Wavelet Methods in Steganography

This paper is devoted to graphic information protection by means of computer steganography using wavelet techniques. The methods of the image processing using digital watermarking are classified. Some research of the structure of the digital image is investigated. In the first solution the steganographic system, which usesa discrete wavelet transform for embedding of grayscale watermark into wavelet coefficients of grayscale container is mоdeled and realized. Stego image is achieved by the inverse discrete wavelet transform. Binarization using halftoning algorithm is considered as a kind of powerful attack to stego image. After binarization attack the extracted watermark was found to have acceptable visual quality. The degradation ofthe embedded digital watermark after binarization is estimated using human visual system. Corresponding conclusions on steganographic system stability are drawn. In the second solution we propose the steganographic scheme which uses the proposed wavelet basis images

ИНТЕЛЛЕКТУАЛЬНЫЙ числовым программным ДЛЯ MIMD-компьютер

For most scientific and engineering problems simulated on computers the solving of problems of the computational mathematics with approximately given initial data constitutes an intermediate or a final stage. Basic problems of the computational mathematics include the investigating and solving of linear algebraic systems, evaluating of eigenvalues and eigenvectors of matrices, the solving of systems of non-linear equations, numerical integration of initial- value problems for systems of ordinary differential equations.Для більшості наукових та інженерних задач моделювання на ЕОМ рішення задач обчислювальної математики з наближено заданими вихідними даними складає проміжний або остаточний етап. Основні проблеми обчислювальної математики відносяться дослідження і рішення лінійних алгебраїчних систем оцінки власних значень і власних векторів матриць, рішення систем нелінійних рівнянь, чисельного інтегрування початково задач для систем звичайних диференціальних рівнянь.Для большинства научных и инженерных задач моделирования на ЭВМ решение задач вычислительной математики с приближенно заданным исходным данным составляет промежуточный или окончательный этап. Основные проблемы вычислительной математики относятся исследования и решения линейных алгебраических систем оценки собственных значений и собственных векторов матриц, решение систем нелинейных уравнений, численного интегрирования начально задач для систем обыкновенных дифференциальных уравнений

ID Photograph hashing : a global approach

This thesis addresses the question of the authenticity of identity photographs, part of the documents required in controlled access. Since sophisticated means of reproduction are publicly available, new methods / techniques should prevent tampering and unauthorized reproduction of the photograph. This thesis proposes a hashing method for the authentication of the identity photographs, robust to print-and-scan. This study focuses also on the effects of digitization at hash level. The developed algorithm performs a dimension reduction, based on independent component analysis (ICA). In the learning stage, the subspace projection is obtained by applying ICA and then reduced according to an original entropic selection strategy. In the extraction stage, the coefficients obtained after projecting the identity image on the subspace are quantified and binarized to obtain the hash value. The study reveals the effects of the scanning noise on the hash values of the identity photographs and shows that the proposed method is robust to the print-and-scan attack. The approach focusing on robust hashing of a restricted class of images (identity) differs from classical approaches that address any imageCette thèse traite de la question de l’authenticité des photographies d’identité, partie intégrante des documents nécessaires lors d’un contrôle d’accès. Alors que les moyens de reproduction sophistiqués sont accessibles au grand public, de nouvelles méthodes / techniques doivent empêcher toute falsification / reproduction non autorisée de la photographie d’identité. Cette thèse propose une méthode de hachage pour l’authentification de photographies d’identité, robuste à l’impression-lecture. Ce travail met ainsi l’accent sur les effets de la numérisation au niveau de hachage. L’algorithme mis au point procède à une réduction de dimension, basée sur l’analyse en composantes indépendantes (ICA). Dans la phase d’apprentissage, le sous-espace de projection est obtenu en appliquant l’ICA puis réduit selon une stratégie de sélection entropique originale. Dans l’étape d’extraction, les coefficients obtenus après projection de l’image d’identité sur le sous-espace sont quantifiés et binarisés pour obtenir la valeur de hachage. L’étude révèle les effets du bruit de balayage intervenant lors de la numérisation des photographies d’identité sur les valeurs de hachage et montre que la méthode proposée est robuste à l’attaque d’impression-lecture. L’approche suivie en se focalisant sur le hachage robuste d’une classe restreinte d’images (d’identité) se distingue des approches classiques qui adressent une image quelconqu

Digital image watermarking using DWT basis matrices

This paper is devoted to image protection by means of computer steganography using wavelet techniques. Some research of the structure of the digital image is investigated, and we introduced its representation over basis images. Such basis images notation refers to orthogonal transform. We consider a set of wavelet basis images generated by orthogonal discrete wavelet transform and introduce a scheme for watermarking by embedding data to wavelet basis items

Robust image steganography method suited for prining = Robustna steganografska metoda prilagođena procesu tiska

U ovoj doktorskoj dizertaciji prezentirana je robustna steganografska metoda razvijena i prilagođena za tisak. Osnovni cilj metode je pružanje zaštite od krivotvorenja ambalaže. Zaštita ambalaže postiže se umetanjem više bitova informacije u sliku pri enkoderu, a potom maskiranjem informacije kako bi ona bila nevidljiva ljudskom oku. Informacija se pri dekoderu detektira pomoću infracrvene kamere. Preliminarna istraživanja pokazala su da u relevantnoj literaturi nedostaje metoda razvijenih za domenu tiska. Razlog za takav nedostatak jest činjenica da razvijanje steganografskih metoda za tisak zahtjeva veću količinu resursa i materijala, u odnosu na razvijanje sličnih domena za digitalnu domenu. Također, metode za tisak često zahtijevaju višu razinu kompleksnosti, budući da se tijekom reprodukcije pojavljuju razni oblici procesiranja koji mogu kompromitirati informaciju u slici [1]. Da bi se sačuvala skrivena informacija, metoda mora biti otporna na procesiranje koje se događa tijekom reprodukcije. Kako bi se postigla visoka razina otpornosti, informacija se može umetnuti unutar frekvencijske domene slike [2], [3]. Frekvencijskoj domeni slike možemo pristupiti pomoću matematičkih transformacija. Najčešće se koriste diskretna kosinusna transformacija (DCT), diskretna wavelet transformacija (DWT) i diskretna Fourierova transformacija (DFT) [2], [4]. Korištenje svake od navedenih transformacija ima određene prednosti i nedostatke, ovisno o kontekstu razvijanja metode [5]. Za metode prilagođene procesu tiska, diskretna Fourierova transformacija je optimalan odabir, budući da metode bazirane na DFT-u pružaju otpornost na geometrijske transformacije koje se događaju tijekom reprodukcije [5], [6]. U ovom istraživanju korištene su slike u cmyk prostoru boja. Svaka slika najprije je podijeljena u blokove, a umetanje informacije vrši se za svaki blok pojedinačno. Pomoću DFT-a, ???? kanal slikovnog bloka se transformira u frekvencijsku domenu, gdje se vrši umetanje informacije. Akromatska zamjena koristi se za maskiranje vidljivih artefakata nastalih prilikom umetanja informacije. Primjeri uspješnog korištenja akromatske zamjene za maskiranje artefakata mogu se pronaći u [7] i [8]. Nakon umetanja informacije u svaki slikovni blok, blokovi se ponovno spajaju u jednu, jedinstvenu sliku. Akromatska zamjena tada mijenja vrijednosti c, m i y kanala slike, dok kanal k, u kojemu se nalazi umetnuta informacija, ostaje nepromijenjen. Time nakon maskiranja akromatskom zamjenom označena slika posjeduje ista vizualna svojstva kao i slika prije označavanja. U eksperimentalnom dijelu rada koristi se 1000 slika u cmyk prostoru boja. U digitalnom okruženju provedeno je istraživanje otpornosti metode na slikovne napade specifične za reprodukcijski proces - skaliranje, blur, šum, rotaciju i kompresiju. Također, provedeno je istraživanje otpornosti metode na reprodukcijski proces, koristeći tiskane uzorke. Objektivna metrika bit error rate (BER) korištena je za evaluaciju. Mogućnost optimizacije metode testirala se procesiranjem slike (unsharp filter) i korištenjem error correction kodova (ECC). Provedeno je istraživanje kvalitete slike nakon umetanja informacije. Za evaluaciju su korištene objektivne metrike peak signal to noise ratio (PSNR) i structural similarity index measure (SSIM). PSNR i SSIM su tzv. full-reference metrike. Drugim riječima, potrebne su i neoznačena i označena slika istovremeno, kako bi se mogla utvrditi razina sličnosti između slika [9], [10]. Subjektivna analiza provedena je na 36 ispitanika, koristeći ukupno 144 uzorka slika. Ispitanici su ocijenjivali vidljivost artefakata na skali od nula (nevidljivo) do tri (vrlo vidljivo). Rezultati pokazuju da metoda posjeduje visoku razinu otpornosti na reprodukcijski proces. Također, metoda se uistinu optimizirala korištenjem unsharp filtera i ECC-a. Kvaliteta slike ostaje visoka bez obzira na umetanje informacije, što su potvrdili rezultati eksperimenata s objektivnim metrikama i subjektivna analiza

On Block Representations in Image Processing Problems

Any orthogonal transformation of the digital grayscale image can be represented by a set of images to be an orthonormal basis. For such representation digital data scattering was considered that is important in applications, particularly for the robust watermarking techniques. We introduce a block matrix, elements of which are basis images. This matrix is found to be useful for representation of multi-dimensional arrays, that can describe a set of digital images. This representation has new features concerning the data scattering. A steganographic scheme for frequency domain watermarking based on this representation is considered

On color-to-gray transformation for distributing color digital images

A new block embedding algorithm with a secret key is introduced for the Color-to-Gray and Back transformation. Color is embedded into the bit planes of the luminosity component of the YUV color space. We present an interface incorporated into Adobe Photoshop and consider a solution of the high quality digital image distribution problem. The solution is based on idea that the grayscale image with hidden color is a β version of a color original. Then a user could get a gray image before buying its color original he is interested. The proposed protocol has a secret key and can protect original images from unauthorized copying

Bayesian Dictionary Learning for Single and Coupled Feature Spaces

Over-complete bases offer the flexibility to represent much wider range of signals with more elementary basis atoms than signal dimension. The use of over-complete dictionaries for sparse representation has been a new trend recently and has increasingly become recognized as providing high performance for applications such as denoise, image super-resolution, inpaiting, compression, blind source separation and linear unmixing. This dissertation studies the dictionary learning for single or coupled feature spaces and its application in image restoration tasks. A Bayesian strategy using a beta process prior is applied to solve both problems. Firstly, we illustrate how to generalize the existing beta process dictionary learning method (BP) to learn dictionary for single feature space. The advantage of this approach is that the number of dictionary atoms and their relative importance may be inferred non-parametrically. Next, we propose a new beta process joint dictionary learning method (BP-JDL) for coupled feature spaces, where the learned dictionaries also reflect the relationship between the two spaces. Compared to previous couple feature spaces dictionary learning algorithms, our algorithm not only provides dictionaries that customized to each feature space, but also adds more consistent and accurate mapping between the two feature spaces. This is due to the unique property of the beta process model that the sparse representation can be decomposed to values and dictionary atom indicators. The proposed algorithm is able to learn sparse representations that correspond to the same dictionary atoms with the same sparsity but different values in coupled feature spaces, thus bringing consistent and accurate mapping between coupled feature spaces. Two applications, single image super-resolution and inverse halftoning, are chosen to evaluate the performance of the proposed Bayesian approach. In both cases, the Bayesian approach, either for single feature space or coupled feature spaces, outperforms state-of-the-art methods in comparative domains

Discrete Wavelet Transform (DWT) Based Dual Watermarking For Authentication And Copyright Protection

Digital media faces significant challenges related to unauthorized access, manipulation, and copyright infringement, necessitating effective authentication and copyright protection mechanisms. This thesis proposes a novel dual watermarking scheme based on the Discrete Wavelet Transform (DWT) to address these concerns. The primary objective of the proposed scheme is to provide robust copyright protection. A watermark, carrying ownership and copyright information, is embedded in the spatial domain using the DWT. This watermark acts as a digital signature, enabling the identification and tracing of the rightful owner of the content. The frequency domain embedding enhances the watermark's robustness against common attacks. In addition to copyright protection, the scheme incorporates a fragile watermark for authentication purposes. The fragile watermark is embedded in the least significant bit which is highly sensitive to any modifications or tampering. By extracting and comparing the fragile watermark, the integrity and authenticity of the content can be verified. Comprehensive experimental evaluations have been conducted to assess the performance of the proposed dual watermarking scheme. The results demonstrate its effectiveness in providing robust copyright protection and authentication capabilities. The scheme exhibits high imperceptibility, preserving the visual quality of the watermarked content, while ensuring a high level of sensitivity to unauthorized alterations