Scytales are one of the oldest forms of cryptography. 
The Spartans used scytales to transmit secret messages. 
Pictures taken at the International Spy Museum depicting how a scytale was used during Spartan military campaigns.
Many years ago, I visited the International Spy Museum in Washington, D.C. One of the most interesting exhibits talked about the history of espionage and the need for governments to keep sensitive information hidden to maintain national security.
Cryptography is the study of techniques used for secure communication. It comes from the Greek roots crypt- meaning secret, and -graphy, meaning to write. Cryptography literally means secret writing!
Scytales are the one of the oldest forms of cryptography. Scytale comes from the Greek word, skútalon, which means baton or cylinder.
Secret messages were written on parchment or leather that was wound around a cylinder of a particular size. The recipient of the message could only decode it by wrapping it around an identical cylindrical rod. Scytales were created and used by the Spartans during military campaigns.
The International Spy Museum is one of the secret treasures of Washington, D.C. If you ever get a chance to visit, I highly recommend it.
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