C#加密解密

        /// <summary>   
        /// DeCode 解密   
        /// </summary>   
        /// <param name="str">要解密的字符串</param>   
        /// <returns></returns>   
        public static String DeCode(String data)
        {
            byte[] byKey = System.Text.ASCIIEncoding.ASCII.GetBytes(KEY_64);
            byte[] byIV = System.Text.ASCIIEncoding.ASCII.GetBytes(IV_64);
            byte[] byEnc;
            try
            {
                byEnc = Convert.FromBase64String(data);
            }
            catch
            {
                return null;
            }
            DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider();
            MemoryStream ms = new MemoryStream(byEnc);
            CryptoStream cst = new CryptoStream(ms, cryptoProvider.CreateDecryptor(byKey, byIV), CryptoStreamMode.Read);
            StreamReader sr = new StreamReader(cst);
            return sr.ReadToEnd();
        }
        /// <summary>   
        /// EnCode 加密   
        /// </summary>   
        /// <param name="str">要加密的字符串</param>   
        /// <returns></returns>   
        const String KEY_64 = "VavicApp";//注意了，是8个字符，64位
        const String IV_64 = "VavicApp";
        public static String EnCode(String data)
        {
            byte[] byKey = System.Text.ASCIIEncoding.ASCII.GetBytes(KEY_64);
            byte[] byIV = System.Text.ASCIIEncoding.ASCII.GetBytes(IV_64);
            DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider();
            int i = cryptoProvider.KeySize;
            MemoryStream ms = new MemoryStream();
            CryptoStream cst = new CryptoStream(ms, cryptoProvider.CreateEncryptor(byKey, byIV), CryptoStreamMode.Write);
            StreamWriter sw = new StreamWriter(cst);
            sw.Write(data);
            sw.Flush();
            cst.FlushFinalBlock();
            sw.Flush();
            return Convert.ToBase64String(ms.GetBuffer(), 0, (int)ms.Length);
        }