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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == Line 684 has weird spacing: '...rveType cur...' == Line 702 has weird spacing: '...ameters cur...' == Line 720 has weird spacing: '...HParams par...' -- The document date (October 19, 2015) is 3113 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'ChangeCipherSpec' is mentioned on line 210, but not defined ** Downref: Normative reference to an Informational draft: draft-irtf-cfrg-curves (ref. 'CFRG-Curves') -- Possible downref: Non-RFC (?) normative reference: ref. '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 'SECG-SEC2' == Outdated reference: A later version (-28) exists of draft-ietf-tls-tls13-02 -- Obsolete informational reference (is this intentional?): RFC 4492 (Obsoleted by RFC 8422)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: 5 errors (**), 0 flaws (~~), 6 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 S. Josefsson 5 Expires: April 21, 2016 SJD AB 6 M. Pegourie-Gonnard 7 Independent / PolarSSL 8 October 19, 2015 10 Elliptic Curve Cryptography (ECC) Cipher Suites for Transport Layer 11 Security (TLS) Versions 1.2 and Earlier 12 draft-ietf-tls-rfc4492bis-04 14 Abstract 16 This document describes key exchange algorithms based on Elliptic 17 Curve Cryptography (ECC) for the Transport Layer Security (TLS) 18 protocol. In particular, it specifies the use of Ephemeral Elliptic 19 Curve Diffie-Hellman (ECDHE) key agreement in a TLS handshake and the 20 use of Elliptic Curve Digital Signature Algorithm (ECDSA) as a new 21 authentication mechanism. 23 Status of This Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at http://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on April 21, 2016. 40 Copyright Notice 42 Copyright (c) 2015 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (http://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 58 1.1. Conventions Used in This Document . . . . . . . . . . . . 4 59 2. Key Exchange Algorithm . . . . . . . . . . . . . . . . . . . 4 60 2.1. ECDHE_ECDSA . . . . . . . . . . . . . . . . . . . . . . . 5 61 2.2. ECDHE_RSA . . . . . . . . . . . . . . . . . . . . . . . . 6 62 2.3. ECDH_anon . . . . . . . . . . . . . . . . . . . . . . . . 6 63 3. Client Authentication . . . . . . . . . . . . . . . . . . . . 7 64 3.1. ECDSA_sign . . . . . . . . . . . . . . . . . . . . . . . 7 65 4. TLS Extensions for ECC . . . . . . . . . . . . . . . . . . . 8 66 5. Data Structures and Computations . . . . . . . . . . . . . . 8 67 5.1. Client Hello Extensions . . . . . . . . . . . . . . . . . 9 68 5.1.1. Supported Elliptic Curves Extension . . . . . . . . . 10 69 5.1.2. Supported Point Formats Extension . . . . . . . . . . 11 70 5.2. Server Hello Extension . . . . . . . . . . . . . . . . . 12 71 5.3. Server Certificate . . . . . . . . . . . . . . . . . . . 13 72 5.4. Server Key Exchange . . . . . . . . . . . . . . . . . . . 14 73 5.5. Certificate Request . . . . . . . . . . . . . . . . . . . 17 74 5.6. Client Certificate . . . . . . . . . . . . . . . . . . . 18 75 5.7. Client Key Exchange . . . . . . . . . . . . . . . . . . . 19 76 5.8. Certificate Verify . . . . . . . . . . . . . . . . . . . 20 77 5.9. Elliptic Curve Certificates . . . . . . . . . . . . . . . 21 78 5.10. ECDH, ECDSA, and RSA Computations . . . . . . . . . . . . 21 79 5.11. Public Key Validation . . . . . . . . . . . . . . . . . . 22 80 6. Cipher Suites . . . . . . . . . . . . . . . . . . . . . . . . 23 81 7. Security Considerations . . . . . . . . . . . . . . . . . . . 24 82 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 83 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26 84 10. Version History for This Draft . . . . . . . . . . . . . . . 26 85 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 27 86 11.1. Normative References . . . . . . . . . . . . . . . . . . 27 87 11.2. Informative References . . . . . . . . . . . . . . . . . 28 88 Appendix A. Equivalent Curves (Informative) . . . . . . . . . . 28 89 Appendix B. Differences from RFC 4492 . . . . . . . . . . . . . 29 90 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30 92 1. Introduction 94 Elliptic Curve Cryptography (ECC) has emerged as an attractive 95 public-key cryptosystem, in particular for mobile (i.e., wireless) 96 environments. Compared to currently prevalent cryptosystems such as 97 RSA, ECC offers equivalent security with smaller key sizes. This is 98 illustrated in the following table, based on [Lenstra_Verheul], which 99 gives approximate comparable key sizes for symmetric- and asymmetric- 100 key cryptosystems based on the best-known algorithms for attacking 101 them. 103 +-----------+-------+------------+ 104 | Symmetric | ECC | DH/DSA/RSA | 105 +-----------+-------+------------+ 106 | 80 | >=158 | 1024 | 107 | 112 | >=221 | 2048 | 108 | 128 | >=252 | 3072 | 109 | 192 | >=379 | 7680 | 110 | 256 | >=506 | 15360 | 111 +-----------+-------+------------+ 113 Table 1: Comparable Key Sizes (in bits) 115 Smaller key sizes result in savings for power, memory, bandwidth, and 116 computational cost that make ECC especially attractive for 117 constrained environments. 119 This document describes additions to TLS to support ECC, applicable 120 to TLS versions 1.0 [RFC2246], 1.1 [RFC4346], and 1.2 [RFC5246]. The 121 use of ECC in TLS 1.3 is defined in [I-D.ietf-tls-tls13], and is 122 explicitly out of scope for this document. In particular, this 123 document defines: 125 o the use of the Elliptic Curve Diffie-Hellman key agreement scheme 126 with ephemeral keys to establish the TLS premaster secret, and 127 o the use of ECDSA certificates for authentication of TLS peers. 129 The remainder of this document is organized as follows. Section 2 130 provides an overview of ECC-based key exchange algorithms for TLS. 131 Section 3 describes the use of ECC certificates for client 132 authentication. TLS extensions that allow a client to negotiate the 133 use of specific curves and point formats are presented in Section 4. 134 Section 5 specifies various data structures needed for an ECC-based 135 handshake, their encoding in TLS messages, and the processing of 136 those messages. Section 6 defines ECC-based cipher suites and 137 identifies a small subset of these as recommended for all 138 implementations of this specification. Section 7 discusses security 139 considerations. Section 8 describes IANA considerations for the name 140 spaces created by this document's predecessor. Section 9 gives 141 acknowledgements. Appendix B provides differences from [RFC4492], 142 the document that this one replaces. 144 Implementation of this specification requires familiarity with TLS, 145 TLS extensions [RFC4366], and ECC (TBD: reference Wikipedia here?). 147 1.1. Conventions Used in This Document 149 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 150 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 151 document are to be interpreted as described in [RFC2119]. 153 2. Key Exchange Algorithm 155 This document defines three new ECC-based key exchange algorithms for 156 TLS. All of them use Ephemeral ECDH (ECDHE) to compute the TLS 157 premaster secret, and they differ only in the mechanism (if any) used 158 to authenticate them. The derivation of the TLS master secret from 159 the premaster secret and the subsequent generation of bulk 160 encryption/MAC keys and initialization vectors is independent of the 161 key exchange algorithm and not impacted by the introduction of ECC. 163 Table 2 summarizes the new key exchange algorithms. All of these key 164 exchange algorithms provide forward secrecy. 166 +-------------+------------------------------------------+ 167 | Algorithm | Description | 168 +-------------+------------------------------------------+ 169 | ECDHE_ECDSA | Ephemeral ECDH with ECDSA signatures. | 170 | ECDHE_RSA | Ephemeral ECDH with RSA signatures. | 171 | ECDH_anon | Anonymous ephemeral ECDH, no signatures. | 172 +-------------+------------------------------------------+ 174 Table 2: ECC Key Exchange Algorithms 176 These key exchanges are analogous to DHE_DSS, DHE_RSA, and DH_anon, 177 respectively. 179 With ECDHE_RSA, a server can reuse its existing RSA certificate and 180 easily comply with a constrained client's elliptic curve preferences 181 (see Section 4). However, the computational cost incurred by a 182 server is higher for ECDHE_RSA than for the traditional RSA key 183 exchange, which does not provide forward secrecy. 185 The anonymous key exchange algorithm does not provide authentication 186 of the server or the client. Like other anonymous TLS key exchanges, 187 it is subject to man-in-the-middle attacks. Implementations of this 188 algorithm SHOULD provide authentication by other means. 190 Note that there is no structural difference between ECDH and ECDSA 191 keys. A certificate issuer may use X.509 v3 keyUsage and 192 extendedKeyUsage extensions to restrict the use of an ECC public key 193 to certain computations. This document refers to an ECC key as ECDH- 194 capable if its use in ECDH is permitted. ECDSA-capable is defined 195 similarly. 197 Client Server 198 ------ ------ 199 ClientHello --------> 200 ServerHello 201 Certificate* 202 ServerKeyExchange* 203 CertificateRequest*+ 204 <-------- ServerHelloDone 205 Certificate*+ 206 ClientKeyExchange 207 CertificateVerify*+ 208 [ChangeCipherSpec] 209 Finished --------> 210 [ChangeCipherSpec] 211 <-------- Finished 212 Application Data <-------> Application Data 213 * message is not sent under some conditions 214 + message is not sent unless client authentication 215 is desired 217 Figure 1: Message flow in a full TLS handshake 219 Figure 1 shows all messages involved in the TLS key establishment 220 protocol (aka full handshake). The addition of ECC has direct impact 221 only on the ClientHello, the ServerHello, the server's Certificate 222 message, the ServerKeyExchange, the ClientKeyExchange, the 223 CertificateRequest, the client's Certificate message, and the 224 CertificateVerify. Next, we describe the ECC key exchange algorithm 225 in greater detail in terms of the content and processing of these 226 messages. For ease of exposition, we defer discussion of client 227 authentication and associated messages (identified with a + in 228 Figure 1) until Section 3 and of the optional ECC-specific extensions 229 (which impact the Hello messages) until Section 4. 231 2.1. ECDHE_ECDSA 233 In ECDHE_ECDSA, the server's certificate MUST contain an ECDSA- 234 capable public key and be signed with ECDSA. 236 The server sends its ephemeral ECDH public key and a specification of 237 the corresponding curve in the ServerKeyExchange message. These 238 parameters MUST be signed with ECDSA using the private key 239 corresponding to the public key in the server's Certificate. 241 The client generates an ECDH key pair on the same curve as the 242 server's ephemeral ECDH key and sends its public key in the 243 ClientKeyExchange message. 245 Both client and server perform an ECDH operation Section 5.10 and use 246 the resultant shared secret as the premaster secret. 248 2.2. ECDHE_RSA 250 This key exchange algorithm is the same as ECDHE_ECDSA except that 251 the server's certificate MUST contain an RSA public key authorized 252 for signing, and that the signature in the ServerKeyExchange message 253 must be computed with the corresponding RSA private key. The server 254 certificate MUST be signed with RSA. 256 2.3. ECDH_anon 258 NOTE: Despite the name beginning with "ECDH_" (no E), the key used in 259 ECDH_anon is ephemeral just like the key in ECDHE_RSA and 260 ECDHE_ECDSA. The naming follows the example of DH_anon, where the 261 key is also ephemeral but the name does not reflect it. TBD: Do we 262 want to rename this so that it makes sense? 264 In ECDH_anon, the server's Certificate, the CertificateRequest, the 265 client's Certificate, and the CertificateVerify messages MUST NOT be 266 sent. 268 The server MUST send an ephemeral ECDH public key and a specification 269 of the corresponding curve in the ServerKeyExchange message. These 270 parameters MUST NOT be signed. 272 The client generates an ECDH key pair on the same curve as the 273 server's ephemeral ECDH key and sends its public key in the 274 ClientKeyExchange message. 276 Both client and server perform an ECDH operation and use the 277 resultant shared secret as the premaster secret. All ECDH 278 calculations are performed as specified in Section 5.10. 280 Note that while the ECDHE_ECDSA and ECDHE_RSA key exchange algorithms 281 require the server's certificate to be signed with a particular 282 signature scheme, this specification (following the similar cases of 283 DHE_DSS, and DHE_RSA in the TLS base documents) does not impose 284 restrictions on signature schemes used elsewhere in the certificate 285 chain. (Often such restrictions will be useful, and it is expected 286 that this will be taken into account in certification authorities' 287 signing practices. However, such restrictions are not strictly 288 required in general: Even if it is beyond the capabilities of a 289 client to completely validate a given chain, the client may be able 290 to validate the server's certificate by relying on a trusted 291 certification authority whose certificate appears as one of the 292 intermediate certificates in the chain.) 294 3. Client Authentication 296 This document defines a client authentication mechanism, named after 297 the type of client certificate involved: ECDSA_sign. The ECDSA_sign 298 mechanism is usable with any of the non-anonymous ECC key exchange 299 algorithms described in Section 2 as well as other non-anonymous 300 (non-ECC) key exchange algorithms defined in TLS. 302 The server can request ECC-based client authentication by including 303 this certificate type in its CertificateRequest message. The client 304 must check if it possesses a certificate appropriate for the method 305 suggested by the server and is willing to use it for authentication. 307 If these conditions are not met, the client should send a client 308 Certificate message containing no certificates. In this case, the 309 ClientKeyExchange should be sent as described in Section 2, and the 310 CertificateVerify should not be sent. If the server requires client 311 authentication, it may respond with a fatal handshake failure alert. 313 If the client has an appropriate certificate and is willing to use it 314 for authentication, it must send that certificate in the client's 315 Certificate message (as per Section 5.6) and prove possession of the 316 private key corresponding to the certified key. The process of 317 determining an appropriate certificate and proving possession is 318 different for each authentication mechanism and described below. 320 NOTE: It is permissible for a server to request (and the client to 321 send) a client certificate of a different type than the server 322 certificate. 324 3.1. ECDSA_sign 326 To use this authentication mechanism, the client MUST possess a 327 certificate containing an ECDSA-capable public key and signed with 328 ECDSA. 330 The client proves possession of the private key corresponding to the 331 certified key by including a signature in the CertificateVerify 332 message as described in Section 5.8. 334 4. TLS Extensions for ECC 336 Two new TLS extensions are defined in this specification: (i) the 337 Supported Elliptic Curves Extension, and (ii) the Supported Point 338 Formats Extension. These allow negotiating the use of specific 339 curves and point formats (e.g., compressed vs. uncompressed, 340 respectively) during a handshake starting a new session. These 341 extensions are especially relevant for constrained clients that may 342 only support a limited number of curves or point formats. They 343 follow the general approach outlined in [RFC4366]; message details 344 are specified in Section 5. The client enumerates the curves it 345 supports and the point formats it can parse by including the 346 appropriate extensions in its ClientHello message. The server 347 similarly enumerates the point formats it can parse by including an 348 extension in its ServerHello message. 350 A TLS client that proposes ECC cipher suites in its ClientHello 351 message SHOULD include these extensions. Servers implementing ECC 352 cipher suites MUST support these extensions, and when a client uses 353 these extensions, servers MUST NOT negotiate the use of an ECC cipher 354 suite unless they can complete the handshake while respecting the 355 choice of curves and compression techniques specified by the client. 356 This eliminates the possibility that a negotiated ECC handshake will 357 be subsequently aborted due to a client's inability to deal with the 358 server's EC key. 360 The client MUST NOT include these extensions in the ClientHello 361 message if it does not propose any ECC cipher suites. A client that 362 proposes ECC cipher suites may choose not to include these 363 extensions. In this case, the server is free to choose any one of 364 the elliptic curves or point formats listed in Section 5. That 365 section also describes the structure and processing of these 366 extensions in greater detail. 368 In the case of session resumption, the server simply ignores the 369 Supported Elliptic Curves Extension and the Supported Point Formats 370 Extension appearing in the current ClientHello message. These 371 extensions only play a role during handshakes negotiating a new 372 session. 374 5. Data Structures and Computations 376 This section specifies the data structures and computations used by 377 ECC-based key mechanisms specified in the previous three sections. 378 The presentation language used here is the same as that used in TLS. 379 Since this specification extends TLS, these descriptions should be 380 merged with those in the TLS specification and any others that extend 381 TLS. This means that enum types may not specify all possible values, 382 and structures with multiple formats chosen with a select() clause 383 may not indicate all possible cases. 385 5.1. Client Hello Extensions 387 This section specifies two TLS extensions that can be included with 388 the ClientHello message as described in [RFC4366], the Supported 389 Elliptic Curves Extension and the Supported Point Formats Extension. 391 When these extensions are sent: 393 The extensions SHOULD be sent along with any ClientHello message that 394 proposes ECC cipher suites. 396 Meaning of these extensions: 398 These extensions allow a client to enumerate the elliptic curves it 399 supports and/or the point formats it can parse. 401 Structure of these extensions: 403 The general structure of TLS extensions is described in [RFC4366], 404 and this specification adds two new types to ExtensionType. 406 enum { elliptic_curves(10), ec_point_formats(11) } ExtensionType; 408 elliptic_curves (Supported Elliptic Curves Extension): Indicates the 409 set of elliptic curves supported by the client. For this 410 extension, the opaque extension_data field contains 411 EllipticCurveList. See Section 5.1.1 for details. 412 ec_point_formats (Supported Point Formats Extension): Indicates the 413 set of point formats that the client can parse. For this 414 extension, the opaque extension_data field contains 415 ECPointFormatList. See Section 5.1.2 for details. 417 Actions of the sender: 419 A client that proposes ECC cipher suites in its ClientHello message 420 appends these extensions (along with any others), enumerating the 421 curves it supports and the point formats it can parse. Clients 422 SHOULD send both the Supported Elliptic Curves Extension and the 423 Supported Point Formats Extension. If the Supported Point Formats 424 Extension is indeed sent, it MUST contain the value 0 (uncompressed) 425 as one of the items in the list of point formats. 427 Actions of the receiver: 429 A server that receives a ClientHello containing one or both of these 430 extensions MUST use the client's enumerated capabilities to guide its 431 selection of an appropriate cipher suite. One of the proposed ECC 432 cipher suites must be negotiated only if the server can successfully 433 complete the handshake while using the curves and point formats 434 supported by the client (cf. Section 5.3 and Section 5.4). 436 NOTE: A server participating in an ECDHE-ECDSA key exchange may use 437 different curves for the ECDSA key in its certificate, and for the 438 ephemeral ECDH key in the ServerKeyExchange message. The server MUST 439 consider the extensions in both cases. 441 If a server does not understand the Supported Elliptic Curves 442 Extension, does not understand the Supported Point Formats Extension, 443 or is unable to complete the ECC handshake while restricting itself 444 to the enumerated curves and point formats, it MUST NOT negotiate the 445 use of an ECC cipher suite. Depending on what other cipher suites 446 are proposed by the client and supported by the server, this may 447 result in a fatal handshake failure alert due to the lack of common 448 cipher suites. 450 5.1.1. Supported Elliptic Curves Extension 452 RFC 4492 defined 25 different curves in the NamedCurve registry for 453 use in TLS. Only three have seen any use. This specification is 454 deprecating the rest (with numbers 1-22). This specification also 455 deprecates the explicit curves with identifiers 0xFF01 and 0xFF02. 456 It also adds the new curves defined in [CFRG-Curves]. The end result 457 is as follows: 459 enum { 460 deprecated(1..22), 461 secp256r1 (23), secp384r1 (24), secp521r1 (25), 462 Curve25519(TBD1), 463 Curve448(TBD2), 464 reserved (0xFE00..0xFEFF), 465 deprecated(0xFF01..0xFF02), 466 (0xFFFF) 467 } NamedCurve; 469 Note that other specification have since added other values to this 470 enumeration. 472 secp256r1, etc: Indicates support of the corresponding named curve or 473 class of explicitly defined curves. The named curves secp256r1, 474 secp384r1, and secp521r1 are specified in SEC 2 [SECG-SEC2]. These 475 curves are also recommended in ANSI X9.62 [ANSI.X9-62.2005] and FIPS 476 186-4 [FIPS.186-4]. Curve25519 and Curve448 are defined in 478 [CFRG-Curves]. Values 0xFE00 through 0xFEFF are reserved for private 479 use. 481 The NamedCurve name space is maintained by IANA. See Section 8 for 482 information on how new value assignments are added. 484 struct { 485 NamedCurve elliptic_curve_list<1..2^16-1> 486 } EllipticCurveList; 488 Items in elliptic_curve_list are ordered according to the client's 489 preferences (favorite choice first). 491 As an example, a client that only supports secp256r1 (aka NIST P-256; 492 value 23 = 0x0017) and secp384r1 (aka NIST P-384; value 24 = 0x0018) 493 and prefers to use secp256r1 would include a TLS extension consisting 494 of the following octets. Note that the first two octets indicate the 495 extension type (Supported Elliptic Curves Extension): 497 00 0A 00 06 00 04 00 17 00 18 499 5.1.2. Supported Point Formats Extension 501 enum { uncompressed (0), ansiX962_compressed_prime (1), 502 ansiX962_compressed_char2 (2), reserved (248..255) 503 } ECPointFormat; 504 struct { 505 ECPointFormat ec_point_format_list<1..2^8-1> 506 } ECPointFormatList; 508 Three point formats were included in the definition of ECPointFormat 509 above. This specification deprecates all but the uncompressed point 510 format. Implementations of this document MUST support the 511 uncompressed format for all of their supported curves, and MUST 512 support no other formats for curves defined in this specification. 513 For backwards compatibility purposes, the point format list extension 514 MUST still be included, and contain exactly one value: the 515 uncomptessed point format (0). 517 The ECPointFormat name space is maintained by IANA. See Section 8 518 for information on how new value assignments are added. 520 Items in ec_point_format_list are ordered according to the client's 521 preferences (favorite choice first). 523 A client compliant with this specification that supports no other 524 curves MUST send the following octets; note that the first two octets 525 indicate the extension type (Supported Point Formats Extension): 527 00 0B 00 02 01 00 529 5.2. Server Hello Extension 531 This section specifies a TLS extension that can be included with the 532 ServerHello message as described in [RFC4366], the Supported Point 533 Formats Extension. 535 When this extension is sent: 537 The Supported Point Formats Extension is included in a ServerHello 538 message in response to a ClientHello message containing the Supported 539 Point Formats Extension when negotiating an ECC cipher suite. 541 Meaning of this extension: 543 This extension allows a server to enumerate the point formats it can 544 parse (for the curve that will appear in its ServerKeyExchange 545 message when using the ECDHE_ECDSA, ECDHE_RSA, or ECDH_anon key 546 exchange algorithm. 548 Structure of this extension: 550 The server's Supported Point Formats Extension has the same structure 551 as the client's Supported Point Formats Extension (see 552 Section 5.1.2). Items in ec_point_format_list here are ordered 553 according to the server's preference (favorite choice first). Note 554 that the server may include items that were not found in the client's 555 list (e.g., the server may prefer to receive points in compressed 556 format even when a client cannot parse this format: the same client 557 may nevertheless be capable of outputting points in compressed 558 format). 560 Actions of the sender: 562 A server that selects an ECC cipher suite in response to a 563 ClientHello message including a Supported Point Formats Extension 564 appends this extension (along with others) to its ServerHello 565 message, enumerating the point formats it can parse. The Supported 566 Point Formats Extension, when used, MUST contain the value 0 567 (uncompressed) as one of the items in the list of point formats. 569 Actions of the receiver: 571 A client that receives a ServerHello message containing a Supported 572 Point Formats Extension MUST respect the server's choice of point 573 formats during the handshake (cf. Section 5.6 and Section 5.7). If 574 no Supported Point Formats Extension is received with the 575 ServerHello, this is equivalent to an extension allowing only the 576 uncompressed point format. 578 5.3. Server Certificate 580 When this message is sent: 582 This message is sent in all non-anonymous ECC-based key exchange 583 algorithms. 585 Meaning of this message: 587 This message is used to authentically convey the server's static 588 public key to the client. The following table shows the server 589 certificate type appropriate for each key exchange algorithm. ECC 590 public keys MUST be encoded in certificates as described in 591 Section 5.9. 593 NOTE: The server's Certificate message is capable of carrying a chain 594 of certificates. The restrictions mentioned in Table 3 apply only to 595 the server's certificate (first in the chain). 597 +-------------+-----------------------------------------------------+ 598 | Algorithm | Server Certificate Type | 599 +-------------+-----------------------------------------------------+ 600 | ECDHE_ECDSA | Certificate MUST contain an ECDSA-capable public | 601 | | key. It MUST be signed with ECDSA. | 602 | ECDHE_RSA | Certificate MUST contain an RSA public key | 603 | | authorized for use in digital signatures. It MUST | 604 | | be signed with RSA. | 605 +-------------+-----------------------------------------------------+ 607 Table 3: Server Certificate Types 609 Structure of this message: 611 Identical to the TLS Certificate format. 613 Actions of the sender: 615 The server constructs an appropriate certificate chain and conveys it 616 to the client in the Certificate message. If the client has used a 617 Supported Elliptic Curves Extension, the public key in the server's 618 certificate MUST respect the client's choice of elliptic curves; in 619 particular, the public key MUST employ a named curve (not the same 620 curve as an explicit curve) unless the client has indicated support 621 for explicit curves of the appropriate type. If the client has used 622 a Supported Point Formats Extension, both the server's public key 623 point and (in the case of an explicit curve) the curve's base point 624 MUST respect the client's choice of point formats. (A server that 625 cannot satisfy these requirements MUST NOT choose an ECC cipher suite 626 in its ServerHello message.) 628 Actions of the receiver: 630 The client validates the certificate chain, extracts the server's 631 public key, and checks that the key type is appropriate for the 632 negotiated key exchange algorithm. (A possible reason for a fatal 633 handshake failure is that the client's capabilities for handling 634 elliptic curves and point formats are exceeded; cf. Section 5.1.) 636 5.4. Server Key Exchange 638 When this message is sent: 640 This message is sent when using the ECDHE_ECDSA, ECDHE_RSA, and 641 ECDH_anon key exchange algorithms. 643 Meaning of this message: 645 This message is used to convey the server's ephemeral ECDH public key 646 (and the corresponding elliptic curve domain parameters) to the 647 client. 649 The ECCCurveType enum used to have values for explicit prime and for 650 explicit char2 curves. Those values are now deprecated, so only one 651 value remains: 653 Structure of this message: 655 enum { deprecated (1..2), named_curve (3), reserved(248..255) 656 } ECCurveType; 658 The value named_curve indicates that a named curve is used. This 659 option SHOULD be used when applicable. 661 Values 248 through 255 are reserved for private use. 663 The ECCurveType name space is maintained by IANA. See Section 8 for 664 information on how new value assignments are added. 666 RFC 4492 had a specification for an ECCurve structure and an 667 ECBasisType structure. Both of these are omitted now because they 668 were only used with the now deprecated explicit curves. 670 struct { 671 opaque point <1..2^8-1>; 672 } ECPoint; 674 This is the byte string representation of an elliptic curve point 675 following the conversion routine in Section 4.3.6 of 676 [ANSI.X9-62.2005]. This byte string may represent an elliptic curve 677 point in uncompressed or compressed format; it MUST conform to what 678 the client has requested through a Supported Point Formats Extension 679 if this extension was used. For the Curve25519 and Curve448 curves, 680 the only valid representation is the one specified in [CFRG-Curves] - 681 a 32- or 56-octet representation of the u value of the point. 683 struct { 684 ECCurveType curve_type; 685 select (curve_type) { 686 case named_curve: 687 NamedCurve namedcurve; 688 }; 689 } ECParameters; 691 This identifies the type of the elliptic curve domain parameters. 693 Specifies a recommended set of elliptic curve domain parameters. All 694 those values of NamedCurve are allowed that refer to a specific 695 curve. Values of NamedCurve that indicate support for a class of 696 explicitly defined curves are not allowed here (they are only 697 permissible in the ClientHello extension); this applies to 698 arbitrary_explicit_prime_curves(0xFF01) and 699 arbitrary_explicit_char2_curves(0xFF02). 701 struct { 702 ECParameters curve_params; 703 ECPoint public; 704 } ServerECDHParams; 706 Specifies the elliptic curve domain parameters associated with the 707 ECDH public key. 709 The ephemeral ECDH public key. 711 The ServerKeyExchange message is extended as follows. 713 enum { ec_diffie_hellman } KeyExchangeAlgorithm; 715 ec_diffie_hellman: Indicates the ServerKeyExchange message contains 716 an ECDH public key. 718 select (KeyExchangeAlgorithm) { 719 case ec_diffie_hellman: 720 ServerECDHParams params; 721 Signature signed_params; 722 } ServerKeyExchange; 724 params: Specifies the ECDH public key and associated domain 725 parameters. 726 signed_params: A hash of the params, with the signature appropriate 727 to that hash applied. The private key corresponding to the 728 certified public key in the server's Certificate message is used 729 for signing. 731 enum { ecdsa } SignatureAlgorithm; 732 select (SignatureAlgorithm) { 733 case ecdsa: 734 digitally-signed struct { 735 opaque sha_hash[sha_size]; 736 }; 737 } Signature; 738 ServerKeyExchange.signed_params.sha_hash 739 SHA(ClientHello.random + ServerHello.random + 740 ServerKeyExchange.params); 742 NOTE: SignatureAlgorithm is "rsa" for the ECDHE_RSA key exchange 743 algorithm and "anonymous" for ECDH_anon. These cases are defined in 744 TLS. SignatureAlgorithm is "ecdsa" for ECDHE_ECDSA. ECDSA 745 signatures are generated and verified as described in Section 5.10, 746 and SHA in the above template for sha_hash accordingly may denote a 747 hash algorithm other than SHA-1. As per ANSI X9.62, an ECDSA 748 signature consists of a pair of integers, r and s. The digitally- 749 signed element is encoded as an opaque vector <0..2^16-1>, the 750 contents of which are the DER encoding corresponding to the following 751 ASN.1 notation. 753 Ecdsa-Sig-Value ::= SEQUENCE { 754 r INTEGER, 755 s INTEGER 756 } 758 Actions of the sender: 760 The server selects elliptic curve domain parameters and an ephemeral 761 ECDH public key corresponding to these parameters according to the 762 ECKAS-DH1 scheme from IEEE 1363 [IEEE.P1363.1998]. It conveys this 763 information to the client in the ServerKeyExchange message using the 764 format defined above. 766 Actions of the receiver: 768 The client verifies the signature (when present) and retrieves the 769 server's elliptic curve domain parameters and ephemeral ECDH public 770 key from the ServerKeyExchange message. (A possible reason for a 771 fatal handshake failure is that the client's capabilities for 772 handling elliptic curves and point formats are exceeded; cf. 773 Section 5.1.) 775 5.5. Certificate Request 777 When this message is sent: 779 This message is sent when requesting client authentication. 781 Meaning of this message: 783 The server uses this message to suggest acceptable client 784 authentication methods. 786 Structure of this message: 788 The TLS CertificateRequest message is extended as follows. 790 enum { 791 ecdsa_sign(64), rsa_fixed_ecdh(65), 792 ecdsa_fixed_ecdh(66), (255) 793 } ClientCertificateType; 795 ecdsa_sign, etc. Indicates that the server would like to use the 796 corresponding client authentication method specified in Section 3. 798 Actions of the sender: 800 The server decides which client authentication methods it would like 801 to use, and conveys this information to the client using the format 802 defined above. 804 Actions of the receiver: 806 The client determines whether it has a suitable certificate for use 807 with any of the requested methods and whether to proceed with client 808 authentication. 810 5.6. Client Certificate 812 When this message is sent: 814 This message is sent in response to a CertificateRequest when a 815 client has a suitable certificate and has decided to proceed with 816 client authentication. (Note that if the server has used a Supported 817 Point Formats Extension, a certificate can only be considered 818 suitable for use with the ECDSA_sign, RSA_fixed_ECDH, and 819 ECDSA_fixed_ECDH authentication methods if the public key point 820 specified in it respects the server's choice of point formats. If no 821 Supported Point Formats Extension has been used, a certificate can 822 only be considered suitable for use with these authentication methods 823 if the point is represented in uncompressed point format.) 825 Meaning of this message: 827 This message is used to authentically convey the client's static 828 public key to the server. The following table summarizes what client 829 certificate types are appropriate for the ECC-based client 830 authentication mechanisms described in Section 3. ECC public keys 831 must be encoded in certificates as described in Section 5.9. 833 NOTE: The client's Certificate message is capable of carrying a chain 834 of certificates. The restrictions mentioned in Table 4 apply only to 835 the client's certificate (first in the chain). 837 +------------------+------------------------------------------------+ 838 | Client | Client Certificate Type | 839 | Authentication | | 840 | Method | | 841 +------------------+------------------------------------------------+ 842 | ECDSA_sign | Certificate MUST contain an ECDSA-capable | 843 | | public key and be signed with ECDSA. | 844 | ECDSA_fixed_ECDH | Certificate MUST contain an ECDH-capable | 845 | | public key on the same elliptic curve as the | 846 | | server's long-term ECDH key. This certificate | 847 | | MUST be signed with ECDSA. | 848 | RSA_fixed_ECDH | Certificate MUST contain an ECDH-capable | 849 | | public key on the same elliptic curve as the | 850 | | server's long-term ECDH key. This certificate | 851 | | MUST be signed with RSA. | 852 +------------------+------------------------------------------------+ 854 Table 4: Client Certificate Types 856 Structure of this message: 858 Identical to the TLS client Certificate format. 860 Actions of the sender: 862 The client constructs an appropriate certificate chain, and conveys 863 it to the server in the Certificate message. 865 Actions of the receiver: 867 The TLS server validates the certificate chain, extracts the client's 868 public key, and checks that the key type is appropriate for the 869 client authentication method. 871 5.7. Client Key Exchange 873 When this message is sent: 875 This message is sent in all key exchange algorithms. If client 876 authentication with ECDSA_fixed_ECDH or RSA_fixed_ECDH is used, this 877 message is empty. Otherwise, it contains the client's ephemeral ECDH 878 public key. 880 Meaning of the message: 882 This message is used to convey ephemeral data relating to the key 883 exchange belonging to the client (such as its ephemeral ECDH public 884 key). 886 Structure of this message: 888 The TLS ClientKeyExchange message is extended as follows. 890 enum { implicit, explicit } PublicValueEncoding; 892 implicit, explicit: For ECC cipher suites, this indicates whether 893 the client's ECDH public key is in the client's certificate 894 ("implicit") or is provided, as an ephemeral ECDH public key, in 895 the ClientKeyExchange message ("explicit"). (This is "explicit" 896 in ECC cipher suites except when the client uses the 897 ECDSA_fixed_ECDH or RSA_fixed_ECDH client authentication 898 mechanism.) 900 struct { 901 select (PublicValueEncoding) { 902 case implicit: struct { }; 903 case explicit: ECPoint ecdh_Yc; 904 } ecdh_public; 905 } ClientECDiffieHellmanPublic; 907 ecdh_Yc: Contains the client's ephemeral ECDH public key as a byte 908 string ECPoint.point, which may represent an elliptic curve point 909 in uncompressed or compressed format. Here, the format MUST 910 conform to what the server has requested through a Supported Point 911 Formats Extension if this extension was used, and MUST be 912 uncompressed if this extension was not used. 914 struct { 915 select (KeyExchangeAlgorithm) { 916 case ec_diffie_hellman: ClientECDiffieHellmanPublic; 917 } exchange_keys; 918 } ClientKeyExchange; 920 Actions of the sender: 922 The client selects an ephemeral ECDH public key corresponding to the 923 parameters it received from the server according to the ECKAS-DH1 924 scheme from IEEE 1363. It conveys this information to the client in 925 the ClientKeyExchange message using the format defined above. 927 Actions of the receiver: 929 The server retrieves the client's ephemeral ECDH public key from the 930 ClientKeyExchange message and checks that it is on the same elliptic 931 curve as the server's ECDH key. 933 5.8. Certificate Verify 935 When this message is sent: 937 This message is sent when the client sends a client certificate 938 containing a public key usable for digital signatures, e.g., when the 939 client is authenticated using the ECDSA_sign mechanism. 941 Meaning of the message: 943 This message contains a signature that proves possession of the 944 private key corresponding to the public key in the client's 945 Certificate message. 947 Structure of this message: 949 The TLS CertificateVerify message and the underlying Signature type 950 are defined in the TLS base specifications, and the latter is 951 extended here in Section 5.4. For the ecdsa case, the signature 952 field in the CertificateVerify message contains an ECDSA signature 953 computed over handshake messages exchanged so far, exactly similar to 954 CertificateVerify with other signing algorithms: 956 CertificateVerify.signature.sha_hash 957 SHA(handshake_messages); 959 ECDSA signatures are computed as described in Section 5.10, and SHA 960 in the above template for sha_hash accordingly may denote a hash 961 algorithm other than SHA-1. As per ANSI X9.62, an ECDSA signature 962 consists of a pair of integers, r and s. The digitally-signed 963 element is encoded as an opaque vector <0..2^16-1>, the contents of 964 which are the DER encoding [CCITT.X690] corresponding to the 965 following ASN.1 notation [CCITT.X680]. 967 Ecdsa-Sig-Value ::= SEQUENCE { 968 r INTEGER, 969 s INTEGER 970 } 972 Actions of the sender: 974 The client computes its signature over all handshake messages sent or 975 received starting at client hello and up to but not including this 976 message. It uses the private key corresponding to its certified 977 public key to compute the signature, which is conveyed in the format 978 defined above. 980 Actions of the receiver: 982 The server extracts the client's signature from the CertificateVerify 983 message, and verifies the signature using the public key it received 984 in the client's Certificate message. 986 5.9. Elliptic Curve Certificates 988 X.509 certificates containing ECC public keys or signed using ECDSA 989 MUST comply with [RFC3279] or another RFC that replaces or extends 990 it. Clients SHOULD use the elliptic curve domain parameters 991 recommended in ANSI X9.62, FIPS 186-4, and SEC 2 [SECG-SEC2]. 993 5.10. ECDH, ECDSA, and RSA Computations 995 All ECDH calculations for the NIST curves (including parameter and 996 key generation as well as the shared secret calculation) are 997 performed according to [IEEE.P1363.1998] using the ECKAS-DH1 scheme 998 with the identity map as key derivation function (KDF), so that the 999 premaster secret is the x-coordinate of the ECDH shared secret 1000 elliptic curve point represented as an octet string. Note that this 1001 octet string (Z in IEEE 1363 terminology) as output by FE2OSP, the 1002 Field Element to Octet String Conversion Primitive, has constant 1003 length for any given field; leading zeros found in this octet string 1004 MUST NOT be truncated. 1006 (Note that this use of the identity KDF is a technicality. The 1007 complete picture is that ECDH is employed with a non-trivial KDF 1008 because TLS does not directly use the premaster secret for anything 1009 other than for computing the master secret. In TLS 1.0 and 1.1, this 1010 means that the MD5- and SHA-1-based TLS PRF serves as a KDF; in TLS 1011 1.2 the KDF is determined by ciphersuite; it is conceivable that 1012 future TLS versions or new TLS extensions introduced in the future 1013 may vary this computation.) 1015 An ECDHE key exchange using Curve25519 goes as follows. Each party 1016 picks a secret key d uniformly at random and computes the 1017 corresponding public key x = Curve25519(d, G). Parties exchange 1018 their public keys and compute a shared secret as x_S = Curve25519(d, 1019 x_peer). ECDHE for Curve448 works similarily, replacing Curve25519 1020 with Curve448. The derived shared secret is used directly as the 1021 premaster secret, which is always exactly 32 bytes when ECDHE with 1022 Curve25519 is used and 56 bytes when ECDHE with Curve448 is used. 1024 All ECDSA computations MUST be performed according to ANSI X9.62 or 1025 its successors. Data to be signed/verified is hashed, and the result 1026 run directly through the ECDSA algorithm with no additional hashing. 1027 The default hash function is SHA-1 [FIPS.180-2], and sha_size (see 1028 Section 5.4 and Section 5.8) is 20. However, an alternative hash 1029 function, such as one of the new SHA hash functions specified in FIPS 1030 180-2 [FIPS.180-2], may be used instead. 1032 RFC 4492 anticipated the standardization of a mechanism for 1033 specifying the required hash function in the certificate, perhaps in 1034 the parameters field of the subjectPublicKeyInfo. Such 1035 standardization never took place, and as a result, SHA-1 is used in 1036 TLS 1.1 and earlier. TLS 1.2 added a SignatureAndHashAlgorithm 1037 parameter to the DigitallySigned struct, thus allowing agility in 1038 choosing the signature hash. 1040 All RSA signatures must be generated and verified according to 1041 [PKCS1] block type 1. 1043 5.11. Public Key Validation 1045 With the NIST curves, each party must validate the public key sent by 1046 its peer before performing cryptographic computations with it. 1047 Failing to do so allows attackers to gain information about the 1048 private key, to the point that they may recover the entire private 1049 key in a few requests, if that key is not really ephemeral. 1051 Curve25519 was designed in a way that the result of Curve25519(x, d) 1052 will never reveal information about d, provided it was chosen as 1053 prescribed, for any value of x. 1055 Let's define legitimate values of x as the values that can be 1056 obtained as x = Curve25519(G, d') for some d, and call the other 1057 values illegitimate. The definition of the Curve25519 function shows 1058 that legitimate values all share the following property: the high- 1059 order bit of the last byte is not set. 1061 Since there are some implementation of the Curve25519 function that 1062 impose this restriction on their input and others that don't, 1063 implementations of Curve25519 in TLS SHOULD reject public keys when 1064 the high-order bit of the last byte is set (in other words, when the 1065 value of the leftmost byte is greater than 0x7F) in order to prevent 1066 implementation fingerprinting. 1068 Other than this recommended check, implementations do not need to 1069 ensure that the public keys they receive are legitimate: this is not 1070 necessary for security with Curve25519. 1072 6. Cipher Suites 1074 The table below defines new ECC cipher suites that use the key 1075 exchange algorithms specified in Section 2. 1077 +---------------------------------------+----------------+ 1078 | CipherSuite | Identifier | 1079 +---------------------------------------+----------------+ 1080 | TLS_ECDHE_ECDSA_WITH_NULL_SHA | { 0xC0, 0x06 } | 1081 | TLS_ECDHE_ECDSA_WITH_RC4_128_SHA | { 0xC0, 0x07 } | 1082 | TLS_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA | { 0xC0, 0x08 } | 1083 | TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA | { 0xC0, 0x09 } | 1084 | TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA | { 0xC0, 0x0A } | 1085 | | | 1086 | TLS_ECDHE_RSA_WITH_NULL_SHA | { 0xC0, 0x10 } | 1087 | TLS_ECDHE_RSA_WITH_RC4_128_SHA | { 0xC0, 0x11 } | 1088 | TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA | { 0xC0, 0x12 } | 1089 | TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA | { 0xC0, 0x13 } | 1090 | TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA | { 0xC0, 0x14 } | 1091 | | | 1092 | TLS_ECDH_anon_WITH_NULL_SHA | { 0xC0, 0x15 } | 1093 | TLS_ECDH_anon_WITH_RC4_128_SHA | { 0xC0, 0x16 } | 1094 | TLS_ECDH_anon_WITH_3DES_EDE_CBC_SHA | { 0xC0, 0x17 } | 1095 | TLS_ECDH_anon_WITH_AES_128_CBC_SHA | { 0xC0, 0x18 } | 1096 | TLS_ECDH_anon_WITH_AES_256_CBC_SHA | { 0xC0, 0x19 } | 1097 +---------------------------------------+----------------+ 1099 Table 5: TLS ECC cipher suites 1101 The key exchange method, cipher, and hash algorithm for each of these 1102 cipher suites are easily determined by examining the name. Ciphers 1103 (other than AES ciphers) and hash algorithms are defined in [RFC2246] 1104 and [RFC4346]. AES ciphers are defined in [RFC5246]. 1106 Server implementations SHOULD support all of the following cipher 1107 suites, and client implementations SHOULD support at least one of 1108 them: 1110 o TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 1111 o TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA 1112 o TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 1113 o TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256 1115 7. Security Considerations 1117 Security issues are discussed throughout this memo. 1119 For TLS handshakes using ECC cipher suites, the security 1120 considerations in appendices D of all three TLS base documemts apply 1121 accordingly. 1123 Security discussions specific to ECC can be found in 1124 [IEEE.P1363.1998] and [ANSI.X9-62.2005]. One important issue that 1125 implementers and users must consider is elliptic curve selection. 1126 Guidance on selecting an appropriate elliptic curve size is given in 1127 Table 1. 1129 Beyond elliptic curve size, the main issue is elliptic curve 1130 structure. As a general principle, it is more conservative to use 1131 elliptic curves with as little algebraic structure as possible. 1132 Thus, random curves are more conservative than special curves such as 1133 Koblitz curves, and curves over F_p with p random are more 1134 conservative than curves over F_p with p of a special form (and 1135 curves over F_p with p random might be considered more conservative 1136 than curves over F_2^m as there is no choice between multiple fields 1137 of similar size for characteristic 2). Note, however, that algebraic 1138 structure can also lead to implementation efficiencies, and 1139 implementers and users may, therefore, need to balance conservatism 1140 against a need for efficiency. Concrete attacks are known against 1141 only very few special classes of curves, such as supersingular 1142 curves, and these classes are excluded from the ECC standards that 1143 this document references [IEEE.P1363.1998], [ANSI.X9-62.2005]. 1145 Another issue is the potential for catastrophic failures when a 1146 single elliptic curve is widely used. In this case, an attack on the 1147 elliptic curve might result in the compromise of a large number of 1148 keys. Again, this concern may need to be balanced against efficiency 1149 and interoperability improvements associated with widely-used curves. 1150 Substantial additional information on elliptic curve choice can be 1151 found in [IEEE.P1363.1998], [ANSI.X9-62.2005], and [FIPS.186-4]. 1153 All of the key exchange algorithms defined in this document provide 1154 forward secrecy. Some of the deprecated key exchange algorithms do 1155 not. 1157 8. IANA Considerations 1159 [RFC4492], the predecessor of this document has already defined the 1160 IANA registries for the following: 1162 o NamedCurve Section 5.1 1163 o ECPointFormat Section 5.1 1164 o ECCurveType Section 5.4 1166 For each name space, this document defines the initial value 1167 assignments and defines a range of 256 values (NamedCurve) or eight 1168 values (ECPointFormat and ECCurveType) reserved for Private Use. Any 1169 additional assignments require IETF Review. 1171 NOTE: IANA, please update the registries to reflect the new policy 1172 name. 1174 NOTE: RFC editor please delete these two notes prior to publication. 1176 IANA, please update these two registries to refer to this document. 1178 IANA is requested to assign two values from the NamedCurve registry 1179 with names Curve25519(TBD1) and Curve448(TBD2) with this document as 1180 reference. 1182 9. Acknowledgements 1184 Most of the text is this document is taken from [RFC4492], the 1185 predecessor of this document. The authors of that document were: 1187 o Simon Blake-Wilson 1188 o Nelson Bolyard 1189 o Vipul Gupta 1190 o Chris Hawk 1191 o Bodo Moeller 1193 In the predecessor document, the authors acknowledged the 1194 contributions of Bill Anderson and Tim Dierks. 1196 10. Version History for This Draft 1198 NOTE TO RFC EDITOR: PLEASE REMOVE THIS SECTION 1200 Changes from draft-ietf-tls-rfc4492bis-01 to draft-nir-tls- 1201 rfc4492bis-03: 1203 o Removed unused curves. 1204 o Removed unused point formats (all but uncompressed) 1206 Changes from draft-nir-tls-rfc4492bis-00 and draft-ietf-tls- 1207 rfc4492bis-00 to draft-nir-tls-rfc4492bis-01: 1209 o Merged errata 1210 o Removed ECDH_RSA and ECDH_ECDSA 1212 Changes from RFC 4492 to draft-nir-tls-rfc4492bis-00: 1214 o Added TLS 1.2 to references. 1215 o Moved RFC 4492 authors to acknowledgements. 1216 o Removed list of required reading for ECC. 1218 11. References 1220 11.1. Normative References 1222 [ANSI.X9-62.2005] 1223 American National Standards Institute, "Public Key 1224 Cryptography for the Financial Services Industry, The 1225 Elliptic Curve Digital Signature Algorithm (ECDSA)", ANSI 1226 X9.62, 2005. 1228 [CCITT.X680] 1229 International Telephone and Telegraph Consultative 1230 Committee, "Abstract Syntax Notation One (ASN.1): 1231 Specification of basic notation", CCITT Recommendation 1232 X.680, July 2002. 1234 [CCITT.X690] 1235 International Telephone and Telegraph Consultative 1236 Committee, "ASN.1 encoding rules: Specification of basic 1237 encoding Rules (BER), Canonical encoding rules (CER) and 1238 Distinguished encoding rules (DER)", CCITT Recommendation 1239 X.690, July 2002. 1241 [CFRG-Curves] 1242 Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves 1243 for Security", draft-irtf-cfrg-curves-11 (work in 1244 progress), October 2015. 1246 [FIPS.186-4] 1247 National Institute of Standards and Technology, "Digital 1248 Signature Standard", FIPS PUB 186-4, 2013, 1249 . 1252 [PKCS1] RSA Laboratories, "RSA Encryption Standard, Version 1.5", 1253 PKCS 1, November 1993. 1255 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1256 Requirement Levels", BCP 14, RFC 2119, March 1997. 1258 [RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", 1259 RFC 2246, January 1999. 1261 [RFC3279] Bassham, L., Polk, W., and R. Housley, "Algorithms and 1262 Identifiers for the Internet X.509 Public Key 1263 Infrastructure Certificate and Certificate Revocation List 1264 (CRL) Profile", RFC 3279, April 2002. 1266 [RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security 1267 (TLS) Protocol Version 1.1", RFC 4346, April 2006. 1269 [RFC4366] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., 1270 and T. Wright, "Transport Layer Security (TLS) 1271 Extensions", RFC 4366, April 2006. 1273 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 1274 (TLS) Protocol Version 1.2", RFC 5246, August 2008. 1276 [SECG-SEC2] 1277 CECG, "Recommended Elliptic Curve Domain Parameters", SEC 1278 2, 2000. 1280 11.2. Informative References 1282 [FIPS.180-2] 1283 National Institute of Standards and Technology, "Secure 1284 Hash Standard", FIPS PUB 180-2, August 2002, 1285 . 1288 [I-D.ietf-tls-tls13] 1289 Dierks, T. and E. Rescorla, "The Transport Layer Security 1290 (TLS) Protocol Version 1.3", draft-ietf-tls-tls13-02 (work 1291 in progress), July 2014. 1293 [IEEE.P1363.1998] 1294 Institute of Electrical and Electronics Engineers, 1295 "Standard Specifications for Public Key Cryptography", 1296 IEEE Draft P1363, 1998. 1298 [Lenstra_Verheul] 1299 Lenstra, A. and E. Verheul, "Selecting Cryptographic Key 1300 Sizes", Journal of Cryptology 14 (2001) 255-293, 2001. 1302 [RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B. 1303 Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites 1304 for Transport Layer Security (TLS)", RFC 4492, May 2006. 1306 Appendix A. Equivalent Curves (Informative) 1308 All of the NIST curves [FIPS.186-4] and several of the ANSI curves 1309 [ANSI.X9-62.2005] are equivalent to curves listed in Section 5.1.1. 1310 In the following table, multiple names in one row represent aliases 1311 for the same curve. 1313 Curve names chosen by different standards organizations 1315 +-----------+------------+------------+ 1316 | SECG | ANSI X9.62 | NIST | 1317 +-----------+------------+------------+ 1318 | sect163k1 | | NIST K-163 | 1319 | sect163r1 | | | 1320 | sect163r2 | | NIST B-163 | 1321 | sect193r1 | | | 1322 | sect193r2 | | | 1323 | sect233k1 | | NIST K-233 | 1324 | sect233r1 | | NIST B-233 | 1325 | sect239k1 | | | 1326 | sect283k1 | | NIST K-283 | 1327 | sect283r1 | | NIST B-283 | 1328 | sect409k1 | | NIST K-409 | 1329 | sect409r1 | | NIST B-409 | 1330 | sect571k1 | | NIST K-571 | 1331 | sect571r1 | | NIST B-571 | 1332 | secp160k1 | | | 1333 | secp160r1 | | | 1334 | secp160r2 | | | 1335 | secp192k1 | | | 1336 | secp192r1 | prime192v1 | NIST P-192 | 1337 | secp224k1 | | | 1338 | secp224r1 | | NIST P-224 | 1339 | secp256k1 | | | 1340 | secp256r1 | prime256v1 | NIST P-256 | 1341 | secp384r1 | | NIST P-384 | 1342 | secp521r1 | | NIST P-521 | 1343 +-----------+------------+------------+ 1345 Table 6: Equivalent curves defined by SECG, ANSI, and NIST 1347 Appendix B. Differences from RFC 4492 1349 o Added TLS 1.2 1350 o Merged Errata 1351 o Removed the ECDH key exchange algorithms: ECDH_RSA and ECDH_ECDSA 1352 o Deprecated a bunch of ciphersuites: 1354 TLS_ECDH_ECDSA_WITH_NULL_SHA 1355 TLS_ECDH_ECDSA_WITH_RC4_128_SHA 1356 TLS_ECDH_ECDSA_WITH_3DES_EDE_CBC_SHA 1357 TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA 1358 TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA 1359 TLS_ECDH_RSA_WITH_NULL_SHA 1360 TLS_ECDH_RSA_WITH_RC4_128_SHA 1361 TLS_ECDH_RSA_WITH_3DES_EDE_CBC_SHA 1362 TLS_ECDH_RSA_WITH_AES_128_CBC_SHA 1363 TLS_ECDH_RSA_WITH_AES_256_CBC_SHA 1365 Removed unused curves and all but the uncompressed point format. 1367 Added Curve25519 and Curve448. 1369 Deprecated explicit curves. 1371 Authors' Addresses 1373 Yoav Nir 1374 Check Point Software Technologies Ltd. 1375 5 Hasolelim st. 1376 Tel Aviv 6789735 1377 Israel 1379 Email: ynir.ietf@gmail.com 1381 Simon Josefsson 1382 SJD AB 1384 Email: simon@josefsson.org 1386 Manuel Pegourie-Gonnard 1387 Independent / PolarSSL 1389 Email: mpg@elzevir.fr