1. A method for embedding a watermark signal that contains message data in a digital image represented as a two-dimensional array of pixel values, comprising the steps of: a) providing a dispersed message image having pixel values representative of the message data; b) modifying each pixel value of the dispersed message image as a function of the corresponding pixel value in the digital image; and c) combining the modified dispersed message image with the digital image to produce a watermarked image.