Cloud backup

How to connect Dropbox and what "end-to-end encrypted" means in practice.

How Mētra backup works

Your data never leaves your device unless you decide it should. Local-first is not a feature toggle, it is the default state. Backup is an option, not an expectation.

When you enable it, Mētra encrypts your entire database on your device before uploading it. Dropbox receives a blob it cannot read. No one else has access to your data, including the people who wrote the code.

⚠️ There is no passphrase reset. The encryption key is derived from your passphrase and lives only on your device — not on any server, not in the cloud. If you lose the passphrase, the backup cannot be recovered. Keep it somewhere safe, separate from your phone (e.g. a password manager).

Connecting a cloud provider

Go to Settings → Cloud backup.
Tap Connect Dropbox.
Your browser opens the provider’s login page.
Once you authorise the connection, you’re returned to Mētra.

Mētra requests the minimum permissions: only access to a dedicated app folder, not your full cloud storage.

Creating a backup

Once connected:

Tap Back up now.
Mētra asks for your passphrase, the same one used to encrypt the backup. You will need it unchanged to restore.
Mētra encrypts the database on your device and uploads it. A progress indicator shows the status.
When complete, the screen displays the date and time of the last successful backup.

On the passphrase: there is no recovery option, because there is no server that could perform one. Choose a passphrase you will remember and store it separately from your phone.

After the initial backup, Mētra will perform periodic backups automatically.

Mētra automatically keeps the 3 most recent encrypted backups in the cloud folder; older blobs are pruned after each successful upload. No user-tunable setting — local-first / respect-the-adult-user posture.

What is backed up

The backup contains the complete contents of your encrypted database:

All daily logs (flow, pain, symptoms, notes).
Cycle entries derived from your logs.
App settings (cycle-length baseline, notification preferences).

It does not include local notification schedule state: those are re-created automatically after a restore.

Restoring from a backup

Install Mētra on the new device (or after a factory reset).
Complete the onboarding flow, the baseline numbers do not matter, they will be overwritten by the restore.
Go to Settings → Cloud backup.
Connect your Dropbox account. If backups are found, Mētra will indicate it and show when the most recent one was created.
Tap Restore from backup and confirm in the warning dialog that current data will be replaced.
A picker sheet appears: scroll the wheel to select the backup version you want. Each entry shows date, time, and file size (up to 3 backups available, newest at the top).
Tap Restore to confirm, or Cancel to go back.
Enter your passphrase. Mētra downloads the chosen backup, decrypts it, and replaces the local database.

⚠️ Warning: Restoring overwrites all data currently on the device. This action cannot be undone.

Disconnecting the provider

Tap Disconnect in the backup screen to unlink the cloud account. The backup files already on the cloud are not deleted, you must delete them manually from the Dropbox app or website.

Mētra now retains up to the 3 most recent encrypted blobs in the App folder.

Technical security details

Encryption algorithm: AES-256-GCM.
Key derivation: Argon2id from your passphrase.
The key is never stored in the cloud, never sent to any server, and never stored on the device itself: it is derived from the passphrase each time it is needed, then discarded.
The backup file has a .enc extension and is stored in a dedicated Mētra folder inside your cloud account.

These are not marketing claims: they are specific choices in the code. You can verify them in lib/data/services/encryption_service.dart.