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.
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).
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.
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.
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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.
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]:
[Wang05] Wang, X., Yin, Y., and H. Yu, "Finding Collisions in the Full SHA-1", CRYPTO 2005, August 2005.
Eric Rescorla RTFM, Inc. 2064 Edgewood Drive Palo Alto 94303 USA
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RFC 5289 TLS ECC New MAC August 2008
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