Frequency Domain Watermarking: An Overview

With rapid growth in computer network and information technology, a large number of copyrighted works now exist digitally as a computer files, and electronic publishing is becoming more popular. These improvements in computer technology increase the problems associated with copyright enforcement and thus future developments of networked multimedia systems are conditioned by the development of efficient methods to protect ownership rights against unauthorized copying and redistribution. Digital watermarking has recently emerged as a candidate to solve this difficult problem. In the first part of this paper we introduces an overview to digital watermarking: The general framework, its main applications, the most important properties, the main aspects used to classify watermarking, and we discuss the attacks that watermarking system may face. Finally we introduce human visual system and its interaction with watermarking as well as some open problems in digital watermarking. In the second part we introduces an overview of watermarking in frequency domain. The general properties for frequency domain as well as specific properties for each sub-domain are introduced. The sub-domains considered are discrete cosine domain, discrete wavelet domain and discrete Fourier domain. We also introduce some different watermarking techniques in each category.