How OwlVault encryption works, and what it can’t protect

The short version

Everything in a vault is encrypted with AES-256-GCM on your iPhone, before it is saved.
To open a vault you need your pattern or PIN and this iPhone. A copy of the files without the phone can’t be opened by guessing.
Your 12-word recovery phrase is the only other way in, and the only way onto a new iPhone.
There is no OwlVault server, account or analytics. We can’t see, recover or hand over your vault.
OwlVault can’t protect a vault that is open on an iPhone in someone else’s hands, or an iPhone with malware.

How your files are encrypted

Each vault has its own random 256-bit master key, and every item in it — a photo, a video, a document scan, a note — gets its own key. The content is encrypted with AES-256-GCM in pieces of 1 MiB. GCM detects any change to an encrypted piece, and the pieces are bound together so that cutting some off or putting them in a different order is detected too.

OwlVault uses only the cryptography built into iOS (Apple’s CryptoKit and CommonCrypto). It doesn’t ship its own homemade encryption.

Your pattern or PIN, plus this iPhone

You open a vault with a pattern on a 4×4 grid (at least 6 dots) or a PIN of 6 to 10 digits. OwlVault turns that secret into a key with PBKDF2, a deliberately slow function (600,000 rounds), and then combines it with a 256-bit device key. The device key is stored in the iOS Keychain as “this device only”: it doesn’t sync to iCloud and never leaves your iPhone.

In practice:

A copy of your vault files without your iPhone can’t be opened by trying patterns or PINs, because the device key is missing.
On your iPhone, every guess is slowed down by those 600,000 rounds, and after 5 wrong attempts you have to wait before trying again.

Vaults nobody can count

The unlock screen never lists your vaults. A wrong pattern looks exactly the same as a vault that doesn’t exist: “Nothing here.” Someone holding your unlocked iPhone can’t tell from OwlVault how many vaults you have.

That’s also why Face ID works for at most one vault. If Face ID could open several, using it would reveal that the others exist. Face ID is optional; its key sits in the Keychain behind biometric access, on this iPhone only.

The recovery phrase

OwlVault gives you a 12-word recovery phrase (the BIP39 standard). It protects the vault’s master key separately from your pattern or PIN, again with 600,000 rounds of PBKDF2.

It’s shown only once. Write it down on paper.
It’s the only way to open your vault on a new iPhone, where the old device key doesn’t exist.
We don’t store it and can’t recover it.
Lost the paper? While a vault is open, you can create a new phrase in Settings, confirming with your pattern or PIN. The old phrase stops working, but backup files you exported earlier still need the old one.

Your vault files can be part of your iPhone’s iCloud or computer backup, and you can export an encrypted .owlbackup file. Both stay encrypted, and on another iPhone both need the recovery phrase. How moving to a new iPhone works.

On your iPhone

Vault files use iOS Complete Protection: they can’t be read at all while your iPhone is locked, even by OwlVault.
OwlVault locks as soon as it goes to the background. You can change this in the app’s settings.
In the app switcher, OwlVault’s screen is blurred.
Files that are decrypted for viewing are temporary and get deleted.
Expiry reminders are local notifications with generic text (“A document in OwlVault expires soon”). They never name the document.

No server, no account, no analytics

There’s no OwlVault account and no OwlVault server. Your vault never passes through us, so there’s nothing on our side to leak, lose or hand over, and no password reset that someone else could abuse.

The only data that leaves your iPhone because of OwlVault is what purchases need: Apple handles the payment, and RevenueCat records your purchase status with an anonymous ID so that Pro works. Neither receives your vault contents. Details are in the privacy policy.

What OwlVault doesn’t protect against

Encryption protects files on the device. It has limits, and you should know them before you rely on it.

An open vault in someone else’s hands. While a vault is open, whoever holds the iPhone sees what you see. Anyone who has your iPhone and knows a vault’s pattern or PIN can open that vault.
Malware or a compromised iPhone. Software that controls your phone can read the screen while a vault is open. Keep iOS up to date and don’t install profiles or apps you don’t trust.
Someone watching you unlock. A pattern or PIN can be learned by looking over your shoulder.
A short PIN on your own iPhone. A 6-digit PIN has a million combinations. That’s enough only because guessing is slow and has to happen on your iPhone. A longer PIN or pattern is stronger.
A forgotten pattern or PIN plus a lost recovery phrase. Then nobody can open the vault — not even us. No back door also means no reset.
Copies outside the vault. Originals left in Photos or in Recently Deleted, photos synced by iCloud Photos, or files you sent in a chat aren’t protected by OwlVault.

Technical details

For security professionals, the design in one place.

Vault key: A random 256-bit master key for each vault. Every item has its own key.
Encryption: AES-256-GCM, applied in 1 MiB chunks, with protection against chunks being truncated or reordered.
Unlock secret: A pattern on a 4×4 grid (at least 6 dots) or a PIN of 6–10 digits.
Key derivation: PBKDF2-HMAC-SHA256 with 600,000 iterations, combined with the device key using HKDF-SHA256.
Device key: 256 bits, stored in the iOS Keychain as “this device only”: not synced, never leaves the iPhone.
Guessing limits: Only possible on the iPhone itself, slowed by the key derivation and a waiting period after 5 wrong attempts.
Recovery phrase: 12 words (BIP39, 128 bits of entropy). It protects the master key separately, again with PBKDF2 and 600,000 iterations. Shown once; not stored by us.
File protection: Vault files use iOS NSFileProtectionComplete: unreadable while the iPhone is locked.
Face ID: Optional, for at most one vault. Its key sits in the Keychain behind biometric access, on this device only.
App state: Locks when it goes to the background (configurable), is blurred in the app switcher, and deletes temporarily decrypted files.
Notifications: Expiry reminders are local and always generic.
Cryptography: Only what is built into iOS: CryptoKit and CommonCrypto.
Network: No OwlVault server, no account, no analytics. Purchases go through Apple, recorded by RevenueCat with an anonymous ID.

Report a security problem

If you think you’ve found a security issue in OwlVault or on this website, email support@owlvault.app with “Security” in the subject. Please don’t include anyone’s vault contents or recovery phrase.

This page describes the design of OwlVault 1.0. Last updated: October 22, 2026.