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Credential Revocation

Some types of Verifiable Credentials require the ability to be revoked by the Entity that issued them. An example could be a University Credential that needs to be revoked once the student (Credential holder) has graduated. The W3C Verifiable Credential spec has a property to track the status of a Credential. Upon receiving a Credential, a Verifier should check that the Credential has not been revoked. The Verifier should not have to contact the Issuer of the Credential to verify this information. Revocation Registries and Status Lists have been outlined as solutions for verifying Credential status.

The implementation we would like to support in this challenge is StatusList2021.

Goal: Provide support for creating a revocable Verifiable Credential following StatusList2021.

Spec

StatusList2021

The basic idea of StatusList2021 is that the Issuer keeps a bitstring list of all Verifiable Credentials it has issued. Each credential is associated with a position in the list. The value at the position is either 0 - not revoked, or 1 - revoked.

This status list is published by the Issuer as a verifiable credential with a type of StatusList2021Credential

Functionality to Implement

Where to Start/Implementation Details

Please fork this repo and use this starter branch.

StatusList2021 functionality can be added to this revocation folder. Structure is up to the implementer.

StatusList Credential

The Status List is published by the Issuer and is a Verifiable Credential. The Issuer creates a Verifiable Credential that contains information about the Status List

The Status List details are included in credentialSubject field of Verifiable Credential

{
  "id": "https://example.com/credentials/status/3",
  "type": ["VerifiableCredential", "StatusList2021Credential"],
  "credentialSubject": {
    "id": "https://example.com/status/3#list",
    "type": "StatusList2021",
    "statusPurpose": "revocation",
    "encodedList": "H4sIAAAAAAAAA-3BMQEAAADCoPVPbQwfoAAAAAAAAAAAAAAAAAAAAIC3AYbSVKsAQAAA"
  },
...
}
  • id - (optional) the url of this Credential
  • type - should contain StatusList2021Credential
  • credentialSubject
    • type - StatusList2021
    • statusPurpose - revocation
    • encodedList - the compressed and base64 encoded value of the bit-string

StatusList2021Entry

When the Issuer issues a Verifiable Credential that is revokable, they will include an entry in the credentialStatus field. This Entry contains the information needed to check this Credential's status in the Status List credential.

"credentialStatus": {
  "id": "https://example.com/credentials/status/3#94567",
  "type": "StatusList2021Entry",
  "statusPurpose": "revocation",
  "statusListIndex": "94567",
  "statusListCredential": "https://example.com/credentials/status/3"
}
  • id - a URL identifying the status information for the verifiable credential
  • type - StatusList2021Entry
  • statusPurpose - revocation
  • statusListIndex - the bit position of the credential within the bit-string
  • statusListCredential - the URL of the StatusList2021Credential credential that encapsulates the bit-string (should match the id field of StatusList Credential)

CredentialStatus Check

Provide a function for the Verifier to use to check the credentialStatus property of a revokable Credential

Testing

The functionality added for this challenge should be unit tested. Tests can be added here in a new revocation folder.

Criteria for Completion

  • All functionality has been implemented
  • Code written has corresponding unit tests (90% coverage)
  • Code is well documented
  • Code passes CI github action (building, linting, and testing of SDK)