A Study On Chaos Based S-box Construct Method And Its Encryption Algorithm

With the development and popularization of information technologies, the securityof sensitive information attracts more and more people’s attention. Thus, informationbecomes the common focus of current research, and the research on it has significantpractical and academic value.Substitution box (S-box) is an important component in block cipher system, and itis widely used in standard encryption algorithms such as: DES and AES. Thus theresearch on S-box is a very important area in the research of cryptography. Chaos hascome excellent properties, such as: randomness, sensitivity to initial value and controlparameter and nonlinearity, and has some relationships with cryptograph, which bringsa new direction of researches on related fields of cryptography.Combining chaotic technologies and research on cryptography, the accomplishedtasks of this paper is shown as below:(1) Basic knowledge of chaos theory, cryptography and image encryption isintroduced. Moreover, state-of-the-art and the worthy research direction of chaos-basedS-box construction method and image encryption algorithm are analysed in detail.(2) The problems of current research on improving the nonlinearity of S-box aregiven. An S-box construct method combining with chaotic map and hill-climbingalgorithm is introduced. Theory analysis and simulation results show that this algorithmcan efficiently obtain S-boxes with high nonlinearity.(3) Shortcomings of S-box construct algorithm based on chaos and geneticalgorithm are analyzed. The properties of truth table of S-box is introduced. At the sametime, a theory used to check bijective property of S-box in the construct process isproposed. An optimization method based on the theory of improving nonlinearity ofS-box is given which can avoid local optimal influences on the result.(4) A method used to permute the image on bit value is introduced. And multiS-boxes are engaged to encode pixel-values of image and expand key stream. Moreover,a spatiotemporal-based image encryption algorithm is shown. The simulation resultsprove that it can effictively encrypt the image and resist classic attacks on block cipher.