<?php
function generateHash($params, $salt) {
    // Extract parameters or use empty string if not provided
    $key = $params['key'];
    $txnid = $params['txnid'];
    $amount = $params['amount'];
    $productinfo = $params['productinfo'];
    $firstname = $params['firstname'];
    $email = $params['email'];
    $udf1 = isset($params['udf1']) ? $params['udf1'] : '';
    $udf2 = isset($params['udf2']) ? $params['udf2'] : '';
    $udf3 = isset($params['udf3']) ? $params['udf3'] : '';
    $udf4 = isset($params['udf4']) ? $params['udf4'] : '';
    $udf5 = isset($params['udf5']) ? $params['udf5'] : '';
    
    // Construct hash string with exact parameter sequence
    $hashString = $key . '|' . $txnid . '|' . $amount . '|' . $productinfo . '|' . 
                  $firstname . '|' . $email . '|' . $udf1 . '|' . $udf2 . '|' . 
                  $udf3 . '|' . $udf4 . '|' . $udf5 . '||||||' . $salt;
    
    // Generate hash and convert to lowercase
    return strtolower(hash('sha512', $hashString));
}

// Example usage
$params = [
    'key' => 'yourKey',
    'txnid' => 'yourTxnId',
    'amount' => 'yourAmount',
    'productinfo' => 'yourProductInfo',
    'firstname' => 'yourFirstName',
    'email' => 'yourEmail',
    'udf1' => 'optional_value1'
    // udf2, udf3, udf4, udf5 not provided - will be empty strings
];
$salt = 'yourSalt';

$hash = generateHash($params, $salt);
echo 'Generated Hash: ' . $hash;
?>

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.HashMap;
import java.util.Map;

public class ImprovedHashGenerator {

    public static String generateHash(Map<String, String> params, String salt) {
        // Extract parameters or use empty string if not provided
        String key = params.get("key");
        String txnid = params.get("txnid");
        String amount = params.get("amount");
        String productinfo = params.get("productinfo");
        String firstname = params.get("firstname");
        String email = params.get("email");
        String udf1 = params.getOrDefault("udf1", "");
        String udf2 = params.getOrDefault("udf2", "");
        String udf3 = params.getOrDefault("udf3", "");
        String udf4 = params.getOrDefault("udf4", "");
        String udf5 = params.getOrDefault("udf5", "");
        
        // Construct hash string with exact parameter sequence
        String hashString = key + "|" + txnid + "|" + amount + "|" + productinfo + "|" + 
                         firstname + "|" + email + "|" + udf1 + "|" + udf2 + "|" + 
                         udf3 + "|" + udf4 + "|" + udf5 + "||||||" + salt;
        
        return sha512(hashString);
    }

    private static String sha512(String input) {
        try {
            MessageDigest md = MessageDigest.getInstance("SHA-512");
            byte[] hashBytes = md.digest(input.getBytes(StandardCharsets.UTF_8));
            StringBuilder sb = new StringBuilder();
            for (byte b : hashBytes) {
                sb.append(String.format("%02x", b));
            }
            return sb.toString().toLowerCase();
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(e);
        }
    }

    public static void main(String[] args) {
        // Example usage with parameters map
        Map<String, String> params = new HashMap<>();
        params.put("key", "yourKey");
        params.put("txnid", "yourTxnId");
        params.put("amount", "yourAmount");
        params.put("productinfo", "yourProductInfo");
        params.put("firstname", "yourFirstName");
        params.put("email", "yourEmail");
        params.put("udf1", "optional_value1");
        // udf2, udf3, udf4, udf5 not provided - will be empty strings
        
        String salt = "yourSalt";

        String hash = generateHash(params, salt);
        System.out.println("Generated Hash: " + hash);
    }
}

using System;
using System.Collections.Generic;
using System.Security.Cryptography;
using System.Text;

public class ImprovedHashGenerator
{
    public static string GenerateHash(Dictionary<string, string> parameters, string salt)
    {
        // Extract parameters or use empty string if not provided
        string key = parameters["key"];
        string txnid = parameters["txnid"];
        string amount = parameters["amount"];
        string productinfo = parameters["productinfo"];
        string firstname = parameters["firstname"];
        string email = parameters["email"];
        
        // Get UDF values if present, otherwise use empty string
        string udf1 = parameters.ContainsKey("udf1") ? parameters["udf1"] : "";
        string udf2 = parameters.ContainsKey("udf2") ? parameters["udf2"] : "";
        string udf3 = parameters.ContainsKey("udf3") ? parameters["udf3"] : "";
        string udf4 = parameters.ContainsKey("udf4") ? parameters["udf4"] : "";
        string udf5 = parameters.ContainsKey("udf5") ? parameters["udf5"] : "";
        
        // Construct hash string with exact parameter sequence
        string hashString = $"{key}|{txnid}|{amount}|{productinfo}|{firstname}|{email}|{udf1}|{udf2}|{udf3}|{udf4}|{udf5}||||||{salt}";
        
        return Sha512(hashString);
    }

    private static string Sha512(string input)
    {
        using (SHA512 sha512 = SHA512.Create())
        {
            byte[] bytes = sha512.ComputeHash(Encoding.UTF8.GetBytes(input));
            StringBuilder sb = new StringBuilder();
            foreach (byte b in bytes)
            {
                sb.Append(b.ToString("x2"));
            }
            return sb.ToString().ToLower();
        }
    }

    public static void Main(string[] args)
    {
        // Example usage with parameters dictionary
        Dictionary<string, string> parameters = new Dictionary<string, string>
        {
            ["key"] = "yourKey",
            ["txnid"] = "yourTxnId",
            ["amount"] = "yourAmount",
            ["productinfo"] = "yourProductInfo",
            ["firstname"] = "yourFirstName",
            ["email"] = "yourEmail",
            ["udf1"] = "optional_value1"
            // udf2, udf3, udf4, udf5 not provided - will be empty strings
        };
        
        string salt = "yourSalt";

        string hash = GenerateHash(parameters, salt);
        Console.WriteLine("Generated Hash: " + hash);
    }
}

import hashlib

def generate_hash(params, salt):
    # Extract parameters or use empty string if not provided
    key = params['key']
    txnid = params['txnid']
    amount = params['amount']
    productinfo = params['productinfo']
    firstname = params['firstname']
    email = params['email']
    udf1 = params.get('udf1', '')
    udf2 = params.get('udf2', '')
    udf3 = params.get('udf3', '')
    udf4 = params.get('udf4', '')
    udf5 = params.get('udf5', '')
    
    # Construct hash string with exact parameter sequence
    hash_string = f"{key}|{txnid}|{amount}|{productinfo}|{firstname}|{email}|{udf1}|{udf2}|{udf3}|{udf4}|{udf5}||||||{salt}"
    
    # Generate SHA-512 hash
    return hashlib.sha512(hash_string.encode('utf-8')).hexdigest()

# Example usage
params = {
    'key': 'yourKey',
    'txnid': 'yourTxnId',
    'amount': 'yourAmount',
    'productinfo': 'yourProductInfo',
    'firstname': 'yourFirstName',
    'email': 'yourEmail',
    'udf1': 'optional_value1'
    # udf2, udf3, udf4, udf5 not provided - will default to empty strings
}
salt = 'yourSalt'

hash_value = generate_hash(params, salt)
print("Generated Hash:", hash_value)

const crypto = require('crypto');

function generateHash(params, salt) {
    // Extract parameters or use empty string if not provided
    const key = params.key;
    const txnid = params.txnid;
    const amount = params.amount;
    const productinfo = params.productinfo;
    const firstname = params.firstname;
    const email = params.email;
    const udf1 = params.udf1 || '';
    const udf2 = params.udf2 || '';
    const udf3 = params.udf3 || '';
    const udf4 = params.udf4 || '';
    const udf5 = params.udf5 || '';
    
    // Construct hash string with exact parameter sequence
    const hashString = `${key}|${txnid}|${amount}|${productinfo}|${firstname}|${email}|${udf1}|${udf2}|${udf3}|${udf4}|${udf5}||||||${salt}`;
    
    // Generate SHA-512 hash
    return crypto.createHash('sha512').update(hashString).digest('hex');
}

// Example usage
const params = {
    key: 'yourKey',
    txnid: 'yourTxnId',
    amount: 'yourAmount',
    productinfo: 'yourProductInfo',
    firstname: 'yourFirstName',
    email: 'yourEmail',
    udf1: 'optional_value1'
    // udf2, udf3, udf4, udf5 not provided - will default to empty strings
};
const salt = 'yourSalt';

const hash = generateHash(params, salt);
console.log("Generated Hash:", hash);