Hannah Wins the GCHQ Prize in This Year's National Cipher Challenge

Many congratulations to Hannah Blacker in Year 11 who has won the GCHQ prize in this year’s National Cipher Challenge.  

Run by the Mathematics department at the University of Southampton, the National Cipher Challenge is an online coding competition for secondary schools and colleges, with this year’s competition attracting over 7,000 registrations.

Hannah worked solo to crack the tricky set of challenges and the prize committee was very impressed by her submission.  Just before half-term Hannah was invited to attend the prizegiving event at Bletchley Park to receive her award.  

We asked Hannah to report back on this year’s competition, and what it’s like to take part.

The National Cipher Challenge is a cryptography competition run by the Mathematics department at the University of Southampton, with sponsors including GCHQ, IBM, Trinity College Cambridge, and Netcraft. The challenges range from simple Caesar Ciphers to complex polyalphabetic substitution and transposition ciphers. It is formed of 10 week-long challenges where you can gain points for the correct solution and the time you took to solve it. 

This year’s competition contained a lot of transposition ciphers, and the final challenge was a Cadenus cipher (a complex transposition variant). I hadn’t explored many transposition ciphers before, so I learnt a lot throughout the challenge. For the final challenge, I needed to use programming skills, as well as maths, creative thinking, and problem solving. The final challenge was three weeks instead of one, and I solved it in 7 days of hard work. 

As one of the top 20 teams/individuals, I had to submit an account of how I had solved the final challenge and any code written to solve it, which they used to decide prize winners.

We were then invited to a day at Bletchley Park, the wartime home of the codebreakers, which included a tour around the park and lectures. It finished with a prizegiving, where I was awarded the GCHQ prize. It was an amazing experience! I highly recommend it to anyone interested in ciphers, computing, maths, or problem solving!