Multi-pass Fast Correlation Attack on Stream Ciphers

Abstract

Fast correlation attacks are one of the most important attacks against stream ciphers. Previous results on this topic mainly regard the initial state of the involved linear feedback shift register as a whole and only use one sort of parity-checks to decode the corresponding linear code. In this paper we propose a new kind of attack, called multi-pass fast correlation attack, on stream ciphers. This kind of attack can make good use of different kinds of parity-checks without increasing the asymptotic complexity and restore the initial state part-by-part. It has no restriction on the weight of the underlying linear feedback shift register and both theoretical analysis and simulation results show that it is more efficient than all the previously known fast correlation attacks.