Improved watermark extraction using dynamic stochastic resonance

In this paper, a dynamic stochastic resonance (DSR)-based blind watermark extraction technique has been proposed for robust extraction of a binary watermark. The watermark embedding has been done in mid-band DCT coefficients using well-known PN sequences. Dynamic stochastic resonance has been strategically used to improve the robustness of the extraction algorithm by utilizing the added noise (or degradation) during attacks itself. DSR is a converging iterative process that tunes the coefficients of the possibly attacked image so that effect of noise is suppressed and hidden information is enhanced. Resilience of this technique has been tested in the presence of various attacks such as noise attacks, geometrical distortions, enhancement, compression and filtering. A simple optimization procedure has been adopted for the selection of bistable double-well system parameters in the DSR step so to achieve maximum correlation coefficient under minimum computational complexity. Using the proposed adaptive DSR-based extraction technique, a very robust extraction of watermark can be done without trading-off with visual quality of the watermarked image. When compared with the plain DCT-based technique, the proposed DSR-based DCT technique has been found to give better performance.