W3C Candidate Recommendation Snapshot
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This specification describes a Data Integrity cryptographic suite for use when creating or verifying a digital signature using the twisted Edwards Curve Digital Signature Algorithm (EdDSA) and Curve25519 (ed25519).
This section describes the status of this document at the time of its publication. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.
The Working Group is actively seeking implementation feedback for this specification. In order to exit the Candidate Recommendation phase, the Working Group has set the requirement of at least two independent implementations for each mandatory feature in the specification. For details on the conformance testing process, see the test suites listed in the implementation report.
This document was published by the Verifiable Credentials Working Group as a Candidate Recommendation Snapshot using the Recommendation track.
Publication as a Candidate Recommendation does not imply endorsement by W3C and its Members. A Candidate Recommendation Snapshot has received wide review, is intended to gather implementation experience, and has commitments from Working Group members to royalty-free licensing for implementations.
This Candidate Recommendation is not expected to advance to Proposed Recommendation any earlier than 24 January 2024.
This document was produced by a group operating under the W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.
This document is governed by the 03 November 2023 W3C Process Document.
This specification defines a cryptographic suite for the purpose of creating, verifying proofs for Ed25519 EdDSA signatures in conformance with the Data Integrity [VC-DATA-INTEGRITY] specification. The approach is accepted by the U.S. National Institute of Standards in the latest FIPS 186-5 publication and meets U.S. Federal Information Processing requirements when using cryptography to secure digital information.
The suites described in this specification use the RDF Dataset Normalization Algorithm [RDF-CANON] or the JSON Canonicalization Scheme [RFC8785] to transform an input document into its canonical form. The canonical representation is then hashed and signed with a detached signature algorithm.
This section defines the terms used in this specification. A link to these terms is included whenever they appear in this specification.
example.com
, an
ad-hoc value such as mycorp-level3-access
, or a very
specific transaction value like 8zF6T8J34qP3mqP
. A signer could
include a domain in its digital proof to restrict its use
to particular target, identified by the specified domain.
id
property in a controller document.
Anything can be a subject: person, group, organization, physical thing, digital
thing, logical thing, etc.
A set of parameters that can be used together with a process to independently verify a proof. For example, a cryptographic public key can be used as a verification method with respect to a digital signature; in such usage, it verifies that the signer possessed the associated cryptographic private key.
"Verification" and "proof" in this definition are intended to apply broadly. For example, a cryptographic public key might be used during Diffie-Hellman key exchange to negotiate a shared symmetric key for encryption. This guarantees the integrity of the key agreement process. It is thus another type of verification method, even though descriptions of the process might not use the words "verification" or "proof."
As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.
The key words MAY, MUST, and MUST NOT in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.
A conforming proof is any concrete expression of the data model that complies with the normative statements in this specification. Specifically, all relevant normative statements in Sections 2. Data Model and 3. Algorithms of this document MUST be enforced.
A conforming processor is any algorithm realized as software and/or hardware that generates or consumes a conforming proof. Conforming processors MUST produce errors when non-conforming documents are consumed.
This document contains examples of JSON and JSON-LD data. Some of these examples
are invalid JSON, as they include features such as inline comments (//
)
explaining certain portions and ellipses (...
) indicating the omission of
information that is irrelevant to the example. These parts would have to be
removed in order to treat the examples as valid JSON or JSON-LD.
The following sections outline the data model that is used by this specification to express verification methods, such as cryptographic public keys, and data integrity proofs, such as digital signatures.
This cryptographic suite is used to verify Data Integrity Proofs [VC-DATA-INTEGRITY] produced using Edwards Curve cryptographic key material. The encoding formats for those key types are provided in this section. Lossless cryptographic key transformation processes that result in equivalent cryptographic key material MAY be used for the processing of digital signatures.
The Multikey format, defined in [VC-DATA-INTEGRITY], is used to express public keys for the cryptographic suites defined in this specification.
The publicKeyMultibase
value of the verification method MUST be 35 bytes in
length and starts with the base-58-btc prefix (z
), as defined in the
Multibase section of
[VC-DATA-INTEGRITY]. A Multibase-encoded Multikey value follows, which MUST
consist of a binary value that starts with the two-byte prefix 0xed01
, which
is the Multikey header for an Ed25519 public key, followed by the 32-byte public
key data, all of which is then encoded using base-58-btc. Any other encoding
MUST NOT be allowed.
Developers are advised to not accidentally publish a representation of a private
key. Implementations of this specification will raise errors if they encounter a
Multikey prefix value other than 0xed01
in a publicKeyMultibase
value.
{ "id": "https://example.com/issuer/123#key-0", "type": "Multikey", "controller": "https://example.com/issuer/123", "publicKeyMultibase": "z6Mkf5rGMoatrSj1f4CyvuHBeXJELe9RPdzo2PKGNCKVtZxP" }
{ "@context": [ "https://www.w3.org/ns/did/v1", "https://w3id.org/security/data-integrity/v1" ], "id": "did:example:123", "verificationMethod": [{ "id": "did:example:123#key-0", "type": "Multikey", "controller": "did:example:123", "publicKeyMultibase": "z6Mkf5rGMoatrSj1f4CyvuHBeXJELe9RPdzo2PKGNCKVtZxP" }], "authentication": [ "did:example:123#key-0" ], "assertionMethod": [ "did:example:123#key-0" ], "capabilityDelegation": [ "did:example:123#key-0" ], "capabilityInvocation": [ "did:example:123#key-0" ] }
The secretKeyMultibase
property represents a Multibase-encoded Multikey
expression of an Ed25519 secret key (sometimes also referred to as a private
key). The value starts with the two-byte prefix 0x8026
,
followed by the 32-byte Ed25519 secret key data. The combined
34-byte value is then base58-btc encoded and z
is added as the prefix on the
encoded value.
Developers are advised to prevent accidental publication of a representation of
a secret key, and to not export the secretKeyMultibase
property by default,
when serializing key pairs to Multikey.
This section details the proof representation formats that are defined by this specification.
The verificationMethod
property of the proof MUST be a URL.
Dereferencing the verificationMethod
MUST result in an object
containing a type
property with the value set to
Multikey
.
The type
property of the proof MUST be DataIntegrityProof
.
The cryptosuite
property of the proof MUST be eddsa-rdfc-2022
or eddsa-jcs-2022
.
The created
property of the proof MUST be an [XMLSCHEMA11-2]
formatted date string.
The proofPurpose
property of the proof MUST be a string, and MUST
match the verification relationship expressed by the verification method
controller
.
The proofValue
property of the proof MUST be a detached EdDSA
produced according to [RFC8032], encoded using the base-58-btc header and
alphabet as described in the
Multibase section of
[VC-DATA-INTEGRITY].
{ "@context": [ {"myWebsite": "https://vocabulary.example/myWebsite"}, "https://www.w3.org/ns/credentials/v2" ], "myWebsite": "https://hello.world.example/", "proof": { "type": "DataIntegrityProof", "cryptosuite": "eddsa-rdfc-2022", "created": "2023-02-24T23:36:38Z", "verificationMethod": "https://vc.example/issuers/5678#z6MkrJVnaZkeFzdQyMZu1 cgjg7k1pZZ6pvBQ7XJPt4swbTQ2", "proofPurpose": "assertionMethod", "proofValue": "z5C5b1uzYJN6pDR3aWgAqUMoSB1JY29epA74qyjaie9qh4okm9DZP6y77eTNq 5NfYyMwNu9bpQQWUHKH5zAmEtszK" } }
The following section describes multiple Data Integrity cryptographic suites that utilize the twisted Edwards Curve Digital Signature Algorithm.
The eddsa-rdfc-2022
cryptographic suite takes an input document, canonicalizes
the document using the Universal RDF Dataset Canonicalization Algorithm
[RDF-CANON], and then cryptographically hashes and signs the output
resulting in the production of a data integrity proof. The algorithms in this
section also include the verification of such a data integrity proof.
When the RDF Dataset Canonicalization Algorithm [RDF-CANON] is used, implementations will detect dataset poisoning by default, and abort processing upon such detection.
To generate a proof, the algorithm in Section 4.1: Add Proof in the Data Integrity [VC-DATA-INTEGRITY] specification MUST be executed. For that algorithm, the cryptographic suite specific transformation algorithm is defined in Section 3.1.3 Transformation (eddsa-rdfc-2022), the hashing algorithm is defined in Section 3.1.4 Hashing (eddsa-rdfc-2022), and the proof serialization algorithm is defined in Section 3.1.6 Proof Serialization (eddsa-rdfc-2022).
To verify a proof, the algorithm in Section 4.2: Verify Proof in the Data Integrity [VC-DATA-INTEGRITY] specification MUST be executed. For that algorithm, the cryptographic suite specific transformation algorithm is defined in Section 3.1.3 Transformation (eddsa-rdfc-2022), the hashing algorithm is defined in Section 3.1.4 Hashing (eddsa-rdfc-2022), and the proof verification algorithm is defined in Section 3.1.7 Proof Verification (eddsa-rdfc-2022).
The following algorithm specifies how to transform an unsecured input document into a transformed document that is ready to be provided as input to the hashing algorithm in Section 3.1.4 Hashing (eddsa-rdfc-2022).
Required inputs to this algorithm are an unsecured data document (unsecuredDocument) and transformation options (options). The transformation options MUST contain a type identifier for the cryptographic suite (type) and a cryptosuite identifier (cryptosuite). A transformed data document is produced as output. Whenever this algorithm encodes strings, it MUST use UTF-8 encoding.
DataIntegrityProof
and options.cryptosuite is not
set to the string eddsa-rdfc-2022
then a PROOF_TRANSFORMATION_ERROR
MUST be
raised.
The following algorithm specifies how to cryptographically hash a transformed data document and proof configuration into cryptographic hash data that is ready to be provided as input to the algorithms in Section 3.1.6 Proof Serialization (eddsa-rdfc-2022) or Section 3.1.7 Proof Verification (eddsa-rdfc-2022).
The required inputs to this algorithm are a transformed data document (transformedDocument) and canonical proof configuration (canonicalProofConfig). A single hash data value represented as series of bytes is produced as output.
The following algorithm specifies how to generate a proof configuration from a set of proof options that is used as input to the proof hashing algorithm.
The required inputs to this algorithm are proof options (options). The proof options MUST contain a type identifier for the cryptographic suite (type) and MUST contain a cryptosuite identifier (cryptosuite). A proof configuration object is produced as output.
DataIntegrityProof
and
proofConfig.cryptosuite is not set to eddsa-rdfc-2022
, an
INVALID_PROOF_CONFIGURATION
error MUST be raised.
INVALID_PROOF_DATETIME
error MUST be raised.
The following algorithm specifies how to serialize a digital signature from a set of cryptographic hash data. This algorithm is designed to be used in conjunction with the algorithms defined in the Data Integrity [VC-DATA-INTEGRITY] specification, Section 4: Algorithms. Required inputs are cryptographic hash data (hashData) and proof options (options). The proof options MUST contain a type identifier for the cryptographic suite (type) and MAY contain a cryptosuite identifier (cryptosuite). A single digital proof value represented as series of bytes is produced as output.
Ed25519
variant
(Pure EdDSA), with hashData as the data to be signed using
the private key specified by privateKeyBytes.
proofBytes will be exactly 64 bytes in size.
The following algorithm specifies how to verify a digital signature from a set of cryptographic hash data. This algorithm is designed to be used in conjunction with the algorithms defined in the Data Integrity [VC-DATA-INTEGRITY] specification, Section 4: Algorithms. Required inputs are cryptographic hash data (hashData), a digital signature (proofBytes) and proof options (options). A verification result represented as a boolean value is produced as output.
Ed25519
variant (Pure EdDSA),
with hashData as the data to be verified against the
proofBytes using the public key specified by
publicKeyBytes.
The eddsa-jcs-2022
cryptographic suite takes an input document, canonicalizes
the document using the JSON Canonicalization Scheme [RFC8785], and then
cryptographically hashes and signs the output resulting in the production of a
data integrity proof. The algorithms for this cryptographic suite are the
same as the ones in Section 3.1 eddsa-rdfc-2022 except for the following
modifications:
In Section 3.1.3 Transformation (eddsa-rdfc-2022), step 1) and step 2) are replaced by the following text:
DataIntegrityProof
and options.cryptosuite is not
set to the string eddsa-jcs-2022
then a PROOF_TRANSFORMATION_ERROR
MUST be
raised.
In Section 3.1.5 Proof Configuration (eddsa-rdfc-2022), step 8) is not performed, and steps 4) and 9) are replaced by the following text:
4) If options.type is not set to
DataIntegrityProof
and proofConfig.cryptosuite is not
set to eddsa-jcs-2022
, an INVALID_PROOF_CONFIGURATION
error MUST be raised.
9) Let canonicalProofConfig be the result of applying the JSON Canonicalization Scheme [RFC8785] to the proofConfig.
Before reading this section, readers are urged to familiarize themselves with general security advice provided in the Security Considerations section of the Data Integrity specification.
The following section describes security considerations that developers implementing this specification should be aware of in order to create secure software.
This section is non-normative.
Ed25519 signatures (EdDSA algorithm with edwards25519 curve) have been widely adopted, due both to the compact size of the keys and signatures and to the speed at which signatures can be produced and verified. Many libraries exist that can create and verify Ed25519 signatures. Since the publication of [RFC8032], security properties of Ed25519 signatures have been rigorously proven (see [Provable_Ed25519] and [Taming_EdDSAs]). However, it has been observed that a significant number of libraries do not achieve these security levels, due to missing input validity checks during the signature verification process. In this section, we summarize the security levels achievable with Ed25519 signatures, and indicate how one can determine whether a library will support those levels.
Digital signatures may exhibit a number of desirable cryptographic properties [Taming_EdDSAs] among these are:
EUF-CMA (existential unforgeability under chosen message attacks) is usually the minimal security property required of a signature scheme. It guarantees that any efficient adversary who has the public key $\begin{array}{c}pk\end{array}$ of the signer and received an arbitrary number of signatures on messages of its choice (in an adaptive manner): $\begin{array}{c}\{{m}_{i},{\sigma}_{i}{\}}_{i=1}^{N}\end{array}$, cannot output a valid signature $\begin{array}{c}{\sigma}^{\ast}\end{array}$ for a new message $\begin{array}{c}{m}^{\ast}\notin \{{m}_{i}{\}}_{i=1}^{N}\end{array}$ (except with negligible probability). In case the attacker outputs a valid signature on a new message: $\begin{array}{c}({m}^{\ast},{\sigma}^{\ast})\end{array}$, it is called an existential forgery.
SUF-CMA (strong unforgeability under chosen message attacks) is a stronger notion than EUF-CMA. It guarantees that for any efficient adversary who has the public key $\begin{array}{c}pk\end{array}$ of the signer and received an arbitrary number of signatures on messages of its choice: $\begin{array}{c}\{{m}_{i},{\sigma}_{i}{\}}_{i=1}^{N}\end{array}$, it cannot output a new valid signature pair $\begin{array}{c}({m}^{\ast},{\sigma}^{\ast})\end{array}$, such that $\begin{array}{c}({m}^{\ast},{\sigma}^{\ast})\notin \{{m}^{i},{\sigma}^{i}{\}}_{i=1}^{N}\end{array}$ (except with negligible probability). Strong unforgeability implies that an adversary cannot only sign new messages, but also cannot find a new signature on an old message. See [Provable_Ed25519] for a real world attack that would have been circumvented with SUF-CMA security over EUF-CMA security.
Binding signature (BS) We say that a signature scheme is binding if no efficient signer can output a tuple $\begin{array}{c}[pk,m,{m}^{\prime},\sigma ]\end{array}$, where both $\begin{array}{c}(m,\sigma )\end{array}$ and $\begin{array}{c}({m}^{\prime},\sigma )\end{array}$ are valid message signature pairs under the public key $\begin{array}{c}pk\end{array}$ and $\begin{array}{c}m\ne {m}^{\prime}\end{array}$ (except with negligible probability). A binding signature makes it impossible for the signer to claim later that it has signed a different message, the signature binds the signer to the message.
Strongly Binding signature (SBS) Certain applications may require a signature to not only be binding to the message but also be binding to the public key. We say that a signature scheme is strongly-binding if any efficient signer can not output a tuple $\begin{array}{c}[pk,m,p{k}^{\prime},{m}^{\prime},\sigma ]\end{array}$, where $\begin{array}{c}(m,\sigma )\end{array}$ is a valid signature for the public key $\begin{array}{c}pk\end{array}$ and $\begin{array}{c}({m}^{\prime},\sigma )\end{array}$ is a valid signature for the public key $\begin{array}{c}p{k}^{\prime}\end{array}$ and either $\begin{array}{c}{m}^{\prime}\ne m\end{array}$ or $\begin{array}{c}pk\ne p{k}^{\prime}\end{array}$, or both (except with negligible probability). See [Provable_Ed25519] for real world attacks that would have been circumvented with the SBS property.
Note that the BS and SBS properties are forms of non-repudiation.
As pointed on in [Taming_EdDSAs] flaws in Ed25519 libraries primarily occur on the signature verification side where sometimes edge cases are not properly checked. An Ed25519 signature library that is in conformance with [RFC8032] or [FIPS-186-5], i.e., one that performs all specified validation checks, will have the SUF-CMA property in addition to EUF-CMA.
Reference [Taming_EdDSAs] achieves the BS and SBS properties along with SUF-CMA in their "signature verification algorithm 2" where an additional check is performed against the public key A to make sure that it is not one of eight "small order points". These additional checks incur minimal processing overhead.
Reference [Taming_EdDSAs] included a set of twelve test vectors to test various Ed25519 libraries available at the time of publication. They found that a significant portion missed edge cases and hence did not achieve SUF-CMA (just EUF-CMA) and only two libraries out of sixteen achieved all the security properties. Since the time of publication more Ed25519 libraries have been created and some of the libraries have been updated to include all verification checks. Implementers are recommended to test the Ed25519 library they are using against the test vectors of [Taming_EdDSAs].
Before reading this section, readers are urged to familiarize themselves with general privacy advice provided in the Privacy Considerations section of the Data Integrity specification.
The following section describes privacy considerations that developers implementing this specification should be aware of in order to avoid violating privacy assumptions.
This cryptography suite does not provide for selective disclosure or unlinkability. If signatures are re-used, they can be used as correlatable data.
Ed25519Signature2020
is an earlier version of a cryptographic suite
for the usage of the EdDSA algorithm and Curve25519. While it has
been used in production systems, new implementations should use edssa-2022
instead. It has been kept in this specification to provide a stable reference.
We need to add documentation to note that this key format is deployed and
widely used in production, but is deprecated. Multikey
and JsonWebKey2020
supersede it.
The type
of the verification method MUST be
Ed25519VerificationKey2020.
The controller
of the verification method MUST be a URL.
The publicKeyMultibase
value of the verification method MUST be 35 bytes in
length and starts with the base-58-btc prefix (z
), as defined in the
Multibase section of
[VC-DATA-INTEGRITY]. A Multibase-encoded Multikey value follows, which MUST
consist of a binary value that starts with the two-byte prefix 0xed01
, which
is the Multikey header for an Ed25519 public key, followed by the 32-byte public
key data, all of which is then encoded using base-58-btc. Any other encoding
MUST NOT be allowed.
Developers are advised to not accidentally publish a representation of a private
key. Implementations of this specification will raise errors in the event of a
Multikey header value other than 0xed01
being used in a
publicKeyMultibase
value.
{ "id": "https://example.com/issuer/123#key-0", "type": "Ed25519VerificationKey2020", "controller": "https://example.com/issuer/123", "publicKeyMultibase": "z6Mkf5rGMoatrSj1f4CyvuHBeXJELe9RPdzo2PKGNCKVtZxP" }
{ "@context": [ "https://www.w3.org/ns/did/v1", "https://w3id.org/security/suites/ed25519-2020/v1" ], "id": "did:example:123", "verificationMethod": [{ "id": "did:example:123#key-0", "type": "Ed25519VerificationKey2020", "controller": "did:example:123", "publicKeyMultibase": "z6Mkf5rGMoatrSj1f4CyvuHBeXJELe9RPdzo2PKGNCKVtZxP" }], "authentication": [ "did:example:123#key-0" ], "assertionMethod": [ "did:example:123#key-0" ], "capabilityDelegation": [ "did:example:123#key-0" ], "capabilityInvocation": [ "did:example:123#key-0" ] }
The verificationMethod
property of the proof MUST be a URL.
Dereferencing the verificationMethod
MUST result in an object
containing a type
property with the value set to
Ed25519VerificationKey2020
.
The type
property of the proof MUST be Ed25519Signature2020
.
The created
property of the proof MUST be an [XMLSCHEMA11-2]
formatted date string.
The proofPurpose
property of the proof MUST be a string, and MUST
match the verification relationship expressed by the verification method
controller
.
The proofValue
property of the proof MUST be a detached EdDSA
produced according to [RFC8032], encoded using
the base-58-btc header and alphabet as described in the
Multibase section of [VC-DATA-INTEGRITY].
{ "@context": [ {"myWebsite": "https://vocabulary.example/myWebsite"}, "https://w3id.org/security/data-integrity/v1" ], "myWebsite": "https://hello.world.example/", "proof": { "type": "Ed25519Signature2020", "created": "2020-11-05T19:23:24Z", "verificationMethod": "https://di.example/issuer#z6MkjLrk3gKS2nnkeWcmcxiZPGskmesDpuwRBorgHxUXfxnG", "proofPurpose": "assertionMethod", "proofValue": "z4oey5q2M3XKaxup3tmzN4DRFTLVqpLMweBrSxMY2xHX5XTYVQeVbY8nQAVHMrXFkXJpmEcqdoDwLWxaqA3Q1geV6" } }
The Ed25519Signature2020
cryptographic suite takes an input document,
canonicalizes the document using the Universal RDF Dataset Canonicalization
Algorithm [RDF-CANON], and then cryptographically hashes and signs the output
resulting in the production of a data integrity proof. The algorithms in this
section also include the verification of such a data integrity proof.
To generate a proof, the algorithm in Section 4.1: Add Proof in the Data Integrity [VC-DATA-INTEGRITY] specification MUST be executed. For that algorithm, the cryptographic suite specific transformation algorithm is defined in Section A.2.1.3 Transformation (Ed25519Signature2020), the hashing algorithm is defined in Section A.2.1.4 Hashing (Ed25519Signature2020), and the proof serialization algorithm is defined in Section A.2.1.6 Proof Serialization (Ed25519Signature2020).
To verify a proof, the algorithm in Section 4.2: Verify Proof in the Data Integrity [VC-DATA-INTEGRITY] specification MUST be executed. For that algorithm, the cryptographic suite specific transformation algorithm is defined in Section A.2.1.3 Transformation (Ed25519Signature2020), the hashing algorithm is defined in Section A.2.1.4 Hashing (Ed25519Signature2020), and the proof verification algorithm is defined in Section A.2.1.7 Proof Verification (Ed25519Signature2020).
The following algorithm specifies how to transform an unsecured input document into a transformed document that is ready to be provided as input to the hashing algorithm in Section A.2.1.4 Hashing (Ed25519Signature2020).
Required inputs to this algorithm are an unsecured data document (unsecuredDocument) and transformation options (options). The transformation options MUST contain a type identifier for the cryptographic suite (type) and a cryptosuite identifier (cryptosuite). A transformed data document is produced as output. Whenever this algorithm encodes strings, it MUST use UTF-8 encoding.
Ed25519Signature2020
, then a PROOF_TRANSFORMATION_ERROR
MUST be raised.
The following algorithm specifies how to cryptographically hash a transformed data document and proof configuration into cryptographic hash data that is ready to be provided as input to the algorithms in Section A.2.1.6 Proof Serialization (Ed25519Signature2020) or Section A.2.1.7 Proof Verification (Ed25519Signature2020).
The required inputs to this algorithm are a transformed data document (transformedDocument) and proof configuration (proofConfig). The proof configuration MUST contain a type identifier for the cryptographic suite (type) and MAY contain a cryptosuite identifier (cryptosuite). A single hash data value represented as series of bytes is produced as output.
The following algorithm specifies how to generate a proof configuration from a set of proof options that is used as input to the proof hashing algorithm.
The required inputs to this algorithm are proof options (options). The proof options MUST contain a type identifier for the cryptographic suite (type) and MAY contain a cryptosuite identifier (cryptosuite). A proof configuration object is produced as output.
Ed25519Signature2020
, an
INVALID_PROOF_CONFIGURATION
error MUST be raised.
INVALID_PROOF_DATETIME
error MUST be raised.
The following algorithm specifies how to serialize a digital signature from a set of cryptographic hash data. This algorithm is designed to be used in conjunction with the algorithms defined in the Data Integrity [VC-DATA-INTEGRITY] specification, Section 4: Algorithms. Required inputs are cryptographic hash data (hashData) and proof options (options). The proof options MUST contain a type identifier for the cryptographic suite (type) and MAY contain a cryptosuite identifier (cryptosuite). A single digital proof value represented as series of bytes is produced as output.
Ed25519
variant
(Pure EdDSA), with hashData as the data to be signed using
the private key specified by privateKeyBytes.
proofBytes will be exactly 64 bytes in size.
The following algorithm specifies how to verify a digital signature from a set of cryptographic hash data. This algorithm is designed to be used in conjunction with the algorithms defined in the Data Integrity [VC-DATA-INTEGRITY] specification, Section 4: Algorithms. Required inputs are cryptographic hash data (hashData), a digital signature (proofBytes) and proof options (options). A verification result represented as a boolean value is produced as output.
Ed25519
variant (Pure EdDSA),
with hashData as the data to be verified against the
proofBytes using the public key specified by
publicKeyBytes.
This section is non-normative.
The signer needs to generate a private/public key pair with the private key used for signing and the public key made available for verification. The representation of the public key and the representation of the private key are shown below.
{ publicKeyMultibase: "z6MkrJVnaZkeFzdQyMZu1cgjg7k1pZZ6pvBQ7XJPt4swbTQ2", privateKeyMultibase: "z3u2en7t5LR2WtQH5PfFqMqwVHBeXouLzo6haApm8XHqvjxq" }
Signing begins with a credential without an attached proof, which is converted to canonical form, and then hashed, as shown in the following three examples.
{ "@context": [ "https://www.w3.org/ns/credentials/v2", "https://www.w3.org/ns/credentials/examples/v2" ], "id": "urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33", "type": ["VerifiableCredential", "AlumniCredential"], "name": "Alumni Credential", "description": "A minimum viable example of an Alumni Credential.", "issuer": "https://vc.example/issuers/5678", "validFrom": "2023-01-01T00:00:00Z", "credentialSubject": { "id": "did:example:abcdefgh", "alumniOf": "The School of Examples" } }
<did:example:abcdefgh> <https://www.w3.org/ns/credentials/examples#alumniOf> "The School of Examples" . <urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <https://www.w3.org/2018/credentials#VerifiableCredential> . <urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <https://www.w3.org/ns/credentials/examples#AlumniCredential> . <urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33> <https://schema.org/description> "A minimum viable example of an Alumni Credential." . <urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33> <https://schema.org/name> "Alumni Credential" . <urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33> <https://www.w3.org/2018/credentials#credentialSubject> <did:example:abcdefgh> . <urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33> <https://www.w3.org/2018/credentials#issuer> <https://vc.example/issuers/5678> . <urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33> <https://www.w3.org/2018/credentials#validFrom> "2023-01-01T00:00:00Z"^^<http://www.w3.org/2001/XMLSchema#dateTime> .
517744132ae165a5349155bef0bb0cf2258fff99dfe1dbd914b938d775a36017
The next step is to take the proof options document, convert it to canonical form, and obtain its hash, as shown in the next three examples.
{ "type": "DataIntegrityProof", "cryptosuite": "eddsa-rdfc-2022", "created": "2023-02-24T23:36:38Z", "verificationMethod": "https://vc.example/issuers/5678#z6MkrJVnaZkeFzdQyMZu1cgjg7k1pZZ6pvBQ7XJPt4swbTQ2", "proofPurpose": "assertionMethod", "@context": [ "https://www.w3.org/ns/credentials/v2", "https://www.w3.org/ns/credentials/examples/v2" ] }
_:c14n0 <http://purl.org/dc/terms/created> "2023-02-24T23:36:38Z"^^<http://www.w3.org/2001/XMLSchema#dateTime> . _:c14n0 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <https://w3id.org/security#DataIntegrityProof> . _:c14n0 <https://w3id.org/security#cryptosuite> "eddsa-rdfc-2022"^^<https://w3id.org/security#cryptosuiteString> . _:c14n0 <https://w3id.org/security#proofPurpose> <https://w3id.org/security#assertionMethod> . _:c14n0 <https://w3id.org/security#verificationMethod> <https://vc.example/issuers/5678#z6MkrJVnaZkeFzdQyMZu1cgjg7k1pZZ6pvBQ7XJPt4swbTQ2> .
4c4d3890a157f8d611b13c265c2c22f39aa0a567c7c7dd9ba3e45cd579784eeb
Finally, we concatenate the hash of the proof options followed by the hash of the credential without proof, use the private key with the combined hash to compute the Ed25519 signature, and then base58-btc encode the signature.
4c4d3890a157f8d611b13c265c2c22f39aa0a567c7c7dd9ba3e45cd579784eeb517744132ae165a5349155bef0bb0cf2258fff99dfe1dbd914b938d775a36017
3237ba3b695c09e199540507ead17a58300cc4efe91ce19d582ad7e001455190f1ea3d13bdeff2cbaf7f30da7fe9f24b475511ef3875b6efe7cc9f49d3f55b02
z21EVs3eXERqTn4acNHT9viboqgzUaQ3kTmhPT3eA8qrVPE7CrQq78WkzctnMX5W4CrzcKnHw8V6dvy5pgWYCU5e9
Assemble the signed credential with the following two steps:
proofValue
field with the previously computed base58-btc
value to the proof options document.
proof
field of the credential to the augmented proof
option document.
{ "@context": [ "https://www.w3.org/ns/credentials/v2", "https://www.w3.org/ns/credentials/examples/v2" ], "id": "urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33", "type": [ "VerifiableCredential", "AlumniCredential" ], "name": "Alumni Credential", "description": "A minimum viable example of an Alumni Credential.", "issuer": "https://vc.example/issuers/5678", "validFrom": "2023-01-01T00:00:00Z", "credentialSubject": { "id": "did:example:abcdefgh", "alumniOf": "The School of Examples" }, "proof": { "type": "DataIntegrityProof", "cryptosuite": "eddsa-rdfc-2022", "created": "2023-02-24T23:36:38Z", "verificationMethod": "https://vc.example/issuers/5678#z6MkrJVnaZkeFzdQyMZu1cgjg7k1pZZ6pvBQ7XJPt4swbTQ2", "proofPurpose": "assertionMethod", "proofValue": "z21EVs3eXERqTn4acNHT9viboqgzUaQ3kTmhPT3eA8qrVPE7CrQq78WkzctnMX5W4CrzcKnHw8V6dvy5pgWYCU5e9" } }
The signer needs to generate a private/public key pair with the private key used for signing and the public key made available for verification. The representation of the public key, and the representation of the private key are shown below.
{ publicKeyMultibase: "z6MkrJVnaZkeFzdQyMZu1cgjg7k1pZZ6pvBQ7XJPt4swbTQ2", privateKeyMultibase: "z3u2en7t5LR2WtQH5PfFqMqwVHBeXouLzo6haApm8XHqvjxq" }
Signing begins with a credential without an attached proof, which is converted to canonical form, and then hashed, as shown in the following three examples.
{ "@context": [ "https://www.w3.org/ns/credentials/v2", "https://www.w3.org/ns/credentials/examples/v2" ], "id": "urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33", "type": ["VerifiableCredential", "AlumniCredential"], "name": "Alumni Credential", "description": "A minimum viable example of an Alumni Credential.", "issuer": "https://vc.example/issuers/5678", "validFrom": "2023-01-01T00:00:00Z", "credentialSubject": { "id": "did:example:abcdefgh", "alumniOf": "The School of Examples" } }
{"@context":["https://www.w3.org/ns/credentials/v2","https://www.w3.org/ns/credentials/examples/v2"],"credentialSubject":{"alumniOf":"The School of Examples","id":"did:example:abcdefgh"},"description":"A minimum viable example of an Alumni Credential.","id":"urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33","issuer":"https://vc.example/issuers/5678","name":"Alumni Credential","type":["VerifiableCredential","AlumniCredential"],"validFrom":"2023-01-01T00:00:00Z"}
59b7cb6251b8991add1ce0bc83107e3db9dbbab5bd2c28f687db1a03abc92f19
The next step is to take the proof options document, convert it to canonical form, and obtain its hash, as shown in the next three examples.
{ "type": "DataIntegrityProof", "cryptosuite": "eddsa-jcs-2022", "created": "2023-02-24T23:36:38Z", "verificationMethod": "https://vc.example/issuers/5678#z6MkrJVnaZkeFzdQyMZu1cgjg7k1pZZ6pvBQ7XJPt4swbTQ2", "proofPurpose": "assertionMethod" }
{"created":"2023-02-24T23:36:38Z","cryptosuite":"eddsa-jcs-2022","proofPurpose":"assertionMethod","type":"DataIntegrityProof","verificationMethod":"https://vc.example/issuers/5678#z6MkrJVnaZkeFzdQyMZu1cgjg7k1pZZ6pvBQ7XJPt4swbTQ2"}
56d860737b1bc788da1f5c5a506115278314559a680f37976502c9b3ed1f38f4
Finally, we concatenate the hash of the proof options followed by the hash of the credential without proof, use the private key with the combined hash to compute the Ed25519 signature, and then base58-btc encode the signature.
56d860737b1bc788da1f5c5a506115278314559a680f37976502c9b3ed1f38f459b7cb6251b8991add1ce0bc83107e3db9dbbab5bd2c28f687db1a03abc92f19
7717cab27b6a4d91a472922d0ec071ead8297ce65c47436ca95b98c646d109abbd0c52cab09e83af605e2d896f29a30bbf81cbe0c2089a7193d908c96eaf6106
z3P6rHMUaWG6e3Ac6xYFht8aEvoVXndgKTtEY8kzWYXzk8dKmAo2GJeZiJw4qoZ2PGp4ugdaHx3oQiLpeFBLDqP2M
Assemble the signed credential with the following two steps:
proofValue
field with the previously computed base58-btc
value to the proof options document.
proof
field of the credential to the augmented proof
option document.
{ "@context": [ "https://www.w3.org/ns/credentials/v2", "https://www.w3.org/ns/credentials/examples/v2" ], "id": "urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33", "type": [ "VerifiableCredential", "AlumniCredential" ], "name": "Alumni Credential", "description": "A minimum viable example of an Alumni Credential.", "issuer": "https://vc.example/issuers/5678", "validFrom": "2023-01-01T00:00:00Z", "credentialSubject": { "id": "did:example:abcdefgh", "alumniOf": "The School of Examples" }, "proof": { "type": "DataIntegrityProof", "cryptosuite": "eddsa-jcs-2022", "created": "2023-02-24T23:36:38Z", "verificationMethod": "https://vc.example/issuers/5678#z6MkrJVnaZkeFzdQyMZu1cgjg7k1pZZ6pvBQ7XJPt4swbTQ2", "proofPurpose": "assertionMethod", "proofValue": "z3P6rHMUaWG6e3Ac6xYFht8aEvoVXndgKTtEY8kzWYXzk8dKmAo2GJeZiJw4qoZ2PGp4ugdaHx3oQiLpeFBLDqP2M" } }
The signer needs to generate a private/public key pair with the private key used for signing and the public key made available for verification. The representation of the public key, and the representation of the private key, are shown below.
{ publicKeyMultibase: "z6MkrJVnaZkeFzdQyMZu1cgjg7k1pZZ6pvBQ7XJPt4swbTQ2", privateKeyMultibase: "z3u2en7t5LR2WtQH5PfFqMqwVHBeXouLzo6haApm8XHqvjxq" }
Signing begins with a credential without an attached proof, which is converted to canonical form, and then hashed, as shown in the following three examples.
{ "@context": [ "https://www.w3.org/ns/credentials/v2", "https://www.w3.org/ns/credentials/examples/v2" ], "id": "urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33", "type": ["VerifiableCredential", "AlumniCredential"], "name": "Alumni Credential", "description": "A minimum viable example of an Alumni Credential.", "issuer": "https://vc.example/issuers/5678", "validFrom": "2023-01-01T00:00:00Z", "credentialSubject": { "id": "did:example:abcdefgh", "alumniOf": "The School of Examples" } }
<did:example:abcdefgh> <https://www.w3.org/ns/credentials/examples#alumniOf> "The School of Examples" . <urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <https://www.w3.org/2018/credentials#VerifiableCredential> . <urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <https://www.w3.org/ns/credentials/examples#AlumniCredential> . <urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33> <https://schema.org/description> "A minimum viable example of an Alumni Credential." . <urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33> <https://schema.org/name> "Alumni Credential" . <urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33> <https://www.w3.org/2018/credentials#credentialSubject> <did:example:abcdefgh> . <urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33> <https://www.w3.org/2018/credentials#issuer> <https://vc.example/issuers/5678> . <urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33> <https://www.w3.org/2018/credentials#validFrom> "2023-01-01T00:00:00Z"^^<http://www.w3.org/2001/XMLSchema#dateTime> .
517744132ae165a5349155bef0bb0cf2258fff99dfe1dbd914b938d775a36017
The next step is to take the proof options document, convert it to canonical form, and obtain its hash, as shown in the next three examples.
{ "type": "Ed25519Signature2020", "created": "2023-02-24T23:36:38Z", "verificationMethod": "https://vc.example/issuers/5678#z6MkrJVnaZkeFzdQyMZu1cgjg7k1pZZ6pvBQ7XJPt4swbTQ2", "proofPurpose": "assertionMethod", "@context": [ "https://www.w3.org/ns/credentials/v2", "https://www.w3.org/ns/credentials/examples/v2" ] }
_:c14n0 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <https://www.w3.org/ns/credentials/examples#Ed25519Signature2020> . _:c14n0 <https://www.w3.org/ns/credentials/examples#created> "2023-02-24T23:36:38Z" . _:c14n0 <https://www.w3.org/ns/credentials/examples#proofPurpose> "assertionMethod" . _:c14n0 <https://www.w3.org/ns/credentials/examples#verificationMethod> "https://vc.example/issuers/5678#z6MkrJVnaZkeFzdQyMZu1cgjg7k1pZZ6pvBQ7XJPt4swbTQ2" .
7094c8ac655f5d26034b866d14cd99eba3d32562408d9c286b64a65fb79e0b2d
Finally, we concatenate the hash of the proof options followed by the hash of the credential without proof, use the private key with the combined hash to compute the Ed25519 signature, and then base58-btc encode the signature.
7094c8ac655f5d26034b866d14cd99eba3d32562408d9c286b64a65fb79e0b2d517744132ae165a5349155bef0bb0cf2258fff99dfe1dbd914b938d775a36017
4527642e1538a97ef38db08fd45cf2d4d04d510231bb83c5991d7a74bcfe9cc5213f956537cc3a7eda1e372e184a9f32285808a0d1ec75db3dc5268727ed0a01
z2PC6JBDG1otY3PfnxGnvHCuh8tEqPPNpDggvsnzjr2yKxszQg5bJXsQhV1ZUTG6KBNGdvWVzVqFxtLagbdoRUjf6
Assemble the signed credential with the following two steps:
proofValue
field with the previously computed base58-btc
value to the proof options document.
proof
field of the credential to the augmented proof
option document.
{ "@context": [ "https://www.w3.org/ns/credentials/v2", "https://www.w3.org/ns/credentials/examples/v2" ], "id": "urn:uuid:58172aac-d8ba-11ed-83dd-0b3aef56cc33", "type": [ "VerifiableCredential", "AlumniCredential" ], "name": "Alumni Credential", "description": "A minimum viable example of an Alumni Credential.", "issuer": "https://vc.example/issuers/5678", "validFrom": "2023-01-01T00:00:00Z", "credentialSubject": { "id": "did:example:abcdefgh", "alumniOf": "The School of Examples" }, "proof": { "type": "Ed25519Signature2020", "created": "2023-02-24T23:36:38Z", "verificationMethod": "https://vc.example/issuers/5678#z6MkrJVnaZkeFzdQyMZu1cgjg7k1pZZ6pvBQ7XJPt4swbTQ2", "proofPurpose": "assertionMethod", "proofValue": "z2PC6JBDG1otY3PfnxGnvHCuh8tEqPPNpDggvsnzjr2yKxszQg5bJXsQhV1ZUTG6KBNGdvWVzVqFxtLagbdoRUjf6" } }
This section is non-normative.
This section contains the substantive changes that have been made to this specification over time.
Changes since the First Public Working Draft: