JSON Proof Algorithms

Internet-Draft	json-proof-algorithms	March 2026
Jones, et al.	Expires 3 September 2026	[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.¶

7. Algorithm Specifications

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

7.1. 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).¶

7.1.1. JWS Algorithm

The Single Use algorithm uses multiple signing keys to protect the Header as well as individual payloads of an Issued JWP. The issuer uses a stable public key to sign each Header, and a per-JWP ephemeral key (conveyed within the Header) to protect the individual payloads. These signatures are all created using the same Asymmetric Algorithm, with the JOSE and COSE name/label of this algorithm being part of registration for a fully-specified Single Use algorithm identifier.¶

The Issuer Header also conveys a holder presentation key, an ephemeral asymmetric key meant to only be used for presenting a single JWP. The fully-specified algorithm the holder must use for presentations is also included. This algorithm MAY be different from the algorithm used by the issuer.¶

The chosen algorithms MUST be asymmetric signing algorithms, so that each signature can be verified without sharing any private values between the parties.¶

7.1.2. Holder Setup

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

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.¶

The issuer MUST determine an appropriate holder presentation algorithm corresponding to the holder presentation key. If the holder and verifier cannot be assumed to know this algorithm is the appropriate choice for a given holder presentation key, this value MUST be conveyed in the hpa Issuer Header.¶

7.1.3. 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.¶

7.1.4. Signing Payloads

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

7.1.5. Issuer Header

The Issuer's Ephemeral Key MUST be included via the Issuer Ephemeral Key Header Parameter.¶

The Holder's Presentation Key MUST be included via the Holder Presentation Key Header Parameter.¶

The Holder's Presentation Algorithm MUST be included via the Holder Presentation Algorithm Header Parameter unless there is another way for the holder and verifier to unambiguously determine the appropriate algorithm to use.¶

The Issuer Header is signed using the appropriate internal signing algorithm for the given fully-specified single use algorithm, using the issuer's Stable Key.¶

7.1.6. Payloads

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

7.1.7. Proof

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

7.1.8. Presentation Header #{presentation-header}

To generate a new presentation, the holder first creates a Presentation 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 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 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.¶

The Presentation Header MUST contain the same Algorithm protected header as the Issuer Header. The Holder Presentation Algorithm Header Parameter MUST NOT be included.¶

7.1.9. Presentation

The holder derives a new proof as part of presentation. The holder will also use these components to generate a presentation internal representation. The number of components depends on the number of payloads which are being disclosed in the presented JWP.¶

The first proof component will be the signature over the Issuer Header made by the issuer's Stable Key.¶

For each payload which is to be disclosed, the corresponding payload signature (from the issued JWP) is included as a subsequent proof component. If the payload is being omitted, the corresponding payload signature is omitted from the proof components.¶

The Presentation Header, Issuer Header, payload slots (distinguishing which are being disclosed) and these proof components are inputs to determine the presentation internal representation.¶

The holder's signature over the presentation internal representation (using the holder's private key and the holder presentation algorithm) is then included as one additional proof component in the final presentation.¶

For example, if only the second and fifth of five payloads are being disclosed, then the proof at this stage will consist of three values:¶

The issuer's signature over the Issuer Header¶
The payload signature corresponding to the second payload¶
The payload signature corresponding to the fifth payload.¶

The presentation internal representation would be calculated with these three proof components, while the final presentation would have an additional fourth component containing the signature using the holder's private key.¶

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.¶

7.1.10. Verification of Presentation

Verification is performed using the following steps.¶

Check that the number of proof components is appropriate for the number of disclosed payloads. There MUST be two more proof components than disclosed payloads.¶
Verify the first proof component is a valid signature over Issuer Header octets, using the issuer's stable key.¶
Extract the holder presentation key and holder presentation algorithm (if present) from the Issuer Header.¶
Omitting the final payload component, calculate the presentation internal representation.¶
Verify the final proof component is a valid signature over the presentation internal binary form, using the holder's presentation key and the extracted (or otherwise determined) holder presentation algorithm.¶
For each remaining proof component, verify they form a valid signature over each disclosed payload in sequence, using the issuer's ephemeral key.¶

7.1.11. 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".¶

7.2. Presentation Internal Representation

Some algorithms (such as Single use and MAC) use a holder key to provide integrity over the presentation. For these algorithms, an internal binary form of the presentation must be generated both for signing by the holder, and for verification by the verifier. Other algorithms MAY use this same form for consistency.¶

The instructions for creating this binary representation will also create well-formed CBOR, although this data is not meant to be shared outside the implementing algorithm. Instead, it focuses on simplicity of generation by the holder and verifier implementations. Although CBOR has multiple representations of the same underlying information, this same octet string MUST be generated by an implementation.¶

When a length or count is added by the steps below, it is added as its 8-byte, network-ordered representation. For example, the length of a 1,234 byte payload would have a length representation of 0x00 00 00 00 00 00 04 D2.¶

The binary representation is created by appending data into a single octet string in the following order:¶

0x84 5B¶
The length and octets of the Presentation Header¶
0x5B¶
The length and octets of the Issuer Header¶
0x9B¶
The number of payload slots in the issued message¶
For each payload representation:¶
- If the payload is being omitted, the value 0xF6¶
- Otherwise:¶
  1. 0x5B¶
  2. The length and octets of the payload¶
0x9B¶
The number of proof components as specified by the algorithm¶
For each proof component, append:¶
1. 0x5B¶
2. The length and octets of the proof component¶

7.3. 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.¶

7.3.1. JPA Algorithms

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

7.3.2. 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.¶

7.3.3. 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 Header octets as header, and the array of payload octet string as messages.¶

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

7.3.4. Issuance Proof Verification

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

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

7.3.5. 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 Header as header, the issuance proof as signature, the issuance payloads as messages, and the holder's Presentation 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 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.¶

7.3.6. Presentation Verification

Verification of a presentation is done by the verifier using the ProofVerify operation from [@!I-D.irtf-cfrg-bbs-signatures, Section 3.5.4].¶

This operation utilizes the issuer's public key as PK, the Issuer Header as header, the issuance proof as signature, the holder's Presentation 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.¶

7.4. Message Authentication Code

The Message Authentication Code (MAC) JPA uses a MAC to both generate ephemeral secrets and to authenticate payloads, along with an asymmetric signature to provide integrity to the issued JWP.¶

The holder can manipulate which payloads are disclosed from the issued JWP, and uses the Holder Presentation Key to create a presentation. The signature created from the Holder Presentation Key MAY use a different algorithm than the Issuer used to sign the issued form.¶

Like 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.¶

7.4.1. Holder Setup

In order to support the protection of a presentation by a holder to a verifier, the holder MUST use a Holder Presentation Key during the issuance and the presentation of every MAC JWP. This Holder Presentation Key MUST be generated and used for only one JWP if unlinkability is desired.¶

The holder's presentation key MUST be included in the Issuer Header using the Holder Presentation Key Header Parameter.¶

7.4.2. 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 with 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.¶

7.4.3. Combined MAC Representation

The combined MAC representation is a single octet string representing the MAC values of the Issuer 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 Header and the integrity of any disclosed payloads.¶

The steps below describe a sequential concatenation of binary values to generate the Combined MAC Representation. The instructions for generating this octet string will also generate well-formed CBOR, although this data is not meant to be shared outside the implementing algorithm. Instead, it focuses on simplicity of generation by the issuer, holder, and verifier implementations. Although CBOR has multiple representations of the same underlying information, this same octet string MUST be generated by an implementation.¶

When a length or count is added by steps in this section, it is added as its 8-byte, network-ordered representation. For example, the length of a 1,234-byte payload would have a length representation of 0x00 00 00 00 00 00 04 D2.¶

The holder will a unique key per payload value using a MAC, with the Shared Secret as the key and a generated binary value. This binary value is constructed by appending data into a single octet string:¶

0x82 67 70 61 79 6C 6F 61 64 1B¶
The zero indexed count of the payload slot¶

The holder will also compute a corresponding MAC of each payload. This MAC uses the unique key above and the payload octet string as the value.¶

When verifying a presentation, the shared secret will be unavailable so the unique key cannot be calculated. The payload octet string may also be omitted in the presentation. The following instructions describe how to get the corresponding MAC of each payload:¶

If the payload is disclosed, the corresponding proof component (as described in MAC Presentation Proof) will contain the generated unique key. The payload MAC will be calculated using this key and the payload octets as the value.¶
If the payload is not disclosed, the corresponding proof component will be the payload MAC.¶

The binary representation is created by appending data into a single octet string in the following order:¶

0x82 5B¶
The length and octets of the Issuer Header¶
0x9B¶
The number of payload slots in the issued JWP¶
For each payload representation:¶
1. 0x5B¶
2. The length and value of the per payload MAC¶

7.4.4. Issuer Header

The Holder's Presentation Key MUST be included via the Holder Presentation Key Header Parameter.¶

7.4.5. 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 combined MAC representation using its stable public key, and the internal signing algorithm for the given fully-specified MAC algorithm variant.¶

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

7.4.6. Presentation Header

See the Presentation Header section given for Single Use algorithms.¶

7.4.7. Presentation Proof

The presentation proof is made of multiple components.¶

The first proof component is the issuer signature over the Combined MAC Representation, which is provided as the first proof component from the issued form.¶

There will now be one proof component per payload slot in the issued JWP. These are used by the verifier to reconstruct the combined MAC representation without access to the Shared Secret. The proof components are calculated per the instructions used to generate the Combined MAC Representation ¶

If a payload is disclosed, the corresponding proof component will be the unique key.¶

If a payload is not disclosed, the corresponding proof component will be the payload's MAC (using the unique key.)¶

The Presentation Header, Issuer Header, payload slots (distinguishing which are being disclosed) and above proof components are inputs to determine the presentation internal representation.¶

The presented form should have two more proof components than payload slots in the issued JWP.¶

Note that the second component of the issued JWP is a shared secret for use by the holder to generate the unique keys used in the Combined MAC Representation. This MUST NOT be included in the presentation.¶

7.4.8. Verification of the Presentation Proof

Verification is performed using the following steps.¶

Check the number of proof components is appropriate for the number of disclosed payloads. There MUST be two more proof components than disclosed payloads.¶
Using the fully-specified MAC algorithm in use, use the Issuer Header, disclosed payloads, and the proof components corresponding to the payloads to regenerate the Combined MAC Representation.¶
Verify the first proof component is a valid signature over the Issuer Header octets, using the issuer's stable key.¶
Extract the holder presentation key and holder presentation algorithm (if present) from the Issuer Header.¶
Omitting the final payload component, calculate the presentation internal representation.¶
Verify the final proof component is a valid signature over the presentation internal binary form, using the holder's presentation key and the extracted (or otherwise determined) holder presentation algorithm.¶

7.4.9. 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¶

9. 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 jose-reg-review@ietf.org 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 iesg@ietf.org 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.¶

9.1. JSON Web Proof Algorithms Registry

This specification establishes the IANA "JSON Web Proof Algorithms" registry, under the "JSON Object Signing and Encryption (JOSE)" registry group. The registry records values values of the JWP alg (algorithm) Header Parameter. 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.¶

9.1.1. 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 of 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 IETF Stream 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.¶

9.1.2. Initial Registry Contents

9.1.2.1. 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 7.1.11 of this specification¶
Algorithm Analysis Documents(s): n/a¶

9.1.2.2. 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 7.1.11 of this specification¶
Algorithm Analysis Documents(s): n/a¶

9.1.2.3. 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 7.1.11 of this specification¶
Algorithm Analysis Documents(s): n/a¶

9.1.2.4. BBS using SHA-256 Algorithm

Algorithm Name: BBS using SHA-256¶
Algorithm JSON Label: BBS¶
Algorithm CBOR Label: 4¶
Algorithm Description: Corresponds to a cipher suite 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 7.3.1 of this specification¶
Algorithm Analysis Documents(s): n/a¶

9.1.2.5. 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 7.4.9 of this specification¶
Algorithm Analysis Documents(s): n/a¶

9.1.2.6. 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 7.4.9 of this specification¶
Algorithm Analysis Documents(s): n/a¶

9.1.2.7. 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 7.4.9 of this specification¶
Algorithm Analysis Documents(s): n/a¶

9.1.2.8. 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 7.4.9 of this specification¶
Algorithm Analysis Documents(s): n/a¶

9.1.2.9. 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 7.4.9 of this specification¶
Algorithm Analysis Documents(s): n/a¶

9.1.2.10. 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 7.4.9 of this specification¶
Algorithm Analysis Documents(s): n/a¶

9.2. JSON Web Key Parameters Registry

This section registers the following JWK parameter in the IANA "JSON Web Key Parameters" registry [IANA.JOSE] established by [RFC7517].¶

9.2.1. Registry Contents

Parameter Name: proof_alg¶
Parameter Description: JSON Web Proof algorithm associated with the key¶
Used with "kty" Value(s): *¶
Parameter Information Class: Public¶
Change Controller: IESG¶
Specification Document(s): Section 6.1 of this specification¶

9.3. COSE Key Common Parameters Registry

This section registers the following COSE_Key parameter in the IANA "COSE Key Common Parameters" registry [IANA.COSE] established by [RFC9052].¶

9.3.1. Registry Contents

Name: proof_alg¶
Label: TBD (requested assignment 7)¶
CBOR Type: int / tstr¶
Value Registry: JSON Web Proof Algorithms¶
Description: JSON Web Proof algorithm associated with the key¶
Reference: Section 6.1 of this specification¶

[RFC-EDITOR: The temporary development label for this COSE_Key parameter is 7CPA, following [I-D.bormann-cbor-draft-numbers]. Please replace 7CPA with the final assigned value and remove this note before publication.]¶

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:¶

{
  "crv": "P-256",
  "d": "DK-sovUBcervl5QDJKW6Ujwq51ICSfkSSRdcd6fSpOE",
  "kty": "EC",
  "x": "xs_KueKqEaJbGljUbyYH76P5Z94HOkafqrD1BGKnijU",
  "y": "BHbl5x2yWAOufTsB5EHetmBGl_c1TjzbtoTL3TZgvPk"
}

Figure 1: Issuer Private Key (ES256 in JWK)

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

{
  "crv": "P-256",
  "d": "kK_tJMtwmY15FvJfAJBceewzYibZhh1Uz9jQWUHEDfc",
  "kty": "EC",
  "x": "9zZSaMP_X_NFOm1Dinx_Ek0JQCi1Q62wyJYW_4Ge8J0",
  "y": "niWuxuD82iGuZ9fHHtvaruTuwebTqlPoiltsLNcv5LM"
}

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:¶

{
  "crv": "P-256",
  "d": "sYGORNvEEUbzbOUsPVAxYPK0Nh-Pt86ToMGp-GNA4Rg",
  "kty": "EC",
  "x": "xP_7tI1acMDwEVxUp-XtCVxNTkzfPKUXYH-1w8YsfnU",
  "y": "PkCV1HmrruCRjM44DAbdb_1opv03xAEMZeKbih_CEJQ"
}

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

The 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",
  "claims": [
    "iat",
    "exp",
    "family_name",
    "given_name",
    "email",
    "address",
    "age_over_21"
  ],
  "hpa": "ES256",
  "hpk": {
    "crv": "P-256",
    "kty": "EC",
    "x": "xP_7tI1acMDwEVxUp-XtCVxNTkzfPKUXYH-1w8YsfnU",
    "y": "PkCV1HmrruCRjM44DAbdb_1opv03xAEMZeKbih_CEJQ"
  },
  "iek": {
    "crv": "P-256",
    "kty": "EC",
    "x": "9zZSaMP_X_NFOm1Dinx_Ek0JQCi1Q62wyJYW_4Ge8J0",
    "y": "niWuxuD82iGuZ9fHHtvaruTuwebTqlPoiltsLNcv5LM"
  },
  "iss": "https://issuer.example",
  "typ": "JPT"
}

Figure 4: Issuer Header (SU-ES256, JSON)
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Figure 5: Encoded Issuer 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 Header with the associated alg value. In this example, the fixed Header used for each JWS is the serialized JSON Object {"alg":"ES256"}. This 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",
  "jaydoe@example.org",
  {
    "country": "USA",
    "formatted": "1234 Main St.\nAnytown, CA 12345\nUSA",
    "locality": "Anytown",
    "postal_code": 12345,
    "region": "CA",
    "street_address": "1234 Main St."
  },
  true
]

Figure 6: Issuer payloads (JSON, as array)

The compact serialization of the same JPT is:¶
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.MTcxNDUyMTYwMA~MTcxNzE5OTk5OQ~IkRvZSI~IkpheSI~ImpheWRvZU
BleGFtcGxlLm9yZyI~eyJjb3VudHJ5IjoiVVNBIiwiZm9ybWF0dGVkIjoiMTIzNCBNYWl
uIFN0LlxuQW55dG93biwgQ0EgMTIzNDVcblVTQSIsImxvY2FsaXR5IjoiQW55dG93biIs
InBvc3RhbF9jb2RlIjoxMjM0NSwicmVnaW9uIjoiQ0EiLCJzdHJlZXRfYWRkcmVzcyI6I
jEyMzQgTWFpbiBTdC4ifQ~dHJ1ZQ.2hSttoVIGlLP727_737J5Srtkr8w5P4zG1QihW2J
uvob4EkqDiJ319D5TdQczv3bAqBeWtxuDOHWOhiIrYaGTw~KuiMmRW7h-2OqDCZ6R8Zn3
XQ_8youcBFxEmmXWMJyiceg6mZtEPcDTTN3l6HOE-5jzZ-G2cDl5gMjilbhGDxeQ~RSTl
0mFdKoQYMAcAzt7_3XV6lCkxVRR0rJQtgGFFujxZXFAAyGRR02Cuu7T6Fn0c8IGmySw7T
NIzcxeyEyYTlQ~1l9iFb7xjMiRjUCrnyH12Gf99LSjEOKW_Spguex4mkNdwdpET7qRZq1
siO2tWKB_Z6nIX2cTOZRhmzzjGF_m4Q~TXc80HAXqHvTUOyg990ihSMCCV8aLRyn_gyaX
6mnkHRIbjDaV-CAMLx3RhmdC3YkthnyEnaXFF5HZtmkIxGLEA~eA9uT8m3CTYttNl0_dd
XKhhh1RnVnIOE4rbMfLq7jw8PAUBXZ7o1y26gV5g7Kpghmt2Fd0N9oK2imQvtFn9bUA~b
YGxg3HjwR7O406Ne2U1O207QdOm6kF2g-N9NQtkaTFwGaEz_1U5uonRPylkR1xlmvKvt2
rMTqiYf-_-pSYdmg~nMkClCSY1g-U5YMW473p2UKm7TFYs3bpjWUrAFCcaC0U958yRXmH
S0nY0iFIfqVkTUxqhrvq55VV4r8xKsp6fQ

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": "Kbyx9Mlh-XUgbOdam1vR-dl4WK13Ltn6y7nfvFUQKKM"
}

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

eyJhbGciOiJTVS1FUzI1NiIsImF1ZCI6Imh0dHBzOi8vcmVjaXBpZW50LmV4YW1wbGUuY
29tIiwibm9uY2UiOiJLYnl4OU1saC1YVWdiT2RhbTF2Ui1kbDRXSzEzTHRuNnk3bmZ2Rl
VRS0tNIn0

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

We apply selective disclosure of only the given name and age claims (family name and email hidden), and remove the proof components corresponding to these entries.¶

Using the selectively disclosed information, we generate the presentation internal representation. Using that and the selectively disclosed payloads, we get the following presented JPT in compact serialization:¶

eyJhbGciOiJTVS1FUzI1NiIsImF1ZCI6Imh0dHBzOi8vcmVjaXBpZW50LmV4YW1wbGUuY
29tIiwibm9uY2UiOiJLYnl4OU1saC1YVWdiT2RhbTF2Ui1kbDRXSzEzTHRuNnk3bmZ2Rl
VRS0tNIn0.eyJhbGciOiJTVS1FUzI1NiIsImNsYWltcyI6WyJpYXQiLCJleHAiLCJmYW1
pbHlfbmFtZSIsImdpdmVuX25hbWUiLCJlbWFpbCIsImFkZHJlc3MiLCJhZ2Vfb3Zlcl8y
MSJdLCJocGEiOiJFUzI1NiIsImhwayI6eyJjcnYiOiJQLTI1NiIsImt0eSI6IkVDIiwie
CI6InhQXzd0STFhY01Ed0VWeFVwLVh0Q1Z4TlRremZQS1VYWUgtMXc4WXNmblUiLCJ5Ij
oiUGtDVjFIbXJydUNSak00NERBYmRiXzFvcHYwM3hBRU1aZUtiaWhfQ0VKUSJ9LCJpZWs
iOnsiY3J2IjoiUC0yNTYiLCJrdHkiOiJFQyIsIngiOiI5elpTYU1QX1hfTkZPbTFEaW54
X0VrMEpRQ2kxUTYyd3lKWVdfNEdlOEowIiwieSI6Im5pV3V4dUQ4MmlHdVo5ZkhIdHZhc
nVUdXdlYlRxbFBvaWx0c0xOY3Y1TE0ifSwiaXNzIjoiaHR0cHM6Ly9pc3N1ZXIuZXhhbX
BsZSIsInR5cCI6IkpQVCJ9.MTcxNDUyMTYwMA~MTcxNzE5OTk5OQ~IkRvZSI~IkpheSI~
ImpheWRvZUBleGFtcGxlLm9yZyI~eyJjb3VudHJ5IjoiVVNBIiwiZm9ybWF0dGVkIjoiM
TIzNCBNYWluIFN0LlxuQW55dG93biwgQ0EgMTIzNDVcblVTQSIsImxvY2FsaXR5IjoiQW
55dG93biIsInBvc3RhbF9jb2RlIjoxMjM0NSwicmVnaW9uIjoiQ0EiLCJzdHJlZXRfYWR
kcmVzcyI6IjEyMzQgTWFpbiBTdC4ifQ~dHJ1ZQ~~.2hSttoVIGlLP727_737J5Srtkr8w
5P4zG1QihW2Juvob4EkqDiJ319D5TdQczv3bAqBeWtxuDOHWOhiIrYaGTw~KuiMmRW7h-
2OqDCZ6R8Zn3XQ_8youcBFxEmmXWMJyiceg6mZtEPcDTTN3l6HOE-5jzZ-G2cDl5gMjil
bhGDxeQ~RSTl0mFdKoQYMAcAzt7_3XV6lCkxVRR0rJQtgGFFujxZXFAAyGRR02Cuu7T6F
n0c8IGmySw7TNIzcxeyEyYTlQ~1l9iFb7xjMiRjUCrnyH12Gf99LSjEOKW_Spguex4mkN
dwdpET7qRZq1siO2tWKB_Z6nIX2cTOZRhmzzjGF_m4Q~TXc80HAXqHvTUOyg990ihSMCC
V8aLRyn_gyaX6mnkHRIbjDaV-CAMLx3RhmdC3YkthnyEnaXFF5HZtmkIxGLEA~eA9uT8m
3CTYttNl0_ddXKhhh1RnVnIOE4rbMfLq7jw8PAUBXZ7o1y26gV5g7Kpghmt2Fd0N9oK2i
mQvtFn9bUA~Iuh1OiiA7HfaQ-C8rEoHTiOHW5NfGOPVYT2hn1P70X1gMCGKTwt2faDggF
J3FhYEJ3hTiPhH0B_z0lMMn-Gmlw

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.ietf-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.¶

{          / issuer 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: {      / iek /
    1: 2,   / kty : "EC2" /
    -1: 1,  / crv: "P-256" /
    -2: h'f7365268c3ff5ff3453a6d438a7c7f124d094028b543adb0c89616ff' +
        h'819ef09d', / x /
    -3: h'9e25aec6e0fcda21ae67d7c71edbdaaee4eec1e6d3aa53e88a5b6c2c' +
        h'd72fe4b3'  / y /
  },
  9: {      / hpk /
    1: 2,   / kty: "EC2" /
    -1: 1,  / crv: "P-256" /
    -2: h'c4fffbb48d5a70c0f0115c54a7e5ed095c4d4e4cdf3ca517607fb5c3' +
        h'c62c7e75', / x /
    -3: h'3e4095d479abaee0918cce380c06dd6ffd68a6fd37c4010c65e29b8a' +
        h'1fc21094'  / y /
  },
  10: -9    / hpa: "ESP256" (I-D.ietf-jose-fully-specified-algorithms TBD-9) /
}

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

[ / payloads    /
  / iat         / 171452160,
  / exp         / 171719999,
  / family_name / "Doe",
  / given_name  / "Jay",
  / email       / "jaydoe@example.org",
  / 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):¶
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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:¶

{          / holder header /
  1: 1,    / alg: "SU-ES256" /
  6: "https://recipient.example.com", / aud /
  7: h'29bcb1f4c961f975206ce75a9b5bd1f9d97858ad772ed9facbb9dfbc551028a3', / nonce /
}

Figure: Presentation 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:¶

{
  "crv": "BLS12381G2",
  "d": "NvpnjNccjwvZTsmcBO4Ntw46mzig50sfOYjeljAl8Bk",
  "kty": "OKP",
  "proof_alg": "BBS",
  "use": "proof",
  "x": "l5CqEP9LwItyq0KzEU7FVrNollmcqgUGX6v69ghb3VNRMfPP3wGg7Tk8m9VEn
        edsFUKjxj35OiCTWU3w43faSmn3wenj3E52S4ifIRJgBI1JP_q_1-7TsA7Wmt
        wj1Z05"
}

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:¶

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

Figure 11: Example Issuer Header

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

eyJhbGciOiJCQlMiLCJraWQiOiJIamZjcHlqdVpRLU84WWUyaFFuTmJUOVJiYm5yb2Jwd
GRuRXhSMERValU4In0.MTcxNDUyMTYwMA~MTcxNzE5OTk5OQ~IkRvZSI~IkpheSI~Imph
eWRvZUBleGFtcGxlLm9yZyI~eyJjb3VudHJ5IjoiVVNBIiwiZm9ybWF0dGVkIjoiMTIzN
CBNYWluIFN0LlxuQW55dG93biwgQ0EgMTIzNDVcblVTQSIsImxvY2FsaXR5IjoiQW55dG
93biIsInBvc3RhbF9jb2RlIjoxMjM0NSwicmVnaW9uIjoiQ0EiLCJzdHJlZXRfYWRkcmV
zcyI6IjEyMzQgTWFpbiBTdC4ifQ~dHJ1ZQ.t-CcghOPDTsp5rqRS3Uxc71LnFXzeFuLln
5xL1QjofTHVe7l_0CNFuKmfxDC51uCKIjBhPEy3gmKSC3sj6I2tcDz9HmgH0iD2qSOiRt
IALk

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: 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.eyJhbGciOiJCQlMiLCJraWQiOiJIamZjcHlqdVp
RLU84WWUyaFFuTmJUOVJiYm5yb2JwdGRuRXhSMERValU4In0.MTcxNDUyMTYwMA~MTcxN
zE5OTk5OQ~IkRvZSI~IkpheSI~~~.j8Un-MjA3J3D5HN9_dC3WLgFx51MIWLc--NPxO1N
SIb7RZENkiwMo8pzHcq3uevulTEy0Ni_BqBQ6wrS19uBtfBAlsqf3boYAwroR4RIMFc7D
Ko3qhKgy_Y7A1Zt_2CIrfjEPj_PsaKCntHZRjGZs9ZA1tzvc3CyrGYlE4ssiEHU9AY_t1
eGCEro_nI8VAVhCVOyl-_GkhjstRLxACFlM8lAJ1MRrNPfIYKsMjFV5PlBkY9sab1dE5S
n7ZpQyQEl2g9jlLfYm2plGUPT4KV6mV0sWlmAT73XWQwsnc6WR_dhoL-QNLSBRgKXklDu
yN40M02Qy0SndGHx-W-rlvCD7LkoHbuKpX2GtyE6aR4EBxMsMtRZXLsfD0JzG37TfRw2F
II_BFslao_0XsWNbpUATyX5DvYB0Uvzd94a_B0eCuf-qfoLTlZIeqWZIO9kVVk3Iu1HSh
pL1vx21g7iVQM7Wo1jgkwjpcml7Nn4WGFee_s

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:¶

{
  "crv": "P-256",
  "d": "DK-sovUBcervl5QDJKW6Ujwq51ICSfkSSRdcd6fSpOE",
  "kty": "EC",
  "x": "xs_KueKqEaJbGljUbyYH76P5Z94HOkafqrD1BGKnijU",
  "y": "BHbl5x2yWAOufTsB5EHetmBGl_c1TjzbtoTL3TZgvPk"
}

Figure 15: Issuer private key

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

"btenJSeYxfYFWF_1WYcQSj5VCY-ecbfibB9Y1V9gHZo"

Figure 16: Shared Secret

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

{
  "crv": "P-256",
  "d": "sYGORNvEEUbzbOUsPVAxYPK0Nh-Pt86ToMGp-GNA4Rg",
  "kty": "EC",
  "x": "xP_7tI1acMDwEVxUp-XtCVxNTkzfPKUXYH-1w8YsfnU",
  "y": "PkCV1HmrruCRjM44DAbdb_1opv03xAEMZeKbih_CEJQ"
}

Figure 17: Holder private key

For the following Header and array of payloads:¶

{
  "alg": "MAC-H256",
  "claims": [
    "iat",
    "exp",
    "family_name",
    "given_name",
    "email",
    "address",
    "age_over_21"
  ],
  "hpa": "ES256",
  "hpk": {
    "crv": "P-256",
    "kty": "EC",
    "use": "sign",
    "x": "xP_7tI1acMDwEVxUp-XtCVxNTkzfPKUXYH-1w8YsfnU",
    "y": "PkCV1HmrruCRjM44DAbdb_1opv03xAEMZeKbih_CEJQ"
  },
  "iss": "https://issuer.example",
  "typ": "JPT"
}

Figure 18: Example Issuer Header

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

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

The issuer generates an array of derived keys, one per payload slot. This is done using the shared secret as the key and a binary value based on the payload slot index (from zero) as input to the HMAC operation.¶

This results in the following set of derived keys:¶

[
  "dAl1DDShaQd8JNWxtb_geTjPpdlUvhAYxhjZXQT9m78",
  "ixhgL6Xok1TY8qhJQs5RpUUdwaI2UUth-c1kE_Tp9Is",
  "AlsVYc-OkHzb-jjK11lXIebmaMydqDqInqVe29W2Vpo",
  "sMtqZYvHga5XmI0iXfjt590DUGTkijkW2uBlcxUtNic",
  "rdM7EBeXSoiWAH2LEwF29M9OfuuL6CBPy0BHe7kfhiU",
  "BxMPFRpKIr2mxKh5CJh1T4uUTaR6FOUNFtViGUp2Rpg",
  "5dhLeVVCb6qFOJWf3juea0t1BxQxVtfjZ60bB-Wx3-g"
]

Figure 20: 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:¶

[
  "pbFrro8SUA49BeLEhzFHsO0YXW1H9i2Q3Fx5zwvaGp8",
  "507GVZGewdO3yNLRx3SmSDpBrOu_TIcZsNBStpxcbZ0",
  "klrnMHpYlOCPR0mHqaABeajd7vLP7FPy7G-IqKCwY4s",
  "jvC3hx68X9-wWetwIZAcUcpdpfO2dg0pZhUQwgTqBvo",
  "LCwZOoqRRM0OePErrPelGxf0TEngY8ZjoDDi2OJLHZo",
  "BJ5DQg-cWglSDDxdmXs1AD0Zkb09a32h3vCEqFdj0PI",
  "d4PaY2wWPAy8xYbK4yYrnZIZAbPKIb0OYScKVd7Er5I"
]

Figure 21: Payload MAC values (Base64url-Encoded)

The Issuer Header and payload MAC values are combined into a binary representation known as the Compact 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.¶

[
  "2sqPqwf_Yw9goaPXaJewV7K6C5OkXH3sC8aNRZ2JwPt6ygX5I9S8_Xu7Hf2vTqY2H2
td0bOiJZ2l2KgbKkMHtw",
  "OQ8bMadJi9YxsHjJ0eGv6Qu8kXQNfBqueu71k1jq22c"
]

Figure 22: Issued Proof (Base64url-Encoded)

The final issued JWP in compact serialization is:¶

eyJhbGciOiJNQUMtSDI1NiIsImNsYWltcyI6WyJpYXQiLCJleHAiLCJmYW1pbHlfbmFtZ
SIsImdpdmVuX25hbWUiLCJlbWFpbCIsImFkZHJlc3MiLCJhZ2Vfb3Zlcl8yMSJdLCJocG
EiOiJFUzI1NiIsImhwayI6eyJjcnYiOiJQLTI1NiIsImt0eSI6IkVDIiwidXNlIjoic2l
nbiIsIngiOiJ4UF83dEkxYWNNRHdFVnhVcC1YdENWeE5Ua3pmUEtVWFlILTF3OFlzZm5V
IiwieSI6IlBrQ1YxSG1ycnVDUmpNNDREQWJkYl8xb3B2MDN4QUVNWmVLYmloX0NFSlEif
SwiaXNzIjoiaHR0cHM6Ly9pc3N1ZXIuZXhhbXBsZSIsInR5cCI6IkpQVCJ9.MTcxNDUyM
TYwMA~MTcxNzE5OTk5OQ~IkRvZSI~IkpheSI~ImpheWRvZUBleGFtcGxlLm9yZyI~eyJj
b3VudHJ5IjoiVVNBIiwiZm9ybWF0dGVkIjoiMTIzNCBNYWluIFN0LlxuQW55dG93biwgQ
0EgMTIzNDVcblVTQSIsImxvY2FsaXR5IjoiQW55dG93biIsInBvc3RhbF9jb2RlIjoxMj
M0NSwicmVnaW9uIjoiQ0EiLCJzdHJlZXRfYWRkcmVzcyI6IjEyMzQgTWFpbiBTdC4ifQ~
dHJ1ZQ.2sqPqwf_Yw9goaPXaJewV7K6C5OkXH3sC8aNRZ2JwPt6ygX5I9S8_Xu7Hf2vTq
Y2H2td0bOiJZ2l2KgbKkMHtw~OQ8bMadJi9YxsHjJ0eGv6Qu8kXQNfBqueu71k1jq22c

Figure 23: Issued JWP (MAC-H256, JSON, Compact Serialization)

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

For presentation with the following Presentation Header:¶

{
  "alg": "MAC-H256",
  "aud": "https://recipient.example.com",
  "nonce": "Kbyx9Mlh-XUgbOdam1vR-dl4WK13Ltn6y7nfvFUQKKM"
}

Figure 24: Presentation 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 each payload slot, the holder will provide one of two values as part of the proof value. For a disclosed payload, the holder will provide the corresponding derived key. For a non-disclosed payload, 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:¶

[
  "2sqPqwf_Yw9goaPXaJewV7K6C5OkXH3sC8aNRZ2JwPt6ygX5I9S8_Xu7Hf2vTqY2H2
td0bOiJZ2l2KgbKkMHtw",
  "dAl1DDShaQd8JNWxtb_geTjPpdlUvhAYxhjZXQT9m78",
  "ixhgL6Xok1TY8qhJQs5RpUUdwaI2UUth-c1kE_Tp9Is",
  "AlsVYc-OkHzb-jjK11lXIebmaMydqDqInqVe29W2Vpo",
  "sMtqZYvHga5XmI0iXfjt590DUGTkijkW2uBlcxUtNic",
  "LCwZOoqRRM0OePErrPelGxf0TEngY8ZjoDDi2OJLHZo",
  "BJ5DQg-cWglSDDxdmXs1AD0Zkb09a32h3vCEqFdj0PI",
  "d4PaY2wWPAy8xYbK4yYrnZIZAbPKIb0OYScKVd7Er5I",
  "C_z9m-WcOFGUOgx4pEp_Kb4jq4IePH67AX7HeM0QGxQ8sYUUCOqxDsDipQ0irMeTT9
bvSxkMIY5nw5apx3-KDA"
]

Figure 25: Presentation proof (Base64url-Encoded)

The final presented JWP in compact serialization is:¶

eyJhbGciOiJNQUMtSDI1NiIsImF1ZCI6Imh0dHBzOi8vcmVjaXBpZW50LmV4YW1wbGUuY
29tIiwibm9uY2UiOiJLYnl4OU1saC1YVWdiT2RhbTF2Ui1kbDRXSzEzTHRuNnk3bmZ2Rl
VRS0tNIn0.eyJhbGciOiJNQUMtSDI1NiIsImNsYWltcyI6WyJpYXQiLCJleHAiLCJmYW1
pbHlfbmFtZSIsImdpdmVuX25hbWUiLCJlbWFpbCIsImFkZHJlc3MiLCJhZ2Vfb3Zlcl8y
MSJdLCJocGEiOiJFUzI1NiIsImhwayI6eyJjcnYiOiJQLTI1NiIsImt0eSI6IkVDIiwid
XNlIjoic2lnbiIsIngiOiJ4UF83dEkxYWNNRHdFVnhVcC1YdENWeE5Ua3pmUEtVWFlILT
F3OFlzZm5VIiwieSI6IlBrQ1YxSG1ycnVDUmpNNDREQWJkYl8xb3B2MDN4QUVNWmVLYml
oX0NFSlEifSwiaXNzIjoiaHR0cHM6Ly9pc3N1ZXIuZXhhbXBsZSIsInR5cCI6IkpQVCJ9
.MTcxNDUyMTYwMA~MTcxNzE5OTk5OQ~IkRvZSI~IkpheSI~~~.2sqPqwf_Yw9goaPXaJe
wV7K6C5OkXH3sC8aNRZ2JwPt6ygX5I9S8_Xu7Hf2vTqY2H2td0bOiJZ2l2KgbKkMHtw~d
Al1DDShaQd8JNWxtb_geTjPpdlUvhAYxhjZXQT9m78~ixhgL6Xok1TY8qhJQs5RpUUdwa
I2UUth-c1kE_Tp9Is~AlsVYc-OkHzb-jjK11lXIebmaMydqDqInqVe29W2Vpo~sMtqZYv
Hga5XmI0iXfjt590DUGTkijkW2uBlcxUtNic~LCwZOoqRRM0OePErrPelGxf0TEngY8Zj
oDDi2OJLHZo~BJ5DQg-cWglSDDxdmXs1AD0Zkb09a32h3vCEqFdj0PI~d4PaY2wWPAy8x
YbK4yYrnZIZAbPKIb0OYScKVd7Er5I~C_z9m-WcOFGUOgx4pEp_Kb4jq4IePH67AX7HeM
0QGxQ8sYUUCOqxDsDipQ0irMeTT9bvSxkMIY5nw5apx3-KDA

Figure 26: Presented JWP (MAC-H256, JSON, Compact Serialization)

Appendix C. Document History

[[ To be removed from the final specification ]]¶

-13¶

Examples are now built deterministically (using RFC 6979 deterministic ECDSA and seeded random number generation for BBS)¶
Add proof_alg to JWK and CWK to prevent potential collisions between the JWS/JWE algorithm registry, COSE algorithms registry, and JWP algorithms registry¶

-12¶

IANA Considerations section changes from IANA Early Review¶
Updated BLS keys to match BLS Key Representations draft 8¶

-11¶

Change Issuer Protected Header to Issuer Header¶
Change Presentation Protected Header and Holder Presentation Header to Presentation Header¶

-10¶

Clarify MAC issuance and presentation using new "payload slot" nomenclature.¶
Define a new binary "Presentation Internal Representation" so that the holder signature protects the entire presentation¶
Leverage the new "Holder Presentation Algorithm" to allow the holder algorithm to be independent from the signature algorithm used by the issuer¶
Redefine computation of the "Combined MAC Representation" to more closely match the new Presentation Internal Representation.¶
Change the MAC algorithm to directly sign the binary Combined MAC Representation rather than convert it to a JWS.¶
Do not unnecessarily hash the issuer protected header inside the Combined MAC Representation, so that it can provide some manner of domain separation.¶
Clarify how verifiers are to generate the Combined MAC Representation from available information.¶
Provider step-by-step instructions for verification of a presentation¶
Change Proof Key to Issuer Ephemeral Key and Presentation Key to Holder Presentation Key¶

-09¶

Remove JSON serialization¶
Added CBOR (CPT) example to the appendix using SU-ES256¶

-08¶

Made some additional references normative.¶
Corrected SU-ES256 issuer protected header including private keys¶

-07¶

Changing primary editor¶
Update registry template for algorithms to account for integer CBOR labels¶
Restylize initial registry entries for readability¶
Defer BBS key definition to [I-D.ietf-cose-bls-key-representations]¶
Modify example generation to use proof_key and presentation_key names¶
Change proof_jwk to proof_key and presentation_jwk to presentation_key to better represent that the key may be JSON or CBOR-formatted.¶
Moved the registry for proof_key and presentation_key to JWP where they are defined. Consolidated usage, purpose, and requirements from algorithm usage under these definitions.¶
Combined BBS-PROOF into BBS¶

-06¶

Update reference to new repository home¶
Fixed #77: Removed vestigial use of presentation_header.¶
Correct pjwk to presentation_jwk¶

-05¶

Update of appendix describing MAC-H256 to now also be generated by the build system from a common set of code and templates.¶
Update single use algorithm to use an array of octet values rather than requiring splitting an octet buffer into parts during generation of a presentation and during verification.¶
Update BBS algorithm description and examples to clarify the proof is an array with a single octet string.¶
Update MAC algorithm to use an array of octet values for the proof, rather than requiring splitting an octet buffer into parts.¶
Add new section on the Combined MAC Representation to clarify operations are serving to recreate this octet string value.¶
Correct reference to the latest BBS draft.¶
SU and MAC families now use raw JWA rather than JWS and synthesized headers¶
Change algorithms to not use base64url-encoding internally. Algorithms are meant to operate on octets, while base64url-encoding is used to represent those octets in JSON and compact serializations.¶

-04¶

Refactoring figures and examples to be built from a common set across all three documents¶
Move single-use example appendix from JWP to JPA¶
Change algorithm from BBS-DRAFT-5 to BBS, and from BBS-PROOF-DRAFT-5 to BBS-PROOF¶
Update BBS ciphersuite ID to BBS_BLS12381G1_XMD:SHA-256_SSWU_RO_¶
Update to draft 5 BLS key representations¶

-03¶

Improvements resulting from a full proofreading.¶
Populated IANA Considerations section.¶
Updated to use BBS draft -05.¶
Updated examples.¶

-02¶

Add new BBS-DRAFT-3 and BBS-PROOF-DRAFT-3 algorithms based on draft-irtf-cfrg-bbs-signatures-03.¶
Remove prior BBS-X algorithm based on a particular implementation of earlier drafts.¶

-01¶

Correct cross-references within group¶
Describe issuer_header and presentation_header¶
Update BBS references to CFRG drafts¶
Rework reference to HMAC ( RFC2104 )¶
Remove ZKSnark placeholder¶

-00¶

Created initial working group draft based on draft-jmiller-jose-json-proof-algorithms-01¶