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

RFC 4492 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 , the IETF is gradually moving away from SHA-1 and towards stronger hash algorithms. This document specifies TLS ECC cipher suites which use SHA-256 and SHA-384 rather than SHA-1. TLS 1.2 , adds support for authenticated encryption with additional data (AEAD) cipher modes . This document also specifies a set of ECC cipher suites using one such mode, Galois Counter Mode (GCM) . Another document , provides support for GCM with other key establishment methods.

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 .

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.

The first eight cipher suites use AES in CBC mode with an HMAC-based MAC: CipherSuite TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 = {0xXX,XX}; CipherSuite TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384 = {0xXX,XX}; CipherSuite TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256 = {0xXX,XX}; CipherSuite TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA384 = {0xXX,XX}; CipherSuite TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 = {0xXX,XX}; CipherSuite TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 = {0xXX,XX}; CipherSuite TLS_ECDH_RSA_WITH_AES_128_CBC_SHA256 = {0xXX,XX}; CipherSuite TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384 = {0xXX,XX}; 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 hash and PRF algorithms. These SHALL be as follows: For cipher suites ending with _SHA256, the PRF is the TLS PRF with SHA-256 as the hash function. The MAC is HMAC with SHA-256 as the hash function. For cipher suites ending with _SHA384, the PRF is the TLS PRF with SHA-384 as the hash function. The MAC is HMAC with SHA-384 as the hash function.

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) : CipherSuite TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 = {0xXX,XX}; CipherSuite TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 = {0xXX,XX}; CipherSuite TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256 = {0xXX,XX}; CipherSuite TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384 = {0xXX,XX}; CipherSuite TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 = {0xXX,XX}; CipherSuite TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 = {0xXX,XX}; CipherSuite TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256 = {0xXX,XX}; CipherSuite TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384 = {0xXX,XX}; These cipher suites use authenticated encryption with additional data algorithms AEAD_AES_128_GCM and AEAD_AES_256_GCM described in . GCM is used as described in . The PRFs SHALL be as follows: For cipher suites ending with _SHA256, the PRF is the TLS PRF with SHA-256 as the hash function. For cipher suites ending with _SHA384, the PRF is the TLS PRF with SHA-384 as the hash function.

The security considerations in RFC 4346, RFC 4492, and apply to this document as well. In addition, as described in , these cipher suites may only be used with TLS 1.2 or greater.

IANA has assigned the following values for these cipher suites: CipherSuite TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 = {0xXX,XX}; CipherSuite TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384 = {0xXX,XX}; CipherSuite TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256 = {0xXX,XX}; CipherSuite TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA384 = {0xXX,XX}; CipherSuite TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 = {0xXX,XX}; CipherSuite TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 = {0xXX,XX}; CipherSuite TLS_ECDH_RSA_WITH_AES_128_CBC_SHA256 = {0xXX,XX}; CipherSuite TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384 = {0xXX,XX}; CipherSuite TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 = {0xXX,XX}; CipherSuite TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 = {0xXX,XX}; CipherSuite TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256 = {0xXX,XX}; CipherSuite TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384 = {0xXX,XX}; CipherSuite TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 = {0xXX,XX}; CipherSuite TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 = {0xXX,XX}; CipherSuite TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256 = {0xXX,XX}; CipherSuite TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384 = {0xXX,XX};

This work was supported by the US Department of Defense. David McGrew, Pasi Eronen, and Alfred Hoenes provided reviews of this document.