draft-ietf-tls-ciphersuite-04.txt   draft-ietf-tls-ciphersuite-05.txt 
Network Working Group Pete Chown Network Working Group Pete Chown
INTERNET DRAFT Skygate Technology INTERNET DRAFT Skygate Technology
<draft-ietf-tls-ciphersuite-04.txt> 5 July 2001 <draft-ietf-tls-ciphersuite-05.txt> 14 August 2001
AES Ciphersuites for TLS AES Ciphersuites for TLS
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
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claims. RSA Security Inc has trademark rights in the names RC2 claims. RSA Security Inc has trademark rights in the names RC2
and RC4, and claims that the RC4 algorithm itself is a trade and RC4, and claims that the RC4 algorithm itself is a trade
secret. Ascom Systec Ltd owns a patent on the IDEA algorithm. secret. Ascom Systec Ltd owns a patent on the IDEA algorithm.
2. Triple DES is much less efficient than more modern ciphers. 2. Triple DES is much less efficient than more modern ciphers.
3. Now the AES process is completed there will be commercial pres¡ 3. Now the AES process is completed there will be commercial pres¡
sure to use the selected cipher. The AES is efficient and has sure to use the selected cipher. The AES is efficient and has
withstood extensive cryptanalytic efforts. The AES is withstood extensive cryptanalytic efforts. The AES is
ietf-tls-ciphersuite-04 AES Ciphersuites for TLS 5 July 2001 ietf-tls-ciphersuite-05 AES Ciphersuites for TLS 14 August 2001
therefore a desirable choice. therefore a desirable choice.
4. Currently the DHE ciphersuites only allow triple DES (along 4. Currently the DHE ciphersuites only allow triple DES (along
with some ``export'' variants which do not use a satisfactory with some ``export'' variants which do not use a satisfactory
key length). At the same time the DHE ciphersuites are the key length). At the same time the DHE ciphersuites are the
only ones to offer forward secrecy. only ones to offer forward secrecy.
This document proposes several new ciphersuites, with the aim of This document proposes several new ciphersuites, with the aim of
overcoming these problems. overcoming these problems.
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All the ciphersuites described here use the AES in cipher block All the ciphersuites described here use the AES in cipher block
chaining (CBC) mode. Furthermore, they use SHA-1 [SHA-1] in an chaining (CBC) mode. Furthermore, they use SHA-1 [SHA-1] in an
HMAC construction as described in section 5 of [TLS]. (Although HMAC construction as described in section 5 of [TLS]. (Although
the TLS ciphersuite names include the text ``SHA'', this actually the TLS ciphersuite names include the text ``SHA'', this actually
refers to the modified SHA-1 version of the algorithm.) refers to the modified SHA-1 version of the algorithm.)
The ciphersuites differ in the type of certificate and key exchange The ciphersuites differ in the type of certificate and key exchange
method. The ciphersuites defined here use the following options method. The ciphersuites defined here use the following options
for this part of the protocol: for this part of the protocol:
ietf-tls-ciphersuite-04 AES Ciphersuites for TLS 5 July 2001 ietf-tls-ciphersuite-05 AES Ciphersuites for TLS 14 August 2001
CipherSuite Certificate type (if applicable) CipherSuite Certificate type (if applicable)
and key exchange algorithm and key exchange algorithm
TLS_RSA_WITH_AES_128_CBC_SHA RSA TLS_RSA_WITH_AES_128_CBC_SHA RSA
TLS_DH_DSS_WITH_AES_128_CBC_SHA DH_DSS TLS_DH_DSS_WITH_AES_128_CBC_SHA DH_DSS
TLS_DH_RSA_WITH_AES_128_CBC_SHA DH_RSA TLS_DH_RSA_WITH_AES_128_CBC_SHA DH_RSA
TLS_DHE_DSS_WITH_AES_128_CBC_SHA DHE_DSS TLS_DHE_DSS_WITH_AES_128_CBC_SHA DHE_DSS
TLS_DHE_RSA_WITH_AES_128_CBC_SHA DHE_RSA TLS_DHE_RSA_WITH_AES_128_CBC_SHA DHE_RSA
TLS_DH_anon_WITH_AES_128_CBC_SHA DH_anon TLS_DH_anon_WITH_AES_128_CBC_SHA DH_anon
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CipherSuite TLS_DHE_RSA_WITH_AES_128_CBC_SHA = { 0x00, 0x33 }; CipherSuite TLS_DHE_RSA_WITH_AES_128_CBC_SHA = { 0x00, 0x33 };
CipherSuite TLS_DH_anon_WITH_AES_128_CBC_SHA = { 0x00, 0x34 }; CipherSuite TLS_DH_anon_WITH_AES_128_CBC_SHA = { 0x00, 0x34 };
CipherSuite TLS_RSA_WITH_AES_256_CBC_SHA = { 0x00, 0x35 }; CipherSuite TLS_RSA_WITH_AES_256_CBC_SHA = { 0x00, 0x35 };
CipherSuite TLS_DH_DSS_WITH_AES_256_CBC_SHA = { 0x00, 0x36 }; CipherSuite TLS_DH_DSS_WITH_AES_256_CBC_SHA = { 0x00, 0x36 };
CipherSuite TLS_DH_RSA_WITH_AES_256_CBC_SHA = { 0x00, 0x37 }; CipherSuite TLS_DH_RSA_WITH_AES_256_CBC_SHA = { 0x00, 0x37 };
CipherSuite TLS_DHE_DSS_WITH_AES_256_CBC_SHA = { 0x00, 0x38 }; CipherSuite TLS_DHE_DSS_WITH_AES_256_CBC_SHA = { 0x00, 0x38 };
CipherSuite TLS_DHE_RSA_WITH_AES_256_CBC_SHA = { 0x00, 0x39 }; CipherSuite TLS_DHE_RSA_WITH_AES_256_CBC_SHA = { 0x00, 0x39 };
CipherSuite TLS_DH_anon_WITH_AES_256_CBC_SHA = { 0x00, 0x3A }; CipherSuite TLS_DH_anon_WITH_AES_256_CBC_SHA = { 0x00, 0x3A };
Padding
In section 4.7 of [TLS], the padding algorithm for RSA encryption
is defined to be PKCS #1 block type 2 [PKCS1-1.5]. When the AES
ietf-tls-ciphersuite-04 AES Ciphersuites for TLS 5 July 2001
ciphersuites are used, however, RSA encryption operations are
padded using OAEP [PKCS1-2.0].
The specific padding algorithm is described in [PKCS1-2.0] section
9.1.1 and is denoted EME-OAEP. A hash function and a mask genera¡
tion function must be selected in order for EME-OAEP to be com¡
pletely defined. For the purposes of the AES ciphersuites, the
hash function is SHA-1 and the mask generation function is MGF1,
described in [PKCS1-2.0] section 10.2.1.
Security Considerations Security Considerations
It is not believed that the new ciphersuites are ever less secure It is not believed that the new ciphersuites are ever less secure
than the corresponding older ones. The AES is believed to be than the corresponding older ones. The AES is believed to be
ietf-tls-ciphersuite-05 AES Ciphersuites for TLS 14 August 2001
secure, and it has withstood extensive cryptanalytic attack. secure, and it has withstood extensive cryptanalytic attack.
The ephemeral Diffie-Hellman ciphersuites provide forward secrecy The ephemeral Diffie-Hellman ciphersuites provide forward secrecy
without any known reduction in security in other areas. To obtain without any known reduction in security in other areas. To obtain
the maximum benefit from these ciphersuites: the maximum benefit from these ciphersuites:
1. The ephemeral keys should only be used once. With the TLS pro¡ 1. The ephemeral keys should only be used once. With the TLS pro¡
tocol as currently defined there is no significant efficiency tocol as currently defined there is no significant efficiency
gain from reusing ephemeral keys. gain from reusing ephemeral keys.
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than TLS. than TLS.
2. ADH is vulnerable to man-in-the-middle attacks, as a conse¡ 2. ADH is vulnerable to man-in-the-middle attacks, as a conse¡
quence of the lack of authentication. The parties must have a quence of the lack of authentication. The parties must have a
way of determining whether they are participating in the same way of determining whether they are participating in the same
TLS connection. If they are not, they can deduce that they are TLS connection. If they are not, they can deduce that they are
under attack, and presumably abort the connection. under attack, and presumably abort the connection.
For example, if the parties share a secret, it is possible to For example, if the parties share a secret, it is possible to
compute a MAC of the TLS Finished message. An attacker would compute a MAC of the TLS Finished message. An attacker would
ietf-tls-ciphersuite-04 AES Ciphersuites for TLS 5 July 2001
have to negotiate two different TLS connections; one with each have to negotiate two different TLS connections; one with each
communicating party. The Finished messages would be different communicating party. The Finished messages would be different
in each case, because they depend on the parties' public keys in each case, because they depend on the parties' public keys
(among other things). For this reason, the MACs computed by (among other things). For this reason, the MACs computed by
each party would be different. each party would be different.
It is important to note that authentication techniques which do It is important to note that authentication techniques which do
not use the Finished message do not usually provide protection not use the Finished message do not usually provide protection
from this attack. For example, the client could authenticate from this attack. For example, the client could authenticate
to the server with a password, but it would still be vulnerable to the server with a password, but it would still be vulnerable
to man-in-the-middle attacks. to man-in-the-middle attacks.
Copyright Copyright
ietf-tls-ciphersuite-05 AES Ciphersuites for TLS 14 August 2001
Copyright (C) The Internet Society 2001. All Rights Reserved. Copyright (C) The Internet Society 2001. All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain others, and derivative works that comment on or otherwise explain
it or assist in its implementation may be prepared, copied, pub¡ it or assist in its implementation may be prepared, copied, pub¡
lished and distributed, in whole or in part, without restriction of lished and distributed, in whole or in part, without restriction of
any kind, provided that the above copyright notice and this para¡ any kind, provided that the above copyright notice and this para¡
graph are included on all such copies and derivative works. How¡ graph are included on all such copies and derivative works. How¡
ever, this document itself may not be modified in any way, such as ever, this document itself may not be modified in any way, such as
by removing the copyright notice or references to the Internet by removing the copyright notice or references to the Internet
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RANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. RANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property Intellectual Property
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to per¡ intellectual property or other rights that might be claimed to per¡
tain to the implementation or use other technology described in tain to the implementation or use other technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the has made any effort to identify any such rights. Information on the
ietf-tls-ciphersuite-04 AES Ciphersuites for TLS 5 July 2001
IETF's procedures with respect to rights in standards-track and IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances claims of rights made available for publication and any assurances
of licenses to be made available, or the result of an attempt made of licenses to be made available, or the result of an attempt made
to obtain a general license or permission for the use of such pro¡ to obtain a general license or permission for the use of such pro¡
prietary rights by implementors or users of this specification can prietary rights by implementors or users of this specification can
be obtained from the IETF Secretariat. be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive this standard. Please address the information to the IETF Executive
Director. Director.
ietf-tls-ciphersuite-05 AES Ciphersuites for TLS 14 August 2001
During the development of the AES, NIST published the following During the development of the AES, NIST published the following
statement on intellectual property: statement on intellectual property:
SPECIAL NOTE - Intellectual Property SPECIAL NOTE - Intellectual Property
NIST reminds all interested parties that the adoption of NIST reminds all interested parties that the adoption of
AES is being conducted as an open standards-setting AES is being conducted as an open standards-setting
activity. Specifically, NIST has requested that all activity. Specifically, NIST has requested that all
interested parties identify to NIST any patents or inven¡ interested parties identify to NIST any patents or inven¡
tions that may be required for the use of AES. NIST tions that may be required for the use of AES. NIST
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I have submitted, known as Rijndael may be covered by the I have submitted, known as Rijndael may be covered by the
following U.S. and/or foreign patents: following U.S. and/or foreign patents:
none none
I do hereby declare that I am aware of no patent applica¡ I do hereby declare that I am aware of no patent applica¡
tions which may cover the practice of my submitted algo¡ tions which may cover the practice of my submitted algo¡
rithm, reference implementation or mathematically opti¡ rithm, reference implementation or mathematically opti¡
mized implementations. mized implementations.
ietf-tls-ciphersuite-04 AES Ciphersuites for TLS 5 July 2001
I do hereby understand that my submitted algorithm may I do hereby understand that my submitted algorithm may
not be selected for inclusion in the Advanced Encryption not be selected for inclusion in the Advanced Encryption
Standard. I also understand and agree that after the Standard. I also understand and agree that after the
close of the submission period, my submission may not be close of the submission period, my submission may not be
withdrawn from public consideration for inclusion in the withdrawn from public consideration for inclusion in the
Federal Information Processing Standard (FIPS) for Federal Information Processing Standard (FIPS) for
Advanced Encryption Standard (AES). I further understand Advanced Encryption Standard (AES). I further understand
that I will not receive financial compensation from the that I will not receive financial compensation from the
government for my submission. I certify that, to the government for my submission. I certify that, to the
best of my knowledge, I have fully disclosed all patents best of my knowledge, I have fully disclosed all patents
and patent applications relating to my algorithm. I also and patent applications relating to my algorithm. I also
understand that the U.S. Government may, during the understand that the U.S. Government may, during the
course of the lifetime of the AES or during the FIPS pub¡ course of the lifetime of the AES or during the FIPS pub¡
lic review process, modify the algorithm's specifications lic review process, modify the algorithm's specifications
(e.g., to protect against a newly discovered vulnerabil¡ (e.g., to protect against a newly discovered
ity). Should my submission be selected for inclusion in
the AES, I hereby agree not to place any restrictions on ietf-tls-ciphersuite-05 AES Ciphersuites for TLS 14 August 2001
the use of the algorithm intending it to be available on
a worldwide, non-exclusive, royalty-free basis. vulnerability). Should my submission be selected for
inclusion in the AES, I hereby agree not to place any
restrictions on the use of the algorithm intending it to
be available on a worldwide, non-exclusive, royalty-free
basis.
I do hereby agree to provide the statements for any I do hereby agree to provide the statements for any
patent or patent application identified to cover practice patent or patent application identified to cover practice
of my algorithm, reference implementation or mathemati¡ of my algorithm, reference implementation or mathemati¡
cally optimized implementations and the right to use such cally optimized implementations and the right to use such
implementations for the purposes of the AES evaluation implementations for the purposes of the AES evaluation
process. process.
I understand that NIST will announce the selected algo¡ I understand that NIST will announce the selected algo¡
rithm(s) and proceed to publish the draft FIPS for public rithm(s) and proceed to publish the draft FIPS for public
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period of four years from the close of the submission period of four years from the close of the submission
date for candidate algorithms, all rights revert to the date for candidate algorithms, all rights revert to the
submitter (and other owner[s] as appropriate). submitter (and other owner[s] as appropriate).
[signed] [signed]
Title: Cryptographer Title: Cryptographer
Dated: 10-6-98 Dated: 10-6-98
Place: Brussels Place: Brussels
ietf-tls-ciphersuite-04 AES Ciphersuites for TLS 5 July 2001
The following disclaimer was signed at the start of the second The following disclaimer was signed at the start of the second
"round" of the AES process: "round" of the AES process:
Dear Mr Foti [of NIST], Dear Mr Foti [of NIST],
Hereby we confirm that the original patent and patent Hereby we confirm that the original patent and patent
application information, as provided to NIST with our application information, as provided to NIST with our
original submission in June 1998, has not changed. To original submission in June 1998, has not changed. To
the best of our knowledge, there are no patents or patent the best of our knowledge, there are no patents or patent
applications covering the practice of the algorithm, ref¡ applications covering the practice of the algorithm, ref¡
erence implementation or the mathematically optimized erence implementation or the mathematically optimized
implementations. implementations.
ietf-tls-ciphersuite-05 AES Ciphersuites for TLS 14 August 2001
[signed] [signed]
Joan Daemen, Vincent Rijmen Joan Daemen, Vincent Rijmen
Acknowledgements Acknowledgements
I would like to thank the ietf-tls mailing list contributors who I would like to thank the ietf-tls mailing list contributors who
have made helpful suggestions for this document. have made helpful suggestions for this document.
References References
[TLS] T. Dierks, C. Allen, "The TLS Protocol Version 1.0" RFC-2246.
January, 1999.
[AES] J. Daemen, V. Rijmen, "The Rijndael Block Cipher" [AES] J. Daemen, V. Rijmen, "The Rijndael Block Cipher"
http://csrc.nist.gov/encryption/aes/rijndael/Rijndael.pdf 3rd http://csrc.nist.gov/encryption/aes/rijndael/Rijndael.pdf 3rd
September 1999. September 1999.
[PKCS1-1.5] RSA Laboratories, "PKCS #1: RSA Encryption Standard"
version 1.5, November 1993.
[PKCS1-2.0] B. Kaliski, J. Staddon, "PKCS #1: RSA Cryptography
Specifications Version 2.0" RFC 2437.
[SHA-1] FIPS PUB 180-1, "Secure Hash Standard," National Institute [SHA-1] FIPS PUB 180-1, "Secure Hash Standard," National Institute
of Standards and Technology, U.S. Department of Commerce, April 17, of Standards and Technology, U.S. Department of Commerce, April 17,
1995. 1995.
[TLS] T. Dierks, C. Allen, "The TLS Protocol Version 1.0" RFC 2246.
January, 1999.
Author's Address Author's Address
Pete Chown Pete Chown
Skygate Technology Ltd Skygate Technology Ltd
8 Lombard Road 8 Lombard Road
London London
SW19 3TZ SW19 3TZ
ietf-tls-ciphersuite-04 AES Ciphersuites for TLS 5 July 2001
United Kingdom United Kingdom
Phone: +44 20 8542 7856 Phone: +44 20 8542 7856
Email: pc@skygate.co.uk Email: pc@skygate.co.uk
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