Additive non-Gaussian noise attacks on the scalar Costa scheme (SCS)
Roman Tzschoppe, Robert Bäuml, Robert F. H. Fischer, Johannes B. Huber, André Kaup · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2005
The additive attack public mutual information game is explicitly solved for one of the simplest quantization based watermarking schemes, the scalar Costa scheme (SCS). It is a zero-sum game played between the embedder and the attacker, and the payoff function is the mutual information. The solution of the game, a subgame perfect nash equilibrium, is found by backward induction. Therefore, the Blahut-Arimoto algorithm is employed for numerically optimizing the mutual information over noise distributions. Although the worst case distribution is in general strongly non-Gaussian, the capacity degradation compared to a suboptimal Gaussian noise attack is quite small. The loss, if the embedder optimizes SCS for a Gaussian attack but the worst case attack is employed, is negligible.