Top Secret: Ciphers from Ancient Greece to the Second World War

From 11 February – 5 June 2022, the National Science and Media Museum is home to Top Secret: From Cipher to Cyber Security. The exhibition has been created alongside expert advisers GCHQ, with support from principal funder The Department for Digital, Culture, Media & Sport. It explores the fascinating world of codebreaking, ciphers and secret communications.

A cipher is a code used to protect information that is being stored or communicated so that only selected people have access to it. Encryption is another term that can be used to describe the creation of secret messages, with decryption being the process used to convert the cipher text back to normal (or ‘plain text’).

Today, terms like encryption and decryption are most often associated with computers and digital code; however, the oldest cipher can be dated back to Ancient Greece, as early as 400BC.

It’s likely that ever since writing was invented, humans have invented found ways to disguise the written word, especially if it contained sensitive information. But the first recorded example of a cipher used for communication was by the Spartans in ancient Greece, using a device known as the scytale. (‘Scytale’ means ‘baton’ in Greek.)

The scytale was used for secret communications between military commanders. As shown above, it consisted of a tapered baton with a strip of parchment or leather wrapped around it in a spiral; this is what the message was written on. When unwrapped, the letters were scrambled, thus creating a cipher. To decrypt the code, the strip would have to be wrapped around another stick with the same proportions as the original.

Want to have a go at creating your own scytale? Visit the National Science and Media Museum this half term (19–27 February 2022) and get involved in Secrets Unravelled, one of our Explainer team’s free family activities. Using a block of bamboo and some ribbon, you too will be able to write your own cipher text and communicate secret messages to the people you trust.

As well as making your own scytale, you’ll also have the chance to explore other devices used for secret communications, such as the cipher wheel. You can see lots of examples of cipher machines in Galleries 1 and 2 as part of Top Secret, and during half term you can also join our Cipher Wheels activity—try your hand at making a cipher wheel out of paper, then use it to encrypt and decrypt your own secret messages.

One of the most famous examples of codebreaking comes from the Second World War. During the war, the Nazis used a special cipher machine called the Enigma (shown above). This machine would mechanically encrypt their messages; for example, if you were to type the letter ‘A’ on the keyboard, the Enigma would change it to an ‘S’. These letter codes would change daily, making it extremely difficult for the allied forces to understand Nazi plans…

… Until March 1940, when Alan Turing created the Bombe (above), a codebreaking machine at Bletchley Park, the then headquarters of GCHQ. The Bombe searched through different possible positions of Enigma’s internal cogs, searching for a pattern of keyboard-to-lamp-board connections that would translate the coded letters into plain-text German.

Historians believe that Alan Turing’s codebreaking skills may have shortened the Second World War by two years, saving millions of lives. In honour of his achievements, his face was added to the £50 note which went into circulation in 2021. You can see this new £50 note, as well an Enigma machine, at the Top Secret exhibition.

Top Secret: From Ciphers to Cyber Security is at the National Science and Media Museum from 11 February to 5 June 2022. Free family activities will be taking place throughout February half term, 19–27 February 2022.