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Code Breaking for Young Secret Agents

The world of secret codes holds a fascinating air of mystery with secret agents trying to discover the enemy’s plans before the enemy uncovers theirs. The Spartans are credited with creating the first system of military secret codes, or secret ciphers, as they are sometimes called. This is why the study of secret codes and methods of breaking these codes is called Cryptology, from the Greek kryptos meaning hidden or secret.


One example of a secret code method is called a Keyword Cipher

With this secret code keyword is placed at the beginning and this shifts the remaining letters of the alphabet, not used in the keyword, to the right. The letters that are not used in the keyword are placed in line in alphabetical order.


For example if the keyword was JAMESBOND the code would read as follows:


To code the message:  SEND HELP QUICKLY

 The code for this is:    RSIE NSGL PUDMFGY


Here is a challenge for you to try, use the JAMESBOND Keyword Cipher to break the code and find the answer to this question.


In the James Bond film The Man With The Golden Gun, how many shots does Scaramanga have with his Golden Gun?


Below is the coded answer to this question.




Organising the Code Breaking Day


There are many different types of secret codes and you can organise different types of challenges for students to take part in.


  • Student teams move around a room (classroom/hall) decoding to find the hidden message(s). For each challenge they are given a set amount of time. Each team gets a score depending on how many codes their team solves.
  • Teams are given code breaking challenges. Once the team has decoded the message correctly they are given the next.
  • A set of coded messages are given out at the beginning of the week to all students in the school.
  • Quick-fire short secret codes can be given out daily.
  • You can work out the relative frequency of letters in the written word by looking at newspaper articles and books. This is useful to spies since if you know E is the most frequent letter and you are decoding a paragraph with lots of Hs, you would guess that E has been replaced by H in the code.


Create your own Code Breaking Day by using the resources below.


Websites on Code Breaking


Codes and Ciphers Teaching Resources Website

Great resource for your code breaking day on Substitution Ciphers, Braille, Bar Codes, ISBN Numbers, Genetic Fingerprinting, Postcodes, Semaphore, Morse Code, and many others. Each comes with lesson plans, pupil information and exercises, and teacher notes. 

Secret Code Breaker

Learn all about secret codes including Caesar Ciphers, Auto Key Ciphers, and Monoalphabetic Substitution Ciphers. Online and downloadable solvers are provided for many of the common ciphers. The website also contains some interesting history stories on code breaking



Kids Spy Equipment

Fun website on how to make spy equipment – How to build a periscope, Keyhole spy tool, Spy ID card, Make Invisible Ink and  Fingerprint powder.


Codes, Ciphers & Codebreaking

Comprehensive guide to codes


The Secret World of Codes and Code Breaking

Stories to use for background history on code breaking



Books on Code Breaking


The Secret Life of Codes (Murderous Maths) by Kjartan Poskitt

Readers will learn how to encode and decode their own messages in as many ways as possible with Poskitt hilarious characters.


The Code Book: The Secret History of Codes and Code-breaking by Simon Singh

Contains many fascinating accounts of code-breaking in action, from its use in unmasking the Man in the Iron Mask and the defeat of the Nazis to the breaking of a modern cipher system by a world-wide army of amateurs in 1994.


Secret Code Breaking for the young secret agent 

Watch out for Dr Maths (aka Steve Humble) book on code breaking coming out in January 2012