ICryptoTransform can not work on the Android phone

public static string Encrypt(string data, string secret) {

     TripleDESCryptoServiceProvider des = new TripleDESCryptoServiceProvider();
     MD5 md5 = MD5.Create();

     string key = GetMd5Hash(md5, secret);
     byte[] finalKey = System.Text.Encoding.UTF8.GetBytes(key); 
     
     des.Mode = CipherMode.ECB;
     des.Key = finalKey;
     des.Padding = PaddingMode.PKCS7;

     ICryptoTransform DESEncrypt = des.CreateEncryptor();

     Byte[] Buffer = ASCIIEncoding.ASCII.GetBytes(data);

     return (Convert.ToBase64String(DESEncrypt.TransformFinalBlock(Buffer, 0, Buffer.Length)));
 }

The encryption code works fine on Unity 5.1 and Android as well, when i changed my Unity version to 5.3, it works on the PC(I can get the encrypt result and print it in editor) but failed on Android, i tried to do debug on Android, it doesn't return a result because the script was stop in the ICryptoTransform DESEncrypt = des.CreateEncryptor(); line. Is that an Unity bug ? because it works fine in the older version, and also can work on the PC in Unity 5.3 version but fail on Android. Thanks for the help