The Binary Phase Only Filter as an Image Watermark

We describe our new method for watermarking digital images. Our work is motivated by the study of phase only filters in Fourier optics. In this paper we concentrate on grey scale images, even though our method works for color also. We take the discrete Fourier transform of an image and determine a signature based upon a binary phase-only filter BPOF. We replace certain frequency magnitudes with this BPOF. This serves as the basis for our watermark. We may also insert additional side information and our method prevents spoofing of the watermark. Our method survives JPEG compression so that the watermark survives to pass various correlation tests. Our watermarking scheme is used for authentication purposes.