Copyright protects the author’s original work against plagiarism and the distribution, commercial or otherwise, of unauthorized reproductions. The use of the Internet has resulted in the ease of copying digital information without any loss of quality. This has a considerable impact on the originators and owners of intellectual property. To solve the problem of publishing digital multimedia, researchers have come up with digital image watermarking. This method allows the owner of an original image to add an invisible watermark to the digital image before publishing it. The watermark serves to enforce copyright on the image. The owner protects the watermark with a cryptographic secret key in order to prevent an unauthorized party from reading or even detecting the watermark. The watermark is also designed to be robust against image tampering. Therefore, anyone who wants to distribute the image further will also distribute the watermark with it, which implies that they will have violated the copyright of the image. If the copyright holder can detect the fraud, he/she can prove ownership by showing that the image contains his/her proper private watermark.
The protection of the creators’ work encompasses many different aspects including copyright protection and moral rights protection. We examine three types of watermarking applications dealing with Intellectual Property Right (IPR) protection (Barni & Bartolini, 2004).
The owner wishes to prove that he/she is the only legitimate owner of the work. To do so, as soon as he/she creates the work, he/she embeds a watermark identifying him/her unambiguously within it. Unfortunately, this simple scheme cannot provide a valid proof in front of a court of law, unless the non-invertibility (non-quasi-invertibility) of the watermarking algorithm is demonstrated. A common way to confer the watermark verification procedure a legal value is to introduce the presence of a Trusted Third Party (TTP) in the watermarking protocol. For example, the watermark identifying the author may be assigned to him/her by a trusted registration authority, thus preventing the possibility to use the SWICO attack (Single-Watermarked-Image-Counterfeit-Original) to fool the ownership verification procedure. Protecting rightful ownership is the main focus of this chapter. For the convenience, the general term “copyright protection” is used in the rest of the chapter instead of rightful ownership.