Julius Caesar was known for many things. He was a historian, a military strategist and politician who played a key role in transforming the Roman Republic into the Roman Empire. Caesar was also the first general who implemented a use of codes to hide messages to his commanders from prying eyes. Caesar's codes are elementary, but for the ancients they worked wonders.

In cryptology there are two main terms you have to remember. There is the plaintext - the written out, easily understood message, and the ciphertext - the encoded message that is indistinguishable at first sight.

The first and simplest method of encryption is called the Caesarian Square. This method uses messages written in a number of letters that is a perfect square to hide the message, meaning that your plaintext message must contain either 4, 9, 16, 25, 36, 49, 64, 81, 100 etc. to be properly encrypted. One thing to remember is that the longer the message the harder it is for prying eyes to decipher.

Caesar would use the square pattern to reformat the message so that instead of reading horizontally it would read vertically. After rewriting the message vertically in the square pattern he would recopy the message line by line so that it once again read horizontally, except the message looked like a mass of jumbled letters.

For our example the plaintext will be:
Begin the first attack at dawn.

We start encoding our message by removing all the punctuation and spaces making the plaintext:
beginthefirstattackatdawn

After removing all the punctuation we rewrite the message in a square pattern with the message reading vertically instead of horizontally:

b t r t t
e h s a d
g e t c a
i f a k w
n i t a n

The final step is to rewrite the message so that it reads horizontally creating the ciphertext without any breaks:

btrttehsadgetcaifakwnitan

And that's how to encode a message using the Caesarian Square. To decode we just do everything backwards.

Lets take use this ciphertext as the example:

oaenskhhsaebiennisclboor
ialeitptueattlwtdswhaaytt

First, we count the letters in the ciphertext. There are 49. By taking the square root we discover that the message was encripted using a 7x7 square.

Using this information we rewrite the message in the square starting a new line every seven letters:

o a e n s k h
h s a e b i e
n n i s e l b
o o r i a l e
i t p t u e a
t t l w t d s
w h a a y t t

Once we have the message in the square form, we read it vertically revealing the plaintext.

ohnoitwasnottheplanesitwas
beautykilledthebeast, or

"Oh, no, it was not the planes. It was Beauty killed the Beast."
-- King Kong (1933)

The good thing about the Caesarian square is that it is very simple to use and takes little time to encrypt and decode.

Two problems are that if someone knows that you are using a Caesarian square encryption, they can easily decode your message. The other problem is you can only encrypt messages with a number of letters that are a perfect squre. There are methods to get around this though.

If your message only has 22 letters, you can attach three random letters to the end to fit the square pattern. You could also add letters somewhere in the middle, but this could make decoding the message harder. Whatever method you choose, make sure your recieving party knows how to decode the message.

Move on to Caeser's next method: The Caesarian Shift -->