Is additional encryption required on iOS when storing files with .completeFileProtection?

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On iOS, if a file is stored using .completeFileProtection it is encrypted by the OS and only accessible when the device is unlocked according to the documentation.

In another app I looked at, the developers had encrypted all files manually and then stored the symmetric key in the device keychain.

I'm wondering if there really is any security benefit from doing that rather than using the built in .completeFileProtection? Or would it ever make sense to do both?

swift encryption ios
1 Answers

To my understanding, with an additional encryption, files will remain encrypted even when device is unlocked.

Also, file will be decrypted only when app needs to read it. With this approach, the app could decrypt and read files even in background mode — if we don't change the level of data protection, since default is NSFileProtectionCompleteUntilFirstUserAuthentication.

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