Self-embedding fragile watermarking based on DCT and fast fractal coding

Abstract

A self-embedding fragile watermarking scheme is proposed in this paper, which is based on Discrete Cosine Transform and fractal compression coding. To overcome the high computational complexity of fractal coding, a fast coding method is also presented that improves the efficiency of fractal block coding in the watermarking procedure. In our algorithm, three kinds of watermarks are generated for image authentication and recovery, which is based on an interleaved and overlapped 8 ×8 image block structure. This makes our method obtain an authentication granularity of 4 ×4 approximately. At the same time, we take advantage of two levels of mapping to select mapping block for every image block. Three versions of recovery watermarks for each block are embedded in different quadrants, which provides another two chances for block recovery in case one is destroyed. Experimental results demonstrate that the proposed scheme not only outperforms conventional self-embedding fragile watermarking algorithms in tamper recovery, but also improves the security against the various counterfeiting attacks.