@web5/credentials

The @web5/credentials package provides the following functionality:

• creation, signing, verification, and general processing of Verifiable Credentials (VCs).
• Presentation Exchange evaluation

Table of Contents

• VerifiableCredential
  • Features
  • Usage
    • Creating a Verifiable Credential
    • Signing a Verifiable Credential
    • Verifying a Verifiable Credential
    • Parsing a JWT into a Verifiable Credential
• VerifiablePresentation
  • Features
  • Usage
    • Creating a Verifiable Presentation
    • Signing a Verifiable Presentation
    • Verifying a Verifiable Presentation
    • Parsing a JWT into a Verifiable Presentation
• PresentationExchange
  • Features
  • Usage
    • Selecting Credentials
    • Satisfying a Presentation Definition
    • Create Presentation From Credentials
    • Validate Definition
    • Validate Submission
    • Validate Presentation

VerifiableCredential

VC 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.

VC Usage

Along with the credentials package you will need command and dids for most of the Verifiable Credentials operations

npm install @web5/common
npm install @web5/dids
npm install @web5/credentials

Then to import:

import { VerifiableCredential, VerifiablePresentation, PresentationExchange } from '@web5/credentials';

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.
• issuanceDate? (Optional) The Issuance Date. Defaults to current date if not specified
• expirationDate?: (Optional) Expiration Date
• evidence?: (Optional) Evidence can be included by an issuer to provide the verifier with additional supporting information in a verifiable credential.

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

const vc = await VerifiableCredential.create({
  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:

• did: The did that is signing the VC

First create a Did object as follows:

import { DidKey } from '@web5/dids';
const issuer: BearerDid = await DidKey.create();

Then sign the VC using the did object

const vcJwt = await vc.sign({ did: issuer });

Verifying a Verifiable Credential

Verify the integrity and authenticity of a Verifiable Credential

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

try {
  await VerifiableCredential.verify({ vcJwt: signedVcJwt })
  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: signedVcJwt })

VerifiablePresentation

VP Features

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

VP Usage

Creating a Verifiable Presentation

Create a new VerifiablePresentation with the following parameters:

• holder: The holder URI of the presentation, as a string..
• vcJwts: The JWTs of the credentials to be included in the presentation.
• type: Optional type of the presentation, can be a string or an array of strings.
• additionalData: Optional additional data to be included in the presentation.

const vp = await VerifiablePresentation.create({
  type: 'PresentationSubmission',
  holder: 'did:ex:holder',
  vcJwts: vcJwts,
  additionalData: { 'arbitrary': 'data' }
});

Signing a Verifiable Presentation

Sign a VerifiablePresentation with a DID:

• did: The did that is signing the VP

Sign the VP using the did object

const vpJwt = await vp.sign({ did: issuer });

Verifying a Verifiable Presentation

Verify the integrity and authenticity of a Verifiable Presentation

• vpJwt: The VP in JWT format as a String.

try {
  await VerifiablePresentation.verify({ vpJwt: signedVpJwt })
  console.log("VP Verification successful!")
} catch (e: Error) {
  console.log("VP Verification failed: ${e.message}")
}

Parsing a JWT into a Verifiable Presentation

Parse a JWT into a VerifiablePresentation instance

vpJwt: The VP JWT as a String.

const parsedVp = VerifiablePresentation.parseJwt({ vcJwt: signedVcJwt })

PresentationExchange

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

PEX Features

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

PEX 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: signedVcJwts,
    presentationDefinition: 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: signedVcJwts, presentationDefinition: 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: signedVcJwts, presentationDefinition: presentationDefinition })

Validate Definition

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

• presentationDefinition The Presentation Definition to validate

const valid = PresentationExchange.validateDefinition({ presentationDefinition })

Validate Submission

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

• presentationSubmission The Presentation Submission to validate

const valid = PresentationExchange.validateSubmission({ presentationSubmission })

Validate Presentation

Evaluates a presentation against a presentation definition.

• presentationDefinition The Presentation Definition to validate
• presentation The Presentation

const evaluationResults = PresentationExchange.evaluatePresentation({ presentationDefinition, presentation })