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Checking references for intended status: Informational ---------------------------------------------------------------------------- No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group L. Bruckert 3 Internet-Draft J. Merkle 4 Intended status: Informational secunet Security Networks 5 Expires: February 8, 2020 M. Lochter 6 BSI 7 August 7, 2019 9 ECC Brainpool Curves for Transport Layer Security (TLS) Version 1.3 10 draft-bruckert-brainpool-for-tls13-05 12 Abstract 14 ECC Brainpool curves were an option for authentication and key 15 exchange in the Transport Layer Security (TLS) protocol version 1.2, 16 but were deprecated by the IETF for use with TLS version 1.3 because 17 they had little usage. There are no security concerns in using the 18 ECC Brainpool Curves, and there is some interest in using several of 19 these curves in TLS 1.3. 21 This document provides the necessary protocol mechanisms for using 22 ECC Brainpool curves in TLS 1.3. This approach is not endorsed by 23 the IETF. 25 Status of This Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at https://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on February 8, 2020. 42 Copyright Notice 44 Copyright (c) 2019 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (https://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 60 2. Requirements Terminology . . . . . . . . . . . . . . . . . . 3 61 3. Brainpool NamedGroup Types . . . . . . . . . . . . . . . . . 3 62 4. Brainpool SignatureScheme Types . . . . . . . . . . . . . . . 3 63 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 64 6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 65 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 66 7.1. Normative References . . . . . . . . . . . . . . . . . . 5 67 7.2. Informative References . . . . . . . . . . . . . . . . . 6 68 Appendix A. Test Vectors . . . . . . . . . . . . . . . . . . . . 8 69 A.1. 256 Bit Curve . . . . . . . . . . . . . . . . . . . . . . 8 70 A.2. 384 Bit Curve . . . . . . . . . . . . . . . . . . . . . . 9 71 A.3. 512 Bit Curve . . . . . . . . . . . . . . . . . . . . . . 9 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 74 1. Introduction 76 [RFC5639] specifies a new set of elliptic curve groups over finite 77 prime fields for use in cryptographic applications. These groups, 78 denoted as ECC Brainpool curves, were generated in a verifiably 79 pseudo-random way and comply with the security requirements of 80 relevant standards from ISO [ISO1] [ISO2], ANSI [ANSI1], NIST [FIPS], 81 and SecG [SEC2]. 83 [RFC8422] defines the usage of elliptic curves for authentication and 84 key agreement in TLS 1.2 and earlier versions, and [RFC7027] defines 85 the usage of the ECC Brainpool curves for authentication and key 86 exchange in TLS. The latter is applicable to TLS 1.2 and earlier 87 versions, but not to TLS 1.3 that deprecates the ECC Brainpool Curve 88 IDs defined in [RFC7027] due to the lack of widespread deployment 89 However, there is some interest in using these curves in TLS 1.3. 91 The negotiation of ECC Brainpool Curves for key exchange in TLS 1.3 92 according to [RFC8446] requires the definition and assignment of 93 additional NamedGroup IDs. This document provides the necessary 94 definition and assignment of additional SignatureScheme IDs for using 95 three ECC Brainpool Curves from [RFC5639]. 97 This approach is not endorsed by the IETF. Implementers and 98 deployers need to be aware of the strengths and weaknesses of all 99 security mechanisms that they use. 101 2. Requirements Terminology 103 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 104 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 105 document are to be interpreted as described in RFC 2119 [RFC2119]. 107 3. Brainpool NamedGroup Types 109 According to [RFC8446], the name space NamedGroup is used for the 110 negotiation of elliptic curve groups for key exchange during a 111 handshake starting a new TLS session. This document adds new 112 NamedGroup types to three elliptic curves defined in [RFC5639] as 113 follows. 115 enum { 116 brainpoolP256r1tls13(31), 117 brainpoolP384r1tls13(32), 118 brainpoolP512r1tls13(33) 119 } NamedGroup; 121 The encoding of ECDHE parameters for sec256r1, secp384r1, and 122 secp521r1 as defined in section 4.2.8.2 of [RFC8446] also applies to 123 this document. 125 Test vectors for a Diffie-Hellman key exchange using these elliptic 126 curves are provided in Appendix A. 128 4. Brainpool SignatureScheme Types 130 According to [RFC8446], the name space SignatureScheme is used for 131 the negotiation of elliptic curve groups for authentication via the 132 "signature_algorithms" extension. This document adds new 133 SignatureScheme types to three elliptic curves defined in [RFC5639] 134 as follows. 136 enum { 137 ecdsa_brainpoolP256r1tls13_sha256(0x081A), 138 ecdsa_brainpoolP384r1tls13_sha384(0x081B), 139 ecdsa_brainpoolP512r1tls13_sha512(0x081C) 140 } SignatureScheme; 142 This notation is used to clarify that an ECDSA signature is 143 calculated over the hashed message. 145 5. IANA Considerations 147 IANA is requested to update the references for the ECC Brainpool 148 curves listed in the Transport Layer Security (TLS) Parameters 149 registry "TLS Supported Groups" [IANA-TLS] to this document. 151 +-------+----------------------+---------+-------------+-----------+ 152 | Value | Description | DTLS-OK | Recommended | Reference | 153 +-------+----------------------+---------+-------------+-----------+ 154 | 31 | brainpoolP256r1tls13 | Y | N | This doc | 155 | | | | | | 156 | 32 | brainpoolP384r1tls13 | Y | N | This doc | 157 | | | | | | 158 | 33 | brainpoolP512r1tls13 | Y | N | This doc | 159 +-------+----------------------+---------+-------------+-----------+ 161 Table 1 163 IANA is requested to update the references for the ECC Brainpool 164 curves in the Transport Layer Security (TLS) Parameters registry "TLS 165 SignatureScheme" [IANA-TLS] to this document. 167 +--------+----------------------+---------+-------------+-----------+ 168 | Value | Description | DTLS-OK | Recommended | Reference | 169 +--------+----------------------+---------+-------------+-----------+ 170 | 0x081A | ecdsa_brainpoolP256r | Y | N | This doc | 171 | | 1tls13_sha256 | | | | 172 | | | | | | 173 | 0x081B | ecdsa_brainpoolP384r | Y | N | This doc | 174 | | 1tls13_sha384 | | | | 175 | | | | | | 176 | 0x081C | ecdsa_brainpoolP512r | Y | N | This doc | 177 | | 1tls13_sha512 | | | | 178 +--------+----------------------+---------+-------------+-----------+ 180 Table 2 182 6. Security Considerations 184 The security considerations of [RFC8446] apply accordingly. 186 The confidentiality, authenticity and integrity of the TLS 187 communication is limited by the weakest cryptographic primitive 188 applied. In order to achieve a maximum security level when using one 189 of the elliptic curves from Table 1 for key exchange and / or one of 190 the signature algorithms from Table 2 for authentication in TLS, the 191 key derivation function, the algorithms and key lengths of symmetric 192 encryption and message authentication as well as the algorithm, bit 193 length and hash function used for signature generation should be 194 chosen according to the recommendations of [NIST800-57] and 195 [RFC5639]. Furthermore, the private Diffie-Hellman keys should be 196 generated from a random keystream with a length equal to the length 197 of the order of the group E(GF(p)) defined in [RFC5639]. The value 198 of the private Diffie-Hellman keys should be less than the order of 199 the group E(GF(p)). 201 When using ECDHE key agreement with the curves brainpoolP256r1tls13, 202 brainpoolP384r1tls13 or brainpoolP512r1tls13, the peers MUST validate 203 each other's public value Q by ensuring that the point is a valid 204 point on the elliptic curve. 206 Implementations of elliptic curve cryptography for TLS may be 207 susceptible to side-channel attacks. Particular care should be taken 208 for implementations that internally transform curve points to points 209 on the corresponding "twisted curve", using the map (x',y') = (x*Z^2, 210 y*Z^3) with the coefficient Z specified for that curve in [RFC5639], 211 in order to take advantage of an an efficient arithmetic based on the 212 twisted curve's special parameters (A = -3): although the twisted 213 curve itself offers the same level of security as the corresponding 214 random curve (through mathematical equivalence), arithmetic based on 215 small curve parameters may be harder to protect against side-channel 216 attacks. General guidance on resistence of elliptic curve 217 cryptography implementations against side-channel-attacks is given in 218 [BSI1] and [HMV]. 220 7. References 222 7.1. Normative References 224 [IANA-TLS] 225 Internet Assigned Numbers Authority, "Transport Layer 226 Security (TLS) Parameters", 227 . 230 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 231 Requirement Levels", BCP 14, RFC 2119, March 1997. 233 [RFC5639] Lochter, M. and J. Merkle, "Elliptic Curve Cryptography 234 (ECC) Brainpool Standard Curves and Curve Generation", 235 RFC 5639, March 2010. 237 [RFC7027] Merkle, J. and M. Lochter, "Elliptic Curve Cryptography 238 (ECC) Brainpool Curves for Transport Layer Security 239 (TLS)", RFC 7027, DOI 10.17487/RFC7027, October 2013, 240 . 242 [RFC8422] Nir, Y., Josefsson, S., and M. Pegourie-Gonnard, "Elliptic 243 Curve Cryptography (ECC) Cipher Suites for Transport Layer 244 Security (TLS) Versions 1.2 and Earlier", RFC 8422, 245 DOI 10.17487/RFC8422, August 2018, 246 . 248 [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol 249 Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, 250 . 252 7.2. Informative References 254 [ANSI1] American National Standards Institute, "Public Key 255 Cryptography For The Financial Services Industry: The 256 Elliptic Curve Digital Signature Algorithm (ECDSA)", 257 ANSI X9.62, 2005. 259 [BSI1] Bundesamt fuer Sicherheit in der Informationstechnik, 260 "Minimum Requirements for Evaluating Side-Channel Attack 261 Resistance of Elliptic Curve Implementations", July 2011. 263 [FIPS] National Institute of Standards and Technology, "Digital 264 Signature Standard (DSS)", FIPS PUB 186-2, December 1998. 266 [HMV] Hankerson, D., Menezes, A., and S. Vanstone, "Guide to 267 Elliptic Curve Cryptography", Springer Verlag, 2004. 269 [ISO1] International Organization for Standardization, 270 "Information Technology - Security Techniques - Digital 271 Signatures with Appendix - Part 3: Discrete Logarithm 272 Based Mechanisms", ISO/IEC 14888-3, 2006. 274 [ISO2] International Organization for Standardization, 275 "Information Technology - Security Techniques - 276 Cryptographic Techniques Based on Elliptic Curves - Part 277 2: Digital signatures", ISO/IEC 15946-2, 2002. 279 [NIST800-57] 280 National Institute of Standards and Technology, 281 "Recommendation for Key Management - Part 1: General 282 (Revised)", NIST Special Publication 800-57, January 2016. 284 [SEC1] Certicom Research, "Elliptic Curve Cryptography", 285 Standards for Efficient Cryptography (SEC) 1, September 286 2000. 288 [SEC2] Certicom Research, "Recommended Elliptic Curve Domain 289 Parameters", Standards for Efficient Cryptography (SEC) 2, 290 September 2000. 292 Appendix A. Test Vectors 294 This non-normative Appendix provides some test vectors for example 295 Diffie-Hellman key exchanges using each of the curves defined in 296 Table 1 . In all of the following sections the following notation is 297 used: 299 d_A: the secret key of party A 301 x_qA: the x-coordinate of the public key of party A 303 y_qA: the y-coordinate of the public key of party A 305 d_B: the secret key of party B 307 x_qB: the x-coordinate of the public key of party B 309 y_qB: the y-coordinate of the public key of party B 311 x_Z: the x-coordinate of the shared secret that results from 312 completion of the Diffie-Hellman computation, i.e. the hex 313 representation of the pre-master secret 315 y_Z: the y-coordinate of the shared secret that results from 316 completion of the Diffie-Hellman computation 318 The field elements x_qA, y_qA, x_qB, y_qB, x_Z, y_Z are represented 319 as hexadecimal values using the FieldElement-to-OctetString 320 conversion method specified in [SEC1]. 322 A.1. 256 Bit Curve 324 Curve brainpoolP256r1 326 dA = 327 81DB1EE100150FF2EA338D708271BE38300CB54241D79950F77B063039804F1D 329 x_qA = 330 44106E913F92BC02A1705D9953A8414DB95E1AAA49E81D9E85F929A8E3100BE5 332 y_qA = 333 8AB4846F11CACCB73CE49CBDD120F5A900A69FD32C272223F789EF10EB089BDC 335 dB = 336 55E40BC41E37E3E2AD25C3C6654511FFA8474A91A0032087593852D3E7D76BD3 338 x_qB = 339 8D2D688C6CF93E1160AD04CC4429117DC2C41825E1E9FCA0ADDD34E6F1B39F7B 340 y_qB = 341 990C57520812BE512641E47034832106BC7D3E8DD0E4C7F1136D7006547CEC6A 343 x_Z = 344 89AFC39D41D3B327814B80940B042590F96556EC91E6AE7939BCE31F3A18BF2B 346 y_Z = 347 49C27868F4ECA2179BFD7D59B1E3BF34C1DBDE61AE12931648F43E59632504DE 349 A.2. 384 Bit Curve 351 Curve brainpoolP384r1 353 dA = 1E20F5E048A5886F1F157C74E91BDE2B98C8B52D58E5003D57053FC4B0BD6 354 5D6F15EB5D1EE1610DF870795143627D042 356 x_qA = 68B665DD91C195800650CDD363C625F4E742E8134667B767B1B47679358 357 8F885AB698C852D4A6E77A252D6380FCAF068 359 y_qA = 55BC91A39C9EC01DEE36017B7D673A931236D2F1F5C83942D049E3FA206 360 07493E0D038FF2FD30C2AB67D15C85F7FAA59 362 dB = 032640BC6003C59260F7250C3DB58CE647F98E1260ACCE4ACDA3DD869F74E 363 01F8BA5E0324309DB6A9831497ABAC96670 365 x_qB = 4D44326F269A597A5B58BBA565DA5556ED7FD9A8A9EB76C25F46DB69D19 366 DC8CE6AD18E404B15738B2086DF37E71D1EB4 368 y_qB = 62D692136DE56CBE93BF5FA3188EF58BC8A3A0EC6C1E151A21038A42E91 369 85329B5B275903D192F8D4E1F32FE9CC78C48 371 x_Z = 0BD9D3A7EA0B3D519D09D8E48D0785FB744A6B355E6304BC51C229FBBCE2 372 39BBADF6403715C35D4FB2A5444F575D4F42 374 y_Z = 0DF213417EBE4D8E40A5F76F66C56470C489A3478D146DECF6DF0D94BAE9 375 E598157290F8756066975F1DB34B2324B7BD 377 A.3. 512 Bit Curve 379 Curve brainpoolP512r1 381 dA = 16302FF0DBBB5A8D733DAB7141C1B45ACBC8715939677F6A56850A38BD87B 382 D59B09E80279609FF333EB9D4C061231FB26F92EEB04982A5F1D1764CAD5766542 383 2 385 x_qA = 0A420517E406AAC0ACDCE90FCD71487718D3B953EFD7FBEC5F7F27E28C6 386 149999397E91E029E06457DB2D3E640668B392C2A7E737A7F0BF04436D11640FD0 387 9FD 388 y_qA = 72E6882E8DB28AAD36237CD25D580DB23783961C8DC52DFA2EC138AD472 389 A0FCEF3887CF62B623B2A87DE5C588301EA3E5FC269B373B60724F5E82A6AD147F 390 DE7 392 dB = 230E18E1BCC88A362FA54E4EA3902009292F7F8033624FD471B5D8ACE49D1 393 2CFABBC19963DAB8E2F1EBA00BFFB29E4D72D13F2224562F405CB80503666B2542 394 9 396 x_qB = 9D45F66DE5D67E2E6DB6E93A59CE0BB48106097FF78A081DE781CDB31FC 397 E8CCBAAEA8DD4320C4119F1E9CD437A2EAB3731FA9668AB268D871DEDA55A54731 398 99F 400 y_qB = 2FDC313095BCDD5FB3A91636F07A959C8E86B5636A1E930E8396049CB48 401 1961D365CC11453A06C719835475B12CB52FC3C383BCE35E27EF194512B7187628 402 5FA 404 x_Z = A7927098655F1F9976FA50A9D566865DC530331846381C87256BAF322624 405 4B76D36403C024D7BBF0AA0803EAFF405D3D24F11A9B5C0BEF679FE1454B21C4CD 406 1F 408 y_Z = 7DB71C3DEF63212841C463E881BDCF055523BD368240E6C3143BD8DEF8B3 409 B3223B95E0F53082FF5E412F4222537A43DF1C6D25729DDB51620A832BE6A26680 410 A2 412 Authors' Addresses 414 Leonie Bruckert 415 secunet Security Networks 416 Ammonstr. 74 417 01067 Dresden 418 Germany 420 Phone: +49 201 5454 3819 421 EMail: leonie.bruckert@secunet.com 423 Johannes Merkle 424 secunet Security Networks 425 Mergenthaler Allee 77 426 65760 Eschborn 427 Germany 429 Phone: +49 201 5454 3091 430 EMail: johannes.merkle@secunet.com 431 Manfred Lochter 432 BSI 433 Postfach 200363 434 53133 Bonn 435 Germany 437 Phone: +49 228 9582 5643 438 EMail: manfred.lochter@bsi.bund.de