关于DES加密码的有关问题

using System;using System.Collections.Generic;using System.Text;using System.IO;using System.Security.Cryptography;namespace WindowsFormsApplication1{    /// <summary>    /// 加密解密操作类    /// </summary>    public class EDHelper    {                private static SymmetricAlgorithm mCSP = new DESCryptoServiceProvider();        private static string vectorKey = "T/Zl4XkLe8I=";//"cEbmGVzevBs=";        private static string ivKey = "5vikZLWsu7g=";//"EHCtpIFk84I=";        /// <summary>        /// 对一个字符串进行加密        /// </summary>        /// <param name="str">需要加密的字符串</param>        /// <returns>返回一个后的字符串</returns>        public static string Encrypt(string str)        {            if (string.IsNullOrEmpty(str))                return "";            try            {                byte[] bytes;                string strResult = string.Empty;                ICryptoTransform ct = mCSP.CreateEncryptor(Convert.FromBase64String(vectorKey), Convert.FromBase64String(ivKey));                bytes = Encoding.UTF8.GetBytes(str);                using (MemoryStream ms = new MemoryStream())                {                    CryptoStream cs = new CryptoStream(ms, ct, CryptoStreamMode.Write);                    cs.Write(bytes, 0, bytes.Length);                    cs.FlushFinalBlock();                    cs.Close();                    strResult = Convert.ToBase64String(ms.ToArray());                }                return strResult;            }            catch            {                return "";            }        }        /// <summary>        /// 对加密的字符串进行解密        /// </summary>        /// <param name="str">需要解密的内容</param>        /// <returns>解密后的字符串</returns>        public static string Decrypt(string str)        {            if (string.IsNullOrEmpty(str))                return "";            try            {                byte[] bytes;                string strResult = string.Empty;                ICryptoTransform ct = mCSP.CreateDecryptor(Convert.FromBase64String(vectorKey), Convert.FromBase64String(ivKey));                bytes = Convert.FromBase64String(str);                using (MemoryStream ms = new MemoryStream())                {                    CryptoStream cs = new CryptoStream(ms, ct, CryptoStreamMode.Write);                    cs.Write(bytes, 0, bytes.Length);                    cs.FlushFinalBlock();                    cs.Close();                    strResult = Encoding.UTF8.GetString(ms.ToArray());                }                return strResult;            }            catch { return ""; }        }        /// <summary>        /// 根据字符串获取MD5哈希值        /// </summary>        /// <param name="str">目标字符串</param>        /// <returns>返回MD5哈希值</returns>        public static int GetMD5Hash(string str)        {            MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();            byte[] hash = md5.ComputeHash(System.Text.Encoding.Unicode.GetBytes(str));            Int32 hashInt = System.BitConverter.ToInt32(hash, 0);            return hashInt;        }    }}