```dart
import 'dart:io';
import 'package:path_provider/path_provider.dart';

Future<void> uploadProtected() async {
  // Create a dummy file
  const exampleString = 'Example file contents';
  final tempDir = await getTemporaryDirectory();
  final exampleFile = File(tempDir.path + '/example.txt')
    ..createSync()
    ..writeAsStringSync(exampleString);

  // Set the access level to `protected` for the current user
  // Note: A user must be logged in through Cognito Auth
  // for this to work.
  final uploadOptions = S3UploadFileOptions(
    accessLevel: StorageAccessLevel.protected,
  );

  // Upload the file to S3 with protected access
  try {
    final UploadFileResult result = await Amplify.Storage.uploadFile(
        local: exampleFile,
        key: 'ExampleKey',
        options: uploadOptions,
        onProgress: (progress) {
          safePrint('Fraction completed: ${progress.getFractionCompleted()}');
        }
    );
    safePrint('Successfully uploaded file: ${result.key}');
  } on StorageException catch (e) {
    safePrint('Error uploading protected file: $e');
  }
}
```