NOSTEGA: A NOVEL NOISELESS STEGANOGRAPHY PARADIGM
Creators: name: Desoky, Abdelrahman
Publisher: name: Maryland Shared Open Access Repository
Year: 2009
Subjects: Covert Communications
Image Steganography
Information Hiding
Linguistic Steganography
Steganography
Text Steganography

description: Steganography is the science and art of covert communications and involves two  procedures. First, the required message is concealed in a particular carrier, e. g. image,  audio, text, etc., that is called a steganographic cover. The second procedure is  concerned with transmitting the cover to the message recipient without drawing  suspicion. Fundamentally, the steganographic goal is not to hinder the adversary from  decoding a hidden message, but to prevent an adversary from suspecting the existence  of covert communications. When using any steganographic technique if suspicion is  raised, the goal of steganography is defeated regardless of whether or not a plaintext  is revealed. Contemporary steganography approaches camouflage data as noise in a  cover that is assumed to look innocent. For example, the encoded message can be  embedded as alteration of digital images, audio files, text, etc., without noticeable  degradation. However, such alteration of authenticated covers can raise suspicion and  makes the message detectable. Another example is when linguistics, e. g., using  synonymous words, is exploited as a means to conceal a message, causing the  presence of abnormal and sometimes weird sentences in a text that become  discernable by human and machine examinations. The presence of such unjustifiable  noise draws attention and unravels the hidden communications.  This dissertation introduces a novel Noiseless Steganography Paradigm  ( Nostega). Nostega neither hides data in a noise nor produces noise. Instead, it  camouflages messages in a form of unquestionable data in the generated cover. In  addition, steganography approaches found in the literature have focused on how to  conceal a message and not on how to camouflage its transmittal. Nostega addresses  such shortcoming by not only camouflaging a message but also its transmission.  Thus, Nostega is a novel paradigm in steganography research. In Nostega, the  steganographical goal is achieved by determining a suitable domain that is capable of  generating an unsuspicious steganographic cover in which a message intrinsically is  embedded in a form of innocent data that is compatible with the chosen domain. In  addition, Nostega establishes a covert channel by employing the selected domain to  serve as a justification for the interaction and delivering the cover among the  communicating parties.  A number of Nostega- based methodologies are presented. The first  methodology, a novel cover type, namely graph- cover, is introduced. Unlike image,  audio, and text based steganographic covers, graphs enable data hiding in a plotted  graph. Graph covers fit very well with Nostega and are suitable for many domains.  The second methodology pursues popular games such as chess, checkers, crosswords,  domino, etc., to conceal messages. Meanwhile, the third methodology pursues the  linguistics path to generate text- cover. It exploits educational documents as  steganographic covers by manipulating mainly, but not limited to, questions and  answers. This methodology can employ exam generators and text substitution  techniques to automate the process of cover generation. Finally, the fourth  methodology is also a linguistic steganography type that conceals messages by  manipulating automatic summarization techniques to conceal data in textual  summaries. Implementation and steganalysis validation of these methodologies are  presented.