Evaluating the performance of ST-DM watermarking in non additive channels

In this paper, the performance of ST-DM watermarking in presence of two categories of non additive attacks, such as the gain attack plus noise addition, and the quantization attack, are evaluated. The work has been developed by assuming that the host features are independent and identically distributed Gaussian random variables, and that a minimum distance criterion is used to decode the embedded information. The theoretical bit error probabilities are derived in closed form, thus permitting to evaluate the impact of the considered attacks on the watermark at a theoretical level. The analysis is validated by means of extensive Monte Carlo simulations. Moreover, Monte Carlo simulations permitted to abandon the hypothesis of normally distributed host features, in favor of more realistic models based on a Laplacian or a Generalized Gaussian pdf. The overall result of our analysis is that ST-DM exhibits excellent performance in all cases with the only noticeable exception of the gain attack