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Housley 3 Intended status: Standards Track Vigil Security 4 Expires: 10 October 2017 10 April 2017 6 Use of the Elliptic Curve Diffie-Hellman Key Agreement Algorithm 7 with X25519 and X448 in the Cryptographic Message Syntax (CMS) 9 11 Abstract 13 This document describes the conventions for using Elliptic Curve 14 Diffie-Hellman (ECDH) key agreement algorithm using curve25519 and 15 curve448 in the Cryptographic Message Syntax (CMS). 17 Status of This Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at http://datatracker.ietf.org/drafts/current/. 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 This Internet-Draft will expire on 10 October 2017. 34 Copyright Notice 36 Copyright (c) 2017 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (http://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 1. Introduction 51 This document describes the conventions for using Elliptic Curve 52 Diffie-Hellman (ECDH) key agreement using curve25519 and curve448 53 [CURVES] in the Cryptographic Message Syntax (CMS) [CMS]. Key 54 agreement is supported in three CMS content types: the enveloped-data 55 content type [CMS], authenticated-data content type [CMS], and the 56 authenticated-enveloped-data content type [AUTHENV]. 58 The conventions for using some Elliptic Curve Cryptography (ECC) 59 algorithms in CMS are described in [CMSECC]. These conventions cover 60 the use of ECDH with some curves other than curve25519 and curve448 61 [CURVES]. Those other curves are not deprecated, but support for 62 curve25519 and curve448 is encouraged. 64 Using curve25519 with Diffie-Hellman key agreement is referred to as 65 X25519. Using curve448 with Diffie-Hellman key agreement is referred 66 to as X448. 68 1.1. Terminology 70 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 71 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 72 document are to be interpreted as described in RFC 2119 [STDWORDS]. 74 1.2. ASN.1 76 CMS values are generated using ASN.1 [X680], which uses the Basic 77 Encoding Rules (BER) and the Distinguished Encoding Rules (DER) 78 [X690]. 80 2. Key Agreement 82 In 1976, Diffie and Hellman described a means for two parties to 83 agree upon a shared secret value in manner that prevents 84 eavesdroppers from learning the shared secret value [DH1976]. This 85 secret may then be converted into pairwise symmetric keying material 86 for use with other cryptographic algorithms. Over the years, many 87 variants of this fundamental technique have been developed. This 88 document describes the conventions for using Ephemeral-Static 89 Elliptic Curve Diffie-Hellman (ECDH) key agreement using X25519 and 90 X448 [CURVES]. 92 The originator uses an ephemeral public/private key pair that is 93 generated on the same elliptic curve as the public key of the 94 recipient. The ephemeral key pair is used for a single CMS protected 95 content type, and then it is discarded. The originator obtains the 96 recipient's static public key from the recipient's certificate 97 [PROFILE]. 99 X25519 is described in Section 6.1 of [CURVES], and X448 is described 100 in Section 6.2 of [CURVES]. Since curve25519 and curve448 have 101 cofactors of 8 and 4, respectively, an input point of small order 102 will eliminate any contribution from the other party's private key. 103 As described in Section 7 of [CURVES], implementations SHOULD detect 104 this situation by checking for the all-zero output. 106 In [CURVES], the shared secret value that is produced by ECDH is 107 called K. (In some other specifications, the shared secret value is 108 called Z.) A key derivation function (KDF) is used to produce a 109 pairwise key-encryption key from the shared secret value (K), the 110 length of the key-encryption key, and the DER-encoded ECC-CMS- 111 SharedInfo structure [CMSECC]. 113 The ECC-CMS-SharedInfo definition from [CMSECC] is repeated here for 114 convenience. 116 ECC-CMS-SharedInfo ::= SEQUENCE { 117 keyInfo AlgorithmIdentifier, 118 entityUInfo [0] EXPLICIT OCTET STRING OPTIONAL, 119 suppPubInfo [2] EXPLICIT OCTET STRING } 121 The ECC-CMS-SharedInfo keyInfo field contains the object identifier 122 of the key-encryption algorithm and associated parameters. This 123 algorithm will be used to wrap the content-encryption key. For 124 example, the AES Key Wrap algorithm [AESKW] does not need parameters, 125 so the algorithm identifier parameters are absent. 127 The ECC-CMS-SharedInfo entityUInfo field optionally contains 128 additional keying material supplied by the sending agent. Note that 129 [CMS] requires implementations to accept a KeyAgreeRecipientInfo 130 SEQUENCE that includes the ukm field. If the ukm field is present, 131 the ukm is placed in the entityUInfo field. The ukm value need not 132 be longer than the key-encryption key that will be produced by the 133 KDF. When present, the ukm ensures that a different key-encryption 134 key is generated, even when the originator ephemeral private key is 135 improperly used more than once. 137 The ECC-CMS-SharedInfo suppPubInfo field contains the length of the 138 generated key-encryption key, in bits, represented as a 32-bit number 139 in network byte order. For example, the key length for AES-256 [AES] 140 would be 0x00000100. 142 2.1. ANSI-X9.63-KDF 144 The ANSI-X9.63-KDF key derivation function is a simple construct 145 based on a one-way hash function described in ANS X9.63 [X963]. This 146 KDF is also described in Section 3.6.1 of [SEC1]. 148 Three values are concatenated to produce the input string to the KDF: 149 1. The shared secret value generated by ECDH, K. 150 2. The iteration counter, starting with one, as described below. 151 3. The DER-encoded ECC-CMS-SharedInfo structure. 153 To generate a key-encryption key (KEK), the KDF generates one or more 154 KM blocks, with the counter starting at 0x00000001, and incrementing 155 the counter for each subsequent KM block until enough material has 156 been generated. The 32-bit counter is represented in network byte 157 order. The KM blocks are concatenated left to right, and then the 158 leftmost portion of the result is used as the pairwise key-encryption 159 key, KEK: 161 KM(i) = Hash(K || INT32(counter=i) || DER(ECC-CMS-SharedInfo)) 163 KEK = KM(counter=1) || KM(counter=2) ... 165 2.2. HKDF 167 The HMAC-based Extract-and-Expand Key Derivation Function (HKDF) is a 168 robust construct based on a one-way hash function described in RFC 169 5869 [HKDF]. HKDF is comprised of two steps: HKDF-Extract followed 170 by HKDF-Expand. 172 Three values are used as inputs to the HKDF: 173 1. The shared secret value generated by ECDH, K. 174 2. The length in octets of the keying data to be generated. 175 3. The DER-encoded ECC-CMS-SharedInfo structure. 177 The ECC-CMS-SharedInfo structure optionally includes the ukm. If the 178 ukm is present, the ukm is also used as the HKDF salt. 180 The length of the generated key-encryption key is used two places, 181 once in bits, and once in octets. The ECC-CMS-SharedInfo structure 182 includes the length of the generated key-encryption key in bits. The 183 HKDF-Expand function takes an argument for the length of the 184 generated key-encryption key in octets. 186 In summary, to produce the pairwise key-encryption key, KEK: 188 if ukm is provided, then salt = ukm, else salt = zero 189 PRK = HKDF-Extract(salt, K) 191 KEK = HKDF-Expand(PRK, DER(ECC-CMS-SharedInfo), SizeInOctets(KEK)) 193 3. Enveloped-data Conventions 195 The CMS enveloped-data content type [CMS] consists of an encrypted 196 content and wrapped content-encryption keys for one or more 197 recipients. The ECDH key agreement algorithm is used to generate a 198 pairwise key-encryption key between the originator and a particular 199 recipient. Then, the key-encryption key is used to wrap the content- 200 encryption key for that recipient. When there is more than one 201 recipient, the same content-encryption key MUST be wrapped for each 202 of them. 204 A compliant implementation MUST meet the requirements for 205 constructing an enveloped-data content type in Section 6 of [CMS]. 207 A content-encryption key MUST be randomly generated for each instance 208 of an enveloped-data content type. The content-encryption key is 209 used to encrypt the content. 211 3.1. EnvelopedData Fields 213 The enveloped-data content type is ASN.1 encoded using the 214 EnvelopedData syntax. The fields of the EnvelopedData syntax MUST be 215 populated as described in [CMS]; for the recipients that use X25519 216 or X448 the RecipientInfo kari choice MUST be used. 218 3.2. KeyAgreeRecipientInfo Fields 220 The fields of the KeyAgreeRecipientInfo syntax MUST be populated as 221 described in this section when X25519 or X448 is employed for one or 222 more recipients. 224 The KeyAgreeRecipientInfo version MUST be 3. 226 The KeyAgreeRecipientInfo originator provides three alternatives for 227 identifying the originator's public key, and the originatorKey 228 alternative MUST be used. The originatorKey MUST contain an 229 ephemeral key for the originator. The originatorKey algorithm field 230 MUST contain the id-X25519 or the id-X448 object identifier. The 231 originator's ephemeral public key MUST be encoded as an OCTET STRING. 233 The object identifiers for X25519 and X448 have been assigned in 235 [ID.curdle-pkix]. They are repeated below for convenience. 237 When using X25519, the public key contains exactly 32 octets, and the 238 id-X25519 object identifier is used: 240 id-X25519 OBJECT IDENTIFIER ::= { 1 3 101 110 } 242 When using X448, the public key contains exactly 56 octets, and the 243 id-X448 object identifier is used: 245 id-X448 OBJECT IDENTIFIER ::= { 1 3 101 111 } 247 KeyAgreeRecipientInfo ukm is optional. Note that [CMS] requires 248 implementations to accept a KeyAgreeRecipientInfo SEQUENCE that 249 includes the ukm field. If present, the ukm is placed in the 250 entityUInfo field of the ECC-CMS-SharedInfo as input to the KDF. The 251 ukm value need not be longer than the key-encryption key produced by 252 the KDF. 254 KeyAgreeRecipientInfo keyEncryptionAlgorithm MUST contain the object 255 identifier of the key-encryption algorithm that will be used to wrap 256 the content-encryption key. The conventions for using AES-128, 257 AES-192, and AES-256 in the key wrap mode are specified in [CMSAES]. 259 KeyAgreeRecipientInfo recipientEncryptedKeys includes a recipient 260 identifier and encrypted key for one or more recipients. The 261 RecipientEncryptedKey KeyAgreeRecipientIdentifier MUST contain either 262 the issuerAndSerialNumber identifying the recipient's certificate or 263 the RecipientKeyIdentifier containing the subject key identifier from 264 the recipient's certificate. In both cases, the recipient's 265 certificate contains the recipient's static X25519 or X448 public 266 key. RecipientEncryptedKey EncryptedKey MUST contain the content- 267 encryption key encrypted with the pairwise key-encryption key using 268 the algorithm specified by the KeyWrapAlgorithm. 270 4. Authenticated-data Conventions 272 The CMS authenticated-data content type [CMS] consists an 273 authenticated content, a message authentication code (MAC), and 274 encrypted authentication keys for one or more recipients. The ECDH 275 key agreement algorithm is used to generate a pairwise key-encryption 276 key between the originator and a particular recipient. Then, the 277 key-encryption key is used to wrap the authentication key for that 278 recipient. When there is more than one recipient, the same 279 authentication key MUST be wrapped for each of them. 281 A compliant implementation MUST meet the requirements for 282 constructing an authenticated-data content type in Section 9 of 283 [CMS]. 285 A authentication key MUST be randomly generated for each instance of 286 an authenticated-data content type. The authentication key is used 287 to compute the MAC over the content. 289 4.1. AuthenticatedData Fields 291 The authenticated-data content type is ASN.1 encoded using the 292 AuthenticatedData syntax. The fields of the AuthenticatedData syntax 293 MUST be populated as described in [CMS]; for the recipients that use 294 X25519 or X448 the RecipientInfo kari choice MUST be used. 296 4.2. KeyAgreeRecipientInfo Fields 298 The fields of the KeyAgreeRecipientInfo syntax MUST be populated as 299 described in Section 3.2 of this document. 301 5. Authenticated-Enveloped-data Conventions 303 The CMS authenticated-enveloped-data content type [AUTHENV] consists 304 of an authenticated and encrypted content and encrypted content- 305 authenticated-encryption keys for one or more recipients. The ECDH 306 key agreement algorithm is used to generate a pairwise key-encryption 307 key between the originator and a particular recipient. Then, the 308 key-encryption key is used to wrap the content-authenticated- 309 encryption key for that recipient. When there is more than one 310 recipient, the same content-authenticated-encryption key MUST be 311 wrapped for each of them. 313 A compliant implementation MUST meet the requirements for 314 constructing an authenticated-data content type in Section 2 of 315 [AUTHENV]. 317 A content-authenticated-encryption key MUST be randomly generated for 318 each instance of an authenticated-enveloped-data content type. The 319 content-authenticated-encryption key key is used to authenticate and 320 encrypt the content. 322 5.1. AuthEnvelopedData Fields 324 The authenticated-enveloped-data content type is ASN.1 encoded using 325 the AuthEnvelopedData syntax. The fields of the AuthEnvelopedData 326 syntax MUST be populated as described in [AUTHENV]; for the 327 recipients that use X25519 or X448 the RecipientInfo kari choice MUST 328 be used. 330 5.2. KeyAgreeRecipientInfo Fields 332 The fields of the KeyAgreeRecipientInfo syntax MUST be populated as 333 described in Section 3.2 of this document. 335 6. Certificate Conventions 337 RFC 5280 [PROFILE] specifies the profile for using X.509 Certificates 338 in Internet applications. A recipient static public key is needed 339 for X25519 or X448, and the originator obtains that public key from 340 the recipient's certificate. The conventions for carrying X25519 and 341 X448 public keys are specified in [ID.curdle-pkix]. 343 7. Key Agreement Algorithm Identifiers 345 The following object identifiers are assigned in [CMSECC] to indicate 346 ECDH with ANSI-X9.63-KDF using various one-way hash functions. These 347 are expected to be used as AlgorithmIdentifiers with a parameter that 348 specifies the key-encryption algorithm. These are repeated here for 349 convenience. 351 secg-scheme OBJECT IDENTIFIER ::= { 352 iso(1) identified-organization(3) certicom(132) schemes(1) } 354 dhSinglePass-stdDH-sha256kdf-scheme OBJECT IDENTIFIER ::= { 355 secg-scheme 11 1 } 357 dhSinglePass-stdDH-sha384kdf-scheme OBJECT IDENTIFIER ::= { 358 secg-scheme 11 2 } 360 dhSinglePass-stdDH-sha512kdf-scheme OBJECT IDENTIFIER ::= { 361 secg-scheme 11 3 } 363 The following object identifiers are assigned to indicate ECDH with 364 HKDF using various one-way hash functions. These are expected to be 365 used as AlgorithmIdentifiers with a parameter that specifies the 366 key-encryption algorithm. 368 smime-alg OBJECT IDENTIFIER ::= { 369 iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) 370 pkcs-9(9) smime(16) alg(3) } 372 dhSinglePass-stdDH-hkdf-sha256-scheme OBJECT IDENTIFIER ::= { 373 smime-alg TBD1 } 375 dhSinglePass-stdDH-hkdf-sha384-scheme OBJECT IDENTIFIER ::= { 376 smime-alg TBD2 } 378 dhSinglePass-stdDH-hkdf-sha512-scheme OBJECT IDENTIFIER ::= { 379 smime-alg TBD3 } 381 8. SMIMECapabilities Attribute Conventions 383 A sending agent MAY announce to other agents that it supports ECDH 384 key agreement using the SMIMECapabilities signed attribute in a 385 signed message [SMIME] or a certificate [CERTCAP]. Following the 386 pattern established in [CMSECC], the SMIMECapabilities associated 387 with ECDH carries a DER-encoded object identifier that identifies 388 support for ECDH in conjunction with a particular KDF, and it 389 includes a parameter that names the key wrap algorithm. 391 The following SMIMECapabilities values (in hexidecimal) from [CMSECC] 392 might be of interest to implementations that support X25519 and X448: 394 ECDH with ANSI-X9.63-KDF using SHA-256; uses AES-128 key wrap: 395 30 15 06 06 2B 81 04 01 0B 01 30 0B 06 09 60 86 48 01 65 03 04 396 01 05 398 ECDH with ANSI-X9.63-KDF using SHA-384; uses AES-128 key wrap: 399 30 15 06 06 2B 81 04 01 0B 02 30 0B 06 09 60 86 48 01 65 03 04 400 01 05 402 ECDH with ANSI-X9.63-KDF using SHA-512; uses AES-128 key wrap: 403 30 15 06 06 2B 81 04 01 0B 03 30 0B 06 09 60 86 48 01 65 03 04 404 01 05 406 ECDH with ANSI-X9.63-KDF using SHA-256; uses AES-256 key wrap: 407 30 15 06 06 2B 81 04 01 0B 01 30 0B 06 09 60 86 48 01 65 03 04 408 01 2D 410 ECDH with ANSI-X9.63-KDF using SHA-384; uses AES-256 key wrap: 411 30 15 06 06 2B 81 04 01 0B 02 30 0B 06 09 60 86 48 01 65 03 04 412 01 2D 414 ECDH with ANSI-X9.63-KDF using SHA-512; uses AES-256 key wrap: 415 30 15 06 06 2B 81 04 01 0B 03 30 0B 06 09 60 86 48 01 65 03 04 416 01 2D 418 The following SMIMECapabilities values (in hexidecimal) based on the 419 algorithm identifiers in Section 7 of this document might be of 420 interest to implementations that support X25519 and X448: 422 ECDH with HKDF using SHA-256; uses AES-128 key wrap: 423 TBD 425 ECDH with HKDF using SHA-384; uses AES-128 key wrap: 426 TBD 428 ECDH with HKDF using SHA-512; uses AES-128 key wrap: 429 TBD 431 ECDH with HKDF using SHA-256; uses AES-256 key wrap: 432 TBD 434 ECDH with HKDF using SHA-384; uses AES-256 key wrap: 435 TBD 437 ECDH with HKDF using SHA-512; uses AES-256 key wrap: 438 TBD 440 9. Security Considerations 442 Please consult the security considerations of [CMS] for security 443 considerations related to the enveloped-data content type and the 444 authenticated-data content type. 446 Please consult the security considerations of [AUTHENV] for security 447 considerations related to the authenticated-enveloped-data content 448 type. 450 Please consult the security considerations of [CURVES] for security 451 considerations related to the use of X25519 and X448. 453 The originator uses an ephemeral public/private key pair that is 454 generated on the same elliptic curve as the public key of the 455 recipient. The ephemeral key pair is used for a single CMS protected 456 content type, and then it is discarded. If the originator wants to 457 be able to decrypt the content (for enveloped-data and authenticated- 458 enveloped-data) or check the authentication (for authenticated-data), 459 then the originator needs to treat themselves as a recipient. 461 As specified in [CMS], implementations MUST support processing of the 462 KeyAgreeRecipientInfo ukm field; this ensures that interoperability 463 is not a concern whether the ukm is present or absent. The ukm is 464 placed in the entityUInfo field of the ECC-CMS-SharedInfo structure. 465 When present, the ukm ensures that a different key-encryption key is 466 generated, even when the originator ephemeral private key is 467 improperly used more than once. 469 10. IANA Considerations 471 One object identifier for the ASN.1 module in the Appendix needs to 472 be assigned in the SMI Security for S/MIME Module Identifiers 473 (1.2.840.113549.1.9.16.0) [IANA-MOD] registry: 475 id-mod-cms-ecdh-alg-2017 OBJECT IDENTIFIER ::= { 476 iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) 477 pkcs-9(9) smime(16) mod(0) TBD0 } 479 Three object identifiers for the Key Agreement Algorithm Identifiers 480 in Sections 7 need to be assigned in the SMI Security for S/MIME 481 Algorithms (1.2.840.113549.1.9.16.3) [IANA-ALG] registry: 483 smime-alg OBJECT IDENTIFIER ::= { 484 iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) 485 pkcs-9(9) smime(16) alg(3) } 487 dhSinglePass-stdDH-hkdf-sha256-scheme OBJECT IDENTIFIER ::= { 488 smime-alg TBD1 } 490 dhSinglePass-stdDH-hkdf-sha384-scheme OBJECT IDENTIFIER ::= { 491 smime-alg TBD2 } 493 dhSinglePass-stdDH-hkdf-sha512-scheme OBJECT IDENTIFIER ::= { 494 smime-alg TBD3 } 496 11. Normative References 498 [AUTHENV] Housley, R., "Cryptographic Message Syntax (CMS) 499 Authenticated-Enveloped-Data Content Type", RFC 5083, 500 November 2007. 502 [CERTCAP] Santesson, S., "X.509 Certificate Extension for 503 Secure/Multipurpose Internet Mail Extensions (S/MIME) 504 Capabilities", RFC 4262, December 2005. 506 [CMS] Housley, R., "Cryptographic Message Syntax (CMS)", RFC 507 5652, September 2009. 509 [CMSASN1] Hoffman, P., and J. Schaad, "New ASN.1 Modules for 510 Cryptographic Message Syntax (CMS) and S/MIME", RFC 5911, 511 June 2010. 513 [CMSECC] Turner, S., and D. Brown, "Use of Elliptic Curve 514 Cryptography (ECC) Algorithms in Cryptographic Message 515 Syntax (CMS)", RFC 5753, January 2010. 517 [CURVES] Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves 518 for Security", RFC 7748, January 2016. 520 [HKDF] Krawczyk, H., and P. Eronen, "HMAC-based Extract-and- 521 Expand Key Derivation Function (HKDF)", RFC 5869, May 522 2010. 524 [ID.curdle-pkix] 525 Josefsson, S., and J. Schaad, "Algorithm Identifiers for 526 Ed25519, Ed25519ph, Ed448, Ed448ph, X25519 and X448 for 527 use in the Internet X.509 Public Key Infrastructure", 528 15 August 2016, Work-in-progress. 530 [PKIXALG] Bassham, L., Polk, W., and R. Housley, "Algorithms and 531 Identifiers for the Internet X.509 Public Key 532 Infrastructure Certificate and Certificate Revocation List 533 (CRL) Profile", RFC 3279, April 2002. 535 [PKIXECC] Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk, 536 "Elliptic Curve Cryptography Subject Public Key 537 Information", RFC 5480, March 2009. 539 [PROFILE] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 540 Housley, R., and W. Polk, "Internet X.509 Public Key 541 Infrastructure Certificate and Certificate Revocation List 542 (CRL) Profile", RFC 5280, May 2008. 544 [SEC1] Standards for Efficient Cryptography Group, "SEC 1: 545 Elliptic Curve Cryptography", version 2.0, May 2009, 546 . 548 [SMIME] Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet 549 Mail Extensions (S/MIME) Version 3.2 Message 550 Specification", RFC 5751, January 2010. 552 [STDWORDS] Bradner, S., "Key words for use in RFCs to Indicate 553 Requirement Levels", BCP 14, RFC 2119, March 1997. 555 [X680] ITU-T, "Information technology -- Abstract Syntax Notation 556 One (ASN.1): Specification of basic notation", ITU-T 557 Recommendation X.680, 2015. 559 [X690] ITU-T, "Information technology -- ASN.1 encoding rules: 560 Specification of Basic Encoding Rules (BER), Canonical 561 Encoding Rules (CER) and Distinguished Encoding Rules 562 (DER)", ITU-T Recommendation X.690, 2015. 564 12. Informative References 566 [AES] National Institute of Standards and Technology. FIPS Pub 567 197: Advanced Encryption Standard (AES). 26 November 2001. 569 [AESKW] Schaad, J., and R. Housley, "Advanced Encryption Standard 570 (AES) Key Wrap Algorithm", RFC 3394, September 2002. 572 [CMSAES] Schaad, J., "Use of the Advanced Encryption Standard (AES) 573 Encryption Algorithm in Cryptographic Message Syntax 574 (CMS)", RFC 3565, July 2003. 576 [DH1976] Diffie, W., and M. E. Hellman, "New Directions in 577 Cryptography", IEEE Trans. on Info. Theory, Vol. IT-22, 578 Nov. 1976, pp. 644-654. 580 [IANA-ALG] https://www.iana.org/assignments/smi-numbers/ 581 smi-numbers.xhtml#security-smime-3. 583 [IANA-MOD] https://www.iana.org/assignments/smi-numbers/ 584 smi-numbers.xhtml#security-smime-0. 586 [X963] "Public-Key Cryptography for the Financial Services 587 Industry: Key Agreement and Key Transport Using Elliptic 588 Curve Cryptography", American National Standard 589 X9.63-2001, 2001. 591 Appendix: ASN.1 Module 593 CMSECDHAlgs-2017 594 { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) 595 smime(16) modules(0) id-mod-cms-ecdh-alg-2017(TBD0) } 597 DEFINITIONS IMPLICIT TAGS ::= 598 BEGIN 600 -- EXPORTS ALL 602 IMPORTS 604 KeyWrapAlgorithm 605 FROM CryptographicMessageSyntaxAlgorithms-2009 -- in [CMSASN1] 606 { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) 607 pkcs-9(9) smime(16) modules(0) id-mod-cmsalg-2001-02(37) } 609 KEY-AGREE, SMIME-CAPS 610 FROM AlgorithmInformation-2009 -- in [CMSASN1] 611 { iso(1) identified-organization(3) dod(6) internet(1) 612 security(5) mechanisms(5) pkix(7) id-mod(0) 613 id-mod-algorithmInformation-02(58) } 615 dhSinglePass-stdDH-sha256kdf-scheme, 616 dhSinglePass-stdDH-sha384kdf-scheme, 617 dhSinglePass-stdDH-sha512kdf-scheme, 618 kaa-dhSinglePass-stdDH-sha256kdf-scheme, 619 kaa-dhSinglePass-stdDH-sha384kdf-scheme, 620 kaa-dhSinglePass-stdDH-sha512kdf-scheme, 621 cap-kaa-dhSinglePass-stdDH-sha256kdf-scheme, 622 cap-kaa-dhSinglePass-stdDH-sha384kdf-scheme, 623 cap-kaa-dhSinglePass-stdDH-sha512kdf-scheme 624 FROM CMSECCAlgs-2009-02 -- in [CMSECC] 625 { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) 626 pkcs-9(9) smime(16) modules(0) 627 id-mod-cms-ecc-alg-2009-02(46) } 628 ; 630 -- 631 -- Object Identifiers 632 -- 634 smime-alg OBJECT IDENTIFIER ::= { 635 iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) 636 pkcs-9(9) smime(16) alg(3) } 638 dhSinglePass-stdDH-hkdf-sha256-scheme OBJECT IDENTIFIER ::= { 639 smime-alg TBD1 } 641 dhSinglePass-stdDH-hkdf-sha384-scheme OBJECT IDENTIFIER ::= { 642 smime-alg TBD2 } 644 dhSinglePass-stdDH-hkdf-sha512-scheme OBJECT IDENTIFIER ::= { 645 smime-alg TBD3 } 647 -- 648 -- Extend the Key Agreement Algorithms in [CMSECC] 649 -- 651 KeyAgreementAlgs KEY-AGREE ::= { ..., 652 kaa-dhSinglePass-stdDH-sha256kdf-scheme | 653 kaa-dhSinglePass-stdDH-sha384kdf-scheme | 654 kaa-dhSinglePass-stdDH-sha512kdf-scheme | 655 kaa-dhSinglePass-stdDH-hkdf-sha256-scheme | 656 kaa-dhSinglePass-stdDH-hkdf-sha384-scheme | 657 kaa-dhSinglePass-stdDH-hkdf-sha512-scheme } 659 kaa-dhSinglePass-stdDH-hkdf-sha256-scheme KEY-AGREE ::= { 660 IDENTIFIER dhSinglePass-stdDH-hkdf-sha256-scheme 661 PARAMS TYPE KeyWrapAlgorithm ARE required 662 UKM -- TYPE unencoded data -- ARE preferredPresent 663 SMIME-CAPS cap-kaa-dhSinglePass-stdDH-hkdf-sha256-scheme } 665 kaa-dhSinglePass-stdDH-hkdf-sha384-scheme KEY-AGREE ::= { 666 IDENTIFIER dhSinglePass-stdDH-hkdf-sha384-scheme 667 PARAMS TYPE KeyWrapAlgorithm ARE required 668 UKM -- TYPE unencoded data -- ARE preferredPresent 669 SMIME-CAPS cap-kaa-dhSinglePass-stdDH-hkdf-sha384-scheme } 671 kaa-dhSinglePass-stdDH-hkdf-sha512-scheme KEY-AGREE ::= { 672 IDENTIFIER dhSinglePass-stdDH-hkdf-sha512-scheme 673 PARAMS TYPE KeyWrapAlgorithm ARE required 674 UKM -- TYPE unencoded data -- ARE preferredPresent 675 SMIME-CAPS cap-kaa-dhSinglePass-stdDH-hkdf-sha512-scheme } 677 -- 678 -- Extend the S/MIME CAPS in [CMSECC] 679 -- 681 SMimeCAPS SMIME-CAPS ::= { ..., 682 kaa-dhSinglePass-stdDH-sha256kdf-scheme.&smimeCaps | 683 kaa-dhSinglePass-stdDH-sha384kdf-scheme.&smimeCaps | 684 kaa-dhSinglePass-stdDH-sha512kdf-scheme.&smimeCaps | 685 kaa-dhSinglePass-stdDH-hkdf-sha256-scheme.&smimeCaps | 686 kaa-dhSinglePass-stdDH-hkdf-sha384-scheme.&smimeCaps | 687 kaa-dhSinglePass-stdDH-hkdf-sha512-scheme.&smimeCaps } 689 cap-kaa-dhSinglePass-stdDH-hkdf-sha256-scheme SMIME-CAPS ::= { 690 TYPE KeyWrapAlgorithm 691 IDENTIFIED BY dhSinglePass-stdDH-hkdf-sha256-scheme } 693 cap-kaa-dhSinglePass-stdDH-hkdf-sha384-scheme SMIME-CAPS ::= { 694 TYPE KeyWrapAlgorithm 695 IDENTIFIED BY dhSinglePass-stdDH-hkdf-sha384-scheme} 697 cap-kaa-dhSinglePass-stdDH-hkdf-sha512-scheme SMIME-CAPS ::= { 698 TYPE KeyWrapAlgorithm 699 IDENTIFIED BY dhSinglePass-stdDH-hkdf-sha512-scheme } 701 END 703 Acknowledgements 705 Many thanks to Daniel Migault, Jim Schaad, Stefan Santesson, and Sean 706 Turner for their review and insightful suggestions. 708 Author's Address 710 Russ Housley 711 918 Spring Knoll Drive 712 Herndon, VA 20170 713 USA 714 housley@vigilsec.com