The Good is Blondie, a wandering gunman with a strong personal sense of honor. The Bad is Angel Eyes, a sadistic hitman who always hits his mark. The Ugly is Tuco, a Mexican bandit whos always only looking out for himself. Against the backdrop of the
BOWS contest, they search for a watermark in gold buried in three images. Each knows only a portion of the golds exact location, so for the moment theyre dependent on each other. However, none are particularly inclined to share...
Nowadays, a popular method used for additive watermarking is wide spread spectrum. It consists in adding a spread signal into the host document. This signal is obtained by the sum of a set of carrier vectors, which are modulated by the bits to be emb
edded. To extract these embedded bits, weighted correlations between the watermarked document and the carriers are computed. Unfortunately, even without any attack, the obtained set of bits can be corrupted due to the interference with the host signal (host interference) and also due to the interference with the others carriers (inter-symbols interference (ISI) due to the non-orthogonality of the carriers). Some recent watermarking algorithms deal with host interference using side informed methods, but inter-symbols interference problem is still open. In this paper, we deal with interference cancellation methods, and we propose to consider ISI as side information and to integrate it into the host signal. This leads to a great improvement of extraction performance in term of signal-to-noise ratio and/or watermark robustness.
The theoretical foundations of data hiding have been revealed by formulating the problem as message communication over a noisy channel. We revisit the problem in light of a more general characterization of the watermark channel and of weighted distor
tion measures. Considering spread spectrum based information hiding, we release the usual assumption of an i.i.d. cover signal. The game-theoretic resolution of the problem reveals a generalized characterization of optimum attacks. The paper then derives closed-form expressions for the different parameters exhibiting a practical embedding and extraction technique.
