Security analysis of a self-embedding fragile image watermark scheme

Abstract

Recently, a self-embedding fragile watermark scheme based on reference-bits interleaving and adaptive selection of embedding mode was proposed. Reference bits are derived from the scrambled MSB bits of a cover image, and then are combined with authentication bits to form the watermark bits for LSB embedding. We find this algorithm has a feature of block independence of embedding watermark such that it is vulnerable to a collage attack. In addition, because the generation of authentication bits via hash function operations is not related to secret keys, we analyze this algorithm by a multiple stego-image attack. We find that the cost of obtaining all the permutation relations of l • b 2 watermark bits of each block (i.e., equivalent permutation keys) is about (l • b 2 )! for the embedding mode (m, l), where m MSB layers of a cover image are used for generating reference bits and l LSB layers for embedding watermark, and b × b is the size of image block. The simulation results and the statistical results demonstrate our analysis is effective.