Using OpenPGP Keys for Transport Layer Security (TLS) Authentication
RFC 6091

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Internet Engineering Task Force (IETF)              N. Mavrogiannopoulos
Request for Comments: 6091                                           KUL
Obsoletes: 5081                                               D. Gillmor
Category: Informational                                      Independent
ISSN: 2070-1721                                            February 2011

  Using OpenPGP Keys for Transport Layer Security (TLS) Authentication

Abstract

   This memo defines Transport Layer Security (TLS) extensions and
   associated semantics that allow clients and servers to negotiate the
   use of OpenPGP certificates for a TLS session, and specifies how to
   transport OpenPGP certificates via TLS.  It also defines the registry
   for non-X.509 certificate types.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6091.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Mavrogiannopoulos & Gillmor   Informational                     [Page 1]
RFC 6091                   Using OpenPGP Keys              February 2011

Table of Contents

   1. Introduction ....................................................2
   2. Terminology .....................................................2
   3. Changes to the Handshake Message Contents .......................3
      3.1. Client Hello ...............................................3
      3.2. Server Hello ...............................................4
      3.3. Server Certificate .........................................4
      3.4. Certificate Request ........................................6
      3.5. Client Certificate .........................................6
      3.6. Other Handshake Messages ...................................7
   4. Security Considerations .........................................7
   5. IANA Considerations .............................................7
   6. Acknowledgements ................................................8
   7. References ......................................................8
      7.1. Normative References .......................................8
      7.2. Informative References .....................................8
   Appendix A.  Changes from RFC 5081 .................................9

1.  Introduction

   The IETF has two sets of standards for public key certificates: one
   set for the use of X.509 certificates [RFC5280], and one for OpenPGP
   certificates [RFC4880].  At the time of this writing, TLS [RFC5246]
   standards are defined to use X.509 certificates.  This document
   specifies a way to negotiate the use of OpenPGP certificates for a
   TLS session, and specifies how to transport OpenPGP certificates via
   TLS.  The proposed extensions are backward-compatible with the
   current TLS specification, so that existing client and server
   implementations that make use of X.509 certificates are not affected.

   These extensions are not backward-compatible with [RFC5081], and the
   major differences are summarized in Appendix A.  Although the OpenPGP
   CertificateType value is being reused by this memo with the same
   number as that specified in [RFC5081] but with different semantics,
   we believe that this causes no interoperability issues because the
   latter was not widely deployed.

2.  Terminology

   The term "OpenPGP key" is used in this document as in the OpenPGP
   specification [RFC4880].  We use the term "OpenPGP certificate" to
   refer to OpenPGP keys that are enabled for authentication.

   This document uses the same notation and terminology used in the TLS
   Protocol specification [RFC5246].

Mavrogiannopoulos & Gillmor   Informational                     [Page 2]
RFC 6091                   Using OpenPGP Keys              February 2011