Internet DRAFT - draft-mattsson-tls-ecdhe-psk-aead
draft-mattsson-tls-ecdhe-psk-aead
Network Working Group J. Mattsson
Internet-Draft D. Migault
Intended status: Standards Track Ericsson
Expires: October 20, 2016 April 18, 2016
ECDHE_PSK with AES-GCM and AES-CCM Cipher Suites
for Transport Layer Security (TLS)
draft-mattsson-tls-ecdhe-psk-aead-05
Abstract
This document defines several new cipher suites for the Transport
Layer Security (TLS) protocol. The cipher suites are all based on
the Ephemeral Elliptic Curve Diffie-Hellman with Pre-Shared Key
(ECDHE_PSK) key exchange together with the Authenticated Encryption
with Associated Data (AEAD) algorithms AES-GCM and AES-CCM. PSK
provides light and efficient authentication, ECDHE provides perfect
forward secrecy, and AES-GCM and AES-CCM provides encryption and
integrity protection.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. ECDHE_PSK with AES-GCM and AES-CCM Cipher Suites . . . . . . 3
3. Applicable TLS Versions . . . . . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
This document defines new cipher suites that provide Pre-Shared Key
(PSK) authentication, Perfect Forward Secrecy (PFS), and
Authenticated Encryption with Associated Data (AEAD). The cipher
suites are defined for version 1.2 or later of the the Transport
Layer Security (TLS) [RFC5246] protocol, as well as version 1.2 or
later of the Datagram Transport Layer Security (DTLS) protocol
[RFC6347].
Pre-Shared Key (PSK) Authentication is widely used in many scenarios.
One deployment is 3GPP networks where pre-shared keys are used to
authenticate both subscriber and network. Another deployment is
Internet of Things where PSK authentication is often preferred for
performance and energy efficiency reasons. In both scenarios the
endpoints are owned/controlled by a party that provisions the pre-
shared keys and makes sure that they provide a high level of entropy.
Perfect Forward Secrecy (PFS) is a strongly recommended feature in
security protocol design and can be accomplished by using an
ephemeral Diffie-Hellman key exchange method. Ephemeral Elliptic
Curve Diffie-Hellman (ECDHE) provides PFS with excellent performance
and small key sizes. ECDHE is mandatory to implement in both HTTP/2
[RFC7540] and CoAP [RFC7252].
AEAD algorithms that combine encryption and integrity protection are
strongly recommended [RFC7525] and non-AEAD algorithms are forbidden
to use in TLS 1.3 [I-D.ietf-tls-tls13]. The AEAD algorithms
considered in this document are AES-GCM and AES-CCM. The use of AES-
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GCM in TLS is defined in [RFC5288] and the use of AES-CCM is defined
in [RFC6655].
[RFC4279] defines Pre-Shared Key (PSK) cipher suites for TLS but does
not consider Elliptic Curve Cryptography. [RFC4492] introduces
Elliptic Curve Cryptography for TLS but does not consider PSK
authentication. [RFC5487] describes the use of AES-GCM in
combination with PSK authentication, but does not consider ECDHE.
[RFC5489] describes the use of PSK in combination with ECDHE but does
not consider AES-GCM or AES-CCM.
2. ECDHE_PSK with AES-GCM and AES-CCM Cipher Suites
The cipher suites defined in this document are based on the AES-GCM
and AES-CCM Authenticated Encryption with Associated Data (AEAD)
algorithms AEAD_AES_128_GCM, AEAD_AES_256_GCM, AEAD_AES_128_CCM, and
AEAD_AES_256_CCM defined in [RFC5116], AEAD_AES_128_CCM_8 and
AEAD_AES_256_CCM_8 defined in [RFC6655]. The following cipher suites
are defined:
TLS_ECDHE_PSK_WITH_AES_128_GCM_SHA256 = {0xTBD,0xTBD};
TLS_ECDHE_PSK_WITH_AES_256_GCM_SHA384 = {0xTBD,0xTBD};
TLS_ECDHE_PSK_WITH_AES_128_CCM_8_SHA256 = {0xTBD,0xTBD};
TLS_ECDHE_PSK_WITH_AES_256_CCM_8_SHA256 = {0xTBD,0xTBD};
TLS_ECDHE_PSK_WITH_AES_128_CCM_SHA256 = {0xTBD,0xTBD};
TLS_ECDHE_PSK_WITH_AES_256_CCM_SHA384 = {0xTBD,0xTBD};
For the AES-128 cipher suites, the TLS Pseudorandom Function (PRF)
with SHA-256 as the hash function SHALL be used and Clients and
Servers MUST NOT negotiate curves of less than 255 bits.
For the AES-256 cipher suites, the TLS PRF with SHA-384 as the hash
function SHALL be used and Clients and Servers MUST NOT negotiate
curves of less than 384 bits.
When used in TLS 1.2, the keying material is derived as described in
[RFC5489] and [RFC5246] and nonces are constructed as described in
[RFC5288], and [RFC6655]. When used in TLS 1.3, the keying material
is derived as described in [I-D.ietf-tls-tls13], and the nonces are
constructed as described in [I-D.ietf-tls-tls13].
3. Applicable TLS Versions
The cipher suites defined in this document make use of the
authenticated encryption with additional data (AEAD) defined in TLS
1.2 [RFC5246] and DTLS 1.2 [RFC6347]. Earlier versions of TLS do not
have support for AEAD and consequently, these cipher suites MUST NOT
be negotiated in TLS versions prior to 1.2. Clients MUST NOT offer
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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. A client MUST treat the selection of these cipher
suites in combination with a version of TLS that does not support
AEAD (i.e., TLS 1.1 or earlier) as an error and generate a fatal
'illegal_parameter' TLS alert.
4. IANA Considerations
This document defines the following new cipher suites, whose values
have been assigned in the TLS Cipher Suite Registry defined by
[RFC5246].
TLS_ECDHE_PSK_WITH_AES_128_GCM_SHA256 = {0xTBD; 0xTBD} {0xD0,0x01};
TLS_ECDHE_PSK_WITH_AES_256_GCM_SHA384 = {0xTBD; 0xTBD} {0xD0,0x02};
TLS_ECDHE_PSK_WITH_AES_128_CCM_8_SHA256 = {0xTBD; 0xTBD} {0xD0,0x03};
TLS_ECDHE_PSK_WITH_AES_256_CCM_8_SHA256 = {0xTBD; 0xTBD} {0xD0,0x04};
TLS_ECDHE_PSK_WITH_AES_128_CCM_SHA256 = {0xTBD; 0xTBD} {0xD0,0x05};
TLS_ECDHE_PSK_WITH_AES_256_CCM_SHA384 = {0xTBD; 0xTBD} {0xD0,0x06};
The cipher suite numbers listed in the second column are numbers used
for cipher suite interoperability testing and it's suggested that
IANA use these values for assignment.
5. Security Considerations
The security considerations in TLS 1.2 [RFC5246], DTLS 1.2 [RFC6347],
TLS 1.3 [I-D.ietf-tls-tls13], ECDHE_PSK [RFC5489], AES-GCM [RFC5288],
and AES-CCM [RFC6655] apply to this document as well.
All the cipher suites defined in this document provide
confidentiality, mutual authentication, and perfect forward secrecy.
The AES-128 cipher suites provide 128-bit security and the AES-256
cipher suites provide at least 192-bit security. However,
AES_128_CCM_8 only provides 64-bit security against message forgery
and AES_256_GCM and AES_256_CCM only provide 128-bit security against
message forgery.
Use of Pre-Shared Keys of limited entropy (for example, a PSK that is
relatively short, or was chosen by a human and thus may contain less
entropy than its length would imply) may allow an active attacker to
perform a brute-force attack where the attacker attempts to connect
to the server and tries different keys. Passive eavesdropping alone
is not sufficient. For these reasons the Pre-Shared Keys used for
authentication MUST have a security level equal or higher than the
cipher suite used, i.e. at least 128-bit for the AES-128 cipher
suites and at least 192-bit for the AES-256 cipher suites.
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6. Acknowledgements
The authors would like to thank Ilari Liusvaara, Eric Rescorla, Dan
Harkins, Russ Housley and Sean Turner for their valuable comments and
feedback.
7. References
7.1. Normative References
[I-D.ietf-tls-tls13]
Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", draft-ietf-tls-tls13-12 (work in progress),
March 2016.
[RFC4279] Eronen, P., Ed. and H. Tschofenig, Ed., "Pre-Shared Key
Ciphersuites for Transport Layer Security (TLS)",
RFC 4279, DOI 10.17487/RFC4279, December 2005,
<http://www.rfc-editor.org/info/rfc4279>.
[RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B.
Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites
for Transport Layer Security (TLS)", RFC 4492,
DOI 10.17487/RFC4492, May 2006,
<http://www.rfc-editor.org/info/rfc4492>.
[RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated
Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008,
<http://www.rfc-editor.org/info/rfc5116>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>.
[RFC5288] Salowey, J., Choudhury, A., and D. McGrew, "AES Galois
Counter Mode (GCM) Cipher Suites for TLS", RFC 5288,
DOI 10.17487/RFC5288, August 2008,
<http://www.rfc-editor.org/info/rfc5288>.
[RFC5489] Badra, M. and I. Hajjeh, "ECDHE_PSK Cipher Suites for
Transport Layer Security (TLS)", RFC 5489,
DOI 10.17487/RFC5489, March 2009,
<http://www.rfc-editor.org/info/rfc5489>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <http://www.rfc-editor.org/info/rfc6347>.
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[RFC6655] McGrew, D. and D. Bailey, "AES-CCM Cipher Suites for
Transport Layer Security (TLS)", RFC 6655,
DOI 10.17487/RFC6655, July 2012,
<http://www.rfc-editor.org/info/rfc6655>.
7.2. Informative References
[RFC5487] Badra, M., "Pre-Shared Key Cipher Suites for TLS with SHA-
256/384 and AES Galois Counter Mode", RFC 5487,
DOI 10.17487/RFC5487, March 2009,
<http://www.rfc-editor.org/info/rfc5487>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014,
<http://www.rfc-editor.org/info/rfc7252>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <http://www.rfc-editor.org/info/rfc7525>.
[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015,
<http://www.rfc-editor.org/info/rfc7540>.
Authors' Addresses
John Mattsson
Ericsson AB
SE-164 80 Stockholm
Sweden
Phone: +46 76 115 35 01
Email: john.mattsson@ericsson.com
Daniel Migault
Ericsson
8400 boulevard Decarie
Montreal, QC H4P 2N2
Canada
Phone: +1 514-452-2160
Email: daniel.migault@ericsson.com
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