The Caesar Cipher is one of the earliest known and simplest Ciphers. It is a substitution Cipher which means that each letter in the plaintext (original message) is swapped for (or ‘shifted’) a certain number of places along the alphabet. For example with a shift of 1, A would become B, B would become C and so on. It is also known as a shift Cipher. It isn’t difficult to break like Enigma messages, so this is a great introduction to cryptography for new Codebreakers!
Did you know? The Cipher is named after Julius Caesar who is said to have used it to communicate with his generals.
The Caesar Wheel
A Caesar wheel is a quick and simple tool to help encode and decode messages using Caesar’s cipher.
Here is a quick how-to guide to make your own!
You will need:
- A print out of the template
- A pair of scissors
- A pen or pencil
- A split-pin or paper fastener
- A friend or family member to send your secret message to (If they don’t live with you, it might be useful to send them this guide so they can make their own Caesar wheel to decode your message!)
How to build your Caesar wheel
- Write the letters A-Z (capitals) clockwise in order in the boxes around the outside of the larger circle.
- Write the letters a-z (lower case) clockwise in order in the boxes around the outside of the smaller circle.
- Cut out the two circles.
- (Carefully!) poke a hole through the dot in the centre of each wheel.
- Place the smaller circle over the larger circle so that the holes line up, and join them together using a split pin. If you don’t have a split pin you can be inventive with a piece of string or a paperclip. The two circles should be able to rotate around this centre hole with respect to each other.
To find out how to use your Caesar wheel to encrypt and decrypt messages, download the template below: