Abstract: In this paper,a scheme of scrambling was designed,and four-dimensional hyperchaos was improved. Based on the chaos method and hyperchaos,the algorithm of double chaos image encryption was proposed. The scrambled method uses Logistic map to scramble the image twice,then takes the scrambled ciphertext image as input,and diffuses it with the improved 4d hyperchaos to get the final ciphertext image. The algorithm designed in this paper combines the image block scrambling and the whole row and column scrambling to ensure the pixel scrambling rate of nearly 100%. In the process of diffusion,the key stream with more pseudo-randomness is generated through improved hyperchaos for multiple encryption,so that the plaintext information can be well hidden. The simulation results show that the algorithm has good encryption effect,not only has strong sensitivity and large key space,but also can resist attack effectively,and has certain application value in image information security.

Key words: Chaos, Chaos encryption, Image encryption, Super chaos