A General Cryptanalysis of Permutation-Only Multimedia Encryption Algorithms

Secrete permutations are widely used in multimedia encryption algorithms, and many permutation-only ciphers have been proposed in recent years for protection of different types of multimedia data, especially digital images and videos. Based on a normalized encryption/decryption model, this paper analyzes the security of permutation-only image ciphers working in spatial domain from a general perspective, taking a recentlyproposed permutation-only image cipher called HCIE (hierarchical chaotic image encryption) as a typical example. It is pointed out that all permutation-only image ciphers are insecure against known/chosen-plaintext attacks in the sense that only O (logL(MN)) known/chosen plain-images are enough to break the ciphers, where MN is the size of the image and L is the number of different pixel values. Also, it is found that the attack complexity is only O(n · (MN)), where n is the number of known/chosen plain-images used. Following the results, it is found that hierarchical permutation-only image ciphers such as HCIE are less secure than normal (i.e., non-hierarchical) permutationonly image ciphers. Experiments are shown to verify the feasibility of the known/chosen-plaintext attacks. The cryptanalysis result is then generalized to permutation-only image ciphers working in frequency domain and video ciphers. In conclusion, secret permutations have to be combined with other encryption techniques to design highly secure multimedia encryption sysThis research was partially supported by the AIIS Inc., NY, USA, the Applied R&D Centers of the City University of Hong Kong (under grants no. 9410011 and no. 9620004), and the National Natural Science Foundation of China (under grant no. 60202002). Shujun Li and Guanrong Chen are with the Department of Electronic Engineering, City University of Hong Kong, Kowloon, Hong Kong, China. E-mails: [email protected], [email protected]. Chengqing Li is with the Department of Mathematics, Zhejiang University, Hangzhou, Zhejiang 310027, China. E-mail: [email protected]. Dan Zhang is with the College of Computer Science, Zhejiang University, Hangzhou, Zhejiang 310027, China. Nikolaos G. Bourbakis is with the Information Technology Research Institute, College of Engineering and Computer Science, Wright State University, 3640 Glenn Hwy, Dayton, OH 45435, USA. tems. This paper provides for the first time theoretically and experimentally clarification of such a security principle on the design of multimedia encryption algorithms.