Alternative Certificate Formats for the Public-Key Infrastructure Using X.509 (PKIX) Certificate Management Protocols
RFC 4212

Document Type RFC - Informational (October 2005; No errata)
Last updated 2013-03-02
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Network Working Group                                          M. Blinov
Request for Comments: 4212                          Guardeonic Solutions
Category: Informational                                         C. Adams
                                                    University of Ottawa
                                                            October 2005

                Alternative Certificate Formats for the
             Public-Key Infrastructure Using X.509 (PKIX)
                    Certificate Management Protocols

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2005).


   This document is not a candidate for any level of Internet Standard.
   The IETF disclaims any knowledge of the fitness of this document for
   any purpose, and in particular notes that it has not had IETF review
   for such things as security, congestion control, or inappropriate
   interaction with deployed protocols.  The RFC Editor has chosen to
   publish this document at its discretion.  Readers of this document
   should exercise caution in evaluating its value for implementation
   and deployment.


   The Public-Key Infrastructure using X.509 (PKIX) Working Group of the
   Internet Engineering Task Force (IETF) has defined a number of
   certificate management protocols.  These protocols are primarily
   focused on X.509v3 public-key certificates.  However, it is sometimes
   desirable to manage certificates in alternative formats as well.
   This document specifies how such certificates may be requested using
   the Certificate Request Message Format (CRMF) syntax that is used by
   several different protocols.  It also explains how alternative
   certificate formats may be incorporated into such popular protocols
   as PKIX Certificate Management Protocol (PKIX-CMP) and Certificate
   Management Messages over CMS (CMC).

Blinov & Adams               Informational                      [Page 1]
RFC 4212            Alternative Certificate Formats         October 2005

1.  Introduction

   Full certificate life-cycle management in a Public-Key Infrastructure
   (PKI) requires protocol support in order to achieve automated
   processing and end user transparency.  Such protocols require
   standardization in order to allow more than one vendor to supply
   various pieces -- End Entity (EE), Certification Authority (CA),
   Registration Authority (RA) -- in the PKI deployment of a single
   organization, or to allow multiple, independently-deployed PKIs to be
   interconnected usefully.

   The IETF PKIX (Public-Key Infrastructure using X.509) Working Group
   currently has several certificate management protocols and
   certificate request syntax specifications on the standards track.
   Although these specifications are primarily focused on X.509v3
   public-key certificates, some of them can be easily extended to
   handle certificates in alternative formats as well.

   This document focuses on a popular certificate request syntax called
   CRMF (Certificate Request Message Format) [CRMF].  Although the
   original specification of CRMF is X.509-specific, extensions have
   already been proposed to allow for alternative certificate templates
   [CMP].  However, those extensions have only defined a framework; they
   did not define the exact format to be used for various certificate

   This document builds on top of the framework mentioned above and
   defines how CRMF can be used to request certificates of the following

   - X.509 attribute certificates [ATTCERT]

   - OpenPGP certificates [OPENPGP]

   The CRMF syntax is used by such popular protocols as PKIX-CMP (PKIX
   Certificate Management Protocol) [CMP] and CMC (Certificate
   Management Messages over CMS) [CMC].  This means that CRMF extensions
   proposed in this document enable these protocols to request
   certificates of the above types.  However, it is not enough to be
   able to request a certificate.  The protocol should be prepared to
   handle certificates of a particular type and, for example, return
   them to the user.

   This document proposes extensions to the PKIX-CMP and CMC protocols
   that are required to manage certificates in alternative formats.

Blinov & Adams               Informational                      [Page 2]
RFC 4212            Alternative Certificate Formats         October 2005

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  Certificate Template

   One of the features of the CRMF format is its use of the CertTemplate
   construct, which allows a requester (EE, or RA acting on behalf of an
   EE) to specify as much or as little as they wish regarding the
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