title: Uniquely identifying an iOS user
body: <p>I'd like to create a user account on the server for new users of an app, but I'd also like to not ask the user to type in anything. Ideally, I'd like this to be automatic, like with Game Center.</p>
  
  <p>But I'm wondering if it's possible. Is there anything I can use to uniquely identify the user? It's highly unlikely that I can find out the user's Apple ID. Also, the device ID uniquely identifies the device, not the user, so it would be useless if the user has more devices...</p>
  
  <p>Is there anything else I can use?</p>
  
  <p>About privacy - I don't want to find out anything behind the user's back. I have absolutely no problem with asking the user for access to their information (and if there is an API that grants me this information, it would be great if the API asks this itself). As Steve Jobs himself said, this is what privacy is all about - forcing apps to ask the user for permission before doing anything with their private data.</p>