On the Security of a Class of Image Encryption Scheme
Recently four chaos-based image encryption schemes were proposed. Essentially, the four schemes can be classified as one class, which is composed of two basic parts: position permutation and diffusion of pixel value with the same cipher-text feedback function. The operations involved in the two basic parts are determined by a random number sequence generated by iterating a chaotic dynamic system. According to the security requirement, the two basic parts are performed alternatively for some rounds. Although the original
authors claimed that the schemes are of high quality, we found the following security problems: 1) the schemes are not sensitive to the change of plain-image; 2) the schemes are not sensitive to the change of secret key; 3) there exist a serious flaw of the diffusion function; 4) the schemes can be broken with no more than $\lceil\log_L(MN)\rceil+3$ chosen-images when the iteration number is equal to one, where $MN$ is the size of the plain-image and $L$ is the number of different pixel values.