Encrypted Key Transport for Secure RTP
draft-ietf-avtcore-srtp-ekt-01

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Replaces draft-ietf-avt-srtp-ekt
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AVTCORE Working Group                                          D. McGrew
Internet-Draft                                              F. Andreasen
Intended status: Standards Track                                 D. Wing
Expires: April 24, 2014                                            Cisco
                                                        October 21, 2013

                 Encrypted Key Transport for Secure RTP
                     draft-ietf-avtcore-srtp-ekt-01

Abstract

   Encrypted Key Transport (EKT) is an extension to Secure Real-time
   Transport Protocol (SRTP) that provides for the secure transport of
   SRTP master keys, Rollover Counters, and other information, within
   SRTP or SRTCP.  This facility enables SRTP to work for decentralized
   conferences with minimal control.

   This note defines EKT, and also describes how to use it with SDP
   Security Descriptions, DTLS-SRTP, and MIKEY.  These other key
   management protocols provide an EKT key to everyone in a session, and
   EKT coordinates the keys within the session.

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   Copyright (c) 2013 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
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   (http://trustee.ietf.org/license-info) in effect on the date of

McGrew, et al.           Expires April 24, 2014                 [Page 1]
Internet-Draft                  EKT SRTP                    October 2013

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  History  . . . . . . . . . . . . . . . . . . . . . . . . .  5
     1.2.  Conventions Used In This Document  . . . . . . . . . . . .  5
   2.  Encrypted Key Transport  . . . . . . . . . . . . . . . . . . .  6
     2.1.  EKT Field Formats  . . . . . . . . . . . . . . . . . . . .  6
     2.2.  Packet Processing and State Machine  . . . . . . . . . . .  8
       2.2.1.  Outbound Processing  . . . . . . . . . . . . . . . . .  8
       2.2.2.  Inbound Processing . . . . . . . . . . . . . . . . . . 10
     2.3.  Ciphers  . . . . . . . . . . . . . . . . . . . . . . . . . 11
       2.3.1.  The Default Cipher . . . . . . . . . . . . . . . . . . 12
       2.3.2.  Other EKT Ciphers  . . . . . . . . . . . . . . . . . . 13
     2.4.  Synchronizing Operation  . . . . . . . . . . . . . . . . . 13
     2.5.  Transport  . . . . . . . . . . . . . . . . . . . . . . . . 14
     2.6.  Timing and Reliability Consideration . . . . . . . . . . . 14
   3.  Use of EKT with SDP Security Descriptions  . . . . . . . . . . 16
     3.1.  SDP Security Descriptions Recap  . . . . . . . . . . . . . 16
     3.2.  Relationship between EKT and SDP Security Descriptions . . 17
     3.3.  Overview of Combined EKT and SDP Security Description
           Operation  . . . . . . . . . . . . . . . . . . . . . . . . 19
     3.4.  EKT Extensions to SDP Security Descriptions  . . . . . . . 19
       3.4.1.  EKT_Cipher . . . . . . . . . . . . . . . . . . . . . . 19
       3.4.2.  EKT_Key  . . . . . . . . . . . . . . . . . . . . . . . 20
       3.4.3.  EKT_SPI  . . . . . . . . . . . . . . . . . . . . . . . 20
     3.5.  Offer/Answer Procedures  . . . . . . . . . . . . . . . . . 20
       3.5.1.  Generating the Initial Offer - Unicast Streams . . . . 21
       3.5.2.  Generating the Initial Answer - Unicast Streams  . . . 22
       3.5.3.  Processing of the Initial Answer - Unicast Streams . . 23
     3.6.  SRTP-Specific Use Outside Offer/Answer . . . . . . . . . . 24
     3.7.  Modifying the Session  . . . . . . . . . . . . . . . . . . 24
     3.8.  Backwards Compatibility Considerations . . . . . . . . . . 25
     3.9.  Grammar  . . . . . . . . . . . . . . . . . . . . . . . . . 25
   4.  Use of EKT with DTLS-SRTP Key Transport  . . . . . . . . . . . 27
     4.1.  EKT Extensions to DTLS-SRTP  . . . . . . . . . . . . . . . 27
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