@cardstack/did-resolver

cardstack DID Resolver

This library is intended to resolve Cardstack Decentralized Identifiers to their associated DID Documents.

It supports the proposed Decentralized Identifiers spec from the W3C Credentials Community Group.

It requires the did-resolver library, which is the primary interface for resolving DIDs.

There is a python-equivalent version for Cardstack services in another subpackage.

DID method

Cardstack supports a family of DIDs that begin with did:cardstack:

DID Document

The DID resolver takes the DID and constructs the DID Document.

Resolving a DID document

The resolver presents a simple resolver() function that returns a ES6 Promise returning the DID document.

import { Resolver } from 'did-resolver'
import { getResolver } from '@cardstack/did-resolver'

const cardstackResolver = getResolver()

const didResolver = new Resolver({
    ...cardstackResolver
    //...you can flatten multiple resolver methods into the Resolver
})

didResolver.resolve('did:cardstack:1p123456...').then(result => console.log(result.didDocument))

// You can also use async/await syntax
(async () => {
    const result = await didResolver.resolve('did:cardstack:1p123456...');
    console.log(result.didDocument);
})();

The resolved DIDDocument will have a alsoKnownAs property that is an array containing a URL to a json document with details of the resource.

Encoding a DID

This package exports an encodeDID function that can be used to create a DID string.

import { encodeDID } from '@cardstack/did-resolver'

let did = encodeDID({ type: 'SupplierInfo' });
console.log(did); // => 'did:cardstack:1sicq4U2Dq678AtWufbxJBg7120d206cf61b50d4'

By default, encodeDID will provide the version and generate a uniqueId for you, but you can also specify them:

import { encodeDID } from '@cardstack/did-resolver'
import shortUuid from 'short-uuid';

let did = encodeDID({ type: 'SupplierInfo', version: 5, uniqueId: shortUuid.generate() });

About the cardstack method identifier format

An example of a cardstack method identifier is:

1sicq4U2Dq678AtWufbxJBg7120d206cf61b50d4
12[---------3----------][------4-------]

Let's break down the parts:

1. First character: represents the version, uses "0"-"9" for 0-9, "A-Z" for 10-35, "a-z" for 36-61

2. Second character: represents the type, 'p' for PrepaidCardCustomization, 'm' for MerchantInfo, 's' for SupplierInfo, 'r' for RewardRule

3. Next 22 characters: unique identifier, you can generate this using shortUuid.generate()

4. Last 16 characters: checksum, hash of the identifier up to this point, calculated using shake_128 with 64 bits of output