A Study On Chaos Based Stream Cipher Algorithm

With the rapid development of information technology, the security of sensitive information attracts more and more people's attention. Then information security becomes the common focus of current research. In that case, based on the features of initial value sensitivity, parameter sensitivity and random sensitivity, the chaotic system is widely used in information security communication.The chaotic stream is a crucial part of the chaotic cryptography. The chaotic map is an important component of the chaotic stream. In chaotic cryptography, designing a superior performance chaotic map is one of the important ways to improve the performance of encryption algorithm. This paper finds that although logistic map owns some advantages from chaotic system, but it still has some inherent problem from the view of cryptography, such as uneven density probability distribution and weak egodicity, etc. Combining chaotic technologies and research on cryptography, the main idea of this paper is as follow:1) Basic knowledge of chaos theory, chaotic map and chaotic steam cipher is studied. Then state-of-the-art and the worthy research direction of chaos-based chaotic map and chaotic steam cipher algorithm are analysed in detail.2) In order to overcome the disadvantage of logistic map in designing chaos-based cipher, the piecewise logistic map(PLM) is presented. Some properties related to cryptography of the PLM, such as ergodicity, Lyapunov exponent and bifurcation, are analyzed and compared with the logistic map. From the view of cryptography, the PLM owns better properties than the logistic map. Furthermore, to improve the density probability distribution of the PLM, the PLM with variable control parameter is suggested.3) According to the PLM, a novel stream cipher algorithm based on PLM is proposed. Then statistical testing, security, correlation evaluation, efficiency, etc are analyzed. These simulation results show that this algorithm not only overcomes the weak security of simple map, but also is a simple and efficient algorithm.4) A novel spatiotemporal chaotic map(PLCML) is suggested based on the PLM, which is an enhanced version of logistic map. Compared with the LCML, the PLCML has bigger Lyapunov exponent. To achieving the more uniform density probability distribution, the PLCML with variable coupling parameter is proposed, which is more suitable to design chaos-base encryption scheme. Then in order to confirm the academic value of PLCML, a new stream cipher algorithm based on PLCML is proposed. Theory analysis and simulation results show that this algorithm has better properties, such as statistical testing, security, correlation evaluation, efficiency, etc. so the algorithm overcomes the weak of large amount of calculation about the complex chaotic map, and has high security.