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Versions: 00 01 02 03 05 06 07 08 rfc4476                               
Internet Draft                                               C. Francis
PKIX Working Group                          WetStone Technologies, Inc.
October 2002                                                  D. Pinkas
Expires: April 2003                                                Bull

                    Attribute Certificate Policy extension

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, and its working groups. Note that other groups
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This document describes one certificate extension to explicitly
state the Attribute Certificate (AC) policies that apply to a given
Attribute Certificate.

Conventions Used In This Document

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
document are to be interpreted as described in [RFC2119].

1. Introduction

When issuing a PKC, a Certificate Authority (CA) can perform various
levels of verification with regard to the subject identity.  A CA makes
its verification procedures, as well as other operational rules it
abides by, "visible" through a certificate policy, which may be
referenced by a certificate policies extension in the PKC.

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When issuing an AC, an Attribute Authority (AA) can perform various
levels of initial and subsequent verifications with regard to the
attributes that will be contained in attribute certificates.

These verification procedures, as well as other operational rules the
attribute certification authority abides by, can be made "visible"
through an AC policies extension, which may be included in the AC.

The purpose of this document is to define such an extension, but not
the AC policies themselves.

2. AC Policy Extension Semantics

Attribute Certificates are defined in [RFC3281].

An Attribute Certificate Policy (ACP) is a set of rules that indicates
generic rules for registering, verifying, delivering and revoking the
attributes contained in a particular Attribute Certificate.

It should thus be noticed that an AA does not necessarily support one
single policy. However, for each AC that is delivered it SHALL make
sure that the policy applies to all the attributes that are contained
in it.

An Attribute Certificate Policy may be used by a certificate user to
decide whether or not to trust the attributes contained in a
certificate for a particular purpose.

When a certificate contains an AC policies extension, the extension
MAY, at the option of the certificate issuer, be either critical or
non-critical.  The extension MAY contain optional qualifiers.

The AC Policies extension MAY be included in an attribute certificate.
Like all X.509 certificate extensions, the AC policies extension is
defined using ASN.1 [X.208-88, X.209-88].

The AC policies extension is identified by id-pe-acPolicies.

     id-pe-acPolicies OBJECT IDENTIFIER  ::=  { id-pe <<TBD>> }

The AC policies extension includes a list of AC policies recognized by
the issuing authority that apply to the attributes included in the
certificate, together with optional qualifier information pertaining to
these AC policies.

AC Policies and AC policy qualifier types may be defined by any
organization with a need.  Object identifiers used to identify AC
Policies and AC Policy qualifier types are assigned in accordance with
[ITU-T Rec. X660 | ISO/IEC 9834-1].

The presence of this extension in an attribute certificate indicates
the AC policies for which the attribute certificate is valid.

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An application that recognizes this extension and its content SHALL
process the extension regardless of the value of the criticality flag.

If the extension is both flagged non-critical and is not recognized,
then the application MAY ignore it.

If the extension is flagged critical or is recognized, it indicates
that the attributes contained in the certificate SHALL only be used for
the purpose, and in accordance with the rules implied by one of the
indicated AC policies.  The rules of a particular policy MAY require
the certificate-using system to process the qualifier value in a
particular way.

If the extension is marked critical or is recognized, certificate users
MUST use the list of AC policies and associated qualifiers to determine
whether it is appropriate to use the attributes contained in that
certificate for a particular transaction.

2.1 AC Policy Extension Syntax

The AC Policy syntax mirrors the certificate policies extension used
for public key certificates defined in [X.509] and profiled in

The syntax for the AC Policy extension is:

acPolicies EXTENSION ::= {
     SYNTAX              acPoliciesSyntax
     IDENTIFIED BY       id-pe-acPolicies}

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

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


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

To promote interoperability, this document RECOMMENDS that policy
information terms consist of only an OID.

2.2 Attribute Certificate Policies

The scope of this document is not the definition of the detailed
content of Attribute Certificate policies themselves, therefore
specific policies are not defined in this document.

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2.3. Policy Qualifiers

2.3.1. Generic Policy Qualifiers

   This specification defines two generic 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 AA.  The pointer is in the
   form of a URI.

   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.

These policies Qualifiers are defined in [RFC3280].

   -- 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 }

2.3.2. Specific Policy Qualifiers

Specific Policy qualifiers MAY be used to convey important
differences between specific policies to relying parties.

This specification defines two specific policy qualifier types
for use by certificate policy writers and certificate issuers. Initial Verification Qualifier

Attributes inserted in a certificate are only verified at the
time of the initial registration of the attribute for a given
end-entity. Unless a specific revocation request is received
and granted by the AA or the CA, attributes will continue to be
certified for the period indicated by the certificateÆs
validity period.

For an AC, since the validity period of an AC can be much
shorter than the period during which the asserted attribute(s)
are granted to the holder, unless specific additional
information is included, it cannot be known when attributes
were initially verified.

The initial verification qualifier indicates when the attributes
contained in the AC have been initially verified.

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   id-qt-iniVer      OBJECT IDENTIFIER ::=  { id-qt W }

   IniVer ::= GeneralizedTime

Note: When an AC contains several attributes with different
initial verification dates, this field contains the oldest
verification date. Regular Verification Qualifier

AAs may choose to regularly verify some attributes so that
relying parties may be more confident about their association with
the end-entity. This information may be made available directly in an
attribute certificate through the Regular Verification qualifier.

The Regular Verification Qualifier indicates that the attributes
contained in the AC are regularly verified and includes the
verification time period.

   id-qt-regVer      OBJECT IDENTIFIER ::=  { id-qt X }

   RegVer ::=  CHOICE {
     days       [0]    INTEGER ,
     months     [1]    INTEGER ,
     years      [2]    INTEGER

3. Security Considerations

The Attribute Certification Policy defined in this document applies
for all the attributes that are included in one AC. AAs shall make sure
that the policy applies to all the attributes which are included in the
certificates they issue.

Attributes may be dynamically grouped in several ACs. It should be
observed that since the management of some attributes may be different,
different policies and/or different policy qualifiers may be used by
the same AA.

4. References

[ITU-T Rec. X660 | ITU-T Recommendation Rec X.660 (1992)
ISO/IEC 9834-1]  | ISO/IEC 9834-1: 1993, Information
                   technology - Open Systems Interconnection
                   Procedures for the operation of OSI
                   Registration Authorities: General procedures.

[RFC3280]  Certificate and Certificate Revocation List (CRL) Profile.
           R. Housley, W.Polk, W.Ford, and D. Solo. April 2002.

[RFC3281]  An Internet Attribute Certificate Profile for Authorization.
           S. Farrell S. and R. Housley. April 2002.

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[X.208-88] CCITT.  Recommendation X.208: Specification of
           Abstract Syntax Notation One (ASN.1). 1988.

[X.209-88] CCITT.  Recommendation X.209: Specification of Basic
           Encoding Rules for Abstract Syntax Notation One (ASN.1).

[X.509]    ITU-T Recommendation X.509 (2000): Information Technology û
           Open Systems Interconnections - The Directory:
           Public-key and Attribute Frameworks, March 2000

Author's Addresses

   Christopher S. Francis
   WetStone Technologies, Inc.
   17755 US Highway 19 North, Suite 150
   Clearwater, Florida   33764

   Email: Chris.Francis@wetstonetech.com

   Denis Pinkas
   Rue Jean Jaures
   78340 Les Clayes-sous-Bois

   Email: Denis.Pinkas@bull.net

Full Copyright Statement

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The limited permissions granted above are perpetual and will not be
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This document and the information contained herein is provided on an

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Funding for the RFC Editor function is currently provided by the
Internet Society.

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Annex A (normative): ASN.1 Definitions

To be provided.

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