Security analysis of a color image encryption based on bit-level and chaotic map

In recent years, various chaotic image encryption algorithms have been proposed, but their security issues still need to be studied and reviewed. This paper implements a cryptographic security analysis on a color image encryption algorithm based on bit-level and improved one-dimensional chaotic map (CIEA-IOCM). In CIEA-IOCM, using the pseudo-random sequences generated by an improved one-dimensional chaotic map, bit-level permutation-diffusion and linear transformation are successively performed to get its cipher image from a plain image. Based on some seemingly good performance analysis results, CIEA-IOCM claimed that it can withstand various common attacks. However, after a cryptanalysis, we found that it can be completely cracked by a chosen-plaintext attack method. The most essential reason is that there are equivalent keys for both bit-level permutation and diffusion processes, and its linear transformation can be combined and simplified. Thus, we achieved a successful security attack by obtaining the equivalent keys. Moreover, the experimental results verify the effectiveness and efficiency of our method. Therefore, our research work can provide some positive and valuable references for improving the security of chaotic image encryption algorithms.