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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Defenses against Covert-Communications in Multimedia and Sensor Networks

Jainsky, Julien Sebastien 1981- 14 March 2013 (has links)
Steganography and covert-communications represent a great and real threat today more than ever due to the evolution of modern communications. This doctoral work proposes defenses against such covert-communication techniques in two threatening but underdeveloped domains. Indeed, this work focuses on the novel problem of visual sensor network steganalysis but also proposes one of the first solutions against video steganography. The first part of the dissertation looks at covert-communications in videos. The contribution of this study resides in the combination of image processing using motion vector interpolation and non-traditional detection theory to obtain better results in identifying the presence of embedded messages in videos compared to what existing still-image steganalytic solutions would offer. The proposed algorithm called MoViSteg utilizes the specifics of video, as a whole and not as a series of images, to decide on the occurrence of steganography. Contrary to other solutions, MoViSteg is a video-specific algorithm, and not a repetitive still-image steganalysis, and allows for detection of embedding in partially corrupted sequences. This dissertation also lays the foundation for the novel study of visual sensor network steganalysis. We develop three different steganalytic solutions to the problem of covert-communications in visual sensor networks. Because of the inadequacy of the existing steganalytic solutions present in the current research literature, we introduce the novel concept of preventative steganalysis, which aims at discouraging potential steganographic attacks. We propose a set of solutions with active and passive warden scenarii using the material made available by the network. To quantify the efficiency of the preventative steganalysis, a new measure for evaluating the risk of steganography is proposed: the embedding potential which relies on the uncertainty of the image’s pixel values prone to corruption.
2

Digitální steganografie a stegoanalýza / Digital Steganography and Steganalysis

Poremba, Tomáš January 2018 (has links)
This thesis deals with digital steganography and steganalysis. It explains the significance of both disciplines and gives a brief overview of the history in the given fields. The paper separates existing steganographic and steganalytic methods and describes the attributes of various branches of steganography. With respect to the chosen field of steganography (the image steganography), the paper narrows down the set of suitable steganographic and steganalytic methods, whose features are then described in detail. The results of the thesis inlcude experiments that verify the features of chosen steganographic methods and evaluation of steganalytic methods and their success in detection of steganography.
3

Applications possibles de la stéganographie sur la compression d’image et l’estimation du regard de l’oeil humain

Jafari, Reza January 2014 (has links)
La recherche présentée dans cette thèse est divisée en trois parties. Notre objectif dans la première partie est l’amélioration de la compression de l’image par stéganographie. Dans cette étude, la compression de données est effectuée en deux étapes. Tout d’abord, nous profitons du compactage d’énergie en utilisant JPEG pour réduire les données redondantes. Ensuite, nous intégrons des blocs de bits dans les blocs suivants de la même image stéganographie. Les bits intégrés servent à non seulement augmenter la taille du fichier de l’image compressée, mais aussi à diminuer davantage la taille du fichier. Les résultats expérimentaux montrent que notre méthode donne de meilleurs taux de compression tout en conservant une haute qualité de l’image. Le deuxième sujet de cette thèse propose un formalisme bayésien pour la stéganalyse d’image numérique qui permet la détection d’images stego, l’identification de l’algorithme de stéganographie utilisé, l’estimation de la longueur du message et l’emplacement, et l’anticipation dans le cas de l’intégration en utilisant un algorithme de stéganographie inconnu. La détection, l’identification et l’anticipation impliquent l’apprentissage discriminant dans l’espace des fonctions. L’estimation nécessite la fusion de classificateurs permettant la discrimination entre les sous-images et une intégration entière des couvertures de tailles différentes. La validation sur des images JPEG montre que le système proposé est efficace et permet d’anticiper des algorithmes de stéganographie inconnus. Le troisième sujet de la thèse décrit une méthode d’estimation du regard de l’oeil humain pendant un mouvement normal de la tête. Dans ce procédé, la position et l’orientation de la tête sont acquises par des données de profondeur fournies par Kinect. La direction de l’oeil est obtenue à partir d’images à haute résolution. Nous nous proposons la régression logistique multinomiale pour construire une fonction de mappage du regard et de vérifier l’état de l’iris. L’efficacité de la méthode proposée est validée par une évaluation de la performance pour plusieurs personnes avec différentes distances et poses par rapport à la caméra et dans différents états de l’oeil.
4

H.264 encoded digital video protection using temporal redundancy LSB steganography

Mitchell, Scott January 2018 (has links)
A steganographic method was developed based on the temporal redundancies present in digital video streams, these redundancies are utilised by the H.264 encoding standard to reduce the bandwidth requirements of a digital video stream while maintaining content quality. The temporal redundancies are used to steganographically embed unique binary data within the digital video stream, this results in a unique embedding strategy within each video stream while also utilising areas that reduce the potential data loss experienced during the H.264 encoding process. The effectivness of the developed steganographic method is measured using the common steganographic metrics of Payload Capacity, Embedded Data Robustness and Media Impact. The results illustrate that the compensation of mutative factors in the embedding process using temporal redundancies result in a more robust method of data embedding within digital video encoded using H.264.
5

Applications possibles de la stéganographie sur la compression d’image et l’estimation du regard de l’oeil humain

Jafari, Reza January 2014 (has links)
La recherche présentée dans cette thèse est divisée en trois parties. Notre objectif dans la première partie est l’amélioration de la compression de l’image par stéganographie. Dans cette étude, la compression de données est effectuée en deux étapes. Tout d’abord, nous profitons du compactage d’énergie en utilisant JPEG pour réduire les données redondantes. Ensuite, nous intégrons des blocs de bits dans les blocs suivants de la même image stéganographie. Les bits intégrés servent à non seulement augmenter la taille du fichier de l’image compressée, mais aussi à diminuer davantage la taille du fichier. Les résultats expérimentaux montrent que notre méthode donne de meilleurs taux de compression tout en conservant une haute qualité de l’image. Le deuxième sujet de cette thèse propose un formalisme bayésien pour la stéganalyse d’image numérique qui permet la détection d’images stego, l’identification de l’algorithme de stéganographie utilisé, l’estimation de la longueur du message et l’emplacement, et l’anticipation dans le cas de l’intégration en utilisant un algorithme de stéganographie inconnu. La détection, l’identification et l’anticipation impliquent l’apprentissage discriminant dans l’espace des fonctions. L’estimation nécessite la fusion de classificateurs permettant la discrimination entre les sous-images et une intégration entière des couvertures de tailles différentes. La validation sur des images JPEG montre que le système proposé est efficace et permet d’anticiper des algorithmes de stéganographie inconnus. Le troisième sujet de la thèse décrit une méthode d’estimation du regard de l’oeil humain pendant un mouvement normal de la tête. Dans ce procédé, la position et l’orientation de la tête sont acquises par des données de profondeur fournies par Kinect. La direction de l’oeil est obtenue à partir d’images à haute résolution. Nous nous proposons la régression logistique multinomiale pour construire une fonction de mappage du regard et de vérifier l’état de l’iris. L’efficacité de la méthode proposée est validée par une évaluation de la performance pour plusieurs personnes avec différentes distances et poses par rapport à la caméra et dans différents états de l’oeil.
6

Automated Detection of Semagram-Laden Images

Cerkez, Paul 01 January 2012 (has links)
Digital steganography is gaining wide acceptance in the world of electronic copyright stamping. Digital media that are easy to steal, such as graphics, photos and audio files, are being tagged with both visible and invisible copyright stamp known as a digital watermark. However, these same methodologies are also used to hide communications between actors in criminal or covert activities. An inherent difficulty in developing steganography attacks is overcoming the variety of methods for hiding a message and the multitude of choices of available media. The steganalyst cannot create an attack until the hidden content method appears. When a message is visually transmitted in a non-textual format (i.e., in an image) it is referred to as a semagram. Semagrams are a subset of steganography and are relatively easy to create. However, detecting a hidden message in an image-based semagram is more difficult than detecting digital modifications to an image's structure. The trend in steganography is a decrease in detectable digital traces, and a move toward semagrams. This research outlines the creation of a novel, computer-based application, designed to detect the likely presence of a Morse Code based semagram message in an image. This application capitalizes on the adaptability and learning capabilities of various artificial neural network (NN) architectures, most notably hierarchical architectures. Four NN architectures [feed-forward Back-Propagation NN (BPNN), Self organizing Map (SOM), Neural Abstraction Pyramid (NAP), and a Hybrid Custom Network (HCN)] were tested for applicability to this domain with the best performing one being the HCN. Each NN was given a baseline set of training images (quantity based on NN architecture) then test images were presented, (each test set having 3,337 images). There were 36 levels of testing. Each subsequent test set representing an increase in complexity over the previous one. In the end, the HCN proved to be the NN of choice from among the four tested. The final HCN implementation was the only network able to successfully perform against all 36 levels. Additionally, the HCN, while only being trained on the base Morse Code images, successfully detected images in the 9 test sets of Morse Code isomorphs.
7

Data hiding and detection in Office Open XML (OOXML) documents

Raffay, Mohammad Ali 01 March 2011 (has links)
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
8

On additive binary nonlinear codes and steganography

Ronquillo Moreno, Lorena 11 May 2012 (has links)
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.
9

Steganalysis of video sequences using collusion sensitivity

Budhia, Udit 16 August 2006 (has links)
In this thesis we present an effective steganalysis technique for digital video sequences based on the collusion attack. Steganalysis is the process of detecting with a high probability the presence of covert data in multimedia. Existing algorithms for steganalysis target detecting covert information in still images. When applied directly to video sequences these approaches are suboptimal. In this thesis we present methods that overcome this limitation by using redundant information present in the temporal domain to detect covert messages in the form of Gaussian watermarks. In particular we target the spread spectrum steganography method because of its widespread use. Our gains are achieved by exploiting the collusion attack that has recently been studied in the field of digital video watermarking and more sophisticated pattern recognition tools. Through analysis and simulations we, evaluate the effectiveness of the video steganalysis method based on averaging based collusion scheme. Other forms of collusion attack in the form of weighted linear collusion and block-based collusion schemes have been proposed to improve the detection performance. The proposed steganalsyis methods were successful in detecting hidden watermarks bearing low SNR with high accuracy. The simulation results also show the improved performance of the proposed temporal based methods over the spatial methods. We conclude that the essence of future video steganalysis techniques lies in the exploitation of the temporal redundancy.
10

STEGANOGRAPHIC COVERT COMMUNICATION CHANNELS AND THEIR DETECTION

Amiruzzaman, Md 13 July 2011 (has links)
No description available.

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