DES数据解密

        /// <summary>
        /// DES数据解密
        /// </summary>
        /// <param name="targetValue"></param>
        /// <param name="key"></param>
        /// <returns></returns>
        public static string Decrypt(string targetValue, string key = "test")
        {
            if (string.IsNullOrEmpty(targetValue))
            {
                return string.Empty;
            }
            // 定义DES加密对象
            try
            {
                var des = new DESCryptoServiceProvider();
                int len = targetValue.Length / 2;
                var inputByteArray = new byte[len];
                int x, i;
                for (x = 0; x < len; x++)
                {
                    i = Convert.ToInt32(targetValue.Substring(x * 2, 2), 16);
                    inputByteArray[x] = (byte)i;
                }
                // 通过两次哈希密码设置对称算法的初始化向量   
                des.Key = Encoding.ASCII.GetBytes(FormsAuthentication.HashPasswordForStoringInConfigFile
                                                      (FormsAuthentication.HashPasswordForStoringInConfigFile(key, "md5").
                                                           Substring(0, 8), "sha1").Substring(0, 8));
                // 通过两次哈希密码设置算法的机密密钥   
                des.IV = Encoding.ASCII.GetBytes(FormsAuthentication.HashPasswordForStoringInConfigFile
                                                     (FormsAuthentication.HashPasswordForStoringInConfigFile(key, "md5")
                                                          .Substring(0, 8), "md5").Substring(0, 8));
                // 定义内存流
                var ms = new MemoryStream();
                // 定义加密流
                var cs = new CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Write);
                cs.Write(inputByteArray, 0, inputByteArray.Length);
                cs.FlushFinalBlock();
                return Encoding.Default.GetString(ms.ToArray());
            }
            catch
            {
            }
            return string.Empty;
        }