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Versions: (draft-badra-tls-psk-new-mac-aes-gcm)
00 01 02 03 04 05 RFC 5487
TLS Working Group Mohamad Badra
Internet Draft LIMOS Laboratory
Intended status: Standards Track October 31, 2008
Expires: April 2009
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-05.txt
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This Internet-Draft will expire on April 31, 2009.
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
pre-shared key cipher suites for TLS which uses stronger digest
algorithms (i.e., SHA-256 or SHA-384) and another set which uses the
Advanced Encryption Standard (AES) in Galois Counter Mode (GCM).
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Table of Contents
1. Introduction...................................................3
1.1. Applicability Statement...................................3
1.2. Conventions used in this document.........................4
2. PSK, DHE_PSK and RSA_PSK Key Exchange Algorithms with AES-GCM..4
3. PSK, DHE_PSK and RSA_PSK Key Exchange with SHA-256/384.........4
3.1. PSK Key Exchange Algorithm with SHA-256/384...............5
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........................................6
5. IANA Considerations............................................6
6. Acknowledgments................................................7
7. References.....................................................7
7.1. Normative References......................................7
7.2. Informative References....................................8
Author's Addresses................................................8
Intellectual Property Statement...................................8
Disclaimer of Validity............................................9
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1. Introduction
The benefits of pre-shared symmetric-key vs. public-/private-key
pair based authentication for the key exchange in TLS have been
explained in the Introduction of [RFC4279]. This document leverages
the already defined algorithms for the application of newer,
generally regarded stronger, cryptographic primitives and building
blocks.
TLS 1.2 [RFC5246] 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) authenticated key exchange mechanisms ([RFC4279] and
[RFC4785]) in cipher suites 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.
Related TLS cipher suites with key exchange algorithms that are
authenticated using public/private key pairs have recently been
specified:
- RSA, DSS, and Diffie-Hellman based cipher suites in [RFC5288],
and
- ECC based cipher suites with SHA-256/384 and AES-GCM in
[RFC5289].
The reader is expected to become familiar with these two memos prior
to studying this document.
1.1. Applicability Statement
The cipher suites defined in Section 3 can be negotiated, whatever
the negotiated TLS version is.
The cipher suites defined in Section 2 can be negotiated in TLS
version 1.2 or higher.
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1.2. 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].
2. PSK, DHE_PSK and RSA_PSK Key Exchange Algorithms with AES-GCM
The following six 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_256_GCM_SHA348) provide Perfect Forward Secrecy
(PFS).
CipherSuite TLS_PSK_WITH_AES_128_GCM_SHA256 = {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_SHA384 = {0xXX,0xXX};
CipherSuite TLS_RSA_PSK_WITH_AES_128_GCM_SHA256 = {0xXX,0xXX};
CipherSuite TLS_RSA_PSK_WITH_AES_256_GCM_SHA384 = {0xXX,0xXX};
These cipher suites use authenticated encryption with additional
data (AEAD) algorithms AEAD_AES_128_GCM and AEAD_AES_256_GCM as
described in RFC 5116. GCM is used as described in [RFC5288].
The PSK, DHE_PSK and RSA_PSK key exchanges are performed as defined
in [RFC4279].
The Pseudo Random Function (PRF) algorithms SHALL be as follows:
For cipher suites ending with _SHA256, the PRF is the TLS PRF
[RFC5246] with SHA-256 as the hash function.
For cipher suites ending with _SHA384, the PRF is the TLS PRF
[RFC5246] with SHA-384 as the hash function.
Implementations MUST send a 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 first two cipher suites described in each of the following three
sections use AES [AES] in Cipher Block Chaining (CBC) mode [CBC] for
data confidentiality, whereas the other two cipher suites do not
provide data confidentiality; all cipher suites provide integrity
protection and authentication using HMAC-based MACs.
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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_SHA384 = {0xXX,0xXX};
CipherSuite TLS_PSK_WITH_NULL_SHA256 = {0xXX,0xXX};
CipherSuite TLS_PSK_WITH_NULL_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:
o For cipher suites with names ending in "_SHA256":
- The MAC is HMAC [RFC2104] with SHA-256 as the hash
function.
- When negotiated in a version of TLS prior to 1.2, the PRF
from that version is used; otherwise the PRF is the TLS
PRF [RFC5246] with SHA-256 as the hash function.
o For cipher suites with names ending in "_SHA384":
- The MAC is HMAC [RFC2104] with SHA-384 as the hash
function.
- When negotiated in a version of TLS prior to 1.2, the PRF
from that version is used; otherwise the PRF is the TLS
PRF [RFC5246] with SHA-384 as the hash function.
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_SHA384 = {0xXX,0xXX};
CipherSuite TLS_DHE_PSK_WITH_NULL_SHA256 = {0xXX,0xXX};
CipherSuite TLS_DHE_PSK_WITH_NULL_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.
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_SHA384 = {0xXX,0xXX};
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CipherSuite TLS_RSA_PSK_WITH_NULL_SHA256 = {0xXX,0xXX};
CipherSuite TLS_RSA_PSK_WITH_NULL_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 [RFC4279], [RFC4785] and [RFC5288]
apply to this document as well. In particular, as authentication-
only cipher suites (with no encryption) defined here do not support
confidentiality, care should be taken not to send sensitive
information (such as passwords) over connections protected with one
of the cipher suites with NULL encryption defined in this document.
As described in [RFC5288], the cipher suites defined in the Section
2 of this document may only be used with TLS 1.2 or greater. The
cipher suites defined in the Section 3 may be used, whatever the
negotiated TLS version is.
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_256_GCM_SHA384 = {0xXX,0xXX};
CipherSuite TLS_DHE_PSK_WITH_AES_128_GCM_SHA256 = {0xXX,0xXX};
CipherSuite TLS_DHE_PSK_WITH_AES_256_GCM_SHA384 = {0xXX,0xXX};
CipherSuite TLS_RSA_PSK_WITH_AES_128_GCM_SHA256 = {0xXX,0xXX};
CipherSuite TLS_RSA_PSK_WITH_AES_256_GCM_SHA384 = {0xXX,0xXX};
CipherSuite TLS_PSK_WITH_AES_128_CBC_SHA256 = {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_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_SHA384 = {0xXX,0xXX};
CipherSuite TLS_RSA_PSK_WITH_NULL_SHA256 = {0xXX,0xXX};
CipherSuite TLS_RSA_PSK_WITH_NULL_SHA384 = {0xXX,0xXX};
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6. Acknowledgments
This draft borrows heavily from [RFC5289] and [RFC5288].
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
[AES] National Institute of Standards and Technology,
"Specification for the Advanced Encryption Standard
(AES)", FIPS 197, November 2001.
[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.
[SHS] National Institute of Standards and Technology, "Secure
Hash Standard", FIPS 180-2, August 2002.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104, February
1997.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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.
[RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated
Encryption", RFC 5116, January 2008.
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[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC5288] Salowey, J., A. Choudhury, and C. McGrew, "RSA based AES-
GCM Cipher Suites for TLS", RFC 5288, August 2008.
7.2. Informative References
[RFC5289] Rescorla, E., "TLS Elliptic Curve Cipher Suites with SHA-
256/384 and AES Galois Counter Mode", RFC 5289, August
2008.
[Wang05] Wang, X., Yin, Y., and H. Yu, "Finding Collisions in the
Full SHA-1", CRYPTO 2005, August 2005.
Author's Addresses
Mohamad Badra
LIMOS Laboratory - UMR6158, CNRS
France
Email: badra@isima.fr
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Acknowledgment
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