A ‘Rusty’ Ribbon and a Cipher … Scytale

I love ciphers, and the Scytale cipher is one of the oldest around. In ancient times, ciphers were often used in love and war, and where two people could pass a secret message without others knowing its contents. Mary Queen of Scots, for example, used a number of ciphers to communicate with her trusted entities:

But one of the oldest ciphers is the Scytale cipher. It was used by the Greeks within their military operations, and where they would create a cylinder of a given radius, and wrap a ribbon around it. Then, only the person with a cylinder of the right radius would be able to read the ciphered message. While it might not seem secure in our modern world, this secret message, at the time, was fairly secure (until the enemy knew the secret behind the cipher, of course).

In the following, we define a cylinder with 10 characters — defined as the height:

If we take the word “letthebattlebeginwhenthesunhasrisenintheeast” and we write a message across the cylinder, and then down, we should get [here]:

llnreeetiatbhssteeethgsn eiui bnnn awht thah tese

If we wrap, we get every 10th character:

LetthebattLebeginwheNthesunhasRisenintheEast

and so on. In this way, we could produce a cylinder with 10 segments, and then take our…