Steganography is the act of hiding messages, so that no one but the person it is for knows a message is even there to be read. Today messages can be hidden digitally, for example in digital pictures and music, but the idea of Steganography dates back to the Ancient Greeks.
The earliest know use of steganography was by the Greek Despot, Histiaeus. He ruled an area of Iona (part of modern Turkey) called Miletus, but for the Persian King of Kings, Darius the Great. As a result of his wisdom and loyalty to Darius in previous battles, Histiaeus left Iona to become Darius’ personal advisor. While away he left his own kingdom in the control of his nephew Asistagoras. However, rather than stay loyal to Darius, he actually plotted to overthrow the Persian’s in Iona as he wanted to become overall King of Miletus, himself.
Histiaeus’ plan was to get his nephew Asistagoras to do the dirty work and rise up against the Persians in Iona, while he was with Darius. He needed to send a message to tell him to do this, without any risk of it being read by those loyal to Darius. To do this he used the head of a slave!
He shaved the slave’s hair off, tattooed a message on his bald head and then let the hair grow back. Once the message was hidden, the slave travelled back to Miletus where he shaved his head again, allowing Asistagoras to read the message that told him to revolt against the Persians. Once the revolt started, Histiaeus persuaded Darius to let him return there supposedly to take back control form his errant nephew.
However, while Darius trusted him, others suspected Histiaeus was actually behind the plot. Ultimately, he was captured in battle by a Persian general, loyal to Darius. The city of Miletus was ultimately destroyed too. As the general was worried Darius might pardon Histiaeus, he beheaded him on the spot. His head was sent to Darius, this time a head being used as a very open message to say that Histiaeus was both a traitor and dead. Darius still refused to believe he had been betrayed by his friend, however.
It may have led to a grisly end, but, the steganography had at least worked to keep the original message secret.