Analyzing And Designing Of Image Encryption Algorithm Based On Chaos Theory

Compared to the traditional information encryptions, digital image encryption has its own features and different encryption algorithm. Chaotic dynamics system, a kind of deterministic nonlinear system and has many corresponds to the characteristics of the cryptography, has been widely used and researched in the field of image encryption.This article focuses on the encryption algorithm which based on chaos with the struction of "permutation-diffusion". At the first, introduces the basic knowledge of cryptography, chaos theory and the relationship of them. It is simple inducts and sums that general technology of digital image encryption, image encryption based on chaotic system and the future development trend of them, and detailed instructions that several common character of the encryption algorithm based on chaotic with "permutation-diffusion" structure.In the second, Analysis a typical image encryption scheme which have the structure of the mentioned above. According to the problem, design a attack scheme combining the chosen plaintext and chosen ciphertex. It can not only fully decryption the intermediate keys were used in image encryption scheme, and compared to other decryption method the decryption method can decrypt more ciphertext at once which were encryption with the some keys. Analyse the vulnerabilities of the image encryption scheme. If an encryption system with the intermediate keys just associated with the encryption key, only the safety of the system is yet to be further improved. After that designed a new method to produce the intermediate keys that is not only related to encryption key and encryption algorithm, but also related to the encrypt plaintext, namely in the procedure of permutation and diffusion all join the effect of plaintext. So different plaintext will generated difference effect make the intermediate keys is dynamic to reduce the possibility of decryption and improve the security of system. Simulation experiments show that the improved scheme not only retains the advantages of original algorithm and has better performance especially for safety performance. Finally, this paper concludes by summarizing the research and the improve place of the work, and the future research direction and planning were discussed.