<?php
   $appId = "<your_app_id>"; //replace it with your appId
   $secretKey = "<your_secret_key">; //replace it with your secret key
   $orderId = "1234";
   $orderAmount = 450;
   $customerEmail = [email protected]
   $customerPhone = 99000XXXXX;
   $tokenData = "appId=".$appId."&orderId=".$orderId."&orderAmount=".$orderAmount."&customerEmail=".$customerEmail."&customerPhone=".$customerPhone."&orderCurrency=".$orderCurrency;
   $token = hash_hmac('sha256', $tokenData, $secretKey, true);
   $paymentToken = base64_encode($token);
 ?>

import hashlib
import hmac
import base64

data = "appId=" + appId + "&orderId=" + orderId + "&orderAmount=" + orderAmount + "&customerEmail=" + customerEmail + "&customerPhone=" + customerPhone + "&orderCurrency=" + orderCurrency;
message = bytes(data).encode('utf-8')
secret = bytes(secretKey).encode('utf-8')
paymentToken = base64.b64encode(hmac.new(secret, message,digestmod=hashlib.sha256).digest())

String data = "appId=" + appId + "&orderId=" + orderId + "&orderAmount=" + orderAmount + "&customerEmail=" + customerEmail + "&customerPhone=" + customerPhone + "&orderCurrency=" + $orderCurrency;
  Mac sha256_HMAC = Mac.getInstance("HmacSHA256");
  SecretKeySpec skspec = new SecretKeySpec(secretKey.getBytes(),"HmacSHA256");
  sha256_HMAC.init(skspec);
  paymentToken = Base64.encodeBase64String(sha256_HMAC.doFinal(data.getBytes()));

using System;
using System.Security.Cryptography;

namespace HttpUtils
{
  public class CashFreeToken
  {
     private string CreateToken(string message, string secret){
       secret = secret ?? "";
       var encoding = new System.Text.ASCIIEncoding();
       byte[] keyByte = encoding.GetBytes(secret);
       byte[] messageBytes = encoding.GetBytes(message);
       using (var hmacsha256 = new HMACSHA256(keyByte))
       {
         byte[] hashmessage = hmacsha256.ComputeHash(messageBytes);
         return Convert.ToBase64String(hashmessage);
       }
     }

     public static void Main() {
       String appId = "<Your_APP_ID>";
       String orderId = "<Your_Order_ID>";
       String orderAmount = "<Order_amount>";
       String customerEmail = "<return_url>";
       String customerPhone = "";
       String secret = "<secret_key>";

       String data = "appId=" + appId + "&orderId=" + orderId + "&orderAmount=" + orderAmount + "&customerEmail=" + customerEmail + "&customerPhone=" + customerPhone + "&orderCurrency=" + $orderCurrency;

       CashFreeToken n = new CashFreeToken();
       String signature = n.CreateToken(data, secret);
       Console.WriteLine(signature);
     }
  }
}

<?php  
 $orderId = $_POST["orderId"];
 $orderAmount = $_POST["orderAmount"];
 $referenceId = $_POST["referenceId"];
 $txStatus = $_POST["txStatus"];
 $paymentMode = $_POST["paymentMode"];
 $txMsg = $_POST["txMsg"];
 $txTime = $_POST["txTime"];
 $signature = $_POST["signature"];
 $data = $orderId.$orderAmount.$referenceId.$txStatus.$paymentMode.$txMsg.$txTime;
 $hash_hmac = hash_hmac('sha256', $data, $secretkey, true) ;
 $computedSignature = base64_encode($hash_hmac);
 if ($signature == $computedSignature) {
    // Proceed
  } else {
   // Reject this call
 }
 ?>

import hashlib
import hmac
import base64

@app.route('/notify_url/', methods=["POST"])
def notify_url_process():

 postData = {
  "orderId" : request.form['orderId'], 
  "orderAmount" : request.form['orderAmount'], 
  "referenceId" : request.form['referenceId'], 
  "txStatus" : request.form['txStatus'], 
  "paymentMode" : request.form['paymentMode'], 
  "txMsg" : request.form['txMsg'], 
  "txTime" : request.form['txTime'], 
 }

 signatureData = postData["orderId"] + postData["orderAmount"] + postData["referenceId"] + postData["txStatus"] + postData["paymentMode"] + postData["txMsg"] + postData["txTime"]

 message = bytes(signatureData).encode('utf-8')
 #get secret key from your config
 secret = bytes(secretKey).encode('utf-8')
 signature = base64.b64encode(hmac.new(secret, 
   message,digestmod=hashlib.sha256).digest())

LinkedHashMap<String, String> postData = new LinkedHashMap<String, String>();

postData.put("orderId", ORDERID);
postData.put("orderAmount", ORDERAMOUNT);
postData.put("referenceId", REFERENCE_ID);
postData.put("txStatus", TXN_STATUS);
postData.put("paymentMode", PAYMENT_MODE);
postData.put("txMsg", TX_MSG);
postData.put("txTime", TX_TIME);

String data = "";
Set<String> keys = postData.keySet();

for (String key : keys) {
    data = data + postData.get(key);
}
String secretKey = "" // Get secret key from config;
Mac sha256_HMAC = Mac.getInstance("HmacSHA256");
SecretKeySpec secret_key_spec = new
SecretKeySpec(secretKey.getBytes(),"HmacSHA256");
sha256_HMAC.init(secret_key_spec);

String signature = Base64.getEncoder().encodeToString(sha256_HMAC.doFinal(data.getBytes()));

using System;
using System.Security.Cryptography;
using System.Collections.Generic;
namespace Rextester {
  public class Program {
    private string CreateToken(string message, string secret){
      secret = secret ?? "";
      var encoding = new System.Text.ASCIIEncoding();
      byte[] keyByte = encoding.GetBytes(secret);
      byte[] messageBytes = encoding.GetBytes(message);
      
      using (var hmacsha256 = new HMACSHA256(keyByte))
      {
        byte[] hashmessage = hmacsha256.ComputeHash(messageBytes);
        return Convert.ToBase64String(hashmessage);
      }
    }

    public static void Main(string[] args) {
        
      string secret = "<your_secret_key>";
      string data = "";  
        
      data = data + "FEX101";
      data = data + "10.00";
      data = data + "19992";
      data = data + "SUCCESS";
      data = data + "pg";
      data = data + "payment done";
      data = data + "2018-02-02 17:29:12";

      Program n = new Program();
      string signature = n.CreateToken(data, secret);
      Console.WriteLine(signature);
    }
  }
}