C r y p t o l o g y : S t e g a n o g r a p h y
The only good is knowledge, and the only evil is ignorance.

- Herodotus

Steganography is the art and science of hiding the existence of a message.

Steganalysis is the art and science of detecting a hidden message.

Stegosaurs were herbivourous dinosaurs of the Jurassic and Early Cretaceous. It is highly unlikely that they used cryptography.
Stego in Literature
Herodotus of Halikarnassos (present day Turkey) lived around 500 BCE. A well-travelled historian and storyteller, he wrote an account of his observations in The Histories of Herodotus. In The Histories, Herodotus describes two incidents involving steganography:

Demaratos warned the Lacedemonians about an impending attack by writing the warning on a wooden tablet and covering it in wax. When the wax tablet reached the Lacedemonians, they scraped the wax off and read the warning.

Another incident involves Histiaios who sent a signal to Aristagoras that he should revolt against the Persians. Histiaos shaved the head of his most trusted slave and tattooed a message on it. As soon as the hair had grown back, the slave was sent to Aristagoras.

Neither of the above incidents described by Herodotus involve any encryption. However, the messages are concealed before being sent. Upon receiving the messages, the recipients have to extract the hidden messages before they can read them.

In both incidents, the only protection mechanism is the fact that the message's existence is a secret. Once discovered, the message could be easily read. So the emphasis is on clever concealment of the message, rather than encryption mechanisms.
The nineteenth century American writer Edgar Allan Poe was an avid cryptographer. His works include that gem of cryptography fiction: The Gold Bug.

In Poe's The Purloined Letter, the police are looking for a blackmail note that is in plain sight. It isn't hidden, is is just sitting among the ordinary correspondence on the desk. For that reason, the police don't bother to examine it.

Clark Kent is Superman hiding behind a pair of glasses and a lack of motor coordination.

In the digital age, steganography still operates under the same premise: Hide the fact that the message exists. You can hide a message or a file inside a picture, movie or sound file. Digital watermarking is a form of steganography.

Related Topics
Herodotus More detailed page about the two steganography-related stories in The Histories of Herodotus.

External Links
The Histories of Herodotus vol 1 Text at Project Gutenberg
The Histories of Herodotus vol 2 Text at Project Gutenberg
Stegoarchive.com Great collection of free and commercial steganography tools. Also has a selection of steganalysis tools.
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