With the rapid development and popularity of information technology, criminals and mischievous computer users are given avenues to commit crimes and malicious activities. One of the commonly used tactics, called steganography, is to hide information under a cover media so that except participants, no one else knows the existence of such information. Many techniques have been proposed for hiding data in images, videos and audios, but there is not much research devoted to data hiding in the popular MS Office documents which have recently adopted Office Open XML (OOXML) format. In this research, we first focus on identifying several data hiding techniques for OOXML documents. Then, we design and develop a fast detection algorithm based on the unique internal structure of OOXML documents, which contains multiple XML files, by using multi-XML query technique. Experimental results show the proposed detection algorithm outperforms the traditional one in terms of detection speed and completeness, where performance is the key to success of detecting hidden data in OOXML documents due to the fact that millions of documents are generated and transferred over the internet every day. / UOIT

Un codi C rep el nom de Z2Z4-additiu si les seves coordenades es poden dividir en dos subconjunts X i Y , de tal manera que el codi punctured de C, obtingut en eliminar les coordenades que no es troben a X –o, respectivament, a Y – és un codi binari lineal – respectivament, un codi quaternari lineal–. La imatge del mapa de Gray de C és un codi binari i, sovint, no lineal, que s’anomena Z2Z4-lineal. Aquesta tesi presenta noves famílies de codis Z2Z4-additius, amb la particularitat que les seves imatges de Gray són codis Z2Z4-lineals que tenen els mateixos paràmetres i propietats que la coneguda família de codis de Reed-Muller binaris i lineals. També, tot considerant la classe de codis perfectes Z2Z4-lineals, els quals se sap que són completament regulars, es fan servir les construccions d’extensió, puncture, shorten i lifting, i s’estudia si els codis obtinguts són uniformement empaquetats o completament regulars. A més de proporcionar fiabilitat en els canals de comunicació, la teoria de codis s’ha aplicat recentment a l’esteganografia, és a dir, a la ciència d’ocultar informació confidencial dins d’altres missatges, aparentment inofensius –l’objecte recobridor–, de manera que terceres parts no puguin detectar l’esmentada informació. Aquest procés s’ha plantejat a la literatura modificant el bit menys significatiu dels símbols de l’objecte recobridor per transmetre el missatge secret (esteganografia binària), o bé modificant els dos bits menys significatius ( 1-esteganografia). Respecte a la 1-esteganografia, s’exposen dos nous mètodes d’embedding basats en codis perfectes Z2Z4-lineals, que assoleixen una taxa d’embedding més alta que amb altres mètodes ja coneguts, per una distorsió donada; mentre que es presenta un altre mètode, basat en el producte de dos o més codis de Hamming q-aris, conforme a l’esteganografia binària. / Un código C recibe el nombre de Z2Z4-aditivo si sus coordenadas se pueden dividir en dos subconjuntos X e Y , tales que el código punctured de C, obtenido a partir de eliminar las coordenadas que no están en X –o, respectivamente, en Y – es un código binario lineal –respectivamente, un código cuaternario lineal–. La imagen del mapa de Gray de C es un código Z2Z4-lineal, que es un código binario y, a menudo, no lineal. En esta tesis se presentan nuevas familias de códigos Z2Z4-aditivos, con la particularidad de que sus imágenes a través del mapa de Gray son códigos Z2Z4-lineales con los mismos parámetros y propiedades que la conocida familia de códigos de Reed-Muller binarios y lineales. Considerando la clase de códigos perfectos Z2Z4-lineales, los cuales se sabe que son completamente regulares, se han utilizado las construcciones de extensión, puncture, shorten y lifting, y estudiado si los códigos obtenidos en cada caso eran uniformemente empaquetados o completamente regulares. Además de proporcionar fiabilidad en los canales de comunicación, la teoria de códigos se ha aplicado recientemente a la esteganografía, es decir, a la ciencia de ocultar información confidencial en otros mensajes, aparentemente inofensivos –el objeto recubridor– de tal manera que dicha información no pueda ser detectada por terceros. Este proceso se ha planteado en la literatura modificando el bit menos significativo de los símbolos del objeto recubridor (esteganografía binaria), o bien modificando los dos bits menos significativos ( 1-esteganografía). Con respecto a la 1-esteganografía, se exponen dos nuevos métodos de embedding basados en códigos perfectos Z2Z4-lineales, que alcanzan una tasa de embedding superior a la de otros métodos anteriores, para una distorsión dada; mientras que se presenta otro método, basado en el producto de dos o más códigos de Hamming q-arios, conforme a la esteganografía binaria. / A code C is said to be Z2Z4-additive if its coordinates can be partitioned into two subsets X and Y , in such a way that the punctured code of C obtained by removing the coordinates outside X –or, respectively, Y – is a binary linear code –respectively, a quaternary linear code–. The Gray map image of C is a binary and often nonlinear code called Z2Z4-linear code. In this dissertation, new families of Z2Z4-additive codes are presented, with the particularity that their Gray map images are Z2Z4-linear codes having the same parameters and properties as the well-known family of binary linear Reed-Muller codes. Considering the class of perfect Z2Z4-linear codes, which are known to be completely regular, we have used the extension, puncture, shorten and lifting constructions, and studied the uniformly packed condition and completely regularity of the obtained codes. Besides providing reliability in communication channels, coding theory has been recently applied to steganography, i.e., the science of hiding sensitive information within an innocuouslooking message –the cover object– in such a way that third parties cannot detect that information. This hiding process has been addressed in the literature either by distorting the least significant bit of symbols in the cover object to transmit the secret message (binary steganography), or by distorting the two least significant bits ( 1-steganography). With respect to 1-steganography, two new embedding methods based on perfect Z2Z4- linear codes are introduced, achieving a higher embedding rate for a given distortion than previous methods; while another method, based on the product of more than two perfect q-ary Hamming codes, is presented conforming to binary steganography.

We present a novel data hiding method for compressed images. The method is designed to minimize the quality loss associated with data embedding into a JPEG image. The described technique uses the objective criterion such as the mean square error and the human visual system based criterion such as the Just Noticable Distortion metric for distortion minimization. The hiding method is designed under the restrictions of the JPEG compression standard to develop new image applications without any modifications or additions to the existing standard. An application example is presented in the thesis. The performance of the technique is examined at different image sizes and resolutions. The cost of hiding in terms of file length extension is examined. Some subjective experiments to determine the zero-perceived distortion hiding capacity are made. An application illustrating the usage of the technique is given. The described application embeds check-bits into JPEG images to facilitate the verification of the sender identity and the authenticity of the transmitted image. In this thesis, we give a list of requirements on the data hiding methods to implement standard compliant applications; design a provably good hiding method operating under these requirements; determine the critical performance points of the method and propose an application based on the method. We have performed some additional research to determine how our system works with high resolution images and existing other well-known algorithms for information hiding. The experiments on high-resolution images have shown that there exists a large embedding capacity for the high resolution images in spite of a loss of embedding density. The performance comparison experiments have shown that the spread spectrum technique offers a competitive but less efficient distortion performance.

Digital multimedia can be distributed via the internet efficiently with superior compression technologies. The chance of distributing digital intellectual properties, such as image, music, films, and software, being large-scale unauthorized copied and distributed are much increasing one possible and practical solution for the copyright protection is information hiding technology. Information hiding technology embeds a special data into multimedia data for copyright protection. However, the embedded data may be damaged by malicious attacks or common signal processing. In this thesis, an information hiding technique based on Fractal Orthonormal Basis is proposed. First, the original image is divided into NxN Range blocks, each range block is substituted by several Domain blocks (Fractal Orthonormal Basis), then the watermark information is embedded into the coefficients of the fractal orthonormal basis. Besides, our technique will be compare with the other two watermarking algorithm (using DCT and DWT). After the attacks of cropping, down-scaling, median filter, smoothing, noise, JPEG, SPIHT and EZW compression, the Fractal Orthonormal Basis watermarking technique shows better result of capacity, transparency and robustness. In addition, we only store parts of compression fractal codes and the permutation seed, and these can be the secret key for the security.

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ABSTRACT ROBUST DATA HIDING SCHEME WITH TURBO CODES &Uuml / NAL, BariS M.S., Department of Electrical And Electronics Engineering Supervisor: Prof. Dr. R&uuml / yal ERG&Uuml / L December 2005, 127 pages This study describes the design and implementation of a robust data hiding algorithm which is provided by turbo codes. As the digital technology grows up, it is getting easy to copy and distribute multimedia products without getting legal permission. This has forced researchers to study in digital watermarking areas. Along with watermarking researches, data hiding studies have gained interest in the last decade. Different watermark and data hiding algorithms have been proposed considering different requirements and properties such as robustness, fidelity, invisibility and data hiding capacity. In this thesis, robustness of watermarking systems and fidelity requirement in watermark models are considered and use of turbo codes is proposed with data embedding systems to improve system performance in terms of robustness. Fundamental watermarking algorithms in DCT domain are analyzed and simulated. Their performances in terms of robustness are presented. Data hiding algorithm which is based on projection and perturbation in transform domain is implemented in visual C. Then turbo codes are applied to this algorithm to improve system robustness. Improvement provided by turbo codes is demonstrated and compared with other discussed watermarking systems.

The first explored area in this thesis is the proposed data hiding method, TCQ-IS. The method is based on Trellis Coded Quantization (TCQ), whose initial state selection is arbitrary. TCQ-IS exploits this fact to hide data. It is a practical multi-dimensional that eliminates the prohibitive task of designing high dimensional quantizers. The strength and weaknesses of the method are stated by various experiments. The second contribution is the proposed data hiding method, Forbidden Zone Data Hiding (FZDH), which relies on the concept of &ldquo / forbidden zone&rdquo / , where host signal is not altered. The main motive of FZDH is to introduce distortion as much as needed, while keeping a range of host signal intact depending on the desired level of robustness. FZDH is compared against Quantization Index Modulation (QIM) as well as DC-QIM and ST-QIM. FZDH outperforms QIM even in 1-D and DC-QIM in higher dimensions. Furthermore, FZDH is comparable with ST-QIM for certain operation regimes. The final contribution is the video data hiding framework that includes FZDH, selective embedding and Repeat Accumulate (RA) codes. De-synchronization due to selective embedding is handled with RA codes. By means of simple rules applied to the embedded frame markers, certain level of robustness against temporal attacks is introduced. Selected coefficients are used to embed message bits by employing multi-dimensional FZDH. The framework is tested with typical broadcast material against common video processing attacks. The results indicate that the framework can be utilized in real life applications.

Common office documents provide significant opportunity for forensic and anti-forensic work. The Object Linking and Embedding 2 (OLE2) specification used primarily by Microsoft’s Office Suite contains unused or dead space regions that can be over written to hide covert channels of communication. This thesis describes a technique to detect those covert channels and also describes a different method of encoding that lowers the probability of detection. The algorithm developed, called OleDetection, is based on the use of kurtosis and byte frequency distribution statistics to accurately identify OLE2 documents with covert channels. OleDetection is able to correctly identify 99.97 percent of documents with covert channel and only a false positive rate 0.65 percent. The improved encoding scheme encodes the covert channel with patterns found in unmodified dead space regions. This anti-forensic technique allows the covert channel to masquerade as normal data, lowering the ability probability for any detection tool to is able to detect its presence.

Η προστασία των πνευματικών δικαιωμάτων και η απόδειξη γνησιότητας του κατόχου, επομένως και η πιστοποίηση της αυθεντικότητας των ψηφιακών αντικειμένων είναι ένα πολύ καυτό ζήτημα και για την επίλυσή του επιστρατεύονται μέθοδοι απόκρυψης πληροφορίας και τεχνικές υδατογράφησης. Εκτός από τη φιλοσοφική αντιμετώπιση του θέματος, προτείνονται μια μέθοδος απόκρυψης πληροφορίας και δύο τεχνικές υδατογράφησης, με σκοπό την προστασία των πνευματικών δικαιωμάτων και την πιστοποίηση της αυθεντικότητας των ψηφιακών αντικειμένων. Η μέθοδος απόκρυψης πληροφορίας δανείζεται έννοιες από την κρυπτογραφία εισάγοντας σε μεγάλες εικόνες ένα δύσκολο στιγμιότυπο, δηλαδή έναν τρία χρωματίσιμο γράφο. Ο γράφος μαζί με το χρωματισμό του αποτελεί το κλειδί. Για να μην αποκαλυφθεί όλος ο χρωματισμός του γράφου σε μια πιθανή διαμάχη, εφαρμόζεται το πρωτόκολλο των διαντιδραστικών αποδείξεων μηδενικής γνώσης (ZKIP) για δύσκολα υπολογιστικά προβλήματα. Η διαδικασία της ένθεσης γίνεται με χρήση του μετασχηματισμού wavelets, παρέχοντας καλή ποιότητα των παραγόμενων εικόνων και ανθεκτικότητα σε περιπτώσεις επιθέσεων. Οι δύο τεχνικές υδατογράφησης εφαρμόζονται στο χωρικό πεδίο και στο πεδίο συχνοτήτων, αντίστοιχα. Η τεχνική που εφαρμόστηκε στο χωρικό πεδίο εκμεταλλεύεται τυχόν ομοιότητες του υδατογραφήματος με τις αρχικές εικόνες για να επιλεγούν οι θέσεις ένθεσης. Αντίθετα στην τεχνική υδατογράφησης που εφαρμόστηκε στο πεδίο συχνοτήτων γίνεται χρήση του μετασχηματισμού wavelet. Σε όλες τις τεχνικές παρατηρήθηκαν ικανοποιητικά αποτελέσματα μετά την ένθεση της εισαγόμενης πληροφορίας έτσι ώστε να μη είναι οπτικά αντιληπτή. Επίσης εξετάστηκε και η ανθεκτικότητα της εισαγόμενης πληροφορίας στις εικόνες ύστερα από πιθανές επιθέσεις και επιβεβαιώθηκε ότι επιζεί ένα αρκετά μεγάλο ποσοστό της εισαγόμενης πληροφορίας, γεγονός που καταξιώνει τις προτεινόμενες μεθόδους. / The copyright protection and the authentication is a very hot topic and for its solution are called up data hiding methods and watermarking techniques. Αpart from the philosophical confrontation of the subject, there are proposed a data hiding method and two watermarking techniques that aim to copyright protect and the authenticate digital objects. The data hiding technique combines concepts from cryptography and it can be applied to large images by inserting a hard instance, i.e. a 3-colorable graph. The graph itself with its coloring compose the key. In order not to reveal all its coloring in a possible conflict, the Zero Knowledge Interactive Proof Protocol (ZKIP) is applied. The insertion process has been done using wavelets transformation, offering good quality of the produced images and robustness against possible attacks. The two watermarking techniques are applied in spatial domain and in frequency domain, respectively. The technique that was applied in spatial domain is exploiting any similarity between the watermark and the initial images so that to select at best the insertion positions. On the contrary, in the watermarking technique that is applied in the frequency domain, wavelets transformation has been used and the watermark was inserted in the differential coefficients of the image, in order to be imperceptible. To all the above techniques, it has been observed sufficient results after the insertion of the redundant information, so that it turned to be visible imperceptibly. Moreover, the robustness of the redundant information was each time after possible attacks examined, and it was confirmed that a rather big percentage of the redundant information is survived, making more reliable the proposed techniques.