Protection against hackers

Hi,


My code for credit card protect:


using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Security.Cryptography;
using System.Text;
using System.IO;


public partial class _Default : System.Web.UI.Page
{


private static string decryptString = "abcdefgh";


public static string Decrypt(string stringToDecrypt)
{
byte[] key = { };
byte[] IV = { 10, 20, 30, 40, 50, 60, 70, 80 };
byte[] inputByteArray = new byte[stringToDecrypt.Length];

try
{
key = Encoding.UTF8.GetBytes(decryptString.Substring(0, 8));
DESCryptoServiceProvider des = new DESCryptoServiceProvider();
...