Framework for Establishing a Secure Real-time Transport Protocol (SRTP) Security Context Using Datagram Transport Layer Security (DTLS)
RFC 5763

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Internet Engineering Task Force (IETF)                         J. Fischl
Request for Comments: 5763                                   Skype, Inc.
Category: Standards Track                                  H. Tschofenig
ISSN: 2070-1721                                   Nokia Siemens Networks
                                                             E. Rescorla
                                                              RTFM, Inc.
                                                                May 2010

Framework for Establishing a Secure Real-time Transport Protocol (SRTP)
    Security Context Using Datagram Transport Layer Security (DTLS)

Abstract

   This document specifies how to use the Session Initiation Protocol
   (SIP) to establish a Secure Real-time Transport Protocol (SRTP)
   security context using the Datagram Transport Layer Security (DTLS)
   protocol.  It describes a mechanism of transporting a fingerprint
   attribute in the Session Description Protocol (SDP) that identifies
   the key that will be presented during the DTLS handshake.  The key
   exchange travels along the media path as opposed to the signaling
   path.  The SIP Identity mechanism can be used to protect the
   integrity of the fingerprint attribute from modification by
   intermediate proxies.

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/rfc5763.

Fischl, et al.               Standards Track                    [Page 1]
RFC 5763                   DTLS-SRTP Framework                  May 2010

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
   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 ....................................................4
   2. Overview ........................................................5
   3. Motivation ......................................................7
   4. Terminology .....................................................8
   5. Establishing a Secure Channel ...................................8
   6. Miscellaneous Considerations ...................................10
      6.1. Anonymous Calls ...........................................10
      6.2. Early Media ...............................................11
      6.3. Forking ...................................................11
      6.4. Delayed Offer Calls .......................................11
      6.5. Multiple Associations .....................................11
      6.6. Session Modification ......................................12
      6.7. Middlebox Interaction .....................................12
           6.7.1. ICE Interaction ....................................12
           6.7.2. Latching Control without ICE .......................13
      6.8. Rekeying ..................................................13
      6.9. Conference Servers and Shared Encryptions Contexts ........13
      6.10. Media over SRTP ..........................................14
      6.11. Best Effort Encryption ...................................14

Fischl, et al.               Standards Track                    [Page 2]
RFC 5763                   DTLS-SRTP Framework                  May 2010