Data Protection Classes

Class A	Complete Protection	NSFileProtectionComplete	Class Key protected with a key derived from the passcode + device UID. When the device locks the class key is discarded. All data is inaccessible until the user authenticate again.
Class B	Protected Unless Open	NSFileProtectionCompleteUnlessOpen	Useful if the app needs to write data while the device is locked
Class C (Default)	Protected Until First User Authentication	NSFileProtectionCompleteUntilFirstUserAuthentication	Sames as complete, except the decrypted class key isn't removed from memory when the device is locked. This is default for all 3rd party apps.
Class D	No Protection	NSFileProtectionNone	Class key is only protected with the UID . Data is still encrypted though.

Keychain Data Protection Classes

Availability	File Data Protection	Keychain Data Protection	Notes
When Unlocked (Default)	NSFileProtectionComplete	KSecAttrAccessibleWhenUnlocked	Keychain item is only accessible when the device is unlocked
While Locked	NsFileProtectionCompleteUnlessOpen	N/A
After First Unlock	NSFileProtectionCompleteUntilFirstUserAuthentication	KSecAttrAccessibleAfterFristUnlock	Item is accessible after the first unlock from boot
Always	NSFileProtectionNone	KSecAttrAccessibleAlways	The item is always accessible
Passcode Enabled	N/A	KSecAttrAccessibleWhenPasscodeSetThisDeviceOnly	If the keychain is copied as part of a backup it won't work on another device as it is protected by the device UID