title: Why should checking a wrong password take longer than checking the right one?
body: <p>This question has always troubled me.</p>
  
  <p>On Linux, when asked for a password, if your input is the correct one, it checks right away, with almost no delay. But, on the other hand, if you type the wrong password, it takes longer to check. Why is that?</p>
  
  <p>I observed this in all <a href="http://en.wikipedia.org/wiki/Linux_distribution" rel="noreferrer">Linux distributions</a> I've ever tried.</p>