@blockcerts/cert-verifier-js

A library to parse and verify Blockcerts certificates.

Usage

Install

$ npm i @blockcerts/cert-verifier-js

Import

Commonjs

Exposed by default:

const { Certificate } = require('@blockcerts/cert-verifier-js');
var certificate = new Certificate(certificateDefinition);

Running in Nodejs

const { Certificate } = require('@blockcerts/cert-verifier-js/lib');
var certificate = new Certificate(certificateDefinition);

ES module

import { Certificate } from '@blockcerts/cert-verifier-js';
let certificate = new Certificate(certificateDefinition);

Script tag (iife)

Check an example here

<script src='node_modules/@blockcerts/cert-verifier-js/dist/verifier-iife.js'></script>
<script>
  var certificate = new Verifier.Certificate(certificateDefinition);
</script>

Examples

You can find more examples in the test folder.

Parse a Blockcert certificate

var fs = require('fs');

fs.readFile('./certificate.json', 'utf8', function (err, data) {
  if (err) {
    console.log(err);
  }

  let certificate = new Certificate(data);
  console.log(cert.name);
});

Verify a Blockcert certificate

var fs = require('fs');

fs.readFile('./certificate.json', 'utf8', function (err, data) {
  if (err) {
    console.log(err);
  }

  let certificate = new Certificate(data);
  const verificationResult = await certificate.verify(({code, label, status, errorMessage}) => {
    console.log('Code:', code, label, ' - Status:', status);
    if (errorMessage) {
      console.log(`The step ${code} fails with the error: ${errorMessage}`);
    }
  });

  if (verificationResult.status === 'failure') {
    console.log(`The certificate is not valid. Error: ${verificationResult.errorMessage}`);
  }
});

API

Certificate

new Certificate(certificateDefinition, options)

const certificate = new Certificate(certificateDefinition);

The constructor automatically parses a certificate.

Parameter

• certificateDefinition (String|Object): the certificate definition. Can either be a string or a JSON object.
• options: (Object): an object of options. The following properties are used:
  • locale: (String): language code used to set the language used by the verifier. Default: en-US.

Returns

The certificate instance has the following properties:

• certificateImage: String. Raw data of the certificate image
• certificateJson: Object. Certificate JSON object
• chain: Object. Chain the certificate was issued on
• description: String. Description of the certificate
• expires: String|null. Expiration date
• id: String. Certificate's ID
• isFormatValid: Boolean. Indicates whether or not the certificate has a valid format
• issuedOn: String. Datetime of issuance (ISO-8601)
• issuer: Object. Certificate issuer
• locale: String. Language code used by the verifier
• metadataJson: Object|null . Certificate metadata object
• name: String. Name of the certificate
• publicKey: String. Certificate's public key
• receipt: Object. Certificate's receipt
• recipientFullName: String. Full name of recipient
• recordLink: String. Link to the certificate record
• revocationKey: String|null. Revocation key (if any)
• sealImage: String. Raw data of the seal's image;
• signature: String|null. Certificate's signature
• signatureImage: SignatureImage[]. Array of certificate signature lines.
• subtitle: String|null. Subtitle of the certificate
• transactionId: String. Transaction ID
• rawTransactionLink: String. Raw transaction ID
• transactionLink: String. Transaction link
• verificationSteps: VerificationStep[]. The array of steps the certificate will have to go through during verification
• version: CertificateVersion. Version of the certificate

Note: verificationSteps is generated according to the nature of the certificate. The full steps array is provided ahead of verification in order to give more flexibility to the consumer. For example, you might want to pre-render the verification steps for animation, or render a count of steps and/or sub-steps.

VerificationStep has the following shape:

{
    code: 'formatValidation',
    label: 'Format validation',
    labelPending: 'Validating format',
    subSteps: [
      {
        code: 'getTransactionId',
        label: 'Get transaction ID',
        labelPending: 'Getting transaction ID',
        parentStep: 'formatValidation'
      },
      ...
    ]
}

verify(stepCallback)

This will run the verification of a certificate. The function is asynchronous.

const certificateVerification = await certificate.verify(({code, label, status, errorMessage}) => {
    console.log('Sub step update:', code, label, status);
}));
console.log(`Verification was a ${certificateVerification.status}:`, certificateVerification.message);

Parameters

• ({code, label, status, errorMessage}) => {} (Function): callback function called whenever a substep status has changed. The callback parameter has 4 properties:
  • code: substep code
  • label: readable label of the substep
  • status: substep status (success, failure, starting)
  • errorMessage: error message (optional)

Returns

The final verification status:

{ code, status, message }

• code: code of the final step (final)
• status: final verification status (success, failure)
• message string | Object: status message. It is internationalized and in case of failure it returns the error message of the failed step. When an object, it takes the following shape:
  • label: Main label of the final step
  • description: further details about the issuance
  • linkText: translation provided for a link text towards the transaction

Shape of the returned object can be checked here: https://github.com/blockchain-certificates/cert-verifier-js/blob/master/src/data/i18n.json#L41

Constants

Several constants are being exposed:

import { BLOCKCHAINS, STEPS, SUB_STEPS, CERTIFICATE_VERSIONS, VERIFICATION_STATUSES } from '@blockcerts/cert-verifier-js';

• BLOCKCHAINS: descriptive object of all blockchains supported by the library
• STEPS: descriptive object of all verification steps (top level)
• SUB_STEPS: descriptive object of all verification substeps
• CERTIFICATE_VERSIONS: list of all certificate versions
• VERIFICATION_STATUSES

i18n

The exposed function getSupportedLanguages() returns an array of language codes supported by the library.

import { getSupportedLanguages } from '@blockcerts/cert-verifier-js';
getSupportedLanguages(); // ['en-US', 'es-ES', 'mt', ...]

You can use the codes for the locale option.

Please note that while we are working to add new languages, any new translation is welcome through forking & PR.

Contribute

Run the tests

$ npm run test

Build

$ npm run build

The build files are in the dist folder.

Verification process

If you want more details about the verification process, please check out the documentation.

Contact

Contact us at the Blockcerts community forum.