Abstract: With the development of multimedia technologies,the applications based on digital images have become more and more popular,the security issues of the image itself and the privacy problems of the image owners are more severe in current environment.Different from text,digital images data as a two-dimensional data with large volume of data,high redundancy and strong correlation between pixels.It is difficult to achieve the effect of encryption when traditional encryption method is applied directly to image encryption.At present,encryption based on chaos theory is one of the mainstream methods in the field of image encryption,which using the classical structure of scrambling-diffusion,making use of the high randomness of the chao-tic sequences to ensure the security of the encryption results,and has a high encryption efficiency at the same time.In order to further improve the security of chaotic encryption algorithms,a large number of complex chaotic maps,such as hyper-chaos and multi-level chaos,have been proposed,however,the computational complexity is much higher than that of one-dimensional chaotic maps.To solve this problem,an efficient chaotic map called SPM is designed through combining Sine map and PWLCM,which expands thechao-tic range,enhances the ergodicity and lifts up the generation speed of chaotic sequence without reducing security.Based on this,an image encryption algorithm based on a novel structure is designed.Only one round of scrambling-diffusion-scrambling is needed to complete the encryption in this method,which reduces the encryption rounds compared to traditional methods and further improves the efficiency of encryption.The fully experiments show that the proposed method can effectively resist the chosen plain-image/cipher-image attacks and the encryption efficiency is improved by about 58% on average,meaning a high practicability.

Key words: Chosen plain-image/cipher-image encryption attack, Compound chaotic map, Image encryption, One-round encryption, Pseudo-randomness