Signal design for robust watermarking on ISI channels

Digital watermarking is equivalent to band-limited power limited digital communications. The power limit arises due to requirement for imperceptible watermarks. The bandwidth limit arises due to the decaying spectrum of the image, opening the door to low-pass filtering attacks that impair watermarks via intersymbol interference (ISI). We aim to design ISI-resistant watermarks via the Nyquist criterion. The key contribution of our work is a modulation scheme that (1) avoids low frequency interference from the host and (2) avoids the high frequency regions where the watermark can be destroyed without visually altering the image. This method exhibits significant improvements compared to existing methods that are not ISI-aware.