Some Primitives Based on Jumping LFSRs with Determined Period
Mahdi Sadjadieh, Arash Mirzaei, Mohammad Dakhilalian · 2016
Linear feedback shift registers (LFSRs) are used in many stream ciphers because of their maximal period and good statistical prop- erties. Due to the linearity of the LFSR, its output cannot be directly used as the keystream. Dierent methods have been proposed to intro- duce the nonlinearity to the LFSR output. Irregular clocking is one of the methods to do this but the stream ciphers based on this method, are vulnerable to the side-channel attacks. In addition, the generation rate of the irregular clocked LFSRs is less than the corresponding regular ones. Jumping is a method of irregular clocking for LFSRs which may have non of the mentioned aws but its output period cannot be determined. In this paper, using the jumping LFSRs, some new primitives will be proposed. Structures of the new primitives have the determined lower bound of period and the resistance against the side-channel attacks. In some of the proposed structures, the lower bound of period can be de- termined without knowledge of the jump index. These structures are applicable when the calculation of the jump index is infeasible. The pro- posed structures can be used as primitives to design the software oriented and hardware oriented stream ciphers.