Cube attack on reduced-round Enhanced-Bivium

Trivium is a notable light-weight synchronous stream cipher submitted to the European eSTREAM project in April 2005. Enhanced-Bivium is a reduced version of Trivium which is suitable for RFID system. In this paper, the security of Enhanced-Bivium is concerned under cube attack, which is one of the best known attack on the reduced round Trivium proposed by Dinur and Shamir at EUROCRYPT 09. Trivium with 576 initialization rounds can be recovered in 2 11 . We show that it is difficult to search the cubes of Enhanced-Bivium with the same rounds and after 464 rounds the attack complexity is reduced to 2 55 . Therefore, comparing with Trivium, Enhanced-Bivium has a better performance under cube attack.