A DCT-DOMAIN SYSTEM FOR ROBUST IMAGE WATERMARKING

Digital watermarking has been proposed as a solution to the problem of copyright protection of multimedia data in a networked environment. I t makes possible to tightly associate to a digital document a code all owing the identification of the data creator, owner, authorized consum er, and so on. In this paper a new watermarking algorithm for digital images is presented: the method, which operates in the frequency domai n, embeds a pseudo-random sequence of real numbers in a selected set o f DCT coefficients. After embedding, the watermark is adapted to the i mage by exploiting the masking characteristics of the human visual sys tem, thus ensuring the watermark invisibility. By exploiting the stati stical properties of the embedded sequence, the mark can be reliably e xtracted without resorting to the original uncorrupted image. Experime ntal results demonstrate that the watermark is robust to several signa l processing techniques, including JPEG compression, low pass and medi an filtering, histogram equalization and stretching, dithering, additi on of Gaussian noise, resizing, and multiple watermarking. (C) 1998 El sevier Science B.V. All rights reserved.