title: How does John the Ripper work?
body: <p>I am familiar with John the Ripper, nevertheless, I haven't found a source where I can familiarize myself with the theory behind the program. I know that by studying the code I can get to understand how it works, yet I would like to read something where the techinques used by the program are studied in deep. Can anybody give some suggestions? 
  Just to get it straight: I would like somebody to point out a reference where I can find the "theory" behind password cracking.
  Thanks.</p>