title: Authenticate by Device with Firebase
body: <p>Sorry if this is a simple question.. but I can't seem to find a good answer for this.</p>
  
  <p>I want to implement an anonymous login, where the user is simply logged in by their device. I am guessing that devices across iOS and Android don't have unique IDs.. so I guess I would have to manually generate an ID, and then see if its already in use, and then if it is regeneerate. Is there a solution to this sort of thing? my solution seems really hacky...</p>
  
  <p>My current idea, logic wise is:</p>
  
  <ul>
  <li>Generate Unique ID</li>
  <li>Query database to see if Unique ID is already in use</li>
  <li>If it is repeat first two steps</li>
  <li>If not push up</li>
  </ul>
  
  <p>I need to be able to track what Device has pushed what information to the database, but I don't want to make users have to sign in or provide any information.</p>