Form 5 stepped into the roles of real-life codebreakers as they took on a high-energy cryptography challenge designed to test teamwork, problem solving and computing skills, with the ultimate prize of cracking open a toy safe. The activity forms part of their Thursday afternoon choice sessions where pupils select from a range of enrichment opportunities.
They have been studying a variety of encryption techniques, including Caesar and Atbash ciphers as well as the more complex Vigenère cipher. Their final challenge put all this learning to the test as they worked together to decode a set of secret messages without being told which encryption method had been used.
I wanted the pupils to experience the kind of uncertainty real codebreakers face. In real-world cryptography no one taps you on the shoulder to tell you which cipher was used. You need to recognise patterns, make inferences and collaborate. They absolutely rose to the challenge.
To solve the mystery, pupils were given access to a dedicated website and a set of 20 unique worksheets created through a mail merge system. Hidden across the materials were four key phrases, each combining a number with two descriptors such as “5 cooking teachers” or “3 maths preps.” The website itself also contained its own secrets. In each of four sections selected letters were italicised to discreetly spell out hidden clues including red dog, big snacks, sports teachers and women jump. Each of these phrases appeared on exactly one worksheet.
Every worksheet contained four encrypted phrases, each using a different cipher: the Caesar cipher, the Atbash cipher, Vigenère and finally an anagram. The children first had to identify which cipher was being used, then work together to decode all four sections. By matching their decoded messages with the hidden phrases on the website, they were able to piece together the four digits of the safe’s combination.
It was amazing watching them share ideas and spot patterns together. One group would shout out a discovery and suddenly another group realised how it helped their clue. The atmosphere was fantastic and they were completely absorbed.
The cryptography session explored not only historical codes but also the mathematics behind modern encryption and the impact of emerging technologies.
Computing plays a vital role in keeping our data secure. We look at how early methods evolved, how computers disrupted the field and even how future technologies such as quantum computing could force us to rethink digital security entirely. The pupils love discussing what the future might hold.
The challenge concluded with the triumphant unlocking of the safe to the delight of the class. But the real reward was the sense of achievement and the curiosity it sparked. The activity continues to be a highlight of Form 5's choice programme and the enthusiasm shown suggests the pupils will be more than ready for their next cryptographic mission.