Transaction Confirmation

This section covers backend integration related to transaction confirmation.

How to Verify a Transaction Confirmation Result

1. Verify the LoginID token.
2. Compare the nonce values (if passed in as an option).
3. Verify that the transaction hash (txHash) matches the original payload.

info

For verifying the LoginID token itself, click here.

To calculate the hash, follow this formula:

tx_hash = base64url(sha256(txPayload + nonce + lNonce));

Where the txPayload value is the txPayload sent in to LoginID.

Below is a NodeJS backend example demonstrating how to verify the transaction result.

NodeJS

import { calculateTxHash } from "@/server/crypto";
import { checkAuthenticated } from "@/server/middleware/";
import jwt from "jsonwebtoken";

const LOGINID_BASE_URL = process.env.LOGINID_BASE_URL;
const LOGINID_API_KEY = process.env.LOGINID_API_KEY;

// Simulate a storage mechanism for persisting transaction data
const transactionStore = new Map();

app.post("/validateTx", checkAuthenticated, async (req, res) => {
  try {
    const { username } = req.username;
    const { loginIdToken } = req.body;

    // Verify the LoginID JWT
    await verifyToken(loginIdToken);

    // Decode and verify the JWT token
    const decoded = jwt.decode(loginIdToken);

    // Extract txHash, lNonce, and nonce from the JWT claims
    const { txHash, lNonce, nonce } = decoded;

    // Fetch the original nonce and txPayload from your transaction store
    const { nonce: originalNonce, txPayload } = transactionStore.get(username);

    // Compare nonces
    if (nonce !== originalNonce) {
      throw new Error("Nonce do not match");
    }

    // Calculated hashes should be the same. Look at bottom on
    // how to calculate the hash
    const calculatedHash = calculateTxHash(txPayload, nonce, lNonce);
    if (calculatedHash !== txHash) {
      throw new Error("Transaction payload do not match");
    }

    // Other business logic can go here

    return res.status(204).end();
  } catch (error) {
    res.send(error);
  }
});