Optimal quantitative cryptanalysis of permutation-only multimedia ciphers against plaintext attacks

Recently, an image scrambling encryption algorithm of pixel bit based on chaos map was proposed. Considering the algorithm as a typical binary image scrambling/permutation algorithm exerting on plaintext of size M x (8N), this paper proposes a novel optimal method to break it with some known/chosen-plaintexts. The spatial complexity and computational complexity of the attack are only O(32 . MN) and O(16 . n(0) . MN) respectively, where no is the number of known/chosen-plaintexts used. The method can be easily extended to break any permutation-only encryption scheme exerting on plaintext of size M x N and with L different levels of values. The corresponding spatial complexity and computational complexity are only O(MN) and O(inverted right perpendicularlog(L)(MN)inverted left perpendicular . MN) respectively. In addition, some specific remarks on the performance of the image scrambling encryption algorithm are presented. (C) 2010 Elsevier B.V. All rights reserved.