Browsing by Subject "Steganography"
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Item Defenses against Covert-Communications in Multimedia and Sensor Networks(2012-11-29) Jainsky, Julien Sebastien 1981-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.Item Steganoscription : exploring techniques for privacy-preserving crowdsourced transcription of handwritten documents(2014-05) Smith, Dustin Lee; Karadkar, Unmil; Galloway, PatThe focus my research is the historical document format represented by the Central State Hospital (CSH) dataset, handwritten medical records. The specific problem innate to the CSH dataset in question is how to transcribe sensitive, cursive-handwritten documents via a manual vehicle- such as crowdsourcing. Manual methods are necessarily no matter the sophistication of the optical character recognition system used because of the inconsistencies within cursive script. To address this problem I've developed an application that enables users to transcribe sensitive, handwritten, document images while preserving the privacy of the context around the transcribed text via random word selection and visual manipulation of the displayed text. This is made possible through several algorithms that process documents from a top-down approach. These system operations detect and segment lines of text in images, reverse the slant common to cursive script, detect and segment words, and finally, manipulate word-images before they are displayed to users; combinations of color, noise, and geometric manipulations are currently supported and used randomly. This system, called Steganoscription, combines the concepts of steganography and transcription.