Watermarking

An embedded identity code, sometimes unique, sometimes secret. Watermarking can exist in currency, images or graphics and even sound. Digital audio watermarks are not very reliable however.

Watermarks have a number of designs and uses including authentication of DRM for piracy prevention, steganography and forensic applications. Watermarking cane present privacy problems. They can be used to make secret marks in a peripherals output, like hardcopy prints.