Walsh-coded signatures for robust digital image watermarking

This paper proposes the use of 1-D Walsh coding to improve the robustness of digital image watermarking techniques. In the proposed method, Walsh functions are used to encode the watermark before embedding it in the original image. Results indicate that this type of coding results in less visible degradation to the watermarked image than direct scaling. Simulation results using both spatial-domain and frequency-domain techniques indicate that the use of Walsh coding results in improved robustness against JPEG compression attacks. It is also shown that frequency domain watermarking is more resistant to JPEG compression attacks and also less sensitive to the contents of the input original image. Increasing the length of the Walsh function results in more robustness but at the expense of more degradation to the quality of the watermarked image.