Hi, My app offers a free-trial of a paid service for new users. I know that in-app purchase has a built-in trial system. But I think some users who are not well knowledgeable about in-app purchase will be reluctant to tap on the "buy" button unless they are ready to buy. I thought of providing a registration and login mechanism but still it would be much cleaner if I can programmatically identify devices uniquely, even after deleting the app and re-installing it. Is there any way to do this on iOS 7?