Copyright protection of digital images by means of frequency domain watermarking

Notwithstanding the high availability of image contents, multimedia products propose very low quality pictures, primarily due to the fact that effective systems for the copyright protection of multimedia works are unavailable. A digital image can, in fact, be easily reproduced obtaining as many identical copies of it as we want, without any possibility to prevent it. To get around the problem, further than scrambling the data to be protected by means of cryptograpic techniques, a code carrying information about IPR (Intellectual Property Rights) could be invisibly embedded into them, in such a way to provide a mean to control their distribution. This is the aim of image watermarking techniques. In this paper general issues related to copyright protection of digital data as well as some items referring to the embedding of a watermark in the frequency domain, are discussed. Results are also presented showing the robustness of the proposed algorithms.