Copyright © 2025 the Contributors to the Confidence Method v0.9 Specification, published by the Credentials Community Group under the W3C Community Final Specification Agreement (FSA). A human-readable summary is available.
This specification defines a mechanism that can be used with the Verifiable Credentials Data Model v2.0 to increase a verifier's confidence about a particular subject identified in a verifiable credential.
This specification was published by the Credentials Community Group. It is not a W3C Standard nor is it on the W3C Standards Track. Please note that under the W3C Community Final Specification Agreement (FSA) other conditions apply. Learn more about W3C Community and Business Groups.
This is an experimental specification and is undergoing regular revisions. It is not fit for production deployment.
GitHub Issues are preferred for discussion of this specification. Alternatively, you can send comments to our mailing list. Please send them to public-credentials@w3.org (subscribe, archives).
This section is non-normative.
When a verifier performs the process of validating a verifiable credential, it is useful to be able to raise the confidence level that the subjects identified in a verifiable credential are the same ones that interacted with the issuer when it performed its vetting process to issue the verifiable credential. For example, when an employer (the issuer) issues a corporate identification card to an employee (the subject), it might require that the employee bind a particular cryptographic key (verification method) to the verifiable credential during the issuing process. In that case, the issuer can use this specification to convey to the verifier which cryptographic key was bound during the initial identity assurance process.
In other words, an issuer can use this specification to convey which provable mechanisms it used to bind claims in a verifiable credential so that a verifier can increase their confidence in the truth of a variety of things, including the following:
Terminology used throughout this document is defined in the Terminology section of the Verifiable Credentials Data Model v2.0 and the Verifiable Credential Data Integrity 1.0 specification.
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 and MUST 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 document is any concrete expression of the data model that follows the relevant normative requirements in Section 2. Data Model.
A conforming processor is any algorithm realized as software and/or hardware that generates and/or consumes a conforming document. Conforming processors MUST produce errors when non-conforming documents are consumed.
This specification defines the confidenceMethod property for expressing
confidence method information in a credentialSubject in a verifiable credential.
If present, the value of the confidenceMethod property is one or more
confidence methods. Each confidence method is bound to one or more subjects
in the verifiable credential, and provides enough information for a
verifier to determine whether the holder can generate a verifiable presentation to increase the verifier's confidence that they are the same
entity referenced by the confidence method. This is referred to as satisfying
the confidence method. It is required that the issuer verifies that the
holder can satisfy each confidenceMethod the issuer includes in the
claims of the verifiable credentials they issue.
Each confidence method MUST specify its type and MAY specify an id. The
precise properties and semantics of each confidence method are determined by the
specific confidenceMethod type definition.
A verifier can decide to accept claims in a verifiable credential without requiring use of the confidence method, or use a different mechanism to increase their confidence about whether, for example, the holder is the same entity the issuer made claims about in the verifiable credential. Such a decision can impact the verifier's liability when accepting verifiable credentials during certain use cases.
A verifier can validate that the holder controls, or has been designated
the ability to use, a confidence method by verifying the proof of the verifiable presentation using the information in the
confidence method. The confidence method can include the verification key, or
the type of the confidence method can define that the verification key is to be
inferred from other properties in the verifiable credential, such as the
credentialSubject.id.
The following example demonstrates the various types of confidence methods that can be used, including public cryptographic keys, verification methods, and Decentralized Identifier Documents.
{
"@context": [
"https://www.w3.org/ns/credentials/v2",
"https://www.w3.org/ns/credentials/examples/v2"
],
"id": "http://example.edu/credentials/3732",
"type": ["VerifiableCredential", "UniversityDegreeCredential"],
"issuer": "https://example.edu/issuers/14",
"validFrom": "2010-01-01T19:23:24Z",
"credentialSubject": {
"confidenceMethod": [{
"type": "BiometricPortraitImage",
"image": "data:image/jpeg;base64,/9j/4AAQSkZJRgABAgAAZABkAAD",
}, {
"id": "urn:uuid:818d5ca0-3978-11f0-8658-4f17a1afd652#key-abc",
"type": "JsonWebKey",
"controller": "urn:uuid:818d5ca0-3978-11f0-8658-4f17a1afd652",
"publicKeyJwk": {
"crv": "Ed25519",
"x": "VCpo2LMLhn6iWku8MKvSLg2ZAoC-nlOyPVQaO3FxVeQ",
"kty": "OKP",
"kid": "_Qq0UL2Fq651Q0Fjd6TvnYE-faHiOpRlPVQcY_-tA4A"
}
}, {
"id": "did:example:123#key-567",
"type": "Multikey",
"controller": "did:example:123",
"publicKeyMultibase": "zH3C2AVvLMv6gmMNam3uVAjZpfkcJCwDwnZn6z3wXmqPV"
}, {
"id": "did:example:1234",
"type": "DecentralizedIdentifierDocument"
}],
"degree": {
"type": "BachelorDegree",
"name": "Bachelor of Science and Arts"
}
},
"proof": { ... }
}
A confidence method can express various metadata such as the issuer's level of confidence that the holder is the subject of the verifiable credential, specific form factors or mechanisms of authenticators, and/or references to other verifiable credentials or versioned trust frameworks. For example, an issuer can make a claim about a confidence method that is based on a cryptographic key pair, but to produce a signature using that key, the holder has to unlock a device using multi-factor authentication.