Using Counter Modes with Encapsulating Security Payload (ESP) and Authentication Header (AH) to Protect Group Traffic
RFC 6054

Internet Engineering Task Force (IETF)                         D. McGrew
Request for Comments: 6054                                       B. Weis
Category: Standards Track                                  Cisco Systems
ISSN: 2070-1721                                            November 2010

   Using Counter Modes with Encapsulating Security Payload (ESP) and
          Authentication Header (AH) to Protect Group Traffic

Abstract

   Counter modes have been defined for block ciphers such as the
   Advanced Encryption Standard (AES).  Counter modes use a counter,
   which is typically assumed to be incremented by a single sender.
   This memo describes the use of counter modes when applied to the
   Encapsulating Security Payload (ESP) and Authentication Header (AH)
   in multiple-sender group applications.

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/rfc6054.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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McGrew & Weis                Standards Track                    [Page 1]
RFC 6054                   Group Counter Modes             November 2010

Table of Contents

   1. Introduction ....................................................2
      1.1. Requirements Notation ......................................2
   2. Problem Statement ...............................................2
   3. IV Formation for Counter Modes with Group Keys ..................3
   4. Group Key Management Conventions ................................4
   5. Security Considerations .........................................5
   6. Acknowledgements ................................................6
   7. References ......................................................6
      7.1. Normative References .......................................6
      7.2. Informative References .....................................6
   Appendix A. Rationale for the IV Formation for Counter Modes
               with Group Keys ........................................9
   Appendix B. Example ................................................9

1.  Introduction

   The IP Encapsulating Security Payload (ESP) specification [RFC4303]
   and Authentication Header (AH) [RFC4302] are security protocols for
   IPsec [RFC4301].  Several new AES encryption modes of operation have
   been specified for ESP: Counter Mode (CTR) [RFC3686], Galois/Counter
   Mode (GCM) [RFC4106], and Counter with Cipher Block Chaining-Message
   Authentication Code (CBC-MAC) Mode (CCM) [RFC4309]; and one that has
   been specified for both ESP and AH: the Galois Message Authentication
   Code (GMAC) [RFC4543].  A Camellia counter mode [RFC5528] and a GOST
   counter mode [RFC4357] have also been specified.  These new modes
   offer advantages over traditional modes of operation.  However, they
   all have restrictions on their use in situations in which multiple
   senders are protecting traffic using the same key.  This document
   addresses this restriction and describes how these modes can be used
   with group key management protocols such as the Group Domain of
   Interpretation (GDOI) protocol [RFC3547] and the Group Secure
   Association Key Management Protocol (GSAKMP) [RFC4535].

1.1.  Requirements Notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

2.  Problem Statement

   The Counter Mode (CTR) of operation [FIPS.800-38A.2001] has become