title: devise - encrypt the login email
body: <p>Do you know if Devise is providing a feature to store the email hashed in the database?</p>
  
  <p>If this is the case, what are the drawback using this feature?</p>
  
  <p>The two I can think of are:</p>
  
  <ul>
  <li><p>will not be obviously possible to see the email on the edit "screen" (except the [theoretical] case where the email would be stored using symmetric encryption instead of the standard one).</p></li>
  <li><p>if the salt is (for any reason) compromised and need to be changed, plan a recovery strategy would be a tough job (rather than just force the users to change the password at the next login). However, I think this is doable.</p></li>
  </ul>
  
  <p>thanks,</p>