Intro

Whether you’re building a finance tracker, secure messaging app, or just storing sensitive preferences, securing local data is non-negotiable. Flutter makes cross-platform development easy, but encryption support isn’t always straightforward out of the box. That’s where this simple yet powerful project comes in—flutter-cryptography.

Built around the cryptography package, this project demonstrates a practical way to encrypt and decrypt data locally in a Flutter app, using AES-GCM and securely storing keys with flutter_secure_storage.

Why Encrypt Locally?

When storing sensitive data—like access tokens, passwords, or any personal user information—on a device, plain text is not an option. Mobile phones can be compromised, apps can be reverse-engineered, and sensitive data can leak. Encryption ensures:

• Confidentiality: Even if the storage is accessed, the data is unreadable.
• Integrity: AES-GCM provides authentication to prevent tampering.
• Peace of mind: You’re doing right by your users.

What This Demo Covers

The flutter-cryptography repository shows a complete encryption workflow in Dart:

1. Key Generation: On first use, a 256-bit AES key is generated and stored securely using flutter_secure_storage.
2. Encrypting Text: Plain text is encrypted using AES-GCM and encoded in base64 for easy storage.
3. Decrypting Text: The encrypted base64 string is decoded and decrypted using the same key.

The Cryptor class wraps all this logic, making it reusable and simple to integrate into any app.

final encrypted = await cryptor.encrypt('secret message');
final decrypted = await cryptor.decrypt(encrypted);

It’s that straightforward.

Why Use AES-GCM?

AES-GCM (Galois/Counter Mode) is a modern encryption standard that not only encrypts data but also verifies its integrity. It’s fast, secure, and widely supported—ideal for mobile apps.

What You’ll Need

To get started, you’ll need these dependencies in your pubspec.yaml:

dependencies:
  cryptography: ^2.0.3
  flutter_secure_storage: ^9.0.0

Make sure you also configure flutter_secure_storage properly for iOS and Android. See their setup instructions for platform-specific steps.

A Note on Key Management

This example keeps things simple by generating a single key and storing it securely on the device. In real-world apps, you may want:

• Key rotation strategies
• Biometric protection (e.g., using local_auth)
• Remote key storage for more sensitive use cases

Wrap-Up

If you’re looking to build Flutter apps that respect user privacy and handle sensitive data securely, flutter-cryptography is a solid starting point. It’s small, focused, and easy to adapt.

Want to try it yourself? 🔗 View the code on GitHub.