December 2012
Intermediate to advanced
834 pages
27h
English
Content preview from iOS 6 Programming CookbookBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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12.6. Securing Files on Disk
Problem
You want to make sure that the files that you are working with on disk are locked and encrypted when the iOS device is locked, and not accessible by an attacker.
Solution
Create your file using the createFileAtPath:contents:attributes: instance
method or your folders using the createDirectoryAtPath:withIntermediateDirectories:attributes:error: instance method of the
NSFileManager and use the
NSFileProtectionKey key in the
attributes dictionary with one of the following values:
NSFileProtectionCompleteUnlessOpenThe file will be encrypted on disk and will be accessible by your app only after the user has unlocked the device. The user can then lock the device back, but while you have the handle to the file, you can continue to read from and write to the file.
NSFileProtectionCompleteThe file is encrypted on disk and is not accessible by your app unless the user unlocks the device. If you have a handle to the file when the device is unlocked, you will not be able to read from or write to the file if the user decides to lock the device again.
NSFileProtectionCompleteUntilFirstUserAuthenticationThe file is encrypted on disk and you can read from it or write to it only after the user has at least unlocked the device once. After that one-time unlocking, you can read from and write to the file. The user can lock the device, but that won’t affect you and your file handle.
iOS uses the passcode that the user sets for her device as a seed to the encryption applied ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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