Credentials

The Credentials package enables the creation, signing, verification, and general processing of Verifiable Credentials (VCs). It also has full Presentation Exchange support.

Verifiable Credential

Features

• Create Verifiable Credentials with flexible data types.
• Sign credentials using decentralized identifiers (DIDs).
• Verify the integrity and authenticity of VCs encoded as JSON Web Tokens (JWTs).
• Parse JWT representations of VCs into VerifiableCredential instances.

Usage:

Creating a Verifiable Credential

Create a new VerifiableCredential with the following parameters:

• type: Type of the credential.
• issuer: Issuer URI.
• subject: Subject URI.
• data: Credential data.
• expirationDate?: (optinal) Expiration Date

class StreetCredibility {
  constructor(localRespect, legit) {
    this.localRespect = localRespect;
    this.legit = legit;
  }
}

const vc = new VerifiableCredential({
  type: "StreetCred",
  issuer: "did:example:issuer",
  subject: "did:example:subject",
  data: new StreetCredibility("high", true)
});

Signing a Verifiable Credential

Sign a VerifiableCredential with a DID:

• signOptions: The sign options used to sign the credential.

First create a SignOptions object as follows:

import { Ed25519, Jose } from '@web5/crypto';
import { DidKeyMethod } from '@web5/dids';

const issuer = await DidKeyMethod.create();
const privateKey = (await Jose.jwkToKey({ key: issuer.keySet.verificationMethodKeys![0].privateKeyJwk! })).keyMaterial;

const signOptions = {
  issuerDid: issuer.did,
  subjectDid: "did:example:subject",
  kid: `${issuer.did}#${issuer.did.split(':')[2]}`,
  signer: async (data) => await Ed25519.sign({ data, key: privateKey })
};

Then sign the VC using the signoptions object

const vcJwt = vc.sign(signOptions)

Verifying a Verifiable Credential

Verify the integrity and authenticity of a VC JWT

• vcJwt: The VC in JWT format as a String.

try {
  await VerifiableCredential.verify(vcJwt)
  console.log("VC Verification successful!")
} catch (e: Error) {
  console.log("VC Verification failed: ${e.message}")
}

Parsing a JWT into a Verifiable Credential

Parse a JWT into a VerifiableCredential instance

vcJwt: The VC JWT as a String.

const vc = VerifiableCredential.parseJwt(vcJwt)

Presentation Exchange

PresentationExchange is designed to facilitate the creation of a Verifiable Presentation by providing tools to select and validate Verifiable Credentials against defined criteria.

Features

• Select credentials that satisfy a given presentation definition.
• Validate if a Verifiable Credential JWT satisfies a Presentation Definition.
• Validate input descriptors within Verifiable Credentials.

Usage

Selecting Credentials

Select Verifiable Credentials that meet the criteria of a given presentation definition.

• vcJwts: The list of Verifiable Credentials to select from.
• presentationDefinition The Presentation Definition to match against.

This returns a list of the vcJwts that are acceptable in the presentation definition.

const selectedCredentials = PresentationExchange.selectCredentials(
    vcJwts,
    presentationDefinition
)

Satisfying a Presentation Definition

Validate if a Verifiable Credential JWT satisfies the given presentation definition. Will return an error if the evaluation results in warnings or errors.

• vcJwts: The list of Verifiable Credentials to select from.
• presentationDefinition The Presentation Definition to match against.

try {
  PresentationExchange.satisfiesPresentationDefinition(vcJwts, presentationDefinition)
  console.log("vcJwts satisfies Presentation Definition!")
} catch (e: Error) {
  console.log("Verification failed: ${e.message}")
}

Create Presentation From Credentials

Creates a presentation from a list of Verifiable Credentials that satisfy a given presentation definition. This function initializes the Presentation Exchange (PEX) process, validates the presentation definition, evaluates the credentials against the definition, and finally constructs the presentation result if the evaluation is successful.

• vcJwts: The list of Verifiable Credentials to select from.
• presentationDefinition The Presentation Definition to match against.

const presentationResult = PresentationExchange.createPresentationFromCredentials(vcJwts, presentationDefinition)

Validate Definition

This method validates whether an object is usable as a presentation definition or not.

const valid = PresentationExchange.validateDefinition(presentationDefinition)

Validate Submission

This method validates whether an object is usable as a presentation submission or not.

const valid = PresentationExchange.validateSubmission(presentationSubmission)

Validate Presentation

Evaluates a presentation against a presentation definition.

const evaluationResults = PresentationExchange.evaluatePresentation(presentationDefinition, presentation)