authenticated-encryption.js

'use strict';
const crypto = require('crypto');

// The two keys gotten from Trustpilot
let encryptionKeyBase64 = 'XCxIAot+Tr6FVbU5fROwe2ckBEoFDcb6gwBT8022oVs=';
let authenticationKeyBase64 = 'wNh58yFZ58H+QPomgWkgPqM3JZegQqpg39k06Q4ZvrA=';
let domain = 'my-domain.com';

// Our order to encrypt
let order = {
    "email":"xyz@domain.com",
    "name":"John Smith",
    "ref":"1234",
    "skus":["sku1","sku2","sku3"],
    "tags":["tag1","tag2","tag3"]
};
let jsonSerializedOrder = JSON.stringify(order);

// When you get the keys from Trustpilot, they are base64 encoded, so first we need to decode them
let encryptionKey = Buffer.from(encryptionKeyBase64, 'base64');
let authenticationKey = Buffer.from(authenticationKeyBase64, 'base64');

// Generate a random initialization vector
let iv = crypto.randomBytes(16);

// Encrypt our order
let cipher = crypto.createCipheriv('aes-256-cbc', encryptionKey, iv);
let cipherText = Buffer.concat([cipher.update(jsonSerializedOrder, 'utf8'), cipher.final()]);

// Compute the HMAC
let hmac = crypto.createHmac('sha256', authenticationKey).update(Buffer.concat([iv, cipherText])).digest();

// Base64 encode the IV + cipherText + HMAC
let base64Payload = Buffer.concat([iv, cipherText, hmac]).toString("base64");

// URL encode to get the final payload
let payload = encodeURIComponent(base64Payload);

// The final url
let url = 'https://www.trustpilot.com/evaluate-bgl/' + domain + '?p=' + payload;

console.log(url);