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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 5226 (Obsoleted by RFC 8126) ** 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RFC 7049 (Obsoleted by RFC 8949) ** Obsolete normative reference: RFC 8152 (Obsoleted by RFC 9052, RFC 9053) == Outdated reference: A later version (-46) exists of draft-ietf-ace-oauth-authz-16 -- Obsolete informational reference (is this intentional?): RFC 7159 (Obsoleted by RFC 8259) Summary: 4 errors (**), 0 flaws (~~), 2 warnings (==), 2 comments (--). 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 13, 2019 RISE SICS 6 G. Selander 7 Ericsson AB 8 S. Erdtman 9 Spotify 10 H. Tschofenig 11 ARM Ltd. 12 November 9, 2018 14 Proof-of-Possession Key Semantics for CBOR Web Tokens (CWTs) 15 draft-ietf-ace-cwt-proof-of-possession-05 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 May 13, 2019. 44 Copyright Notice 46 Copyright (c) 2018 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 . . . . . . . . . . 8 70 4. Security Considerations . . . . . . . . . . . . . . . . . . . 8 71 5. Privacy Considerations . . . . . . . . . . . . . . . . . . . 9 72 6. Operational Considerations . . . . . . . . . . . . . . . . . 10 73 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 74 7.1. CBOR Web Token Claims Registration . . . . . . . . . . . 11 75 7.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 11 76 7.2. CWT Confirmation Methods Registry . . . . . . . . . . . . 11 77 7.2.1. Registration Template . . . . . . . . . . . . . . . . 11 78 7.2.2. Initial Registry Contents . . . . . . . . . . . . . . 12 79 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 80 8.1. Normative References . . . . . . . . . . . . . . . . . . 13 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 [RFC7159] 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. 119 In context of OAuth this party is also called OAuth Client. 121 Recipient 122 Party that receives the CWT containing the proof-of-possession key 123 information from the presenter. 124 In context of OAuth this party is also called OAuth Resource 125 Server. 127 3. Representations for Proof-of-Possession Keys 129 By including a "cnf" (confirmation) claim in a CWT, the issuer of the 130 CWT declares that the presenter possesses a particular key and that 131 the recipient can cryptographically confirm that the presenter has 132 possession of that key. The value of the "cnf" claim is a CBOR map 133 and the members of that map identify the proof-of-possession key. 135 The presenter can be identified in one of several ways by the CWT, 136 depending upon the application requirements. For instance, some 137 applications may use the CWT "sub" (subject) claim [RFC8392], to 138 identify the presenter. Other applications may use the "iss" claim 139 to identify the presenter. In some applications, the subject 140 identifier might be relative to the issuer identified by the "iss" 141 (issuer) claim [RFC8392]. The actual mechanism used is dependent 142 upon the application. The case in which the presenter is the subject 143 of the CWT is analogous to Security Assertion Markup Language (SAML) 144 2.0 [OASIS.saml-core-2.0-os] SubjectConfirmation usage. 146 3.1. Confirmation Claim 148 The "cnf" claim in the CWT is used to carry confirmation methods. 149 Some of them use proof-of-possession keys while others do not. This 150 design is analogous to the SAML 2.0 [OASIS.saml-core-2.0-os] 151 SubjectConfirmation element in which a number of different subject 152 confirmation methods can be included (including proof-of-possession 153 key information). 155 The set of confirmation members that a CWT must contain to be 156 considered valid is context dependent and is outside the scope of 157 this specification. Specific applications of CWTs will require 158 implementations to understand and process some confirmation members 159 in particular ways. However, in the absence of such requirements, 160 all confirmation members that are not understood by implementations 161 MUST be ignored. 163 This specification establishes the IANA "CWT Confirmation Methods" 164 registry for these members in Section 7.2 and registers the members 165 defined by this specification. Other specifications can register 166 other members used for confirmation, including other members for 167 conveying proof-of-possession keys using different key 168 representations. 170 The "cnf" claim value MUST represent only a single proof-of- 171 possession key. At most one of the "COSE_Key" and 172 "Encrypted_COSE_Key" confirmation values defined in Figure 1 may be 173 present. Note that if an application needs to represent multiple 174 proof-of-possession keys in the same CWT, one way for it to achieve 175 this is to use other claim names, in addition to "cnf", to hold the 176 additional proof-of-possession key information. These claims could 177 use the same syntax and semantics as the "cnf" claim. Those claims 178 would be defined by applications or other specifications and could be 179 registered in the IANA "CBOR Web Token Claims" registry 180 [IANA.CWT.Claims]. 182 /--------------------+-----+-------------------------------\ 183 | Name | Key | Value type | 184 |--------------------+-----+-------------------------------| 185 | COSE_Key | 1 | COSE_Key | 186 | Encrypted_COSE_Key | 2 | COSE_Encrypt or COSE_Encrypt0 | 187 | kid | 3 | binary string | 188 \--------------------+-----+-------------------------------/ 190 Figure 1: Summary of the cnf names, keys, and value types 192 3.2. Representation of an Asymmetric Proof-of-Possession Key 194 When the key held by the presenter is an asymmetric private key, the 195 "COSE_Key" member is a COSE_Key [RFC8152] representing the 196 corresponding asymmetric public key. The following example (using 197 CBOR diagnostic notation) demonstrates such a declaration in the CWT 198 Claims Set of a CWT: 200 { 201 /iss/ 1 : "coaps://server.example.com", 202 /aud/ 3 : "coaps://client.example.org", 203 /exp/ 4 : 1361398824, 204 /cnf/ 8 :{ 205 /COSE_Key/ 1 :{ 206 /kty/ 1 : /EC/ 2, 207 /crv/ -1 : /P-256/ 1, 208 /x/ -2 : h'd7cc072de2205bdc1537a543d53c60a6acb62eccd890c7fa27c9 209 e354089bbe13', 210 /y/ -3 : h'f95e1d4b851a2cc80fff87d8e23f22afb725d535e515d020731e 211 79a3b4e47120' 212 } 213 } 214 } 216 The COSE_Key MUST contain the required key members for a COSE_Key of 217 that key type and MAY contain other COSE_Key members, including the 218 "kid" (Key ID) member. 220 The "COSE_Key" member MAY also be used for a COSE_Key representing a 221 symmetric key, provided that the CWT is encrypted so that the key is 222 not revealed to unintended parties. The means of encrypting a CWT is 223 explained in [RFC8392]. If the CWT is not encrypted, the symmetric 224 key MUST be encrypted as described in Section 3.3. 226 3.3. Representation of an Encrypted Symmetric Proof-of-Possession Key 228 When the key held by the presenter is a symmetric key, the 229 "Encrypted_COSE_Key" member is an encrypted COSE_Key [RFC8152] 230 representing the symmetric key encrypted to a key known to the 231 recipient using COSE_Encrypt or COSE_Encrypt0. 233 The following example (using CBOR diagnostic notation, with 234 linebreaks for readability) illustrates a symmetric key that could 235 subsequently be encrypted for use in the "Encrypted_COSE_Key" member: 237 { 238 /kty/ 1 : /Symmetric/ 4, 239 /alg/ 3 : /HMAC256/ 5, 240 /k/ -1 : h'6684523ab17337f173500e5728c628547cb37df 241 e68449c65f885d1b73b49eae1A0B0C0D0E0F10' 242 } 244 The COSE_Key representation is used as the plaintext when encrypting 245 the key. 247 The following example CWT Claims Set of a CWT (using CBOR diagnostic 248 notation, with linebreaks for readability) illustrates the use of an 249 encrypted symmetric key as the "Encrypted_COSE_Key" member value: 251 { 252 /iss/ 1 : "coaps://server.example.com", 253 /sub/ 2 : "24400320", 254 /aud/ 3: "s6BhdRkqt3", 255 /exp/ 4 : 1311281970, 256 /iat/ 5 : 1311280970, 257 /cnf/ 8 : { 258 /COSE_Encrypt0/ 2 : [ 259 /protected header / h'A1010A' /{ \alg\ 1:10 \AES-CCM-16-64-128\}/, 260 /unprotected header/ { / iv / 5: h'636898994FF0EC7BFCF6D3F95B'}, 261 /ciphertext/ h'0573318A3573EB983E55A7C2F06CADD0796C9E584F1D0E3E 262 A8C5B052592A8B2694BE9654F0431F38D5BBC8049FA7F13F' 263 ] 264 } 265 } 267 The example above was generated with the key: 269 h'6162630405060708090a0b0c0d0e0f10' 271 3.4. Representation of a Key ID for a Proof-of-Possession Key 273 The proof-of-possession key can also be identified by the use of a 274 Key ID instead of communicating the actual key, provided the 275 recipient is able to obtain the identified key using the Key ID. In 276 this case, the issuer of a CWT declares that the presenter possesses 277 a particular key and that the recipient can cryptographically confirm 278 proof of possession of the key by the presenter by including a "cnf" 279 claim in the CWT whose value is a CBOR map with the CBOR map 280 containing a "kid" member identifying the key. 282 The following example (using CBOR diagnostic notation) demonstrates 283 such a declaration in the CWT Claims Set of a CWT: 285 { 286 /iss/ 1 : "coaps://server.example.com", 287 /aud/ 3 : "coaps://client.example.org", 288 /exp/ 4 : 1361398824, 289 /cnf/ 8 : { 290 /kid/ 2 : h'dfd1aa976d8d4575a0fe34b96de2bfad' 291 } 292 } 294 The content of the "kid" value is application specific. For 295 instance, some applications may choose to use a cryptographic hash of 296 the public key value as the "kid" value. 298 Note that the use of a Key ID to identify a proof-of-possesion key 299 needs to be carefully circumscribed, as described below and in 300 Section 6. Where the Key ID is not a cryptographic value derived 301 from the key or where all of the parties involved are not validating 302 the cryptographic derivation, it is possible to get into situations 303 where the same Key ID is being used for multiple keys. The 304 implication of this is that a recipient may have multiple keys known 305 to it that have the same Key ID, and thus it might not know which 306 proof-of-possession key is associated with the CWT. 308 In the world of constrained Internet of Things (IoT) devices, there 309 is frequently a restriction on the size of Key IDs, either because of 310 table constraints or a desire to keep message sizes small. These 311 restrictions are going to protocol dependent. For example, DTLS can 312 use a Key ID of any size. However, if the key is being used with 313 COSE encrypted message, then the length of the key needs to be 314 minimized and may have a limit as small as one byte. 316 Note that the value of a Key ID is not always the same for different 317 parties. When sending a COSE encrypted message with a shared key, 318 the Key ID may be different on both sides of the conversation, with 319 the appropriate one being included in the message based on the 320 recipient of the message. 322 For symmetric keys, the Key ID is normally going to be generated by 323 the CWT issuer. This means that enforcing a rule that Key ID values 324 only match if CWTs have the same issuer works for matching Key IDs 325 between CWTs. In this case, the issuer can ensure that there are no 326 collisions between currently active symmetric keys for all CWTs that 327 it has issued. This allows for a recipient to use the pair of issuer 328 and Key ID for matching keys. 330 For asymmetric keys, the Key ID value is normally going to be 331 generated by the CWT recipient, thus the possibility of collisions is 332 greater. For instance, recipients might start by assigning a Key ID 333 of 0, given that Key IDs are frequently only needed to be unique and 334 meaningful to the recipient. This problem can be addressed in a 335 couple of different ways, depending on how the Key ID value is going 336 to be used: 338 o The issuer can assign a new unique Key ID the first time it sees 339 the key. Depending on the protocol being used, the new value may 340 then need to be transported to the presenter by the protocol used 341 to issue CWTs. In this case, the rule of requiring that the 342 issuer, Key ID pair be used for matching works. 344 o The issuer can use a different confirmation method if a collision 345 might be unavoidable. 347 o A recipient can decide not to use a CWT based on a created Key ID 348 if it does not fit the recipient's requirements. 350 o If an issuer is going to use the Key ID confirmation method and is 351 not going to guarantee that serial number uniqueness is going to 352 be preserved, the recipient needs to have that information 353 configured into it so that appropriate actions can be taken. 355 3.5. Specifics Intentionally Not Specified 357 Proof of possession is often demonstrated by having the presenter 358 sign a value determined by the recipient using the key possessed by 359 the presenter. This value is sometimes called a "nonce" or a 360 "challenge". 362 The means of communicating the nonce and the nature of its contents 363 are intentionally not described in this specification, as different 364 protocols will communicate this information in different ways. 365 Likewise, the means of communicating the signed nonce is also not 366 specified, as this is also protocol specific. 368 Note that another means of proving possession of the key when it is a 369 symmetric key is to encrypt the key to the recipient. The means of 370 obtaining a key for the recipient is likewise protocol specific. 372 4. Security Considerations 374 All of the security considerations that are discussed in [RFC8392] 375 also apply here. In addition, proof of possession introduces its own 376 unique security issues. Possessing a key is only valuable if it is 377 kept secret. Appropriate means must be used to ensure that 378 unintended parties do not learn private key or symmetric key values. 380 Applications utilizing proof of possession SHOULD also utilize 381 audience restriction, as described in Section 4.1.3 of [JWT], as it 382 provides additional protections. Audience restriction can be used by 383 recipients to reject messages intended for different recipients. 385 A recipient might not understand the "cnf" claim. Applications that 386 require the proof-of-possession keys communicated with it to be 387 understood and processed MUST ensure that the parts of this 388 specification that they use are implemented. 390 CBOR Web Tokens with proof-of-possession keys are used in context of 391 an architecture, such as the ACE OAuth Framework 392 [I-D.ietf-ace-oauth-authz], in which protocols are used by a 393 presenter to request these tokens and to subsequently use them with 394 recipients. To avoid replay attacks when the proof-of-possession 395 tokens are sent to presenters, a security protocol, which uses 396 mechansims such as nonces or timestamps, has to be utilized. Note 397 that a discussion of the architecture or specific protocols that CWT 398 proof-of-possession tokens are used with is beyond the scope of this 399 specification. 401 As is the case with other information included in a CWT, it is 402 necessary to apply data origin authentication and integrity 403 protection (via a keyed message digest or a digital signature). Data 404 origin authentication ensures that the recipient of the CWT learns 405 about the entity that created the CWT since this will be important 406 for any policy decisions. Integrity protection prevents an adversary 407 from changing any elements conveyed within the CWT payload. Special 408 care has to be applied when carrying symmetric keys inside the CWT 409 since those not only require integrity protection but also 410 confidentiality protection. 412 As described in Section 6 (Key Identification) and Appendix D (Notes 413 on Key Selection) of [JWS], it is important to make explicit trust 414 decisions about the keys. Proof-of-possession signatures made with 415 keys not meeting the application's trust criteria MUST NOT be relied 416 upon. 418 5. Privacy Considerations 420 A proof-of-possession key can be used as a correlation handle if the 421 same key is used with multiple parties. Thus, for privacy reasons, 422 it is recommended that different proof-of-possession keys be used 423 when interacting with different parties. 425 6. Operational Considerations 427 The use of CWTs with proof-of-possession keys requires additional 428 information to be shared between the involved parties in order to 429 ensure correct processing. The recipient needs to be able to use 430 credentials to verify the authenticity, integrity, and potentially 431 the confidentiality of the CWT and its content. This requires the 432 recipient to know information about the issuer. Likewise, there 433 needs to be agreement between the issuer and the recipient about the 434 claims being used (which is also true of CWTs in general). 436 When an issuer creates a CWT containing a Key ID claim, it needs to 437 make sure that it does not issue another CWT containing the same Key 438 ID with a different content, or for a different subject, within the 439 lifetime of the CWTs, unless intentionally desired. Failure to do so 440 may allow one party to impersonate another party, with the potential 441 to gain additional privileges. Likewise, if PoP keys are used for 442 multiple different kinds of CWTs in an application and the PoP keys 443 are identified by Key IDs, care must be taken to keep the keys for 444 the different kinds of CWTs segregated so that an attacker cannot 445 cause the wrong PoP key to be used by using a valid Key ID for the 446 wrong kind of CWT. 448 7. IANA Considerations 450 The following registration procedure is used for all the registries 451 established by this specification. 453 Values are registered on a Specification Required [RFC5226] basis 454 after a three-week review period on the cwt-reg-review@ietf.org 455 mailing list, on the advice of one or more Designated Experts. 456 However, to allow for the allocation of values prior to publication, 457 the Designated Experts may approve registration once they are 458 satisfied that such a specification will be published. [[ Note to 459 the RFC Editor: The name of the mailing list should be determined in 460 consultation with the IESG and IANA. Suggested name: cwt-reg- 461 review@ietf.org. ]] 463 Registration requests sent to the mailing list for review should use 464 an appropriate subject (e.g., "Request to Register CWT Confirmation 465 Method: example"). Registration requests that are undetermined for a 466 period longer than 21 days can be brought to the IESG's attention 467 (using the iesg@ietf.org mailing list) for resolution. 469 Criteria that should be applied by the Designated Experts include 470 determining whether the proposed registration duplicates existing 471 functionality, determining whether it is likely to be of general 472 applicability or whether it is useful only for a single application, 473 and evaluating the security properties of the item being registered 474 and whether the registration makes sense. 476 It is suggested that multiple Designated Experts be appointed who are 477 able to represent the perspectives of different applications using 478 this specification in order to enable broadly informed review of 479 registration decisions. In cases where a registration decision could 480 be perceived as creating a conflict of interest for a particular 481 Expert, that Expert should defer to the judgment of the other 482 Experts. 484 7.1. CBOR Web Token Claims Registration 486 This specification registers the "cnf" claim in the IANA "CBOR Web 487 Token Claims" registry [IANA.CWT.Claims] established by [RFC8392]. 489 7.1.1. Registry Contents 491 o Claim Name: "cnf" 492 o Claim Description: Confirmation 493 o JWT Claim Name: "cnf" 494 o Claim Key: TBD (maybe 8) 495 o Claim Value Type(s): map 496 o Change Controller: IESG 497 o Specification Document(s): Section 3.1 of [[ this document ]] 499 7.2. CWT Confirmation Methods Registry 501 This specification establishes the IANA "CWT Confirmation Methods" 502 registry for CWT "cnf" member values. The registry records the 503 confirmation method member and a reference to the specification that 504 defines it. 506 7.2.1. Registration Template 508 Confirmation Method Name: 509 The human-readable name requested (e.g., "kid"). 511 Confirmation Method Description: 512 Brief description of the confirmation method (e.g., "Key 513 Identifier"). 515 JWT Confirmation Method Name: 516 Claim Name of the equivalent JWT confirmation method value, as 517 registered in [IANA.JWT.Claims]. CWT claims should normally have 518 a corresponding JWT claim. If a corresponding JWT claim would not 519 make sense, the Designated Experts can choose to accept 520 registrations for which the JWT Claim Name is listed as "N/A". 522 Confirmation Key: 523 CBOR map key value for the confirmation method. 525 Confirmation Value Type(s): 526 CBOR types that can be used for the confirmation method value. 528 Change Controller: 529 For Standards Track RFCs, list the "IESG". For others, give the 530 name of the responsible party. Other details (e.g., postal 531 address, email address, home page URI) may also be included. 533 Specification Document(s): 534 Reference to the document or documents that specify the parameter, 535 preferably including URIs that can be used to retrieve copies of 536 the documents. An indication of the relevant sections may also be 537 included but is not required. 539 7.2.2. Initial Registry Contents 541 o Confirmation Method Name: "COSE_Key" 542 o Confirmation Method Description: COSE_Key Representing Public Key 543 o JWT Confirmation Method Name: "jwk" 544 o Confirmation Key: 1 545 o Confirmation Value Type(s): COSE_Key structure 546 o Change Controller: IESG 547 o Specification Document(s): Section 3.2 of [[ this document ]] 549 o Confirmation Method Name: "Encrypted_COSE_Key" 550 o Confirmation Method Description: Encrypted COSE_Key 551 o JWT Confirmation Method Name: "jwe" 552 o Confirmation Key: 2 553 o Confirmation Value Type(s): COSE_Encrypt or COSE_Encrypt0 554 structure (with an optional corresponding COSE_Encrypt or 555 COSE_Encrypt0 tag) 556 o Change Controller: IESG 557 o Specification Document(s): Section 3.3 of [[ this document ]] 559 o Confirmation Method Name: "kid" 560 o Confirmation Method Description: Key Identifier 561 o JWT Confirmation Method Name: "kid" 562 o Confirmation Key: 3 563 o Confirmation Value Type(s): binary string 564 o Change Controller: IESG 565 o Specification Document(s): Section 3.4 of [[ this document ]] 567 8. References 569 8.1. Normative References 571 [IANA.CWT.Claims] 572 IANA, "CBOR Web Token Claims", 573 . 575 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 576 Requirement Levels", BCP 14, RFC 2119, 577 DOI 10.17487/RFC2119, March 1997, 578 . 580 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 581 IANA Considerations Section in RFCs", RFC 5226, 582 DOI 10.17487/RFC5226, May 2008, 583 . 585 [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object 586 Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, 587 October 2013, . 589 [RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)", 590 RFC 8152, DOI 10.17487/RFC8152, July 2017, 591 . 593 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 594 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 595 May 2017, . 597 [RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig, 598 "CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392, 599 May 2018, . 601 8.2. Informative References 603 [I-D.ietf-ace-oauth-authz] 604 Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and 605 H. Tschofenig, "Authentication and Authorization for 606 Constrained Environments (ACE) using the OAuth 2.0 607 Framework (ACE-OAuth)", draft-ietf-ace-oauth-authz-16 608 (work in progress), October 2018. 610 [IANA.JWT.Claims] 611 IANA, "JSON Web Token Claims", 612 . 614 [JWS] Jones, M., Bradley, J., and N. Sakimura, "JSON Web 615 Signature (JWS)", RFC 7515, May 2015, 616 . 618 [JWT] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token 619 (JWT)", RFC 7519, DOI 10.17487/RFC7159, May 2015, 620 . 622 [OASIS.saml-core-2.0-os] 623 Cantor, S., Kemp, J., Philpott, R., and E. Maler, 624 "Assertions and Protocol for the OASIS Security Assertion 625 Markup Language (SAML) V2.0", OASIS Standard saml-core- 626 2.0-os, March 2005, 627 . 629 [RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data 630 Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March 631 2014, . 633 [RFC7800] Jones, M., Bradley, J., and H. Tschofenig, "Proof-of- 634 Possession Key Semantics for JSON Web Tokens (JWTs)", 635 RFC 7800, DOI 10.17487/RFC7800, April 2016, 636 . 638 Acknowledgements 640 Thanks to the following people for their reviews of the 641 specification: Roman Danyliw, Michael Richardson, and Jim Schaad. 643 Ludwig Seitz and Goeran Selander worked on this document as part of 644 the CelticPlus project CyberWI, with funding from Vinnova. 646 Document History 648 [[ to be removed by the RFC Editor before publication as an RFC ]] 650 -05 652 o Added text suggested by Jim Schaad describing considerations when 653 using the Key ID confirmation method. 655 -04 657 o Addressed additional WGLC comments by Jim Schaad and Roman 658 Danyliw. 660 -03 661 o Addressed review comments by Jim Schaad, see https://www.ietf.org/ 662 mail-archive/web/ace/current/msg02798.html 664 o Removed unnecessary sentence in the introduction regarding the use 665 any strings that could be case-sensitive. 667 o Clarified the terms Presenter and Recipient. 669 o Clarified text about the confirmation claim. 671 -02 673 o Changed "typically" to "often" when describing ways of performing 674 proof of possession. 676 o Changed b64 to hex encoding in an example. 678 o Changed to using the RFC 8174 boilerplate instead of the RFC 2119 679 boilerplate. 681 -01 683 o Now uses CBOR diagnostic notation for the examples. 685 o Added a table summarizing the "cnf" names, keys, and value types. 687 o Addressed some of Jim Schaad's feedback on -00. 689 -00 691 o Created the initial working group draft from draft-jones-ace-cwt- 692 proof-of-possession-01. 694 Authors' Addresses 696 Michael B. Jones 697 Microsoft 699 Email: mbj@microsoft.com 700 URI: http://self-issued.info/ 701 Ludwig Seitz 702 RISE SICS 703 Scheelevaegen 17 704 Lund 223 70 705 Sweden 707 Email: ludwig@ri.se 709 Goeran Selander 710 Ericsson AB 711 Faeroegatan 6 712 Kista 164 80 713 Sweden 715 Email: goran.selander@ericsson.com 717 Samuel Erdtman 718 Spotify 720 Email: erdtman@spotify.com 722 Hannes Tschofenig 723 ARM Ltd. 724 Hall in Tirol 6060 725 Austria 727 Email: Hannes.Tschofenig@arm.com