draft-ietf-tls-rsa-aes-gcm-00.txt   draft-ietf-tls-rsa-aes-gcm-01.txt 
TLS Working Group J. Salowey TLS Working Group J. Salowey
Internet-Draft A. Choudhury Internet-Draft A. Choudhury
Intended status: Standards Track D. McGrew Intended status: Standards Track D. McGrew
Expires: December 20, 2007 Cisco Systems, Inc. Expires: July 16, 2008 Cisco Systems, Inc.
June 18, 2007 January 13, 2008
RSA based AES-GCM Cipher Suites for TLS RSA based AES-GCM Cipher Suites for TLS
draft-ietf-tls-rsa-aes-gcm-00 draft-ietf-tls-rsa-aes-gcm-01
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
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aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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This Internet-Draft will expire on December 20, 2007. This Internet-Draft will expire on July 16, 2008.
Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2008).
Abstract Abstract
This memo describes the use of the Advanced Encryption Standard (AES) This memo describes the use of the Advanced Encryption Standard (AES)
in Galois/Counter Mode (GCM) as a Transport Layer Security (TLS) in Galois/Counter Mode (GCM) as a Transport Layer Security (TLS)
authenticated encryption operation. GCM provides both authenticated encryption operation. GCM provides both
confidentiality and data origin authentication, can be efficiently confidentiality and data origin authentication, can be efficiently
implemented in hardware for speeds of 10 gigabits per second and implemented in hardware for speeds of 10 gigabits per second and
above, and is also well-suited to software implementations. This above, and is also well-suited to software implementations. This
memo defines TLS ciphersuites that use AES-GCM with RSA. memo defines TLS ciphersuites that use AES-GCM with RSA.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used In This Document . . . . . . . . . . . . . . . 3 2. Conventions Used In This Document . . . . . . . . . . . . . . . 3
3. RSA Based AES-GCM Cipher Suites . . . . . . . . . . . . . . . . 3 3. RSA Based AES-GCM Cipher Suites . . . . . . . . . . . . . . . . 3
3.1. Recommendations for Multiple Cryptographic Processors . . . 4
4. TLS Versions . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. TLS Versions . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
6.1. Perfect Forward Secrecy . . . . . . . . . . . . . . . . . . 6 6.1. Perfect Forward Secrecy . . . . . . . . . . . . . . . . . . 6
6.2. Counter Reuse . . . . . . . . . . . . . . . . . . . . . . . 6 6.2. Counter Reuse . . . . . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
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controllers (ACs) have to meet requirements to support higher controllers (ACs) have to meet requirements to support higher
throughputs in the future. AES-GCM has been specified as a mode that 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 can be used with IPsec ESP [RFC4106] and 802.1AE MAC Security
[IEEE8021AE]. It also is part of the NSA suite B ciphersuites for [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 TLS [I-D.rescorla-tls-suiteb]; however in order to meet Suite B
requirements these ciphersuites require ECC base key exchange and TLS requirements these ciphersuites require ECC base key exchange and TLS
1.2. The ciphersuites defined in this document are based on RSA 1.2. The ciphersuites defined in this document are based on RSA
which allows the use of AES-GCM in environments that have not which allows the use of AES-GCM in environments that have not
deployed ECC algorithms and do not need to meet NSA Suite B deployed ECC algorithms and do not need to meet NSA Suite B
requirements. AES-GCM is an authenticated encryption with associated requirements. AES-GCM is an authenticated encryption with associated
data (AEAD) operation, as used in TLS 1.2[I-D.ietf-tls-rfc4346-bis]. 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 DTLS defined The ciphersuites defined in this draft may be used with Datagram TLS
in [RFC4347] and [I-D.ietf-tls-ecc-new-mac]. This memo uses GCM in a defined in [RFC4347]. This memo uses GCM in a way similar to
way similar to [I-D.rescorla-tls-suiteb]. [I-D.ietf-tls-ecc-new-mac].
2. Conventions Used In This Document 2. Conventions Used In This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119] document are to be interpreted as described in [RFC2119]
3. RSA Based AES-GCM Cipher Suites 3. RSA Based AES-GCM Cipher Suites
The ciphersuites defined in this document are based on the the AES- The following ciphersuites use the new authenticated encryption modes
GCM authenticated encryption with associated data (AEAD) algorithms defined in TLS 1.2 with AES in Galois Counter Mode (GCM) [GCM]:
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_128_GCM_SHA256 = {TBD1,TBD1}
CipherSuite TLS_RSA_WITH_AES_256_GCM_SHA384 = {TBD2,TBD2} 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_128_GCM_SHA256 = {TBD3,TBD3}
CipherSuite TLS_RSA_DHE_WITH_AES_256_GCM_SHA384 = {TBD4,TBD4} CipherSuite TLS_RSA_DHE_WITH_AES_256_GCM_SHA384 = {TBD4,TBD4}
The "nonce" SHALL be 12 bytes long and it is "partially implicit" These ciphersuites use the AES-GCM authenticated encryption with
(see section 3.2.1 in [I-D.mcgrew-auth-enc]); that is, part of the associated data (AEAD) algorithms AEAD_AES_128_GCM and
nonce is explicitly carried in each packet, and part of the nonce is AEAD_AES_256_GCM described in [I-D.mcgrew-auth-enc]. Note that this
implicit. The nonce is constructed from a salt and an explicit specification uses a 128-bit authentication tag with GCM. The
Counter, sent as part of the packet, as follows: "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
generated as part of the handshake process and is static for the
entire session and part is carried in each packet.
Struct{ Struct{
opaque salt[4]; opaque salt[4];
opaque explicit_nonce_part[8]; opaque explicit_nonce_part[8];
} GCMNonce } GCMNonce
The salt is the "implicit" part of the nonce and is not sent in the 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 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 the server_write_IV if the server is sending. These IVs SHALL be 4
bytes long. bytes long.
The explicit_nonce_part is chosen by the sender and included in the 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 packet. Each value of the explicit_nonce_part MUST be distinct for
each distinct invocation of GCM encrypt function using a particular each distinct invocation of GCM encrypt function for any fixed key.
fixed key. Failure to meet this uniqueness requirement can Failure to meet this uniqueness requirement can significantly degrade
significantly degrade security. The explicit_nonce_part is carried security. The explicit_nonce_part is carried in the IV field of the
in the IV field of the GenericAEADCipher structure. Therefore, for GenericAEADCipher structure. Therefore, for all the algorithms
all the algorithms defined in this section, defined in this section, SecurityParameters.iv_length=8.
SecurityParameters.iv_length=8.
In the case of TLS the explicit_nonce_part MAY be the 64-bit sequence In the case of TLS the explicit_nonce_part MAY be the 64-bit sequence
number. In the case of DTLS the explicit_nonce_part MAY be the 16- number. In the case of Datagram TLS [RFC4347] the
bit epoch with the concatenated 48-bit DTLS seq_num. 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 If multiple cryptographic processors are in use by the sender, then
the sender MUST ensure that each value of the explicit_nonce_part the sender MUST ensure that each value of the explicit_nonce_part
that is used by each processor is distinct. In this case each that is used by each processor is distinct. In this case each
encryption processor SHOULD include in the explicit_nonce_part a a encryption processor SHOULD include in the explicit_nonce_part a a
fixed value that is distinct for each processor. The recommended fixed value that is distinct for each processor. The recommended
format is format is
explicit_nonce_part = FixedDistinct || Variable explicit_nonce_part = FixedDistinct || Variable
where the FixedDistinct field is distinct for each encryption where the FixedDistinct field is distinct for each encryption
processor, but is fixed for a given processor, and the Variable field processor, but is fixed for a given processor, and the Variable field
is distinct for each distinct nonce used by a particular encryption is distinct for each distinct nonce used by a particular encryption
processor. When this method is used, the FixedDistinct fields used processor. When this method is used, the FixedDistinct fields used
by the different processors MUST have the same length. 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 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 Fixed-Common part of the nonce (it is fixed, and it is common across
all encryption processors), the FixedDistinct field exactly all encryption processors), the FixedDistinct field exactly
corresponds to the Fixed-Distinct field, and the Variable field corresponds to the Fixed-Distinct field, and the Variable field
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The GCMnonces generated by the second encryption processor, and their The GCMnonces generated by the second encryption processor, and their
corresponding explicit_nonce_parts, are corresponding explicit_nonce_parts, are
GCMNonce explicit_nonce_part GCMNonce explicit_nonce_part
------------------------ ---------------------------- ------------------------ ----------------------------
eedc68dc0200000000000000 0200000000000000 eedc68dc0200000000000000 0200000000000000
eedc68dc0200000000000001 0200000000000001 eedc68dc0200000000000001 0200000000000001
eedc68dc0200000000000002 0200000000000002 eedc68dc0200000000000002 0200000000000002
... ...
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. 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.
4. TLS Versions 4. TLS Versions
These ciphersuites make use of the authenticated encryption with These ciphersuites make use of the authenticated encryption with
additional data defined in TLS 1.2 [I-D.ietf-tls-rfc4346-bis]. They 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 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. 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 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 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 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 server might potentially negotiate TLS 1.1 or earlier and select one
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IANA has assigned the following values for the ciphersuites defined IANA has assigned the following values for the ciphersuites defined
in this draft: in this draft:
CipherSuite TLS_RSA_WITH_AES_128_GCM_SHA256 = {TBD1,TBD1} CipherSuite TLS_RSA_WITH_AES_128_GCM_SHA256 = {TBD1,TBD1}
CipherSuite TLS_RSA_WITH_AES_256_GCM_SHA384 = {TBD2,TBD2} 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_128_GCM_SHA256 = {TBD3,TBD3}
CipherSuite TLS_RSA_DHE_WITH_AES_256_GCM_SHA384 = {TBD4,TBD4} CipherSuite TLS_RSA_DHE_WITH_AES_256_GCM_SHA384 = {TBD4,TBD4}
6. Security Considerations 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 6.1. Perfect Forward Secrecy
The perfect forward secrecy properties of RSA based TLS ciphersuites The perfect forward secrecy properties of RSA based TLS ciphersuites
are discussed in the security analysis of [RFC4346]. It should be are discussed in the security analysis of [I-D.ietf-tls-rfc4346-bis].
noted that only the ephemeral Diffie-Hellman based ciphersuites are It should be noted that only the ephemeral Diffie-Hellman based
capable of providing perfect forward secrecy. ciphersuites (RSA_DHE) are capable of providing perfect forward
secrecy.
6.2. Counter Reuse 6.2. Counter Reuse
AES-GCM security requires that the counter is never reused. The IV AES-GCM security requires that the counter is never reused. The IV
construction in Section 3 is designed to prevent counter reuse. construction in Section 3 is designed to prevent counter reuse.
7. Acknowledgements 7. Acknowledgements
This draft borrows heavily from [I-D.ietf-tls-ecc-new-mac] and This draft borrows heavily from [I-D.ietf-tls-ecc-new-mac].
[I-D.rescorla-tls-suiteb]
8. References 8. References
8.1. Normative References 8.1. Normative References
[AES] National Institute of Standards and Technology, [AES] National Institute of Standards and Technology,
"Specification for the Advanced Encryption Standard "Specification for the Advanced Encryption Standard
(AES)", FIPS 197, November 2001. (AES)", FIPS 197, November 2001.
[GCM] National Institute of Standards and Technology, [GCM] National Institute of Standards and Technology,
"Recommendation for Block Cipher Modes of Operation: "Recommendation for Block Cipher Modes of Operation:
Galois Counter Mode (GCM) for Confidentiality and Galois Counter Mode (GCM) for Confidentiality and
Authentication", SP 800-38D, April 2006. Authentication", SP 800-38D, April 2006.
[I-D.ietf-tls-rfc4346-bis] [I-D.ietf-tls-rfc4346-bis]
Dierks, T. and E. Rescorla, "The TLS Protocol Version Dierks, T. and E. Rescorla, "The Transport Layer Security
1.2", draft-ietf-tls-rfc4346-bis-03 (work in progress), (TLS) Protocol Version 1.2", draft-ietf-tls-rfc4346-bis-07
March 2007. (work in progress), November 2007.
[I-D.mcgrew-auth-enc] [I-D.mcgrew-auth-enc]
McGrew, D., "An Interface and Algorithms for Authenticated McGrew, D., "An Interface and Algorithms for Authenticated
Encryption", draft-mcgrew-auth-enc-02 (work in progress), Encryption", draft-mcgrew-auth-enc-05 (work in progress),
March 2007. November 2007.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.1", RFC 4346, April 2006. (TLS) Protocol Version 1.1", RFC 4346, April 2006.
[RFC4347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer [RFC4347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security", RFC 4347, April 2006. Security", RFC 4347, April 2006.
8.2. Informative References 8.2. Informative References
[I-D.ietf-tls-ecc-new-mac] [I-D.ietf-tls-ecc-new-mac]
Rescorla, E., "TLS Elliptic Curve Cipher Suites with SHA- Rescorla, E., "TLS Elliptic Curve Cipher Suites with SHA-
256/384 and AES Galois Counter Mode", 256/384 and AES Galois Counter Mode",
draft-ietf-tls-ecc-new-mac-01 (work in progress), draft-ietf-tls-ecc-new-mac-02 (work in progress),
June 2007. December 2007.
[I-D.rescorla-tls-suiteb] [I-D.rescorla-tls-suiteb]
Salter, M. and E. Rescorla, "Suite B Cipher Suites for Salter, M. and E. Rescorla, "Suite B Cipher Suites for
TLS", draft-rescorla-tls-suiteb-01 (work in progress), TLS", draft-rescorla-tls-suiteb-01 (work in progress),
June 2007. June 2007.
[IEEE8021AE] [IEEE8021AE]
Institute of Electrical and Electronics Engineers, "Media Institute of Electrical and Electronics Engineers, "Media
Access Control Security", IEEE Standard 802.1AE, Access Control Security", IEEE Standard 802.1AE,
August 2006. August 2006.
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David McGrew David McGrew
Cisco Systems, Inc. Cisco Systems, Inc.
170 W Tasman Drive 170 W Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
USA USA
Email: mcgrew@cisco.com Email: mcgrew@cisco.com
Full Copyright Statement Full Copyright Statement
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors contained in BCP 78, and except as set forth therein, the authors
retain all their rights. retain all their rights.
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
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