title: In Rails, can the secret_key_base be updated without losing previously signed data?
body: <p>In Rails 4.x the <code>secret_key_base</code> is used to sign the session cookie and also any other signed cookies created by calling <code>cookies.signed</code>.</p>
  
  <p>I'd like to update/cycle/roll this <code>secret_key_base</code>, but without losing access to all of the previously signed cookies (I don't mind losing the sessions). Is it possible to do this?</p>
  
  <p>Ideally I'd like something like:</p>
  
  <ol>
  <li>Add new <code>secret_key_base</code>.</li>
  <li>Use both the old and new <code>secret_key_base</code>'s alongside each other over a period of time, so that cookies signed using the older key can be re-signed with the newer key.</li>
  <li>Remove the old <code>secret_key_base</code>.</li>
  </ol>
  
  <p>I know there was similar functionality for upgrading from using a <code>secret_token</code> to a <code>secret_key_base</code>. Is there a way to achieve this using Rails?</p>