ASIdentifierManager
NSString *advertisingIdentifier = [[[ASIdentifierManager sharedManager] advertisingIdentifier] UUIDString]; identifierForVendor
NSString *identifierForVendor = [[[UIDevice currentDevice] identifierForVendor] UUIDString];identifier hashed from MAC Address
NSString *uniqueGlobalDeviceIdentifier = [[UIDevice currentDevice] uniqueGlobalDeviceIdentifier];