Create Status List

Create a Bitstring Status List on cheqd, stored as a DID-Linked Resource (DLR), using Veramo.

The Bitstring Status List Specification indicates that it may be desirable to store the actual StatusList using something like a Content Distribution Network to lessen the load on the server maintained by the issuer to return a result in real-time.

Using cheqd's Resource Module, the same benefits may be achieved. In fact, storing a StatusList as an on-ledger Resource is a much better application of technology than using a Verifiable Credential for the same purpose.

By storing a StatusList on the cheqd Network as a Resource, it creates a much more resilient and decentralised mechanism for storing and maintaining the revocation/suspension status of Verifiable Credentials. The benefits of using the cheqd Resource module over traditional centralised architecture are detailed here.

Moreover, cheqd's Resource Module enables individual Resources to be referenced and retrieved using a DID URL in conformance with DID Core. This is being standardized at the Trust over IP Foundation within a specification called DID URLs for Digital Resources.

Creating a StatusList Resource using Veramo SDK for cheqd

Using the cheqd Resource module, the same content and semantics of Bistring Status List can be replicated, with additional benefits of enabling DID Resolvers to fetch the contents of the StatusList.

Create a DID and DID Document with keys to manage the StatusList

You can follow the tutorial to create a DID and DID Document here.

Let's assume that the following DID is created.

"didDocument": {
    "@context": [
      "https://www.w3.org/ns/did/v1"
    ],
    "id": "did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY",
    "controller": [
      "did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY"
    ],
    "verificationMethod": [
      {
        "id": "did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY#verkey-1",
        "type": "Ed25519VerificationKey2020",
        "controller": "did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY",
        "publicKeyMultibase": "zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpYAZPD1M9tvwyzE"
      },
    ],
    "authentication": [
      "did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY#verkey-1"
    ]
  }

Prepare encodedList content

Prepare a file with the Bistring Status List bitstring encodedList and encode it into base64, following the same generate algorithm as in the Specification.

Note: The uncompressed bitstring MUST be at least 16KB in size to maintain herd privacy for the holder.

Create a unique ID for the StatusList Resource

UUIDs are used to identify Resources. On Unix systems, the uuidgen tool can be used to generate a new UUID.

Create a new Resource for an unencrypted StatusList

{
  "kms": "local",
  "payload": {
    "collectionId": "zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY",
    "id": "4a71319b-00b1-4db9-bc05-56dc426f7062",
    "name": "ExampleStatusList",
    "resourceType": "StatusListRevocation",
    "encrypted": false
    "data": "SGVsbG8sIHdvcmxk"
  },
  "signInputs": [
    {
      "verificationMethodId": "did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY#verkey-1",
      "keyType": "Ed25519",
      "privateKeyHex": "0f5c124886178037952e87e0cdc55d185732577fca19ae877e64ac9ab24a0cc534e5326e70f1a42d785d93048aee806c359ec75a7b06f39253befd1746708438"
    }
  ]
}

Where the fields within the payload have the following meaning:

Parameter	Description
collectionId	The unique identifier of the parent DID, to link the Resource to a particular DID
id	A UUID for the resource, to enable it to be specifically referenced and fetched
name	This must be a unique name indicating the type of Status List, but also a qualifying name for the List. For example: ExampleStatusList
resourceType	This must indicate the statusPurpose. This value should be either: StatusList2021Revocation or StatusList2021Suspension
data	Base 64 encoded file containing the full bitstring for the StatusList

Note: If an issuer wants to create multiple StatusLists within the same Collection, they must have unique and distinct names.

Note association between DID and Resource

Once created, the StatusList2021 Resource will be associated with the parent DID, and referenced in the DID Document Metadata as follows:

{
  "didDocument": {
    "@context": ["https://www.w3.org/ns/did/v1"],
    "id": "did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY",
    "controller": ["did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY"],
    "verificationMethod": [
      {
        "id": "did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY#verkey-1",
        "type": "Ed25519VerificationKey2020",
        "controller": "did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY",
        "publicKeyMultibase": "zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpYAZPD1M9tvwyzE"
      }
    ],
    "authentication": [
      "did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY#verkey-1"
    ]
  },
  "didDocumentMetadata": {
    "created": "2022-09-16T11:15:20Z",
    "versionId": "204e296f-d55b-4552-9fec-0b242a689f96",
    "linkedResourceMetadata": [
      {
        "resourceURI": "did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY/resources/4a71319b-00b1-4db9-bc05-56dc426f7062",
        "resourceCollectionId": "zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY",
        "resourceId": "4a71319b-00b1-4db9-bc05-56dc426f7062",
        "resourceName": "ExampleStatusList2021",
        "resourceType": "StatusList2021Revocation",
        "mediaType": "application/json",
        "created": "2022-09-16T11:15:52Z",
        "checksum": "0f503dfbff29de9ac74fd07f1720ba560eb388e28062367884890c311736ec9d",
        "previousVersionId": "",
        "nextVersionId": ""
      }
    ]
  }
}

Creating new StatusList2021 Resource Version

An issuer may want to regularly update the bitstring whenever there is a certain amount of revocation status updates. The issuer will therefore need to create a new version for the initial StatusList2021 Resource.

Resources with the same Collection ID and name are grouped into version sets. Each resource in such a set has a link to the previous version (except the first version) and the next version (if it's not the most recent version).

To create a resource and mark it as a new version within a particular group, it is necessary to use the same collection-id, name and type as in the previous version. Links between versions will be created automatically.

New versions have dedicated unique IDs and can be referenced and retrieved as any other resources.

For example:

{
  "kms": "local",
  "payload": {
    "collectionId": "zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY", // Same Collection ID
    "id": "6922ae19-777e-4e05-8b10-8a2f0a2d418d", // New unique ID
    "name": "ExampleStatusList2021", // Same name
    "resourceType": "StatusList2021Revocation", // Same Resource Type
    "data": "hwbWB8FnRwXxmxk" // New base 64 encoded value with updated bitstring
  },
  "signInputs": [
    {
      "verificationMethodId": "did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY#verkey-1", // Same Verification key
      "keyType": "Ed25519",
      "privateKeyHex": "0f5c124886178037952e87e0cdc55d185732577fca19ae877e64ac9ab24a0cc534e5326e70f1a42d785d93048aee806c359ec75a7b06f39253befd1746708438"
    }
  ]
}

Resulting in the following metadata syntax:

{
  "didDocument": {
    "@context": ["https://www.w3.org/ns/did/v1"],
    "id": "did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY",
    "controller": ["did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY"],
    "verificationMethod": [
      {
        "id": "did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY#verkey-1",
        "type": "Ed25519VerificationKey2020",
        "controller": "did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY",
        "publicKeyMultibase": "zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpYAZPD1M9tvwyzE"
      }
    ],
    "authentication": [
      "did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY#verkey-1"
    ]
  },
  "didDocumentMetadata": {
    "created": "2022-09-16T11:15:20Z",
    "versionId": "204e296f-d55b-4552-9fec-0b242a689f96",
    "linkedResourceMetadata": [
      {
        "resourceURI": "did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY/resources/4a71319b-00b1-4db9-bc05-56dc426f7062",
        "resourceCollectionId": "zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY",
        "resourceId": "4a71319b-00b1-4db9-bc05-56dc426f7062",
        "resourceName": "ExampleStatusList2021",
        "resourceType": "StatusList2021Revocation",
        "mediaType": "application/json",
        "created": "2022-09-16T11:15:52Z",
        "checksum": "0f503dfbff29de9ac74fd07f1720ba560eb388e28062367884890c311736ec9d",
        "previousVersionId": "",
        "nextVersionId": "6922ae19-777e-4e05-8b10-8a2f0a2d418d"
      },
      {
        "resourceURI": "did:cheqd:testnet:zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY/resources/6922ae19-777e-4e05-8b10-8a2f0a2d418d",
        "resourceCollectionId": "zGgLTsq96mTsFcFBUCxX6k4kc5i5RNpY",
        "resourceId": "6922ae19-777e-4e05-8b10-8a2f0a2d418d",
        "resourceName": "ExampleStatusList2021",
        "resourceType": "StatusList2021Revocation",
        "mediaType": "application/json",
        "created": "2022-10-16T09:04:17Z",
        "checksum": "0f503dfbff29de9ac74fd07f1720ba560eb388e28062367884890c311736ec9d",
        "previousVersionId": "4a71319b-00b1-4db9-bc05-56dc426f7062",
        "nextVersionId": ""
      }
    ]
  }
}