< draft-ietf-tls-ecdhe-psk-04.txt   draft-ietf-tls-ecdhe-psk-05.txt >
TLS Working Group Mohamad Badra TLS Working Group Mohamad Badra
Internet Draft LIMOS Laboratory Internet Draft LIMOS Laboratory
Intended status: Informational October 17, 2008 Intended status: Informational November 1, 2008
Expires: April 2009 Expires: May 2009
ECDHE_PSK Ciphersuites for Transport Layer Security (TLS) ECDHE_PSK Ciphersuites for Transport Layer Security (TLS)
draft-ietf-tls-ecdhe-psk-04.txt draft-ietf-tls-ecdhe-psk-05.txt
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Copyright (C) The IETF Trust (2008). Copyright (C) The IETF Trust (2008).
Abstract Abstract
This document extends RFC 4279, RFC 4492 and RFC 4785, and specifies This document extends RFC 4279, RFC 4492 and RFC 4785, and specifies
a set of ciphersuites that use a pre-shared key (PSK) to authenticate a set of cipher suites that use a pre-shared key (PSK) to
an Elliptic Curve Diffie-Hellman exchange (ECDH). These ciphersuites authenticate an Elliptic Curve Diffie-Hellman exchange (ECDH). These
provide Perfect Forward Secrecy (PFS). cipher suites provide Perfect Forward Secrecy (PFS).
Table of Contents Table of Contents
1. Introduction...................................................3 1. Introduction...................................................3
1.1. Applicability Statement...................................3 1.1. Applicability Statement...................................3
1.2. Conventions used in this document.........................3 1.2. Conventions used in this document.........................3
2. ECDHE_PSK Key Exchange Algorithm...............................3 2. ECDHE_PSK Key Exchange Algorithm...............................3
3. ECDHE_PSK Based Cipher Suites..................................5 3. ECDHE_PSK Based Cipher Suites..................................4
3.1. ECDHE_PSK Cipher Suites Using the SHA-1 Hash..............5 3.1. ECDHE_PSK Cipher Suites Using the SHA-1 Hash..............4
3.2. ECDHE_PSK Cipher Suites Using SHA-2 Hashes................5 3.2. ECDHE_PSK Cipher Suites Using SHA-2 Hashes................5
4. ECDHE_PSK Based Cipher Suites with NULL Encryption.............5 4. ECDHE_PSK Based Cipher Suites with NULL Encryption.............5
4.1. ECDHE_PSK Cipher Suites Using the SHA-1 Hash with NULL 4.1. ECDHE_PSK Cipher Suite Using the SHA-1 Hash with NULL
Encryption.....................................................5 Encryption.....................................................5
4.2. ECDHE_PSK Cipher Suites Using SHA-2 Hashes with NULL 4.2. ECDHE_PSK Cipher Suites Using SHA-2 Hashes with NULL
Encryption.....................................................6 Encryption.....................................................6
5. Security Considerations........................................6 5. Security Considerations........................................6
6. IANA Considerations............................................6 6. IANA Considerations............................................6
7. Acknowledgments................................................6 7. Acknowledgments................................................7
8. References.....................................................7 8. References.....................................................7
8.1. Normative References......................................7 8.1. Normative References......................................7
Author's Addresses................................................7 Author's Addresses................................................7
Intellectual Property Statement...................................7 Intellectual Property Statement...................................7
Disclaimer of Validity............................................8 Disclaimer of Validity............................................8
1. Introduction 1. Introduction
RFC 4279 specifies cipher suites for supporting TLS using pre-shared RFC 4279 specifies cipher suites for supporting TLS using pre-shared
symmetric keys which (a) use only symmetric key operations for symmetric keys which (a) use only symmetric key operations for
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RFC 4492 defines a set of ECC-based cipher suites for TLS and RFC 4492 defines a set of ECC-based cipher suites for TLS and
describes the use of ECC certificates for client authentication. In describes the use of ECC certificates for client authentication. In
particular, it specifies the use of Elliptic Curve Diffie-Hellman particular, it specifies the use of Elliptic Curve Diffie-Hellman
(ECDH) key agreement in a TLS handshake and the use of Elliptic Curve (ECDH) key agreement in a TLS handshake and the use of Elliptic Curve
Digital Signature Algorithm (ECDSA) as a new authentication Digital Signature Algorithm (ECDSA) as a new authentication
mechanism. mechanism.
This document specifies a set of cipher suites that use a PSK to This document specifies a set of cipher suites that use a PSK to
authenticate an ECDH exchange. These cipher suites provide Perfect authenticate an ECDH exchange. These cipher suites provide Perfect
Forward Secrecy. One of these ciphersuites provides authentication- Forward Secrecy. One of these cipher suites provides authentication-
only. only.
The reader is expected to become familiar with RFC 4279, RFC 4492, The reader is expected to become familiar with RFC 4279, RFC 4492,
and RFC 4785 prior to studying this document. and RFC 4785 prior to studying this document.
1.1. Applicability Statement 1.1. Applicability Statement
The ciphersuites defined in Sections 3.1 and 4.1 can be negotiated, The cipher suites defined in this document can be negotiated,
whatever the negotiated TLS version is. whatever the negotiated TLS version is.
The ciphersuites defined in Sections 3.2 and 4.2 can be negotiated in
TLS version 1.2 or higher.
1.2. Conventions used in this document 1.2. 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].
2. ECDHE_PSK Key Exchange Algorithm 2. ECDHE_PSK Key Exchange Algorithm
The ciphersuites described in this document make use of the EC The cipher suites described in this document make use of the EC
parameter negotiation mechanism defined in RFC 4492. When the parameter negotiation mechanism defined in RFC 4492. When the cipher
ciphersuites defined in this document are used, the suites defined in this document are used, the 'ec_diffie_hellman_psk'
'ec_diffie_hellman_psk' case inside the ServerKeyExchange and case inside the ServerKeyExchange and ClientKeyExchange structure
ClientKeyExchange structure MUST be used instead of the 'psk' case MUST be used instead of the 'psk' case defined in [RFC4279] (i.e.,
defined in [RFC4279] (i.e., the ServerKeyExchange and the ServerKeyExchange and ClientKeyExchange messages include the
ClientKeyExchange messages include the Diffie-Hellman parameters). Diffie-Hellman parameters). The PSK identity and identity hint
The PSK identity and identity hint fields have the same meaning and fields have the same meaning and encoding as specified in [RFC4279]
encoding as specified in [RFC4279] (note that the ServerKeyExchange (note that the ServerKeyExchange message is always sent, even if no
message is always sent, even if no PSK identity hint is provided). PSK identity hint is provided).
The format of the ServerKeyExchange and ClientKeyExchange messages is The format of the ServerKeyExchange and ClientKeyExchange messages is
shown below. shown below.
struct { struct {
select (KeyExchangeAlgorithm) { select (KeyExchangeAlgorithm) {
/* other cases for rsa, diffie_hellman, etc. */ /* other cases for rsa, diffie_hellman, etc. */
case ec_diffie_hellman_psk: /* NEW */ case ec_diffie_hellman_psk: /* NEW */
opaque psk_identity_hint<0..2^16-1>; opaque psk_identity_hint<0..2^16-1>;
ServerECDHParams params; ServerECDHParams params;
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3.1. ECDHE_PSK Cipher Suites Using the SHA-1 Hash 3.1. ECDHE_PSK Cipher Suites Using the SHA-1 Hash
CipherSuite TLS_ECDHE_PSK_WITH_RC4_128_SHA = {0xXX,0xXX}; CipherSuite TLS_ECDHE_PSK_WITH_RC4_128_SHA = {0xXX,0xXX};
CipherSuite TLS_ECDHE_PSK_WITH_3DES_EDE_CBC_SHA = {0xXX,0xXX}; CipherSuite TLS_ECDHE_PSK_WITH_3DES_EDE_CBC_SHA = {0xXX,0xXX};
CipherSuite TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA = {0xXX,0xXX}; CipherSuite TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA = {0xXX,0xXX};
CipherSuite TLS_ECDHE_PSK_WITH_AES_256_CBC_SHA = {0xXX,0xXX}; CipherSuite TLS_ECDHE_PSK_WITH_AES_256_CBC_SHA = {0xXX,0xXX};
The above four cipher suites match the cipher suites defined in The above four cipher suites match the cipher suites defined in
[RFC4279], except that they use an Elliptic Curve Diffie-Hellman [RFC4279], except that they use an Elliptic Curve Diffie-Hellman
exchange [RFC4492] authenticated with a PSK and that: exchange [RFC4492] authenticated with a PSK, and that:
o when negotiated in a version of TLS prior to 1.2, they use the - The MAC is HMAC [RFC2104] with SHA-1 as the hash
Pseudo Random Function (PRF) from that version; function.
o when negotiated in TLS version 1.2, they use the PRF with the - When negotiated in a version of TLS prior to 1.2, the PRF
SHA-256 hash function defined in TLS version 1.2. from that version is used; otherwise the PRF is the TLS
PRF [RFC5246] with SHA-256 as the hash function.
3.2. ECDHE_PSK Cipher Suites Using SHA-2 Hashes 3.2. ECDHE_PSK Cipher Suites Using SHA-2 Hashes
CipherSuite TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA256 = {0xXX,0xXX}; CipherSuite TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA256 = {0xXX,0xXX};
CipherSuite TLS_ECDHE_PSK_WITH_AES_256_CBC_SHA384 = {0xXX,0xXX}; CipherSuite TLS_ECDHE_PSK_WITH_AES_256_CBC_SHA384 = {0xXX,0xXX};
The above two cipher suites are the same as the corresponding AES The above two cipher suites are the same as the corresponding AES
cipher suites in section 3.1 above, except for the hash and PRF cipher suites in section 3.1 above, except for the hash and PRF
algorithms, which SHALL be as follows: algorithms, which SHALL be as follows:
For TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA256, the PRF is the TLS PRF O For the cipher suites TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA256:
[RFC5246] with SHA-256 as the hash function, and the MAC is HMAC
[RFC2104] with SHA-256 as the hash function.
For TLS_ECDHE_PSK_WITH_AES_256_CBC_SHA384, the PRF is the TLS PRF - The MAC is HMAC [RFC2104] with SHA-256 as the hash
[RFC5246] with SHA-384 as the hash function, and the MAC is HMAC function.
[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-256 as the hash function.
o For the cipher suite TLS_ECDHE_PSK_WITH_AES_256_CBC_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.
4. ECDHE_PSK Based Cipher Suites with NULL Encryption 4. ECDHE_PSK Based Cipher Suites with NULL Encryption
4.1. ECDHE_PSK Cipher Suites Using the SHA-1 Hash with NULL Encryption 4.1. ECDHE_PSK Cipher Suite Using the SHA-1 Hash with NULL Encryption
The following cipher suite matches the cipher suites defined in The following cipher suite matches the cipher suites defined in
section 3.1, except that we define a suite with null encryption. section 3.1, except that we define a suite with NULL encryption.
CipherSuite TLS_ECDHE_PSK_WITH_NULL_SHA = {0xXX,0xXX}; CipherSuite TLS_ECDHE_PSK_WITH_NULL_SHA = {0xXX,0xXX};
4.2. ECDHE_PSK Cipher Suites Using SHA-2 Hashes with NULL Encryption 4.2. ECDHE_PSK Cipher Suites Using SHA-2 Hashes with NULL Encryption
The following two cipher suites are the same as the corresponding
cipher suites in section 3.2, but with NULL encryption (instead of
AES).
CipherSuite TLS_ECDHE_PSK_WITH_NULL_SHA256 = {0xXX,0xXX}; CipherSuite TLS_ECDHE_PSK_WITH_NULL_SHA256 = {0xXX,0xXX};
CipherSuite TLS_ECDHE_PSK_WITH_NULL_SHA384 = {0xXX,0xXX}; CipherSuite TLS_ECDHE_PSK_WITH_NULL_SHA384 = {0xXX,0xXX};
These two cipher suites are the same as the corresponding cipher
suites in section 3.2, but with NULL encryption (instead of AES).
5. Security Considerations 5. Security Considerations
The security considerations described throughout [RFC5246], The security considerations described throughout [RFC5246],
[RFC4785], [RFC4492], and [RFC4279] apply here as well. In [RFC4785], [RFC4492], and [RFC4279] apply here as well. In
particular, as authentication-only cipher suites (with no encryption) particular, as authentication-only cipher suites (with no encryption)
defined here do not support confidentiality, care should be taken not defined here do not support confidentiality, care should be taken not
to send sensitive information (such as passwords) over connections to send sensitive information (such as passwords) over connections
protected with one of the cipher suites with NULL encryption defined protected with one of the cipher suites with NULL encryption defined
in this document. in this document.
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The author appreciates Alfred Hoenes for his detailed review and The author appreciates Alfred Hoenes for his detailed review and
effort on issues resolving discussion. The author would like to effort on issues resolving discussion. The author would like to
acknowledge Bodo Moeller, Simon Josefsson, Uri Blumenthal, Pasi acknowledge Bodo Moeller, Simon Josefsson, Uri Blumenthal, Pasi
Eronen, Paul Hoffman, Joseph Salowey, Mark Tillinghast, and the TLS Eronen, Paul Hoffman, Joseph Salowey, Mark Tillinghast, and the TLS
mailing list members for their comments on the document. mailing list members for their comments on the document.
8. References 8. References
8.1. Normative References 8.1. Normative References
[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 [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.
[RFC4279] Eronen, P. and H. Tschofenig, "Pre-Shared Key Ciphersuites [RFC4279] Eronen, P. and H. Tschofenig, "Pre-Shared Key Ciphersuites
for Transport Layer Security (TLS)", RFC 4279, December for Transport Layer Security (TLS)", RFC 4279, December
2005. 2005.
[RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C. and B. [RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C. and B.
Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites
for Transport Layer Security (TLS)", RFC 4492, May 2006. for Transport Layer Security (TLS)", RFC 4492, May 2006.
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