private void Rijndael_Decrypt_Click(object sender, RoutedEventArgs e)
        {
            var tempText = RijndaelEncryptTextBlock.Text;

            var decryptedText = MyRijndael.Decrypt(tempText, NetworkInterface.GetAllNetworkInterfaces()[0].GetPhysicalAddress().ToString());

            RijndaelDecryptTextBlock.Text = decryptedText;
        }
        private void Rijndael_Click(object sender, RoutedEventArgs e)
        {
            var tempText = RijndaelTextBlock.Text;

            // key is current MAC address
            var encryptedText = MyRijndael.Encrypt(tempText, NetworkInterface.GetAllNetworkInterfaces()[0].GetPhysicalAddress().ToString());

            RijndaelEncryptTextBlock.Text = encryptedText;
        }