DCT-based watermark recovering without resorting to the uncorrupted original image

TLDR

Digital watermarking protects multimedia by enabling identification of authors, owners, distributors, or authorized users in networked environments. The study introduces a watermarking method that embeds a pseudo‑random sequence of real numbers into selected DCT coefficients of digital images. The technique embeds the sequence into chosen DCT coefficients, applies HVS masking for invisibility, and extracts the watermark without requiring the original image. Experiments demonstrate the watermark remains robust against most signal‑processing attacks and geometric distortions.

Abstract

Digital watermarking has been proposed as a viable solution to the need of copyright protection and authentication of multimedia data in a networked environment, since it makes it possible to identify the author, owner, distributor or authorized consumer of a document. In this paper a new watermarking technique to add a code to digital images is presented; the method operates in the frequency domain embedding a pseudo-random sequence of real numbers in a selected set of DCT coefficients. Watermark casting is performed by exploiting the masking characteristics of the human visual system, to ensure watermark invisibility. The embedded sequence is extracted without resorting to the original image, so that the proposed technique represents a major improvement to methods relying on the comparison between the watermarked and original images. Experimental results demonstrate that the watermark is robust to most of the signal processing techniques and geometric distortions.