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'3') (Obsoleted by RFC 4366) -- Possible downref: Non-RFC (?) normative reference: ref. '4' -- Possible downref: Non-RFC (?) normative reference: ref. '5' -- Possible downref: Non-RFC (?) normative reference: ref. '6' -- Possible downref: Non-RFC (?) normative reference: ref. '7' -- Possible downref: Non-RFC (?) normative reference: ref. '8' -- Possible downref: Non-RFC (?) normative reference: ref. '9' -- Possible downref: Non-RFC (?) normative reference: ref. '10' -- Obsolete informational reference (is this intentional?): RFC 3268 (ref. '14') (Obsoleted by RFC 5246) Summary: 5 errors (**), 0 flaws (~~), 9 warnings (==), 11 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 TLS Working Group V. Gupta 3 Internet-Draft Sun Labs 4 Expires: October 30, 2004 S. Blake-Wilson 5 BCI 6 B. Moeller 7 University of California, Berkeley 8 C. Hawk 9 Independent Consultant 10 N. Bolyard 11 Netscape 12 May. 2004 14 ECC Cipher Suites for TLS 15 17 Status of this Memo 19 This document is an Internet-Draft and is in full conformance with 20 all provisions of Section 10 of RFC2026. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF), its areas, and its working groups. Note that 24 other groups may also distribute working documents as Internet- 25 Drafts. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 The list of current Internet-Drafts can be accessed at http:// 33 www.ietf.org/ietf/1id-abstracts.txt. 35 The list of Internet-Draft Shadow Directories can be accessed at 36 http://www.ietf.org/shadow.html. 38 This Internet-Draft will expire on October 30, 2004. 40 Copyright Notice 42 Copyright (C) The Internet Society (2004). All Rights Reserved. 44 Abstract 46 This document describes new key exchange algorithms based on Elliptic 47 Curve Cryptography (ECC) for the TLS (Transport Layer Security) 48 protocol. In particular, it specifies the use of Elliptic Curve 49 Diffie-Hellman (ECDH) key agreement in a TLS handshake and the use of 50 Elliptic Curve Digital Signature Algorithm (ECDSA) as a new 51 authentication mechanism. 53 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 54 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 55 document are to be interpreted as described in RFC 2119 [1]. 57 Please send comments on this document to the TLS mailing list. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 62 2. Key Exchange Algorithms . . . . . . . . . . . . . . . . . . 5 63 2.1 ECDH_ECDSA . . . . . . . . . . . . . . . . . . . . . . . . . 7 64 2.2 ECDHE_ECDSA . . . . . . . . . . . . . . . . . . . . . . . . 7 65 2.3 ECDH_RSA . . . . . . . . . . . . . . . . . . . . . . . . . . 7 66 2.4 ECDHE_RSA . . . . . . . . . . . . . . . . . . . . . . . . . 7 67 2.5 ECDH_anon . . . . . . . . . . . . . . . . . . . . . . . . . 8 68 3. Client Authentication . . . . . . . . . . . . . . . . . . . 9 69 3.1 ECDSA_sign . . . . . . . . . . . . . . . . . . . . . . . . . 9 70 3.2 ECDSA_fixed_ECDH . . . . . . . . . . . . . . . . . . . . . . 10 71 3.3 RSA_fixed_ECDH . . . . . . . . . . . . . . . . . . . . . . . 10 72 4. TLS Extensions for ECC . . . . . . . . . . . . . . . . . . . 11 73 5. Data Structures and Computations . . . . . . . . . . . . . . 12 74 5.1 Client Hello Extensions . . . . . . . . . . . . . . . . . . 12 75 5.2 Server Hello Extensions . . . . . . . . . . . . . . . . . . 15 76 5.3 Server Certificate . . . . . . . . . . . . . . . . . . . . . 16 77 5.4 Server Key Exchange . . . . . . . . . . . . . . . . . . . . 17 78 5.5 Certificate Request . . . . . . . . . . . . . . . . . . . . 21 79 5.6 Client Certificate . . . . . . . . . . . . . . . . . . . . . 21 80 5.7 Client Key Exchange . . . . . . . . . . . . . . . . . . . . 23 81 5.8 Certificate Verify . . . . . . . . . . . . . . . . . . . . . 24 82 5.9 Elliptic Curve Certificates . . . . . . . . . . . . . . . . 25 83 5.10 ECDH, ECDSA and RSA Computations . . . . . . . . . . . . . . 25 84 6. Cipher Suites . . . . . . . . . . . . . . . . . . . . . . . 27 85 7. Security Considerations . . . . . . . . . . . . . . . . . . 29 86 8. Intellectual Property Rights . . . . . . . . . . . . . . . . 30 87 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 31 88 Normative References . . . . . . . . . . . . . . . . . . . . 32 89 Informative References . . . . . . . . . . . . . . . . . . . 33 90 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 33 91 Full Copyright Statement . . . . . . . . . . . . . . . . . . 35 93 1. Introduction 95 Elliptic Curve Cryptography (ECC) is emerging as an attractive 96 public-key cryptosystem for mobile/wireless environments. Compared 97 to currently prevalent cryptosystems such as RSA, ECC offers 98 equivalent security with smaller key sizes. This is illustrated in 99 the following table, based on [12], which gives approximate 100 comparable key sizes for symmetric- and asymmetric-key cryptosystems 101 based on the best-known algorithms for attacking them. 103 Symmetric | ECC | DH/DSA/RSA 104 -------------+---------+------------ 105 80 | 163 | 1024 106 112 | 233 | 2048 107 128 | 283 | 3072 108 192 | 409 | 7680 109 256 | 571 | 15360 111 Table 1: Comparable key sizes (in bits) 113 Smaller key sizes result in power, bandwidth and computational 114 savings that make ECC especially attractive for constrained 115 environments. 117 This document describes additions to TLS to support ECC. In 118 particular, it defines 120 o the use of the Elliptic Curve Diffie-Hellman (ECDH) key agreement 121 scheme with long-term or ephemeral keys to establish the TLS 122 premaster secret, and 124 o the use of fixed-ECDH certificates and ECDSA for authentication of 125 TLS peers. 127 The remainder of this document is organized as follows. Section 2 128 provides an overview of ECC-based key exchange algorithms for TLS. 129 Section 3 describes the use of ECC certificates for client 130 authentication. TLS extensions that allow a client to negotiate the 131 use of specific curves and point formats are presented in Section 4. 132 Section 5 specifies various data structures needed for an ECC-based 133 handshake, their encoding in TLS messages and the processing of those 134 messages. Section 6 defines new ECC-based cipher suites and 135 identifies a small subset of these as recommended for all 136 implementations of this specification. Section 7, Section 8 and 137 Section 9 mention security considerations, intellectual property 138 rights, and acknowledgments, respectively. This is followed by a 139 list of references cited in this document and the authors' contact 140 information. 142 Implementation of this specification requires familiarity with TLS 143 [2], TLS extensions [3] and ECC [4][5][6][8] . 145 2. Key Exchange Algorithms 147 This document introduces five new ECC-based key exchange algorithms 148 for TLS. All of them use ECDH to compute the TLS premaster secret 149 and differ only in the lifetime of ECDH keys (long-term or ephemeral) 150 and the mechanism (if any) used to authenticate them. The derivation 151 of the TLS master secret from the premaster secret and the subsequent 152 generation of bulk encryption/MAC keys and initialization vectors is 153 independent of the key exchange algorithm and not impacted by the 154 introduction of ECC. 156 The table below summarizes the new key exchange algorithms which 157 mimic DH_DSS, DH_RSA, DHE_DSS, DHE_RSA and DH_anon (see [2]), 158 respectively. 160 Key 161 Exchange 162 Algorithm Description 163 --------- ----------- 165 ECDH_ECDSA Fixed ECDH with ECDSA-signed certificates. 167 ECDHE_ECDSA Ephemeral ECDH with ECDSA signatures. 169 ECDH_RSA Fixed ECDH with RSA-signed certificates. 171 ECDHE_RSA Ephemeral ECDH with RSA signatures. 173 ECDH_anon Anonymous ECDH, no signatures. 175 Table 2: ECC key exchange algorithms 177 The ECDHE_ECDSA and ECDHE_RSA key exchange mechanisms provide forward 178 secrecy. With ECDHE_RSA, a server can reuse its existing RSA 179 certificate and easily comply with a constrained client's elliptic 180 curve preferences (see Section 4). However, the computational cost 181 incurred by a server is higher for ECDHE_RSA than for the traditional 182 RSA key exchange which does not provide forward secrecy. 184 The ECDH_RSA mechanism requires a server to acquire an ECC 185 certificate but the certificate issuer can still use an existing RSA 186 key for signing. This eliminates the need to update the trusted key 187 store in TLS clients. The ECDH_ECDSA mechanism requires ECC keys for 188 the server as well as the certification authority and is best suited 189 for constrained devices unable to support RSA. 191 The anonymous key exchange algorithm does not provide authentication 192 of the server or the client. Like other anonymous TLS key exchanges, 193 it is subject to man-in-the-middle attacks. Implementations of this 194 algorithm SHOULD provide authentication by other means. 196 Note that there is no structural difference between ECDH and ECDSA 197 keys. A certificate issuer may use X509.v3 keyUsage and 198 extendedKeyUsage extensions to restrict the use of an ECC public key 199 to certain computations. This document refers to an ECC key as ECDH- 200 capable if its use in ECDH is permitted. ECDSA-capable is defined 201 similarly. 203 Client Server 204 ------ ------ 206 ClientHello --------> 207 ServerHello 208 Certificate* 209 ServerKeyExchange* 210 CertificateRequest*+ 211 <-------- ServerHelloDone 212 Certificate*+ 213 ClientKeyExchange 214 CertificateVerify*+ 215 [ChangeCipherSpec] 216 Finished --------> 217 [ChangeCipherSpec] 218 <-------- Finished 220 Application Data <-------> Application Data 222 Figure 1: Message flow in a full TLS handshake 223 * message is not sent under some conditions 224 + message is not sent unless the client is 225 authenticated 227 Figure 1 shows all messages involved in the TLS key establishment 228 protocol (aka full handshake). The addition of ECC has direct impact 229 only on the ClientHello, the ServerHello, the server's Certificate 230 message, the ServerKeyExchange, the ClientKeyExchange, the 231 CertificateRequest, the client's Certificate message, and the 232 CertificateVerify. Next, we describe each ECC key exchange algorithm 233 in greater detail in terms of the content and processing of these 234 messages. For ease of exposition, we defer discussion of client 235 authentication and associated messages (identified with a + in Figure 236 1) until Section 3 and of the optional ECC-specific extensions (which 237 impact the Hello messages) until Section 4. 239 2.1 ECDH_ECDSA 241 In ECDH_ECDSA, the server's certificate MUST contain an ECDH-capable 242 public key and be signed with ECDSA. 244 A ServerKeyExchange MUST NOT be sent (the server's certificate 245 contains all the necessary keying information required by the client 246 to arrive at the premaster secret). 248 The client MUST generate an ECDH key pair on the same curve as the 249 server's long-term public key and send its public key in the 250 ClientKeyExchange message (except when using client authentication 251 algorithm ECDSA_fixed_ECDH or RSA_fixed_ECDH, in which case the 252 modifications from section Section 3.2 or Section 3.3 apply). 254 Both client and server MUST perform an ECDH operation and use the 255 resultant shared secret as the premaster secret. All ECDH 256 calculations are performed as specified in Section 5.10 258 2.2 ECDHE_ECDSA 260 In ECDHE_ECDSA, the server's certificate MUST contain an ECDSA- 261 capable public key and be signed with ECDSA. 263 The server MUST send its ephemeral ECDH public key and a 264 specification of the corresponding curve in the ServerKeyExchange 265 message. These parameters MUST be signed with ECDSA using the 266 private key corresponding to the public key in the server's 267 Certificate. 269 The client MUST generate an ECDH key pair on the same curve as the 270 server's ephemeral ECDH key and send its public key in the 271 ClientKeyExchange message. 273 Both client and server MUST perform an ECDH operation (Section 5.10) 274 and use the resultant shared secret as the premaster secret. 276 2.3 ECDH_RSA 278 This key exchange algorithm is the same as ECDH_ECDSA except the 279 server's certificate MUST be signed with RSA rather than ECDSA. 281 2.4 ECDHE_RSA 283 This key exchange algorithm is the same as ECDHE_ECDSA except the 284 server's certificate MUST contain an RSA public key authorized for 285 signing and the signature in the ServerKeyExchange message MUST be 286 computed with the corresponding RSA private key. The server 287 certificate MUST be signed with RSA. 289 2.5 ECDH_anon 291 In ECDH_anon, the server's Certificate, the CertificateRequest, the 292 client's Certificate, and the CertificateVerify messages MUST NOT be 293 sent. 295 The server MUST send an ephemeral ECDH public key and a specification 296 of the corresponding curve in the ServerKeyExchange message. These 297 parameters MUST NOT be signed. 299 The client MUST generate an ECDH key pair on the same curve as the 300 server's ephemeral ECDH key and send its public key in the 301 ClientKeyExchange message. 303 Both client and server MUST perform an ECDH operation and use the 304 resultant shared secret as the premaster secret. All ECDH 305 calculations are performed as specified in Section 5.10 307 3. Client Authentication 309 This document defines three new client authentication mechanisms 310 named after the type of client certificate involved: ECDSA_sign, 311 ECDSA_fixed_ECDH and RSA_fixed_ECDH. The ECDSA_sign mechanism is 312 usable with any of the non-anonymous ECC key exchange algorithms 313 described in Section 2 as well as other non-anonymous (non-ECC) key 314 exchange algorithms defined in TLS [2]. The ECDSA_fixed_ECDH and 315 RSA_fixed_ECDH mechanisms are usable with ECDH_ECDSA and ECDH_RSA. 316 Their use with ECDHE_ECDSA and ECDHE_RSA is prohibited because the 317 use of a long-term ECDH client key would jeopardize the forward 318 secrecy property of these algorithms. 320 The server can request ECC-based client authentication by including 321 one or more of these certificate types in its CertificateRequest 322 message. The server MUST NOT include any certificate types that are 323 prohibited for the negotiated key exchange algorithm. The client 324 must check if it possesses a certificate appropriate for any of the 325 methods suggested by the server and is willing to use it for 326 authentication. 328 If these conditions are not met, the client should send a client 329 Certificate message containing no certificates. In this case, the 330 ClientKeyExchange should be sent as described in Section 2 and the 331 CertificateVerify should not be sent. If the server requires client 332 authentication, it may respond with a fatal handshake failure alert. 334 If the client has an appropriate certificate and is willing to use it 335 for authentication, it MUST send that certificate in the client's 336 Certificate message (as per Section 5.6) and prove possession of the 337 private key corresponding to the certified key. The process of 338 determining an appropriate certificate and proving possession is 339 different for each authentication mechanism and described below. 341 NOTE: It is permissible for a server to request (and the client to 342 send) a client certificate of a different type than the server 343 certificate. 345 3.1 ECDSA_sign 347 To use this authentication mechanism, the client MUST possess a 348 certificate containing an ECDSA-capable public key and signed with 349 ECDSA. 351 The client MUST prove possession of the private key corresponding to 352 the certified key by including a signature in the CertificateVerify 353 message as described in Section 5.8. 355 3.2 ECDSA_fixed_ECDH 357 To use this authentication mechanism, the client MUST possess a 358 certificate containing an ECDH-capable public key and that 359 certificate MUST be signed with ECDSA. Furthermore, the client's 360 ECDH key MUST be on the same elliptic curve as the server's long-term 361 (certified) ECDH key. This might limit use of this mechanism to 362 closed environments. In situations where the client has an ECC key 363 on a different curve, it would have to authenticate either using 364 ECDSA_sign or a non-ECC mechanism (e.g. RSA). Using fixed ECDH for 365 both servers and clients is computationally more efficient than 366 mechanisms providing forward secrecy. 368 When using this authentication mechanism, the client MUST send an 369 empty ClientKeyExchange as described in Section 5.7 and MUST NOT send 370 the CertificateVerify message. The ClientKeyExchange is empty since 371 the client's ECDH public key required by the server to compute the 372 premaster secret is available inside the client's certificate. The 373 client's ability to arrive at the same premaster secret as the server 374 (demonstrated by a successful exchange of Finished messages) proves 375 possession of the private key corresponding to the certified public 376 key and the CertificateVerify message is unnecessary. 378 3.3 RSA_fixed_ECDH 380 This authentication mechanism is identical to ECDSA_fixed_ECDH except 381 the client's certificate MUST be signed with RSA. 383 4. TLS Extensions for ECC 385 Two new TLS extensions --- (i) the Supported Elliptic Curves 386 Extension, and (ii) the Supported Point Formats Extension --- allow a 387 client to negotiate the use of specific curves and point formats 388 (e.g. compressed v/s uncompressed), respectively. These extensions 389 are especially relevant for constrained clients that may only support 390 a limited number of curves or point formats. They follow the 391 general approach outlined in [3]. The client enumerates the curves 392 and point formats it supports by including the appropriate extensions 393 in its ClientHello message. By echoing that extension in its 394 ServerHello, the server agrees to restrict its key selection or 395 encoding to the choices specified by the client. 397 A TLS client that proposes ECC cipher suites in its ClientHello 398 message SHOULD include these extensions. Servers implementing ECC 399 cipher suites MUST support these extensions and negotiate the use of 400 an ECC cipher suite only if they can complete the handshake while 401 limiting themselves to the curves and compression techniques 402 enumerated by the client. This eliminates the possibility that a 403 negotiated ECC handshake will be subsequently aborted due to a 404 client's inability to deal with the server's EC key. 406 These extensions MUST NOT be included if the client does not propose 407 any ECC cipher suites. A client that proposes ECC cipher suites may 408 choose not to include these extension. In this case, the server is 409 free to choose any one of the elliptic curves or point formats listed 410 in Section 5. That section also describes the structure and 411 processing of these extensions in greater detail. 413 5. Data Structures and Computations 415 This section specifies the data structures and computations used by 416 ECC-based key mechanisms specified in Section 2, Section 3 and 417 Section 4. The presentation language used here is the same as that 418 used in TLS [2]. Since this specification extends TLS, these 419 descriptions should be merged with those in the TLS specification and 420 any others that extend TLS. This means that enum types may not 421 specify all possible values and structures with multiple formats 422 chosen with a select() clause may not indicate all possible cases. 424 5.1 Client Hello Extensions 426 When this message is sent: 428 The ECC extensions SHOULD be sent along with any ClientHello message 429 that proposes ECC cipher suites. 431 Meaning of this message: 433 These extensions allow a constrained client to enumerate the elliptic 434 curves and/or point formats it supports. 436 Structure of this message: 438 The general structure of TLS extensions is described in [3] and this 439 specification adds two new types to ExtensionType. 441 enum { elliptic_curves(6), ec_point_formats(7) } ExtensionType; 443 elliptic_curves: Indicates the set of elliptic curves supported by 444 the client. For this extension, the opaque extension_data field 445 contains EllipticCurveList. 447 ec_point_formats: Indicates the set of point formats supported by 448 the client. For this extension, the opaque extension_data field 449 contains ECPointFormatList. 451 enum { 452 sect163k1 (1), sect163r1 (2), sect163r2 (3), 453 sect193r1 (4), sect193r2 (5), sect233k1 (6), 454 sect233r1 (7), sect239k1 (8), sect283k1 (9), 455 sect283r1 (10), sect409k1 (11), sect409r1 (12), 456 sect571k1 (13), sect571r1 (14), secp160k1 (15), 457 secp160r1 (16), secp160r2 (17), secp192k1 (18), 458 secp192r1 (19), secp224k1 (20), secp224r1 (21), 459 secp256k1 (22), secp256r1 (23), secp384r1 (24), 460 secp521r1 (25), reserved (240..247), 461 arbitrary_explicit_prime_curves(253), 462 arbitrary_explicit_char2_curves(254), 463 (255) 464 } NamedCurve; 466 sect163k1, etc: Indicates support of the corresponding named curve 467 specified in SEC 2 [10]. Note that many of these curves are also 468 recommended in ANSI X9.62 [6], and FIPS 186-2 [8]. Values 240 469 through 247 are reserved for private use. Values 253 and 254 470 indicate that the client supports arbitrary prime and 471 characteristic-2 curves, respectively (the curve parameters must 472 be encoded explicitly in ECParameters). 474 struct { 475 NamedCurve elliptic_curve_list<1..2^8-1> 476 } EllipticCurveList; 478 Items in elliptic_curve_list are ordered according to the client's 479 preferences (favorite choice first). 481 As an example, a client that only supports secp192r1 (aka NIST P-192) 482 and secp224r1 (aka NIST P-224) and prefers to use secp192r1, would 483 include an elliptic_curves extension with the following octets: 485 00 06 02 13 15 487 A client that supports arbitrary explicit binary polynomial curves 488 would include an extension with the following octets: 490 00 06 01 fe 491 enum { uncompressed (0), ansiX963_compressed (1), 492 ansiX963_hybrid (2), (255) 493 } ECPointFormat; 495 struct { 496 ECPointFormat ec_point_format_list<1..2^8-1> 497 } ECPointFormatList; 499 Three point formats are included in the defintion of ECPointFormat 500 above. The uncompressed point format is the default format that 501 implementations of this document MUST support. The 502 ansix963_compressed format reduces bandwidth by including only the x- 503 coordinate and a single bit of the y-coordinate of the point. The 504 ansix963_hybrid format includes both the full y-coordinate and the 505 compressed y-coordinate to allow flexibility and improve efficiency 506 in some cases. Implementations of this document MAY support the 507 ansix963_compressed and ansix963_hybrid point formats. 509 Items in ec_point_format_list are ordered according to the client's 510 preferences (favorite choice first). 512 A client that only supports the uncompressed point format includes an 513 extension with the following octets: 515 00 07 01 00 517 A client that prefers the use of the ansiX963_compressed format over 518 uncompressed may indicate that preference by including an extension 519 with the following octets: 521 00 07 02 01 00 523 Actions of the sender: 525 A client that proposes ECC cipher suites in its ClientHello appends 526 these extensions (along with any others) enumerating the curves and 527 point formats it supports. 529 Actions of the receiver: 531 A server that receives a ClientHello containing one or both of these 532 extensions MUST use the client's enumerated capabilities to guide its 533 selection of an appropriate cipher suite. One of the proposed ECC 534 cipher suites must be negotiated only if the server can successfully 535 complete the handshake while using the curves and point formats 536 supported by the client. 538 NOTE: A server participating in an ECDHE-ECDSA key exchange may use 539 different curves for (i) the ECDSA key in its certificate, and (ii) 540 the ephemeral ECDH key in the ServerKeyExchange message. The server 541 must consider the "elliptic_curves" extension in selecting both of 542 these curves. 544 If a server does not understand the "elliptic_curves" extension or is 545 unable to complete the ECC handshake while restricting itself to the 546 enumerated curves, it MUST NOT negotiate the use of an ECC cipher 547 suite. Depending on what other cipher suites are proposed by the 548 client and supported by the server, this may result in a fatal 549 handshake failure alert due to the lack of common cipher suites. 551 5.2 Server Hello Extensions 553 When this message is sent: 555 The ServerHello ECC extensions are sent in response to a Client Hello 556 message containing ECC extensions when negotiating an ECC cipher 557 suite. 559 Meaning of this message: 561 These extensions indicate the server's agreement to use only the 562 elliptic curves and point formats supported by the client during the 563 ECC-based key exchange. 565 Structure of this message: 567 The ECC extensions echoed by the server are the same as those in the 568 ClientHello except the "extension_data" field is empty. 570 For example, a server indicates its acceptance of the client's 571 elliptic_curves extension by sending an extension with the following 572 octets: 574 00 06 00 00 576 Actions of the sender: 578 A server makes sure that it can complete a proposed ECC key exchange 579 mechanism by restricting itself to the curves/point formats supported 580 by the client before sending these extensions. 582 Actions of the receiver: 584 A client that receives a ServerHello with ECC extensions proceeds 585 with an ECC key exchange assured that it will be able to handle the 586 server's EC key(s). 588 5.3 Server Certificate 590 When this message is sent: 592 This message is sent in all non-anonymous ECC-based key exchange 593 algorithms. 595 Meaning of this message: 597 This message is used to authentically convey the server's static 598 public key to the client. The following table shows the server 599 certificate type appropriate for each key exchange algorithm. ECC 600 public keys must be encoded in certificates as described in Section 601 5.9. 603 NOTE: The server's Certificate message is capable of carrying a chain 604 of certificates. The restrictions mentioned in Table 3 apply only to 605 the server's certificate (first in the chain). 607 Key Exchange Algorithm Server Certificate Type 608 ---------------------- ----------------------- 610 ECDH_ECDSA Certificate must contain an 611 ECDH-capable public key. It 612 must be signed with ECDSA. 614 ECDHE_ECDSA Certificate must contain an 615 ECDSA-capable public key. It 616 must be signed with ECDSA. 618 ECDH_RSA Certificate must contain an 619 ECDH-capable public key. It 620 must be signed with RSA. 622 ECDHE_RSA Certificate must contain an 623 RSA public key authorized for 624 use in digital signatures. It 625 must be signed with RSA. 627 Table 3: Server certificate types 629 Structure of this message: 631 Identical to the TLS Certificate format. 633 Actions of the sender: 635 The server constructs an appropriate certificate chain and conveys it 636 to the client in the Certificate message. 638 Actions of the receiver: 640 The client validates the certificate chain, extracts the server's 641 public key, and checks that the key type is appropriate for the 642 negotiated key exchange algorithm. 644 5.4 Server Key Exchange 646 When this message is sent: 648 This message is sent when using the ECDHE_ECDSA, ECDHE_RSA and 649 ECDH_anon key exchange algorithms. 651 Meaning of this message: 653 This message is used to convey the server's ephemeral ECDH public key 654 (and the corresponding elliptic curve domain parameters) to the 655 client. 657 Structure of this message: 659 enum { explicit_prime (1), explicit_char2 (2), 660 named_curve (3), (255) } ECCurveType; 662 explicit_prime: Indicates the elliptic curve domain parameters are 663 conveyed verbosely, and the underlying finite field is a prime 664 field. 666 explicit_char2: Indicates the elliptic curve domain parameters are 667 conveyed verbosely, and the underlying finite field is a 668 characteristic-2 field. 670 named_curve: Indicates that a named curve is used. This option 671 SHOULD be used when applicable. 673 struct { 674 opaque a <1..2^8-1>; 675 opaque b <1..2^8-1>; 676 } ECCurve; 678 a, b: These parameters specify the coefficients of the elliptic 679 curve. Each value contains the byte string representation of a 680 field element following the conversion routine in Section 4.3.3 of 681 ANSI X9.62 [6]. 683 struct { 684 opaque point <1..2^8-1>; 685 } ECPoint; 687 point: This is the byte string representation of an elliptic curve 688 point following the conversion routine in Section 4.3.6 of ANSI 689 X9.62 [6]. Note that this byte string may represent an elliptic 690 curve point in compressed or uncompressed form. 692 enum { ec_basis_trinomial, ec_basis_pentanomial } ECBasisType; 694 ec_basis_trinomial: Indicates representation of a characteristic-2 695 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_trinomial: 714 opaque k <1..2^8-1>; 715 case ec_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; 729 curve_type: This identifies the type of the elliptic curve domain 730 parameters. 732 prime_p: This is the odd prime defining the field Fp. 734 curve: Specifies the coefficients a and b of the elliptic curve E. 736 base: Specifies the base point G on the elliptic curve. 738 order: Specifies the order n of the base point. 740 cofactor: Specifies the cofactor h = #E(Fq)/n, where #E(Fq) 741 represents the number of points on the elliptic curve E defined 742 over the field Fq. 744 m: This is the degree of the characteristic-2 field F2^m. 746 k: The exponent k for the trinomial basis representation x^m + x^k 747 +1. 749 k1, k2, k3: The exponents for the pentanomial representation x^m + 750 x^k3 + x^k2 + x^k1 + 1 (such that k3 > k2 > k1). 752 namedcurve: Specifies a recommended set of elliptic curve domain 753 parameters. All enum values of NamedCurve are allowed except for 754 arbitrary_explicit_prime_curves(253) and 755 arbitrary_explicit_char2_curves(254). These two values are only 756 allowed in the ClientHello extension. 758 struct { 759 ECParameters curve_params; 760 ECPoint public; 761 } ServerECDHParams; 763 curve_params: Specifies the elliptic curve domain parameters 764 associated with the ECDH public key. 766 public: The ephemeral ECDH public key. 768 The ServerKeyExchange message is extended as follows. 770 enum { ec_diffie_hellman } KeyExchangeAlgorithm; 772 ec_diffie_hellman: Indicates the ServerKeyExchange message contains 773 an ECDH public key. 775 select (KeyExchangeAlgorithm) { 776 case ec_diffie_hellman: 777 ServerECDHParams params; 778 Signature signed_params; 779 } ServerKeyExchange; 781 params: Specifies the ECDH public key and associated domain 782 parameters. 784 signed_params: A hash of the params, with the signature appropriate 785 to that hash applied. The private key corresponding to the 786 certified public key in the server's Certificate message is used 787 for signing. 789 enum { ecdsa } SignatureAlgorithm; 791 select (SignatureAlgorithm) { 792 case ecdsa: 793 digitally-signed struct { 794 opaque sha_hash[sha_size]; 795 }; 796 } Signature; 798 NOTE: SignatureAlgorithm is 'rsa' for the ECDHE_RSA key exchange 799 algorithm and 'anonymous' for ECDH_anon. These cases are defined in 800 TLS [2]. SignatureAlgorithm is 'ecdsa' for ECDHE_ECDSA. ECDSA 801 signatures are generated and verified as described in Section 5.10. 802 As per ANSI X9.62, an ECDSA signature consists of a pair of integers 803 r and s. These integers are both converted into byte strings of the 804 same length as the curve order n using the conversion routine 805 specified in Section 4.3.1 of [6]. The two byte strings are 806 concatenated, and the result is placed in the signature field. 808 Actions of the sender: 810 The server selects elliptic curve domain parameters and an ephemeral 811 ECDH public key corresponding to these parameters according to the 812 ECKAS-DH1 scheme from IEEE 1363 [5]. It conveys this information to 813 the client in the ServerKeyExchange message using the format defined 814 above. 816 Actions of the recipient: 818 The client verifies the signature (when present) and retrieves the 819 server's elliptic curve domain parameters and ephemeral ECDH public 820 key from the ServerKeyExchange message. 822 5.5 Certificate Request 824 When this message is sent: 826 This message is sent when requesting client authentication. 828 Meaning of this message: 830 The server uses this message to suggest acceptable client 831 authentication methods. 833 Structure of this message: 835 The TLS CertificateRequest message is extended as follows. 837 enum { 838 ecdsa_sign(?), rsa_fixed_ecdh(?), 839 ecdsa_fixed_ecdh(?), (255) 840 } ClientCertificateType; 842 ecdsa_sign, etc Indicates that the server would like to use the 843 corresponding client authentication method specified in Section 3. 845 EDITOR: The values used for ecdsa_sign, rsa_fixed_ecdh, and 846 ecdsa_fixed_ecdh have been left as ?. These values will be 847 assigned when this draft progresses to RFC. Earlier versions of 848 this draft used the values 5, 6, and 7 - however these values have 849 been removed since they are used differently by SSL 3.0 [13] and 850 their use by TLS is being deprecated. 852 Actions of the sender: 854 The server decides which client authentication methods it would like 855 to use, and conveys this information to the client using the format 856 defined above. 858 Actions of the receiver: 860 The client determines whether it has an appropriate certificate for 861 use with any of the requested methods, and decides whether or not to 862 proceed with client authentication. 864 5.6 Client Certificate 866 When this message is sent: 868 This message is sent in response to a CertificateRequest when a 869 client has a suitable certificate. 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 Client 884 Authentication Method Client Certificate Type 885 --------------------- ----------------------- 887 ECDSA_sign Certificate must contain an 888 ECDSA-capable public key and 889 be signed with ECDSA. 891 ECDSA_fixed_ECDH Certificate must contain an 892 ECDH-capable public key on the 893 same elliptic curve as the server's 894 long-term ECDH key. This certificate 895 must be signed with ECDSA. 897 RSA_fixed_ECDH Certificate must contain an 898 ECDH-capable public key on the 899 same elliptic curve as the server's 900 long-term ECDH key. This certificate 901 must be signed with RSA. 903 Table 4: Client certificate types 905 Structure of this message: 907 Identical to the TLS client Certificate format. 909 Actions of the sender: 911 The client constructs an appropriate certificate chain, and conveys 912 it to the server in the Certificate message. 914 Actions of the receiver: 916 The TLS server validates the certificate chain, extracts the client's 917 public key, and checks that the key type is appropriate for the 918 client authentication method. 920 5.7 Client Key Exchange 922 When this message is sent: 924 This message is sent in all key exchange algorithms. If client 925 authentication with ECDSA_fixed_ECDH or RSA_fixed_ECDH is used, this 926 message is empty. Otherwise, it contains the client's ephemeral ECDH 927 public key. 929 Meaning of the message: 931 This message is used to convey ephemeral data relating to the key 932 exchange belonging to the client (such as its ephemeral ECDH public 933 key). 935 Structure of this message: 937 The TLS ClientKeyExchange message is extended as follows. 939 enum { yes, no } EphemeralPublicKey; 941 yes, no: Indicates whether or not the client is providing an 942 ephemeral ECDH public key. (In ECC ciphersuites, this is "yes" 943 except when the client uses the ECDSA_fixed_ECDH or RSA_fixed_ECDH 944 client authentication mechanism.) 946 struct { 947 select (EphemeralPublicKey) { 948 case yes: ECPoint ecdh_Yc; 949 case no: struct { }; 950 } ecdh_public; 951 } ClientECDiffieHellmanPublic; 953 ecdh_Yc: Contains the client's ephemeral ECDH public key. 955 struct { 956 select (KeyExchangeAlgorithm) { 957 case ec_diffie_hellman: ClientECDiffieHellmanPublic; 958 } exchange_keys; 959 } ClientKeyExchange; 961 Actions of the sender: 963 The client selects an ephemeral ECDH public key corresponding to the 964 parameters it received from the server according to the ECKAS-DH1 965 scheme from IEEE 1363 [5]. It conveys this information to the client 966 in the ClientKeyExchange message using the format defined above. 968 Actions of the recipient: 970 The server retrieves the client's ephemeral ECDH public key from the 971 ClientKeyExchange message and checks that it is on the same elliptic 972 curve as the server's ECDH key. 974 5.8 Certificate Verify 976 When this message is sent: 978 This message is sent when the client sends a client certificate 979 containing a public key usable for digital signatures, e.g. when the 980 client is authenticated using the ECDSA_sign mechanism. 982 Meaning of the message: 984 This message contains a signature that proves possession of the 985 private key corresponding to the public key in the client's 986 Certificate message. 988 Structure of this message: 990 The TLS CertificateVerify message is extended as follows. 992 enum { ecdsa } SignatureAlgorithm; 994 select (SignatureAlgorithm) { 995 case ecdsa: 996 digitally-signed struct { 997 opaque sha_hash[sha_size]; 998 }; 999 } Signature; 1001 For the ecdsa case, the signature field in the CertificateVerify 1002 message contains an ECDSA signature computed over handshake messages 1003 exchanged so far. ECDSA signatures are computed as described in 1004 Section 5.10. As per ANSI X9.62, an ECDSA signature consists of a 1005 pair of integers r and s. These integers are both converted into 1006 byte strings of the same length as the curve order n using the 1007 conversion routine specified in Section 4.3.1 of [6]. The two byte 1008 strings are concatenated, and the result is placed in the signature 1009 field. 1011 Actions of the sender: 1013 The client computes its signature over all handshake messages sent or 1014 received starting at client hello up to but not including this 1015 message. It uses the private key corresponding to its certified 1016 public key to compute the signature which is conveyed in the format 1017 defined above. 1019 Actions of the receiver: 1021 The server extracts the client's signature from the CertificateVerify 1022 message, and verifies the signature using the public key it received 1023 in the client's Certificate message. 1025 5.9 Elliptic Curve Certificates 1027 X509 certificates containing ECC public keys or signed using ECDSA 1028 MUST comply with [11] or another RFC that replaces or extends it. 1029 Clients SHOULD use the elliptic curve domain parameters recommended 1030 in ANSI X9.62 [6], FIPS 186-2 [8], and SEC 2 [10]. 1032 5.10 ECDH, ECDSA and RSA Computations 1034 All ECDH calculations (including parameter and key generation as well 1035 as the shared secret calculation) MUST be performed according to [5] 1036 using the ECKAS-DH1 scheme with the identity map as key derivation 1037 function, so that the premaster secret is the x-coordinate of the 1038 ECDH shared secret elliptic curve point, i.e. the octet string Z in 1039 IEEE 1363 terminology. 1041 Note that a new extension may be introduced in the future to allow 1042 the use of a different KDF during computation of the premaster 1043 secret. In this event, the new KDF would be used in place of the 1044 process detailed above. This may be desirable, for example, to 1045 support compatibility with the planned NIST key agreement standard. 1047 All ECDSA computations MUST be performed according to ANSI X9.62 [6] 1048 or its successors. Data to be signed/verified is hashed and the 1049 result run directly through the ECDSA algorithm with no additional 1050 hashing. The default hash function is SHA-1 [7] and sha_size (see 1051 Section 5.4 and Section 5.8) is 20. However, an alternative hash 1052 function, such as one of the new SHA hash functions specified in FIPS 1053 180-2 [7], may be used instead if the certificate containing the EC 1054 public key explicitly requires use of another hash function. (The 1055 mechanism for specifying the required hash function has not been 1056 standardized but this provision anticipates such standardization and 1057 obviates the need to update this document in response. Future PKIX 1058 RFCs may choose, for example, to specify the hash function to be used 1059 with a public key in the parameters field of subjectPublicKeyInfo.) 1061 All RSA signatures must be generated and verified according to PKCS#1 1062 [9]. 1064 6. Cipher Suites 1066 The table below defines new ECC cipher suites that use the key 1067 exchange algorithms specified in Section 2. 1069 CipherSuite TLS_ECDH_ECDSA_WITH_NULL_SHA = { 0x00, 0x?? } 1070 CipherSuite TLS_ECDH_ECDSA_WITH_RC4_128_SHA = { 0x00, 0x?? } 1071 CipherSuite TLS_ECDH_ECDSA_WITH_DES_CBC_SHA = { 0x00, 0x?? } 1072 CipherSuite TLS_ECDH_ECDSA_WITH_3DES_EDE_CBC_SHA = { 0x00, 0x?? } 1073 CipherSuite TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA = { 0x00, 0x?? } 1074 CipherSuite TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA = { 0x00, 0x?? } 1076 CipherSuite TLS_ECDHE_ECDSA_WITH_NULL_SHA = { 0x00, 0x?? } 1077 CipherSuite TLS_ECDHE_ECDSA_WITH_RC4_128_SHA = { 0x00, 0x?? } 1078 CipherSuite TLS_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA = { 0x00, 0x?? } 1079 CipherSuite TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA = { 0x00, 0x?? } 1080 CipherSuite TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA = { 0x00, 0x?? } 1082 CipherSuite TLS_ECDH_RSA_WITH_NULL_SHA = { 0x00, 0x?? } 1083 CipherSuite TLS_ECDH_RSA_WITH_RC4_128_SHA = { 0x00, 0x?? } 1084 CipherSuite TLS_ECDH_RSA_WITH_3DES_EDE_CBC_SHA = { 0x00, 0x?? } 1085 CipherSuite TLS_ECDH_RSA_WITH_AES_128_CBC_SHA = { 0x00, 0x?? } 1086 CipherSuite TLS_ECDH_RSA_WITH_AES_256_CBC_SHA = { 0x00, 0x?? } 1088 CipherSuite TLS_ECDHE_RSA_WITH_NULL_SHA = { 0x00, 0x?? } 1089 CipherSuite TLS_ECDHE_RSA_WITH_RC4_128_SHA = { 0x00, 0x?? } 1090 CipherSuite TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA = { 0x00, 0x?? } 1091 CipherSuite TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA = { 0x00, 0x?? } 1092 CipherSuite TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA = { 0x00, 0x?? } 1094 CipherSuite TLS_ECDH_anon_NULL_WITH_SHA = { 0x00, 0x?? } 1095 CipherSuite TLS_ECDH_anon_WITH_RC4_128_SHA = { 0x00, 0x?? } 1096 CipherSuite TLS_ECDH_anon_WITH_3DES_EDE_CBC_SHA = { 0x00, 0x?? } 1097 CipherSuite TLS_ECDH_anon_WITH_AES_128_CBC_SHA = { 0x00, 0x?? } 1098 CipherSuite TLS_ECDH_anon_WITH_AES_256_CBC_SHA = { 0x00, 0x?? } 1100 Table 5: TLS ECC cipher suites 1102 The key exchange method, cipher, and hash algorithm for each of these 1103 cipher suites are easily determined by examining the name. Ciphers 1104 other than AES ciphers, and hash algorithms are defined in [2]. AES 1105 ciphers are defined in [14]. 1107 Server implementations SHOULD support all of the following cipher 1108 suites, and client implementations SHOULD support at least one of 1109 them: TLS_ECDH_ECDSA_WITH_3DES_EDE_CBC_SHA, 1110 TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA, 1111 TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA, and 1112 TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA. 1114 7. Security Considerations 1116 This document is based on [2], [5], [6] and [14]. The appropriate 1117 security considerations of those documents apply. 1119 One important issue that implementors and users must consider is 1120 elliptic curve selection. Guidance on selecting an appropriate 1121 elliptic curve size is given in Figure 1. 1123 Beyond elliptic curve size, the main issue is elliptic curve 1124 structure. As a general principle, it is more conservative to use 1125 elliptic curves with as little algebraic structure as possible - thus 1126 random curves are more conservative than special curves such as 1127 Koblitz curves, and curves over F_p with p random are more 1128 conservative than curves over F_p with p of a special form (and 1129 curves over F_p with p random might be considered more conservative 1130 than curves over F_2^m as there is no choice between multiple fields 1131 of similar size for characteristic 2). Note, however, that algebraic 1132 structure can also lead to implementation efficiencies and 1133 implementors and users may, therefore, need to balance conservatism 1134 against a need for efficiency. Concrete attacks are known against 1135 only very few special classes of curves, such as supersingular 1136 curves, and these classes are excluded from the ECC standards that 1137 this document references [5], [6]. 1139 Another issue is the potential for catastrophic failures when a 1140 single elliptic curve is widely used. In this case, an attack on the 1141 elliptic curve might result in the compromise of a large number of 1142 keys. Again, this concern may need to be balanced against efficiency 1143 and interoperability improvements associated with widely-used curves. 1144 Substantial additional information on elliptic curve choice can be 1145 found in [4], [5], [6], [8]. 1147 Implementors and users must also consider whether they need forward 1148 secrecy. Forward secrecy refers to the property that session keys 1149 are not compromised if the static, certified keys belonging to the 1150 server and client are compromised. The ECDHE_ECDSA and ECDHE_RSA key 1151 exchange algorithms provide forward secrecy protection in the event 1152 of server key compromise, while ECDH_ECDSA and ECDH_RSA do not. 1153 Similarly if the client is providing a static, certified key, 1154 ECDSA_sign client authentication provides forward secrecy protection 1155 in the event of client key compromise, while ECDSA_fixed_ECDH and 1156 RSA_fixed_ECDH do not. Thus to obtain complete forward secrecy 1157 protection, ECDHE_ECDSA or ECDHE_RSA must be used for key exchange, 1158 with ECDSA_sign used for client authentication if necessary. Here 1159 again the security benefits of forward secrecy may need to be 1160 balanced against the improved efficiency offered by other options. 1162 8. Intellectual Property Rights 1164 The IETF has been notified of intellectual property rights claimed in 1165 regard to the specification contained in this document. For more 1166 information, consult the online list of claimed rights (http:// 1167 www.ietf.org/ipr.html). 1169 The IETF takes no position regarding the validity or scope of any 1170 intellectual property or other rights that might be claimed to 1171 pertain to the implementation or use of the technology described in 1172 this document or the extent to which any license under such rights 1173 might or might not be available; neither does it represent that it 1174 has made any effort to identify any such rights. Information on the 1175 IETF's procedures with respect to rights in standards-track and 1176 standards-related documentation can be found in [15]. Copies of 1177 claims of rights made available for publication and any assurances of 1178 licenses to be made available, or the result of an attempt made to 1179 obtain a general license or permission for the use of such 1180 proprietary rights by implementers or users of this specification can 1181 be obtained from the IETF Secretariat. 1183 9. Acknowledgments 1185 The authors wish to thank Bill Anderson and Tim Dierks. 1187 Normative References 1189 [1] Bradner, S., "Key Words for Use in RFCs to Indicate Requirement 1190 Levels", RFC 2119, March 1997. 1192 [2] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC 1193 2246, January 1999. 1195 [3] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J. and 1196 T. Wright, "Transport Layer Security (TLS) Extensions", RFC 1197 3546, June 2003. 1199 [4] SECG, "Elliptic Curve Cryptography", SEC 1, 2000, . 1202 [5] IEEE, "Standard Specifications for Public Key Cryptography", 1203 IEEE 1363, 2000. 1205 [6] ANSI, "Public Key Cryptography For The Financial Services 1206 Industry: The Elliptic Curve Digital Signature Algorithm 1207 (ECDSA)", ANSI X9.62, 1998. 1209 [7] NIST, "Secure Hash Standard", FIPS 180-2, 2002. 1211 [8] NIST, "Digital Signature Standard", FIPS 186-2, 2000. 1213 [9] RSA Laboratories, "PKCS#1: RSA Encryption Standard version 1214 1.5", PKCS 1, November 1993. 1216 [10] SECG, "Recommended Elliptic Curve Domain Parameters", SEC 2, 1217 2000, . 1219 [11] Polk, T., Housley, R. and L. Bassham, "Algorithms and 1220 Identifiers for the Internet X.509 Public Key Infrastructure 1221 Certificate and Certificate Revocation List (CRL) Profile", RFC 1222 3279, April 2002. 1224 Informative References 1226 [12] Lenstra, A. and E. Verheul, "Selecting Cryptographic Key 1227 Sizes", Journal of Cryptology 14 (2001) 255-293, . 1230 [13] Freier, A., Karlton, P. and P. Kocher, "The SSL Protocol 1231 Version 3.0", November 1996, . 1234 [14] Chown, P., "Advanced Encryption Standard (AES) Ciphersuites for 1235 Transport Layer Security (TLS)", RFC 3268, June 2002. 1237 [15] Hovey, R. and S. Bradner, "The Organizations Involved in the 1238 IETF Standards Process", RFC 2028, BCP 11, October 1996. 1240 Authors' Addresses 1242 Vipul Gupta 1243 Sun Microsystems Laboratories 1244 2600 Casey Avenue 1245 MS UMTV29-235 1246 Mountain View, CA 94303 1247 USA 1249 Phone: +1 650 336 1681 1250 EMail: vipul.gupta@sun.com 1252 Simon Blake-Wilson 1253 Basic Commerce & Industries, Inc. 1254 96 Spandia Ave 1255 Unit 606 1256 Toronto, ON M6G 2T6 1257 Canada 1259 Phone: +1 416 214 5961 1260 EMail: sblakewilson@bcisse.com 1261 Bodo Moeller 1262 University of California, Berkeley 1263 EECS -- Computer Science Division 1264 513 Soda Hall 1265 Berkeley, CA 94720-1776 1266 USA 1268 EMail: bodo@openssl.org 1270 Chris Hawk 1271 Independent Consultant 1273 EMail: chris@socialeng.com 1275 Nelson Bolyard 1276 Netscape 1278 EMail: misterssl@aol.com 1280 Full Copyright Statement 1282 Copyright (C) The Internet Society (2004). 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