title: How to identify unique users without using a login system (iOS)
body: <p>I need to have a way to identify the users of my app, but without having a login system.</p>
  
  <p>I looked into the UUID which gives me part of an answer to my problem, but as it's not the real  UDID, it's not "really unique" : if the user re-installs the app, he gets a new UUID, and this can't work for me.</p>
  
  <p>Is there a way I can get the device serial number or something unique like that? Anything of the sort that i could get from the device without having the user to fill any fields.</p>