Perse code breakers find formula for national success
A team of Perse students have cracked the code to claim silver medals in a national cryptography competition.
Team Puzzling Pelicans, featuring Daniel, Luca, Oliver (both Lower Sixth) and Ryan (Year 11), came joint second in the National Cipher Challenge, a competition organised by Southampton University aimed at getting youngsters interested in the world of codebreaking.
In addition, Team 101 Pelicans, formed of Perse Year 8 pupils Florence, Jeffrey, Alicia, Joshua, Haransh, Cato, Tim and Benjamin, did extremely well to finish 12th overall.
Daniel, Luca, Oliver and Ryan also won a cash prize for their outstanding efforts in the National Cipher Challenge, which saw teams take on increasingly difficult weekly online challenges over a three-month period with points awarded for how quickly the problems are solved.
Team leader Daniel, who has been involved in the school’s Cipher Club since Year 8, said the group relished the process of systematically unveiling the passages of writing, which were based on a series of imagined letters between computing pioneers, including Charles Babbage and Ada Lovelace.
He said: “The first thing to work out is which cipher is being used because they work in different ways, but from certain clues, you can work out what it is and start using trial and error by hand.
Luca added: “We do frequency analysis by looking at the statistics of a piece of encrypted text and comparing that to what it should be. For example, seeing how frequently different letters come up. From there, there are quite a lot of ciphers it could be, but from the statistics you can infer something and you can bring in machine learning to help.
Oliver explained the machine learning technique of ‘hill climbing’ was extremely useful in the process of codebreaking. He said: “This is where you start by trying random attempts to learn the cipher, but then little things change. You pick up on them and slowly the decryption improves.”
Throughout the competition, they began each challenge by individually trying to break down the encoded puzzle from different angles. Once a team member felt they were on to something, they worked together to find algorithms that could crack the code.
The group broke one code in a staggering time of just 0.423 seconds, but the final challenge, deciphering a passage that used just three different symbols, proved a tougher nut to crack, albeit completed in a little over two hours.
Daniel said: “The cipher wasn’t a classical one, but one the organisers had created, so the longest part of the process was trying to figure out how the cipher worked. We went through almost 20 ideas.”
Luca added: “I felt quite nervous for the 10 seconds we had to wait to see if the algorithm worked at the end, so it was thrilling to see it work, especially when you’ve been trying to figure it out for two hours.”