Please note: This is a work in progress.
Throughout history, humankind has used various methods to hide information in a non-secret message. This practice is known as steganography, which stems from a combination of the Greek words
στεγανός (watertight) and
γραφή (writing), meaning covered writing.
In this article, I will be using the common placeholder names, Alice, Bod & Eve (Eavesdropper), when things start to get a little complicated.
Alice --------------------------> Bob | | | Eve
The earliest documented use of steganography is found in Herodotus’ Histories. Herodotus mentions several various methods. In the first instance, a war was about to take place between Cyrus the Great and King Astyages of Medes. The primary general of King Astyages, Harpagus, wanted to notify Cyrus the Great, that he would support him in the war, because the Median King had fed him his own son. In order to notify Cyprus, Harpagus had to hide a message in the belly of a hare 🐇, carried by a messenger disguised as a hunter.
“So much being ready and done, Harpagus wanted to reveal his intent to Cyrus, who then lived among the Persians. But the roads were guarded, and he had no plan for sending a message but this: he carefully slit the belly of a hare, and then leaving it as it was without further harm he put into it a paper on which he wrote what he thought best. Then he sewed up the hare’s belly, and sent it to Persia by the most trusted of his servants, giving him nets to carry as if he were a huntsman. The messenger was instructed to give Cyrus the hare and tell him by word of mouth to cut it open with his own hands, with no one else present.”
In book V , Herodotus mentions another intriguing way of hiding a message. In 499 BC, Histiaeus, the tyrant of Miletus, pricked a secret message into the shaven head of his most trusted slave. Once his hair had grown back, he sent him to his son-in-law, Aristagoras.
“For Histiaeus, when he was anxious to give Aristagoras orders to revolt, could find but one safe way, as the roads were guarded, of making his wishes known; which was by taking the trustiest of his slaves, shaving all the hair from off his head, and then pricking letters upon the skin, and waiting till the hair grew again.”
 - Godley, A. D. “Herodotus, The Histories.” Herodotus, The Histories, Book 5, chapter 37, section 1. (July 23, 2016).
 - Rawlinson, George. “The Internet Classics Archive - The History of Herodotus by Herodotus.” The Internet Classics Archive - The History of Herodotus by Herodotus. (July 23, 2016).