| The progress of science and technology has been promoting the development of communication technology rapidly. In recent years, Wi-Fi service with a rapid maturation not only allowed customers to experience unprecedented convenience, but also changed the way we communicate in certain extent. Wi-Fi service has been further pushed by portable intelligent terminal. However, the security of file information becomes outstanding issue in the process of communication, including the security of image information. In addition, the occupied space is also accordingly increase, with increasing pixels of the image. Thus, how to transmit the image faster between client and server has become an urgent problem to be solved. The extreme sensitivity to initial conditions and the initial parameters, aperiodic motion and topological transitivity, ergodicity and other characteristics of chaotic systems exactly consistent with the characteristics of modern cryptography. So chaos theory has rapidly become an important topic of research in cryptography and has also provided a more effective encrypted method for communication security. LZW algorithm is a kind of general data stream compression algorithm, which has been widely applied to image compression technology. LZW algorithm has better compression effect when the predictability of the data flow is not high. Strong adaptability of the LZW algorithm has many variants and provides an ideal means for the design of compression.The main content of this research are listed as follows:(1)Study chaos theory and cryptography in a deep way, analyze the existing cat maps and the encryption algorithm based on Logistic chaotic, analyze the characteristics and applicable ways of these two encryption methods, and analyze some flaws which exist in those methods. Study of Wang-Chen chaotic system and based on the core of security of system and speed of algorithm, using an improved Wang-Chen chaotic system generates chaotic sequence which was used to image encryption. The performance of this chaotic system was analyzed by NIST test method, NPCR and UACI Joint Test Methods and histogram analysis method. The experiment results show that the algorithm has the characteristics of chaotic system, which has the characters of great key space, strong anti-attack property and safety.(2)Analysis and compare the advantages and disadvantages of the main communication protocols UDP and TCP. The security and integrity of the data in the network environment TCP is better than that of UDP. Finally, The TCP protocol was selected for the realization of Socket application. We analysis the encoding process and the decoding process of LZW coding algorithm. The LZW algorithm was implemented in C language. We also implement the application of Wi-Fi transmission and LZW algorithm in chaotic image encryption system. The experimental results show that the LZW algorithm can achieve file transfer in the environment of Wi-Fi. The Socket program is stable and meets the needs basically.(3)Hardware implementation of the chaotic image secures communication system was provided. The environment of embedded Linux system has been set up, including the configuration of hardware resources. The software includes the BootLoader compiling and transplantation, the Linux kernel cutting, the root file system compiling and transplantation. Ultimately, the ARM9 development board of embedded system was built and the chaotic image encryption, decryption, transmission and other important parts were transplanted to the board. The experimental show that the system can realize the safe transmission of image information and has certain value for application. |
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