New Attacks from Old Distinguishers Improved Attacks on Serpent

Serpent was originally proposed in 1998 and is one of the most studied block ciphers. In this paper we improve knowledge of its security by providing the current best attack on this cipher, which is a 12-round differential-linear attack with lower data, time and memory complexities than the best previous attacks. Our improvements are based on an improved conditional key guessing technique that exploits the properties of the Sboxes.