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'PKCS1' ** Obsolete normative reference: RFC 2246 (Obsoleted by RFC 4346) ** Obsolete normative reference: RFC 4346 (Obsoleted by RFC 5246) ** Obsolete normative reference: RFC 4366 (Obsoleted by RFC 5246, RFC 6066) ** Obsolete normative reference: RFC 5246 (Obsoleted by RFC 8446) -- Possible downref: Non-RFC (?) normative reference: ref. 'SECG-SEC2' == Outdated reference: A later version (-28) exists of draft-ietf-tls-tls13-02 -- Obsolete informational reference (is this intentional?): RFC 4492 (Obsoleted by RFC 8422) Summary: 4 errors (**), 0 flaws (~~), 9 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 TLS Working Group Y. Nir 3 Internet-Draft Check Point 4 Intended status: Standards Track January 13, 2015 5 Expires: July 17, 2015 7 Elliptic Curve Cryptography (ECC) Cipher Suites for Transport Layer 8 Security (TLS) Versions 1.2 and Earlier 9 draft-ietf-tls-rfc4492bis-01 11 Abstract 13 This document describes key exchange algorithms based on Elliptic 14 Curve Cryptography (ECC) for the Transport Layer Security (TLS) 15 protocol. In particular, it specifies the use of Ephemeral Elliptic 16 Curve Diffie-Hellman (ECDHE) key agreement in a TLS handshake and the 17 use of Elliptic Curve Digital Signature Algorithm (ECDSA) as a new 18 authentication mechanism. 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at http://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on July 17, 2015. 37 Copyright Notice 39 Copyright (c) 2015 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 1.1. Conventions Used in This Document . . . . . . . . . . . . 4 56 2. Key Exchange Algorithm . . . . . . . . . . . . . . . . . . . 4 57 2.1. ECDHE_ECDSA . . . . . . . . . . . . . . . . . . . . . . . 5 58 2.2. ECDHE_RSA . . . . . . . . . . . . . . . . . . . . . . . . 6 59 2.3. ECDH_anon . . . . . . . . . . . . . . . . . . . . . . . . 6 60 3. Client Authentication . . . . . . . . . . . . . . . . . . . . 6 61 3.1. ECDSA_sign . . . . . . . . . . . . . . . . . . . . . . . 7 62 4. TLS Extensions for ECC . . . . . . . . . . . . . . . . . . . 7 63 5. Data Structures and Computations . . . . . . . . . . . . . . 8 64 5.1. Client Hello Extensions . . . . . . . . . . . . . . . . . 8 65 5.1.1. Supported Elliptic Curves Extension . . . . . . . . . 10 66 5.1.2. Supported Point Formats Extension . . . . . . . . . . 11 67 5.2. Server Hello Extension . . . . . . . . . . . . . . . . . 12 68 5.3. Server Certificate . . . . . . . . . . . . . . . . . . . 13 69 5.4. Server Key Exchange . . . . . . . . . . . . . . . . . . . 14 70 5.5. Certificate Request . . . . . . . . . . . . . . . . . . . 18 71 5.6. Client Certificate . . . . . . . . . . . . . . . . . . . 19 72 5.7. Client Key Exchange . . . . . . . . . . . . . . . . . . . 20 73 5.8. Certificate Verify . . . . . . . . . . . . . . . . . . . 22 74 5.9. Elliptic Curve Certificates . . . . . . . . . . . . . . . 23 75 5.10. ECDH, ECDSA, and RSA Computations . . . . . . . . . . . . 23 76 6. Cipher Suites . . . . . . . . . . . . . . . . . . . . . . . . 24 77 7. Security Considerations . . . . . . . . . . . . . . . . . . . 25 78 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 79 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26 80 10. Version History for This Draft . . . . . . . . . . . . . . . 26 81 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 82 11.1. Normative References . . . . . . . . . . . . . . . . . . 26 83 11.2. Informative References . . . . . . . . . . . . . . . . . 28 84 Appendix A. Equivalent Curves (Informative) . . . . . . . . . . 28 85 Appendix B. Differences from RFC 4492 . . . . . . . . . . . . . 29 86 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 30 88 1. Introduction 90 Elliptic Curve Cryptography (ECC) is emerging as an attractive 91 public-key cryptosystem, in particular for mobile (i.e., wireless) 92 environments. Compared to currently prevalent cryptosystems such as 93 RSA, ECC offers equivalent security with smaller key sizes. This is 94 illustrated in the following table, based on [Lenstra_Verheul], which 95 gives approximate comparable key sizes for symmetric- and asymmetric- 96 key cryptosystems based on the best-known algorithms for attacking 97 them. 99 +-----------+-----+------------+ 100 | Symmetric | ECC | DH/DSA/RSA | 101 +-----------+-----+------------+ 102 | 80 | 163 | 1024 | 103 | 112 | 233 | 2048 | 104 | 128 | 283 | 3072 | 105 | 192 | 409 | 7680 | 106 | 256 | 571 | 15360 | 107 +-----------+-----+------------+ 109 Table 1: Comparable Key Sizes (in bits) 111 Smaller key sizes result in savings for power, memory, bandwidth, and 112 computational cost that make ECC especially attractive for 113 constrained environments. 115 This document describes additions to TLS to support ECC, applicable 116 to TLS versions 1.0 [RFC2246], 1.1 [RFC4346], and 1.2 [RFC5246]. The 117 use of ECC in TLS 1.3 is defined in [I-D.ietf-tls-tls13], and is 118 explicitly out of scope for this document. In particular, this 119 document defines: 121 o the use of the Elliptic Curve Diffie-Hellman key agreement scheme 122 with ephemeral keys to establish the TLS premaster secret, and 123 o the use of ECDSA certificates for authentication of TLS peers. 125 The remainder of this document is organized as follows. Section 2 126 provides an overview of ECC-based key exchange algorithms for TLS. 127 Section 3 describes the use of ECC certificates for client 128 authentication. TLS extensions that allow a client to negotiate the 129 use of specific curves and point formats are presented in Section 4. 130 Section 5 specifies various data structures needed for an ECC-based 131 handshake, their encoding in TLS messages, and the processing of 132 those messages. Section 6 defines ECC-based cipher suites and 133 identifies a small subset of these as recommended for all 134 implementations of this specification. Section 7 discusses security 135 considerations. Section 8 describes IANA considerations for the name 136 spaces created by this document's predecessor. Section 9 gives 137 acknowledgements. Appendix B provides differences from [RFC4492], 138 the document that this one replaces. 140 Implementation of this specification requires familiarity with TLS, 141 TLS extensions [RFC4366], and ECC (TBD: reference Wikipedia here?). 143 1.1. Conventions Used in This Document 145 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 146 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 147 document are to be interpreted as described in [RFC2119]. 149 2. Key Exchange Algorithm 151 This document defines three new ECC-based key exchange algorithms for 152 TLS. All of them use Ephemeral ECDH (ECDHE) to compute the TLS 153 premaster secret, and they differ only in the mechanism (if any) used 154 to authenticate them. The derivation of the TLS master secret from 155 the premaster secret and the subsequent generation of bulk 156 encryption/MAC keys and initialization vectors is independent of the 157 key exchange algorithm and not impacted by the introduction of ECC. 159 The table below summarizes the new key exchange algorithms, which 160 mimic DHE_DSS, DHE_RSA, and DH_anon, respectively. 162 +-------------+---------------------------------------+ 163 | Algorithm | Description | 164 +-------------+---------------------------------------+ 165 | ECDHE_ECDSA | Ephemeral ECDH with ECDSA signatures. | 166 | ECDHE_RSA | Ephemeral ECDH with RSA signatures. | 167 | ECDH_anon | Anonymous ECDH, no signatures. | 168 +-------------+---------------------------------------+ 170 Table 2: ECC Key Exchange Algorithms 172 The ECDHE_ECDSA and ECDHE_RSA key exchange mechanisms provide forward 173 secrecy. With ECDHE_RSA, a server can reuse its existing RSA 174 certificate and easily comply with a constrained client's elliptic 175 curve preferences (see Section 4). However, the computational cost 176 incurred by a server is higher for ECDHE_RSA than for the traditional 177 RSA key exchange, which does not provide forward secrecy. 179 The anonymous key exchange algorithm does not provide authentication 180 of the server or the client. Like other anonymous TLS key exchanges, 181 it is subject to man-in-the-middle attacks. Implementations of this 182 algorithm SHOULD provide authentication by other means. 184 Note that there is no structural difference between ECDH and ECDSA 185 keys. A certificate issuer may use X.509 v3 keyUsage and 186 extendedKeyUsage extensions to restrict the use of an ECC public key 187 to certain computations. This document refers to an ECC key as ECDH- 188 capable if its use in ECDH is permitted. ECDSA-capable is defined 189 similarly. 191 Client Server 192 ------ ------ 193 ClientHello --------> 194 ServerHello 195 Certificate* 196 ServerKeyExchange* 197 CertificateRequest*+ 198 <-------- ServerHelloDone 199 Certificate*+ 200 ClientKeyExchange 201 CertificateVerify*+ 202 [ChangeCipherSpec] 203 Finished --------> 204 [ChangeCipherSpec] 205 <-------- Finished 206 Application Data <-------> Application Data 207 * message is not sent under some conditions 208 + message is not sent unless client authentication 209 is desired 211 Figure 1: Message flow in a full TLS handshake 213 Figure 1 shows all messages involved in the TLS key establishment 214 protocol (aka full handshake). The addition of ECC has direct impact 215 only on the ClientHello, the ServerHello, the server's Certificate 216 message, the ServerKeyExchange, the ClientKeyExchange, the 217 CertificateRequest, the client's Certificate message, and the 218 CertificateVerify. Next, we describe each ECC key exchange algorithm 219 in greater detail in terms of the content and processing of these 220 messages. For ease of exposition, we defer discussion of client 221 authentication and associated messages (identified with a + in 222 Figure 1) until Section 3 and of the optional ECC-specific extensions 223 (which impact the Hello messages) until Section 4. 225 2.1. ECDHE_ECDSA 227 In ECDHE_ECDSA, the server's certificate MUST contain an ECDSA- 228 capable public key and be signed with ECDSA. 230 The server sends its ephemeral ECDH public key and a specification of 231 the corresponding curve in the ServerKeyExchange message. These 232 parameters MUST be signed with ECDSA using the private key 233 corresponding to the public key in the server's Certificate. 235 The client generates an ECDH key pair on the same curve as the 236 server's ephemeral ECDH key and sends its public key in the 237 ClientKeyExchange message. 239 Both client and server perform an ECDH operation Section 5.10 and use 240 the resultant shared secret as the premaster secret. 242 2.2. ECDHE_RSA 244 This key exchange algorithm is the same as ECDHE_ECDSA except that 245 the server's certificate MUST contain an RSA public key authorized 246 for signing, and that the signature in the ServerKeyExchange message 247 must be computed with the corresponding RSA private key. The server 248 certificate MUST be signed with RSA. 250 2.3. ECDH_anon 252 In ECDH_anon, the server's Certificate, the CertificateRequest, the 253 client's Certificate, and the CertificateVerify messages MUST NOT be 254 sent. 256 The server MUST send an ephemeral ECDH public key and a specification 257 of the corresponding curve in the ServerKeyExchange message. These 258 parameters MUST NOT be signed. 260 The client generates an ECDH key pair on the same curve as the 261 server's ephemeral ECDH key and sends its public key in the 262 ClientKeyExchange message. 264 Both client and server perform an ECDH operation and use the 265 resultant shared secret as the premaster secret. All ECDH 266 calculations are performed as specified in Section 5.10. 268 Note that while the ECDHE_ECDSA and ECDHE_RSA key exchange algorithms 269 require the server's certificate to be signed with a particular 270 signature scheme, this specification (following the similar cases of 271 DHE_DSS, and DHE_RSA in the TLS base documents) does not impose 272 restrictions on signature schemes used elsewhere in the certificate 273 chain. (Often such restrictions will be useful, and it is expected 274 that this will be taken into account in certification authorities' 275 signing practices. However, such restrictions are not strictly 276 required in general: Even if it is beyond the capabilities of a 277 client to completely validate a given chain, the client may be able 278 to validate the server's certificate by relying on a trusted 279 certification authority whose certificate appears as one of the 280 intermediate certificates in the chain.) 282 3. Client Authentication 284 This document defines a client authentication mechanism, named after 285 the type of client certificate involved: ECDSA_sign. The ECDSA_sign 286 mechanism is usable with any of the non-anonymous ECC key exchange 287 algorithms described in Section 2 as well as other non-anonymous 288 (non-ECC) key exchange algorithms defined in TLS. 290 The server can request ECC-based client authentication by including 291 this certificate type in its CertificateRequest message. The client 292 must check if it possesses a certificate appropriate for the method 293 suggested by the server and is willing to use it for authentication. 295 If these conditions are not met, the client should send a client 296 Certificate message containing no certificates. In this case, the 297 ClientKeyExchange should be sent as described in Section 2, and the 298 CertificateVerify should not be sent. If the server requires client 299 authentication, it may respond with a fatal handshake failure alert. 301 If the client has an appropriate certificate and is willing to use it 302 for authentication, it must send that certificate in the client's 303 Certificate message (as per Section 5.6) and prove possession of the 304 private key corresponding to the certified key. The process of 305 determining an appropriate certificate and proving possession is 306 different for each authentication mechanism and described below. 308 NOTE: It is permissible for a server to request (and the client to 309 send) a client certificate of a different type than the server 310 certificate. 312 3.1. ECDSA_sign 314 To use this authentication mechanism, the client MUST possess a 315 certificate containing an ECDSA-capable public key and signed with 316 ECDSA. 318 The client proves possession of the private key corresponding to the 319 certified key by including a signature in the CertificateVerify 320 message as described in Section 5.8. 322 4. TLS Extensions for ECC 324 Two new TLS extensions are defined in this specification: (i) the 325 Supported Elliptic Curves Extension, and (ii) the Supported Point 326 Formats Extension. These allow negotiating the use of specific 327 curves and point formats (e.g., compressed vs. uncompressed, 328 respectively) during a handshake starting a new session. These 329 extensions are especially relevant for constrained clients that may 330 only support a limited number of curves or point formats. They 331 follow the general approach outlined in [RFC4366]; message details 332 are specified in Section 5. The client enumerates the curves it 333 supports and the point formats it can parse by including the 334 appropriate extensions in its ClientHello message. The server 335 similarly enumerates the point formats it can parse by including an 336 extension in its ServerHello message. 338 A TLS client that proposes ECC cipher suites in its ClientHello 339 message SHOULD include these extensions. Servers implementing ECC 340 cipher suites MUST support these extensions, and when a client uses 341 these extensions, servers MUST NOT negotiate the use of an ECC cipher 342 suite unless they can complete the handshake while respecting the 343 choice of curves and compression techniques specified by the client. 344 This eliminates the possibility that a negotiated ECC handshake will 345 be subsequently aborted due to a client's inability to deal with the 346 server's EC key. 348 The client MUST NOT include these extensions in the ClientHello 349 message if it does not propose any ECC cipher suites. A client that 350 proposes ECC cipher suites may choose not to include these 351 extensions. In this case, the server is free to choose any one of 352 the elliptic curves or point formats listed in Section 5. That 353 section also describes the structure and processing of these 354 extensions in greater detail. 356 In the case of session resumption, the server simply ignores the 357 Supported Elliptic Curves Extension and the Supported Point Formats 358 Extension appearing in the current ClientHello message. These 359 extensions only play a role during handshakes negotiating a new 360 session. 362 5. Data Structures and Computations 364 This section specifies the data structures and computations used by 365 ECC-based key mechanisms specified in the previous three sections. 366 The presentation language used here is the same as that used in TLS. 367 Since this specification extends TLS, these descriptions should be 368 merged with those in the TLS specification and any others that extend 369 TLS. This means that enum types may not specify all possible values, 370 and structures with multiple formats chosen with a select() clause 371 may not indicate all possible cases. 373 5.1. Client Hello Extensions 375 This section specifies two TLS extensions that can be included with 376 the ClientHello message as described in [RFC4366], the Supported 377 Elliptic Curves Extension and the Supported Point Formats Extension. 379 When these extensions are sent: 381 The extensions SHOULD be sent along with any ClientHello message that 382 proposes ECC cipher suites. 384 Meaning of these extensions: 386 These extensions allow a client to enumerate the elliptic curves it 387 supports and/or the point formats it can parse. 389 Structure of these extensions: 391 The general structure of TLS extensions is described in [RFC4366], 392 and this specification adds two new types to ExtensionType. 394 enum { elliptic_curves(10), ec_point_formats(11) } ExtensionType; 396 elliptic_curves (Supported Elliptic Curves Extension): Indicates the 397 set of elliptic curves supported by the client. For this 398 extension, the opaque extension_data field contains 399 EllipticCurveList. See Section 5.1.1 for details. 400 ec_point_formats (Supported Point Formats Extension): Indicates the 401 set of point formats that the client can parse. For this 402 extension, the opaque extension_data field contains 403 ECPointFormatList. See Section 5.1.2 for details. 405 Actions of the sender: 407 A client that proposes ECC cipher suites in its ClientHello message 408 appends these extensions (along with any others), enumerating the 409 curves it supports and the point formats it can parse. Clients 410 SHOULD send both the Supported Elliptic Curves Extension and the 411 Supported Point Formats Extension. If the Supported Point Formats 412 Extension is indeed sent, it MUST contain the value 0 (uncompressed) 413 as one of the items in the list of point formats. 415 Actions of the receiver: 417 A server that receives a ClientHello containing one or both of these 418 extensions MUST use the client's enumerated capabilities to guide its 419 selection of an appropriate cipher suite. One of the proposed ECC 420 cipher suites must be negotiated only if the server can successfully 421 complete the handshake while using the curves and point formats 422 supported by the client (cf. Section 5.3 and Section 5.4). 424 NOTE: A server participating in an ECDHE-ECDSA key exchange may use 425 different curves for (i) the ECDSA key in its certificate, and (ii) 426 the ephemeral ECDH key in the ServerKeyExchange message. The server 427 must consider the extensions in both cases. 429 If a server does not understand the Supported Elliptic Curves 430 Extension, does not understand the Supported Point Formats Extension, 431 or is unable to complete the ECC handshake while restricting itself 432 to the enumerated curves and point formats, it MUST NOT negotiate the 433 use of an ECC cipher suite. Depending on what other cipher suites 434 are proposed by the client and supported by the server, this may 435 result in a fatal handshake failure alert due to the lack of common 436 cipher suites. 438 5.1.1. Supported Elliptic Curves Extension 440 enum { 441 sect163k1 (1), sect163r1 (2), sect163r2 (3), 442 sect193r1 (4), sect193r2 (5), sect233k1 (6), 443 sect233r1 (7), sect239k1 (8), sect283k1 (9), 444 sect283r1 (10), sect409k1 (11), sect409r1 (12), 445 sect571k1 (13), sect571r1 (14), secp160k1 (15), 446 secp160r1 (16), secp160r2 (17), secp192k1 (18), 447 secp192r1 (19), secp224k1 (20), secp224r1 (21), 448 secp256k1 (22), secp256r1 (23), secp384r1 (24), 449 secp521r1 (25), 450 reserved (0xFE00..0xFEFF), 451 arbitrary_explicit_prime_curves(0xFF01), 452 arbitrary_explicit_char2_curves(0xFF02), 453 (0xFFFF) 454 } NamedCurve; 456 sect163k1, etc: Indicates support of the corresponding named curve or 457 class of explicitly defined curves. The named curves defined here 458 are those specified in SEC 2 [SECG-SEC2]. Note that many of these 459 curves are also recommended in ANSI X9.62 [ANSI.X9-62.2005] and FIPS 460 186-4 [FIPS.186-4]. Values 0xFE00 through 0xFEFF are reserved for 461 private use. Values 0xFF01 and 0xFF02 indicate that the client 462 supports arbitrary prime and characteristic-2 curves, respectively 463 (the curve parameters must be encoded explicitly in ECParameters). 465 The NamedCurve name space is maintained by IANA. See Section 8 for 466 information on how new value assignments are added. 468 struct { 469 NamedCurve elliptic_curve_list<1..2^16-1> 470 } EllipticCurveList; 472 Items in elliptic_curve_list are ordered according to the client's 473 preferences (favorite choice first). 475 As an example, a client that only supports secp192r1 (aka NIST P-192; 476 value 19 = 0x0013) and secp224r1 (aka NIST P-224; value 21 = 0x0015) 477 and prefers to use secp192r1 would include a TLS extension consisting 478 of the following octets. Note that the first two octets indicate the 479 extension type (Supported Elliptic Curves Extension): 481 00 0A 00 06 00 04 00 13 00 15 483 A client that supports arbitrary explicit characteristic-2 curves 484 (value 0xFF02) would include an extension consisting of the following 485 octets: 487 00 0A 00 04 00 02 FF 02 489 5.1.2. Supported Point Formats Extension 491 enum { uncompressed (0), ansiX962_compressed_prime (1), 492 ansiX962_compressed_char2 (2), reserved (248..255) 493 } ECPointFormat; 494 struct { 495 ECPointFormat ec_point_format_list<1..2^8-1> 496 } ECPointFormatList; 498 Three point formats are included in the definition of ECPointFormat 499 above. The uncompressed point format is the default format in that 500 implementations of this document MUST support it for all of their 501 supported curves. Compressed point formats reduce bandwidth by 502 including only the x-coordinate and a single bit of the y-coordinate 503 of the point. Implementations of this document MAY support the 504 ansiX962_compressed_prime and ansiX962_compressed_char2 formats, 505 where the former applies only to prime curves and the latter applies 506 only to characteristic-2 curves. (These formats are specified in 507 [ANSI.X9-62.2005].) Values 248 through 255 are reserved for private 508 use. 510 The ECPointFormat name space is maintained by IANA. See Section 8 511 for information on how new value assignments are added. 513 Items in ec_point_format_list are ordered according to the client's 514 preferences (favorite choice first). 516 A client that can parse only the uncompressed point format (value 0) 517 includes an extension consisting of the following octets; note that 518 the first two octets indicate the extension type (Supported Point 519 Formats Extension): 521 00 0B 00 02 01 00 523 A client that in the case of prime fields prefers the compressed 524 format (ansiX962_compressed_prime, value 1) over the uncompressed 525 format (value 0), but in the case of characteristic-2 fields prefers 526 the uncompressed format (value 0) over the compressed format 527 (ansiX962_compressed_char2, value 2), may indicate these preferences 528 by including an extension consisting of the following octets: 530 00 0B 00 04 03 01 00 02 532 5.2. Server Hello Extension 534 This section specifies a TLS extension that can be included with the 535 ServerHello message as described in [RFC4366], the Supported Point 536 Formats Extension. 538 When this extension is sent: 540 The Supported Point Formats Extension is included in a ServerHello 541 message in response to a ClientHello message containing the Supported 542 Point Formats Extension when negotiating an ECC cipher suite. 544 Meaning of this extension: 546 This extension allows a server to enumerate the point formats it can 547 parse (for the curve that will appear in its ServerKeyExchange 548 message when using the ECDHE_ECDSA, ECDHE_RSA, or ECDH_anon key 549 exchange algorithm. 551 Structure of this extension: 553 The server's Supported Point Formats Extension has the same structure 554 as the client's Supported Point Formats Extension (see 555 Section 5.1.2). Items in ec_point_format_list here are ordered 556 according to the server's preference (favorite choice first). Note 557 that the server may include items that were not found in the client's 558 list (e.g., the server may prefer to receive points in compressed 559 format even when a client cannot parse this format: the same client 560 may nevertheless be capable of outputting points in compressed 561 format). 563 Actions of the sender: 565 A server that selects an ECC cipher suite in response to a 566 ClientHello message including a Supported Point Formats Extension 567 appends this extension (along with others) to its ServerHello 568 message, enumerating the point formats it can parse. The Supported 569 Point Formats Extension, when used, MUST contain the value 0 570 (uncompressed) as one of the items in the list of point formats. 572 Actions of the receiver: 574 A client that receives a ServerHello message containing a Supported 575 Point Formats Extension MUST respect the server's choice of point 576 formats during the handshake (cf. Section 5.6 and Section 5.7). If 577 no Supported Point Formats Extension is received with the 578 ServerHello, this is equivalent to an extension allowing only the 579 uncompressed point format. 581 5.3. Server Certificate 583 When this message is sent: 585 This message is sent in all non-anonymous ECC-based key exchange 586 algorithms. 588 Meaning of this message: 590 This message is used to authentically convey the server's static 591 public key to the client. The following table shows the server 592 certificate type appropriate for each key exchange algorithm. ECC 593 public keys MUST be encoded in certificates as described in 594 Section 5.9. 596 NOTE: The server's Certificate message is capable of carrying a chain 597 of certificates. The restrictions mentioned in Table 3 apply only to 598 the server's certificate (first in the chain). 600 +-------------+-----------------------------------------------------+ 601 | Algorithm | Server Certificate Type | 602 +-------------+-----------------------------------------------------+ 603 | ECDHE_ECDSA | Certificate MUST contain an ECDSA-capable public | 604 | | key. It MUST be signed with ECDSA. | 605 | ECDHE_RSA | Certificate MUST contain an RSA public key | 606 | | authorized for use in digital signatures. It MUST | 607 | | be signed with RSA. | 608 +-------------+-----------------------------------------------------+ 610 Table 3: Server Certificate Types 612 Structure of this message: 614 Identical to the TLS Certificate format. 616 Actions of the sender: 618 The server constructs an appropriate certificate chain and conveys it 619 to the client in the Certificate message. If the client has used a 620 Supported Elliptic Curves Extension, the public key in the server's 621 certificate MUST respect the client's choice of elliptic curves; in 622 particular, the public key MUST employ a named curve (not the same 623 curve as an explicit curve) unless the client has indicated support 624 for explicit curves of the appropriate type. If the client has used 625 a Supported Point Formats Extension, both the server's public key 626 point and (in the case of an explicit curve) the curve's base point 627 MUST respect the client's choice of point formats. (A server that 628 cannot satisfy these requirements MUST NOT choose an ECC cipher suite 629 in its ServerHello message.) 631 Actions of the receiver: 633 The client validates the certificate chain, extracts the server's 634 public key, and checks that the key type is appropriate for the 635 negotiated key exchange algorithm. (A possible reason for a fatal 636 handshake failure is that the client's capabilities for handling 637 elliptic curves and point formats are exceeded; cf. Section 5.1.) 639 5.4. Server Key Exchange 641 When this message is sent: 643 This message is sent when using the ECDHE_ECDSA, ECDHE_RSA, and 644 ECDH_anon key exchange algorithms. 646 Meaning of this message: 648 This message is used to convey the server's ephemeral ECDH public key 649 (and the corresponding elliptic curve domain parameters) to the 650 client. 652 Structure of this message: 654 enum { explicit_prime (1), explicit_char2 (2), 655 named_curve (3), reserved(248..255) } ECCurveType; 657 explicit_prime: Indicates the elliptic curve domain parameters are 658 conveyed verbosely, and the underlying finite field is a prime 659 field. 660 explicit_char2: Indicates the elliptic curve domain parameters are 661 conveyed verbosely, and the underlying finite field is a 662 characteristic-2 field. 663 named_curve: Indicates that a named curve is used. This option 664 SHOULD be used when applicable. 666 Values 248 through 255 are reserved for private use. 668 The ECCurveType name space is maintained by IANA. See Section 8 for 669 information on how new value assignments are added. 671 struct { 672 opaque a <1..2^8-1>; 673 opaque b <1..2^8-1>; 674 } ECCurve; 676 a, b: These parameters specify the coefficients of the elliptic 677 curve. Each value contains the byte string representation of a 678 field element following the conversion routine in Section 4.3.3 of 679 [ANSI.X9-62.2005]. 681 struct { 682 opaque point <1..2^8-1>; 683 } ECPoint; 684 point: This is the byte string representation of an elliptic curve 685 point following the conversion routine in Section 4.3.6 of 686 [ANSI.X9-62.2005]. This byte string may represent an elliptic 687 curve point in uncompressed or compressed format; it MUST conform 688 to what the client has requested through a Supported Point Formats 689 Extension if this extension was used. 691 enum { 692 ec_basis_trinomial(1), ec_basis_pentanomial(2), 693 (255) 694 } ECBasisType; 695 ec_basis_trinomial: Indicates representation of a characteristic-2 696 field using a trinomial basis. 697 ec_basis_pentanomial: Indicates representation of a characteristic-2 698 field using a pentanomial basis. 700 struct { 701 ECCurveType curve_type; 702 select (curve_type) { 703 case explicit_prime: 704 opaque prime_p <1..2^8-1>; 705 ECCurve curve; 706 ECPoint base; 707 opaque order <1..2^8-1>; 708 opaque cofactor <1..2^8-1>; 709 case explicit_char2: 710 uint16 m; 711 ECBasisType basis; 712 select (basis) { 713 case ec_basis_trinomial: 714 opaque k <1..2^8-1>; 715 case ec_basis_pentanomial: 716 opaque k1 <1..2^8-1>; 717 opaque k2 <1..2^8-1>; 718 opaque k3 <1..2^8-1>; 719 }; 720 ECCurve curve; 721 ECPoint base; 722 opaque order <1..2^8-1>; 723 opaque cofactor <1..2^8-1>; 724 case named_curve: 725 NamedCurve namedcurve; 726 }; 727 } ECParameters; 728 curve_type: This identifies the type of the elliptic curve domain 729 parameters. 730 prime_p: This is the odd prime defining the field Fp. 731 curve: Specifies the coefficients a and b of the elliptic curve E. 732 base: Specifies the base point G on the elliptic curve. 733 order: Specifies the order n of the base point. 734 cofactor: Specifies the cofactor h = #E(Fq)/n, where #E(Fq) 735 represents the number of points on the elliptic curve E defined 736 over the field Fq (either Fp or F2^m). 737 m: This is the degree of the characteristic-2 field F2^m. 738 k: The exponent k for the trinomial basis representation x^m + x^k+1. 739 k1, k2, k3: The exponents for the pentanomial representation x^m + 740 x^k3 + x^k2 + x^k1 + 1 (such that k3 > k2 > k1). 741 namedcurve: Specifies a recommended set of elliptic curve domain 742 parameters. All those values of NamedCurve are allowed that refer 743 to a specific curve. Values of NamedCurve that indicate support 744 for a class of explicitly defined curves are not allowed here 745 (they are only permissible in the ClientHello extension); this 746 applies to arbitrary_explicit_prime_curves(0xFF01) and 747 arbitrary_explicit_char2_curves(0xFF02). 749 struct { 750 ECParameters curve_params; 751 ECPoint public; 752 } ServerECDHParams; 753 curve_params: Specifies the elliptic curve domain parameters 754 associated with the ECDH public key. 755 public: The ephemeral ECDH public key. 757 The ServerKeyExchange message is extended as follows. 759 enum { ec_diffie_hellman } KeyExchangeAlgorithm; 761 ec_diffie_hellman: Indicates the ServerKeyExchange message contains 762 an ECDH public key. 764 select (KeyExchangeAlgorithm) { 765 case ec_diffie_hellman: 766 ServerECDHParams params; 767 Signature signed_params; 768 } ServerKeyExchange; 770 params: Specifies the ECDH public key and associated domain 771 parameters. 772 signed_params: A hash of the params, with the signature appropriate 773 to that hash applied. The private key corresponding to the 774 certified public key in the server's Certificate message is used 775 for signing. 777 enum { ecdsa } SignatureAlgorithm; 778 select (SignatureAlgorithm) { 779 case ecdsa: 780 digitally-signed struct { 781 opaque sha_hash[sha_size]; 782 }; 783 } Signature; 784 ServerKeyExchange.signed_params.sha_hash 785 SHA(ClientHello.random + ServerHello.random + 786 ServerKeyExchange.params); 788 NOTE: SignatureAlgorithm is "rsa" for the ECDHE_RSA key exchange 789 algorithm and "anonymous" for ECDH_anon. These cases are defined in 790 TLS. SignatureAlgorithm is "ecdsa" for ECDHE_ECDSA. ECDSA 791 signatures are generated and verified as described in Section 5.10, 792 and SHA in the above template for sha_hash accordingly may denote a 793 hash algorithm other than SHA-1. As per ANSI X9.62, an ECDSA 794 signature consists of a pair of integers, r and s. The digitally- 795 signed element is encoded as an opaque vector <0..2^16-1>, the 796 contents of which are the DER encoding corresponding to the following 797 ASN.1 notation. 799 Ecdsa-Sig-Value ::= SEQUENCE { 800 r INTEGER, 801 s INTEGER 802 } 804 Actions of the sender: 806 The server selects elliptic curve domain parameters and an ephemeral 807 ECDH public key corresponding to these parameters according to the 808 ECKAS-DH1 scheme from IEEE 1363 [IEEE.P1363.1998]. It conveys this 809 information to the client in the ServerKeyExchange message using the 810 format defined above. 812 Actions of the receiver: 814 The client verifies the signature (when present) and retrieves the 815 server's elliptic curve domain parameters and ephemeral ECDH public 816 key from the ServerKeyExchange message. (A possible reason for a 817 fatal handshake failure is that the client's capabilities for 818 handling elliptic curves and point formats are exceeded; cf. 819 Section 5.1.) 821 5.5. Certificate Request 823 When this message is sent: 825 This message is sent when requesting client authentication. 827 Meaning of this message: 829 The server uses this message to suggest acceptable client 830 authentication methods. 832 Structure of this message: 834 The TLS CertificateRequest message is extended as follows. 836 enum { 837 ecdsa_sign(64), rsa_fixed_ecdh(65), 838 ecdsa_fixed_ecdh(66), (255) 839 } ClientCertificateType; 841 ecdsa_sign, etc. Indicates that the server would like to use the 842 corresponding client authentication method specified in Section 3. 844 Actions of the sender: 846 The server decides which client authentication methods it would like 847 to use, and conveys this information to the client using the format 848 defined above. 850 Actions of the receiver: 852 The client determines whether it has a suitable certificate for use 853 with any of the requested methods and whether to proceed with client 854 authentication. 856 5.6. Client Certificate 858 When this message is sent: 860 This message is sent in response to a CertificateRequest when a 861 client has a suitable certificate and has decided to proceed with 862 client authentication. (Note that if the server has used a Supported 863 Point Formats Extension, a certificate can only be considered 864 suitable for use with the ECDSA_sign, RSA_fixed_ECDH, and 865 ECDSA_fixed_ECDH authentication methods if the public key point 866 specified in it respects the server's choice of point formats. If no 867 Supported Point Formats Extension has been used, a certificate can 868 only be considered suitable for use with these authentication methods 869 if the point is represented in uncompressed point format.) 871 Meaning of this message: 873 This message is used to authentically convey the client's static 874 public key to the server. The following table summarizes what client 875 certificate types are appropriate for the ECC-based client 876 authentication mechanisms described in Section 3. ECC public keys 877 must be encoded in certificates as described in Section 5.9. 879 NOTE: The client's Certificate message is capable of carrying a chain 880 of certificates. The restrictions mentioned in Table 4 apply only to 881 the client's certificate (first in the chain). 883 +------------------+------------------------------------------------+ 884 | Client | Client Certificate Type | 885 | Authentication | | 886 | Method | | 887 +------------------+------------------------------------------------+ 888 | ECDSA_sign | Certificate MUST contain an ECDSA-capable | 889 | | public key and be signed with ECDSA. | 890 | ECDSA_fixed_ECDH | Certificate MUST contain an ECDH-capable | 891 | | public key on the same elliptic curve as the | 892 | | server's long-term ECDH key. This certificate | 893 | | MUST be signed with ECDSA. | 894 | RSA_fixed_ECDH | Certificate MUST contain an ECDH-capable | 895 | | public key on the same elliptic curve as the | 896 | | server's long-term ECDH key. This certificate | 897 | | MUST be signed with RSA. | 898 +------------------+------------------------------------------------+ 900 Table 4: Client Certificate Types 902 Structure of this message: 904 Identical to the TLS client Certificate format. 906 Actions of the sender: 908 The client constructs an appropriate certificate chain, and conveys 909 it to the server in the Certificate message. 911 Actions of the receiver: 913 The TLS server validates the certificate chain, extracts the client's 914 public key, and checks that the key type is appropriate for the 915 client authentication method. 917 5.7. Client Key Exchange 919 When this message is sent: 921 This message is sent in all key exchange algorithms. If client 922 authentication with ECDSA_fixed_ECDH or RSA_fixed_ECDH is used, this 923 message is empty. Otherwise, it contains the client's ephemeral ECDH 924 public key. 926 Meaning of the message: 928 This message is used to convey ephemeral data relating to the key 929 exchange belonging to the client (such as its ephemeral ECDH public 930 key). 932 Structure of this message: 934 The TLS ClientKeyExchange message is extended as follows. 936 enum { implicit, explicit } PublicValueEncoding; 938 implicit, explicit: For ECC cipher suites, this indicates whether 939 the client's ECDH public key is in the client's certificate 940 ("implicit") or is provided, as an ephemeral ECDH public key, in 941 the ClientKeyExchange message ("explicit"). (This is "explicit" 942 in ECC cipher suites except when the client uses the 943 ECDSA_fixed_ECDH or RSA_fixed_ECDH client authentication 944 mechanism.) 946 struct { 947 select (PublicValueEncoding) { 948 case implicit: struct { }; 949 case explicit: ECPoint ecdh_Yc; 950 } ecdh_public; 951 } ClientECDiffieHellmanPublic; 952 ecdh_Yc: Contains the client's ephemeral ECDH public key as a byte 953 string ECPoint.point, which may represent an elliptic curve point 954 in uncompressed or compressed format. Here, the format MUST 955 conform to what the server has requested through a Supported Point 956 Formats Extension if this extension was used, and MUST be 957 uncompressed if this extension was not used. 959 struct { 960 select (KeyExchangeAlgorithm) { 961 case ec_diffie_hellman: ClientECDiffieHellmanPublic; 962 } exchange_keys; 963 } ClientKeyExchange; 965 Actions of the sender: 967 The client selects an ephemeral ECDH public key corresponding to the 968 parameters it received from the server according to the ECKAS-DH1 969 scheme from IEEE 1363. It conveys this information to the client in 970 the ClientKeyExchange message using the format defined above. 972 Actions of the receiver: 974 The server retrieves the client's ephemeral ECDH public key from the 975 ClientKeyExchange message and checks that it is on the same elliptic 976 curve as the server's ECDH key. 978 5.8. Certificate Verify 980 When this message is sent: 982 This message is sent when the client sends a client certificate 983 containing a public key usable for digital signatures, e.g., when the 984 client is authenticated using the ECDSA_sign mechanism. 986 Meaning of the message: 988 This message contains a signature that proves possession of the 989 private key corresponding to the public key in the client's 990 Certificate message. 992 Structure of this message: 994 The TLS CertificateVerify message and the underlying Signature type 995 are defined in the TLS base specifications, and the latter is 996 extended here in Section 5.4. For the ecdsa case, the signature 997 field in the CertificateVerify message contains an ECDSA signature 998 computed over handshake messages exchanged so far, exactly similar to 999 CertificateVerify with other signing algorithms: 1001 CertificateVerify.signature.sha_hash 1002 SHA(handshake_messages); 1004 ECDSA signatures are computed as described in Section 5.10, and SHA 1005 in the above template for sha_hash accordingly may denote a hash 1006 algorithm other than SHA-1. As per ANSI X9.62, an ECDSA signature 1007 consists of a pair of integers, r and s. The digitally-signed 1008 element is encoded as an opaque vector <0..2^16-1>, the contents of 1009 which are the DER encoding [CCITT.X690] corresponding to the 1010 following ASN.1 notation [CCITT.X680]. 1012 Ecdsa-Sig-Value ::= SEQUENCE { 1013 r INTEGER, 1014 s INTEGER 1015 } 1017 Actions of the sender: 1019 The client computes its signature over all handshake messages sent or 1020 received starting at client hello and up to but not including this 1021 message. It uses the private key corresponding to its certified 1022 public key to compute the signature, which is conveyed in the format 1023 defined above. 1025 Actions of the receiver: 1027 The server extracts the client's signature from the CertificateVerify 1028 message, and verifies the signature using the public key it received 1029 in the client's Certificate message. 1031 5.9. Elliptic Curve Certificates 1033 X.509 certificates containing ECC public keys or signed using ECDSA 1034 MUST comply with [RFC3279] or another RFC that replaces or extends 1035 it. Clients SHOULD use the elliptic curve domain parameters 1036 recommended in ANSI X9.62, FIPS 186-4, and SEC 2 [SECG-SEC2]. 1038 5.10. ECDH, ECDSA, and RSA Computations 1040 All ECDH calculations (including parameter and key generation as well 1041 as the shared secret calculation) are performed according to 1042 [IEEE.P1363.1998] using the ECKAS-DH1 scheme with the identity map as 1043 key derivation function (KDF), so that the premaster secret is the 1044 x-coordinate of the ECDH shared secret elliptic curve point 1045 represented as an octet string. Note that this octet string (Z in 1046 IEEE 1363 terminology) as output by FE2OSP, the Field Element to 1047 Octet String Conversion Primitive, has constant length for any given 1048 field; leading zeros found in this octet string MUST NOT be 1049 truncated. 1051 (Note that this use of the identity KDF is a technicality. The 1052 complete picture is that ECDH is employed with a non-trivial KDF 1053 because TLS does not directly use the premaster secret for anything 1054 other than for computing the master secret. In TLS 1.0 and 1.1, this 1055 means that the MD5- and SHA-1-based TLS PRF serves as a KDF; in TLS 1056 1.2 the KDF is determined by ciphersuite; it is conceivable that 1057 future TLS versions or new TLS extensions introduced in the future 1058 may vary this computation.) 1060 All ECDSA computations MUST be performed according to ANSI X9.62 or 1061 its successors. Data to be signed/verified is hashed, and the result 1062 run directly through the ECDSA algorithm with no additional hashing. 1063 The default hash function is SHA-1 [FIPS.180-2], and sha_size (see 1064 Section 5.4 and Section 5.8) is 20. However, an alternative hash 1065 function, such as one of the new SHA hash functions specified in FIPS 1066 180-2 [FIPS.180-2], may be used instead if the certificate containing 1067 the EC public key explicitly requires use of another hash function. 1068 (The mechanism for specifying the required hash function has not been 1069 standardized, but this provision anticipates such standardization and 1070 obviates the need to update this document in response. Future PKIX 1071 RFCs may choose, for example, to specify the hash function to be used 1072 with a public key in the parameters field of subjectPublicKeyInfo.) 1073 All RSA signatures must be generated and verified according to 1074 [PKCS1] block type 1. 1076 6. Cipher Suites 1078 The table below defines new ECC cipher suites that use the key 1079 exchange algorithms specified in Section 2. 1081 +---------------------------------------+----------------+ 1082 | CipherSuite | Identifier | 1083 +---------------------------------------+----------------+ 1084 | TLS_ECDHE_ECDSA_WITH_NULL_SHA | { 0xC0, 0x06 } | 1085 | TLS_ECDHE_ECDSA_WITH_RC4_128_SHA | { 0xC0, 0x07 } | 1086 | TLS_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA | { 0xC0, 0x08 } | 1087 | TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA | { 0xC0, 0x09 } | 1088 | TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA | { 0xC0, 0x0A } | 1089 | | | 1090 | TLS_ECDHE_RSA_WITH_NULL_SHA | { 0xC0, 0x10 } | 1091 | TLS_ECDHE_RSA_WITH_RC4_128_SHA | { 0xC0, 0x11 } | 1092 | TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA | { 0xC0, 0x12 } | 1093 | TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA | { 0xC0, 0x13 } | 1094 | TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA | { 0xC0, 0x14 } | 1095 | | | 1096 | TLS_ECDH_anon_WITH_NULL_SHA | { 0xC0, 0x15 } | 1097 | TLS_ECDH_anon_WITH_RC4_128_SHA | { 0xC0, 0x16 } | 1098 | TLS_ECDH_anon_WITH_3DES_EDE_CBC_SHA | { 0xC0, 0x17 } | 1099 | TLS_ECDH_anon_WITH_AES_128_CBC_SHA | { 0xC0, 0x18 } | 1100 | TLS_ECDH_anon_WITH_AES_256_CBC_SHA | { 0xC0, 0x19 } | 1101 +---------------------------------------+----------------+ 1103 Table 5: TLS ECC cipher suites 1105 The key exchange method, cipher, and hash algorithm for each of these 1106 cipher suites are easily determined by examining the name. Ciphers 1107 (other than AES ciphers) and hash algorithms are defined in [RFC2246] 1108 and [RFC4346]. AES ciphers are defined in [RFC5246]. 1110 Server implementations SHOULD support all of the following cipher 1111 suites, and client implementations SHOULD support at least one of 1112 them: 1114 o TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 1115 o TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA 1116 o TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 1117 o TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256 1119 7. Security Considerations 1121 Security issues are discussed throughout this memo. 1123 For TLS handshakes using ECC cipher suites, the security 1124 considerations in appendices D of all three TLS base documemts apply 1125 accordingly. 1127 Security discussions specific to ECC can be found in 1128 [IEEE.P1363.1998] and [ANSI.X9-62.2005]. One important issue that 1129 implementers and users must consider is elliptic curve selection. 1130 Guidance on selecting an appropriate elliptic curve size is given in 1131 Table 1. 1133 Beyond elliptic curve size, the main issue is elliptic curve 1134 structure. As a general principle, it is more conservative to use 1135 elliptic curves with as little algebraic structure as possible. 1136 Thus, random curves are more conservative than special curves such as 1137 Koblitz curves, and curves over F_p with p random are more 1138 conservative than curves over F_p with p of a special form (and 1139 curves over F_p with p random might be considered more conservative 1140 than curves over F_2^m as there is no choice between multiple fields 1141 of similar size for characteristic 2). Note, however, that algebraic 1142 structure can also lead to implementation efficiencies, and 1143 implementers and users may, therefore, need to balance conservatism 1144 against a need for efficiency. Concrete attacks are known against 1145 only very few special classes of curves, such as supersingular 1146 curves, and these classes are excluded from the ECC standards that 1147 this document references [IEEE.P1363.1998], [ANSI.X9-62.2005]. 1149 Another issue is the potential for catastrophic failures when a 1150 single elliptic curve is widely used. In this case, an attack on the 1151 elliptic curve might result in the compromise of a large number of 1152 keys. Again, this concern may need to be balanced against efficiency 1153 and interoperability improvements associated with widely-used curves. 1154 Substantial additional information on elliptic curve choice can be 1155 found in [IEEE.P1363.1998], [ANSI.X9-62.2005], and [FIPS.186-4]. 1157 All of the key exchange algorithms defined in this document provide 1158 forward secrecy. Some of the deprecated key exchange algorithms do 1159 not. 1161 8. IANA Considerations 1163 [RFC4492], the predecessor of this document has already defined the 1164 IANA registries for the following: 1166 o NamedCurve Section 5.1 1167 o ECPointFormat Section 5.1 1168 o ECCurveType Section 5.4 1170 For each name space, this document defines the initial value 1171 assignments and defines a range of 256 values (NamedCurve) or eight 1172 values (ECPointFormat and ECCurveType) reserved for Private Use. Any 1173 additional assignments require IETF Consensus action. 1175 9. Acknowledgements 1177 Most of the text is this document is taken from [RFC4492], the 1178 predecessor of this document. The authors of that document were: 1180 o Simon Blake-Wilson 1181 o Nelson Bolyard 1182 o Vipul Gupta 1183 o Chris Hawk 1184 o Bodo Moeller 1186 In the predecessor document, the authors acknowledged the 1187 contributions of Bill Anderson and Tim Dierks. 1189 10. Version History for This Draft 1191 NOTE TO RFC EDITOR: PLEASE REMOVE THIS SECTION 1193 Changes from draft-nir-tls-rfc4492bis-00 and draft-ietf-tls- 1194 rfc4492bis-00 to draft-nir-tls-rfc4492bis-01: 1196 o Merged errata 1197 o Removed ECDH_RSA and ECDH_ECDSA 1199 Changes from RFC 4492 to draft-nir-tls-rfc4492bis-00: 1201 o Added TLS 1.2 to references. 1202 o Moved RFC 4492 authors to acknowledgements. 1203 o Removed list of required reading for ECC. 1205 11. References 1207 11.1. Normative References 1209 [ANSI.X9-62.2005] 1210 American National Standards Institute, "Public Key 1211 Cryptography for the Financial Services Industry, The 1212 Elliptic Curve Digital Signature Algorithm (ECDSA)", ANSI 1213 X9.62, 2005. 1215 [CCITT.X680] 1216 International Telephone and Telegraph Consultative 1217 Committee, "Abstract Syntax Notation One (ASN.1): 1218 Specification of basic notation", CCITT Recommendation 1219 X.680, July 2002. 1221 [CCITT.X690] 1222 International Telephone and Telegraph Consultative 1223 Committee, "ASN.1 encoding rules: Specification of basic 1224 encoding Rules (BER), Canonical encoding rules (CER) and 1225 Distinguished encoding rules (DER)", CCITT Recommendation 1226 X.690, July 2002. 1228 [FIPS.186-4] 1229 National Institute of Standards and Technology, "Digital 1230 Signature Standard", FIPS PUB 186-4, 2013, 1231 . 1234 [PKCS1] RSA Laboratories, "RSA Encryption Standard, Version 1.5", 1235 PKCS 1, November 1993. 1237 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1238 Requirement Levels", BCP 14, RFC 2119, March 1997. 1240 [RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", 1241 RFC 2246, January 1999. 1243 [RFC3279] Bassham, L., Polk, W., and R. Housley, "Algorithms and 1244 Identifiers for the Internet X.509 Public Key 1245 Infrastructure Certificate and Certificate Revocation List 1246 (CRL) Profile", RFC 3279, April 2002. 1248 [RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security 1249 (TLS) Protocol Version 1.1", RFC 4346, April 2006. 1251 [RFC4366] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., 1252 and T. Wright, "Transport Layer Security (TLS) 1253 Extensions", RFC 4366, April 2006. 1255 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 1256 (TLS) Protocol Version 1.2", RFC 5246, August 2008. 1258 [SECG-SEC2] 1259 CECG, "Recommended Elliptic Curve Domain Parameters", SEC 1260 2, 2000. 1262 11.2. Informative References 1264 [FIPS.180-2] 1265 National Institute of Standards and Technology, "Secure 1266 Hash Standard", FIPS PUB 180-2, August 2002, 1267 . 1270 [I-D.ietf-tls-tls13] 1271 Dierks, T. and E. Rescorla, "The Transport Layer Security 1272 (TLS) Protocol Version 1.3", draft-ietf-tls-tls13-02 (work 1273 in progress), July 2014. 1275 [IEEE.P1363.1998] 1276 Institute of Electrical and Electronics Engineers, 1277 "Standard Specifications for Public Key Cryptography", 1278 IEEE Draft P1363, 1998. 1280 [Lenstra_Verheul] 1281 Lenstra, A. and E. Verheul, "Selecting Cryptographic Key 1282 Sizes", Journal of Cryptology 14 (2001) 255-293, 2001. 1284 [RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B. 1285 Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites 1286 for Transport Layer Security (TLS)", RFC 4492, May 2006. 1288 Appendix A. Equivalent Curves (Informative) 1290 All of the NIST curves [FIPS.186-4] and several of the ANSI curves 1291 [ANSI.X9-62.2005] are equivalent to curves listed in Section 5.1.1. 1292 In the following table, multiple names in one row represent aliases 1293 for the same curve. 1295 Curve names chosen by different standards organizations 1297 +-----------+------------+------------+ 1298 | SECG | ANSI X9.62 | NIST | 1299 +-----------+------------+------------+ 1300 | sect163k1 | | NIST K-163 | 1301 | sect163r1 | | | 1302 | sect163r2 | | NIST B-163 | 1303 | sect193r1 | | | 1304 | sect193r2 | | | 1305 | sect233k1 | | NIST K-233 | 1306 | sect233r1 | | NIST B-233 | 1307 | sect239k1 | | | 1308 | sect283k1 | | NIST K-283 | 1309 | sect283r1 | | NIST B-283 | 1310 | sect409k1 | | NIST K-409 | 1311 | sect409r1 | | NIST B-409 | 1312 | sect571k1 | | NIST K-571 | 1313 | sect571r1 | | NIST B-571 | 1314 | secp160k1 | | | 1315 | secp160r1 | | | 1316 | secp160r2 | | | 1317 | secp192k1 | | | 1318 | secp192r1 | prime192v1 | NIST P-192 | 1319 | secp224k1 | | | 1320 | secp224r1 | | NIST P-224 | 1321 | secp256k1 | | | 1322 | secp256r1 | prime256v1 | NIST P-256 | 1323 | secp384r1 | | NIST P-384 | 1324 | secp521r1 | | NIST P-521 | 1325 +-----------+------------+------------+ 1327 Table 6: Equivalent curves defined by SECG, ANSI, and NIST 1329 Appendix B. Differences from RFC 4492 1331 o Added TLS 1.2 1332 o Merged Errata 1333 o Removed the ECDH key exchange algorithms: ECDH_RSA and ECDH_ECDSA 1334 o Deprecated a bunch of ciphersuites: 1336 TLS_ECDH_ECDSA_WITH_NULL_SHA 1337 TLS_ECDH_ECDSA_WITH_RC4_128_SHA 1338 TLS_ECDH_ECDSA_WITH_3DES_EDE_CBC_SHA 1339 TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA 1340 TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA 1341 TLS_ECDH_RSA_WITH_NULL_SHA 1342 TLS_ECDH_RSA_WITH_RC4_128_SHA 1343 TLS_ECDH_RSA_WITH_3DES_EDE_CBC_SHA 1344 TLS_ECDH_RSA_WITH_AES_128_CBC_SHA 1345 TLS_ECDH_RSA_WITH_AES_256_CBC_SHA 1347 Author's Address 1349 Yoav Nir 1350 Check Point Software Technologies Ltd. 1351 5 Hasolelim st. 1352 Tel Aviv 6789735 1353 Israel 1355 Email: ynir.ietf@gmail.com