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This Holder ULA plugin responds to an incoming ChallengeRequest from the issuer and/or verifier. This implementation uses secp256k1 by default. If you want to use a different cryptographic algorithm, then provide your own crypt-util instance.


If you work with QR codes, please read the instructions in the ula-process-eth-barcode repository. Also, in order to save credentials properly, we advise to install the ula-vc-data-management plugin as well.

In an existing project (with package.json), install the plugin by running the following commands:

npm install universal-ledger-agent --save
npm install crypt-util --save
npm install vp-toolkit --save
npm install ula-vp-controller-plugin --save


This is an example of enabling this plugin in the ULA in a browser environment.

import { BrowserHttpService, EventHandler } from "universal-ledger-agent";
import { VpController } from "ula-vp-controller";
import { LocalCryptUtils } from "crypt-util";
import {
} from "vp-toolkit";
// Prepare plugin dependencies
const browserHttpService = new BrowserHttpService()
const cryptUtil = new LocalCryptUtils()
const vcSigner = new VerifiableCredentialSigner(cryptUtil)
const vcGenerator = new VerifiableCredentialGenerator(vcSigner)
const vpSigner = new VerifiablePresentationSigner(cryptUtil)
const vpGenerator = new VerifiablePresentationGenerator(vpSigner)
// Instantiate the plugin
const vpControllerPlugin = new VpController(cryptUtil, vcGenerator, vpGenerator, browserHttpService)
// Setup the ULA and inject the plugin
const ulaEventHandler = new EventHandler([vpControllerPlugin /*, other ULA plugins here */])


Using an existing ULA plugin

Add the ula-process-eth-barcode plugin to receive input from that plugin and you're set to go!


However, if you want to invoke this plugin manually, send a ULA message with this format:

const msg = {
  type: 'process-challengerequest',
  msg: { /* IChallengeRequestParamsfields */
    toVerify: [{predicate: "{schema.org URL}", allowedIssuers: ["did:eth:allowedIssuer"]}, {predicate: "{schema.org URL}"}],
    toAttest: [{predicate: "{schema.org URL}"}, {predicate: "{schema.org URL}"}],
    postEndpoint: '{endpoint URL}', // The holder will post a VerifiablePresentation object here
    proof: { /* Proof object */ },
    nonce: "{uuid}"
ulaEventHandler.processMsg(msg, (response: UlaResponse) => {
  // Handle callback
  // If statuscode is 1, update the UI

The msg property contains a ChallengeRequest object. Generate a ChallengeRequest object by using the vp-toolkit library.

Note: toVerify and toAttest fields are optional. You can use both at the same time or omit one of them. If you omit both fields, the plugin will complete without sending any visual feedback.


When the plugin has finished, the callback function will be called twice. The first time for updating the user interface and the second time for passing operation details (in this case, only a status code).

In case of a successful situation:

// Dont show loading screen, show success screen
callback(new UlaResponse({ statusCode: 1, body: { loading: false, success: true, failure: false } }))
callback(new UlaResponse({ statusCode: 201, body: {} })) // Everything went OK

In case of an error:

// Don't show loading screen, but show failure screen
callback(new UlaResponse({ statusCode: 1, body: { loading: false, success: false, failure: true } }))
callback(new UlaResponse({ statusCode: 204, body: {} })) // No information available

Running tests

Besides unit testing with Mocha, the effectivity of all tests are also measured with the Stryker mutation testing framework.

npm run test
npm run stryker

We aim to achieve a coverage of 100%. Stryker and/or mocha test scores below 80% will fail the build.


Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

Please make sure to update tests as appropriate.

License and disclaimer

apache-2.0 with a notice.

We discourage the use of this work in production environments as it is in active development and not mature enough.

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