Hey guys am i doing it right or wrong? My intention is to decode hashes I just encoded of an image. How do I decode ? My code Need reviewed .

base64.dart

//encode:
 Future<void> _encryptionBinary() async {
    int x = 0;
    int y = 100;
    print("Please Enter {content} you want to encrypt:  ");
    String _requestUserFileInput = IO.stdin.readLineSync();
    List _binary = await new IO.File(_requestUserFileInput).readAsBytesSync();
    String _encodedFile = base64.encode(_binary);
    print("Encoded Binary:  $_encodedFile".substring(x, y));
  }
// encode output, lets say b'fftviuynpoiupiuniunsadsadasdsdasdoiufdiytpiu=='
// intention: decode hashes and export to file("picture_name.extension");
//decode:
Future<void> __decryption_Binary() async {
    // To be Reviewed:
    var _decodedBytes;
    var _file;
    print("Please Enter {content} you want to decrypt:  ");
    String _requestUserFileInput = IO.stdin.readLineSync();
    List _binary = await new IO.File(_requestUserFileInput).readAsBytesSync();
    String _encodedFile = base64.encode(_binary);
    _decodedBytes = base64Decode(_encodedFile);
    print("Decoded Binary:  $_encodedFile");
    _file = IO.File("output.png");
    _file.writeAsBytesSync(_decodedBytes);
  }