Confidence Method v1.0

This specification defines the confidenceMethod property for expressing confidence method information in a credentialSubject in a verifiable credential.

confidenceMethod

If present, the value of the confidenceMethod property is one or more confidence methods as defined below. Each confidence method specifies the specific type of confidence method and any reference data that might be required to evaluate the method. The method is bound to a subject in the verifiable credential and provides enough information for a verifier to evaluate whether a particular candidate party is, for their purposes, the same entity referenced in the credential. THe verifier evaluates the confidence method, executing the process of that method. Successful evaluation indicates the credential has satisfied the confidence method and the verifier can safely rely on that belief to provide services.

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.

assuranceMethod

If present, the value of the assuranceMethod property is one or more assurance methods, defined below. Each assurance method specifies the specific type of assurance method and any reference data that might be required to evaluate the method. The method is bound to a subject in the verifiable credential and provides information about the level of assurance that the issuer had about the subject at the time of issuance. This can help a verifier understand the means by which the verifier established their own level of assurance that for that subject. Different subjects may have different assurance method, allowing the issuer to use different levels of assurance for different subjects in the same credential. For example, an issuer can use a high level of assurance for the subject that is the officiant or spouse in a marriage license, but a lower level of assurance for the witnesses to that ceremony.

Each assurance method MUST specify its type and MAY specify an id. The precise properties and semantics of each assurance method are determined by the specific assuranceMethod 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": { ... }
}

VerificationConfidence

VerificationConfidence specifies how to use a verification method in a controlled identifier document such as a DID document.

BiometricImageConfidence

BiometricImageConfidence specifies how to use an image in a verifiable credential for recognizing the subject of the credential.

NIST_800-63-4_LOA

NIST_800-63-4 defines an assurance method based on the [NIST-SP-800-63-4] specification.

EIDAS_LOA

EIDAS_LOA defines an assurance method based on the [EIDAS2].