Data that is embedded into media such as a graphic which is hidden from sight, but which can be recovered by executing a program that displays it. There are a number of uses for digital watermarking. The first is to show ownership. For example, the owner of a media object would place a watermark in that object using a private key. If someone claimed ownership of the object the original owner could recover the watermark by decryption and prove ownership. The second use is to detect unauthorized duplication. The third use is to provide authentication and integrity verification in legal cases where the authenticity of a media object such as a photograph has to be demonstrated. The fourth use is to provide hidden content labelling: for example, a watermark could be used to provide subsidiary information about a photograph, such as who the subject was and when it was taken. The fifth use is in usage control where the watermark would be dynamic and would include a number which indicated how many copies should be taken of the media object. This figure would be decreased every time a copy was taken. Watermark technology is in its early days, but a number of products have been a released.