be updated, replaced, or obsoleted by other documents at any   time. It is inappropriate to use Internet-Drafts as reference   material or to cite them other than as "work in progress."   The list of current Internet-Drafts can be accessed at   http://www.ietf.org/ietf/1id-abstracts.txt   The list of Internet-Draft Shadow Directories can be accessed at   http://www.ietf.org/shadow.html.   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.Pinkas, Gindin                                                 [ Page 1]Permanent Identifier                Document Expiration:       June 20031  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 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 consists of an identifier value assigned   within a given naming space by the organization which is    authoritative for that naming space.  Such an organization is known    as an Assigner Authority.   An Assigner Authority may be a government, a government agency, a   corporation, or any other sort of organization.  It MUST have a    unique identifier to distinguish it from any other such authority.   In this standard, that identifier MUST be an object identifier or    be representable as a URI.   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.Pinkas, Gindin                                                 [ Page 2]Permanent Identifier                Document Expiration:       June 2003         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.   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.2. 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    Assigner Authority and the type of that field.Pinkas, Gindin                                                 [ Page 3]Permanent Identifier                Document Expiration:       June 2003   When the IdentifierType field is missing, then it is assumed that    the Assigner Authority is the CA itself and that there is only one    type of such identifier for the CA.   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 Assigner Authority, 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.520.3. Security considerations   A given entity may have at an instant of time or at different    instants of time multiple forms of identities. Pinkas, Gindin                                                 [ Page 4]Permanent Identifier                Document Expiration:       June 2003   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.   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. It is the responsibility of the CA to verify that    the permanent identifier being included in the certificate refers    to the subject being certified.   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 are 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.Pinkas, Gindin                                                 [ Page 5]Permanent Identifier                Document Expiration:       June 20034. References4.1. 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.   [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.