The Secrets of Codes

If you'd like to send a message that only your agent can read, you'll need to use some sort of code. There are several different types of code depending on what you want to send.

Quick links: Scrambled Codes Caesar Shift Vigenere Grid

Hidden Code

This is a good sort of code to write on a postcard or even stick on a noticeboard. It can look totally innocent and although anyone can see it, they won't suspect that there's a secret message hidden in there. The only person who can read the secret message will be your agent!

There's a message hidden on this piece of paper. Can you spot it before we tell you the secret?

If you can't work it out, then the secret is that you have to read every third word starting with "my". Have you got it now? Ouch!

However, if you want something a bit more secure, try one of the codes below.


Did you manage to read the last headline?

All the letters are there, but they're mixed up.

Find out how to unmix them in Scrambled Codes

The Caesar Shift

The Caesar Shift is one of the best known cipher systems.

A cipher usually means that each letter is replaced by a different letter, and to decode a message you need to know the secret key.

A simple version of this system was used by the Roman Emperor Caesar to help him conquer the world. We'll show you how to use it and even make it better!

The Vigenere Grid

The Vigenere Grid is a very clever cipher system, similar to the Caesar Shift. It is so secure, it is still being used by real spies today.

The Vigenere system works with either a key word, a key sentence or even a whole key book. When the code is being used with a book, even computers can't break this one!

Teacher Resources

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