Cross Curricular maths: Codes and Codebreakers

About a year ago I gave a talk to a group of maths students at a careers event at Oxford University. I endeavoured to persuade them to ignore all offers of ridiculously highly paid jobs in the city and become secondary maths teachers instead. Not an easy task. So I was pleasantly suprised when quite a few students came up to speak to me at the end of all the talks.

I was particularly surprised that anyone bothered to speak to me because the speaker who came directly before me was from GCHQ. He worked as a codebreaker and was incredibly cool.

Mathematicians are in high demand at GCHQ he said. The work is really interesting and it pays well. Where else could you say that your mathematical skills were being put to use to help protect the nation? You'll be serving Queen and Country from a very comfortable office in Cheltenham.

Powerful stuff.

Even more enticing - he pointed out that codebreakers weren't allowed to take work home and were strongly discouraged from staying later than 5pm. I started to have doubts about my chosen career.....

To remind myself that teaching really is the best job in the world, I decided that I could have a go at being a codebreaker myself and I'd get my year 8 class to join in. I used some resources from Nrich, out of which I particularly like the transposition cipher because it helps cement understanding of factors and multiples http://nrich.maths.org/7940.

This year we're going one step further and one of my wonderful colleagues in the history department has got involved. We're rolling out the codebreaking project to the whole of year 8 and putting it in the context of WW2 codebreakers at Bletchly park. (This context has the major advantage of demonstrating how women can be excllent mathematicians too. Girls need mathematical role models). This is the first slide:

The history teacher gave me some sentences in English which I have coded using different techniques including the ceasar shift technique, the pigpen cipher, a transposition cipher and the vigenere square. I used Simon Singh's wonderful website to help me out. It does the ciphering for you! http://www.simonsingh.net/The_Black_Chamber/chamberguide.html  And it gives some really useful historical context to each technique.