using System;

using System.Text;

using System.Security.Cryptography;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        string hashKey = "QcCBxuhaYbYkzm4B";

        string terminalId = "99966254";

        string reference = "0987654321A";

        string amount = "13.00";

         Console.WriteLine(Convert.ToBase64String(new SHA1CryptoServiceProvider().ComputeHash(Encoding.UTF8.GetBytes(string.Concat(hashKey, terminalId, reference, amount)))));

         Console.WriteLine(string.Concat(hashKey, terminalId, reference, amount));

​

​

    }

}