Dissertation
Dissertation > Industrial Technology > Automation technology,computer technology > Computing technology,computer technology > General issues > Security and confidentiality > Encryption and decryption

The Generation of Chaotic PN Series and Its Application in Image and Video Encryption

Author ZuoJianZheng
Tutor WangGuangYi
School Hangzhou University of Electronic Science and Technology
Course Circuits and Systems
Keywords Chaos Fractional Digital DSP Image Video
CLC TP309.7
Type Master's thesis
Year 2009
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With the continuous progress of science and technology, information technology has penetrated into every aspect of people’s lives. Information security has attracted more and more attention, and so how to strengthen information privacy becomes an urgent problem. Because of chaotic signal inherent in non-cycle, wide spectrum and sensitivity to the initial values and so on, it makes chaos has good application prospects in the information encryption. In order to enhance the confidentiality and practicality of chaotic information encryption, the following two aspects are needed to do first: On the one hand, to improve the performance of chaos; on the other hand, to improve the performance of encryption system. Based on this background, the two problems are studied and a series of new results are gotten. The main contributions of this paper are as follows:(1) A variety of chaotic sequence generation methods are systematically studied. The generation of chaotic sequence is the premise and the key technology of chaos information encryption. From the original analog circuitry and now the digital system, a series of new problems appear with the continuous progress. This paper summarizes the previous research, systematic introduce a variety of chaotic sequence generation methods, including analog circuits, FPGA, LabVIEW, DSP, etc. Through the analysis and comparison, it plays an important reference for the continue in-depth study.(2) A new chaotic system is designed. Considering the chaotic secure communication in engineering practice, it is necessary to construct a large number of chaotic systems. In order to design the good performance of chaotic systems, Based on the noted Sprott system, a new chaotic system was constructed. Dynamical behaviors of the new system are analysied, including bifurcation analysis and Lyapunov exponents’spectrum. Besides, the analog circuit of the new system is also designed. Comparing the experiment with the simulation, it is shown that the attractors of the new chaos are the same, which also verifies the nature of chaotic system.(3) A new fractional order chaotic system is designed. This paper proposes a new fractional chaotic system and introduces two analytical methods of fractional calculus. Numerical simulation adopts a method to solve fractional calculus in time domain, Circuit simulation adopts the method of conversion between time domain and frequency domain. The simulation results show that the minimum order of the system is 2.31 when the system exhibits chaotic behaviors. Then a fractional chaotic oscillating circuit for implementing the system is designed and simulated. Circuit simulation results show a good qualitative agreement between the circuit and numerical simulations. The feasibility of the signal generator is confirmed.The fractional chaotic system displays physical phenomena better than the integer-order chaotic system. A definite fractional order chaotic system shows different state in different values. So the fractional chaotic system has a larger key space and less likely to be replicated.(4) It is the first time by using digital system to produce fractional order chaotic sequence. Extensive research of the fractional order chaotic system is in the recent decades, the current study which is in theory stage. In this paper, by using LabVIEW and other digital systems, the real fractional order chaotic signals are obtained. Firstly the equations of chaos are calculated by MATLAB through the connection of LabVIEW and MATLAB. Then the front panel is designed on the LabVIEW platform, parameter can be regulated in the front panel. Finally the fractional order chaotic sequence is outputted by data acquisition card. Digital system can do the same parameter and easy to control.(5) Through DSP platform, by using fractional chaos PN sequence, the real-time encryption/ decryption of images and videos are successful implemented. The PN sequence previously generated from the fractional chaotic order system are applied as the key stream in image and video encryption, that is, to XOR the PN sequence and individual pixel in the frames of images or videos.The fractional order chaotic system has a larger key space, so the security is high. The DSP has Very high computation speed, by using DSP, this Encryption system can meet the requirement of real-time. This encryption method can overcome the shortcomings of slow and easily to be cracked in the traditional encryption, so it has broad prospects of application.

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