Data Protection Improvements

Introduced in iOS 4.0, data protection lets you store application and user data files on disk in an encrypted format so that they can be accessed only when a user’s device is unlocked. In iOS 5.0, you now have more flexibility regarding when your application can access protected files. Using the NSFileProtectionCompleteUnlessOpen option, your application can access a file while the device is unlocked and, if you keep the file open, continue to access that file after the user locks the device. Using the NSFileProtectionCompleteUntilFirstUserAuthentication option, your application cannot access the file while the device is booting or until the user unlocks the device. After the user unlocks the device for the first time, you can access the file even if the user subsequently locks the device again. You should protect files as soon as possible after creating them.