System.Security.Cryptography.DESCryptoServiceProvider.CreateDecryptor C# (CSharp) Method

        public override ICryptoTransform CreateDecryptor()
        {
            return CreateTransform(Key, IV, encrypting: false);
        }

 /// <summary>
 /// 解密
 /// </summary>
 /// <param name="text">要被解密字符</param>
 /// <param name="sKey">密钥</param>
 /// <returns></returns>
 public static string Decrypt(this string text, string sKey)
 {
     var provider = new DESCryptoServiceProvider();
     int num = text.Length / 2;
     byte[] buffer = new byte[num];
     try
     {
         for (int i = 0; i < num; i++)
         {
             int num3 = Convert.ToInt32(text.Substring(i * 2, 2), 0x10);
             buffer[i] = (byte)num3;
         }
     }
     catch
     {
         return string.Empty;
     }
     provider.Key = Encoding.ASCII.GetBytes(FormsAuthentication.HashPasswordForStoringInConfigFile(sKey, "md5").Substring(0, 8));
     provider.IV = Encoding.ASCII.GetBytes(FormsAuthentication.HashPasswordForStoringInConfigFile(sKey, "md5").Substring(0, 8));
     MemoryStream stream = new MemoryStream();
     CryptoStream stream2 = new CryptoStream(stream, provider.CreateDecryptor(), CryptoStreamMode.Write);
     try
     {
         stream2.Write(buffer, 0, buffer.Length);
         stream2.FlushFinalBlock();
     }
     catch
     {
         return string.Empty;
     }
     return Encoding.Default.GetString(stream.ToArray());
 }