File protection extends beyond the main database. Previews, temporary files and sharing copies also form part of an iOS application's data surface.
Evaluation approach
Examine when a file is opened, how long its contents remain in memory and whether it enters backups. Keychain and file protection serve different data types.
Application example
Use the workflow to assess whether a sensitive report must remain accessible after the screen locks.
Limits and considerations
Disk encryption does not automatically protect live application memory or an improperly shared file.
What changes when the device locks?
A file's protection class affects the device states in which it is accessible. A file needed by a background task and a sensitive file opened only through user interaction have different requirements. Choose according to actual use.
Test locked devices, restarts and background work together. Check that an access failure does not cause the application to create a less protected copy. Complement protection-class choices with data minimization and server authorization.
Checks and decisions
- Classify files
- Test lock states
- Clean up temporary files
Observe every copy when testing changes in device lock state.
Sources
The primary references above provide the technical basis. Example workflows and evaluation suggestions are this publication’s explanations, not independent test results for a particular product.