Digital Watermarking Robustness and Fragility Characteristics: New Modelling and Coding Influence

This paper, introduces a new methodology for the design and analysis of digital watermarking systems which, from an information theoretic point of view, incorporates robustness and fragility. The proposed methodology is developed by focusing on the probability of error versus watermark-to-noise ratio curve, describing the technique performance, and a scenario for coded techniques which takes into account not only the coding gain, but also the robustness or fragility of the system. This new concept requires that coded digital watermarking systems design be revisited to also include the robustness and fragility requirements. Turbo codes, which appropriately meet these requirements, can be used straightforwardly to construct robust watermarking systems. Fragile systems can also be constructed by introducing the idea of polarization scheme. This new idea has allowed the implementation of hybrid techniques achieving fragility and robustness with a single watermark embedding. We moreover, present (turbo) coded techniques which can also be used in a semi-fragile mode.