Internet Engineering Task Force (IETF)                       J. Mattsson
Request for Comments: 8442                                    D. Migault
Category: Standards Track                                       Ericsson
ISSN: 2070-1721                                           September 2018


           ECDHE_PSK with AES-GCM and AES-CCM Cipher Suites
                       for TLS 1.2 and DTLS 1.2

Abstract

  This document defines several new cipher suites for version 1.2 of
  the Transport Layer Security (TLS) protocol and version 1.2 of the
  Datagram Transport Layer Security (DTLS) protocol.  These cipher
  suites are 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 forward secrecy, and AES-GCM and
  AES-CCM provide encryption and integrity protection.

Status of This Memo

  This is an Internet Standards Track document.

  This document is a product of the Internet Engineering Task Force
  (IETF).  It represents the consensus of the IETF community.  It has
  received public review and has been approved for publication by the
  Internet Engineering Steering Group (IESG).  Further information on
  Internet Standards is available in Section 2 of RFC 7841.

  Information about the current status of this document, any errata,
  and how to provide feedback on it may be obtained at
  https://www.rfc-editor.org/info/rfc8442.

















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Copyright Notice

  Copyright (c) 2018 IETF Trust and the persons identified as the
  document authors.  All rights reserved.

  This document is subject to BCP 78 and the IETF Trust's Legal
  Provisions Relating to IETF Documents
  (https://trustee.ietf.org/license-info) in effect on the date of
  publication of this document.  Please review these documents
  carefully, as they describe your rights and restrictions with respect
  to this document.  Code Components extracted from this document must
  include Simplified BSD License text as described in Section 4.e of
  the Trust Legal Provisions and are provided without warranty as
  described in the Simplified BSD License.

Table of Contents

  1. Introduction ....................................................2
  2. Requirements Notation ...........................................3
  3. ECDHE_PSK with AES-GCM and AES-CCM Cipher Suites ................3
  4. IANA Considerations .............................................4
  5. Security Considerations .........................................4
  6. References ......................................................5
     6.1. Normative References .......................................5
     6.2. Informative References .....................................6
  Acknowledgements ...................................................7
  Authors' Addresses .................................................7

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 of the Transport Layer Security
  (TLS) protocol [RFC5246] and version 1.2 of the Datagram Transport
  Layer Security (DTLS) protocol [RFC6347].

  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 and/or 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



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  Curve Diffie-Hellman (ECDHE) provides PFS with excellent performance
  and small key sizes.  ECDHE is mandatory to implement in both HTTP/2
  [RFC7540] and the Constrained Application Protocol (CoAP) [RFC7252].

  AEAD algorithms that combine encryption and integrity protection are
  strongly recommended for (D)TLS [RFC7525], and TLS 1.3 [RFC8446]
  forbids the use of non-AEAD algorithms.  The AEAD algorithms
  considered in this document are AES-GCM and AES-CCM.  The use of
  AES-GCM in TLS is defined in [RFC5288], and the use of AES-CCM is
  defined in [RFC6655].

  [RFC4279] defines PSK cipher suites for TLS but does not consider
  elliptic curve cryptography.  [RFC8422] 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.  Requirements Notation

  The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
  "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
  "OPTIONAL" in this document are to be interpreted as described in
  BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
  capitals, as shown here.

3.  ECDHE_PSK with AES-GCM and AES-CCM Cipher Suites

  The cipher suites defined in this document are based on the following
  AES-GCM and AES-CCM AEAD algorithms: AEAD_AES_128_GCM [RFC5116],
  AEAD_AES_256_GCM [RFC5116], AEAD_AES_128_CCM [RFC5116], and
  AEAD_AES_128_CCM_8 [RFC6655].

  Messages and premaster secret construction in this document are
  defined in [RFC5489].  The ServerKeyExchange and ClientKeyExchange
  messages are used, and the premaster secret is computed as for the
  ECDHE_PSK key exchange.  The elliptic curve parameters used in the
  Diffie-Hellman parameters are negotiated using extensions defined in
  [RFC8422].

  For TLS 1.2 and DTLS 1.2, the following cipher suites are defined:

  TLS_ECDHE_PSK_WITH_AES_128_GCM_SHA256   = {0xD0,0x01}
  TLS_ECDHE_PSK_WITH_AES_256_GCM_SHA384   = {0xD0,0x02}
  TLS_ECDHE_PSK_WITH_AES_128_CCM_8_SHA256 = {0xD0,0x03}
  TLS_ECDHE_PSK_WITH_AES_128_CCM_SHA256   = {0xD0,0x05}




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  The assigned code points can only be used for TLS 1.2 and DTLS 1.2.

  The cipher suites defined in this document MUST NOT be negotiated for
  any version of (D)TLS other than version 1.2.  Servers MUST NOT
  select one of these cipher suites when selecting a (D)TLS version
  other than version 1.2.  A client MUST treat the selection of these
  cipher suites in combination with a different version of (D)TLS as an
  error and generate a fatal 'illegal_parameter' TLS alert.

  Cipher suites TLS_AES_128_GCM_SHA256, TLS_AES_256_GCM_SHA384,
  TLS_AES_128_CCM_8_SHA256, and TLS_AES_128_CCM_SHA256 are used to
  support equivalent functionality in TLS 1.3 [RFC8446].

4.  IANA Considerations

  This document defines the following new cipher suites for TLS 1.2 and
  DTLS 1.2.  The values have been assigned in the "TLS Cipher Suites"
  registry defined by [RFC8446] and [RFC8447].

 Value       Description                            DTLS-OK Recommended
 -----       -----------                            ------- -----------
 {0xD0,0x01} TLS_ECDHE_PSK_WITH_AES_128_GCM_SHA256    Y         Y
 {0xD0,0x02} TLS_ECDHE_PSK_WITH_AES_256_GCM_SHA384    Y         Y
 {0xD0,0x03} TLS_ECDHE_PSK_WITH_AES_128_CCM_8_SHA256  Y         N
 {0xD0,0x05} TLS_ECDHE_PSK_WITH_AES_128_CCM_SHA256    Y         Y

5.  Security Considerations

  The security considerations in TLS 1.2 [RFC5246], DTLS 1.2 [RFC6347],
  PSK Ciphersuites for TLS [RFC4279], 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 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.

  The pre-shared keys used for authentication MUST have a security
  level equal to or higher than the cipher suite used, i.e., at least
  128-bit security for the AES-128 cipher suites and at least 192-bit
  security for the AES-256 cipher suites.

  GCM or CCM encryption that reuses a nonce with a same key undermines
  the security of GCM and CCM.  As a result, GCM and CCM MUST only be
  used with a system guaranteeing nonce uniqueness [RFC5116].





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6.  References

6.1.  Normative References

  [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119,
             DOI 10.17487/RFC2119, March 1997,
             <https://www.rfc-editor.org/info/rfc2119>.

  [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,
             <https://www.rfc-editor.org/info/rfc4279>.

  [RFC5116]  McGrew, D., "An Interface and Algorithms for Authenticated
             Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008,
             <https://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,
             <https://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,
             <https://www.rfc-editor.org/info/rfc5288>.

  [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
             Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
             January 2012, <https://www.rfc-editor.org/info/rfc6347>.

  [RFC6655]  McGrew, D. and D. Bailey, "AES-CCM Cipher Suites for
             Transport Layer Security (TLS)", RFC 6655,
             DOI 10.17487/RFC6655, July 2012,
             <https://www.rfc-editor.org/info/rfc6655>.

  [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
             2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
             May 2017, <https://www.rfc-editor.org/info/rfc8174>.

  [RFC8422]  Nir, Y., Josefsson, S., and M. Pegourie-Gonnard, "Elliptic
             Curve Cryptography (ECC) Cipher Suites for Transport Layer
             Security (TLS) Versions 1.2 and Earlier", RFC 8422,
             DOI 10.17487/RFC8422, August 2018,
             <https://www.rfc-editor.org/info/rfc8422>.





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  [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
             Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
             <https://www.rfc-editor.org/info/rfc8446>.

6.2.  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,
             <https://www.rfc-editor.org/info/rfc5487>.

  [RFC5489]  Badra, M. and I. Hajjeh, "ECDHE_PSK Cipher Suites for
             Transport Layer Security (TLS)", RFC 5489,
             DOI 10.17487/RFC5489, March 2009,
             <https://www.rfc-editor.org/info/rfc5489>.

  [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
             Application Protocol (CoAP)", RFC 7252,
             DOI 10.17487/RFC7252, June 2014,
             <https://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, <https://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,
             <https://www.rfc-editor.org/info/rfc7540>.

  [RFC8447]  Salowey, J. and S. Turner, "IANA Registry Updates for TLS
             and DTLS", RFC 8447, DOI 10.17487/RFC8447, August 2018,
             <https://www.rfc-editor.org/info/rfc8447>.
















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Acknowledgements

  The authors would like to thank Ilari Liusvaara, Eric Rescorla, Dan
  Harkins, Russ Housley, Dan Harkins, Martin Thomson, Nikos
  Mavrogiannopoulos, Peter Dettman, Xiaoyin Liu, Joseph Salowey, Sean
  Turner, Dave Garrett, Martin Rex, and Kathleen Moriarty for their
  valuable comments and feedback.

Authors' Addresses

  John Mattsson
  Ericsson AB
  SE-164 80 Stockholm
  Sweden

  Phone: +46 76 115 35 01
  Email: [email protected]


  Daniel Migault
  Ericsson
  8400 Boulevard Decarie
  Montreal, QC  H4P 2N2
  Canada

  Phone: +1 514-452-2160
  Email: [email protected]
























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