title: Unique device fingerprint
body: <p>How do we generate a unique device fingerprint, for each and every android device?</p>
  
  <p>Criteria,</p>
  
  <ol>
  <li>It should be unique for each and every device.</li>
  <li>Should not change when user upgrades the OS.</li>
  <li>Should not be predictable, for security reasons.</li>
  </ol>
  
  <p>I have already tried various permutation and combination. I see that generating a random, and storing is the easiest alternative. 
   I am not very comfortable with the "storing" part.</p>