Distinguishing Attack on CSA

Kai Zhang and Jie Guan

Zhengzhou Information Science and Technology Institute, China

Abstract: Common Scrambling Algorithm (CSA) has been used to encrypt European cable digital television signals since 1994. Although the key size of CSA is small, up to now, there haven’t any effective crypto results which can break the algorithm totally. Based on the idea of slide resynchronization attack, a distinguishing attack which can distinguish the keystream of the stream cipher from a purely random sequence with computational complexity of O (2¹⁵) is proposed. According to the distinguishing attack, the 64 bit initial key can be recovered with computational complexity of O (2⁵⁵).

Keywords: DVB-CSA, distinguishing attack, slide resynchronization attack, hybrid cipher.

Received August 31, 2012; accepted February 23, 2014