The Research Of Digital Image Encryption Technology Based On Chaotic Theroy

With the rapid development of computer network communication technology, the network has become one of the important means for people to access information. To ensure the security of multimedia communication becomes an urgent problem to be solved. Images, as a kind of carrier of information, its encryption technique has already been practical and needs to be further developed.In recent years, chaos applications have attracted increasing attention. Chaotic dynamical systems are deterministic systems in non-linear dynamics. There are lots of corresponding features between chaos and classical cryptography. When security of traditional cryptology is confronted with threats, some appealing characters of chaos, such as complexity, sensitivity to the initial conditions and control parameters, pseudo-randomness and unpredictable property, provide new directions for cryptography.First, we introduced the fundamental knowledge of chaos theory and cryptography, and discussed the relationship between them. Second, several primary techniques of encryption based on chaotic system are introduced, and a comprehensive survey about previous research in designing chaotic cryptograph for image encryption is conducted. Then, based on analyzing image encrypting algorithms presently, two image encrypting alrithms are proposes in this paper, one is a new image chaotic encryption algorithm based on external keys and ciphertext feedback, and the other is a new image encryption algorithm based on general Chen's chaotic system and wavelet transform.The first proposed encryption algorithm can not only make full use of the low-dimensional chaotic systems'advantages of simple format and high calculating speed, but also can overcome the low-dimensional chaotic systems'defects of being attacked easily by using phase space reconstitution technologies. The experimental results proves the effectiveness and security of the proposed algorithm.Before proposed the second encryption algorithm, we first analyzed and improved a existing algorithm that shuffle the positions of the image pixels based on general Chen's chaotic system. Then, we combined the permutation algorithm with image wavelet transform and proposed a new chaotic image encryption algorithm. The research results in this paper indicate that its key space is large enough to resist the brute-force attack and it has the robustness against noise attack.Finally, this paper concludes by summarizing the research and indicating its future research directions.