Study Of Encryption Algorithm Based On Mixed Cellular Automation

How to improve computing efficiency of encryption system on the base of enhances its safety have always been problems concerned by scholars.For cellular automation,as a parallel dynamics system with high discretion of time-space variables,its dynamics behaviors have various complex characteristics,and these behaviors are rightly indispensable for encryption system.However,three-neighbor cellular automation only has 256 rules with small secret-key space,so rules that can be used for encryption are limited,so this paper solved this problem by enlarging number of neighbors of cellular automation and expanding the dimension.The greater radius of neighborhood of cellular automation is,the greater secret-key space will be.However,as radius of neighborhood enlarges,the number of its rules will present exponential increase,which increases analysis difficulty.Although number of secret-key spaces of five-neighbor cellular automation reaches over 2³²,it is of enormous workload for analysis.Four-neighbor cellular automation is a kind of asymmetric neighboring structure which breaks through pattern of previous symmetric neighboring structure,so it is a breakthrough in structure.This paper conducted meticulous research and classification of 1D four-neighbor cellular automation through DDLAB system and selected some encryption rules with good dynamic characteristics and chaotic behaviors.In the meantime,this paper used three-neighbor reversible cellular automation rules to obtain 2D cellular automation rules with reversible behaviors in computations of different directions and expanded 1D space into 2D plane,which not only enlarged secret-key space of cellular automation but also unproved spatial complexity of the algorithm.Besides,it adopted a now Y-type structure which enlarged information diffusion degree of 2D cellular automation on the condition that computing efficiency was guaranteed;finally it expanded 2D model into 3D space through second-order structure,which further enlarged secret-key space and improved evolutionary complexity of the algorithm.This paper proposed a block cipher method by combining 1D 2-state four-neighbor cellular automation and Y-type second-order reversible cellular automation.This method adopted second-order structural encryption method,used 1D four-neighbor cellular automation with chaotic characteristics to generate pseudo random sequence(C^-1)as initial structure of plain text（C⁰）in encryption layered structure,and then conducted iteration encryption of plain text in form of layered structure through Y-type second-order reversible2 D cellular automation.This method overcome structural limitation of 1D cellular automation,improved secret key space and enhanced algorithm complexity.In the meantime,for application of Y-type structure,on the condition that encryption efficiency was ensured,it made interaction between information reach the maximum.Experiment showed that this method was of great secret key space,it satisfied avalanche effect and had initial value sensitivity and ideal information entropy;besides,it could effectively resist differential attack.