Generating the Authentication Key

public static void Main()
{
  var time = DateTime.UtcNow.ToString("yyyyMMddHHmmss");
  var tokenexid = "123456789"; //From client portal
  var clientSecretKey = "A1b2C3D4e5F6h7I8j9K0l1M2n3O4p"; // From client portal
  var tokenScheme = "PCI";
  var origin = "https://www.example.com";
  var concatenatedString = tokenexid+"|"+origin+"|"+time+"|"+tokenScheme;
  var AuthenticationKey = GenerateHMAC(concatenatedString, clientSecretKey);
}

private string GenerateHMAC(string concatenatedInfo, string HMACkey)
{
    var result = string.Empty;
    var hmac = new System.Security.Cryptography.HMACSHA256();
    hmac.Key = System.Text.Encoding.UTF8.GetBytes(HMACkey);
    var hash = hmac.ComputeHash(System.Text.Encoding.UTF8.GetBytes(concatenatedInfo));
    result = Convert.ToBase64String(hash); // Ensure the string returned is Base64 Encoded
    return result;
}

<?php

$timestamp = gmdate("YmdHis");
$tokenexId = "123456789"; //From client portal
$clientSecretKey = "A1b2C3D4e5F6h7I8j9K0l1M2n3O4p"; // From client portal
$tokenScheme = "PCI";
$origin = "https://www.example.com";
$concatenatedString = $tokenexId . '|' . $origin . '|' . $timestamp . '|' . $tokenScheme;
$authenticationKey = GenerateHMAC($concatenatedString, $clientSecretKey);

function GenerateHMAC($concatenatedInfo, $HMACkey) {
    $hmac = hash_hmac('sha256', $concatenatedInfo, $HMACkey, true); //Output needs to be in raw binary data format
    $result = base64_encode($hmac);
    return $result;
}
?>

import hmac
import hashlib
import base64
from datetime import datetime

def generateHMAC(payload, HMACKey):
    payload = payload.encode()
    HMACKey = bytes(HMACKey, 'UTF-8')
    my_hmac = hmac.new(HMACKey,payload,hashlib.sha256)
    return base64.b64encode(my_hmac.digest()).decode()

time = datetime.utcnow().strftime("%Y%m%d%H%M%S")
tokenexid = "123456789" # From client portal
clientSecretKey = "A1b2C3D4e5F6h7I8j9K0l1M2n3O4p" # From client portal
origin = "https://www.example.com"
token_scheme = "PCI"
concatenated = tokenexid + "|" + origin + "|" + time + "|" + token_scheme
AuthenticationKey = generateHMAC(concatenated, clientSecretKey)

/* This example is for Javascript backends, such as Node.js.
 TokenEx strongly recommends generating the authentication key in the backend 
and not exposing your TokenEx credentials within the frontend Javascript. */

var tokenExId = "123456789";
var clientSecretKey = "A1b2C3D4e5F6h7I8j9K0l1M2n3O4p";  // From client portal
var tokenScheme = "PCI";
var timeStamp = new Date().toISOString().replace(/[^0-9]/g, "").slice(0, -3); // outputs UTC date in yyyyMMddHHmmss

function generateHmac() {
  let concatenatedData = tokenExId + "|" + origin + "|" + timeStamp + "|" + tokenScheme;
  let hmac = CryptoJS.HmacSHA256(concatenatedData, clientSecretKey);
  let hmacAsBase64 = CryptoJS.enc.Base64.stringify(hmac);
  return hmacAsBase64;
}