‘ISSP 7-8’ Lecture Review

Last week I attended an ISSP lecture by Thomas Briggs from Bletchley Park with other year 7-8 students about ‘Codes & Ciphers’. We looked at Morse Code and encryption methods to make data unreadable to unintended parties like the Caesar cipher where each letter is replaced with one a certain number up or down the alphabet.  We were told about the history of Bletchley Park near Milton Keynes, as Britain’s main decryption centre during World War Two. It was well located being remote, safe from bombing in London but well connected. People first moved there pretending to be friends in ‘Captain Ridley’s Shooting Party’ enjoying a weekend away. Really, they were from MI6, and the Government Code and Cipher School (GC&CS), a secret team of Codebreakers. At first GC&CS recruited graduates from Cambridge and Oxford Universities, particularly Classicists who were good at Latin which used code breaking type skills and mathematicians who were good problem solvers. Bletchley Park started in 1939 with 150 staff, but grew rapidly. Some were recruited from a national crossword puzzle- if you could complete it in 10 minutes you could sit crosswords in exam conditions and then may be interviewed but weren’t told what the job was! As Bletchley Park grew, sections moved into large wooden huts which for security reasons were known only by their hut numbers. Prime Minister Winston Churchill visited once but couldn’t go often to risk its security. He said Bletchley Park should have everything they wanted.

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Most enemy messages were tele-printer code enciphered with the complex Lorenz cipher machine. They were sent by telegrams communicating to army commanders in the field through telephone and telegraph cables as the Germans, Japanese and Italians thought they were unreadable. The intelligence value of breaking these was huge. In the lecture, we were shown an Enigma machine and had a hands-on demonstration. It looked like a typewriter but had a lamp board above the keys with a lamp for each letter. The operator pressed the key for the original letter of the message and the enciphered letter lit up on the lamp board. The machine had interchangeable rotors, which rotated every time a key was pressed to keep the cipher changing continuously. This was combined with a plug board on the front of the machine where pairs of letters were exchanged; these two systems gave 49 quintillion settings (!!!), which the Germans thought made Enigma unbreakable!

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The first big break into Enigma messages at Bletchley Park came in January 1940, when mathematicians including Alan Turing, broke the German Army key known as ‘The Green’. Later they cracked the ‘Red’ key used by the Luftwaffe (German air force). German, Italian and Japanese systems were broken. Breaking the ciphers gave vital intelligence to Allied military operations. It is said that the information from Bletchley shortened the war by 2-4 years, and without it the outcome would have been uncertain. Bletchley Park also started the information age as code breaking was first done by hand but they could not keep up with the number of intercepts so they made machines such as ‘Colossus’, the world’s first semi-programmable electronic computer. We were shown a photograph of Colossus and it was huge! Sadly, they were all destroyed after the war but replicas are now in Bletchley Park. I would like to visit Bletchley Park and definitely recommend going to ISSP lectures as you learn lots of interesting information about new topics.

Sebastian – Year 7