Abstract: Digital watermarking is a kind of data hiding technology. It is a way of embedding information (i.e., watermark) in multimedia data (image, audio or video), such that the embedded watermark can be later retrieved from the watermarked data for the purpose of content protection or authentication. Among different kinds of digital watermarking schemes, reversible watermarking has become a research hotspot recently. For about ten years, several reversible watermarking schemes have been proposed for protecting images of sensitive content, like medical or military images, for which any modification may impact their interpretation. These methods allow the user to restore exactly the original image from its watermarked version by removing the watermark. Thus it becomes possible to update the watermark content, as for example security attributes (e.g., one digital signature or some authenticity codes), at any time without adding new image distortions.

Keywords: Digital watermarking, reversible watermarking, digital signature, authenticity codes.