AES-GCM Authenticated Encryption in the Secure Real-time Transport Protocol (SRTP)
RFC 7714

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Internet Engineering Task Force (IETF)                         D. McGrew
Request for Comments: 7714                           Cisco Systems, Inc.
Category: Standards Track                                        K. Igoe
ISSN: 2070-1721                                 National Security Agency
                                                           December 2015

                    AES-GCM Authenticated Encryption
           in the Secure Real-time Transport Protocol (SRTP)

Abstract

   This document defines how the AES-GCM Authenticated Encryption with
   Associated Data family of algorithms can be used to provide
   confidentiality and data authentication in the Secure Real-time
   Transport Protocol (SRTP).

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/rfc7714.

Copyright Notice

   Copyright (c) 2015 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.

McGrew & Igoe                Standards Track                    [Page 1]
RFC 7714                    AES-GCM for SRTP               December 2015

Table of Contents

   1. Introduction ....................................................3
   2. Conventions Used in This Document ...............................4
   3. Overview of the SRTP/SRTCP AEAD Security Architecture ...........4
   4. Terminology .....................................................5
   5. Generic AEAD Processing .........................................6
      5.1. Types of Input Data ........................................6
      5.2. AEAD Invocation Inputs and Outputs .........................6
           5.2.1. Encrypt Mode ........................................6
           5.2.2. Decrypt Mode ........................................7
      5.3. Handling of AEAD Authentication ............................7
   6. Counter Mode Encryption .........................................7
   7. Unneeded SRTP/SRTCP Fields ......................................8
      7.1. SRTP/SRTCP Authentication Tag Field ........................8
      7.2. RTP Padding ................................................9
   8. AES-GCM Processing for SRTP .....................................9
      8.1. SRTP IV Formation for AES-GCM ..............................9
      8.2. Data Types in SRTP Packets ................................10
      8.3. Handling Header Extensions ................................11
      8.4. Prevention of SRTP IV Reuse ...............................12
   9. AES-GCM Processing of SRTCP Compound Packets ...................13
      9.1. SRTCP IV Formation for AES-GCM ............................13
      9.2. Data Types in Encrypted SRTCP Compound Packets ............14
      9.3. Data Types in Unencrypted SRTCP Compound Packets ..........16
      9.4. Prevention of SRTCP IV Reuse ..............................17
   10. Constraints on AEAD for SRTP and SRTCP ........................17
   11. Key Derivation Functions ......................................18
   12. Summary of AES-GCM in SRTP/SRTCP ..............................19
   13. Security Considerations .......................................20
      13.1. Handling of Security-Critical Parameters .................20
      13.2. Size of the Authentication Tag ...........................21
   14. IANA Considerations ...........................................21
      14.1. SDES .....................................................21
      14.2. DTLS-SRTP ................................................22
      14.3. MIKEY ....................................................23
   15. Parameters for Use with MIKEY .................................23
   16. Some RTP Test Vectors .........................................24
      16.1. SRTP AEAD_AES_128_GCM ....................................25
           16.1.1. SRTP AEAD_AES_128_GCM Encryption ..................25
           16.1.2. SRTP AEAD_AES_128_GCM Decryption ..................27