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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 7049 (Obsoleted by RFC 8949) ** Obsolete normative reference: RFC 8152 (Obsoleted by RFC 9052, RFC 9053) == Outdated reference: A later version (-46) exists of draft-ietf-ace-oauth-authz-21 Summary: 2 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ACE M. Jones 3 Internet-Draft Microsoft 4 Intended status: Standards Track L. Seitz 5 Expires: March 21, 2020 RISE SICS 6 G. Selander 7 Ericsson AB 8 S. Erdtman 9 Spotify 10 H. Tschofenig 11 Arm Ltd. 12 September 18, 2019 14 Proof-of-Possession Key Semantics for CBOR Web Tokens (CWTs) 15 draft-ietf-ace-cwt-proof-of-possession-07 17 Abstract 19 This specification describes how to declare in a CBOR Web Token (CWT) 20 that the presenter of the CWT possesses a particular proof-of- 21 possession key. Being able to prove possession of a key is also 22 sometimes described as being the holder-of-key. This specification 23 provides equivalent functionality to "Proof-of-Possession Key 24 Semantics for JSON Web Tokens (JWTs)" (RFC 7800) but using CBOR and 25 CWTs rather than JSON and JWTs. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at https://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on March 21, 2020. 44 Copyright Notice 46 Copyright (c) 2019 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (https://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 62 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 63 3. Representations for Proof-of-Possession Keys . . . . . . . . 3 64 3.1. Confirmation Claim . . . . . . . . . . . . . . . . . . . 4 65 3.2. Representation of an Asymmetric Proof-of-Possession Key . 5 66 3.3. Representation of an Encrypted Symmetric Proof-of- 67 Possession Key . . . . . . . . . . . . . . . . . . . . . 5 68 3.4. Representation of a Key ID for a Proof-of-Possession Key 6 69 3.5. Specifics Intentionally Not Specified . . . . . . . . . . 7 70 4. Security Considerations . . . . . . . . . . . . . . . . . . . 8 71 5. Privacy Considerations . . . . . . . . . . . . . . . . . . . 9 72 6. Operational Considerations . . . . . . . . . . . . . . . . . 9 73 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 74 7.1. CBOR Web Token Claims Registration . . . . . . . . . . . 10 75 7.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 10 76 7.2. CWT Confirmation Methods Registry . . . . . . . . . . . . 11 77 7.2.1. Registration Template . . . . . . . . . . . . . . . . 11 78 7.2.2. Initial Registry Contents . . . . . . . . . . . . . . 11 79 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 80 8.1. Normative References . . . . . . . . . . . . . . . . . . 12 81 8.2. Informative References . . . . . . . . . . . . . . . . . 13 82 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 14 83 Document History . . . . . . . . . . . . . . . . . . . . . . . . 14 84 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 86 1. Introduction 88 This specification describes how a CBOR Web Token (CWT) [RFC8392] can 89 declare that the presenter of the CWT possesses a particular proof- 90 of-possession (PoP) key. Proof of possession of a key is also 91 sometimes described as being the holder-of-key. This specification 92 provides equivalent functionality to "Proof-of-Possession Key 93 Semantics for JSON Web Tokens (JWTs)" [RFC7800] but using CBOR 94 [RFC7049] and CWTs [RFC8392] rather than JSON [RFC8259] and JWTs 95 [JWT]. 97 2. Terminology 99 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 100 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 101 "OPTIONAL" in this document are to be interpreted as described in BCP 102 14 [RFC2119] [RFC8174] when, and only when, they appear in all 103 capitals, as shown here. 105 This specification uses terms defined in the CBOR Web Token (CWT) 106 [RFC8392], CBOR Object Signing and Encryption (COSE) [RFC8152], and 107 Concise Binary Object Representation (CBOR) [RFC7049] specifications. 109 These terms are defined by this specification: 111 Issuer 112 Party that creates the CWT and binds the claims about the subject 113 to the proof-of-possession key. 115 Presenter 116 Party that proves possession of a private key (for asymmetric key 117 cryptography) or secret key (for symmetric key cryptography) to a 118 recipient of a CWT. 119 In the context of OAuth, this party is also called the OAuth 120 Client. 122 Recipient 123 Party that receives the CWT containing the proof-of-possession key 124 information from the presenter. 125 In the context of OAuth, this party is also called the OAuth 126 Resource Server. 128 This specification provides examples in CBOR extended diagnostic 129 notation, as defined in Appendix G of [RFC8610]. The examples 130 include line breaks for readability. 132 3. Representations for Proof-of-Possession Keys 134 By including a "cnf" (confirmation) claim in a CWT, the issuer of the 135 CWT declares that the presenter possesses a particular key and that 136 the recipient can cryptographically confirm that the presenter has 137 possession of that key. The value of the "cnf" claim is a CBOR map 138 and the members of that map identify the proof-of-possession key. 140 The presenter can be identified in one of several ways by the CWT, 141 depending upon the application requirements. For instance, some 142 applications may use the CWT "sub" (subject) claim [RFC8392], to 143 identify the presenter. Other applications may use the "iss" claim 144 to identify the presenter. In some applications, the subject 145 identifier might be relative to the issuer identified by the "iss" 146 (issuer) claim [RFC8392]. The actual mechanism used is dependent 147 upon the application. The case in which the presenter is the subject 148 of the CWT is analogous to Security Assertion Markup Language (SAML) 149 2.0 [OASIS.saml-core-2.0-os] SubjectConfirmation usage. 151 3.1. Confirmation Claim 153 The "cnf" claim in the CWT is used to carry confirmation methods. 154 Some of them use proof-of-possession keys while others do not. This 155 design is analogous to the SAML 2.0 [OASIS.saml-core-2.0-os] 156 SubjectConfirmation element in which a number of different subject 157 confirmation methods can be included (including proof-of-possession 158 key information). 160 The set of confirmation members that a CWT must contain to be 161 considered valid is context dependent and is outside the scope of 162 this specification. Specific applications of CWTs will require 163 implementations to understand and process some confirmation members 164 in particular ways. However, in the absence of such requirements, 165 all confirmation members that are not understood by implementations 166 MUST be ignored. 168 This specification establishes the IANA "CWT Confirmation Methods" 169 registry for these members in Section 7.2 and registers the members 170 defined by this specification. Other specifications can register 171 other members used for confirmation, including other members for 172 conveying proof-of-possession keys using different key 173 representations. 175 The "cnf" claim value MUST represent only a single proof-of- 176 possession key. At most one of the "COSE_Key" and 177 "Encrypted_COSE_Key" confirmation values defined in Figure 1 may be 178 present. Note that if an application needs to represent multiple 179 proof-of-possession keys in the same CWT, one way for it to achieve 180 this is to use other claim names, in addition to "cnf", to hold the 181 additional proof-of-possession key information. These claims could 182 use the same syntax and semantics as the "cnf" claim. Those claims 183 would be defined by applications or other specifications and could be 184 registered in the IANA "CBOR Web Token Claims" registry 185 [IANA.CWT.Claims]. 187 /--------------------+-----+-------------------------------\ 188 | Name | Key | Value type | 189 |--------------------+-----+-------------------------------| 190 | COSE_Key | 1 | COSE_Key | 191 | Encrypted_COSE_Key | 2 | COSE_Encrypt or COSE_Encrypt0 | 192 | kid | 3 | binary string | 193 \--------------------+-----+-------------------------------/ 195 Figure 1: Summary of the cnf names, keys, and value types 197 3.2. Representation of an Asymmetric Proof-of-Possession Key 199 When the key held by the presenter is an asymmetric private key, the 200 "COSE_Key" member is a COSE_Key [RFC8152] representing the 201 corresponding asymmetric public key. The following example 202 demonstrates such a declaration in the CWT Claims Set of a CWT: 204 { 205 /iss/ 1 : "coaps://server.example.com", 206 /aud/ 3 : "coaps://client.example.org", 207 /exp/ 4 : 1879067471, 208 /cnf/ 8 :{ 209 /COSE_Key/ 1 :{ 210 /kty/ 1 : /EC2/ 2, 211 /crv/ -1 : /P-256/ 1, 212 /x/ -2 : h'd7cc072de2205bdc1537a543d53c60a6acb62eccd890c7fa27c9 213 e354089bbe13', 214 /y/ -3 : h'f95e1d4b851a2cc80fff87d8e23f22afb725d535e515d020731e 215 79a3b4e47120' 216 } 217 } 218 } 220 The COSE_Key MUST contain the required key members for a COSE_Key of 221 that key type and MAY contain other COSE_Key members, including the 222 "kid" (Key ID) member. 224 The "COSE_Key" member MAY also be used for a COSE_Key representing a 225 symmetric key, provided that the CWT is encrypted so that the key is 226 not revealed to unintended parties. The means of encrypting a CWT is 227 explained in [RFC8392]. If the CWT is not encrypted, the symmetric 228 key MUST be encrypted as described in Section 3.3. 230 3.3. Representation of an Encrypted Symmetric Proof-of-Possession Key 232 When the key held by the presenter is a symmetric key, the 233 "Encrypted_COSE_Key" member is an encrypted COSE_Key [RFC8152] 234 representing the symmetric key encrypted to a key known to the 235 recipient using COSE_Encrypt or COSE_Encrypt0. 237 The following example illustrates a symmetric key that could 238 subsequently be encrypted for use in the "Encrypted_COSE_Key" member: 240 { 241 /kty/ 1 : /Symmetric/ 4, 242 /alg/ 3 : /HMAC256//256/ 5, 243 /k/ -1 : h'6684523ab17337f173500e5728c628547cb37df 244 e68449c65f885d1b73b49eae1' 245 } 247 The COSE_Key representation is used as the plaintext when encrypting 248 the key. 250 The following example CWT Claims Set of a CWT illustrates the use of 251 an encrypted symmetric key as the "Encrypted_COSE_Key" member value: 253 { 254 /iss/ 1 : "coaps://server.example.com", 255 /sub/ 2 : "24400320", 256 /aud/ 3: "s6BhdRkqt3", 257 /exp/ 4 : 1311281970, 258 /iat/ 5 : 1311280970, 259 /cnf/ 8 : { 260 /Encrypted_COSE_Key/ 2 : [ 261 /protected header/ h'A1010A' /{ \alg\ 1:10 \AES-CCM-16-64-128\}/, 262 /unprotected header/ { / iv / 5: h'636898994FF0EC7BFCF6D3F95B'}, 263 /ciphertext/ h'0573318A3573EB983E55A7C2F06CADD0796C9E584F1D0E3E 264 A8C5B052592A8B2694BE9654F0431F38D5BBC8049FA7F13F' 265 ] 266 } 267 } 269 The example above was generated with the key: 271 h'6162630405060708090a0b0c0d0e0f10' 273 3.4. Representation of a Key ID for a Proof-of-Possession Key 275 The proof-of-possession key can also be identified using a Key ID 276 instead of communicating the actual key, provided the recipient is 277 able to obtain the identified key using the Key ID. In this case, 278 the issuer of a CWT declares that the presenter possesses a 279 particular key and that the recipient can cryptographically confirm 280 proof of possession of the key by the presenter by including a "cnf" 281 claim in the CWT whose value is a CBOR map with the CBOR map 282 containing a "kid" member identifying the key. 284 The following example demonstrates such a declaration in the CWT 285 Claims Set of a CWT: 287 { 288 /iss/ 1 : "coaps://as.example.com", 289 /aud/ 3 : "coaps://resource.example.org", 290 /exp/ 4 : 1361398824, 291 /cnf/ 8 : { 292 /kid/ 3 : h'dfd1aa976d8d4575a0fe34b96de2bfad' 293 } 294 } 296 The content of the "kid" value is application specific. For 297 instance, some applications may choose to use a cryptographic hash of 298 the public key value as the "kid" value. 300 Note that the use of a Key ID to identify a proof-of-possession key 301 needs to be carefully circumscribed, as described below and in 302 Section 6. In cases where the Key ID is not a cryptographic value 303 derived from the key or where not all of the parties involved are 304 validating the cryptographic derivation, implementers should expect 305 collisions, where different keys are assigned the same Key ID. 306 Recipients of a CWT with a PoP key linked through only a Key ID 307 should be prepared to handle such situations. 309 In the world of constrained Internet of Things (IoT) devices, there 310 is frequently a restriction on the size of Key IDs, either because of 311 table constraints or a desire to keep message sizes small. 313 3.5. Specifics Intentionally Not Specified 315 Proof of possession is often demonstrated by having the presenter 316 sign a value determined by the recipient using the key possessed by 317 the presenter. This value is sometimes called a "nonce" or a 318 "challenge". There are, however, also other means to demonstrate 319 freshness of the exchange and to link the proof-of-possession key to 320 the participating parties, as demonstrated by various authentication 321 and key exchange protocols. 323 The means of communicating the nonce and the nature of its contents 324 are intentionally not described in this specification, as different 325 protocols will communicate this information in different ways. 326 Likewise, the means of communicating the signed nonce is also not 327 specified, as this is also protocol specific. 329 Note that other means of proving possession of the key exist, which 330 could be used in conjunction with a CWT's confirmation key. 331 Applications making use of such alternate means are encouraged to 332 register them in the IANA "CWT Confirmation Methods" registry 333 established in Section 7.2. 335 4. Security Considerations 337 All the security considerations that are discussed in [RFC8392] also 338 apply here. In addition, proof of possession introduces its own 339 unique security issues. Possessing a key is only valuable if it is 340 kept secret. Appropriate means must be used to ensure that 341 unintended parties do not learn private key or symmetric key values. 343 Applications utilizing proof of possession SHOULD also utilize 344 audience restriction, as described in Section 4.1.3 of [JWT], as it 345 provides additional protections. Audience restriction can be used by 346 recipients to reject messages intended for different recipients. 348 A recipient might not understand the "cnf" claim. Applications that 349 use proof-of-possession keys in CWTs with the "cnf" claim MUST ensure 350 that the parts of this specification that they use are implemented by 351 the intended recipient. 353 CBOR Web Tokens with proof-of-possession keys are used in context of 354 an architecture, such as the ACE OAuth Framework 355 [I-D.ietf-ace-oauth-authz], in which protocols are used by a 356 presenter to request these tokens and to subsequently use them with 357 recipients. Proof of possession only provides the intended security 358 gains when the proof is known to be current and not subject to replay 359 attacks; security protocols using mechanisms such as nonces and 360 timestamps can be used to avoid the risk of replay when performing 361 proof of possession for a token. Note that a discussion of the 362 architecture or specific protocols that CWT proof-of-possession 363 tokens are used with is beyond the scope of this specification. 365 As is the case with other information included in a CWT, it is 366 necessary to apply data origin authentication and integrity 367 protection (via a keyed message digest or a digital signature). Data 368 origin authentication ensures that the recipient of the CWT learns 369 about the entity that created the CWT since this will be important 370 for any policy decisions. Integrity protection prevents an adversary 371 from changing any elements conveyed within the CWT payload. Special 372 care has to be applied when carrying symmetric keys inside the CWT 373 since those not only require integrity protection but also 374 confidentiality protection (e.g., either by encrypting the "cnf" 375 element, as specified in Section 3.3, or by encrypting the whole CWT, 376 as specified in [RFC8392]). 378 As described in Section 6 (Key Identification) and Appendix D (Notes 379 on Key Selection) of [JWS], it is important to make explicit trust 380 decisions about the keys. Proof-of-possession signatures made with 381 keys not meeting the application's trust criteria MUST NOT be relied 382 upon. 384 5. Privacy Considerations 386 A proof-of-possession key can be used as a correlation handle if the 387 same key is used on multiple occasions. Thus, for privacy reasons, 388 it is recommended that different proof-of-possession keys be used 389 when interacting with different parties. 391 6. Operational Considerations 393 The use of CWTs with proof-of-possession keys requires additional 394 information to be shared between the involved parties in order to 395 ensure correct processing. The recipient needs to be able to use 396 credentials to verify the authenticity and integrity of the CWT. 397 Furthermore, the recipient may need to be able to decrypt either the 398 whole CWT or the encrypted parts thereof (see Section 3.3). This 399 requires the recipient to know information about the issuer. 400 Likewise, there needs to be agreement between the issuer and the 401 recipient about the claims being used (which is also true of CWTs in 402 general). 404 When an issuer creates a CWT containing a Key ID claim, it needs to 405 make sure that it does not issue another CWT with different claims 406 containing the same Key ID within the lifetime of the CWTs, unless 407 intentionally desired. Failure to do so may allow one party to 408 impersonate another party, with the potential to gain additional 409 privileges. A case where such reuse of a Key ID would be intentional 410 is when a presenter obtains a CWT with different claims (e.g., 411 extended scope) for the same recipient, but wants to continue using 412 an existing security association (e.g., a DTLS session) bound to the 413 key identified by the Key ID. Likewise, if PoP keys are used for 414 multiple different kinds of CWTs in an application and the PoP keys 415 are identified by Key IDs, care must be taken to keep the keys for 416 the different kinds of CWTs segregated so that an attacker cannot 417 cause the wrong PoP key to be used by using a valid Key ID for the 418 wrong kind of CWT. Using an audience restriction for the CWT would 419 be one strategy to mitigate this risk. 421 7. IANA Considerations 423 The following registration procedure is used for all the registries 424 established by this specification. 426 Values are registered on a Specification Required [RFC8126] basis 427 after a three-week review period on the cwt-reg-review@ietf.org 428 mailing list, on the advice of one or more Designated Experts. 429 However, to allow for the allocation of values prior to publication, 430 the Designated Experts may approve registration once they are 431 satisfied that such a specification will be published. [[ Note to 432 the RFC Editor: The name of the mailing list should be determined in 433 consultation with the IESG and IANA. Suggested name: cwt-reg- 434 review@ietf.org. ]] 436 Registration requests sent to the mailing list for review should use 437 an appropriate subject (e.g., "Request to Register CWT Confirmation 438 Method: example"). Registration requests that are undetermined for a 439 period longer than 21 days can be brought to the IESG's attention 440 (using the iesg@ietf.org mailing list) for resolution. 442 Designated Experts should determine whether a registration request 443 contains enough information for the registry to be populated with the 444 new values and whether the proposed new functionality already exists. 445 In the case of an incomplete registration or an attempt to register 446 already existing functionality, the Designated Experts should ask for 447 corrections or reject the registration. 449 It is suggested that multiple Designated Experts be appointed who are 450 able to represent the perspectives of different applications using 451 this specification in order to enable broadly informed review of 452 registration decisions. In cases where a registration decision could 453 be perceived as creating a conflict of interest for a particular 454 Expert, that Expert should defer to the judgment of the other 455 Experts. 457 7.1. CBOR Web Token Claims Registration 459 This specification registers the "cnf" claim in the IANA "CBOR Web 460 Token Claims" registry [IANA.CWT.Claims] established by [RFC8392]. 462 7.1.1. Registry Contents 464 o Claim Name: "cnf" 465 o Claim Description: Confirmation 466 o JWT Claim Name: "cnf" 467 o Claim Key: TBD (maybe 8) 468 o Claim Value Type(s): map 469 o Change Controller: IESG 470 o Specification Document(s): Section 3.1 of [[ this document ]] 472 7.2. CWT Confirmation Methods Registry 474 This specification establishes the IANA "CWT Confirmation Methods" 475 registry for CWT "cnf" member values. The registry records the 476 confirmation method member and a reference to the specification that 477 defines it. 479 7.2.1. Registration Template 481 Confirmation Method Name: 482 The human-readable name requested (e.g., "kid"). 484 Confirmation Method Description: 485 Brief description of the confirmation method (e.g., "Key 486 Identifier"). 488 JWT Confirmation Method Name: 489 Claim Name of the equivalent JWT confirmation method value, as 490 registered in [IANA.JWT.Claims]. CWT claims should normally have 491 a corresponding JWT claim. If a corresponding JWT claim would not 492 make sense, the Designated Experts can choose to accept 493 registrations for which the JWT Claim Name is listed as "N/A". 495 Confirmation Key: 496 CBOR map key value for the confirmation method. 498 Confirmation Value Type(s): 499 CBOR types that can be used for the confirmation method value. 501 Change Controller: 502 For Standards Track RFCs, list the "IESG". For others, give the 503 name of the responsible party. 505 Specification Document(s): 506 Reference to the document or documents that specify the parameter, 507 preferably including URIs that can be used to retrieve copies of 508 the documents. An indication of the relevant sections may also be 509 included but is not required. Note that the Designated Experts 510 and IANA must be able to obtain copies of the specification 511 document(s) to perform their work. 513 7.2.2. Initial Registry Contents 515 o Confirmation Method Name: "COSE_Key" 516 o Confirmation Method Description: COSE_Key Representing Public Key 517 o JWT Confirmation Method Name: "jwk" 518 o Confirmation Key: 1 519 o Confirmation Value Type(s): COSE_Key structure 520 o Change Controller: IESG 521 o Specification Document(s): Section 3.2 of [[ this document ]] 523 o Confirmation Method Name: "Encrypted_COSE_Key" 524 o Confirmation Method Description: Encrypted COSE_Key 525 o JWT Confirmation Method Name: "jwe" 526 o Confirmation Key: 2 527 o Confirmation Value Type(s): COSE_Encrypt or COSE_Encrypt0 528 structure (with an optional corresponding COSE_Encrypt or 529 COSE_Encrypt0 tag) 530 o Change Controller: IESG 531 o Specification Document(s): Section 3.3 of [[ this document ]] 533 o Confirmation Method Name: "kid" 534 o Confirmation Method Description: Key Identifier 535 o JWT Confirmation Method Name: "kid" 536 o Confirmation Key: 3 537 o Confirmation Value Type(s): binary string 538 o Change Controller: IESG 539 o Specification Document(s): Section 3.4 of [[ this document ]] 541 8. References 543 8.1. Normative References 545 [IANA.CWT.Claims] 546 IANA, "CBOR Web Token Claims", 547 . 549 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 550 Requirement Levels", BCP 14, RFC 2119, 551 DOI 10.17487/RFC2119, March 1997, 552 . 554 [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object 555 Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, 556 October 2013, . 558 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 559 Writing an IANA Considerations Section in RFCs", BCP 26, 560 RFC 8126, DOI 10.17487/RFC8126, June 2017, 561 . 563 [RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)", 564 RFC 8152, DOI 10.17487/RFC8152, July 2017, 565 . 567 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 568 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 569 May 2017, . 571 [RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig, 572 "CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392, 573 May 2018, . 575 8.2. Informative References 577 [I-D.ietf-ace-oauth-authz] 578 Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and 579 H. Tschofenig, "Authentication and Authorization for 580 Constrained Environments (ACE) using the OAuth 2.0 581 Framework (ACE-OAuth)", draft-ietf-ace-oauth-authz-21 582 (work in progress), February 2019. 584 [IANA.JWT.Claims] 585 IANA, "JSON Web Token Claims", 586 . 588 [JWS] Jones, M., Bradley, J., and N. Sakimura, "JSON Web 589 Signature (JWS)", RFC 7515, May 2015, 590 . 592 [JWT] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token 593 (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, 594 . 596 [OASIS.saml-core-2.0-os] 597 Cantor, S., Kemp, J., Philpott, R., and E. Maler, 598 "Assertions and Protocol for the OASIS Security Assertion 599 Markup Language (SAML) V2.0", OASIS Standard saml-core- 600 2.0-os, March 2005, 601 . 603 [RFC7800] Jones, M., Bradley, J., and H. Tschofenig, "Proof-of- 604 Possession Key Semantics for JSON Web Tokens (JWTs)", 605 RFC 7800, DOI 10.17487/RFC7800, April 2016, 606 . 608 [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data 609 Interchange Format", STD 90, RFC 8259, 610 DOI 10.17487/RFC8259, December 2017, 611 . 613 [RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data 614 Definition Language (CDDL): A Notational Convention to 615 Express Concise Binary Object Representation (CBOR) and 616 JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610, 617 June 2019, . 619 Acknowledgements 621 Thanks to the following people for their reviews of the 622 specification: Roman Danyliw, Benjamin Kaduk, Michael Richardson, and 623 Jim Schaad. 625 Ludwig Seitz and Goeran Selander worked on this document as part of 626 the CelticPlus project CyberWI, with funding from Vinnova. 628 Document History 630 [[ to be removed by the RFC Editor before publication as an RFC ]] 632 -07 634 o Addressed Area Director review by Benjamin Kaduk. 636 -06 638 o Corrected nits identified by Roman Danyliw. 640 -05 642 o Added text suggested by Jim Schaad describing considerations when 643 using the Key ID confirmation method. 645 -04 647 o Addressed additional WGLC comments by Jim Schaad and Roman 648 Danyliw. 650 -03 652 o Addressed review comments by Jim Schaad, see https://www.ietf.org/ 653 mail-archive/web/ace/current/msg02798.html 655 o Removed unnecessary sentence in the introduction regarding the use 656 any strings that could be case-sensitive. 658 o Clarified the terms Presenter and Recipient. 660 o Clarified text about the confirmation claim. 662 -02 664 o Changed "typically" to "often" when describing ways of performing 665 proof of possession. 667 o Changed b64 to hex encoding in an example. 669 o Changed to using the RFC 8174 boilerplate instead of the RFC 2119 670 boilerplate. 672 -01 674 o Now uses CBOR diagnostic notation for the examples. 676 o Added a table summarizing the "cnf" names, keys, and value types. 678 o Addressed some of Jim Schaad's feedback on -00. 680 -00 682 o Created the initial working group draft from draft-jones-ace-cwt- 683 proof-of-possession-01. 685 Authors' Addresses 687 Michael B. Jones 688 Microsoft 690 Email: mbj@microsoft.com 691 URI: http://self-issued.info/ 693 Ludwig Seitz 694 RISE SICS 695 Scheelevaegen 17 696 Lund 223 70 697 Sweden 699 Email: ludwig@ri.se 701 Goeran Selander 702 Ericsson AB 703 Faeroegatan 6 704 Kista 164 80 705 Sweden 707 Email: goran.selander@ericsson.com 708 Samuel Erdtman 709 Spotify 711 Email: erdtman@spotify.com 713 Hannes Tschofenig 714 Arm Ltd. 715 Hall in Tirol 6060 716 Austria 718 Email: Hannes.Tschofenig@arm.com