# Veramo Credential Interface Specification 2.0

# Credential Interface Design Update

## Notes / Main Points:
- a persistence function should not be part of the interface: remove "save"
- If clients want to persist a VC/VP they will have to call the appropriate separate save interface function
- Accumulate all non-credential Payload properties into an `options` object.
- Input is always a valid JSON-LD (and validate against @context) (even with proofType: "JWT")
- Verification of JWT and JSON-LD Payload cannot separeted from Credentials Validation e.g. verify and validate a credential is an atomic operation
- MessageHandler would need to be updated to identify payload (by metadata?) in order to call the appropriate action handlers
- We introduce dedicated verify methods for Credentials that did not exist before.
- We "keep" a dedicated function that validates(!) a verifiable presentation against a previous request.
- CredentialStatus Endpoints (to revoke) are currently out-of-scope.

## CreateVerifiablePresentation (Holder)

{
    "presentation": {...},
    "options": {
        "verificationMethod": "direct type" OR "DID Anchor",
        "proofType": "LDProof" or "JWT",
        "proofPurpose": "string", Default 'assertionMethod',
        "domain": "example.com",
        "challenge": "d436f0c8-fbd9-4e48-bbb2-55fc5d0920a8"
    }
}

Example DID Anchor: `id:example:123#z6MksHh7qHWvybLg5QTPPdG2DgEjjduBDArV9EF9mRiRzMBN`
Example Verification Method:
`Ed25519VerificationKey2018` -> Results in `Ed25519Signature2018`

## CreateVerifiableCredential (Issuer)

{
  "credential": {
  ...
      "credentialStatus": {...}
  ...
  },
  "options": {
      "verificationMethod":
      "proofType": "LDProof" or "JWT",
      "proofPurpose": "string", Default 'assertionMethod'.
  }
}

credentialStatus `payload` is automatically witin the `credential` payload. It's the responsibility of th

## VerifyVerifiablePresentation

{
    "presentation": JWT or {...},
    "options": {
        "verificationMethod": "direct type" OR "DID Anchor",
        "proofType": "LDProof" or "JWT",
        "proofPurpose": "assertionMethod",
        "domain": "example.com",
        "challenge": "d436f0c8-fbd9-4e48-bbb2-55fc5d0920a8"
    }
}

This methods can delegate VC validation of contained VC to `VerifyVerifiableCredential`
JWT/JSON-LD Discovery/Format should be outside of this function. Fails on `proofType` mismatch.
Fails on `proofPurpose` mismatch.

## VerifyVerifiableCredential

{
  "credential": {...},
  "options": {
      "verificationMethod":
      "proofType": "LDProof" or "JWT",
      "proofPurpose": "string", Default 'assertionMethod'.
      "failOnCredentialStatus: "true/false"
  }
}

JWT/JSON-LD Discovery/Format should be outside of this function. Fails on `proofType` mismatch.
Fails on `proofPurpose` mismatch.

## ValidatePresentationAgainstRequest
This is the end-2-end validation of a presentation against a previous request. Currently: Veramos SDR, but also Presentation Definition int he future.

{
  "presentation": {...},
  "request": {}
  "options": {
      "proofType": "LDProof" or "JWT",
      "request_format: "VeramoSDR" or "DIF_PE"
  }
}

Note, "challenge/domain" can be inside the supported request format and revalidated within

## Credential Status Methods (Out of Scope / TBD)
### Update Credential Status

{
    "credentialId": "urn:uuid:45a44711-e457-4fa8-9b89-69fe0287c86a",
    "credentialStatus": [
        {
            "type": "RevocationList2020Status",
            "status": "0"
        }
    ]
}

### Check Credential Status?
- Should not be exposed and only abstracted behind `VerifyVerifiableCredential`

# Appendix

## Current Interface

### CreateVerifiablePresentation

{
  "presentation": {
    "id": "string",
    "holder": "string",
    "issuanceDate": "string",
    "expirationDate": "string",
    "@context": [
      "string"
    ],
    "type": [
      "string"
    ],
    "verifier": [
      "string"
    ],
    "verifiableCredential": [
      {
        "@context": [
          "string"
        ],
        "id": "string",
        "type": [
          "string"
        ],
        "issuer": {
          "id": "string"
        },
        "issuanceDate": "string",
        "expirationDate": "string",
        "credentialSubject": {
          "id": "string"
        },
        "credentialStatus": {
          "id": "string",
          "type": "string"
        },
        "proof": {
          "type": "string"
        }
      }
    ]
  },
  "save": true,
  "proofFormat": "string"
}

### CreateVerifiableCredential

{
  "credential": {
    "@context": [
      "string"
    ],
    "id": "string",
    "type": [
      "string"
    ],
    "issuer": {
      "id": "string"
    },
    "issuanceDate": "string",
    "expirationDate": "string",
    "credentialSubject": {
      "id": "string",
      "additionalProp1": {}
    },
    "credentialStatus": {
      "id": "string",
      "type": "string"
    }
  },
  "save": true,
  "proofFormat": "string"
}