Encrypted Flutter Expense Tracker

A cross-platform Flutter sample that stores expenses in an encrypted SQLite database using the published sqlite_encrypted package and official SQLite Encryption Extension (SEE).

The sample demonstrates:

• installing SQLite.Encrypted packages from packages.sourcegear.com;
• activating SEE and reporting missing or invalid activation keys clearly;
• opening an encrypted database with the keyed openDatabase() API;
• ordinary sqflite inserts, queries, filtering, and deletes;
• generating a random database key and protecting it with the platform's secure credential store; and
• using the same application on Android, iOS, Windows, macOS, and Linux.

Prerequisites

• Flutter with tooling for your target platform
• a SQLite.Encrypted activation key.

Free fully-featured demo keys are available from sqlite.sourcegear.com.

The activation key must cover the platform and SQLite minor version bundled in the selected sqlite_encrypted package. An activation key issued for an older minor version will be rejected by a newer package.

The value passed to activateSee() is the activation hex string itself. Do not include the see- prefix used by the PRAGMA form.

On iOS, the sample enables Keychain Sharing as required by flutter_secure_storage. On macOS it uses the legacy Keychain so a local sample build does not require a provisioning profile.

On Linux, flutter_secure_storage requires the system libsecret development package. For Debian or Ubuntu:

sudo apt-get install libsecret-1-dev

Run the sample

From this directory:

flutter pub get
flutter run \
  --dart-define=SQLITE_ENCRYPTED_ACTIVATION_KEY=<your-activation-key>

Select a target explicitly when more than one is available:

flutter run -d windows \
  --dart-define=SQLITE_ENCRYPTED_ACTIVATION_KEY=<your-activation-key>

PowerShell uses a backtick instead of a backslash for line continuation:

flutter run -d windows `
  --dart-define=SQLITE_ENCRYPTED_ACTIVATION_KEY=<your-activation-key>

Other common device values include macos, linux, and the identifier shown by flutter devices for a phone, simulator, or emulator.

The activation key is supplied as a compile-time definition for this compact sample. Production applications should choose a delivery strategy appropriate to their threat model rather than committing the key to source control.

Package source

Both SQLite.Encrypted Flutter packages come from the SourceGear Pub repository:

dependencies:
  sqflite_common_ffi:
    hosted: https://packages.sourcegear.com/pub
    version: 3.54.0
  sqlite_encrypted:
    hosted: https://packages.sourcegear.com/pub
    version: 3.54.0

The application calls sqfliteFfiInit() on desktop platforms before assigning databaseFactoryFfi. Mobile platforms use the platform implementation selected by the sqlite_encrypted package.

Key handling

On first launch, the app creates a random 256-bit database key and stores it with flutter_secure_storage. Later launches retrieve that same key before opening expense_tracker.db. Expense data is manipulated through the ordinary sqflite API after the keyed open succeeds.

Removing the application's secure-storage entry while retaining its database will make that database unreadable. A real application should define its own backup, recovery, and key-rotation policy.