Education Stegonography

Steganography is the art of covered or hidden writing. The purpose of steganography is covert communication-to hide the existence of a message from a third party. This paper is intended as a high-level technical introduction to steganography for those unfamiliar with the field. It is directed at forensic computer examiners who need a practical understanding of steganography without delving into the mathematics, although references are provided to some of the ongoing research for the person who needs or wants additional detail. Although this paper provides a historical context for steganography, the emphasis is on digital applications, focusing on hiding information in online image or audio files. Examples of software tools that employ steganography to hide data inside of other files as well as software to detect such hidden files will also be presented. Even though steganography dealing with computer files is a relatively new concept, other forms of steganography have been around for quite some time. Ancient Greeks, when wishing to send a secret message, would sometimes write a message on a messengerÕs scalp, wait for the hair to grow back, and send that messenger to the receiver with the instructions to give this man a haircut. This is seen as a form of steganography since not only is the message itself virtually invisible underneath the manÕs hair, but the fact that a message exists at all is unknown to everyone. Should it leak out that message transfer was occurring in this way, then all that would need to be done to intercept these secret messages would be to shave the heads of all the passersby.

Another technique used in Ancient times that was a form of steganography was the use of tablets. Normal tablets are made out of wood with a wax coating. Anything that was to be inscribed on the tablets was written in the wax. To hide a message, the inscriber would write directly on the wood, then cover the whole thing with a fresh layer of wax. To the untrained eye, the tablet would then look like a fresh, new one. The receiver of the tablet would then have to know to scrape off the wax to retrieve the desired message. A third example of non-computer related steganography was that of spies during World War II. If a message were to be concealed, it would be written in a substance that would darken when heated, such as milk, lemon juice, or even urine. Once the paper was received, it would have to be knows to heat it up. Then, the secret message would appear. In all three of these examples, there is one key that is the most important part of the steganographic process. It has to be known that to receive the message, a manÕs head has to be shaven, or wax has to be removed, or a piece of paper needs to be heated up. Because these keys are unknown to everyone else, this process remains a very secure way of communication. Not just the message itself is hidden, but the way the message is concealed is a secret. This is the main concept of steganography, and today it applies to computer text files and images. steganography is a term used to describe files that have other types of files secretly embedded inside. Usually, when we talk about steganography, we mean the embedding of a text file, or a secret message, inside an image. Not only is the message itself hidden, but the fact that a message exists is hidden. It is in this way that steganography is a method of concealing the fact that communication is taking place in addition to actually concealing a file.