Off-the-shelf Masterclass: Codebreaking & Ciphers

Off-the-shelf Primary Mathematics Masterclass about creating and cracking secret codes.

Explore some encryption techniques used throughout history for guarding top-secret information. Encode messages using a variety of different ciphers, and discover how cryptography can help you unlock secrets.

  • Credit: (Enigma Machine) University of Manchester School of Mathematics via Flickr

About this Masterclass

Cryptography is a fascinating topic that makes today’s world possible. The techniques we use to keep messages secret have improved significantly over millennia, moving from very simple ideas to increasingly complex and computationally difficult as we get better at cracking codes and ciphers. Working out how to crack encryptions and read secret messages is a skill which has always been in high demand and is a very interesting career for many mathematicians.

This workshop encourages students to think strategically and logically to solve problems as they go through the basics of encryption and decryption. Focusing on transposition and substitution ciphers, where each letter is replaced or moved to create an encrypted message, we will create our own ciphers and work together to crack each other’s.

Length: 2 hours (see the session leader notes for ideas on how to shorten the Masterclass).

Resources needed

  • Copies of worksheets, as detailed in Session Leader Notes 
  • Optional: copies of student take-home activity with guidance for extension activities
  • Fixed Caesar wheel templates: 0-25, 3 and Blank. Printed from templates, as detailed in Session Leader Notes 
  • Optional: split-pins, paperclips and rotating wheel template to replace fixed wheels
  • Computer and data projector


All supporting notes, worksheets and solutions can be downloaded from this page along with the Powerpoint presentation.

The Session Leader Notes offer full notes on the activities and a detailed list of resources, including quantities needed. 

The Session Helper Notes can be distributed amongst helpers giving them an overview of the subject and activities planned.

Ask the Ri

You can collect any student questions and email them to the Ri Masterclass team at - we will endeavour to answer them before the next Masterclass in your series.

Masterclass series support

For more information on running a Masterclass series and the support, templates and other resources available to you, please get in touch via