Discrete Polynomial Transform for Digital Imagewatermarking Application

In this study, we propose a new way to detect the image watermark messages modulated as linear chirp signals. The spread spectrum image watermarking algorithm embeds linear chirps as watermark messages. The phase of the chirp represents watermark message such that each phase corresponds to a different message. We extract the watermark message using a phase detection algorithm based on discrete polynomial phase transform (DPT). The DPT models the signal as polynomial and uses ambiguity function to estimate the signal parameters. The proposed method not only detects the presence of watermark, but also extracts the embedded watermark bits and ensures the message is received correctly. The robustness of the proposed detection scheme has been evaluated using checkmark benchmark attacks, and we found a guaranteed maximum bit error rate of 15%, which watermark message is correctly detected using DPT