Keying Material Exporters for Transport Layer Security (TLS)
RFC 5705

• Status
• IESG evaluation record
• IESG writeups
• Email expansions
• History

• Versions
• 07

Internet Engineering Task Force (IETF)                       E. Rescorla
Request for Comments: 5705                                    RTFM, Inc.
Category: Standards Track                                     March 2010
ISSN: 2070-1721

      Keying Material Exporters for Transport Layer Security (TLS)

Abstract

   A number of protocols wish to leverage Transport Layer Security (TLS)
   to perform key establishment but then use some of the keying material
   for their own purposes.  This document describes a general mechanism
   for allowing that.

Status of This Memo

   This is an Internet Standards Track document.

   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).  Further information on
   Internet Standards is available in 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/5705.

Copyright Notice

   Copyright (c) 2010 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.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow

Rescorla                     Standards Track                    [Page 1]
RFC 5705                      TLS Exporters                   March 2010

   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.  Conventions Used In This Document . . . . . . . . . . . . . . . 3
   3.  Binding to Application Contexts . . . . . . . . . . . . . . . . 3
   4.  Exporter Definition . . . . . . . . . . . . . . . . . . . . . . 4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 7
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 7

1.  Introduction

   Note:  The mechanism described in this document was previously known
          as "TLS Extractors" but was changed to avoid a name conflict
          with the use of the term "Extractor" in the cryptographic
          community.

   A number of protocols wish to leverage Transport Layer Security (TLS)
   [RFC5246] or Datagram TLS (DTLS) [RFC4347] to perform key
   establishment but then use some of the keying material for their own
   purposes.  A typical example is DTLS-SRTP [DTLS-SRTP], a key
   management scheme for the Secure Real-time Transport Protocol (SRTP)
   that uses DTLS to perform a key exchange and negotiate the SRTP
   [RFC3711] protection suite and then uses the DTLS master_secret to
   generate the SRTP keys.

   These applications imply a need to be able to export keying material
   (later called Exported Keying Material or EKM) from TLS/DTLS to an
   application or protocol residing at an upper layer, and to securely
   agree on the upper-layer context where the keying material will be
   used.  The mechanism for exporting the keying material has the
   following requirements:

   o  Both client and server need to be able to export the same EKM
      value.

Rescorla                     Standards Track                    [Page 2]
RFC 5705                      TLS Exporters                   March 2010

   o  EKM values should be indistinguishable from random data to
      attackers who don't know the master_secret.

   o  It should be possible to export multiple EKM values from the same