Digital watermark technology in security applications

With the rising emphasis on security and the number of fraud related crimes around the world, authorities are looking for new technologies to tighten security of identity. Among many modern electronic technologies, digital watermarking has unique advantages to enhance the document authenticity. At the current status of the development, digital watermarking technologies are not as matured as other competing technologies to support identity authentication systems. This work presents improvements in performance of two classes of digital watermarking techniques and investigates the issue of watermark synchronisation. Optimal performance can be obtained if the spreading sequences are designed to be orthogonal to the cover vector. In this thesis, two classes of orthogonalisation methods that generate binary sequences quasi-orthogonal to the cover vector are presented. One method, namely "Sorting and Cancelling" generates sequences that have a high level of orthogonality to the cover vector. The Hadamard Matrix based orthogonalisation method, namely "Hadamard Matrix Search" is able to realise overlapped embedding, thus the watermarking capacity and image fidelity can be improved compared to using short watermark sequences. The results are compared with traditional pseudo-randomly generated binary sequences. The advantages of both classes of orthogonalisation inethods are significant. Another watermarking method that is introduced in the thesis is based on writing-on-dirty-paper theory. The method is presented with biorthogonal codes that have the best robustness. The advantage and trade-offs of using biorthogonal codes with this watermark coding methods are analysed comprehensively. The comparisons between orthogonal and non-orthogonal codes that are used in this watermarking method are also made. It is found that fidelity and robustness are contradictory and it is not possible to optimise them simultaneously. Comparisons are also made between all proposed methods. The comparisons are focused on three major performance criteria, fidelity, capacity and robustness. aom two different viewpoints, conclusions are not the same. For fidelity-centric viewpoint, the dirty-paper coding methods using biorthogonal codes has very strong advantage to preserve image fidelity and the advantage of capacity performance is also significant. However, from the power ratio point of view, the orthogonalisation methods demonstrate significant advantage on capacity and robustness. The conclusions are contradictory but together, they summarise the performance generated by different design considerations. The synchronisation of watermark is firstly provided by high contrast frames around the watermarked image. The edge detection filters are used to detect the high contrast borders of the captured image. By scanning the pixels from the border to the centre, the locations of detected edges are stored. The optimal linear regression algorithm is used to estimate the watermarked image frames. Estimation of the regression function provides rotation angle as the slope of the rotated frames. The scaling is corrected by re-sampling the upright image to the original size. A theoretically studied method that is able to synchronise captured image to sub-pixel level accuracy is also presented. By using invariant transforms and the "symmetric phase only matched filter" the captured image can be corrected accurately to original geometric size. The method uses repeating watermarks to form an array in the spatial domain of the watermarked image and the the array that the locations of its elements can reveal information of rotation, translation and scaling with two filtering processes

Implementasi Metode Log-Polar Mapping Dan Phase Correlation Pada Watermaking Citra Digital Yang Independen Terhadap Rotasi, Skala, Dan Translasi

Watermarking adalah proses embedding (penambahan) dan ekstraksi data yang disebut watermark ke dalam sebuah media. Watermark ini bisa berbentuk sinyal, citra, atau barisan bit. Sedangkan media yang digunakan bisa berupa citra atau video atau audio. Fungsi utama dari watermarking adalah sebagai proteksi hak cipta dari media yang diberi watermark. Banyak metode telah digunakan dalam watermarking ini. Salah satunya menggunakan metode Log-Polar Mapping (LPM) dan Phase Correlation. Metode inilah yang digunakan dalam tugas akhir ini. Metode LPM dan Phase Correlation digunakan dalam proses embedding dan ekstraksi watermark. Proses-proses ini dilakukan pada magnitude dari domain Fourier sebuah citra digital untuk membuat watermarking independen terhadap translasi. Metode LPM digunakan pada proses embedding untuk membuat watermark yang independen terhadap rotasi dan skala. Sedangkan metode Phase Correlation dalam proses ekstraksi watermark bersamaan dengan metode LPM digunakan dalam proses penyesuaian (rect(fication) citra digital. Dengan kedua metode ini posisi watermark dalam magnitude tetap terjaga sehingga watermark mudah diekstraksi. Selain itu watermark terhindar dari resiko pengurangan kualitas yang disebabkan oleh LPM. Uji coba dilakukan menggunakan 5 citra digital dan berbagai macam watermark. Hasil uji coba menunjukkan terdeteksinya watermark pada hampir semua kasus, hal ini menunjukkan watermarking ini independen terhadap rotasi, skala, dan translasi (RST)

Identificaçăo de propriedade em imagens com marcas d'água no domínio da transformada wavelet /

Orientador: Hélio PedriniInclui apęndiceInclui bibliografi

Data Hiding and Its Applications

Data hiding techniques have been widely used to provide copyright protection, data integrity, covert communication, non-repudiation, and authentication, among other applications. In the context of the increased dissemination and distribution of multimedia content over the internet, data hiding methods, such as digital watermarking and steganography, are becoming increasingly relevant in providing multimedia security. The goal of this book is to focus on the improvement of data hiding algorithms and their different applications (both traditional and emerging), bringing together researchers and practitioners from different research fields, including data hiding, signal processing, cryptography, and information theory, among others

Framework for Automatic Identification of Paper Watermarks with Chain Codes

Title from PDF of title page viewed May 21, 2018Dissertation advisor: Reza DerakhshaniVitaIncludes bibliographical references (pages 220-235)Thesis (Ph.D.)--School of Computing and Engineering. University of Missouri--Kansas City, 2017In this dissertation, I present a new framework for automated description, archiving, and identification of paper watermarks found in historical documents and manuscripts. The early manufacturers of paper have introduced the embedding of identifying marks and patterns as a sign of a distinct origin and perhaps as a signature of quality. Thousands of watermarks have been studied, classified, and archived. Most of the classification categories are based on image similarity and are searchable based on a set of defined contextual descriptors. The novel method presented here is for automatic classification, identification (matching) and retrieval of watermark images based on chain code descriptors (CC). The approach for generation of unique CC includes a novel image preprocessing method to provide a solution for rotation and scale invariant representation of watermarks. The unique codes are truly reversible, providing high ratio lossless compression, fast searching, and image matching. The development of a novel distance measure for CC comparison is also presented. Examples for the complete process are given using the recently acquired watermarks digitized with hyper-spectral imaging of Summa Theologica, the work of Antonino Pierozzi (1389 – 1459). The performance of the algorithm on large datasets is demonstrated using watermarks datasets from well-known library catalogue collections.Introduction -- Paper and paper watermarks -- Automatic identification of paper watermarks -- Rotation, Scale and translation invariant chain code -- Comparison of RST_Invariant chain code -- Automatic identification of watermarks with chain codes -- Watermark composite feature vector -- Summary -- Appendix A. Watermarks from the Bernstein Collection used in this study -- Appendix B. The original and transformed images of watermarks -- Appendix C. The transformed and scaled images of watermarks -- Appendix D. Example of chain cod

Rotation, scaling and translation invariant digital image watermarking

Many digital image watermarking schemes have been proposed and are robust to common signal processing, such as compression and filtering. Geometric distortions, such as rotation, scaling, and translation (RST), are considered the most challenging attacks. This thesis is on RST invariant digital image watermarking. In this thesis, we introduce the fundamental theories and techniques necessary for RST invariant digital image watermarking, and briefly review the existing RST invariant image watermarking schemes. Then, we propose an image rectification scheme for RST invariant digital image watermarking. Rotation and scaling transformations in the spatial domain result in cyclical shifts in the log-polar domain, which is the log-polar mapping (LPM) of the magnitude of the Fourier spectrum of the image. We utilize this property to detect the rotation and scaling parameters by using a matching template and our new phase-only filtering method in the LPM domain. We employ the same strategy in the spatial domain to detect the translation parameters. This rectification scheme can detect RST parameters very accurately. (Abstract shortened by UMI.