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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RFC 7049 (Obsoleted by RFC 8949) ** Obsolete normative reference: RFC 8152 (Obsoleted by RFC 9052, RFC 9053) == Outdated reference: A later version (-46) exists of draft-ietf-ace-oauth-authz-21 Summary: 2 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--).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: May 3, 2020 RISE SICS 6 G. Selander 7 Ericsson AB 8 S. Erdtman 9 Spotify 10 H. Tschofenig 11 Arm Ltd. 12 October 31, 2019 14 Proof-of-Possession Key Semantics for CBOR Web Tokens (CWTs) 15 draft-ietf-ace-cwt-proof-of-possession-11 17 Abstract 19 This specification describes how to declare in a CBOR Web Token (CWT) 20 (which is defined by RFC 8392) that the presenter of the CWT 21 possesses a particular proof-of-possession key. Being able to prove 22 possession of a key is also sometimes described as being the holder- 23 of-key. This specification provides equivalent functionality to 24 "Proof-of-Possession Key Semantics for JSON Web Tokens (JWTs)" (RFC 25 7800) but using Concise Binary Object Representation (CBOR) and CWTs 26 rather than JavaScript Object Notation (JSON) and JSON Web Tokens 27 (JWTs). 29 Status of This Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at https://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on May 3, 2020. 46 Copyright Notice 48 Copyright (c) 2019 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (https://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 64 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 65 3. Representations for Proof-of-Possession Keys . . . . . . . . 3 66 3.1. Confirmation Claim . . . . . . . . . . . . . . . . . . . 4 67 3.2. Representation of an Asymmetric Proof-of-Possession Key . 5 68 3.3. Representation of an Encrypted Symmetric Proof-of- 69 Possession Key . . . . . . . . . . . . . . . . . . . . . 6 70 3.4. Representation of a Key ID for a Proof-of-Possession Key 7 71 3.5. Specifics Intentionally Not Specified . . . . . . . . . . 8 72 4. Security Considerations . . . . . . . . . . . . . . . . . . . 8 73 5. Privacy Considerations . . . . . . . . . . . . . . . . . . . 9 74 6. Operational Considerations . . . . . . . . . . . . . . . . . 9 75 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 76 7.1. CBOR Web Token Claims Registration . . . . . . . . . . . 11 77 7.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 11 78 7.2. CWT Confirmation Methods Registry . . . . . . . . . . . . 11 79 7.2.1. Registration Template . . . . . . . . . . . . . . . . 11 80 7.2.2. Initial Registry Contents . . . . . . . . . . . . . . 12 81 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 82 8.1. Normative References . . . . . . . . . . . . . . . . . . 12 83 8.2. Informative References . . . . . . . . . . . . . . . . . 13 84 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 14 85 Document History . . . . . . . . . . . . . . . . . . . . . . . . 14 86 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 88 1. Introduction 90 This specification describes how a CBOR Web Token (CWT) [RFC8392] can 91 declare that the presenter of the CWT possesses a particular proof- 92 of-possession (PoP) key. Proof of possession of a key is also 93 sometimes described as being the holder-of-key. This specification 94 provides equivalent functionality to "Proof-of-Possession Key 95 Semantics for JSON Web Tokens (JWTs)" [RFC7800] but using Concise 96 Binary Object Representation (CBOR) [RFC7049] and CWTs [RFC8392] 97 rather than JavaScript Object Notation (JSON) [RFC8259] and JSON Web 98 Tokens (JWTs) [JWT]. 100 2. Terminology 102 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 103 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 104 "OPTIONAL" in this document are to be interpreted as described in BCP 105 14 [RFC2119] [RFC8174] when, and only when, they appear in all 106 capitals, as shown here. 108 This specification uses terms defined in the CBOR Web Token (CWT) 109 [RFC8392], CBOR Object Signing and Encryption (COSE) [RFC8152], and 110 Concise Binary Object Representation (CBOR) [RFC7049] specifications. 112 These terms are defined by this specification: 114 Issuer 115 Party that creates the CWT and binds the claims about the subject 116 to the proof-of-possession key. 118 Presenter 119 Party that proves possession of a private key (for asymmetric key 120 cryptography) or secret key (for symmetric key cryptography) to a 121 recipient of a CWT. 122 In the context of OAuth, this party is also called the OAuth 123 Client. 125 Recipient 126 Party that receives the CWT containing the proof-of-possession key 127 information from the presenter. 128 In the context of OAuth, this party is also called the OAuth 129 Resource Server. 131 This specification provides examples in CBOR extended diagnostic 132 notation, as defined in Appendix G of [RFC8610]. The examples 133 include line breaks for readability. 135 3. Representations for Proof-of-Possession Keys 137 By including a "cnf" (confirmation) claim in a CWT, the issuer of the 138 CWT declares that the presenter possesses a particular key and that 139 the recipient can cryptographically confirm that the presenter has 140 possession of that key. The value of the "cnf" claim is a CBOR map 141 (which is defined in Section 2.1 of [RFC7049]) and the members of 142 that map identify the proof-of-possession key. 144 The presenter can be identified in one of several ways by the CWT, 145 depending upon the application requirements. For instance, some 146 applications may use the CWT "sub" (subject) claim [RFC8392], to 147 identify the presenter. Other applications may use the "iss" 148 (issuer) claim [RFC8392] to identify the presenter. In some 149 applications, the subject identifier might be relative to the issuer 150 identified by the "iss" claim. The actual mechanism used is 151 dependent upon the application. The case in which the presenter is 152 the subject of the CWT is analogous to Security Assertion Markup 153 Language (SAML) 2.0 [OASIS.saml-core-2.0-os] SubjectConfirmation 154 usage. 156 3.1. Confirmation Claim 158 The "cnf" claim in the CWT is used to carry confirmation methods. 159 Some of them use proof-of-possession keys while others do not. This 160 design is analogous to the SAML 2.0 [OASIS.saml-core-2.0-os] 161 SubjectConfirmation element in which a number of different subject 162 confirmation methods can be included (including proof-of-possession 163 key information). 165 The set of confirmation members that a CWT must contain to be 166 considered valid is context dependent and is outside the scope of 167 this specification. Specific applications of CWTs will require 168 implementations to understand and process some confirmation members 169 in particular ways. However, in the absence of such requirements, 170 all confirmation members that are not understood by implementations 171 MUST be ignored. 173 This specification establishes the IANA "CWT Confirmation Methods" 174 registry for these members in Section 7.2 and registers the members 175 defined by this specification. Other specifications can register 176 other members used for confirmation, including other members for 177 conveying proof-of-possession keys using different key 178 representations. 180 The "cnf" claim value MUST represent only a single proof-of- 181 possession key. At most one of the "COSE_Key" and 182 "Encrypted_COSE_Key" confirmation values defined in Figure 1 may be 183 present. Note that if an application needs to represent multiple 184 proof-of-possession keys in the same CWT, one way for it to achieve 185 this is to use other claim names, in addition to "cnf", to hold the 186 additional proof-of-possession key information. These claims could 187 use the same syntax and semantics as the "cnf" claim. Those claims 188 would be defined by applications or other specifications and could be 189 registered in the IANA "CBOR Web Token Claims" registry 190 [IANA.CWT.Claims]. 192 /--------------------+-----+-------------------------------\ 193 | Name | Key | Value type | 194 |--------------------+-----+-------------------------------| 195 | COSE_Key | 1 | COSE_Key | 196 | Encrypted_COSE_Key | 2 | COSE_Encrypt or COSE_Encrypt0 | 197 | kid | 3 | binary string | 198 \--------------------+-----+-------------------------------/ 200 Figure 1: Summary of the cnf names, keys, and value types 202 3.2. Representation of an Asymmetric Proof-of-Possession Key 204 When the key held by the presenter is an asymmetric private key, the 205 "COSE_Key" member is a COSE_Key [RFC8152] representing the 206 corresponding asymmetric public key. The following example 207 demonstrates such a declaration in the CWT Claims Set of a CWT: 209 { 210 /iss/ 1 : "coaps://server.example.com", 211 /aud/ 3 : "coaps://client.example.org", 212 /exp/ 4 : 1879067471, 213 /cnf/ 8 :{ 214 /COSE_Key/ 1 :{ 215 /kty/ 1 : /EC2/ 2, 216 /crv/ -1 : /P-256/ 1, 217 /x/ -2 : h'd7cc072de2205bdc1537a543d53c60a6acb62eccd890c7fa27c9 218 e354089bbe13', 219 /y/ -3 : h'f95e1d4b851a2cc80fff87d8e23f22afb725d535e515d020731e 220 79a3b4e47120' 221 } 222 } 223 } 225 The COSE_Key MUST contain the required key members for a COSE_Key of 226 that key type and MAY contain other COSE_Key members, including the 227 "kid" (Key ID) member. 229 The "COSE_Key" member MAY also be used for a COSE_Key representing a 230 symmetric key, provided that the CWT is encrypted so that the key is 231 not revealed to unintended parties. The means of encrypting a CWT is 232 explained in [RFC8392]. If the CWT is not encrypted, the symmetric 233 key MUST be encrypted as described in Section 3.3. This procedure is 234 equivalent to the one defined in section 3.3 of [RFC7800]. 236 3.3. Representation of an Encrypted Symmetric Proof-of-Possession Key 238 When the key held by the presenter is a symmetric key, the 239 "Encrypted_COSE_Key" member is an encrypted COSE_Key [RFC8152] 240 representing the symmetric key encrypted to a key known to the 241 recipient using COSE_Encrypt or COSE_Encrypt0. 243 The following example illustrates a symmetric key that could 244 subsequently be encrypted for use in the "Encrypted_COSE_Key" member: 246 { 247 /kty/ 1 : /Symmetric/ 4, 248 /alg/ 3 : /HMAC 256-256/ 5, 249 /k/ -1 : h'6684523ab17337f173500e5728c628547cb37df 250 e68449c65f885d1b73b49eae1' 251 } 253 The COSE_Key representation is used as the plaintext when encrypting 254 the key. 256 The following example CWT Claims Set of a CWT illustrates the use of 257 an encrypted symmetric key as the "Encrypted_COSE_Key" member value: 259 { 260 /iss/ 1 : "coaps://server.example.com", 261 /sub/ 2 : "24400320", 262 /aud/ 3: "s6BhdRkqt3", 263 /exp/ 4 : 1311281970, 264 /iat/ 5 : 1311280970, 265 /cnf/ 8 : { 266 /Encrypted_COSE_Key/ 2 : [ 267 /protected header/ h'A1010A' /{ \alg\ 1:10 \AES-CCM-16-64-128\}/, 268 /unprotected header/ { / iv / 5: h'636898994FF0EC7BFCF6D3F95B'}, 269 /ciphertext/ h'0573318A3573EB983E55A7C2F06CADD0796C9E584F1D0E3E 270 A8C5B052592A8B2694BE9654F0431F38D5BBC8049FA7F13F' 271 ] 272 } 273 } 275 The example above was generated with the key: 277 h'6162630405060708090a0b0c0d0e0f10' 279 3.4. Representation of a Key ID for a Proof-of-Possession Key 281 The proof-of-possession key can also be identified using a Key ID 282 instead of communicating the actual key, provided the recipient is 283 able to obtain the identified key using the Key ID. In this case, 284 the issuer of a CWT declares that the presenter possesses a 285 particular key and that the recipient can cryptographically confirm 286 proof of possession of the key by the presenter by including a "cnf" 287 claim in the CWT whose value is a CBOR map with the CBOR map 288 containing a "kid" member identifying the key. 290 The following example demonstrates such a declaration in the CWT 291 Claims Set of a CWT: 293 { 294 /iss/ 1 : "coaps://as.example.com", 295 /aud/ 3 : "coaps://resource.example.org", 296 /exp/ 4 : 1361398824, 297 /cnf/ 8 : { 298 /kid/ 3 : h'dfd1aa976d8d4575a0fe34b96de2bfad' 299 } 300 } 302 The content of the "kid" value is application specific. For 303 instance, some applications may choose to use a cryptographic hash of 304 the public key value as the "kid" value. 306 Note that the use of a Key ID to identify a proof-of-possession key 307 needs to be carefully circumscribed, as described below and in 308 Section 6. In cases where the Key ID is not a cryptographic value 309 derived from the key or where not all of the parties involved are 310 validating the cryptographic derivation, implementers should expect 311 collisions, where different keys are assigned the same Key ID. 312 Recipients of a CWT with a PoP key linked through only a Key ID 313 should be prepared to handle such situations. 315 In the world of constrained Internet of Things (IoT) devices, there 316 is frequently a restriction on the size of Key IDs, either because of 317 table constraints or a desire to keep message sizes small. 319 Note that the value of a Key ID for a specific key is not necessarily 320 the same for different parties. When sending a COSE encrypted 321 message with a shared key, the Key ID may be different on both sides 322 of the conversation, with the appropriate one being included in the 323 message based on the recipient of the message. 325 3.5. Specifics Intentionally Not Specified 327 Proof of possession is often demonstrated by having the presenter 328 sign a value determined by the recipient using the key possessed by 329 the presenter. This value is sometimes called a "nonce" or a 330 "challenge". There are, however, also other means to demonstrate 331 freshness of the exchange and to link the proof-of-possession key to 332 the participating parties, as demonstrated by various authentication 333 and key exchange protocols. 335 The means of communicating the nonce and the nature of its contents 336 are intentionally not described in this specification, as different 337 protocols will communicate this information in different ways. 338 Likewise, the means of communicating the signed nonce is also not 339 specified, as this is also protocol specific. 341 Note that other means of proving possession of the key exist, which 342 could be used in conjunction with a CWT's confirmation key. 343 Applications making use of such alternate means are encouraged to 344 register them in the IANA "CWT Confirmation Methods" registry 345 established in Section 7.2. 347 4. Security Considerations 349 All the security considerations that are discussed in [RFC8392] also 350 apply here. In addition, proof of possession introduces its own 351 unique security issues. Possessing a key is only valuable if it is 352 kept secret. Appropriate means must be used to ensure that 353 unintended parties do not learn private key or symmetric key values. 355 Applications utilizing proof of possession SHOULD also utilize 356 audience restriction, as described in Section 3.1.3 of [RFC8392], as 357 it provides additional protections. Audience restriction can be used 358 by recipients to reject messages intended for different recipients. 359 (Of course, applications not using proof of possession can also 360 benefit from using audience restriction to reject messages intended 361 for different recipients.) 363 CBOR Web Tokens with proof-of-possession keys are used in context of 364 an architecture, such as the ACE OAuth Framework 365 [I-D.ietf-ace-oauth-authz], in which protocols are used by a 366 presenter to request these tokens and to subsequently use them with 367 recipients. Proof of possession only provides the intended security 368 gains when the proof is known to be current and not subject to replay 369 attacks; security protocols using mechanisms such as nonces and 370 timestamps can be used to avoid the risk of replay when performing 371 proof of possession for a token. Note that a discussion of the 372 architecture or specific protocols that CWT proof-of-possession 373 tokens are used with is beyond the scope of this specification. 375 As is the case with other information included in a CWT, it is 376 necessary to apply data origin authentication and integrity 377 protection (via a keyed message digest or a digital signature). Data 378 origin authentication ensures that the recipient of the CWT learns 379 about the entity that created the CWT since this will be important 380 for any policy decisions. Integrity protection prevents an adversary 381 from changing any elements conveyed within the CWT payload. Special 382 care has to be applied when carrying symmetric keys inside the CWT 383 since those not only require integrity protection but also 384 confidentiality protection. 386 As described in Section 6 (Key Identification) and Appendix D (Notes 387 on Key Selection) of [JWS], it is important to make explicit trust 388 decisions about the keys. Proof-of-possession signatures made with 389 keys not meeting the application's trust criteria MUST NOT be relied 390 upon. 392 5. Privacy Considerations 394 A proof-of-possession key can be used as a correlation handle if the 395 same key is used on multiple occasions. Thus, for privacy reasons, 396 it is recommended that different proof-of-possession keys be used 397 when interacting with different parties. 399 6. Operational Considerations 401 The use of CWTs with proof-of-possession keys requires additional 402 information to be shared between the involved parties in order to 403 ensure correct processing. The recipient needs to be able to use 404 credentials to verify the authenticity and integrity of the CWT. 405 Furthermore, the recipient may need to be able to decrypt either the 406 whole CWT or the encrypted parts thereof (see Section 3.3). This 407 requires the recipient to know information about the issuer. 408 Likewise, there needs to be agreement between the issuer and the 409 recipient about the claims being used (which is also true of CWTs in 410 general). 412 When an issuer creates a CWT containing a Key ID claim, it needs to 413 make sure that it does not issue another CWT with different claims 414 containing the same Key ID within the lifetime of the CWTs, unless 415 intentionally desired. Failure to do so may allow one party to 416 impersonate another party, with the potential to gain additional 417 privileges. A case where such reuse of a Key ID would be intentional 418 is when a presenter obtains a CWT with different claims (e.g., 419 extended scope) for the same recipient, but wants to continue using 420 an existing security association (e.g., a DTLS session) bound to the 421 key identified by the Key ID. Likewise, if PoP keys are used for 422 multiple different kinds of CWTs in an application and the PoP keys 423 are identified by Key IDs, care must be taken to keep the keys for 424 the different kinds of CWTs segregated so that an attacker cannot 425 cause the wrong PoP key to be used by using a valid Key ID for the 426 wrong kind of CWT. Using an audience restriction for the CWT would 427 be one strategy to mitigate this risk. 429 7. IANA Considerations 431 The following registration procedure is used for all the registries 432 established by this specification. 434 Values are registered on a Specification Required [RFC8126] basis 435 after a three-week review period on the cwt-reg-review@ietf.org 436 mailing list, on the advice of one or more Designated Experts. 437 However, to allow for the allocation of values prior to publication, 438 the Designated Experts may approve registration once they are 439 satisfied that such a specification will be published. [[ Note to 440 the RFC Editor: The name of the mailing list should be determined in 441 consultation with the IESG and IANA. Suggested name: cwt-reg- 442 review@ietf.org. ]] 444 Registration requests sent to the mailing list for review should use 445 an appropriate subject (e.g., "Request to Register CWT Confirmation 446 Method: example"). Registration requests that are undetermined for a 447 period longer than 21 days can be brought directly to IANA's 448 attention (using the iana@iana.org mailing list) for resolution. 450 Designated Experts should determine whether a registration request 451 contains enough information for the registry to be populated with the 452 new values and whether the proposed new functionality already exists. 453 In the case of an incomplete registration or an attempt to register 454 already existing functionality, the Designated Experts should ask for 455 corrections or reject the registration. 457 It is suggested that multiple Designated Experts be appointed who are 458 able to represent the perspectives of different applications using 459 this specification in order to enable broadly informed review of 460 registration decisions. In cases where a registration decision could 461 be perceived as creating a conflict of interest for a particular 462 Expert, that Expert should defer to the judgment of the other 463 Experts. 465 7.1. CBOR Web Token Claims Registration 467 This specification registers the "cnf" claim in the IANA "CBOR Web 468 Token Claims" registry [IANA.CWT.Claims] established by [RFC8392]. 470 7.1.1. Registry Contents 472 o Claim Name: "cnf" 473 o Claim Description: Confirmation 474 o JWT Claim Name: "cnf" 475 o Claim Key: TBD (maybe 8) 476 o Claim Value Type(s): map 477 o Change Controller: IESG 478 o Specification Document(s): Section 3.1 of [[ this document ]] 480 7.2. CWT Confirmation Methods Registry 482 This specification establishes the IANA "CWT Confirmation Methods" 483 registry for CWT "cnf" member values. The registry records the 484 confirmation method member and a reference to the specification that 485 defines it. 487 7.2.1. Registration Template 489 Confirmation Method Name: 490 The human-readable name requested (e.g., "kid"). 492 Confirmation Method Description: 493 Brief description of the confirmation method (e.g., "Key 494 Identifier"). 496 JWT Confirmation Method Name: 497 Claim Name of the equivalent JWT confirmation method value, as 498 registered in [IANA.JWT.Claims]. CWT claims should normally have 499 a corresponding JWT claim. If a corresponding JWT claim would not 500 make sense, the Designated Experts can choose to accept 501 registrations for which the JWT Claim Name is listed as "N/A". 503 Confirmation Key: 504 CBOR map key value for the confirmation method. 506 Confirmation Value Type(s): 507 CBOR types that can be used for the confirmation method value. 509 Change Controller: 510 For Standards Track RFCs, list the "IESG". For others, give the 511 name of the responsible party. 513 Specification Document(s): 514 Reference to the document or documents that specify the parameter, 515 preferably including URIs that can be used to retrieve copies of 516 the documents. An indication of the relevant sections may also be 517 included but is not required. Note that the Designated Experts 518 and IANA must be able to obtain copies of the specification 519 document(s) to perform their work. 521 7.2.2. Initial Registry Contents 523 o Confirmation Method Name: "COSE_Key" 524 o Confirmation Method Description: COSE_Key Representing Public Key 525 o JWT Confirmation Method Name: "jwk" 526 o Confirmation Key: 1 527 o Confirmation Value Type(s): COSE_Key structure 528 o Change Controller: IESG 529 o Specification Document(s): Section 3.2 of [[ this document ]] 531 o Confirmation Method Name: "Encrypted_COSE_Key" 532 o Confirmation Method Description: Encrypted COSE_Key 533 o JWT Confirmation Method Name: "jwe" 534 o Confirmation Key: 2 535 o Confirmation Value Type(s): COSE_Encrypt or COSE_Encrypt0 536 structure (with an optional corresponding COSE_Encrypt or 537 COSE_Encrypt0 tag) 538 o Change Controller: IESG 539 o Specification Document(s): Section 3.3 of [[ this document ]] 541 o Confirmation Method Name: "kid" 542 o Confirmation Method Description: Key Identifier 543 o JWT Confirmation Method Name: "kid" 544 o Confirmation Key: 3 545 o Confirmation Value Type(s): binary string 546 o Change Controller: IESG 547 o Specification Document(s): Section 3.4 of [[ this document ]] 549 8. References 551 8.1. Normative References 553 [IANA.CWT.Claims] 554 IANA, "CBOR Web Token Claims", 555 . 557 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 558 Requirement Levels", BCP 14, RFC 2119, 559 DOI 10.17487/RFC2119, March 1997, 560 . 562 [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object 563 Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, 564 October 2013, . 566 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 567 Writing an IANA Considerations Section in RFCs", BCP 26, 568 RFC 8126, DOI 10.17487/RFC8126, June 2017, 569 . 571 [RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)", 572 RFC 8152, DOI 10.17487/RFC8152, July 2017, 573 . 575 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 576 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 577 May 2017, . 579 [RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig, 580 "CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392, 581 May 2018, . 583 8.2. Informative References 585 [I-D.ietf-ace-oauth-authz] 586 Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and 587 H. Tschofenig, "Authentication and Authorization for 588 Constrained Environments (ACE) using the OAuth 2.0 589 Framework (ACE-OAuth)", draft-ietf-ace-oauth-authz-21 590 (work in progress), February 2019. 592 [IANA.JWT.Claims] 593 IANA, "JSON Web Token Claims", 594 . 596 [JWS] Jones, M., Bradley, J., and N. Sakimura, "JSON Web 597 Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May 598 2015, . 600 [JWT] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token 601 (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, 602 . 604 [OASIS.saml-core-2.0-os] 605 Cantor, S., Kemp, J., Philpott, R., and E. Maler, 606 "Assertions and Protocol for the OASIS Security Assertion 607 Markup Language (SAML) V2.0", OASIS Standard saml-core- 608 2.0-os, March 2005, 609 . 611 [RFC7800] Jones, M., Bradley, J., and H. Tschofenig, "Proof-of- 612 Possession Key Semantics for JSON Web Tokens (JWTs)", 613 RFC 7800, DOI 10.17487/RFC7800, April 2016, 614 . 616 [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data 617 Interchange Format", STD 90, RFC 8259, 618 DOI 10.17487/RFC8259, December 2017, 619 . 621 [RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data 622 Definition Language (CDDL): A Notational Convention to 623 Express Concise Binary Object Representation (CBOR) and 624 JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610, 625 June 2019, . 627 Acknowledgements 629 Thanks to the following people for their reviews of the 630 specification: Roman Danyliw, Christer Holmberg, Benjamin Kaduk, 631 Mirja Kuehlewind, Yoav Nir, Michael Richardson, Adam Roach, Eric 632 Vyncke, and Jim Schaad. 634 Ludwig Seitz and Goeran Selander worked on this document as part of 635 the CelticPlus projects CyberWI and CRITISEC, with funding from 636 Vinnova. 638 Document History 640 [[ to be removed by the RFC Editor before publication as an RFC ]] 642 -11 644 o Addressed remaining IESG review comment by Mirja Kuehlewind. 646 -10 648 o Addressed IESG review comments by Adam Roach and Eric Vyncke. 650 -09 652 o Addressed Gen-ART review comments by Christer Holmberg and SecDir 653 review comments by Yoav Nir. 655 -08 657 o Addressed remaining Area Director review comments by Benjamin 658 Kaduk. 660 -07 662 o Addressed Area Director review by Benjamin Kaduk. 664 -06 666 o Corrected nits identified by Roman Danyliw. 668 -05 670 o Added text suggested by Jim Schaad describing considerations when 671 using the Key ID confirmation method. 673 -04 675 o Addressed additional WGLC comments by Jim Schaad and Roman 676 Danyliw. 678 -03 680 o Addressed review comments by Jim Schaad, see https://www.ietf.org/ 681 mail-archive/web/ace/current/msg02798.html 683 o Removed unnecessary sentence in the introduction regarding the use 684 any strings that could be case-sensitive. 686 o Clarified the terms Presenter and Recipient. 688 o Clarified text about the confirmation claim. 690 -02 692 o Changed "typically" to "often" when describing ways of performing 693 proof of possession. 695 o Changed b64 to hex encoding in an example. 697 o Changed to using the RFC 8174 boilerplate instead of the RFC 2119 698 boilerplate. 700 -01 702 o Now uses CBOR diagnostic notation for the examples. 704 o Added a table summarizing the "cnf" names, keys, and value types. 706 o Addressed some of Jim Schaad's feedback on -00. 708 -00 710 o Created the initial working group draft from draft-jones-ace-cwt- 711 proof-of-possession-01. 713 Authors' Addresses 715 Michael B. Jones 716 Microsoft 718 Email: mbj@microsoft.com 719 URI: http://self-issued.info/ 721 Ludwig Seitz 722 RISE SICS 723 Scheelevaegen 17 724 Lund 223 70 725 Sweden 727 Email: ludwig@ri.se 729 Goeran Selander 730 Ericsson AB 731 Faeroegatan 6 732 Kista 164 80 733 Sweden 735 Email: goran.selander@ericsson.com 737 Samuel Erdtman 738 Spotify 740 Email: erdtman@spotify.com 742 Hannes Tschofenig 743 Arm Ltd. 744 Hall in Tirol 6060 745 Austria 747 Email: Hannes.Tschofenig@arm.com