Digital watermarking techniques and methodologies

Digital watermarking is a huge research area which is progressively growing. It covers theoretical studies. novel techniques, attacks and performance analysis. Over the years, the digital watermarking community has focused on developing new techniques for watermark embedding and detection. Analysis of these techniques leads to methods for attacks and countermeasures which are used to discover faults and limitations in applications, encouraging the development of better ones. Digital watermarking is distinctive depending on its techniques and applications. The location of watermark embedding determines two kinds of methods:- The spatial domain methods embed watermark information directly into images pixels. On the other hand, the frequency domain methods embed watelmark information in the transform domain. The general approach used in these methods is to divide the image into blocks. Each block is mapped into the transform domain using either the Discrete Cosine Transform (DCT) [9], the Discrete Fourier Transform (DFT), or the Wavelet Transform. Embedding the watermark in the frequency domain can provide more robustness than in the spatial domain. It is strong against attacks like compression where spatial domain is not. Image watermarking techniques can be distinguished according to the way the watermark is revealed from the watermarked image. One way is by comparing this image to the original one, while the other doesn't resort to this comparison. The second are usually refen'ed to as blind watermarking techniques and are preferable

Digital image watermarking techniques

The ability to resolve ownership disputes and copyright infringement is difficult in the worldwide digital age. There is an increasing need to develop techniques that protect the owner of digital data. Digital Watermarking is a technique used to embed a known piece of digital data within another piece of digital data. The embedded piece of data acts as a fingerprint for the owner, allowing the protection of copyright, authentication of the data, and tracing of illegal copies. The goal of this thesis is to produce two watermarking tools and compare their effectiveness with that of other watermarking tools. One of the tools uses a spatial watermarking technique, while the other uses a frequency based spread spectrum technique. These represent the two current approaches to digital watermarking. Use of a standard benchmark is necessary to advance the science of digital watermarking. Until recently, there have been no standard metrics for deter mining the effectiveness of a particular watermarking scheme. Several recent papers propose standard procedures and metrics for comparing watermarking techniques. The proposed metrics and test bed imagery are used as the basis for comparison with other watermark techniques. Overall, the most successful techniques model themselves after data communications techniques. In this case, the image is similar to the atmosphere (medium) and the watermark message is the signal communicated through the medium. The spread spectrum technique yields results that in some cases are comparable to commercial watermarking tools. The spatial domain tool as implemented is inadequate for comparison with the commercial tools

Spread spectrum-based video watermarking algorithms for copyright protection

Merged with duplicate record 10026.1/2263 on 14.03.2017 by CS (TIS)Digital technologies know an unprecedented expansion in the last years. The consumer can now benefit from hardware and software which was considered state-of-the-art several years ago. The advantages offered by the digital technologies are major but the same digital technology opens the door for unlimited piracy. Copying an analogue VCR tape was certainly possible and relatively easy, in spite of various forms of protection, but due to the analogue environment, the subsequent copies had an inherent loss in quality. This was a natural way of limiting the multiple copying of a video material. With digital technology, this barrier disappears, being possible to make as many copies as desired, without any loss in quality whatsoever. Digital watermarking is one of the best available tools for fighting this threat. The aim of the present work was to develop a digital watermarking system compliant with the recommendations drawn by the EBU, for video broadcast monitoring. Since the watermark can be inserted in either spatial domain or transform domain, this aspect was investigated and led to the conclusion that wavelet transform is one of the best solutions available. Since watermarking is not an easy task, especially considering the robustness under various attacks several techniques were employed in order to increase the capacity/robustness of the system: spread-spectrum and modulation techniques to cast the watermark, powerful error correction to protect the mark, human visual models to insert a robust mark and to ensure its invisibility. The combination of these methods led to a major improvement, but yet the system wasn't robust to several important geometrical attacks. In order to achieve this last milestone, the system uses two distinct watermarks: a spatial domain reference watermark and the main watermark embedded in the wavelet domain. By using this reference watermark and techniques specific to image registration, the system is able to determine the parameters of the attack and revert it. Once the attack was reverted, the main watermark is recovered. The final result is a high capacity, blind DWr-based video watermarking system, robust to a wide range of attacks.BBC Research & Developmen