| As in the information era, the information communication technology and the Internet technology was experiencing a rapid development and widely used. The more information is transmitted through the Internet, the more attention was drew to the information security and privacy problems, which changes cryptography a rising important area in the study of computer security.Some emerging theories of cryptography, such as chaotic cryptography, quantum cryptography are getting more popular among scholars. Today, multimedia technology is developed abundantly, especially in the field of images, videos, etc. which are involved with an enormous amount of data. In order to operate, transmit, store more effectively, the multimedia data, data compression technology becomes a hot spot in multimedia data processing area. The widely used image and multimedia information are challenging the traditional encryption algorithms since the large amount of data and high redundancy. Along with the rising requirements for security and coding efficiency of the algorithm in nowadays scientific research, lots of scientist made many efforts previously, which improved the security and flexibility of multimedia application.The dissertation is dedicated in studying of joint compression and encryption algorithm based on chaos theory research. It is introduced systematically that the basic knowledge of cryptography and the relevant knowledge of data compression technology. The insufficient was discussed in detail about the existing two algorithms, encryption first or compression first. Basing on that, two brightly new joint compression and encryption algorithms are put forward, chaos based cryptosystem using adaptive Huffman tree and chaos based cryptosystem using adaptive arithmetic coding. This essay analyzed characteristics of the algorithms theoretically, including the key space, the randomness, the information entropy, the compression ratio and the encoding speed, etc. Lots of experiments were done for the comparison and analysis reason. Basing on the simulation test, it is illustrated that these algorithms can enhance the randomness of probability distribution and the entropy of output stream effectively. The security of the algorithm is improved drastically with compression ratio barely effected. In the end of the article, a summery was made and the future research direction was prospected. |
