Introduction to Steganography: Hiding in Plain Sight

Steganography, the science of hiding secret messages within publicly accessible material, is an ancient science. One of the first accounts of steganography in action dates back to the Greek historian Herodotus. In the fifth century BCE he documented the story of Demeratus, who struggled to find a way of alerting Sparta that the Persian Great King Xerxes was gearing up to invade Greece. Knowing that any overt message would be intercepted easily by the Persians, he scraped off the wax surface of a wooden writing tablet and scratched his warning into the underlying wood. Demeratus then re-coated the tablet with a fresh layer of wax, thus allowing the apparently blank writing tablet to be carried off to Sparta without arousing suspicion.

In the modern world, steganography simply takes one piece of information and hides it within another electronically. Computer files (images, sounds recordings, even disks) contain unused or insignificant areas of data. Steganography takes advantage of these areas, replacing them with information (encrypted mail, for instance). The files can then be exchanged without anyone knowing what really lies inside of them. An image of the space shuttle landing might contain a private letter to a friend. A recording of a short sentence might contain your company's plans for a secret new product. Steganography can also be used to place a hidden "trademark" in images, music, and software, a technique referred to as watermarking.

The issues that surround steganography are quite similar to the controversy that surrounded and still continues to surround another similar field, that of publicly available strong encryption. The encryption debate has revolved around issues of industrial competitiveness, personal privacy, and the interests of national security and law enforcement.

The main reason we chose to examine this one particular area was linked to our mutual fascination with encryption and security issues in general. Also, the large amount of media attention it has received in the recent past in conjunction with 9/11 has caused much concern in the uninformed public.

Goals

The main goal of this project was to investigate the history and various approaches to steganography and see how hard it would be to create a simple, first generation electronic stegonographic program that allows the user to embed text in an image as well as to investigate the legal and social issues surrounding this topic.

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