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

*Shujun Li and Chengqing Li and Guanrong Chen and 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.

**Category / Keywords: **permutation-only multimedia encryption, image, video, speech, cryptanalysis, known-plaintext attack, chosen-plaintext attack

**Publication Info: **Signal Processing: Image Communication, vol. 23, no. 3, pp. 212-223, 2008, DOI: 10.1016/j.image.2008.01.003

**Date: **received 29 Dec 2004, last revised 6 May 2008

**Contact author: **hooklee75 at hotmail com

**Available format(s): **PDF | BibTeX Citation

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

**Version: **20080506:111459 (All versions of this report)

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