Issuing Credentials

What We Are Doing:

• Setting up a minimal Express application in src/index.js that:

  • Loads environment variables (via dotenv).

  • Serves static files from a public/ directory.

  • Mounts our router (where the /kyc-credential route will live).

Why: Before we can implement any credential-related endpoints, we need a working Express server that can:

• Host our frontend assets (HTML/CSS/JS) under public/.

• Accept POST requests (JSON/form data) from the frontend.

• Delegate route handling to src/issuer-routes.js.

• Spin up on a known port so the frontend and wallet callbacks work correctly.

Steps: Create src/index.js with the following contents:

import express from "express";
import path from "path";
import {fileURLToPath} from "url";
import dotenv from "dotenv";
import issuerRouter from "./issuer-routes.js";
import jwt from "jsonwebtoken";

dotenv.config();

// Convert module URL to a __dirname-like value
const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

// PORT and BASE_URL come from .env (fallback to 3000 if not set)
const PORT = process.env.PORT || 3000;
const BASE_URL = process.env.BASE_URL || `http://localhost:${PORT}`;

// Initialize Express app
const app = express();

// Serve any static assets (e.g., index.html, scripts, styles) from public/
app.use(express.static(path.join(__dirname, "../public")));

// Parse URL-encoded bodies (HTML form submissions)
app.use(express.urlencoded({extended: true}));

// Attach our router (defined in src/issuer-routes.js)
app.use("/issuer", express.json(), issuerRouter);

// Start the server
app.listen(PORT, () => {
  console.log(`Server is running on ${BASE_URL}`);
});

To .env file, add the following variables:

PORT=3000

BASE_URL=http://192.168.1.1:3000 # or your desired base URL it should match the URL of your server + the port. 
# It cannot be localhost because the Empe DID Wallet needs to access it from a mobile device

JWT_SECRET=`your-jwt-secret` # a secret key for signing JWTs, used later for authorization

Also make sure you have ISSUER_URL and ISSUER_SECRET set in your .env file as described in the Deploying the Issuer.

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Issuing Credentials

What We Are Doing:

• Implementing a route (/kyc-credential) in our Express app that:

  • Takes user input (age, firstName, lastName).

  • Contacts the Issuer to create a credential issuance offering.

  • Returns the offering data, including a qr_code_url.

Why: This route enables users to input their info and receive a QR code. Scanning the QR code with the Empe DID Wallet allows them to claim the credential.

Steps: Update src/issuer-routes.js:

import {Router} from "express";
import fetch from "node-fetch";
import dotenv from "dotenv";

dotenv.config();

const router = Router();
const ISSUER_URL = process.env.ISSUER_URL;
const ISSUER_SECRET = process.env.ISSUER_SECRET;

router.post("/kyc-credential", async (req, res) => {
  try {
    const {age, firstName, lastName} = req.body;
    // Fetch issuer metadata to get offering_endpoint
    const metadataRes = await fetch(`${ISSUER_URL}/.well-known/openid-credential-issuer`);
    const metadata = await metadataRes.json();
    const offering_endpoint = metadata.offering_endpoint;
    // Request an issuance offering from the Issuer
    const offeringRes = await fetch(offering_endpoint, {
      method: "POST",
      headers: {
        "Content-Type": "application/json",
        "x-client-secret": ISSUER_SECRET,
      },
      body: JSON.stringify({
        credential_type: "KYC Verifiable Credential",
        credential_subject: {age: Number(age), firstName, lastName},
      }),
    });

    const offeringData = await offeringRes.json();
    res.status(200).json(offeringData);
  } catch (error) {
    console.error(error);
    res.status(500).json({error: "Internal server error"});
  }
});

export default router;

Run the server:

  node src/index.js

Next, we will create a simple frontend form to submit user data and display the QR code.