TLS Elliptic Curve Cipher Suites with SHA-256/384 and AES Galois Counter Mode (GCM)
RFC 5289

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Network Working Group                                        E. Rescorla
Request for Comments:  5289                                   RTFM, Inc.
Category:  Informational                                     August 2008

                 TLS Elliptic Curve Cipher Suites with
             SHA-256/384 and AES Galois Counter Mode (GCM)

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Abstract

   RFC 4492 describes elliptic curve cipher suites for Transport Layer
   Security (TLS).  However, all those cipher suites use HMAC-SHA-1 as
   their Message Authentication Code (MAC) algorithm.  This document
   describes sixteen new cipher suites for TLS that specify stronger MAC
   algorithms.  Eight use Hashed Message Authentication Code (HMAC) with
   SHA-256 or SHA-384, and eight use AES in Galois Counter Mode (GCM).

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.  Conventions Used in This Document . . . . . . . . . . . . . . . 2
   3.  Cipher Suites . . . . . . . . . . . . . . . . . . . . . . . . . 2
     3.1.  HMAC-Based Cipher Suites  . . . . . . . . . . . . . . . . . 2
     3.2.  Galois Counter Mode-Based Cipher Suites . . . . . . . . . . 3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 3
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 3
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 4
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 4
     7.1.  Normative References  . . . . . . . . . . . . . . . . . . . 4
     7.2.  Informative References  . . . . . . . . . . . . . . . . . . 5

Rescorla                     Informational                      [Page 1]
RFC 5289                    TLS ECC New MAC                  August 2008

1.  Introduction

   RFC 4492 [RFC4492] describes Elliptic Curve Cryptography (ECC) cipher
   suites for Transport Layer Security (TLS).  However, all of the RFC
   4492 suites use HMAC-SHA1 as their MAC algorithm.  Due to recent
   analytic work on SHA-1 [Wang05], the IETF is gradually moving away
   from SHA-1 and towards stronger hash algorithms.  This document
   specifies TLS ECC cipher suites that use SHA-256 and SHA-384 [SHS]
   rather than SHA-1.

   TLS 1.2 [RFC5246], adds support for authenticated encryption with
   additional data (AEAD) cipher modes [RFC5116].  This document also
   specifies a set of ECC cipher suites using one such mode, Galois
   Counter Mode (GCM) [GCM].  Another document [RFC5288] provides
   support for GCM with other key establishment methods.

2.  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].

3.  Cipher Suites

   This document defines 16 new cipher suites to be added to TLS.  All
   use Elliptic Curve Cryptography for key exchange and digital
   signature, as defined in RFC 4492.

3.1.  HMAC-Based Cipher Suites

   The first eight cipher suites use AES [AES] in Cipher Block Chaining
   (CBC) [CBC] mode with an HMAC-based MAC:

     CipherSuite TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256  = {0xC0,0x23};
     CipherSuite TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384  = {0xC0,0x24};
     CipherSuite TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256   = {0xC0,0x25};
     CipherSuite TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA384   = {0xC0,0x26};
     CipherSuite TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256    = {0xC0,0x27};
     CipherSuite TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384    = {0xC0,0x28};
     CipherSuite TLS_ECDH_RSA_WITH_AES_128_CBC_SHA256     = {0xC0,0x29};
     CipherSuite TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384     = {0xC0,0x2A};

   These eight cipher suites are the same as the corresponding cipher
   suites in RFC 4492 (with names ending in "_SHA" in place of "_SHA256"
   or "_SHA384"), except for the MAC and Pseudo Random Function (PRF)
   algorithms.

Rescorla                     Informational                      [Page 2]
RFC 5289                    TLS ECC New MAC                  August 2008

   These SHALL be as follows:

   o  For cipher suites ending with _SHA256, the PRF is the TLS PRF
      [RFC5246] with SHA-256 as the hash function.  The MAC is HMAC
      [RFC2104] with SHA-256 as the hash function.

   o  For cipher suites ending with _SHA384, the PRF is the TLS PRF
      [RFC5246] with SHA-384 as the hash function.  The MAC is HMAC
      [RFC2104] with SHA-384 as the hash function.

3.2.  Galois Counter Mode-Based Cipher Suites

   The second eight cipher suites use the same asymmetric algorithms as
   those in the previous section but use the new authenticated
   encryption modes defined in TLS 1.2 with AES in Galois Counter Mode
   (GCM) [GCM]:

     CipherSuite TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256  = {0xC0,0x2B};