Steganography

:This article is about steganography (hidden writing), not to be confused with stenography (shorthand).

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Steganography is the art and science of writing hidden messages in such a way that no one apart from the intended recipient knows of the existence of the message; this is in contrast to cryptography, where the existence of the message itself is not disguised, but the meaning is obscured. "Steganography" is a Greek word and means covered or hidden writing. Its origins can be traced back to 440 BC. Herodotus mentions two examples of Steganography in The Histories of Herodotushttp://www.cl.cam.ac.uk/~fapp2/publications/ieee99-infohiding.pdf. Demeratus sent a warning about a forthcoming attacks to Xerxes by writing it on a wooden panel and covering it in wax. The second example is Histaeus who shaved the head of his most trusted slave and tattooed a message on his head. After his hair had grown the message was hidden. The purpose was to instigate a revolt against the Persians. Later, Johannes Trithemius's book Steganographia is a treatise on cryptography and steganography disguised as a book on black magic.

Related Topics:
Cryptography - Herodotus - The Histories of Herodotus - Johannes Trithemius - Black magic

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Generally a steganographic message will appear to be something else: a picture, an article, a shopping list, or some other "cover" message. Recent trends include steganographic coding inside of a transport layer such an MP3 file or a protocol such as UDP.

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Steganographic messages are often first encrypted by some traditional means, and then a covertext is modified in some way to contain the encrypted message, resulting in stegotext. For example, the letter size, spacing, typeface, or other characteristics of a covertext can be manipulated to carry the hidden message; only the recipient (who must know the technique used) can recover the message and then decrypt it. Francis Bacon is known to have suggested such a technique to hide messages.

Related Topics:
Encrypted - Typeface - Francis Bacon

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