The growing popularity of the Internet and multimedia methods have sparked an ever increasing interest in hiding data [with] in digital media (Wang). Many of the methods that have been used to protect copyrighted materials such as audio, video, images, and text, have focused primarily on watermarking. However embedding data within data has also proved useful for concealed communication, or stegonagraphy. This paper will address in further detail what stegonagraphy is, and the various techniques that are utilized.
Stegonagraphy is a form of hidden communication that literally means covered writing (Niklasson). The message itself is left in plain view for all to see, but goes unnoticed because the very existence of there even being a message is secret. One popular expression used to describe this method is hidden in plain sight, experts refer to this as Security through Obscurity (Duraiswamy). This is of course in distinction to cryptography where the message is actually scrambled, and the data left virtually unintelligible (encryption) to the eavesdropper even though the existence of a message is often times known beforehand.
It is also important to note that watermarking and stegonagraphy differ as well. Stegonagraphic information must never be evident to a viewer unaware of its presence. Modern stegonagraphy should only be detectable if secret information is known i.e. a secret key, whereas this key feature is optional when referring to watermarking.
Also compared to watermarking, stegonagraphy has drawn less attention until recently, as computer specialists, signal-processing researchers, and multimedia product vendors concerned about information security have recognized that illicit use of the technique might become a threat to the security of the worldwide information infrastructure (Wang).This key piece of information has prompted research to study steganalysis, or the detection of embedded data.
Many times throughout history encrypted messages have been intercepted but not decoded. While this protects the hidden information from being discerned by the enemy, an intercepted message also alerts the enemy that someone is trying to communicate with someone else. Stegonagraphy on the other hand, takes the opposite approach and attempts to hide all evidence that communication is even taking place. Images are the most popular cover media for stegonagraphy and can be stored in a straightforward bitmap format such as BMP or in a compressed format such as JPEG(Kipper). As described above this is achieved through hiding a message within another message but doing s it in such a way that the compound message appears to be a normal graphic, video, or sound file. Some of the popular techniques that implement stegonagraphy such as microdots, semagrams, anamorphosis and invisible ink are described below:
One implementation of stegonagraphy is the microdot. The microdot is a page-sized photograph that has been...