Hybrid multiplicative multi-watermarking in DWT domain

Multiwatermarking embeds multiple watermarks into the media content imperceptibly. It is regarded as the potential means to protect the media contents' copyright and/or trace illegal redistributors in multi-user environments, e.g., collaborative media content production or layered media content distribution. However, there are still some open issues in designing a good multiwatermarking scheme, including the combination between multiple embedding steps, the combination between multiple watermarks and the security of embedding schemes. In this paper, novel multiwatermarking schemes are proposed, which are based on hybrid multi-bit multiplicative rules controlled by secret keys. Two hybrid multiplicative multiwatermarking decoders, i.e., optimum and locally optimum, are proposed, which are based on the minimum Bayesian risk criterion and the DWT coefficients are modeled as the generalized Gaussian distribution. The BER (average bit error rate) as the evaluation index of the performance of optimum hybrid decoders is exactly analyzed. Finally, experimental results are shown to confirm the validity of the theoretical and empirical analysis.