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c. 700 BCE
“During Roman times, Sparta’s military needed to send messages over long distances. To be useful, the messages had to travel fast, which meant that they couldn’t be transported by a large, slow-moving battalion. And the messages needed to remain secret, in case they were intercepted.
To protect its messages, the military devised a secure communications system involving two wooden staffs of identical diameter and a strip of parchment. Two parties needing to communicate each would have a single staff. To create a message, the sending party would wrap the parchment around his staff and then write a message across; when the parchment was unwrapped, the message would be scrambled. At the other end, the recipient would wrap the message around his staff, and the message would be legible once again.
The scytale is mentioned in the writings of Archilochus, a Greek poet who lived from 680 BCE to 645 BCE. Today, nearly every modern cryptography textbook features a description of the scytale. Although there are examples of cryptography and encipherment from ancient Egypt, Mesopotamia, and Judaea, the scytale is the first example of a cryptographic device—with the diameter of the staff being akin to the encryption key. (A key is a secret—typically a word, number, or phrase—that controls the encryption algorithm. The key determines how the message is encrypted; for most encryption algorithms, the same key is used to decrypt the encrypted message. Thus, keeping the key secret is critical to message security.)
But while the writings of Archilochus certainly do mention a scytale as a means of communication, references to it as an encryption device do not appear until nearly 700 years later, in the writings of Plutarch.
Another encryption cipher from the ancient world was Julius Caesar’s cipher, used in the first century BCE by the general to scramble military communications. Several hundred years later, the Kama Sutra, by Vatsyayana, advised men and women to know how to compose and read secret messages.
SEE ALSO On Deciphering Cryptographic Messages (c. 850), Vernam Cipher (1917)
A scytale uses parchment wrapped around a cylinder to encrypt a message; the recipient wraps the message around a cylinder of the same diameter to read the coded content.”