The Use of Galois/Counter Mode (GCM) in IPsec Encapsulating Security Payload (ESP)
RFC 4106

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Network Working Group                                           J. Viega
Request for Comments: 4106                         Secure Software, Inc.
Category: Standards Track                                      D. McGrew
                                                     Cisco Systems, Inc.
                                                               June 2005

                 The Use of Galois/Counter Mode (GCM)
             in IPsec Encapsulating Security Payload (ESP)

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This memo describes the use of the Advanced Encryption Standard (AES)
   in Galois/Counter Mode (GCM) as an IPsec Encapsulating Security
   Payload (ESP) mechanism to provide confidentiality and data origin
   authentication.  This method can be efficiently implemented in
   hardware for speeds of 10 gigabits per second and above, and is also
   well-suited to software implementations.

Table of Contents

   1. Introduction ....................................................2
      1.1. Conventions Used in This Document ..........................2
   2. AES-GCM .........................................................3
   3. ESP Payload Data ................................................3
      3.1. Initialization Vector (IV) .................................3
      3.2. Ciphertext .................................................4
   4. Nonce Format ....................................................4
   5. AAD Construction ................................................5
   6. Integrity Check Value (ICV) .....................................5
   7. Packet Expansion ................................................6
   8. IKE Conventions .................................................6
      8.1. Keying Material and Salt Values ............................6
      8.2. Phase 1 Identifier .........................................6
      8.3. Phase 2 Identifier .........................................7
      8.4. Key Length Attribute .......................................7

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RFC 4106                        GCM ESP                        June 2005

   9. Test Vectors ....................................................7
   10. Security Considerations ........................................7
   11. Design Rationale ...............................................8
   12. IANA Considerations ............................................8
   13. Acknowledgements ...............................................9
   14. Normative References ...........................................9
   15. Informative References .........................................9

1.  Introduction

   This document describes the use of AES in GCM mode (AES-GCM) as an
   IPsec ESP mechanism for confidentiality and data origin
   authentication.  We refer to this method as AES-GCM-ESP.  This
   mechanism is not only efficient and secure, but it also enables
   high-speed implementations in hardware.  Thus, AES-GCM-ESP allows
   IPsec connections that can make effective use of emerging 10-gigabit
   and 40-gigabit network devices.

   Counter mode (CTR) has emerged as the preferred encryption method for
   high-speed implementations.  Unlike conventional encryption modes
   such as Cipher Block Chaining (CBC) and Cipher Block Chaining Message
   Authentication Code (CBC-MAC), CTR can be efficiently implemented at
   high data rates because it can be pipelined.  The ESP CTR protocol
   describes how this mode can be used with IPsec ESP [RFC3686].

   Unfortunately, CTR provides no data origin authentication, and thus
   the ESP CTR standard requires the use of a data origin authentication
   algorithm in conjunction with CTR.  This requirement is problematic,
   because none of the standard data origin authentication algorithms
   can be efficiently implemented for high data rates.  GCM solves this
   problem, because under the hood, it combines CTR mode with a secure,
   parallelizable, and efficient authentication mechanism.

   This document does not cover implementation details of GCM.  Those
   details can be found in [GCM], along with test vectors.

1.1.  Conventions Used in This Document

   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].

Viega & McGrew              Standards Track                     [Page 2]
RFC 4106                        GCM ESP                        June 2005