Source : WordNet®

cryptanalysis
     n : the science of analyzing and deciphering codes and ciphers
         and cryptograms [syn: {cryptanalytics}, {cryptography}, {cryptology}]

Source : Free On-Line Dictionary of Computing

cryptanalysis
     
        The branch of {cryptography} concerned with decoding encrypted
        messages when you're not supposed to be able to.
     
        (1994-12-06)