What on-device encryption would mean in a SeraShield vault

Start with what somebody might actually see

Consider a scan of a lease. If the file is encrypted but its thumbnail or filename appears in a readable cache, a sensitive part of the scan may still be exposed. A useful design must account for the imported file, the index that lists it, any generated thumbnail, and temporary copies used for viewing or sharing.

iOS already protects files through its Data Protection system, with different access rules for different file classes. An application vault could add its own layer by encrypting selected material before writing it to permanent vault storage. The design question is where the file is readable during normal use and what remains readable afterward.

Decide when the key can be used

A candidate design would use an established authenticated encryption API, such as AES-GCM in Apple’s CryptoKit, to check the integrity of encrypted contents as well as conceal them. A vetted key-management design would still be needed, including how keys are generated and protected, how nonce reuse is prevented, and what happens when storage formats change.

Apple’s Keychain controls can restrict access based on device state and user presence. That makes it possible to explore a vault that requires authentication after you hand over an unlocked phone. The choice of fallback matters. If the device passcode is an accepted fallback, a person who knows it may have a path to unlock. Tying a key more tightly to one device can make transfer and recovery harder.

Evidence we would want before a release

We would define the intended protection against casual browsing, possession of a locked phone, and access to a copied backup separately. Each case needs its own tests. A phone under someone else’s control or an export that has left the vault introduces additional risks.

1. Inspect stored files, thumbnails, logs, and app previews after import, lock, force-quit, and reboot.
2. Tamper with an encrypted sample and check that the app rejects it without displaying partial content.
3. Test authentication fallback, interrupted import, key changes, and restoration on a replacement device.
4. Document which files leave the vault when you export or share them.