Cachette

Cachette is an encrypted vault for photos, videos and documents. It lives on the phone. The pattern is the key.

You draw a pattern on 25 dots. That pattern opens a vault. A different pattern opens a different vault. An unknown pattern opens an empty vault, after the same wait, so it does not announce that you got it wrong.

There is no account, no password and no server. The app does not request the INTERNET permission, so Android will not open a socket for it. There is no analytics and no crash reporting.

If you forget the pattern, the vault is gone. Nothing on the device can bring it back. There is no reset link, no support ticket and no override, including from us. The way back is a backup you make yourself: one encrypted file, opened by a random 24-word phrase you keep on paper.

A second vault is for the moment someone tells you to unlock. It should look like a phone that has nothing to hide. The other vault stays unprovable. Cachette does not stop coercion. It makes handing over the real vault pointless.

What it does
• Pattern only, at least 6 of 25 dots. Common shapes are refused. No fingerprint, no face.
• AES-256-GCM, a random key per file. Names are random. Sizes are padded.
• The key is stretched with Argon2id, then bound to a key that stays in StrongBox.
• No vault list. Unlock tries every header.
• FLAG_SECURE on every window: no screenshots, recordings, casts or recents thumbnail.
• No permissions at install. Import uses the photo picker or the share sheet. The camera is asked at first use.
• Originals can be deleted immediately, with no 30-day trash.
• App-private storage only. Android cloud backup is off. The screen going off locks the vault and wipes its keys.
• Verify shows the permissions Android holds for the app, read from the system, not from us.

What it cannot do
• Hide how much encrypted data is on the phone. Someone with a full disk image can see the total.
• Reach copies that already left the phone, such as a cloud gallery that synced a photo before you imported it.
• Survive a rooted or infected phone.
• Recover a forgotten pattern.

Private Space can hide that the app exists. When that space is locked, Android removes Cachette from the app list, recents, notifications and Settings.

Remember the pattern. Make the backup. Keep the 24 words.