TLS Working Group Mohamad Badra
Internet Draft LIMOS Laboratory
Intended status: Standards Track May 29, 2008
Expires: November 2008
Pre-Shared Key Cipher Suites for Transport Layer Security (TLS) with
SHA-256/384 and AES Galois Counter Mode
draft-ietf-tls-psk-new-mac-aes-gcm-01.txt
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Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
RFC 4279 and RFC 4785 describe pre-shared key cipher suites for
Transport Layer Security (TLS). However, all those cipher suites
use SHA-1 as their MAC algorithm. This document describes a set of
cipher suites for TLS/DTLS which uses stronger digest algorithms
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(i.e., SHA-256 or SHA-384) and another which uses the Advanced
Encryption Standard (AES) in Galois Counter Mode (GCM).
Table of Contents
1. Introduction...................................................3
1.1. Conventions used in this document.........................3
2. PSK, DHE_PSK and RSA_PSK Key Exchange Algorithms with AES-GCM..3
3. PSK, DHE_PSK and RSA_PSK Key Exchange with SHA-256/384.........4
3.1. PSK Key Exchange Algorithm with SHA-256/384...............4
3.2. DHE_PSK Key Exchange Algorithm with SHA-256/384...........5
3.3. RSA_PSK Key Exchange Algorithm with SHA-256/384...........5
4. Security Considerations........................................5
5. IANA Considerations............................................5
6. Acknowledgments................................................6
7. References.....................................................6
7.1. Normative References......................................6
7.2. Informative References....................................7
Author's Addresses................................................7
Intellectual Property and Copyright Statements....................8
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1. Introduction
TLS 1.2 [I-D.ietf-tls-rfc4346-bis], adds support for authenticated
encryption with additional data (AEAD) cipher modes [RFC5116]. This
document describes the use of Advanced Encryption Standard (AES)
[AES] in Galois Counter Mode (GCM) [GCM] (AES-GCM) with various pre-
shared key (PSK) key exchange mechanisms ([RFC4279] and [RFC4785])
as a cipher suite for Transport Layer Security (TLS).
This document also specifies PSK cipher suites for TLS which replace
SHA-1 by SHA-256 or SHA-384 [SHS]. RFC 4279 [RFC4279] and RFC 4785
[RFC4785] describe PSK cipher suites for TLS. However, all of the
RFC 4279 and the RFC 4785 cipher 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.
ECC based cipher suites with SHA-256/384 and AES-GCM are defined in
[I-D.ietf-tls-ecc-new-mac]; RSA, DSS and Diffie-Hellman based cipher
suites are specified in [I-D.ietf-tls-rsa-aes-gcm]. The reader is
expected to become familiar with these two memos prior to studying
this document.
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].
2. PSK, DHE_PSK and RSA_PSK Key Exchange Algorithms with AES-GCM
The following eight cipher suites use the new authenticated
encryption modes defined in TLS 1.2 with AES in Galois Counter Mode
(GCM) [GCM]. The cipher suites with DHE_PSK key exchange algorithm
(TLS_DHE_PSK_WITH_AES_128_GCM_SHA256 and
TLS_DHE_PSK_WITH_AES_128_GCM_SHA348) provide Perfect Forward Secrecy
(PFS).
CipherSuite TLS_PSK_WITH_AES_128_GCM_SHA256 = {0xXX,0xXX};
CipherSuite TLS_PSK_WITH_AES_258_GCM_SHA256 = {0xXX,0xXX};
CipherSuite TLS_PSK_WITH_AES_128_GCM_SHA384 = {0xXX,0xXX};
CipherSuite TLS_PSK_WITH_AES_256_GCM_SHA384 = {0xXX,0xXX};
CipherSuite TLS_DHE_PSK_WITH_AES_128_GCM_SHA256 = {0xXX,0xXX};
CipherSuite TLS_DHE_PSK_WITH_AES_256_GCM_SHA256 = {0xXX,0xXX};
CipherSuite TLS_RSA_PSK_WITH_AES_128_GCM_SHA384 = {0xXX,0xXX};
CipherSuite TLS_RSA_PSK_WITH_AES_256_GCM_SHA384 = {0xXX,0xXX};
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These cipher suites use authenticated encryption with additional
data (AEAD) algorithms AEAD_AES_128_GCM and AEAD_AES_256_GCM
described in RFC 5116. GCM is used as described in [I-D.ietf-tls-
rsa-aes-gcm].
The PSK, DHE_PSK and RSA_PSK key exchanges are performed as defined
in [RFC4279].
The PRFs SHALL be as follows:
For cipher suites ending with _SHA256, the PRF is the TLS PRF
[I-D.ietf-tls-rfc4346-bis] with SHA-256 as the hash function.
For cipher suites ending with _SHA384, the PRF is the TLS PRF
[I-D.ietf-tls-rfc4346-bis] with SHA-384 as the hash function.
Implementations MUST send TLS Alert bad_record_mac for all types of
failures encountered in processing the AES-GCM algorithm.
3. PSK, DHE_PSK and RSA_PSK Key Exchange with SHA-256/384
The cipher suites described in this section use AES [AES] in CBC
[CBC] mode with an HMAC-based MAC.
3.1. PSK Key Exchange Algorithm with SHA-256/384
CipherSuite TLS_PSK_WITH_AES_128_CBC_SHA256 = {0xXX,0xXX};
CipherSuite TLS_PSK_WITH_AES_256_CBC_SHA256 = {0xXX,0xXX};
CipherSuite TLS_PSK_WITH_AES_128_CBC_SHA384 = {0xXX,0xXX};
CipherSuite TLS_PSK_WITH_AES_256_CBC_SHA384 = {0xXX,0xXX};
CipherSuite TLS_PSK_WITH_NULL_SHA256 = {0xXX,0xXX};
CipherSuite TLS_PSK_WITH_NULL_SHA384 = {0xXX,0xXX};
The above six cipher suites are the same as the corresponding cipher
suites in RFC 4279 and RFC 4785 (with names ending in "_SHA" in
place of "_SHA256" or "_SHA384"), except for the hash and PRF
algorithms.
The PRF and MAC algorithms SHALL be as follows:
For cipher suites ending with _SHA256, the PRF is the TLS PRF
[I-D.ietf-tls-rfc4346-bis] with SHA-256 as the hash function.
The MAC is HMAC [RFC2104] with SHA-256 as the hash function.
For cipher suites ending with _SHA384, the PRF is the TLS PRF
[I-D.ietf-tls-rfc4346-bis] with SHA-384 as the hash function.
The MAC is HMAC [RFC2104] with SHA-384 as the hash function.
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3.2. DHE_PSK Key Exchange Algorithm with SHA-256/384
CipherSuite TLS_DHE_PSK_WITH_AES_128_CBC_SHA256 = {0xXX,0xXX};
CipherSuite TLS_DHE_PSK_WITH_AES_256_CBC_SHA256 = {0xXX,0xXX};
CipherSuite TLS_DHE_PSK_WITH_AES_128_CBC_SHA384 = {0xXX,0xXX};
CipherSuite TLS_DHE_PSK_WITH_AES_256_CBC_SHA384 = {0xXX,0xXX};
CipherSuite TLS_DHE_PSK_WITH_NULL_SHA256 = {0xXX,0xXX};
CipherSuite TLS_DHE_PSK_WITH_NULL_SHA384 = {0xXX,0xXX};
The above six cipher suites are the same as the corresponding cipher
suites in RFC 4279 and RFC 4785 (with names ending in "_SHA" in
place of "_SHA256" or "_SHA384"), except for the hash and PRF
algorithms, as explained in section 3.1.
3.3. RSA_PSK Key Exchange Algorithm with SHA-256/384
CipherSuite TLS_RSA_PSK_WITH_AES_128_CBC_SHA256 = {0xXX,0xXX};
CipherSuite TLS_RSA_PSK_WITH_AES_256_CBC_SHA256 = {0xXX,0xXX};
CipherSuite TLS_RSA_PSK_WITH_AES_128_CBC_SHA384 = {0xXX,0xXX};
CipherSuite TLS_RSA_PSK_WITH_AES_256_CBC_SHA384 = {0xXX,0xXX};
The above four cipher suites are the same as the corresponding
cipher suites in RFC 4279 and RFC 4785 (with names ending in "_SHA"
in place of "_SHA256" or "_SHA384"), except for the hash and PRF
algorithms, as explained in section 3.1.
4. Security Considerations
The security considerations in RFC 4279, RFC 4758, and [I-D.ietf-
tls-rsa-aes-gcm] apply to this document as well. In addition, as
described in [I-D.ietf-tls-rsa-aes-gcm], these cipher suites may
only be used with TLS 1.2 or greater.
5. IANA Considerations
IANA has assigned the following values for the cipher suites defined
in this document:
CipherSuite TLS_PSK_WITH_AES_128_GCM_SHA256 = {0xXX,0xXX};
CipherSuite TLS_PSK_WITH_AES_258_GCM_SHA256 = {0xXX,0xXX};
CipherSuite TLS_PSK_WITH_AES_128_GCM_SHA384 = {0xXX,0xXX};
CipherSuite TLS_PSK_WITH_AES_256_GCM_SHA384 = {0xXX,0xXX};
CipherSuite TLS_DHE_PSK_WITH_AES_128_GCM_SHA256 = {0xXX,0xXX};
CipherSuite TLS_DHE_PSK_WITH_AES_256_GCM_SHA256 = {0xXX,0xXX};
CipherSuite TLS_RSA_PSK_WITH_AES_128_GCM_SHA384 = {0xXX,0xXX};
CipherSuite TLS_RSA_PSK_WITH_AES_256_GCM_SHA384 = {0xXX,0xXX};
CipherSuite TLS_PSK_WITH_AES_128_CBC_SHA256 = {0xXX,0xXX};
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CipherSuite TLS_PSK_WITH_AES_256_CBC_SHA256 = {0xXX,0xXX};
CipherSuite TLS_PSK_WITH_AES_128_CBC_SHA384 = {0xXX,0xXX};
CipherSuite TLS_PSK_WITH_AES_256_CBC_SHA384 = {0xXX,0xXX};
CipherSuite TLS_PSK_WITH_NULL_SHA256 = {0xXX,0xXX};
CipherSuite TLS_PSK_WITH_NULL_SHA384 = {0xXX,0xXX};
CipherSuite TLS_DHE_PSK_WITH_AES_128_CBC_SHA256 = {0xXX,0xXX};
CipherSuite TLS_DHE_PSK_WITH_AES_256_CBC_SHA256 = {0xXX,0xXX};
CipherSuite TLS_DHE_PSK_WITH_AES_128_CBC_SHA384 = {0xXX,0xXX};
CipherSuite TLS_DHE_PSK_WITH_AES_256_CBC_SHA384 = {0xXX,0xXX};
CipherSuite TLS_DHE_PSK_WITH_NULL_SHA256 = {0xXX,0xXX};
CipherSuite TLS_DHE_PSK_WITH_NULL_SHA384 = {0xXX,0xXX};
CipherSuite TLS_RSA_PSK_WITH_AES_128_CBC_SHA256 = {0xXX,0xXX};
CipherSuite TLS_RSA_PSK_WITH_AES_256_CBC_SHA256 = {0xXX,0xXX};
CipherSuite TLS_RSA_PSK_WITH_AES_128_CBC_SHA384 = {0xXX,0xXX};
CipherSuite TLS_RSA_PSK_WITH_AES_256_CBC_SHA384 = {0xXX,0xXX};
6. Acknowledgments
This draft borrows heavily from [I-D.ietf-tls-ecc-new-mac] and [I-
D.ietf-tls-rsa-aes-gcm].
The author appreciates Alfred Hoenes for his detailed review and
effort on issues resolving discussion. The author would like also
to acknowledge Ibrahim Hajjeh, Simon Josefsson, Hassnaa Moustafa,
Joseph Salowey and Pascal Urien for their reviews of the content of
the document.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[I-D.ietf-tls-rfc4346-bis]
Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", draft-ietf-tls-rfc4346-bis-
10, work in progress, March 2008.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104, February
1997.
[RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated
Encryption", RFC 5116, January 2008.
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[RFC4279] Eronen, P. and H. Tschofenig, "Pre-Shared Key Ciphersuites
for Transport Layer Security (TLS)", RFC 4279, December
2005.
[RFC4785] Blumenthal, U., Goel, P., "Pre-Shared Key (PSK)
Ciphersuites with NULL Encryption for Transport Layer
Security (TLS)", RFC 4785, January 2007.
[AES] National Institute of Standards and Technology,
"Specification for the Advanced Encryption Standard
(AES)", FIPS 197, November 2001.
[SHS] National Institute of Standards and Technology, "Secure
Hash Standard", FIPS 180-2, August 2002.
[CBC] National Institute of Standards and Technology,
"Recommendation for Block Cipher Modes of Operation -
Methods and Techniques", SP 800-38A, December 2001.
[GCM] National Institute of Standards and Technology,
"Recommendation for Block Cipher Modes of Operation:
Galois/Counter Mode (GCM) for Confidentiality and
Authentication", SP 800-38D, November 2007.
[I-D.ietf-tls-rsa-aes-gcm]
Salowey, J., A. Choudhury, and C. McGrew, "RSA based AES-
GCM Cipher Suites for TLS", draft-ietf-tls-rsa-aes-gcm-03
(work in progress), April 2008.
7.2. Informative References
[Wang05] Wang, X., Yin, Y., and H. Yu, "Finding Collisions in the
Full SHA-1", CRYPTO 2005, August 2005.
[I-D.ietf-tls-ecc-new-mac]
Rescorla, E., "TLS Elliptic Curve Cipher Suites with SHA-
256/384 and AES Galois Counter Mode", draft-ietf-tls-ecc-
new-mac-07 (work in progress), May 2008.
Author's Addresses
Mohamad Badra
LIMOS Laboratory - UMR6158, CNRS
France
Email: badra@isima.fr
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