Working with Challenges and Responses

warning

This feature is currently in the experimental stage of development. Do not use it in production environments or presume it is secure. Expect breaking changes.

What is a challenge and response?

The VC model enables 3rd party entities to issue a Challenge requesting proof from a VC Holder. The VC Holder may respond (at the holder's discretion) with a Verifiable Presentation providing tamper-proof evidence data in response to the Challenge request.

Creating a Challenge

The challenge is created from a schema file or from an existing DID pointing to an existing schema credential. To create a challenge from a schema file, use kc create-challenge; to create a challenge from an existing credential DID, use kc create-challenge-cc instead.

$ kc create-challenge-cc social-media sm-challenge
did:mdip:test:z3v8AuaaxRxwZCPUnpCc4RoV5CZjeYVJepmJTVeJrpvyyB6LmwN

In the command above, social-media is a named alias in Alice's wallet that resolves to the DID of the social-medial credential in examples above. sm-challenge is a new named alias in Alice's wallet that contains the DID of the new challenge document:

$ kc resolve-did sm-challenge
{
    "@context": "https://w3id.org/did-resolution/v1",
    "didDocument": {
        "@context": [
            "https://www.w3.org/ns/did/v1"
        ],
        "id": "did:mdip:test:z3v8AuaaxRxwZCPUnpCc4RoV5CZjeYVJepmJTVeJrpvyyB6LmwN",
        "controller": "did:mdip:test:z3v8AuabRm9DaiakqbwFPgsLd6vSYBQtdj7poQFGYBgsZCfqTvY"
    },
    "didDocumentMetadata": {
        "created": "2024-03-22T18:18:35.413Z"
    },
    "didDocumentData": {
        "credentials": [
            {
                "schema": "did:mdip:test:z3v8AuaeAPf9JMuyYZ1D79D626uUzDQmRPwq4d8oB1Th6ztzAS7"
            }
        ]
    },
    "mdip": {
        "registry": "hyperswarm",
        "type": "asset",
        "version": 1
    }
}

Creating a Verifiable Presentation Response

When presented with a challenge, a user can prepare a Verifiable Presentation of the credentials claims requested in the challenge.

1. The user can first verify that they are using the identity they want to create a Verifiable Presentation for:

   $ kc use-id Bob
   OK

2. Next, the user can optionally create their own alias to interact with the challenge DID:

   $ kc add-name sm-challenge did:mdip:test:z3v8AuaaxRxwZCPUnpCc4RoV5CZjeYVJepmJTVeJrpvyyB6LmwN
   note

   If you're testing as both Alice and Bob from a single wallet, you can skip this step.

3. Then the user can create a repsonse:

   $ kc create-response sm-challenge
   did:mdip:test:z3v8AuadZ56m4x2UTpeY3HhSFvFQnrCUyASBYA77vqrqQr9SR99

The command above mapped the Challenge with previously received VCs and found one matching the request for Bob's twitter account credential. The resulting DID document contains a Verifiable Presentation revealing the twitter account VC data encrypted to the requesting party (Alice).

Verifying a VP Response

To verify the response received to a challenge, a user passes the DID of the VP received from the VC Holder being challenged, as well as the challenge DID:

$ kc use-id Alice
OK
kc verify-response did:mdip:test:z3v8AuadZ56m4x2UTpeY3HhSFvFQnrCUyASBYA77vqrqQr9SR99 did:mdip:test:z3v8AuaaxRxwZCPUnpCc4RoV5CZjeYVJepmJTVeJrpvyyB6LmwN
[
    {
        "@context": [
            "https://www.w3.org/ns/credentials/v2",
            "https://www.w3.org/ns/credentials/examples/v2"
        ],
        "type": [
            "VerifiableCredential",
            "did:mdip:test:z3v8AuaeAPf9JMuyYZ1D79D626uUzDQmRPwq4d8oB1Th6ztzAS7"
        ],
        "issuer": "did:mdip:test:z3v8AuabRm9DaiakqbwFPgsLd6vSYBQtdj7poQFGYBgsZCfqTvY",
        "validFrom": "2024-03-22T15:06:24.773Z",
        "validUntil": null,
        "credentialSubject": {
            "id": "did:mdip:test:z3v8AuairhLoGZqf6UDKw7zXyBknTvanvSzFHnLpwy8nwa7WLzk"
        },
        "credential": {
            "account": "https://twitter.com/bob",
            "service": "twitter.com"
        },
        "signature": {
            "signer": "did:mdip:test:z3v8AuabRm9DaiakqbwFPgsLd6vSYBQtdj7poQFGYBgsZCfqTvY",
            "signed": "2024-03-22T18:00:19.405Z",
            "hash": "62f7cb1a31d338d29287f9ce91b4da103391dca88b853ea1b05920c6049ae8ff",
            "value": "37941a42492a431ceaff91c86de55eb0cd3ed98107a3ce19a76d88511b7fe2bc6fcf298c69e431b048ab0786e9624b647e4d03a4c26031c4c6e2b6882223defe"
        }
    }
]