请问一个解密方法的加密方法，有劳了

public static string HEDET(string etStr)
        {
            byte[] bytes = Encoding.UTF8.GetBytes(Key);
            byte[] rgbIV = Encoding.UTF8.GetBytes(IV);
            byte[] buffer = Convert.FromBase64String(etStr);
            string str = null;
            Rijndael rijndael = Rijndael.Create();
            try
            {
                using (MemoryStream stream = new MemoryStream())
                {
                    using (CryptoStream stream2 = new CryptoStream(stream, rijndael.CreateDecryptor(bytes, rgbIV), CryptoStreamMode.Write))
                    {
                        stream2.Write(buffer, 0, buffer.Length);
                        stream2.FlushFinalBlock();
                        str = Encoding.UTF8.GetString(stream.ToArray());
                    }
                }
            }
            catch
            {
            }
            rijndael.Clear();
            return str;
        }

TripleDESCryptoServiceProvider des = new TripleDESCryptoServiceProvider();
            des.Key = GetMD5(key, encoding);
            des.Mode = CipherMode.ECB;
            return des;