C#實現3DES加密 24位密鑰

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

namespace ConsoleApplication1
{
    class Program
    {
        public static string Encrypt3DES(string a_strString, string a_strKey)
        {
            TripleDESCryptoServiceProvider DES = new TripleDESCryptoServiceProvider();

            DES.Key = ASCIIEncoding.ASCII.GetBytes(a_strKey);
            DES.Mode = CipherMode.ECB;

            ICryptoTransform DESEncrypt = DES.CreateEncryptor();

            byte[] Buffer = ASCIIEncoding.ASCII.GetBytes(a_strString);
            return Convert.ToBase64String(DESEncrypt.TransformFinalBlock(Buffer, 0, Buffer.Length));
        }   

        public static string Decrypt3DES(string a_strString, string a_strKey)
        {
            TripleDESCryptoServiceProvider DES = new TripleDESCryptoServiceProvider();

            DES.Key = ASCIIEncoding.ASCII.GetBytes(a_strKey);
            DES.Mode = CipherMode.ECB;
            DES.Padding = System.Security.Cryptography.PaddingMode.PKCS7;

            ICryptoTransform DESDecrypt = DES.CreateDecryptor();

            string result = "";
            try
            {
                byte[] Buffer = Convert.FromBase64String(a_strString);
                result = ASCIIEncoding.ASCII.GetString(DESDecrypt.TransformFinalBlock(Buffer, 0, Buffer.Length));
            }
            catch (Exception e)
            {

            }
            return result;
        }   

        static void Main(string[] args)
        {
            Console.WriteLine(Encrypt3DES("999999999", "#s^un2ye31<cn%|aoXpR,+vh");
            Console.ReadLine();
        }
    }
}