About the challenge

The National Cipher Challenge has been run by the University of Southampton Mathematics Department since 2002 and has attracted a wide following. We count ex-Cabinet Ministers (an maybe some current ones – would love to hear from them!), media scientists, journalists, authors and actors among our fans. We even had the pleasure of introducing the Cipher Challenge team from Saint Anne’s School in Southampton to the Duke of Edinburgh who, remembering his work in the second world war immediately fell in love with the competition and gave Harry a reading list for the summer.

The real fans though are the competitors who take part every year until they are too old, by which time it is too late and they are hooked. Many of them go on to careers in cyber security and others follow other paths using the mathematics and computing skills they learned tackling our fiendish challenges.

Julian went on to study Discrete Mathematics and made it to the Grand Final of the UK National Cyber Security Championship in 2013, following in the footsteps of the 2008 National Cipher Challenge winner, Jonathan Millican, who was crowned winner of the UK National Cyber Security Championship the previous year. Naomi Andrew, who operates under a code name as one of the Elves on the site, took part from Year 8 until she was sadly too old to compete, but managed to stay involved as a student at Southampton. She stayed on for a PhD and is now a working as a research mathematician at Oxford. We like to think the Cipher Challenge had an important part to play in that journey.

If I were to name one thing which has undoubtedly influenced my academic drive, interests and overall career to date, it would be the National Cipher Challenge. Since being introduced to cryptography and the challenge in Year 8, it has been my one passion and driving force in pursuing further education in maths.

Julian Bahrdwaj

Competitors take part by breaking codes and ciphers that are published week by week on the challenge pages, throughout the competition and submitting their answers on that page. Each challenge comes as two parts, part A and part B, and together they add up to a short story. The ciphers get harder as the competition progresses and competitors can download certificates recording their progress. You can read more about it here on this page and elsewhere on the site.

The lesson PowerPoints are great to use with any year group – easy to understand with passages written in code for them to practise using the decryption methods, with little input needed from the teacher. Would recommend – especially if you are starting a Codebreaking club before the competition begins like me.

Sam Barlow, Queen Anne’s School, Caversham

Even if you can’t or don’t want to take part in the competition there is a lot here for you to enjoy.

Alongside the materials we have produced you will find everything you need to be a successful code-breaker.

We have a library full of suggestions of great books, fact and fiction, links to a whole range of videos on topics related to maths, computing and codebreaking, even a guest lecture by one of our alumni describing how he learned python to break the challenge.

We have some basic cipher tools you can use to get started including a Caesar wheel, an affine shift encryption machine and a frequency analyser to help you break down and find patterns in a ciphertext. In our cryptanalyst handbook you can find instructions to build your own cipher machines, including the simple cipher wheel and tis more sophisticated cousin the affine shift cipher wheel. Or you can go a step further and explore the fascinating Enigma machine and its cardboard twin, the Pringle Can Enigma Machine.

It was said by Niels Ferguson, one of the leading cryptographers of his generation, that cryptography was “just about the most fun you can have with mathematics”. As professional mathematicians we can think of a few others too, but we largely agree with that and hope that the Cipher Challenge will convince you too.