JSON Proof Algorithms

Internet-Draft	json-proof-algorithms	April 2025
Jones, et al.	Expires 10 October 2025	[Page]

Abstract

The JSON Proof Algorithms (JPA) specification registers cryptographic algorithms and identifiers to be used with the JSON Web Proof, JSON Web Key (JWK), and COSE specifications. It defines IANA registries for these identifiers.¶

6. Algorithm Specifications

This section defines how to use specific algorithms for JWPs.¶

6.1. Single Use

The Single Use (SU) algorithm is based on composing multiple traditional asymmetric signatures into a single JWP proof. It enables a very simple form of selective disclosure without requiring any advanced cryptographic techniques.¶

It does not support unlinkability if the same JWP is presented multiple times, therefore when privacy is required the holder will need to interact with the issuer again to receive new single-use JWPs (dynamically or in batches).¶

6.1.1. JWS Algorithm

The Single Use algorithm is based on using multiple signatures to cover the individual payloads, all of which are generated with the same Asymmetric JSON Web Algorithm (JWA). The internal signing algorithm to use is part of the registration for a new Single Use algorithm identifier.¶

The chosen JWA MUST be an asymmetric signing algorithm so that each signature can be verified without sharing any private values between the parties. This ensures that the verifier cannot brute force any non-disclosed payloads based only on their disclosed individual signatures.¶

6.1.2. Holder Setup

In order to support the protection of a presentation by a holder to a verifier, the holder MUST use a Presentation Key during the issuance and the presentation of every Single Use JWP. This Presentation Key MUST be generated and used for only one JWP.¶

The issuer MUST verify that the holder has possession of this key. The holder-issuer communication to exchange this information is out of scope of this specification, but can be accomplished by the holder using this key to generate a JWS that signs a value the issuer can verify as unique.¶

6.1.3. Issuer Setup

To create a Single Use JWP, the issuer first generates a unique Ephemeral Key using the selected internal algorithm. This key-pair will be used to sign each of the payloads of a single JWP and then discarded.¶

6.1.4. Signing payloads

Each individual payload is signed using the selected internal algorithm using the Ephemeral Key.¶

6.1.5. Issuer Protected Header

The issuer's Ephemeral Key MUST be included in the issuer protected header via the Proof Key header parameter.¶

The holder's Presentation Key MUST be included in issuer protected header via the Presentation Key header parameter.¶

The issuer protected header is signed using the given JWA and the issuer's Stable Key.¶

6.1.6. Payloads

Each JWP payload is processed in order and signed using the given JWA using the issuer's Ephemeral Key.¶

6.1.7. Proof

The proof value is an octet string array. The first entry is the octet string of the issuer protected header signature, with an additional entry for each payload signature.¶

6.1.8. Presentation Protected Header

To generate a new presentation, the holder first creates a presentation protected header that is specific to the verifier being presented to. This header MUST contain a parameter that both the holder and verifier trust as being unique and non-replayable. Use of the nonce header parameter is RECOMMENDED for this purpose.¶

This specification registers the nonce header parameter for the presentation protected header that contains a string value either generated by the verifier or derived from values provided by the verifier. When present, the verifier MUST ensure the nonce value matches during verification.¶

The presentation protected header MAY contain other header parameters that are either provided by the verifier or by the holder. These presentation header parameters SHOULD NOT contain values that are common across multiple presentations and SHOULD be unique to a single presentation and verifier.¶

6.1.9. Presentation

Editor's Note: The current definition here is incomplete, the holder's signature needs to also incorporate the presented proof.¶

The holder derives a new proof as part of presentation. The presented proof value will always contain the issuer's Stable Key signature for the issuer protected header as the first element.¶

The second element of the presented proof is the holder's signature of the presentation protected header using the holder's presentation key. This signature is constructed using the same algorithm described in generating the issuer's signature over the issuer protected header. Signing only the presentation header with the Presentation Key is sufficient to protect the entire presentation since that key is private to the holder and only the contents of the presentation header are used for replay prevention.¶

For each payload which is to be disclosed, the corresponding payload signature (from the issued JWP) is included in the proof. If a payload is omitted from the presented JWP, the signature value will NOT be includeed, and the presentation proof will have one less part.¶

For example, if the second and fifth of five payloads are not disclosed, then the holder's derived proof would consist of the issuer's signature over the issuer protected header, the holder's signature over the holder's protected header, the ephemeral key signature over the first, third and fourth payloads.¶

Since the individual signatures in the proof value are unique and remain unchanged across multiple presentations, a Single Use JWP SHOULD only be presented a single time to each verifier in order for the holder to remain unlinkable across multiple presentations.¶

6.1.10. Verification

The verifier MUST verify the issuer protected header octets against the first part in the proof using the issuer's Stable Key. It MUST also verify the presentation protected header octets against the second part in the proof value using the holder's Presentation Key, as provided in the Presentation Key header parameter.¶

With the headers verified, the Proof Key header parameter can then be used to verify each of the disclosed payload signatures.¶

6.1.11. JPA Registration

The proposed JWP alg value is of the format "SU-" appended with the relevant JWS alg value for the chosen public and ephemeral key-pair algorithm, for example "SU-ES256".¶

6.2. BBS

The BBS Signature Scheme [I-D.irtf-cfrg-bbs-signatures] is under active development within the CRFG.¶

This algorithm supports both selective disclosure and unlinkability, enabling the holder to generate multiple presentations from one issued JWP without a verifier being able to correlate those presentations together based on the proof.¶

6.2.1. JPA Algorithms

The BBS algorithm corresponds to a ciphersuite identifier of BBS_BLS12381G1_XMD:SHA-256_SSWU_RO_.¶

6.2.2. Key Format

The key used for the BBS algorithm is an elliptic curve-based key pair, specifically against the G_2 subgroup of a pairing friendly curve. Additional details on key generation can be found in Section 3.4. The JWK and Cose Key Object representations of the key are detailed in [I-D.ietf-cose-bls-key-representations].¶

There is no additional holder presentation key necessary for presentation proofs.¶

6.2.3. Issuance

Issuance is performed using the Sign operation from Section 3.5.1 of [I-D.irtf-cfrg-bbs-signatures]. This operation utilizes the issuer's BLS12-381 G2 key pair as SK and PK, along with desired protected header and payloads as the octets header and the octets array messages.¶

The octets resulting from this operation form a single octet string in the issuance proof array, to be used along with the protected header and payloads to serialize the JWP.¶

6.2.4. Issuance Proof Verification

Holder verification of the signature on issuance form is performed using the Verify operation from Section 3.5.2 of [I-D.irtf-cfrg-bbs-signatures].¶

This operation utilizes the issuer's public key as PK, the proof as signature, the protected header octets as header and the array of payload octets as messages.¶

6.2.5. Presentation

Derivation of a presentation is done by the holder using the ProofGen operation from Section 3.5.3 of [I-D.irtf-cfrg-bbs-signatures].¶

This operation utilizes the issuer's public key as PK, the issuer protected header as header, the issuance proof as signature, the issuance payloads as messages, and the holder's presentation protected header as ph.¶

The operation also takes a vector of indexes into messages, describing which payloads the holder wishes to disclose. All payloads are required for proof generation, but only these indicated payloads will be required to be disclosed for later proof verification.¶

The output of this operation is the presentation proof, as a single octet string.¶

Presentation serialization leverages the two protected headers and presentation proof, along with the disclosed payloads. Non-disclosed payloads are represented with the absent value of null in CBOR serialization and a zero-length string in compact serialization.¶

6.2.6. Presentation Verification

Verification of a presentation is done by the verifier using the ProofVerify operation from Section 3.5.4.¶

This operation utilizes the issuer's public key as PK, the issuer protected header as header, the issuance proof as signature, the holder's presentation protected header as ph, and the payloads as disclosed_messages.¶

In addition, the disclosed_indexes scalar array is calculated from the payloads provided. Values disclosed in the presented payloads have a zero-based index in this array, while the indices of absent payloads are omitted.¶

6.3. Message Authentication Code

The Message Authentication Code (MAC) JPA uses a MAC to both generate ephemeral keys and compute authentication codes to protect the issuer header and each payload individually.¶

Like the the Single Use algorithm family, it also does not support unlinkability if the same JWP is presented multiple times. and requires an individually issued JWP for each presentation in order to fully protect privacy. When compared to the JWS approach, using a MAC requires less computation but can result in potentially larger presentation proof values.¶

The design is intentionally minimal and only involves using a single standardized MAC method instead of a mix of MAC/hash methods or a custom hash-based construct. It is able to use any published cryptographic MAC method such as HMAC [RFC2104] or KMAC. It uses traditional public-key based signatures to verify the authenticity of the issuer and holder.¶

6.3.1. Holder Setup

Prior to the issuer creating a new JWP, the issuer MUST have a presentation public key provided by the holder.¶

The holder's presentation key MUST be included in the issuer's protected header using the Presentation Key header parameter.¶

6.3.2. Issuer Setup

To use the MAC algorithm, the issuer must have a stable public key pair to perform signing. To start the issuance process, a single 32-byte random Shared Secret must first be generated. This value will be shared privately to the holder as part of the issuer's JWP proof value.¶

The Shared Secret is used by both the issuer and holder as the MAC method's key to generate a new set of unique ephemeral keys. These keys are then used as the input to generate a MAC that protects each payload.¶

6.3.3. Combined MAC Representation

The combined MAC representation is a single octet string representing the MAC values of the issuer protected header, along with each payload provided by the issuer. This representation is signed by the issuer, but not shared - parties will recreate this octet string and verify the signature to verify the integrity of supplied issuer protected header and the integrity of any disclosed payloads.¶

The issuer protected header is included in this value as a MAC created using the fixed key "issuer_header" in UTF-8 encoded octets. The value is the issuer header JSON as a UTF-8 encoded octet string.¶

A unique key is generated for each payload using a MAC, with the Shared Secret as the key and a value of "payload_X" as UTF-8 encoded octets, where "X" is replaced by the zero-based array index of the payload, for example "payload_0", "payload_1", etc.¶

Each payload then itself has a corresponding MAC, using the above per-payload key and the payload octet string.¶

The combined MAC representation is the octet string formed by the the concatentation of the issuer protected header MAC output, along with each payload MAC output.¶

6.3.4. Issuer Proof

The issuer proof consists of two octet strings.¶

The first octet string is the issuer signature over the combined MAC representation. The issuer signs the JWS using its stable public key, and a fixed header containing the alg associated with signing algorithm in use.¶

jws_header = '{"alg":"ES256"}'¶

The signature value of the JWS is extracted and base64url-decoded into an octet string.¶

The second octet string is the Shared Secret used to generate the per-payload keys for the combined representation.¶

6.3.5. Presentation Protected Header

See the JWS Presentation Protected Header section.¶

6.3.6. Presentation Proof

Editor's Note: The current definition here is incomplete, the holder's signature needs to also incorporate the presented proof.¶

The first value in the presentation proof is the presentation signature. This is a signature over the presentation protected header, using the key specified by the Presentation Key header parameter in the issuer protected header.¶

The second value is the issuer signature over the Combined MAC Representation provided with the issued form.¶

The remaining values are used by the verifier to reconstruct the combined MAC representation without access to the Shared Secret. There is one value corresponding to each payload, whether it has been disclosed or not.¶

If a payload is disclosed, the unique per-payload key derived from the shared secret is used as the payload's entry in the proof array.¶

If a payload is not disclosed, the payload's MAC in the combined MAC representation is used as the payload's entry in the proof array.¶

6.3.7. Verification of the Presentation Proof

The verifier must recreate the Combined MAC Representation from the presentation proof to verify integrity over the disclosed information.¶

The issuer protected header MAC is recreated using the same mechanism described above.¶

For each payload in the presentation:¶

If the payload is disclosed, then the presentation proof contains the unique per-payload key. The corresponding payload MAC can be computed by performing the MAC operation with this key and the corresponding payload.¶
If the payload is not disclosed, then the presentation proof contains the payload MAC, which can be used directly¶

The concatenation of the octets of the issuer protected header MAC and each payload MAC forms the Combined MAC Representation. The issuer signature in the proof is then verified by converting these values to a JWS as described above, and verifying that JWS.¶

6.3.8. JPA Registration

Proposed JWP alg value is of the format "MAC-" appended with a unique identifier for the set of MAC and signing algorithms used. Below are the initial registrations:¶

MAC-H256 uses HMAC SHA-256 as the MAC and ECDSA using P-256 and SHA-256 for the signatures¶
MAC-H384 uses HMAC SHA-384 as the MAC and ECDSA using P-384 and SHA-384 for the signatures¶
MAC-H512 uses HMAC SHA-512 as the MAC and ECDSA using P-521 and SHA-512 for the signatures¶
MAC-K25519 uses KMAC SHAKE128 as the MAC and EdDSA using Curve25519 for the signatures¶
MAC-K448 uses KMAC SHAKE256 as the MAC and EdDSA using Curve448 for the signatures¶
MAC-H256K uses HMAC SHA-256 as the MAC and ECDSA using secp256k1 and SHA-256 for the signatures¶

8. IANA Considerations

The following registration procedure is used for all the registries established by this specification.¶

Values are registered on a Specification Required [RFC5226] basis after a three-week review period on the [email protected] mailing list, 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.¶

Registration requests sent to the mailing list for review should use an appropriate subject (e.g., "Request to register JWP algorithm: example").¶

Within the review period, the Designated Experts will either approve or deny the registration request, communicating this decision to the review list and IANA. Denials should include an explanation and, if applicable, suggestions as to how to make the request successful. Registration requests that are undetermined for a period longer than 21 days can be brought to the IESG's attention (using the [email protected] mailing list) for resolution.¶

Criteria that should be applied by the Designated Experts include determining whether the proposed registration duplicates existing functionality, whether it is likely to be of general applicability or useful only for a single application, and whether the registration description is clear.¶

IANA must only accept registry updates from the Designated Experts and should direct all requests for registration to the review mailing list.¶

It is suggested that multiple Designated Experts be appointed who are able to represent the perspectives of different applications using this specification, in order to enable broadly informed review of registration decisions. In cases where a registration decision could be perceived as creating a conflict of interest for a particular Expert, that Expert should defer to the judgment of the other Experts.¶

8.1. JSON Web Proof Algorithms Registry

This specification establishes the IANA "JSON Web Proof Algorithms" registry for values of the JWP alg (algorithm) parameter in JWP Header Parameters. The registry records the algorithm name, the algorithm description, the algorithm usage locations, the implementation requirements, the change controller, and a reference to the specification that defines it. The same algorithm name can be registered multiple times, provided that the sets of usage locations are disjoint.¶

It is suggested that the length of the key be included in the algorithm name when multiple variations of algorithms are being registered that use keys of different lengths and the key lengths for each need to be fixed (for instance, because they will be created by key derivation functions). This allows readers of the JSON text to more easily make security decisions.¶

The Designated Experts should perform reasonable due diligence that algorithms being registered either are currently considered cryptographically credible or are being registered as Deprecated or Prohibited.¶

The implementation requirements of an algorithm may be changed over time as the cryptographic landscape evolves, for instance, to change the status of an algorithm to Deprecated or to change the status of an algorithm from Optional to Recommended+ or Required. Changes of implementation requirements are only permitted on a Specification Required basis after review by the Designated Experts, with the new specification defining the revised implementation requirements level.¶

8.1.1. Registration Template

Algorithm Name:: Brief descriptive name of the algorithm (e.g., Single-Use JWP using ES256.) Descriptive names may not match other registered names unless the Designated Experts state that there is a compelling reason to allow an exception.¶
Algorithm JSON Label:: The string label requested (e.g., SU-ES256). This label is a case-sensitive ASCII string. JSON Labels may not match other registered labels in a case-insensitive manner unless the Designated Experts state that there is a compelling reason to allow an exception.¶
Algorithm CBOR Label:: The integer label requested (e.g. 1). CBOR Labels may not match other registered labels unless the Designated Experts state that there is a compelling reason to allow an exception.¶
Algorithm Description:: Optional additional information clarifying the algorithm. This may be used for example to document additional chosen parameters.¶
Algorithm Usage Location(s):: The algorithm usage locations, which should be one or more of the values Issued or Presented. Other values may be used with the approval of a Designated Expert.¶
JWP Implementation Requirements:: The algorithm implementation requirements for JWP, which must be one the words Required, Recommended, Optional, Deprecated, or Prohibited. Optionally, the word can be followed by a + or -. The use of + indicates that the requirement strength is likely to be increased in a future version of the specification. The use of - indicates that the requirement strength is likely to be decreased in a future version of the specification. Any identifiers registered for algorithms that are otherwise unsuitable for direct use as JWP algorithms must be registered as Prohibited.¶
Change Controller:: For Standards Track RFCs, list the "IETF". 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.¶
Algorithm Analysis Documents(s):: References to a publication or publications in well-known cryptographic conferences, by national standards bodies, or by other authoritative sources analyzing the cryptographic soundness of the algorithm to be registered. The Designated Experts may require convincing evidence of the cryptographic soundness of a new algorithm to be provided with the registration request unless the algorithm is being registered as Deprecated or Prohibited. Having gone through working group and IETF review, the initial registrations made by this document are exempt from the need to provide this information.¶

8.1.2. Initial Registry Contents

8.1.2.1. Single-Use JWP using ES256 Algorithm

Algorithm Name: Single-Use JWP using ES256¶
Algorithm JSON Label: SU-ES256¶
Algorithm CBOR Label: 1¶
Algorithm Usage Location(s): Issued, Presented¶
JWP Implementation Requirements: Recommended¶
Change Controller: IETF¶
Specification Document(s): Section 6.1.11 of this specification¶
Algorithm Analysis Documents(s): n/a¶

8.1.2.2. Single-Use JWP using ES384 Algorithm

Algorithm Name: Single-Use JWP using ES384¶
Algorithm JSON Label: SU-ES384¶
Algorithm CBOR Label: 2¶
Algorithm Usage Location(s): Issued, Presented¶
JWP Implementation Requirements: Optional¶
Change Controller: IETF¶
Specification Document(s): Section 6.1.11 of this specification¶
Algorithm Analysis Documents(s): n/a¶

8.1.2.3. Single-Use JWP using ES512 Algorithm

Algorithm Name: Single-Use JWP using ES512¶
Algorithm JSON Label: SU-ES512¶
Algorithm CBOR Label: 3¶
Algorithm Usage Location(s): Issued, Presented¶
JWP Implementation Requirements: Optional¶
Change Controller: IETF¶
Specification Document(s): Section 6.1.11 of this specification¶
Algorithm Analysis Documents(s): n/a¶

8.1.2.4. BBS using SHA-256 Algorithm

Algorithm Name: BBS using SHA-256¶
Algorithm JSON Label: BBS¶
Algorithm CBOR Label: 4¶
Algorithm Description: Corresponds to a ciphersuite identifier of BBS_BLS12381G1_XMD:SHA-256_SSWU_RO_H2G_HM2S_¶
Algorithm Usage Location(s): Issued, Presented¶
JWP Implementation Requirements: Required¶
Change Controller: IETF¶
Specification Document(s): Section 6.2.1 of this specification¶
Algorithm Analysis Documents(s): n/a¶

8.1.2.5. MAC-H256 Algorithm

Algorithm Name: MAC-H256¶
Algorithm JSON Label: MAC-H256¶
Algorithm CBOR Label: 5¶
Algorithm Description: MAC-H256 uses HMAC SHA-256 as the MAC, and ECDSA using P-256 and SHA-256 for the signatures¶
Algorithm Usage Location(s): Issued, Presented¶
JWP Implementation Requirements: Optional¶
Change Controller: IETF¶
Specification Document(s): Section 6.3.8 of this specification¶
Algorithm Analysis Documents(s): n/a¶

8.1.2.6. MAC-H384 Algorithm

Algorithm Name: MAC-H384¶
Algorithm JSON Label: MAC-H384¶
Algorithm CBOR Label: 6¶
Algorithm Description: MAC-H384 uses HMAC SHA-384 as the MAC, and ECDSA using P-384 and SHA-384 for the signatures¶
Algorithm Usage Location(s): Issued, Presented¶
JWP Implementation Requirements: Optional¶
Change Controller: IETF¶
Specification Document(s): Section 6.3.8 of this specification¶
Algorithm Analysis Documents(s): n/a¶

8.1.2.7. MAC-H512 Algorithm

Algorithm Name: MAC-H512¶
Algorithm JSON Label: MAC-H512¶
Algorithm CBOR Label: 7¶
Algorithm Description: MAC-H512 uses HMAC SHA-512 as the MAC, and ECDSA using P-521 and SHA-512 for the signatures¶
Algorithm Usage Location(s): Issued, Presented¶
JWP Implementation Requirements: Optional¶
Change Controller: IETF¶
Specification Document(s): Section 6.3.8 of this specification¶
Algorithm Analysis Documents(s): n/a¶

8.1.2.8. MAC-K25519 Algorithm

Algorithm Name: MAC-K25519¶
Algorithm JSON Label: MAC-K25519¶
Algorithm CBOR Label: 8¶
Algorithm Description: MAC-K25519 uses KMAC SHAKE128 as the MAC, and EdDSA using Curve25519 for the signatures¶
Algorithm Usage Location(s): Issued, Presented¶
JWP Implementation Requirements: Optional¶
Change Controller: IETF¶
Specification Document(s): Section 6.3.8 of this specification¶
Algorithm Analysis Documents(s): n/a¶

8.1.2.9. MAC-K448 Algorithm

Algorithm Name: MAC-K448¶
Algorithm JSON Label: MAC-K448¶
Algorithm CBOR Label: 9¶
Algorithm Description: MAC-K448 uses KMAC SHAKE256 as the MAC, and EdDSA using Curve448 for the signatures¶
Algorithm Usage Location(s): Issued, Presented¶
JWP Implementation Requirements: Optional¶
Change Controller: IETF¶
Specification Document(s): Section 6.3.8 of this specification¶
Algorithm Analysis Documents(s): n/a¶

8.1.2.10. MAC-H256K Algorithm

Algorithm Name: MAC-H256K¶
Algorithm JSON Label: MAC-H256K¶
Algorithm CBOR Label: 10¶
Algorithm Description: MAC-H256K uses HMAC SHA-256 as the MAC, and ECDSA using secp256k1 and SHA-256 for the signatures¶
Algorithm Usage Location(s): Issued, Presented¶
JWP Implementation Requirements: Optional¶
Change Controller: IETF¶
Specification Document(s): Section 6.3.8 of this specification¶
Algorithm Analysis Documents(s): n/a¶

Appendix A. Example JWPs

The following examples use algorithms defined in JSON Proof Algorithms and also contain the keys used, so that implementations can validate these samples.¶

A.1. Example JSON-Serialized Single-Use JWP

This example uses the Single-Use Algorithm as defined in JSON Proof Algorithms to create a JSON Proof Token. It demonstrates how to apply selective disclosure using an array of traditional JWS-based signatures. Unlinkability is only achieved by using each JWP one time, as multiple uses are inherently linkable via the traditional ECDSA signature embedded in the proof.¶

To begin, we need two asymmetric keys for Single Use: one that represents the JPT Issuer's stable key and the other is an ephemeral key generated by the Issuer just for this JWP.¶

This is the Issuer's stable private key used in this example in the JWK format:¶

{
  "kty": "EC",
  "crv": "P-256",
  "x": "P98A5H6nXHfjyRNIG3WTZX5tShfK-eJG24HOCvj1qEM",
  "y": "ZdgxfASS-hTXEnAIvYnI0aSz2WenHQOgP3J43Gjzl_c",
  "d": "zbqFoMVyw_A7uQFvsJORLPxXCI4GiwZBvXxxsOCIR0o"
}

Figure 1: Issuer Private Key (ES256 in JWK)

This is the ephemeral private key used in this example in the JWK format:¶

{
  "kty": "EC",
  "crv": "P-256",
  "x": "Xb5mt8IT26iNL7feuxx0zq_FCNyeSPlMwv8y4qyvrIU",
  "y": "Hdj6TpAT8b8L0IXDANAZXcKlyu6e4FgQPpUU5ziGrAg",
  "d": "F8AAvN-AHaX1GDnPiSpvJFSz67laSUL7NSGMUj16Hh4"
}

Figure 2: Issuer Ephemeral Private Key (ES256 in JWK)

This is the Holder's presentation private key used in this example in the JWK format:¶

{
  "kty": "EC",
  "crv": "P-256",
  "x": "Mvndw9DGgODdNLiEQ-rqpTI2wZ5LKeQfbVRKSmlgv1g",
  "y": "VohB6ZcAiCo0P2F09JAqI1XdciZaglYDo0lAwuqygCQ",
  "d": "mnIjF4G3hihDqSWvwwND1RB_TJj_0FpsaXFV1EJOMVs"
}

Figure 3: Holder Presentation Private Key (ES256 in JWK)

The JWP Protected Header declares that the data structure is a JPT and the JWP Proof Input is secured using the Single-Use ECDSA algorithm with the P-256 curve and SHA-256 digest. It also includes the ephemeral public key, the Holder's presentation public key and list of claims used for this JPT.¶

{
  "alg": "SU-ES256",
  "typ": "JPT",
  "iss": "https://issuer.example",
  "claims": [
    "iat",
    "exp",
    "family_name",
    "given_name",
    "email",
    "address",
    "age_over_21"
  ],
  "proof_key": {
    "kty": "EC",
    "crv": "P-256",
    "x": "Xb5mt8IT26iNL7feuxx0zq_FCNyeSPlMwv8y4qyvrIU",
    "y": "Hdj6TpAT8b8L0IXDANAZXcKlyu6e4FgQPpUU5ziGrAg"
  },
  "presentation_key": {
    "kty": "EC",
    "crv": "P-256",
    "x": "Mvndw9DGgODdNLiEQ-rqpTI2wZ5LKeQfbVRKSmlgv1g",
    "y": "VohB6ZcAiCo0P2F09JAqI1XdciZaglYDo0lAwuqygCQ"
  }
}

Figure 4: Issuer Protected header (SU-ES256, JSON)
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Figure 5: Encoded Issuer Protected Header (SU-ES256, JSON, encoded)

The Single Use algorithm utilizes multiple individual JWS Signatures. Each signature value is generated by creating a JWS with a single Protected Header with the associated alg value. In this example, the fixed header used for each JWS is the serialized JSON Object {"alg":"ES256"}. This protected header will be used to generate a signature over each corresponding payload in the JWP. The corresponding octet value in the proof is the octet string (base64url-decoded) value of the signature.¶

The final proof value from the Issuer is an array with the octets of the header signature, followed by entries for each payload signature.¶

[
    1714521600,
    1717199999,
    "Doe",
    "Jay",
    "[email protected]",
    {
        "formatted": "1234 Main St.\nAnytown, CA 12345\nUSA",
        "street_address": "1234 Main St.",
        "locality": "Anytown",
        "region": "CA",
        "postal_code": 12345,
        "country": "USA"
    },
    true
]

Figure 6: Issuer payloads (JSON, as array)

The compact serialization of the same JPT is:¶
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.MTcxNDUyMTYwMA~MTcxNzE5OTk5OQ~IkRvZSI~IkpheSI~Imp
heWRvZUBleGFtcGxlLm9yZyI~eyJmb3JtYXR0ZWQiOiIxMjM0IE1haW4gU3QuXG5Bbnl0
b3duLCBDQSAxMjM0NVxuVVNBIiwic3RyZWV0X2FkZHJlc3MiOiIxMjM0IE1haW4gU3QuI
iwibG9jYWxpdHkiOiJBbnl0b3duIiwicmVnaW9uIjoiQ0EiLCJwb3N0YWxfY29kZSI6MT
IzNDUsImNvdW50cnkiOiJVU0EifQ~dHJ1ZQ.T69zblpucqbjz6wg5QTeTvI1crogVDm2m
3gkH_v1rr5KNPUv8wQamtaDstU0S-wSwpMEUcBKxOKgrWY6UqX9aQ~SuTUxAZ9Dd-gpA9
uxPYDfDrxqB9CFXH2wxd9ODf6ucqNsmks0Du3tAdLLgaPL7Dzxo1WxL6c1xhZb2fXNJPM
EA~67gfDB50veY1JzAQSJoH2bo7WJ4UtoTb7Al3YayCIzFEV1m4Ls0nOfUrwKTli-a3mI
B-xHvcJb33t-peqeGdqw~aYwyEzLSwOIn9b2b61sFXeFJKnSOw-cC7YYaBuw_nQ367PVe
B8HclZ2NJXSpVnLt7JGC88hyecgYPjvvK_ZZ1A~NdinVn7N_zhbicKxWMxslNaji89N0R
xU5zCzkQZyxweD8Em-Vw5__rrWkrjO2Wmopcihl_QIPdRKB2z4SFocEA~Q8lv3wGchn_m
FFUjs8hhZ8YJ0qdpZXnTEbnv_DMpZD5HBM6B_IRTJ10FD4ta8I7mPb9lU95-dvlv6obtl
hnj4Q~ZyCVmIVneNelUjb0-dTZGIfouH7WI_AUzMi-VsK1yLEypdV8E4xts5T4JVkEK_x
bRTA50sjKSvAH_9qCV3G6Xw~nrLmBw0Gr57iRt8lmJt9BD0j_UVhmInw5Zv6FP09eV4Rz
NOF-0jUzBl49k4wzwvUgPYowWttqbjA8pJjY7kouA

Figure 7: Issued JWP (SU-ES256, JSON, Compact Serialization)

To present this JPT, we first use the following presentation header with a nonce (provided by the Verifier):¶

{
  "alg": "SU-ES256",
  "aud": "https://recipient.example.com",
  "nonce": "H4iTRVLIsA5zKGwYTbIDfIDrj51KjCG1-XveKhdMQRA"
}

Figure 8: Presentation Header (SU-ES256, JSON)

eyJhbGciOiJTVS1FUzI1NiIsImF1ZCI6Imh0dHBzOi8vcmVjaXBpZW50LmV4YW1wbGUuY
29tIiwibm9uY2UiOiJINGlUUlZMSXNBNXpLR3dZVGJJRGZJRHJqNTFLakNHMS1YdmVLaG
RNUVJBIn0

Figure 9: Presentation Header (SU-ES256, JSON, Base64url-Encoded)

When signed with the holder's presentation key, the resulting signature are:¶

2vLbPzg9cRCRGklvfNaOp6yXRw2A4iMbO-CY5MDkg2F8Be2U_nw-OVSt38smp90BuvSY3
gTHVzjqHmLbhLTSUg

Figure: Holder Proof-of-Possession (SU-ES256, JSON)¶

Then by applying selective disclosure of only the given name and age claims (family name and email hidden), we get the following presented JPT in compact serialization:¶

eyJhbGciOiJTVS1FUzI1NiIsImF1ZCI6Imh0dHBzOi8vcmVjaXBpZW50LmV4YW1wbGUuY
29tIiwibm9uY2UiOiJINGlUUlZMSXNBNXpLR3dZVGJJRGZJRHJqNTFLakNHMS1YdmVLaG
RNUVJBIn0.eyJhbGciOiJTVS1FUzI1NiIsInR5cCI6IkpQVCIsImlzcyI6Imh0dHBzOi8
vaXNzdWVyLmV4YW1wbGUiLCJjbGFpbXMiOlsiaWF0IiwiZXhwIiwiZmFtaWx5X25hbWUi
LCJnaXZlbl9uYW1lIiwiZW1haWwiLCJhZGRyZXNzIiwiYWdlX292ZXJfMjEiXSwicHJvb
2Zfa2V5Ijp7Imt0eSI6IkVDIiwiY3J2IjoiUC0yNTYiLCJ4IjoiWGI1bXQ4SVQyNmlOTD
dmZXV4eDB6cV9GQ055ZVNQbE13djh5NHF5dnJJVSIsInkiOiJIZGo2VHBBVDhiOEwwSVh
EQU5BWlhjS2x5dTZlNEZnUVBwVVU1emlHckFnIn0sInByZXNlbnRhdGlvbl9rZXkiOnsi
a3R5IjoiRUMiLCJjcnYiOiJQLTI1NiIsIngiOiJNdm5kdzlER2dPRGROTGlFUS1ycXBUS
TJ3WjVMS2VRZmJWUktTbWxndjFnIiwieSI6IlZvaEI2WmNBaUNvMFAyRjA5SkFxSTFYZG
NpWmFnbFlEbzBsQXd1cXlnQ1EifX0.MTcxNDUyMTYwMA~MTcxNzE5OTk5OQ~IkRvZSI~I
kpheSI~ImpheWRvZUBleGFtcGxlLm9yZyI~eyJmb3JtYXR0ZWQiOiIxMjM0IE1haW4gU3
QuXG5Bbnl0b3duLCBDQSAxMjM0NVxuVVNBIiwic3RyZWV0X2FkZHJlc3MiOiIxMjM0IE1
haW4gU3QuIiwibG9jYWxpdHkiOiJBbnl0b3duIiwicmVnaW9uIjoiQ0EiLCJwb3N0YWxf
Y29kZSI6MTIzNDUsImNvdW50cnkiOiJVU0EifQ~dHJ1ZQ~~.T69zblpucqbjz6wg5QTeT
vI1crogVDm2m3gkH_v1rr5KNPUv8wQamtaDstU0S-wSwpMEUcBKxOKgrWY6UqX9aQ~2vL
bPzg9cRCRGklvfNaOp6yXRw2A4iMbO-CY5MDkg2F8Be2U_nw-OVSt38smp90BuvSY3gTH
VzjqHmLbhLTSUg~SuTUxAZ9Dd-gpA9uxPYDfDrxqB9CFXH2wxd9ODf6ucqNsmks0Du3tA
dLLgaPL7Dzxo1WxL6c1xhZb2fXNJPMEA~67gfDB50veY1JzAQSJoH2bo7WJ4UtoTb7Al3
YayCIzFEV1m4Ls0nOfUrwKTli-a3mIB-xHvcJb33t-peqeGdqw~aYwyEzLSwOIn9b2b61
sFXeFJKnSOw-cC7YYaBuw_nQ367PVeB8HclZ2NJXSpVnLt7JGC88hyecgYPjvvK_ZZ1A~
NdinVn7N_zhbicKxWMxslNaji89N0RxU5zCzkQZyxweD8Em-Vw5__rrWkrjO2Wmopcihl
_QIPdRKB2z4SFocEA~Q8lv3wGchn_mFFUjs8hhZ8YJ0qdpZXnTEbnv_DMpZD5HBM6B_IR
TJ10FD4ta8I7mPb9lU95-dvlv6obtlhnj4Q

Figure: Presentation (SU-ES256, JSON, Compact Serialization)¶

A.2. Example CBOR-Serialized Single-Use CPT

This example is meant to mirror the prior compact serialization, using RFC8392 and claims from [I-D.maldant-spice-oidc-cwt], illustrated using [I-D.ietf-cbor-edn-literals] (EDN).¶

To simplify this example, the same information is represented as the JPT example above, including the same public and private keys.¶

{          / protected header /
  1: 1,     / alg: "SU-ES256" /
  3: 20,    / typ: "JPT" (20CPA) /
  5: "https://issuer.example",  / iss: "https://issuer.example" /
  6: [      / claims /
    6,      / "iat" /
    4,      / "exp" /
    170,    / "family_name" (I-D.maldant-spice-oidc-cwt TBD1) /
    171,    / "given_name"  (I-D.maldant-spice-oidc-cwt TBD2) /
    179,    / "email"       (I-D.maldant-spice-oidc-cwt TBD10) /
    187,    / "address"     (I-D.maldant-spice-oidc-cwt TBD18) /
    "age_over_21"
  ],
  8: {      / proof key /
    1: 2,   / kty : "EC2" /
    -1: 1,  / crv: "P-256" /
    -2: h'32f9ddc3d0c680e0dd34b88443eaeaa53236c19e4b29e41f6d544a4a' +
        h'6960bf58', / x /
    -3: h'568841e99700882a343f6174f4902a2355dd72265a825603a34940c2' +
        h'eab28024'  / y /
  },
  9: {      / presentation key /
    1: 2,   / kty: "EC2" /
    -1: 1,  / crv: "P-256" /
    -2: h'5dbe66b7c213dba88d2fb7debb1c74ceafc508dc9e48f94cc2ff32e2' +
        h'acafac85', / x /
    -3: h'1dd8fa4e9013f1bf0bd085c300d0195dc2a5caee9ee058103e9514e7' +
        h'3886ac08'  / y /
  }
}

Figure: Issuer Protected Header (SU-ES256, CBOR)¶

[ / payloads    /
  / iat         / 171452160,
  / exp         / 171719999,
  / family_name / "Doe",
  / given_name  / "Jay",
  / email       / "[email protected]",
  / address     / {
    / formatted / 1: "1234 Main St.\nAnytown, CA 12345\nUSA",
    / street    / 2: "1234 Main St.",
    / locality  / 3: "Anytown",
    / region    / 4: "CA",
    / post code / 5: "90210",
    / country   / 6: "USA"
  },
  / age_over_21 / true
]

Figure: Issuer Payloads (as CBOR array)¶

When signed and serialized, the CPT is represented by the following CBOR (in hex):¶

8358cda601010314057668747470733a2f2f6973737565722e6578616d706c65
0687060418aa18ab18b318bb6b6167655f6f7665725f323108a4010220012158
2032f9ddc3d0c680e0dd34b88443eaeaa53236c19e4b29e41f6d544a4a6960bf
58225820568841e99700882a343f6174f4902a2355dd72265a825603a34940c2
eab2802409a4010220012158205dbe66b7c213dba88d2fb7debb1c74ceafc508
dc9e48f94cc2ff32e2acafac852258201dd8fa4e9013f1bf0bd085c300d0195d
c2a5caee9ee058103e9514e73886ac08871a0a3827001a0a3c3d3f63446f6563
4a6179726a6179646f65406578616d706c652e6f7267a601782331323334204d
61696e2053742e0a416e79746f776e2c2043412031323334350a555341026d31
323334204d61696e2053742e0367416e79746f776e0462434105653930323130
0663555341f5885840dfcca036447142876c5894a96ecb67db496e617d4e1b8b
c442d7d5107207562b5f39257703de217f9cac843273f19892e07f83c8f1d21b
f60fe4fc0ac029d406584004bd7aa9d8ff8a4ff57acf366f4aed8d5d220a9273
b2de9e866a49860b447d0a29fdd4d1341248987c69109c40507af98126e70685
2e1677639ce0ebcbbc62125840bba2ba271dac547609417b3cc6403d4df446e6
84dee27b39312a5ca9c4cde8ad52f4755c01295a3e614c0b461120f637f1c788
ffd467f590363a8a6c18ed4de258407d1ddfcd6e30111732258ee67a3ff7f1cd
14c0c940593f3486b6d884fbfa9a064714f0a6d71aa04b1edc3efe476fa2c664
fa0cd52ed060693b0a7ca456b820c25840e5feca083f5aba8f7311dd8ff5260b
e41532fec972b8fbd08a55674a8552b2422a1841d11436afa5add37198661a79
cb06376d2d64676901e1ff268fcc5668d45840a288d49c633e5a0c0f3e575d83
a4d40c9f693ebe4551954e3d031f70ace40ea0c635928e5dbe20f227ebbf1ddb
4db0397ea591a40067e1ae09fbb70a3717f2f45840425204215811b98ec30ff2
57bb2ad97ed4b4d5cf8cdb0362f7c573e19bf1af007b09d030407532b5bd87f2
61a72c372a04c8a75182be293994f5e8d52c41a2895840cf4303b9b41fa2a24a
a2bcc491731ff76da149a071d6bee046226478b99aa117b7ae66993b65890a45
762ba05f8256ba5ccba67d782fd2dc843ec97c4043a022

Fixtures: Issued Form (SU-ES256, CBOR)¶

The presented form, similarly to the issued form above, is made with the holder conveying the same parameters and the same set of selectively disclosed payloads as the JPT above:¶

{          / protected header /
  1: 1,    / alg: "SU-ES256" /
  6: "https://recipient.example.com", / aud /
  7: h'1f88934552c8b00e73286c184db2037c80eb8f9d4a8c21b5f97bde2a174c4110', / nonce /
}

Figure: Holder Protected Header (SU-ES256, CBOR)¶

When the appropriate proof is generated, the CPT is serialized into the following CBOR (in hex):¶
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Figure: Presented Form (SU-ES256, CBOR)¶

A.3. Example BBS JWP

The following example uses the BBS algorithm.¶

This is the Issuer's stable private key in the JWK format:¶

{
  "kty": "EC2",
  "alg": "BBS",
  "use": "proof",
  "crv": "BLS12381G2",
  "x": "Fa_0zEJCeiUtDMYqi_Ze1VIgKDMJBxdmpC9Ky0li-4OU0VKHf97thxy2W_PIP
       s3IFoa79wBsXv54zB7k90dyvaVBeYpPrAO-9Nm69gyE5TWYHJ_9t4EuwlsuTYA
       Phu65",
  "y": "AvHLNGjxokwT9T4chrlhh3oRUtMiZnh97cVrSOQEkqifsQ574IIyTc9yx1LdB
       R3zDFBhteGDMrS45Hf5sOnswRmTxGX13zqRJ7GpgUFTBPzoJ4ykSuAXFX90khZ
       8im7a",
  "d": "ROddaOzvYtwfdcg37a4GLNhFW146nDL-RKAb2MNOKeM"
}

Figure 10: BBS private key in JWK format

There is no additional holder key necessary for presentation proofs.¶

For the following protected header and array of payloads:¶

{
  "kid": "HjfcpyjuZQ-O8Ye2hQnNbT9RbbnrobptdnExR0DUjU8",
  "alg": "BBS"
}

Figure 11: Example issuer protected header

These components are signed using the private issuer key previously given, which is then representable in the following serialization:¶

eyJraWQiOiJIamZjcHlqdVpRLU84WWUyaFFuTmJUOVJiYm5yb2JwdGRuRXhSMERValU4I
iwiYWxnIjoiQkJTIn0.MTcxNDUyMTYwMA~MTcxNzE5OTk5OQ~IkRvZSI~IkpheSI~Imph
eWRvZUBleGFtcGxlLm9yZyI~eyJmb3JtYXR0ZWQiOiIxMjM0IE1haW4gU3QuXG5Bbnl0b
3duLCBDQSAxMjM0NVxuVVNBIiwic3RyZWV0X2FkZHJlc3MiOiIxMjM0IE1haW4gU3QuIi
wibG9jYWxpdHkiOiJBbnl0b3duIiwicmVnaW9uIjoiQ0EiLCJwb3N0YWxfY29kZSI6MTI
zNDUsImNvdW50cnkiOiJVU0EifQ~dHJ1ZQ.gdD9CAcF2zkH4IntAk-MD2ITKp_uWrawLP
KMiUwE2mH_PF1gFbQlpw7xBq35VJyVSBgAkHeiFoE85Fd7G9Lo9ZLemgqatC5DQLGWdWt
ZW-8

Figure 12: Issued JWP (BBS, JSON, Compact Serialization)

For a presentation with the following presentation header:¶

{
    "alg": "BBS",
    "aud": "https://recipient.example.com",
    "nonce": "wrmBRkKtXjQ"
}

Figure 13: Holder Presentation Header

The holder decides to share all information other than the email address, and generates a proof. That proof is represented in the following serialization:¶

eyJhbGciOiJCQlMiLCJhdWQiOiJodHRwczovL3JlY2lwaWVudC5leGFtcGxlLmNvbSIsI
m5vbmNlIjoid3JtQlJrS3RYalEifQ.eyJraWQiOiJIamZjcHlqdVpRLU84WWUyaFFuTmJ
UOVJiYm5yb2JwdGRuRXhSMERValU4IiwiYWxnIjoiQkJTIn0.MTcxNDUyMTYwMA~MTcxN
zE5OTk5OQ~IkRvZSI~IkpheSI~~~.sCMvF86QBn3R7vS8xNilHYMbf3gk6A0P3sptLdXX
kLIpyWRLI8lL6SD1ysF_-DJNqumzx_WgCetOzY-jaXu02g_Ec_mEOx-bJ-2auYL8SeDFy
jfooFRQGc7G0PEFLBagoygiGL_Rhhe_hMzMduo97ufMVF-0OEcV5F7bi48bczWRFFka0N
UOkZW9e614ZtPzJBA09i_r-34ffr95dU_vJBEUaGPofnZM2B4cW1sw8vtb2BkoKoWIXjq
EYHUW81yA3b5qMy55DW1FUNpOP_uHkWU9VsJQSM7XprMULjKuOaZdbLgv24ffYr7fcTQs
8ySON6GCBfHp0srUc_EIg5Ba_lNi4qg0k3M8UFAnTD_HfBBsvGczg01nKnngb4EO3g8PO
o9jRzojfrDTtq1wvuTMdinx-thiqx9PEuvcSdgOWqu2vQd0tnYEqIvpJj30_90TQ05nFk
_W6dETqaT-Wqt7tkHDzKpp1ghyl6ac-fmcde4

Figure 14: Presentation JWP (BBS, JSON, Compact serialization)

A.4. Example MAC JWP

The following example uses the MAC-H256 algorithm.¶

This is the Issuer's stable private key in the JWK format:¶

{
  "kty": "EC",
  "crv": "P-256",
  "x": "P98A5H6nXHfjyRNIG3WTZX5tShfK-eJG24HOCvj1qEM",
  "y": "ZdgxfASS-hTXEnAIvYnI0aSz2WenHQOgP3J43Gjzl_c",
  "d": "zbqFoMVyw_A7uQFvsJORLPxXCI4GiwZBvXxxsOCIR0o"
}

Figure 15: Issuer private key

This is the Issuer's ephemerally generated shared secret:¶

"pFdS_Ph8GDXTdME2ES1PAs1yvwiY7JPoFClnBZcLHdk"

Figure 16: Shared Secret

This is the Holder's presentation private key in the JWK format:¶

{
  "kty": "EC",
  "crv": "P-256",
  "x": "Mvndw9DGgODdNLiEQ-rqpTI2wZ5LKeQfbVRKSmlgv1g",
  "y": "VohB6ZcAiCo0P2F09JAqI1XdciZaglYDo0lAwuqygCQ",
  "d": "mnIjF4G3hihDqSWvwwND1RB_TJj_0FpsaXFV1EJOMVs"
}

Figure 17: Holder private key

For the following protected header and array of payloads:¶

{
  "alg": "MAC-H256",
  "typ": "JPT",
  "iss": "https://issuer.example",
  "claims": [
    "iat",
    "exp",
    "family_name",
    "given_name",
    "email",
    "address",
    "age_over_21"
  ],
  "presentation_key": {
    "kty": "EC",
    "crv": "P-256",
    "use": "sign",
    "x": "Mvndw9DGgODdNLiEQ-rqpTI2wZ5LKeQfbVRKSmlgv1g",
    "y": "VohB6ZcAiCo0P2F09JAqI1XdciZaglYDo0lAwuqygCQ"
  }
}

Figure 18: Example issuer protected header

[
    1714521600,
    1717199999,
    "Doe",
    "Jay",
    "[email protected]",
    {
        "formatted": "1234 Main St.\nAnytown, CA 12345\nUSA",
        "street_address": "1234 Main St.",
        "locality": "Anytown",
        "region": "CA",
        "postal_code": 12345,
        "country": "USA"
    },
    true
]

Figure 19: Example issuer payloads (as members of a JSON array)

The first MAC is generated using the key issuer_header and a value of the issuer protected header as a UTF-8 encoded octet string. This results in the following MAC:¶

BT-Yxz59zgCbxVuHiZdk24YU2ANLw2rmpBusoIIQHEY

Figure 20: Issuer MAC of protected header (Base64url-Encoded)

The issuer generates an array of derived keys with one for each payload by using the shared secret as the key, and the index of the payload (as payload_{n} in UTF-8 encoded octets) as the input in a HMAC operation. This results in the following set of derived keys:¶

[
  "2FyQltudQOc2o_vYTHTc_O_mEgZhOvsLEtFLIy1cB5o",
  "SmC-MI5-dHT3HJMxwm2kfeqBkmPWSHm19KPvSeJEXP8",
  "XiFumFViyN7Glz1r5NBbdR5tU2KoHb971kRAlhca8dM",
  "wURB2gqGrOJCtQEGU9EJxNYAzPnSJtLVeP924AbyWKs",
  "DmyAxJ_qJL1r_VHpuatbRoLq5IlhaaTT-dptqtNT3VA",
  "-Ct88RZPInvTzNzKW68sEKHlI-Uxi1mV4ueYp06f-Ck",
  "wNXSLdoKliDeG2vYMAzkjmYkd7N6Up-3qXzzJNlk468"
]

Figure 21: Derived payload keys (Base64url-Encoded)

A MAC is generated for each payload using the corresponding derived payload key. This results in the following set of MAC values:¶

[
  "xxoc18XStdVzVCj9X8cs4LxqZfFl2fUjsay-qXaULo4",
  "cgJ80HoKmfVXi-fdnuCjEQsKd0Dn_Xys6N9eh_Glmqc",
  "wPQZ4S8vAl4gS_qBcqIQhOgHu_jwdBCQAwZpSD0fnSQ",
  "PwlfmCadLPQHiiJQ2D-8wOiq2s_UA_MP7uJv7PCfuWs",
  "Km7eIfZn20KsuQUaTi59X9ADmuZE8xYryUCNfWywJ_0",
  "QVvB9677SzqJvyfTMSq6xqOPBeIiJcFfV91sUHD0JOM",
  "tCY7vTWqAEsJRiql3njVtn8uQ5rjKS22Fl9ThJq1YCw"
]

Figure 22: Payload MAC values (Base64url-Encoded)

The issuer protected header MAC and the payload MAC octet strings are concatenated into a single value known as the combined MAC representation. This representation is signed with the issuer's private key.¶

The proof consists of two octet string values: the signature over the combined MAC representation, and the shared secret.¶

[
  "vuHT1WWtaBpVZjjTxypjHqAILzhKAVqazEtb_qdCZLLuM7PAsQNynlTqyMfSTJrtHm
AFYvbZBEW8b4kDieNf9g",
  "vCy1i6TT73iG8wzgAvRgIU54BFOTbx7zL_seiSw71MU"
]

Figure 23: Issued Proof (Base64url-Encoded)

The final issued JWP in compact serialization is:¶

eyJhbGciOiJNQUMtSDI1NiIsInR5cCI6IkpQVCIsImlzcyI6Imh0dHBzOi8vaXNzdWVyL
mV4YW1wbGUiLCJjbGFpbXMiOlsiaWF0IiwiZXhwIiwiZmFtaWx5X25hbWUiLCJnaXZlbl
9uYW1lIiwiZW1haWwiLCJhZGRyZXNzIiwiYWdlX292ZXJfMjEiXSwicHJlc2VudGF0aW9
uX2tleSI6eyJrdHkiOiJFQyIsImNydiI6IlAtMjU2IiwidXNlIjoic2lnbiIsIngiOiJN
dm5kdzlER2dPRGROTGlFUS1ycXBUSTJ3WjVMS2VRZmJWUktTbWxndjFnIiwieSI6IlZva
EI2WmNBaUNvMFAyRjA5SkFxSTFYZGNpWmFnbFlEbzBsQXd1cXlnQ1EifX0.MTcxNDUyMT
YwMA~MTcxNzE5OTk5OQ~IkRvZSI~IkpheSI~ImpheWRvZUBleGFtcGxlLm9yZyI~eyJmb
3JtYXR0ZWQiOiIxMjM0IE1haW4gU3QuXG5Bbnl0b3duLCBDQSAxMjM0NVxuVVNBIiwic3
RyZWV0X2FkZHJlc3MiOiIxMjM0IE1haW4gU3QuIiwibG9jYWxpdHkiOiJBbnl0b3duIiw
icmVnaW9uIjoiQ0EiLCJwb3N0YWxfY29kZSI6MTIzNDUsImNvdW50cnkiOiJVU0EifQ~d
HJ1ZQ.vuHT1WWtaBpVZjjTxypjHqAILzhKAVqazEtb_qdCZLLuM7PAsQNynlTqyMfSTJr
tHmAFYvbZBEW8b4kDieNf9g~vCy1i6TT73iG8wzgAvRgIU54BFOTbx7zL_seiSw71MU

Figure 24: Issued JWP (MAC-H256, JSON, Compact Serialization)

Next, we show the presentation of the JWP with selective disclosure.¶

For presentation with the following presentation protected header:¶

{
  "alg": "MAC-H256",
  "aud": "https://recipient.example.com",
  "nonce": "H4iTRVLIsA5zKGwYTbIDfIDrj51KjCG1-XveKhdMQRA"
}

Figure 25: Presentation Protected Header

The holder will take the issuer proof (including shared secret) and derive the same individual payload MAC values (above).¶

In this case, the holder has decided not to disclose the last three claims provided by the issuer (corresponding to email, address, and age_over_21)¶

For the disclosed payloads, the holder will provide the corresponding derived key. For the non-disclosed payloads, the holder will provide the corresponding MAC value.¶

The final presented proof value is an array of octet strings. The contents are presentation header signature, followed by the issuer signature, then the value disclosed by the holder for each payload. This results in the following proof:¶

[
  "hXfGuDiaNpy472hZk2Kdoc4ZedICNqIq-8p2ZR6bZA8nLuSJ4hG7VvyKBA_YEw3EI0
Foirx6EuB8sSf9UmJ91Q",
  "vuHT1WWtaBpVZjjTxypjHqAILzhKAVqazEtb_qdCZLLuM7PAsQNynlTqyMfSTJrtHm
AFYvbZBEW8b4kDieNf9g",
  "2FyQltudQOc2o_vYTHTc_O_mEgZhOvsLEtFLIy1cB5o",
  "SmC-MI5-dHT3HJMxwm2kfeqBkmPWSHm19KPvSeJEXP8",
  "XiFumFViyN7Glz1r5NBbdR5tU2KoHb971kRAlhca8dM",
  "wURB2gqGrOJCtQEGU9EJxNYAzPnSJtLVeP924AbyWKs",
  "Km7eIfZn20KsuQUaTi59X9ADmuZE8xYryUCNfWywJ_0",
  "QVvB9677SzqJvyfTMSq6xqOPBeIiJcFfV91sUHD0JOM",
  "tCY7vTWqAEsJRiql3njVtn8uQ5rjKS22Fl9ThJq1YCw"
]

Figure 26: Presentation proof (Base64url-Encoded)

The final presented JWP in compact serialization is:¶

eyJhbGciOiJNQUMtSDI1NiIsImF1ZCI6Imh0dHBzOi8vcmVjaXBpZW50LmV4YW1wbGUuY
29tIiwibm9uY2UiOiJINGlUUlZMSXNBNXpLR3dZVGJJRGZJRHJqNTFLakNHMS1YdmVLaG
RNUVJBIn0.eyJhbGciOiJNQUMtSDI1NiIsInR5cCI6IkpQVCIsImlzcyI6Imh0dHBzOi8
vaXNzdWVyLmV4YW1wbGUiLCJjbGFpbXMiOlsiaWF0IiwiZXhwIiwiZmFtaWx5X25hbWUi
LCJnaXZlbl9uYW1lIiwiZW1haWwiLCJhZGRyZXNzIiwiYWdlX292ZXJfMjEiXSwicHJlc
2VudGF0aW9uX2tleSI6eyJrdHkiOiJFQyIsImNydiI6IlAtMjU2IiwidXNlIjoic2lnbi
IsIngiOiJNdm5kdzlER2dPRGROTGlFUS1ycXBUSTJ3WjVMS2VRZmJWUktTbWxndjFnIiw
ieSI6IlZvaEI2WmNBaUNvMFAyRjA5SkFxSTFYZGNpWmFnbFlEbzBsQXd1cXlnQ1EifX0.
MTcxNDUyMTYwMA~MTcxNzE5OTk5OQ~IkRvZSI~IkpheSI~~~.hXfGuDiaNpy472hZk2Kd
oc4ZedICNqIq-8p2ZR6bZA8nLuSJ4hG7VvyKBA_YEw3EI0Foirx6EuB8sSf9UmJ91Q~vu
HT1WWtaBpVZjjTxypjHqAILzhKAVqazEtb_qdCZLLuM7PAsQNynlTqyMfSTJrtHmAFYvb
ZBEW8b4kDieNf9g~2FyQltudQOc2o_vYTHTc_O_mEgZhOvsLEtFLIy1cB5o~SmC-MI5-d
HT3HJMxwm2kfeqBkmPWSHm19KPvSeJEXP8~XiFumFViyN7Glz1r5NBbdR5tU2KoHb971k
RAlhca8dM~wURB2gqGrOJCtQEGU9EJxNYAzPnSJtLVeP924AbyWKs~Km7eIfZn20KsuQU
aTi59X9ADmuZE8xYryUCNfWywJ_0~QVvB9677SzqJvyfTMSq6xqOPBeIiJcFfV91sUHD0
JOM~tCY7vTWqAEsJRiql3njVtn8uQ5rjKS22Fl9ThJq1YCw

Figure 27: Presented JWP (MAC-H256, JSON, Compact Serialization)