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Code Breaking
Error Checking Algorithms

The Numbers on your credit card and ISBN numbers have error checking features built in and Chris Smith has put these excellent documents together::

ISBN Numbers - Click here                 Credit Cards - Click here


Public Key Encryption

Banks, Facebook, Twitter and Google use epic numbers - based on prime factors - to keep our Internet secrets. This is RSA public-key encryption - Click here


The subject of cryptography is of obvious interest to young people, as it includes spying, intrigue, secrecy, the Enigma cipher, mobile phones and the Internet. Furthermore,  is built on mathematics, so it can be used to illustrate several aspects of the topic and its applications in the real world. And because cryptography has such a long and rich history, there is the opportunity to pick up on aspects of the history syllabus, such as the Elizabethans or the Second World War.  

I ran a Code Breaking Day where the pupils worked in groups of 3 and each group had access to a computer.

I downloaded the Code Book (lite version) [which I put on a CD to give each pupil to take home] and worked through some exercises, which I selected from those on  I mixed these in with some challenges which involved them breaking a code and finding the answer somewhere around the school using a map.  At the end of the day they had a period of time to explore one of the many techniques which we hadn't covered from the CDRom which they had to explain to the rest of the class.  Next year I shall include more challenges as these were really popular and helped the pupils to find their way around the school.  I intend to get the pupils to write their own challenges.

To download the Code Book on CDRom -Click here
For the Challenges - Click here
For the letter sent home to parents - Click here
For the Cover Page for pupil handouts - Click here
For a copy of the exercises - Click here
For the exercises with the answers - Click here
For the Challenges with the answers - Click here
For the school map I used with the challenges - Click here

WW2 Enigma Video Clip - Click here                 Alternative Clip - Click here
Make your own Enigma Machine - Click here


This series of lesson plans by Andrew Chambers takes you through a wide range of Codes and gives you a great deal of the history as well, it includes a Murder Mystery which you can personalise.

Code Resources Pack - Click here

Murder Mystery PowerPoint version - Click here

Manchester University run a Cipher Challenge each year. You can find tasks from previous years and answers if you - Click here

Additional Resources

Simon Singh has a 20 minute video clip - Click here

The Code Book (ISBN 1-85702-889-9) by Simon Singh

See Simon Singh's website for further information 

An additional Code Breaking Project can be found here

Southampton run an annual Cipher Challenge which is open to Year 10/11 pupils and begins in September.

nrich celebrated the centenary of Turing's birth Feb 2012 with lots of engaging tasks on codes and ciphers, devised with the help of James Grime of the Enigma project. We hope they stimulate interest in this intriguing field - Click here