How ScanLocker protects what you keep in it.
This page states what the application does, in the terms an engineer would use to check it.
Encryption at rest
Every item you save is sealed with 256-bit Advanced Encryption Standard in Galois/Counter Mode, through Apple's CryptoKit framework. Galois/Counter Mode authenticates as well as encrypts, so the application detects a modified file and refuses it. The sealing happens on the way to disk, and the plaintext bytes are never written.
Where the keys live
The 256-bit key is generated on your iPhone and stored in that iPhone's Keychain with the attribute that Apple names WhenUnlockedThisDeviceOnly. That attribute means the key is readable only while the device is unlocked, it never syncs to iCloud, and it never restores onto a second device. Zirkon LLC holds no copy of it.
The key for the Locker tab is wrapped under a key agreed with the Secure Enclave, so opening it requires that particular iPhone's hardware.
The Locker Page Pin
The pin you set for the Locker tab is put through PBKDF2 with a 16-byte random salt, and only the resulting hash and the salt are stored. Reading the Keychain gives an attacker the hash, and the pin itself has to be searched for.
The files on disk
Sealed files are written with iOS Complete Data Protection, which keeps them unreadable while the iPhone is locked. They are also excluded from device backup, which means they are absent from an iCloud or Finder backup. That is a deliberate choice and it has a consequence you should plan for: a restored iPhone arrives empty of them.
The network
The application opens no internet connection of its own. It carries no account, no analytics, no advertising, and no crash reporting, and it embeds no third-party software development kit. The Security tab watches the connections this process makes and tells you what it has seen, so the claim is one you can check on your own device.
What leaves, and when
A copy leaves the iPhone when you start one of three actions.
- Sending an item through the iOS Share Sheet, to whatever destination you pick.
- Saving a picture into the Photos library.
- Transferring your contents to a second iPhone running ScanLocker.
The Security tab notes the time and the kind of each one. The note never carries what the item said. Whatever receives a copy then holds it under its own rules, beyond the reach of this application.
The transfer between two iPhones
Two devices running ScanLocker agree a key over ephemeral Curve25519 key agreement, fresh for that transfer, and the payload crosses sealed under AES-GCM with that key. The next transfer agrees a new one.
The cryptography we use
ScanLocker uses standard, published algorithms as Apple's platform supplies them: AES-256-GCM, Curve25519, PBKDF2, and the iOS Keychain and Secure Enclave. We have written no cipher of our own, and the application depends on no cryptographic library outside Apple's.
Reporting a vulnerability
Write to security@zirkon.services with a security finding. Tell us the device, the iOS version, and the steps that reproduce it. We answer every such message, we will tell you what we intend to do and when, and we credit the reporter in the release notes when the reporter wants that. The same contact is published in machine-readable form at /.well-known/security.txt.