Exclude items from iOS backup and restore

1. File and folder
application can apply property NSURLIsExcludedFromBackupKey to exclude file or folder item from itune/icloud backup and restore.

 NSURL* URL= [NSURL fileURLWithPath: filePathString];

 NSError *error = nil;
 BOOL success = [URL setResourceValue: [NSNumber numberWithBool: YES]
                                  forKey: NSURLIsExcludedFromBackupKey error: &error];


2. NSUserDefault
NSUserDefault items are always included in the backup and restore and cannot be excluded.


3. KeyChain
The following three attributes can be used to prevent the keychain items be restored to other devices. The values can be set as kSecAttrAccessible attribute in the secItemAdd method

Sample:
[dict setObject:kSecAttrAccessibleAlwaysThisDeviceOnly forKey:kSecAttrAccessible];

kSecAttrAccessibleWhenUnlockedThisDeviceOnly
Keychain item is accessible only after the device is unlocked and the item cannot be migrated between devices.
kSecAttrAccessibleAfterFirstUnlockThisDeviceOnly
Keychain item is accessible after the first unlock of the device and the item cannot be migrated between devices.
kSecAttrAccessibleAlwaysThisDeviceOnly
Keychain item is accessible even the device is locked and the item cannot be migrated between devices.