1. A method of creating a signature from plural images for providing watermark information related to the images, the method comprising: analysing a pair of images, each image containing a plurality of elements; identifying a first element in one of the pair of images; identifying plural elements in the other of the pair of images; measuring a disparity parameter between the first element and a set of the plural elements; matching the first element with a second element from the set of the plural elements, the matched second element having the smallest measured distance between first element and the second element; and computing a signature based at least in part on the measured disparity parameter between the first element and the second element.