A digital watermark is a digital signal or pattern inserted into a digital document such as text, graphics or multimedia, and carries information unique to the copyright owner, the creator of the document or the authorized consumer. Digital watermarking is a technique which allows an individual to add hidden copyright notices or other verification messages to digital audio, video, or image signals and documents. Such hidden message is a group of bits describing information pertaining to the signal or to the author of the signal (name, place, etc.). The technique takes its name from watermarking of paper or money as a security measure. Digital watermarking is not a form of steganography, in which data is hidden in the message without the end user's knowledge, although some watermarking techniques have the steganographic feature of not being perceivable by the human eye.