COPYRIGHT PROTECTION OF DIGITAL IMAGES BY EMBEDDED UNPERCEIVABLE MARKS

Digital watermarking has been proposed as a solution to the problem of copyright protection of multimedia documents in a networked environme nt. It makes it possible to tightly associate a code to an image, allo wing the identification of the data creator, owner and so on. In this paper, after a review of some important watermarking techniques, a new watermarking algorithm for digital images is presented: the method, w hich enhances a previous technique proposed by Cox et al. [1] [I.J. Co x, J. Kilian, T. Leighton, T. Shamoon, Secure spread spectrum watermar king for multimedia, NEC Research Institute Technical Report 95-10], o perates in the frequency domain, by embedding in a selected set of DCT coefficients a sequence of randomly generated real numbers. By exploi ting their statistical characteristics, it is possible to reliably ext ract the embedded sequences without resorting to the original unmarked image. Experimental results demonstrate that the watermark is robust to several image transformations. (C) 1998 Elsevier Science B.V. All r ights reserved.