You draw a pattern on a 5x5 grid. ArkWarden derives a 256-bit encryption key from that pattern and uses the key to encrypt every file in your vault. There is no password to remember and no PIN protecting already-readable files. The security comes from the cryptography used for key derivation and encryption.
Most vault apps use your input to unlock files that are already stored in a readable form. ArkWarden uses your input to generate the key that encrypts and decrypts the data itself. Here is what happens between your finger and the encrypted file on disk.
Pattern
Shape you draw
Salt
Random, per vault
PBKDF2
Key derivation
256-bit key
Master key
AES-256-GCM
File encryption
You connect dots on a 5x5 grid. ArkWarden records which dots you touch and the order you touch them in. That sequence is your pattern.
The grid is intentionally large. A 5x5 grid produces billions of possible patterns, significantly more than a 6-digit iPhone passcode, which has one million combinations. More dots means more entropy, which means a harder target for guessing attacks.
ArkWarden feeds your pattern into a key derivation function. The function combines the pattern with a random salt that is unique to your vault, then runs through hundreds of thousands of hashing rounds before producing a 256-bit output.
ArkWarden uses the derived key to encrypt every file you import. Photos, videos, documents, audio. Each file is encrypted with AES-256-GCM, the same authenticated encryption used inside TLS 1.3. You can also add a second factor for another authentication step after the pattern succeeds.
Each file also gets a unique nonce, the small random value that AES needs to keep two identical files from producing the same ciphertext. Two copies of the same photo, encrypted with the same key, will still produce two completely different encrypted files on disk.
The metadata that organises your vault (category names, file titles, ordering) is encrypted with ChaCha20-Poly1305. It is the same authenticated style of encryption, tuned for the small structured data that an index needs.
When you lock the vault or close the app, the 256-bit key is released from memory. It is not written to disk. It is not cached. It is not kept for later use.
The next time you draw your pattern, ArkWarden runs the same derivation against the same salt and produces the same key. Your files decrypt. Draw a different pattern and a different key is produced. Decryption fails and the data remains unreadable.
Plenty of apps will hide your files. A much smaller number will actually encrypt them.
| A 4-digit PIN | Apple's Hidden Album | A cloud-based vault | ArkWarden | |
|---|---|---|---|---|
| What the input does | Controls access to readable files | Moves files into another album | Sends files to a server, then encrypts | Generates the encryption key itself |
| How many guesses to break it | 10,000 | Not relevant. The files are already readable. | Depends on the provider's master key | Computationally infeasible |
| Where your files live | On disk, readable | On disk, readable, just unlisted | On someone else's servers | On your device, encrypted |
| Who else can read them | Anyone with the unlock code or device access | Anyone who taps "Show Hidden Album" | The provider, plus anyone the provider gives the keys to | Nobody without your pattern |
| Recovery if you forget | Reset and lose nothing | There is nothing to recover | Account reset, often by email | A 12 or 24-word recovery phrase you control |
A PIN controls access. The data it protects is already stored in a readable form. If the access control fails, the data is immediately available. Encryption works differently. The data is stored in an encrypted form and remains unreadable until the correct key is provided.
Apple's Hidden Album and many "vault" apps move files into a private list. The underlying file data remains unchanged. Anyone with sufficient device access, or access to an unprotected backup, may still be able to read it. ArkWarden writes encrypted data to disk. Without the correct key, the contents are computationally infeasible to recover.
Cloud vaults provide synchronisation, but they also create an additional place where encrypted data is stored. The provider holds at least your encrypted files and, in some systems, the keys required to recover them. ArkWarden has no server and no account system of its own. Your encrypted files stay on your device, and if you enable the optional iCloud Backup, only you hold the key that opens it.
You do not need any of this to use ArkWarden. We include it so anyone who wants to verify what we say can match our claims against the standards that support them. See how encryption fits into the full security design.
| Part | Algorithm | Why this one |
|---|---|---|
| Key derivation from pattern | PBKDF2 |
Standardised by NIST (SP 800-132). Available natively through Apple's CryptoKit. Slow by design, which is what you want for password-style input. Configured at 600,000 iterations, the count OWASP recommends. |
| Key derivation from recovery phrase | PBKDF2 |
The phrase and the pattern both produce the same master key through the same derivation. One vault, two recovery methods. |
| File encryption | AES-256-GCM |
The authenticated encryption standard used in TLS 1.3 and IPsec. Detects tampering as part of decryption. |
| Metadata encryption | ChaCha20-Poly1305 |
The other authenticated cipher used in TLS 1.3 and WireGuard. Well suited to the small structured payloads a category index produces. |
| Salt generation | Apple's secure random source (CryptoKit) | Generated once per vault. Stored in the iOS Keychain. Unique even across two devices that share a pattern. |
| Recovery phrase | BIP-39 English wordlist, 12 or 24 words | The same wordlist used by hardware wallets. Generated using Apple's secure random source. |
Why 600,000 iterations? OWASP sets this as the recommended minimum for PBKDF2. Each unlock attempt requires that full computation. On a modern iPhone it takes under a second. For an attacker testing millions of guesses, the total computation time increases to years.
On disk: Only ciphertext. File data encrypted with AES-256-GCM. The category index encrypted with ChaCha20-Poly1305.
In the iOS Keychain: The salt for key derivation, and the master key encrypted under a key derived from your pattern (and separately encrypted under a key derived from your recovery phrase). Both items are stored so they cannot be read while the device is locked and cannot be restored to a different device.
On Apple's servers: Nothing, unless you turn on iCloud Backup. ArkWarden has no account system and no telemetry on file contents. A backup stores only an encrypted copy in your own iCloud, which is unreadable without your recovery phrase.
In memory: The decrypted master key, only while your vault is unlocked. The moment you lock the app, the reference is released and the key is no longer available in process memory.
Every iPhone supported by ArkWarden has a Secure Enclave. The iOS Keychain itself is encrypted by keys that live inside the Secure Enclave, so the master key you keep in the Keychain is ultimately protected by dedicated security hardware.
ArkWarden does not generate non-exportable Secure Enclave keys directly, because the master key has to be usable for bulk encrypt and decrypt operations, which is incompatible with non-exportable hardware keys. The Keychain path gives hardware protection without that constraint.
A large pattern space, a unique salt, and a deliberately expensive derivation process make offline guessing attacks costly and time-consuming against a single vault.
The trail of fingerprints on the screen reveals which dots were touched but not the order, direction, or connections between them. On a 5x5 grid the number of orderings consistent with any given smudge is large.
With no pattern and no recovery phrase, the on-disk data is ciphertext. There is no stored hash that directly confirms whether a guess is correct. Every guess has to attempt decryption before the attacker can evaluate the result.
ArkWarden blocks system screenshots and screen recordings across the entire app, including while you draw your pattern, while you browse your vault, and while you view a file.
ArkWarden does not send your files anywhere on its own. If you turn on iCloud Backup, only AES-256-GCM-encrypted data travels to your own iCloud, so a network attacker intercepts nothing readable.
The cryptographic claims on this page are based on published standards from recognized bodies. Each link points to the primary source.
Draw a pattern. Derive a 256-bit key. Encrypt the files you want to keep private, on your device, with no account and no server.
