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History of cryptography: the scitala

The scitala or scital (in ancient Greek: σκυτάλη, skytàlē, “stick”) is traditionally considered an encrypted and secret message that was sent by the ephors, the five supreme magistrates of Sparta, to the generals and navarchs engaged in military expeditions.

It is one of the oldest known methods of encryption by transposition: the coding mechanism allowed, if the scitala had been intercepted by the enemy, to keep the content of the message secret and, at the same time, allowed the recipient to verify its authenticity, as only those who were equipped with a wand identical to the one used by the sender to prepare the scitala that could decipher and read the message.

However, some modern scholars have questioned the cryptographic use of the scitala, arguing that it was instead used as an unencrypted communication system.

 

Scitala: description and use

Plutarch accurately describes the functioning of the scitala in the Life of Lysander, where he specifies that this term meant both the parchment with the message and the wand that was used for its writing and deciphering.

Before writing the message, the ephors prepared a long, narrow strip of parchment and wound it in a spiral around a wand, which was the same in length and diameter as another wand that the magistrates had previously provided to the recipient.

After having made the parchment adhere to the stick, taking care not to leave any space in which the wood was visible and at the same time avoiding overlapping different edges of the parchment itself, the ephors proceeded to write the message.

Then, the ephors unwound the strip from the wand and send it to their emissary via a messenger.

If he had been intercepted during his journey, the message would have been incomprehensible as it was made up of letters that could not be connected.

Only the recipient, on the other hand, having a stick identical to the one in the hands of the ephors, could rewind the parchment around it and reconstruct the original position of the letters and understand the content of the message.

 

The scitala of Farnabazo

Plutarch tells of the sending of a scitala to Lysander with which the ephors immediately recalled him to Sparta to justify the looting and raids he had carried out in the Persian satrapy of Farnabazo II, where he was at that moment.

According to Plutarch’s story, the Navarch, having received the message, was seized by a great agitation and asked Farnabazo to write a letter to the ephors in which he justified his actions.

Farnabazo, very cunningly, wrote the letter as the navarch wanted but at the last moment he replaced it with another, which he had written in secret, in which he openly accused Lysander.

The latter returned to Sparta with the letter from Farnabazo, presented himself to the five magistrates convinced that he had no problems but the ephors, once they had read the message delivered to them by the navarch himself, made him read it in turn and leaving him dismayed.

A very similar description of the scitala is also provided by Aulus Gellius and the lexicon Suida, which recalls that the scitala was also used by the Spartans who gave money on loan who, after having divided it into two parts, wrote the contract on each one and gave one of the two parties to the witnesses.

 

Ancient testimonies and modern hypotheses

Although Plutarch and Aulus Gellius present scitala as an encrypted communication system, other ancient authors use the term as a synonym for non-coded message.

In the Life of Agesilaus, Plutarch again uses the term Scythian to describe the order sent to Agesilaus to take command of the fleet; the same episode is also remembered by Xenophon, who however does not refer to the encrypted message.

Similarly, in the Life of Alcibiades Plutarch speaks of a message transmitted by script from the ephors to Alcibiades, but in a parallel passage Thucydides does not mention the encryption system.

Thucydides himself testifies to the sending of a scitala (without specifying whether the message was encrypted) to Pausanias, the winner of the battle of Plataea, to recall him home from the Troad, where he was after the conquest of Byzantium (471 BC), so that could answer for the accusations of treason that were brought against him and from which he was later acquitted.

The message from the scitala said to report immediately to Sparta, otherwise he would be declared a public enemy.

Due to these divergences, some modern scholars have hypothesized that both Plutarch and Aulus Gellius have misunderstood the use of the scitala, which originally would have had no encryption functionality; the origin of the error could be Apollonio Rodio, who, according to Athenaeus of Naucrati, discussed the use of this instrument in the lost work Su Archilochus.

 

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