SilentBOX: a private encrypted vault, and what we just added to it
A vault that only exists on one phone is one dropped phone away from being gone.
Most people carry a handful of files they would not want anyone else opening. Identity documents. Contracts. Photographs. Recovery phrases. They usually sit in a phone's gallery or downloads folder, which is to say they sit in the open.
SilentBOX is a vault for those files. Everything you put in it is encrypted on your device, with a key derived from a PIN only you know. This release is the biggest one so far, and it adds the piece that was missing.
Encrypted backup, and you keep it
A vault that only exists on one phone is one dropped phone away from being gone. So SilentBOX now creates a full encrypted backup of everything inside it.
The design matters here. Your files are already encrypted on disk, so a backup copies that ciphertext directly. Nothing is decrypted along the way, which means the readable version of your files never exists during a backup at all. File names are encrypted too, because a list of file names tells someone almost as much as the files do.
Where the backup goes is your decision. It leaves through the system share sheet, so it can land in whatever storage you already use and trust. We hold no token for your storage, and no copy of your vault ever reaches us. There is no sync, and there is no server-side copy to compromise.
Restoring adopts the PIN the backup was made with. It has to: those files are encrypted with the key derived from that PIN, and doing anything else would hand you files that could never be opened again. The app tells you this plainly before it proceeds.
The backup streams one file at a time rather than assembling the whole vault in memory, so a large vault restores as reliably as a small one.
Also new in this release
Instant hide, so the vault can be closed in one movement without unlocking anything.
Biometric unlock, handled by the Android Keystore.
A hardened unlock path, rebuilt so that the vault does not announce itself.
The app is rebuilt on a current Android toolchain with full 16 KB memory page support, which is now a requirement rather than an optimisation.
The security, stated precisely
AES-256-GCM, applied per file, each with its own initialisation vector.
PBKDF2-SHA256 at 100,000 iterations to derive your key from your PIN.
Your PIN is never stored. We keep a hash and a salt, which is what lets the app tell a correct PIN from a wrong one without ever holding the PIN itself.
No vault content, no file name and no PIN ever leaves your device. The only network call the app makes is a subscription status check, and it carries none of your data.
This release ships behind 126 automated checks across seven suites covering the encryption, the backup format and the unlock path. Those checks include restoring backups whose file names are in Arabic, Japanese or emoji, and reading them in deliberately awkward chunk sizes, because a restore that quietly corrupts a vault would be the worst failure this product could have.
Why we publish the specifics
"Bank grade encryption" is a phrase that means nothing and can be checked by nobody. AES-256-GCM with a per file initialisation vector, and PBKDF2 at 100,000 iterations, means something precise and can be verified.
A privacy app asks for an unusual amount of trust. The only way to earn it is to say exactly what the software does, in terms specific enough to be wrong about, and then be right.