Research On Light Weight Chaotic Block Cipher

As an important branch of the symmetric cryptosystem, block cipher plays an important role in the data encryption of information and network security, at the same time, it is also widely employed in the message authentication, key management, and other confidential fields. With the rise of the Internet of Things and the widely application of the smart card, the lightweight block cipher which works in the limited resources environment has become the hot topics of research. Combined with the chaotic system, this thesis mainly researches on the design, analysis, etc of the lightweight chaotic block cipher. The following aspects are mainly included:(1)Some basic knowledge of the design and analysis theory of block cipher algorithms and chaotic maps are summarized. In the first, the general mathematical model and some basic design principles of block cipher are introduced. Secondly, five working modes and some common security analysis methods of block cipher including the difference and the linear analysis are reviewed. Finally, the relationship between the chaotic system and the modern cryptography is illustrated, some kinds of common models and discretization methods of the chaotic maps are also listed.(2)Combined with the classic structure of the modern block cipher and the chaotic system, this thesis proposes a chaotic block cipher algorithm based on the generalized Feistel structure. To improve the security of the algorithm, two different round functions are adopted in the same round. The two round functions are redesigned with simple structure, which enable the algorithm to obtain desirable confusion and diffusion with less computation. At the same time, a mixing transformation based on discrete two- dimensional cat map is adopted between different branches to speed up the spread of local data change. Theoretical and experimental results show that the algorithm is sensitive to the change of keys and has good confusion and diffusion.(3)Considering the branch of diffusion layer and mixing transformation in the above section did not achieve the optimal situation, we propose a new design method of diffusion layer based on cyclic shift and XOR, and improve the key scheduling algorithm and the mixing transformation, statistical test method is also used to assess the confusion and diffusion effect. Meanwhile, the ability of algorithm resisting differential and linear attack is evaluated. Furthermore, the algorithm is simulated on the FPGA platform and the hardware resource occupancy of this algorithm is also estimated. It turns out that the proposed algorithm is more secure but less resources involved, which is suitable for the application in resource limited environment.Finally, the work of the thesis is summarized comprehensively, and the future research work is prospected.