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0.2.2 • Public • Published


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A Holder ULA plugin for processing W3C Verifiable Credential QR codes, using the credential exchange flow described in vp-toolkit. This small plugin calls the endpoint as provided in the QR code and expects a ChallengeRequest object response from the endpoint. Then the ChallengeRequest object is parsed and sent to the next plugin by broadcasting a ULA message.

We strongly recommend to add the ula-vp-controller plugin so the rest of the flow is executed.


In an existing project (with package.json), install ula-process-eth-barcode

npm install ula-process-eth-barcode --save


import { ProcessEthBarcode, BrowserHttpService } from 'ula-process-eth-barcode'
import { EventHandler, UlaResponse } from 'universal-ledger-agent'
// Prepare the ProcessEthBarcode plugin
const httpService = new BrowserHttpService()
const processEthBarcode = new ProcessEthBarcode(httpService)
// Instantiate the Universal Ledger Agent with this plugin
const ulaEventHandler = new EventHandler([processEthBarcode])
// Note that you will need to add more plugins to complete the flow
// Then, somewhere in your code, call your own QR code scanner component:
const qrCodeContents: object = await yourQRCodeScanner.scan()
// Make sure that qrCodeContents object at least contains a 'type' field!
// And let the ULA handle the rest of the process:
ulaEventHandler.processMsg(qrCodeContents, (response: UlaResponse) => {
  // Handle callback

The UlaResponse callback with the statusCode and body fields can be in many shapes or forms. This plugin does not use the callback itself, instead, it passes it to the next plugin.

QR code content

In order to trigger this plugin, the ULA message must be in the following format:

const msg = {
  type: 'ethereum-qr',
  url: '{endpoint}'

The endpoint must return a signed, stringified ChallengeRequest when doing a GET request.

Handling the ChallengeRequest

This plugin does not handle the ChallengeRequest. Instead, this plugin will send a new ULA message with this payload:

const msg = {
  type: 'process-challengerequest',
  msg: challengeRequestJson

This message can be handled by the ula-vp-controller plugin. If you want to handle the ChallengeRequest yourself, create a plugin which listens to the process-challengerequest type.

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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  • dlamers
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