Paper 2004/374

A general quantitative cryptanalysis of permutation-only multimedia ciphers against plaintext attacks

Shujun Li, Chengqing Li, Guanrong Chen, Nikolaos G. Bourbakis, and Kwok-Tung Lo

Abstract

In recent years secret permutations have been widely used for protecting different types of multimedia data, including speech files, digital images and videos. Based on a general model of permutation-only multimedia ciphers, this paper performs a quantitative cryptanalysis on the performance of these kind of ciphers against plaintext attacks. When the plaintext is of size $M\times N$ and with $L$ different levels of values, the following quantitative cryptanalytic findings have been concluded under the assumption of a uniform distribution of each element in the plaintext: 1) all permutation-only multimedia ciphers are practically insecure against known/chosen-plaintext attacks in the sense that only $O(log_L(MN))$ known/chosen plaintexts are sufficient to recover not less than (in an average sense) half elements of the plaintext; 2) the computational complexity of the known/chosen-plaintext attack is only $O(n\cdot(MN)^2)$, where n is the number of known/chosen plaintexts used. When the plaintext has a non-uniform distribution, the number of required plaintexts and the computational complexity is also discussed. Experiments are given to demonstrate the real performance of the known-plaintext attack for a typical permutation-only image cipher.

Note: A published edition of the pre-print, with many major revisions.