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TLS Working Group J. Salowey
Internet-Draft A. Choudhury
Intended status: Standards Track D. McGrew
Expires: August 29, 2007 Cisco Systems, Inc.
February 25, 2007
RSA based AES-GCM Cipher Suites for TLS
draft-salowey-tls-rsa-aes-gcm-00
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on August 29, 2007.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This memo describes the use of the Advanced Encryption Standard (AES)
in Galois/Counter Mode (GCM) as a Transport Layer Security (TLS)
authenticated encryption operation. GCM provides both
confidentiality and data origin authentication, can be efficiently
implemented in hardware for speeds of 10 gigabits per second and
above, and is also well-suited to software implementations. This
memo defines TLS ciphersuites that use AES-GCM with RSA.
Salowey, et al. Expires August 29, 2007 [Page 1]
Internet-Draft RSA AES-GCM Ciphersuites February 2007
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used In This Document . . . . . . . . . . . . . . . 3
3. RSA Based AES-GCM Cipher Suites . . . . . . . . . . . . . . . . 3
4. TLS Versions . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
6.1. Perfect Forward Secrecy . . . . . . . . . . . . . . . . . . 5
6.2. Counter Reuse . . . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
Intellectual Property and Copyright Statements . . . . . . . . . . 8
Salowey, et al. Expires August 29, 2007 [Page 2]
Internet-Draft RSA AES-GCM Ciphersuites February 2007
1. Introduction
This document describes the use of AES [AES]in Galois Counter Mode
(GCM) [GCM] (AES-GCM) with RSA based key exchange as a ciphersuite
for TLS. This mechanism is not only efficient and secure, hardware
implementations can achieve high speeds with low cost and low
latency, because the mode can be pipelined. Applications like
CAPWAP, which uses DTLS, can benefit from the high-speed
implementations when wireless termination points (WTPs) and
controllers (ACs) have to meet requirements to support higher
throughputs in the future. AES-GCM has been specified as a mode that
can be used with IPsec ESP [RFC4106] and 802.1AE MAC Security
[IEEE8021AE]. It also is part of the NSA suite B ciphersuites for
TLS [I-D.rescorla-tls-suiteb]; however in order to meet Suite B
requirements these ciphersuites require ECC base key exchange and TLS
1.2. The ciphersuites defined in this document are based on RSA
which allows the use of AES-GCM in environments that have not
deployed ECC algorithms and do not need to meet NSA Suite B
requirements. AES-GCM is an authenticated encryption with associated
data (AEAD) operation, as used in TLS 1.2[I-D.ietf-tls-rfc4346-bis].
The ciphersuites defined in this draft may be used with DTLS defined
in [RFC4347] and [I-D.ietf-tls-ctr]. This memo uses GCM in a way
similar to [I-D.rescorla-tls-suiteb].
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. RSA Based AES-GCM Cipher Suites
The ciphersuites defined in this document are based on the the AES-
GCM authenticated encryption with associated data (AEAD) algorithms
AEAD_AES_128_GCM and AEAD_AES_256_GCM described in
[I-D.mcgrew-auth-enc]. Note that this specification uses a 128-bit
authentication tag with GCM. The following ciphersuites are defined:
CipherSuite TLS_RSA_WITH_AES_128_GCM_SHA256 = {TBD1,TBD1}
CipherSuite TLS_RSA_WITH_AES_256_GCM_SHA384 = {TBD2,TBD2}
CipherSuite TLS_RSA_DHE_WITH_AES_128_GCM_SHA256 = {TBD3,TBD3}
CipherSuite TLS_RSA_DHE_WITH_AES_256_GCM_SHA384 = {TBD4,TBD4}
These ciphersuites make use of the AEAD capability in TLS 1.2
[I-D.ietf-tls-rfc4346-bis]. The "nonce" SHALL be 12 bytes long and
constructed from a salt and a counter as follows:
Salowey, et al. Expires August 29, 2007 [Page 3]
Internet-Draft RSA AES-GCM Ciphersuites February 2007
Struct{
uint32 salt;
uint64 counter;
} GCMNonce
The salt is derived form the TLS key block as follows:
struct {
case client:
uint32 client_write_IV; // low order 32-bits
case server:
uint32 server_write_IV; // low order 32-bits
} salt
In the case of TLS the counter is the 64 bit sequence number. In the
case of DTLS the counter is formed from the concatenation of the 16-
bit epoch with the 48-bit sequence number.
The RSA and RSA-DHE key exchange is performed as defined in
[I-D.ietf-tls-rfc4346-bis].
Recall that an AEAD operation replaces the use of HMAC as a MAC, but
not as a PRF for the purposes of key derivation. Consequently, the
hash function for the TLS PRF must be explicitly specified by the
ciphersuite. For TLS_RSA_WITH_AES_128_GCM_SHA256 and
TLS_RSA_DHE_WITH_AES_128_GCM_SHA256 the hash function is SHA256. For
TLS_RSA_WITH_AES_256_GCM_SHA384 and
TLS_RSA_DHE_WITH_AES_256_GCM_SHA384 the hash function is SHA384.
4. TLS Versions
These ciphersuites make use of the authenticated encryption with
additional data defined in TLS 1.2 [I-D.ietf-tls-rfc4346-bis]. They
MUST NOT be negotiated in older versions of TLS. Clients MUST NOT
offer these cipher suites if they do not offer TLS 1.2 or later.
Servers which select an earlier version of TLS MUST NOT select one of
these cipher suites. Because TLS has no way for the client to
indicate that it supports TLS 1.2 but not earlier, a non-compliant
server might potentially negotiate TLS 1.1 or earlier and select one
of the cipher suites in this document. Clients MUST check the TLS
version and generate a fatal "illegal_parameter" alert if they detect
an incorrect version.
Salowey, et al. Expires August 29, 2007 [Page 4]
Internet-Draft RSA AES-GCM Ciphersuites February 2007
5. IANA Considerations
IANA has assigned the following values for the ciphersuites defined
in this draft:
CipherSuite TLS_RSA_WITH_AES_128_GCM_SHA256 = {TBD1,TBD1}
CipherSuite TLS_RSA_WITH_AES_256_GCM_SHA384 = {TBD2,TBD2}
CipherSuite TLS_RSA_DHE_WITH_AES_128_GCM_SHA256 = {TBD3,TBD3}
CipherSuite TLS_RSA_DHE_WITH_AES_256_GCM_SHA384 = {TBD4,TBD4}
6. Security Considerations
6.1. Perfect Forward Secrecy
The perfect forward secrecy properties of RSA based TLS ciphersuites
are discussed in the security analysis of [RFC4346]. It should be
noted that only the ephemeral Diffie-Hellman based ciphersuites are
capable of providing perfect forward secrecy.
6.2. Counter Reuse
AES-GCM security requires that the counter is never reused. The IV
construction in Section 3 is designed to prevent counter reuse.
7. Acknowledgements
This draft borrows heavily from [I-D.ietf-tls-ctr] and
[I-D.rescorla-tls-suiteb]
8. References
8.1. Normative References
[AES] National Institute of Standards and Technology,
"Specification for the Advanced Encryption Standard
(AES)", FIPS 197, November 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, April 2006.
[I-D.ietf-tls-rfc4346-bis]
Dierks, T. and E. Rescorla, "The TLS Protocol Version
1.2", draft-ietf-tls-rfc4346-bis-02 (work in progress),
Salowey, et al. Expires August 29, 2007 [Page 5]
Internet-Draft RSA AES-GCM Ciphersuites February 2007
October 2006.
[I-D.mcgrew-auth-enc]
McGrew, D., "An Interface and Algorithms for Authenticated
Encryption", draft-mcgrew-auth-enc-01 (work in progress),
October 2006.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.1", RFC 4346, April 2006.
[RFC4347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security", RFC 4347, April 2006.
8.2. Informative References
[I-D.ietf-tls-ctr]
Modadugu, N. and E. Rescorla, "AES Counter Mode Cipher
Suites for TLS and DTLS", draft-ietf-tls-ctr-01 (work in
progress), June 2006.
[I-D.rescorla-tls-suiteb]
Salter, M. and E. Rescorla, "SuiteB CipherSuites for TLS",
draft-rescorla-tls-suiteb-00 (work in progress),
December 2006.
[IEEE8021AE]
Institute of Electrical and Electronics Engineers, "Media
Access Control Security", IEEE Standard 802.1AE,
August 2006.
[RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
RFC 2246, January 1999.
[RFC4106] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode
(GCM) in IPsec Encapsulating Security Payload (ESP)",
RFC 4106, June 2005.
Salowey, et al. Expires August 29, 2007 [Page 6]
Internet-Draft RSA AES-GCM Ciphersuites February 2007
Authors' Addresses
Joseph Salowey
Cisco Systems, Inc.
2901 3rd. Ave
Seattle, WA 98121
USA
Email: jsalowey@cisco.com
Abhijit Choudhury
Cisco Systems, Inc.
170 W Tasman Drive
San Jose, CA 95134
USA
Email: abhijitc@cisco.com
David McGrew
Cisco Systems, Inc.
170 W Tasman Drive
San Jose, CA 95134
USA
Email: mcgrew@cisco.com
Salowey, et al. Expires August 29, 2007 [Page 7]
Internet-Draft RSA AES-GCM Ciphersuites February 2007
Full Copyright Statement
Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
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Salowey, et al. Expires August 29, 2007 [Page 8]
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