A process for watermarking images that includes embedding into the images before their transmission a message by modifying the data characteristic of the images. Further, a co-watermarking is performed by periodic embedding of a binary matrix into the image to determine on reception the co-ordinates of the origin of the initial image and allow the registration of the images received relative to this origin so as to make it possible to read the embedded message. Such a process may find particular application to the transmission of stationary or video images.