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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: draft-ietf-tls-tls13 has been published as RFC 8446 ** Obsolete normative reference: RFC 4492 (Obsoleted by RFC 8422) ** Obsolete normative reference: RFC 5246 (Obsoleted by RFC 8446) ** Downref: Normative reference to an Informational RFC: RFC 5489 ** Obsolete normative reference: RFC 6347 (Obsoleted by RFC 9147) Summary: 5 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group J. Mattsson 3 Internet-Draft D. Migault 4 Intended status: Standards Track Ericsson 5 Expires: June 10, 2016 December 8, 2015 7 ECDHE_PSK with AES-GCM and AES-CCM Cipher Suites 8 for Transport Layer Security (TLS) 9 draft-mattsson-tls-ecdhe-psk-aead-03 11 Abstract 13 This document defines several new cipher suites for the Transport 14 Layer Security (TLS) protocol. The cipher suites are all based on 15 the Ephemeral Elliptic Curve Diffie-Hellman with Pre-Shared Key 16 (ECDHE_PSK) key exchange together with the Authenticated Encryption 17 with Associated Data (AEAD) algorithms AES-GCM and AES-CCM. PSK 18 provides light and efficient authentication, ECDHE provides perfect 19 forward secrecy, and AES-GCM and AES-CCM provides encryption and 20 integrity protection. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on June 10, 2016. 39 Copyright Notice 41 Copyright (c) 2015 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 2. ECDHE_PSK with AES-GCM and AES-CCM Cipher Suites . . . . . . 3 58 3. Applicable TLS Versions . . . . . . . . . . . . . . . . . . . 3 59 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 60 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 61 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 62 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 63 7.1. Normative References . . . . . . . . . . . . . . . . . . 5 64 7.2. Informative References . . . . . . . . . . . . . . . . . 6 65 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 67 1. Introduction 69 This document defines new cipher suites that provide Pre-Shared Key 70 (PSK) authentication, Perfect Forward Secrecy (PFS), and 71 Authenticated Encryption with Associated Data (AEAD). The cipher 72 suites are defined for version 1.2 or later of the the Transport 73 Layer Security (TLS) [RFC5246] protocol, as well as version 1.2 or 74 later of the Datagram Transport Layer Security (DTLS) protocol 75 [RFC6347]. 77 Pre-Shared Key (PSK) Authentication is widely used in many scenarios. 78 One deployment is 3GPP networks where pre-shared keys are used to 79 authenticate both subscriber and network. Another deployment is 80 Internet of Things where PSK authentication is often preferred for 81 performance and energy efficiency reasons. In both scenarios the 82 endpoints are owned/controlled by a party that provisions the pre- 83 shared keys and makes sure that they provide a high level of entropy. 85 Perfect Forward Secrecy (PFS) is a strongly recommended feature in 86 security protocol design and can be accomplished by using an 87 ephemeral Diffie-Hellman key exchange method. Ephemeral Elliptic 88 Curve Diffie-Hellman (ECDHE) provides PFS with excellent performance 89 and small key sizes. ECDHE is mandatory to implement in both HTTP/2 90 [RFC7540] and CoAP [RFC7252]. 92 AEAD algorithms that combine encryption and integrity protection are 93 strongly recommended [RFC7525] and non-AEAD algorithms are forbidden 94 to use in TLS 1.3 [I-D.ietf-tls-tls13]. The AEAD algorithms 95 considered in this document are AES-GCM and AES-CCM. The use of AES- 96 GCM in TLS is defined in [RFC5288] and the use of AES-CCM is defined 97 in [RFC6655]. 99 [RFC4279] defines Pre-Shared Key (PSK) cipher suites for TLS but does 100 not consider Elliptic Curve Cryptography. [RFC4492] introduces 101 Elliptic Curve Cryptography for TLS but does not consider PSK 102 authentication. [RFC5487] describes the use of AES-GCM in 103 combination with PSK authentication, but does not consider ECDHE. 104 [RFC5489] describes the use of PSK in combination with ECDHE but does 105 not consider AES-GCM or AES-CCM. 107 2. ECDHE_PSK with AES-GCM and AES-CCM Cipher Suites 109 The cipher suites defined in this document are based on the AES-GCM 110 and AES-CCM Authenticated Encryption with Associated Data (AEAD) 111 algorithms AEAD_AES_128_GCM, AEAD_AES_256_GCM, AEAD_AES_128_CCM, and 112 AEAD_AES_256_CCM defined in [RFC5116], and AEAD_AES_128_CCM_8 defined 113 in [RFC6655]. The following cipher suites are defined: 115 TLS_ECDHE_PSK_WITH_AES_128_GCM_SHA256 = {TDB0,TDB1}; 116 TLS_ECDHE_PSK_WITH_AES_256_GCM_SHA384 = {TDB2,TDB3}; 117 TLS_ECDHE_PSK_WITH_AES_128_CCM_8_SHA256 = {TDB4,TDB5}; 118 TLS_ECDHE_PSK_WITH_AES_128_CCM_SHA256 = {TDB6,TDB7}; 119 TLS_ECDHE_PSK_WITH_AES_256_CCM_SHA384 = {TDB8,TDB9}; 121 For the AES-128 cipher suites, the TLS Pseudorandom Function (PRF) 122 with SHA-256 as the hash function SHALL be used and Clients and 123 Servers MUST NOT negotiate curves of less than 255 bits. 125 For the AES-256 cipher suites, the TLS PRF with SHA-384 as the hash 126 function SHALL be used and Clients and Servers MUST NOT negotiate 127 curves of less than 384 bits. 129 When used in TLS 1.2, the keying material is derived as described in 130 [RFC5489] and [RFC5246] and nonces are constructed as described in 131 [RFC5288], and [RFC6655]. When used in TLS 1.3, the keying material 132 is derived as described in [I-D.ietf-tls-tls13], and the nonces are 133 constructed as described in [I-D.ietf-tls-tls13]. 135 3. Applicable TLS Versions 137 The cipher suites defined in this document make use of the 138 authenticated encryption with additional data (AEAD) defined in TLS 139 1.2 [RFC5246] and DTLS 1.2 [RFC6347]. Earlier versions of TLS do not 140 have support for AEAD and consequently, these cipher suites MUST NOT 141 be negotiated in TLS versions prior to 1.2. Clients MUST NOT offer 142 these cipher suites if they do not offer TLS 1.2 or later. Servers, 143 which select an earlier version of TLS MUST NOT select one of these 144 cipher suites. A client MUST treat the selection of these cipher 145 suites in combination with a version of TLS that does not support 146 AEAD (i.e., TLS 1.1 or earlier) as an error and generate a fatal 147 'illegal_parameter' TLS alert. 149 4. IANA Considerations 151 This document defines the following new cipher suites, whose values 152 have been assigned in the TLS Cipher Suite Registry defined by 153 [RFC5246]. 155 TLS_ECDHE_PSK_WITH_AES_128_GCM_SHA256 = {TDB0,TDB1}; 156 TLS_ECDHE_PSK_WITH_AES_256_GCM_SHA384 = {TDB2,TDB3}; 157 TLS_ECDHE_PSK_WITH_AES_128_CCM_8_SHA256 = {TDB4,TDB5}; 158 TLS_ECDHE_PSK_WITH_AES_128_CCM_SHA256 = {TDB6,TDB7}; 159 TLS_ECDHE_PSK_WITH_AES_256_CCM_SHA384 = {TDB8,TDB9}; 161 5. Security Considerations 163 The security considerations in TLS 1.2 [RFC5246], DTLS 1.2 [RFC6347], 164 TLS 1.3 [I-D.ietf-tls-tls13], ECDHE_PSK [RFC5489], AES-GCM [RFC5288], 165 and AES-CCM [RFC6655] apply to this document as well. 167 All the cipher suites defined in this document provide 168 confidentiality, mutual authentication, and perfect forward secrecy. 169 The AES-128 cipher suites provide 128-bit security and the AES-256 170 cipher suites provide at least 192-bit security. However, 171 AES_128_CCM_8 only provides 64-bit security against message forgery 172 and AES_256_GCM and AES_256_CCM only provide 128-bit security against 173 message forgery. 175 Use of Pre-Shared Keys of limited entropy (for example, a PSK that is 176 relatively short, or was chosen by a human and thus may contain less 177 entropy than its length would imply) may allow an active attacker to 178 perform a brute-force attack where the attacker attempts to connect 179 to the server and tries different keys. Passive eavesdropping alone 180 is not sufficient. For these reasons the Pre-Shared Keys used for 181 authentication MUST have a security level equal or higher than the 182 cipher suite used, i.e. at least 128-bit for the AES-128 cipher 183 suites and at least 192-bit for the AES-256 cipher suites. 185 6. Acknowledgements 187 The authors would like to thank Ilari Liusvaara, Eric Rescorla, Dan 188 Harkins, and Russ Housley for their valuable comments and feedback. 190 7. References 192 7.1. Normative References 194 [I-D.ietf-tls-tls13] 195 Rescorla, E., "The Transport Layer Security (TLS) Protocol 196 Version 1.3", draft-ietf-tls-tls13-10 (work in progress), 197 October 2015. 199 [RFC4279] Eronen, P., Ed. and H. Tschofenig, Ed., "Pre-Shared Key 200 Ciphersuites for Transport Layer Security (TLS)", 201 RFC 4279, DOI 10.17487/RFC4279, December 2005, 202 . 204 [RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B. 205 Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites 206 for Transport Layer Security (TLS)", RFC 4492, 207 DOI 10.17487/RFC4492, May 2006, 208 . 210 [RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated 211 Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008, 212 . 214 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 215 (TLS) Protocol Version 1.2", RFC 5246, 216 DOI 10.17487/RFC5246, August 2008, 217 . 219 [RFC5288] Salowey, J., Choudhury, A., and D. McGrew, "AES Galois 220 Counter Mode (GCM) Cipher Suites for TLS", RFC 5288, 221 DOI 10.17487/RFC5288, August 2008, 222 . 224 [RFC5489] Badra, M. and I. Hajjeh, "ECDHE_PSK Cipher Suites for 225 Transport Layer Security (TLS)", RFC 5489, 226 DOI 10.17487/RFC5489, March 2009, 227 . 229 [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer 230 Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, 231 January 2012, . 233 [RFC6655] McGrew, D. and D. Bailey, "AES-CCM Cipher Suites for 234 Transport Layer Security (TLS)", RFC 6655, 235 DOI 10.17487/RFC6655, July 2012, 236 . 238 7.2. Informative References 240 [RFC5487] Badra, M., "Pre-Shared Key Cipher Suites for TLS with SHA- 241 256/384 and AES Galois Counter Mode", RFC 5487, 242 DOI 10.17487/RFC5487, March 2009, 243 . 245 [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained 246 Application Protocol (CoAP)", RFC 7252, 247 DOI 10.17487/RFC7252, June 2014, 248 . 250 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 251 "Recommendations for Secure Use of Transport Layer 252 Security (TLS) and Datagram Transport Layer Security 253 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 254 2015, . 256 [RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext 257 Transfer Protocol Version 2 (HTTP/2)", RFC 7540, 258 DOI 10.17487/RFC7540, May 2015, 259 . 261 Authors' Addresses 263 John Mattsson 264 Ericsson AB 265 SE-164 80 Stockholm 266 Sweden 268 Phone: +46 76 115 35 01 269 Email: john.mattsson@ericsson.com 271 Daniel Migault 272 Ericsson 273 8400 boulevard Decarie 274 Montreal, QC H4P 2N2 275 Canada 277 Phone: +1 514-452-2160 278 Email: daniel.migault@ericsson.com