Optimization strategies for quantization watermarking with application to image authentication

In this paper we present optimal quantization watermarking strategies with respect to the robustness of a watermarking system given the embedding rate and distortion constraint. Firstly, we investigate the optimal decoding for quantization watermarking and show that by making use of channel statistics, the maximum likelihood decoder is always better than the minimum distance decoder. Secondly, the optimal encoding is designed by exploiting the knowledge of the host signal and channel statistics. Algorithms for designing the optimal uniform quantization encoding scheme and optimal nonuniform quantization encoding scheme are proposed. Simulation results show that the optimal nonuniform quantization watermarking can achieve better performance. Finally, applications to image authentication which is robust to high quality JPEG compression are described.