Nostega: a novel noiseless steganography paradigm

• Authors: Mohammed Younis;Abdelrahman Desoky
• Venue: Nostega: a novel noiseless steganography paradigm
• Year: 2009

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.