Best Practices for Local Storage in Flutter Apps

When it comes to storing data locally in your Flutter applications, security is paramount. Protecting sensitive information is a shared responsibility between developers and the frameworks we use. Here are some essential practices to consider before employing local storage mechanisms like Shared Preferences or local files using path provider.

1. Encrypt Sensitive Data

Before saving sensitive data locally, consider encrypting it to add an extra layer of security. Use the encrypt package to perform encryption and decryption operations on your data. Here's a simple example for Shared Preferences:

'package:encrypt/encrypt.dart';

void saveEncryptedData(String key, String value) {
  // Use a secure key and IV for encryption
  final key = Key.fromUtf8('my_secure_key');
  final iv = IV.fromLength(16);

  final encrypter = Encrypter(AES(key, iv));

  final encryptedValue = encrypter.encrypt(value);
  SharedPreferences.getInstance().then((prefs) {
    prefs.setString(key, encryptedValue.base64);
  });
}

2. Utilize Secure Storage Plugins

Consider using plugins like flutter secure storage for secure storage of sensitive information. These plugins are designed to store data in a secure manner, providing additional protection against potential threats.

'package:flutter_secure_storage/flutter_secure_storage.dart';

void saveSecureData(String key, String value) {
  FlutterSecureStorage().write(key: key, value: value);
}

3. Validate and Sanitize Data

Before storing any data, validate and sanitize it to ensure that only necessary and valid information is being stored. This helps prevent security vulnerabilities and enhances the overall integrity of your data.

4. Set Appropriate File Permissions

If you're dealing with local files using path provider, set appropriate file permissions to restrict access. The file package can assist with managing file operations and permissions.

'dart:io';

void setFilePermissions(File file) {
  file.setPermissions(
    mode: FilePermissions.mode600,
  );
}

5. Consider App Sandbox and Server-Side Security

Take advantage of the app's sandboxed environment. Files stored in the app's local directories are not directly accessible by other apps. For highly sensitive information, consider implementing server-side security measures as well.

Remember, the security of your app's data is a continuous process. Stay vigilant, stay secure, and keep building amazing Flutter applications!