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+
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+
+TLS Working Group J. Salowey
+Internet-Draft A. Choudhury
+Intended status: Standards Track D. McGrew
+Expires: July 16, 2008 Cisco Systems, Inc.
+ January 13, 2008
+
+
+ RSA based AES-GCM Cipher Suites for TLS
+ draft-ietf-tls-rsa-aes-gcm-01
+
+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
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+
+ The list of Internet-Draft Shadow Directories can be accessed at
+ http://www.ietf.org/shadow.html.
+
+ This Internet-Draft will expire on July 16, 2008.
+
+Copyright Notice
+
+ Copyright (C) The IETF Trust (2008).
+
+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.
+
+
+
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+Internet-Draft RSA AES-GCM Ciphersuites January 2008
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+
+Table of Contents
+
+ 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
+
+ 2. Conventions Used In This Document . . . . . . . . . . . . . . . 3
+
+ 3. RSA Based AES-GCM Cipher Suites . . . . . . . . . . . . . . . . 3
+ 3.1. Recommendations for Multiple Cryptographic Processors . . . 4
+
+ 4. TLS Versions . . . . . . . . . . . . . . . . . . . . . . . . . 5
+
+ 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
+
+ 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
+ 6.1. Perfect Forward Secrecy . . . . . . . . . . . . . . . . . . 6
+ 6.2. Counter Reuse . . . . . . . . . . . . . . . . . . . . . . . 6
+
+ 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
+
+ 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
+ 8.1. Normative References . . . . . . . . . . . . . . . . . . . 7
+ 8.2. Informative References . . . . . . . . . . . . . . . . . . 7
+
+ Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
+ Intellectual Property and Copyright Statements . . . . . . . . . . 9
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+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) cipher, as defined in TLS 1.2[I-D.ietf-tls-rfc4346-bis].
+ The ciphersuites defined in this draft may be used with Datagram TLS
+ defined in [RFC4347]. This memo uses GCM in a way similar to
+ [I-D.ietf-tls-ecc-new-mac].
+
+
+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 following ciphersuites use the new authenticated encryption modes
+ defined in TLS 1.2 with AES in Galois Counter Mode (GCM) [GCM]:
+
+ 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 use 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
+ "nonce" SHALL be 12 bytes long and it is "partially implicit" (see
+ section 3.2.1 in [I-D.mcgrew-auth-enc]). Part of the nonce is
+
+
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+ generated as part of the handshake process and is static for the
+ entire session and part is carried in each packet.
+
+ Struct{
+ opaque salt[4];
+ opaque explicit_nonce_part[8];
+ } GCMNonce
+
+ The salt is the "implicit" part of the nonce and is not sent in the
+ packet. It is either the client_write_IV if the client is sending or
+ the server_write_IV if the server is sending. These IVs SHALL be 4
+ bytes long.
+
+ The explicit_nonce_part is chosen by the sender and included in the
+ packet. Each value of the explicit_nonce_part MUST be distinct for
+ each distinct invocation of GCM encrypt function for any fixed key.
+ Failure to meet this uniqueness requirement can significantly degrade
+ security. The explicit_nonce_part is carried in the IV field of the
+ GenericAEADCipher structure. Therefore, for all the algorithms
+ defined in this section, SecurityParameters.iv_length=8.
+
+ In the case of TLS the explicit_nonce_part MAY be the 64-bit sequence
+ number. In the case of Datagram TLS [RFC4347] the
+ explicit_nonce_part MAY be formed from the concatenation of the 16-
+ bit epoch with the 48-bit DTLS seq_num.
+
+ The RSA and RSA-DHE key exchange is performed as defined in
+ [I-D.ietf-tls-rfc4346-bis].
+
+ The PRF algorithms SHALL be as follows:
+
+ 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.
+
+3.1. Recommendations for Multiple Cryptographic Processors
+
+ If multiple cryptographic processors are in use by the sender, then
+ the sender MUST ensure that each value of the explicit_nonce_part
+ that is used by each processor is distinct. In this case each
+ encryption processor SHOULD include in the explicit_nonce_part a a
+ fixed value that is distinct for each processor. The recommended
+ format is
+
+ explicit_nonce_part = FixedDistinct || Variable
+
+
+
+
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+ where the FixedDistinct field is distinct for each encryption
+ processor, but is fixed for a given processor, and the Variable field
+ is distinct for each distinct nonce used by a particular encryption
+ processor. When this method is used, the FixedDistinct fields used
+ by the different processors MUST have the same length.
+
+ In the terms of Figure 2 in [I-D.mcgrew-auth-enc], the Salt is the
+ Fixed-Common part of the nonce (it is fixed, and it is common across
+ all encryption processors), the FixedDistinct field exactly
+ corresponds to the Fixed-Distinct field, and the Variable field
+ corresponds to the Counter field, and the explicit part exactly
+ corresponds to the explicit_nonce_part.
+
+ For clarity, we provide an example for TLS in which there are two
+ distinct encryption processors, each of which uses a one-byte
+ FixedDistinct field:
+
+ Salt = eedc68dc
+ FixedDistinct = 01 (for the first encryption processor)
+ FixedDistinct = 02 (for the second encryption processor)
+
+ The GCMnonces generated by the first encryption processor, and their
+ corresponding explicit_nonce_parts, are:
+
+ GCMNonce explicit_nonce_part
+ ------------------------ ----------------------------
+ eedc68dc0100000000000000 0100000000000000
+ eedc68dc0100000000000001 0100000000000001
+ eedc68dc0100000000000002 0100000000000002
+ ...
+
+ The GCMnonces generated by the second encryption processor, and their
+ corresponding explicit_nonce_parts, are
+
+ GCMNonce explicit_nonce_part
+ ------------------------ ----------------------------
+ eedc68dc0200000000000000 0200000000000000
+ eedc68dc0200000000000001 0200000000000001
+ eedc68dc0200000000000002 0200000000000002
+ ...
+
+
+
+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
+
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+ 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.
+
+
+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
+
+ The security considerations in [I-D.ietf-tls-rfc4346-bis] apply to
+ this document as well. The remainder of this section describes
+ security considerations specific to the cipher suites described in
+ this document.
+
+6.1. Perfect Forward Secrecy
+
+ The perfect forward secrecy properties of RSA based TLS ciphersuites
+ are discussed in the security analysis of [I-D.ietf-tls-rfc4346-bis].
+ It should be noted that only the ephemeral Diffie-Hellman based
+ ciphersuites (RSA_DHE) 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-ecc-new-mac].
+
+
+8. References
+
+
+
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+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 Transport Layer Security
+ (TLS) Protocol Version 1.2", draft-ietf-tls-rfc4346-bis-07
+ (work in progress), November 2007.
+
+ [I-D.mcgrew-auth-enc]
+ McGrew, D., "An Interface and Algorithms for Authenticated
+ Encryption", draft-mcgrew-auth-enc-05 (work in progress),
+ November 2007.
+
+ [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-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-02 (work in progress),
+ December 2007.
+
+ [I-D.rescorla-tls-suiteb]
+ Salter, M. and E. Rescorla, "Suite B Cipher Suites for
+ TLS", draft-rescorla-tls-suiteb-01 (work in progress),
+ June 2007.
+
+ [IEEE8021AE]
+ Institute of Electrical and Electronics Engineers, "Media
+ Access Control Security", IEEE Standard 802.1AE,
+ August 2006.
+
+
+
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+ [RFC4106] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode
+ (GCM) in IPsec Encapsulating Security Payload (ESP)",
+ RFC 4106, June 2005.
+
+
+Authors' Addresses
+
+ Joseph Salowey
+ Cisco Systems, Inc.
+ 2901 3rd. Ave
+ Seattle, WA 98121
+ USA
+
+ Email: jsalowey@cisco.com
+
+
+ Abhijit Choudhury
+ Cisco Systems, Inc.
+ 3625 Cisco Way
+ 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
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+Full Copyright Statement
+
+ Copyright (C) The IETF Trust (2008).
+
+ 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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+Acknowledgment
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+
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