Serpent was widely viewed as a more traditional approach to security than the other AES finalists choosing a larger security margin : the designers estimated 16 rounds to be sufficient against known types of attack , but specified 32 rounds as insurance against future progress in cryptanalysis . Serpent was widely viewed as taking a more conservative approach to security than the other AES finalists , opting for a larger security margin : the designers deemed 16 rounds to be sufficient against known types of attack , but specified 32 rounds as insurance against future discoveries in cryptanalysis .