This is an excerpt from an article published in the Jan/Feb 2025 issue of IQ, the exclusive magazine for Mensa members. Find out more about becoming a Mensa member here.
Bletchley Park and the art of codebreaking
Codebreaking, or cryptography, is most often associated with Bletchley Park and the World War Two codebreakers – but its origins lie in techniques that date back almost as far as writing itself.
When most people think of codebreaking or cryptography, Bletchley Park and the Enigma code are usually the first things to come to mind. In reality, of course, people have been using codes and ciphers to write and send secret messages since ancient times.
Ancient Egyptian hieroglyphs, particularly those from around 1900 BC found in the tomb of Khnumhotep II, are considered the earliest examples of cryptography. Clay tablets discovered in Mesopotamia are designed to protect information, such as trade secrets – one tablet from around 1500 BC contained enciphered writing thought to be a secret recipe for ceramic glazes. The Ancient Romans also made use of cryptography, most famously the Caesar cipher, which Julius Caesar used in his private correspondence.
Cracking the code
For as long as there have been codes, people have been trying to crack them. Modern cryptology, the formal study and art of writing and solving codes, is thought to have originated among the Arabs in medieval times. Al-Khalil, the Arab philologist and grammarian who penned the first Arabic dictionary, was the first to systematically document codebreaking methods with his Book of Cryptographic Messages in the 8th century.
Around AD800, the Arab mathematician Al-Kindi made what has been described as the most significant advancement in cryptology until the Second World War: the invention of the frequency analysis technique, or codebreaking through counting the frequency of letters.
Cryptography and codebreaking have been involved in many major events, including the Babington plot to assassinate Queen Elizabeth I (which led to the execution of Mary, Queen of Scots).
The mid-1800s marked a turning point in the history of codebreaking. The rise of telecommunications, particularly the telegraph, highlighted the need for secure communication. In the early 20th century, many new cryptographic technologies emerged, and mechanical devices such as cipher machines were used extensively towards the end of the First World War. Cryptography’s key role in the war was underscored when British codebreakers intercepted and deciphered the Zimmermann Telegram, which played a crucial role in bringing the US into the war.
The Second World War is often viewed as the golden age of codebreaking, when advances were made in the use of mechanical and electromechanical codebreaking devices. In 1938-39, the UK’s Government Code & Cypher School (GC&CS), now known as GCHQ, began to set up shop at Bletchley Park in preparation for war, working rapidly to recruit codebreakers. Over 10,000 people worked at Bletchley at its peak, 75% of whom were women. The trailblazing team deciphered intelligence that saved thousands of lives and laid the foundations for the birth of modern computer science.
Codebreaking today
In the digital age, cryptography has become increasingly complex in both theory and practice. Modern cryptography is based heavily on mathematical theory and computer science. Processes of cryptography now enable many aspects of our day-to-day lives that we often take for granted – from protecting sensitive data when we make online purchases to allowing us to communicate securely over the internet.
Though the techniques and technology involved in cryptography have evolved greatly over the past century, the strengths and aptitudes that make a good codebreaker remain similar to those that stood out in the Bletchley Park codebreakers. The ability to think logically and laterally, to work backwards, find connections and spot patterns are crucial. So too are patience, resilience and imagination.
If you’d like to try your hand, there are resources out there to get you started. The Royal Institution offers a free online masterclass in codebreaking and ciphers, including detailed explainers and exercises to help you apply your knowledge. Websites such as MysteryTwister and Cryptohack, designed by cryptography enthusiasts, offer helpful explainers and challenges to test your codebreaking skills.
Explore encryption techniques used for guarding top-secret information, encode your own messages and discover how cryptography can help you unlock secrets, with the Royal Instituition’s free online masterclass.
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