title: How good is SecRandomCopyBytes?
body: <p>I'm principally interested in the implementation of <code>SecRandomCopyBytes</code> on <strong>iOS</strong>, if it differs from the OS X implementation. (I would presume that it does, since a mobile device has more and more readily available sources of entropy than a desktop computer.)</p>
  
  <p>Does anyone have information on:</p>
  
  <ol>
  <li>Where SecRandomCopyBytes gets entropy from?</li>
  <li>What rate it can generate good random numbers?</li>
  <li>Will it block, or fail immediately if not enough entropy is available?</li>
  <li>Is it FIPS 140-2 compliant, or has it been included in any other official certification?</li>
  </ol>
  
  <p>The documentation does not cover these points.</p>
  
  <p>I've only been able to find hear-say comments that it uses information from radios, the compass, accelerometers and other sources, but no quotes from people actually representing Apple.</p>