ACE Working Group E. Wahlstroem Internet-Draft Intended status: Informational M. Jones Expires: January 8, 2017 Microsoft H. Tschofenig ARM Ltd. S. Erdtman Spotify AB July 7, 2016 CBOR Web Token (CWT) draft-ietf-ace-cbor-web-token-01 Abstract CBOR Web Token (CWT) is a compact means of representing claims to be transferred between two parties. CWT is a profile of the JSON Web Token (JWT) that is optimized for constrained devices. The claims in a CWT are encoded in the Concise Binary Object Representation (CBOR) and CBOR Object Signing and Encryption (COSE) is used for added application layer security protection. A claim is a piece of information asserted about a subject and is represented as a name/ value pair consisting of a claim name and a claim value. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on January 8, 2017. Copyright Notice Copyright (c) 2016 IETF Trust and the persons identified as the document authors. All rights reserved. Wahlstroem, et al. Expires January 8, 2017 [Page 1] Internet-Draft CBOR Web Token July 2016 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Claims . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Claim Names . . . . . . . . . . . . . . . . . . . . . . . 4 3.1.1. iss (Issuer) Claim . . . . . . . . . . . . . . . . . 4 3.1.2. sub (Subject) Claim . . . . . . . . . . . . . . . . . 4 3.1.3. aud (Audience) Claim . . . . . . . . . . . . . . . . 4 3.1.4. exp (Expiration Time) Claim . . . . . . . . . . . . . 5 3.1.5. nbf (Not Before) Claim . . . . . . . . . . . . . . . 5 3.1.6. iat (Issued At) Claim . . . . . . . . . . . . . . . . 5 3.1.7. cti (CWT ID) Claim . . . . . . . . . . . . . . . . . 5 4. Summary of the values, CBOR major types and encoded claim keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5. Creating and Validating CWTs . . . . . . . . . . . . . . . . 6 5.1. Creating a CWT . . . . . . . . . . . . . . . . . . . . . 6 5.2. Validating a CWT . . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 7.1. CBOR Web Token (CWT) Claims Registry . . . . . . . . . . 8 7.1.1. Registration Template . . . . . . . . . . . . . . . . 8 7.1.2. Initial Registry Contents . . . . . . . . . . . . . . 9 7.2. CoAP Content-Format Registration . . . . . . . . . . . . 10 7.2.1. Registry Contents . . . . . . . . . . . . . . . . . . 10 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 8.1. Normative References . . . . . . . . . . . . . . . . . . 11 8.2. Informative References . . . . . . . . . . . . . . . . . 12 Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 12 A.1. CWT with "aud" and symmetric key . . . . . . . . . . . . 12 A.2. CWT with "aud" and EC key . . . . . . . . . . . . . . . . 13 A.3. Full CWT . . . . . . . . . . . . . . . . . . . . . . . . 15 Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 18 Appendix C. Document History . . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 Wahlstroem, et al. Expires January 8, 2017 [Page 2] Internet-Draft CBOR Web Token July 2016 1. Introduction The JSON Web Token (JWT) [RFC7519] is a standardized security token format that has found use in OAuth 2.0 and OpenID Connect deployments, among other applications. JWT uses JSON Web Signatures (JWS) [RFC7515] and JSON Web Encryption (JWE) [RFC7516] to secure the contents of the JWT, which is a set of claims represented in JSON [RFC7519]. The use of JSON for encoding information is popular for Web and native applications, but it is considered inefficient for some Internet of Things (IoT) systems that use low power radio technologies. In this document an alternative encoding of claims is defined. Instead of using JSON, as provided by JWTs, this specification uses CBOR [RFC7049] and calls this new structure "CBOR Web Token (CWT)", which is a compact means of representing secured claims to be transferred between two parties. CWT is closely related to JWT. It references the JWT claims and both its name and pronunciation are derived from JWT. To protect the claims contained in CWTs, the CBOR Object Signing and Encryption (COSE) [I-D.ietf-cose-msg] specification is used. The suggested pronunciation of CWT is the same as the English word "cot". 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in "Key words for use in RFCs to Indicate Requirement Levels" [RFC2119]. This document reuses terminology from JWT [RFC7519] and COSE [I-D.ietf-cose-msg]. Type3StringOrURI: The "Type3StringOrURI" term has the same meaning, syntax, and processing rules as the "StringOrUri" term defined in Section 2 of JWT [RFC7519], except that Type3StringOrURI uses CBOR major type 3 instead of a JSON string value. Type6NumericDate: The "Type6NumericDate" term has the same meaning, syntax, and processing rules as the "NumericDate" term defined in Section 2 of JWT [RFC7519], except that Type6NumericDate uses CBOR major type 6, with tag value 1, instead of a numeric JSON value. CBOR encoded claim key: Wahlstroem, et al. Expires January 8, 2017 [Page 3] Internet-Draft CBOR Web Token July 2016 The key used to identify a claim value. 3. Claims The set of claims that a CWT must contain to be considered valid is context dependent and is outside the scope of this specification. Specific applications of CWTs will require implementations to understand and process some claims in particular ways. However, in the absence of such requirements, all claims that are not understood by implementations MUST be ignored. To keep CWTs as small as possible, the CBOR encoded claim keys are represented using CBOR major type 0. Section 4 summaries all keys used to identity the claims defined in this document. 3.1. Claim Names None of the claims defined below are intended to be mandatory to use or implement. They rather provide a starting point for a set of useful, interoperable claims. Applications using CWTs should define which specific claims they use and when they are required or optional. 3.1.1. iss (Issuer) Claim The "iss" (issuer) claim has the same meaning, syntax, and processing rules as the "iss" claim defined in Section 4.1.1 of JWT [RFC7519], except that the format MUST be a Type3StringOrURI. The CBOR encoded claim key 1 MUST be used to identify this claim. 3.1.2. sub (Subject) Claim The "sub" (subject) claim has the same meaning, syntax, and processing rules as the "sub" claim defined in Section 4.1.2 of JWT [RFC7519], except that the format MUST be a Type3StringOrURI. The CBOR encoded claim key 2 MUST be used to identify this claim. 3.1.3. aud (Audience) Claim The "aud" (audience) claim has the same meaning, syntax, and processing rules as the "aud" claim defined in Section 4.1.3 of JWT [RFC7519], except that the format MUST be a Type3StringOrURI. The CBOR encoded claim key 3 MUST be used to identify this claim. Wahlstroem, et al. Expires January 8, 2017 [Page 4] Internet-Draft CBOR Web Token July 2016 3.1.4. exp (Expiration Time) Claim The "exp" (expiration time) claim has the same meaning, syntax, and processing rules as the "exp" claim defined in Section 4.1.4 of JWT [RFC7519], except that the format MUST be a Type6NumericDate. The CBOR encoded claim key 4 MUST be used to identify this claim. 3.1.5. nbf (Not Before) Claim The "nbf" (not before) claim has the same meaning, syntax, and processing rules as the "nbf" claim defined in Section 4.1.5 of JWT [RFC7519], except that the format MUST be a Type6NumericDate. The CBOR encoded claim key 5 MUST be used to identify this claim. 3.1.6. iat (Issued At) Claim The "iat" (issued at) claim has the same meaning, syntax, and processing rules as the "iat" claim defined in Section 4.1.6 of JWT [RFC7519], except that the format MUST be a Type6NumericDate. The CBOR encoded claim key 6 MUST be used to identify this claim. 3.1.7. cti (CWT ID) Claim The "cti" (CWT ID) claim has the same meaning, syntax, and processing rules as the "jti" claim defined in Section 4.1.7 of JWT [RFC7519], except that the format MUST be of major type 2, binary string. The CBOR encoded claim key 7 MUST be used to identify this claim. 4. Summary of the values, CBOR major types and encoded claim keys /---------+------------------------+--------------------------\ | Claim | CBOR encoded claim key | CBOR major type of value | |---------+------------------------+--------------------------| | iss | 1 | 3 | | sub | 2 | 3 | | aud | 3 | 3 | | exp | 4 | 6 tag value 1 | | nbf | 5 | 6 tag value 1 | | iat | 6 | 6 tag value 1 | | cti | 7 | 2 | \---------+------------------------+--------------------------/ Figure 1: Summary of the values, CBOR major types and encoded claim keys. Wahlstroem, et al. Expires January 8, 2017 [Page 5] Internet-Draft CBOR Web Token July 2016 5. Creating and Validating CWTs 5.1. Creating a CWT To create a CWT, the following steps are performed. The order of the steps is not significant in cases where there are no dependencies between the inputs and outputs of the steps. 1. Create a CWT Claims Set containing the desired claims. 2. Let the Message be the binary representation of the CWT Claims Set. 3. Create a COSE Header containing the desired set of Header Parameters. The CWT Header MUST be a valid according to the [I-D.ietf-cose-msg] specification. 4. Depending upon whether the CWT is signed, MACed or encrypted, there are three cases: * If the CWT is signed, create a COSE_Sign/COSE_Sign1 object using the Message as the COSE_Sign/COSE_Sign1 Payload; all steps specified in [I-D.ietf-cose-msg] for creating a COSE_Sign/COSE_Sign1 object MUST be followed. * Else, if the CWT is MACed, create a COSE_Mac/COSE_Mac0 object using the Message as the COSE_Mac/COSE_Mac0 Payload; all steps specified in [I-D.ietf-cose-msg] for creating a COSE_Mac/ COSE_Mac0 object MUST be followed. * Else, if the CWT is a COSE_Encrypt/COSE_Encrypt0 object, create a COSE_Encrypt/COSE_Encrypt0 using the Message as the plaintext for the COSE_Encrypt/COSE_Encrypt0 object; all steps specified in [I-D.ietf-cose-msg] for creating a COSE_Encrypt/ COSE_Encrypt0 object MUST be followed. 5. If a nested signing, MACing or encryption operation will be performed, let the Message be the COSE_Sign/COSE_Sign1, COSE_Mac/ COSE_Mac0 or COSE_Encrypt/COSE_Encrypt0, and return to Step 3, using "content type" header value of "CWT" in the new COSE Header created in that step. Note: If integrity (signing/MACing) and confidentiality (encryption) protection are needed, it is recommended to use an authenticated encryption algorithm to save space and processing. Wahlstroem, et al. Expires January 8, 2017 [Page 6] Internet-Draft CBOR Web Token July 2016 5.2. Validating a CWT When validating a CWT, the following steps are performed. The order of the steps is not significant in cases where there are no dependencies between the inputs and outputs of the steps. If any of the listed steps fail, then the CWT MUST be rejected -- that is, treated by the application as an invalid input. 1. Verify that the CWT is a valid CBOR object. 2. Verify that the resulting COSE Header includes only parameters and values whose syntax and semantics are both understood and supported or that are specified as being ignored when not understood. 3. Use the CBOR tag to determine the type the CWT, COSE_Sign/ COSE_Sign1, COSE_Mac/COSE_Mac0 or COSE_Encrypt/COSE_Encrypt0. 4. Depending upon whether the CWT is a COSE_Sign/COSE_Sign1, COSE_Mac/COSE_Mac0 or COSE_Encrypt/COSE_Encrypt0, there are three cases: * If the CWT is a COSE_Sign/COSE_Sign1, follow the steps specified in [I-D.ietf-cose-msg] Section 4 (Signing Objects) for validating a COSE_Sign/COSE_Sign1 object. Let the Message be the COSE_Sign/COSE_Sign1 payload. * Else, if the CWT is a COSE_Mac/COSE_Mac0, follow the steps specified in [I-D.ietf-cose-msg] Section 6 (MAC Objects) for validating a COSE_Mac/COSE_Mac0 object. Let the Message be the COSE_Mac/COSE_Mac0 payload. * Else, if the CWT is a COSE_Encrypt/COSE_Encrypt0 object, follow the steps specified in [I-D.ietf-cose-msg] Section 5 (Encryption Objects) for validating a COSE_Encrypt/ COSE_Encrypt0 object. Let the Message be the resulting plaintext. 5. If the JOSE Header contains a "content type" value of "CWT", then the Message is a CWT that was the subject of nested signing or encryption operations. In this case, return to Step 1, using the Message as the CWT. 6. Verify that the Message is a valid CBOR object; let the CWT Claims Set be this CBOR object. Wahlstroem, et al. Expires January 8, 2017 [Page 7] Internet-Draft CBOR Web Token July 2016 6. Security Considerations The security of the CWT is dependent on the protection offered by COSE. Without protecting the claims contained in a CWT an adversary is able to modify, add or remove claims. Since the claims conveyed in a CWT are used to make authorization decisions it is not only important to protect the CWT in transit but also to ensure that the recipient is able to authenticate the party that collected the claims and created the CWT. Without trust of the recipient in the party that created the CWT no sensible authorization decision can be made. Furthermore, the creator of the CWT needs to carefully evaluate each claim value prior to including it in the CWT so that the recipient can be assured about the correctness of the provided information. 7. IANA Considerations 7.1. CBOR Web Token (CWT) Claims Registry This section establishes the IANA "CBOR Web Token (CWT) Claims" registry. Values are registered on a Specification Required [RFC5226] basis, on the advice of one or more Designated Experts. However, to allow for the allocation of values prior to publication, the Designated Experts may approve registration once they are satisfied that such a specification will be published. Criteria that should be applied by the Designated Experts includes determining whether the proposed registration duplicates existing functionality, whether it is likely to be of general applicability or whether it is useful only for a single application, and whether the registration description is clear. 7.1.1. Registration Template Claim Name: The human-readable name requested (e.g., "iss"). Claim Description: Brief description of the claim (e.g., "Issuer"). JWT Claim Name: Claim Name of the equivalent JWT claim as registered in [IANA.JWT.Claims]. CWT claims should normally have a corresponding JWT claim. If a corresponding JWT claim would not make sense, the Designated Experts can choose to accept registrations for which the JWT Claim Name is listed as "N/A". Wahlstroem, et al. Expires January 8, 2017 [Page 8] Internet-Draft CBOR Web Token July 2016 CBOR Key Value: Key value for the claim. The key value MUST be an integer in the range of 1 to 65536. CBOR Major Type: CBOR Major type and optional tag for the claim. Change Controller: For Standards Track RFCs, list the "IESG". For others, give the name of the responsible party. Other details (e.g., postal address, email address, home page URI) may also be included. Specification Document(s): Reference to the document or documents that specify the parameter, preferably including URIs that can be used to retrieve copies of the documents. An indication of the relevant sections may also be included but is not required. 7.1.2. Initial Registry Contents o Claim Name: "iss" o Claim Description: Issuer o JWT Claim Name: "iss" o CBOR Key Value: 1 o CBOR Major Type: 3 o Change Controller: IESG o Specification Document(s): Section 3.1.1 of [[ this specification ]] o Claim Name: "sub" o Claim Description: Subject o JWT Claim Name: "sub" o CBOR Key Value: 2 o CBOR Major Type: 3 o Change Controller: IESG o Specification Document(s): Section 3.1.2 of [[ this specification ]] o Claim Name: "aud" o Claim Description: Audience o JWT Claim Name: "aud" o CBOR Key Value: 3 o CBOR Major Type: 3 o Change Controller: IESG o Specification Document(s): Section 3.1.3 of [[ this specification ]] o Claim Name: "exp" Wahlstroem, et al. Expires January 8, 2017 [Page 9] Internet-Draft CBOR Web Token July 2016 o Claim Description: Expiration Time o JWT Claim Name: "exp" o CBOR Key Value: 4 o CBOR Major Type: 6, tag value 1 o Change Controller: IESG o Specification Document(s): Section 3.1.4 of [[ this specification ]] o Claim Name: "nbf" o Claim Description: Not Before o JWT Claim Name: "nbf" o CBOR Key Value: 5 o CBOR Major Type: 6, tag value 1 o Change Controller: IESG o Specification Document(s): Section 3.1.5 of [[ this specification ]] o Claim Name: "iat" o Claim Description: Issued At o JWT Claim Name: "iat" o CBOR Key Value: 6 o CBOR Major Type: 6, tag value 1 o Change Controller: IESG o Specification Document(s): Section 3.1.6 of [[ this specification ]] o Claim Name: "cti" o Claim Description: CWT ID o JWT Claim Name: "jti" o CBOR Key Value: 7 o CBOR Major Type: 2 o Change Controller: IESG o Specification Document(s): Section 3.1.7 of [[ this specification ]] 7.2. CoAP Content-Format Registration This section registers the "application/cwt" CoAP Content-Format ID in the "CoRE Parameters" sub-registry "CoAP Content-Format" in the manner described in [RFC7252]. 7.2.1. Registry Contents o Media Type: application/cwt o Encoding: - o Id: TBD (maybe 61) o Reference: [[ this specification ]] Wahlstroem, et al. Expires January 8, 2017 [Page 10] Internet-Draft CBOR Web Token July 2016 8. References 8.1. Normative References [I-D.ietf-cose-msg] Schaad, J., "CBOR Object Signing and Encryption (COSE)", draft-ietf-cose-msg-14 (work in progress), June 2016. [IANA.JWT.Claims] IANA, "JSON Web Token Claims", . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, DOI 10.17487/RFC5226, May 2008, . [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, October 2013, . [RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March 2014, . [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained Application Protocol (CoAP)", RFC 7252, DOI 10.17487/RFC7252, June 2014, . [RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May 2015, . [RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)", RFC 7516, DOI 10.17487/RFC7516, May 2015, . [RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, . Wahlstroem, et al. Expires January 8, 2017 [Page 11] Internet-Draft CBOR Web Token July 2016 8.2. Informative References [I-D.seitz-ace-oauth-authz] Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and H. Tschofenig, "Authorization for the Internet of Things using OAuth 2.0", draft-seitz-ace-oauth-authz-00 (work in progress), October 2015. Appendix A. Examples Three examples of CWTs follow. A.1. CWT with "aud" and symmetric key A CWT used in the context of ACE requires at least the "aud" and a "cks" claim (defined elsewhere). This means that "iss", "alg", "key_ops" and others are pre-established and assumed. This would look like this non-normative JSON. { "aud":"coap://light.example.com", "cks": [ // COSE_Key is a CBOR map with an array of keys { "kty":4, // symmetric key is indicated using kty 4 "k": "loremipsum" // the symmetric key } ] } Figure 2: "aud" claim and symmetric key in non-normative JSON Using the CBOR encoded claim keys according to Section 4 and COSE [I-D.ietf-cose-msg] makes a CWT with "aud" and a symmetric key look like this in CBOR diagnostic notation: Wahlstroem, et al. Expires January 8, 2017 [Page 12] Internet-Draft CBOR Web Token July 2016 { 3: "coap://light.example.com", 8: [ { 1: 4, -1: "loremipsum" } ] } Figure 3: CWT in CBOR diagnostic notation Defined in CBOR. a2 # map(2) 03 # unsigned(3) 78 18 # text(24) 636f61703a2f2f6c696768742e6578616d706c652e636f6d # "coap://light.example.com" 08 # unsigned(8) 81 # array(1) a2 # map(2) 01 # unsigned(1) 04 # unsigned(4) 20 # negative(0) 6a # text(10) 6c6f72656d697073756d # "loremipsum" Figure 4: CWT with "aud" and symmetric key in CBOR Size of the CWT with a symmetric key of 10 bytes is 45 bytes. This is then packaged signed and encrypted using COSE. A.2. CWT with "aud" and EC key Token with "aud" set to "coap://light.example.com" and an EC key with "kid" set to "11". Wahlstroem, et al. Expires January 8, 2017 [Page 13] Internet-Draft CBOR Web Token July 2016 { "aud": "coap://light.example.com", "cks": [ // COSE_Key is a CBOR map with an array of keys { "kty": "EC", "kid": "11", "crv": 1, // using P-384 "x": h'bac5b11cad8f99f9c72b05cf4b9e26d244dc189f745228255a219a86d6a09eff', "y": h'20138bf82dc1b6d562be0fa54ab7804a3a64b6d72ccfed6b6fb6ed28bbfc117e' } ] } Figure 5: "aud" claim and EC key in non-normative JSON Using the CBOR encoded claim keys according to Section 4 and COSE [I-D.ietf-cose-msg] makes a CWT with "aud" and an EC key look like this in CBOR diagnostic notation: { 3: "coap://light.example.com", 8: [ { 1: 2, 2: "11", -1: 1, -2: h'bac5b11cad8f99f9c72b05cf4b9e26d244dc189f745228255a219a86d6a09eff', -3: h'20138bf82dc1b6d562be0fa54ab7804a3a64b6d72ccfed6b6fb6ed28bbfc117e' } ] } Figure 6: CWT with EC key in CBOR diagnostic notation Defined in CBOR. Wahlstroem, et al. Expires January 8, 2017 [Page 14] Internet-Draft CBOR Web Token July 2016 a2 # map(2) 03 # unsigned(3) 78 18 # text(24) 636f61703a2f2f6c696768742e6578616d706c652e636f6d # "coap://light.example.com" 08 # unsigned(8) 81 # array(1) a5 # map(5) 01 # unsigned(1) 02 # unsigned(2) 02 # unsigned(2) 62 # text(2) 3131 # "11" 20 # negative(0) 01 # unsigned(1) 21 # negative(1) 58 20 # bytes(32) bac5b11cad8f99f9c72b05cf4b9e26d244dc189f745228255a219a86d6a09eff # "\xBA\xC5\xB1\x1C\xAD\x8F\x99\xF9\xC7+\x05\xCFK\x9E&\xD2D\xDC\x18\x9FtR(%Z!\x9A\x86\xD6\xA0\x9E\xFF" 22 # negative(2) 58 20 # bytes(32) 20138bf82dc1b6d562be0fa54ab7804a3a64b6d72ccfed6b6fb6ed28bbfc117e # "\x13\x8B\xF8-\xC1\xB6\xD5b\xBE\x0F\xA5J\xB7\x80J:d\xB6\xD7,\xCF\xEDko\xB6\xED(\xBB\xFC\x11~" Figure 7: CWT with EC in CBOR Size of the CWT with an EC key is 109 bytes. This is then packaged signed and encrypted using COSE. A.3. Full CWT CWT using all claims defined by this specification, plus extensions for AIF and an EC key. Wahlstroem, et al. Expires January 8, 2017 [Page 15] Internet-Draft CBOR Web Token July 2016 { "iss": "coap://as.example.com", "aud": "coap://light.example.com", "sub": "erikw", "exp": 1444064944, "nbf": 1443944944, "iat": 1443944944, "cti": 2929, "cks": [ // COSE_Key is a CBOR map with an array of keys { "kty": "EC", "kid": "11", "crv": 1, // using P-384 "x": h'bac5b11cad8f99f9c72b05cf4b9e26d244dc189f745228255a219a86d6a09eff', "y": h'20138bf82dc1b6d562be0fa54ab7804a3a64b6d72ccfed6b6fb6ed28bbfc117e' } ], "aif": [["/s/light", 1], ["/a/led", 5], ["/dtls", 2]] } Figure 8: All claims, "aif" and EC key in non-normative JSON Using the CBOR encoded claim keys according to Section 4 and COSE [I-D.ietf-cose-msg] makes a full CWT look like this in CBOR diagnostic notation: Wahlstroem, et al. Expires January 8, 2017 [Page 16] Internet-Draft CBOR Web Token July 2016 { 1: "coap://as.example.com", 3: "coap://light.example.com", 2: "erikw", 4: 1(1444064944), 5: 1(1443944944), 6: 1(1443944944), 7: 2929, 8: [ { 1: 2, 2: "11", -1: 1, -2: h'bac5b11cad8f99f9c72b05cf4b9e26d244dc189f745228255a219a86d6a09eff', -3: h'20138bf82dc1b6d562be0fa54ab7804a3a64b6d72ccfed6b6fb6ed28bbfc117e' } ], 9: [["/s/light", 1], ["/a/led", 5], ["/dtls", 2]] } Figure 9: Full CWT with EC key in CBOR diagnostic notation Defined in CBOR. a9 # map(9) 01 # unsigned(1) 75 # text(21) 636f61703a2f2f61732e6578616d706c652e636f6d # "coap://as.example.com" 03 # unsigned(3) 78 18 # text(24) 636f61703a2f2f6c696768742e6578616d706c652e636f6d # "coap://light.example.com" 02 # unsigned(2) 65 # text(5) 6572696b77 # "erikw" 04 # unsigned(4) c1 # tag(1) 1a 5612aeb0 # unsigned(1444064944) 05 # unsigned(5) c1 # tag(1) 1a 5610d9f0 # unsigned(1443944944) 06 # unsigned(6) c1 # tag(1) 1a 5610d9f0 # unsigned(1443944944) 07 # unsigned(7) 19 0b71 # unsigned(2929) 08 # unsigned(8) Wahlstroem, et al. Expires January 8, 2017 [Page 17] Internet-Draft CBOR Web Token July 2016 81 # array(1) a5 # map(5) 01 # unsigned(1) 02 # unsigned(2) 02 # unsigned(2) 62 # text(2) 3131 # "11" 20 # negative(0) 01 # unsigned(1) 21 # negative(1) 58 20 # bytes(32) bac5b11cad8f99f9c72b05cf4b9e26d244dc189f745228255a219a86d6a09eff # "\xBA\xC5\xB1\x1C\xAD\x8F\x99\xF9\xC7+\x05\xCFK\x9E&\xD2D\xDC\x18\x9FtR(%Z!\x9A\x86\xD6\xA0\x9E\xFF" 22 # negative(2) 58 20 # bytes(32) 20138bf82dc1b6d562be0fa54ab7804a3a64b6d72ccfed6b6fb6ed28bbfc117e # "\x13\x8B\xF8-\xC1\xB6\xD5b\xBE\x0F\xA5J\xB7\x80J:d\xB6\xD7,\xCF\xEDko\xB6\xED(\xBB\xFC\x11~" 09 # unsigned(9) 83 # array(3) 82 # array(2) 68 # text(8) 2f732f6c69676874 # "/s/light" 01 # unsigned(1) 82 # array(2) 66 # text(6) 2f612f6c6564 # "/a/led" 05 # unsigned(5) 82 # array(2) 65 # text(5) 2f64746c73 # "/dtls" 02 # unsigned(2) Figure 10: Full CWT with EC in CBOR Size of the CWT with an EC key is 194 bytes. This is then packaged signed and encrypted using COSE. Appendix B. Acknowledgements This specification is based on JSON Web Token (JWT) [RFC7519], the authors of which also include Nat Sakimura and John Bradley. A straw man proposal of CWT was written in the draft "Authorization for the Internet of Things using OAuth 2.0" [I-D.seitz-ace-oauth-authz] with the help of Ludwig Seitz and Goeran Selander. Wahlstroem, et al. Expires January 8, 2017 [Page 18] Internet-Draft CBOR Web Token July 2016 Appendix C. Document History [[ to be removed by the RFC Editor before publication as an RFC ]] -01 o Added IANA registration for CWT Claims. o Added IANA registration for the application/cwt CoAP content- format type. o Added Samuel Erdtman as an editor. o Changed Erik's e-mail address. -00 o Created the initial working group version based on draft- wahlstroem-ace-cbor-web-token-00. Authors' Addresses Erik Wahlstroem Sweden Email: erik@wahlstromstekniska.se Michael B. Jones Microsoft Email: mbj@microsoft.com URI: http://self-issued.info/ Hannes Tschofenig ARM Ltd. Hall in Tirol 6060 Austria Email: Hannes.Tschofenig@arm.com Samuel Erdtman Spotify AB Birger Jarlsgatan 61, 4tr Stockholm 113 56 Sweden Phone: +46702691499 Email: erdtman@spotify.com Wahlstroem, et al. Expires January 8, 2017 [Page 19]