The ancient Greeks used steganography to conceal messages from prying eyes. Steganography comes from the Greek meaning "covered or hidden writing." It is the art and science of writing a hidden message that only the sender and receiver can read. The ancient art traces back to 440 B.C. The famous historian Herodotus mentions two cases in his Histories.

In the Histories Herodotus mentions Histiaeus, a king taken out of power by the Persians. Wishing to return to power, he sent a hidden message telling his people to revolt against the foreign occupation. Since the Persians controlled the region, then certainly any message of rebellion would be discovered if sent by messenger?

To hide his message Histiaeus shaved the head of his most trusted slave and tattooed his message onto the slave's head. When the slave's hair regrew the king sent the slave to deliver the message. When he arrived he shaved his head revealing the King's message.

He also tells the story of Demaratus, King of Sparta, who sent a message to Greece about the forthcoming attack by writing it on a wooden panel and covering it with wax. Wax tablets were used in that time as reusable writing surfaces, so no treachery was suspected. When the tablets reached their destination the wax was melted revealing the hidden message.

Generally a steganographic message will appear to be something else like a picture, an article, a grocery list etc. The advantage is that the hidden message does not draw attention to the sender or receiver, as a mass of jumbled letters will immediately arouse suspicion.

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