OF INTEREST… BLETCHLEY PARK
From Secret Intelligence Centre to World Class Heritage Site
Dr Joel Greenberg – Bletchley Park Trust
Bletchley Park and its tremendous story have featured regularly in film and television over the past few years. The most recent interest triggered through the amazing story in the film starring Benedict Cumberbatch – The Imitation Game. Dr Joel Greenberg of the Bletchley Park Trust shares the history.
Introduction
During WW2, Bletchley Park (BP), a 55 acre country estate in the Buckinghamshire countryside was the home of an organisation called the Government Code and Cipher School (GC&CS). Set up in 1919 by merging small War Office and Admiralty based code-breaking teams, GC&CS grew to a large intelligence centre, employing around 10,500 people by the end of WW2. GC&CS staff developed methods to break the military codes and ciphers that secured the communications of Germany, Japan and other Axis nations. This resulted in vital intelligence which subsequently informed Allied military operations. BP industrialised its codebreaking processes by developing machines such as the Turing/Welchman Bombe and the world’s first electronic computer, Colossus. Hollerith punch card equipment was adapted to enable an early form of data search.
At the end of the War the unique expertise that had been developed at BP was taken
forward by a number of the wartime GC&CS staff into a new organisation known to this day as Government Communications Headquarters (GCHQ).
The Intelligence War
At the beginning of WW1, Britain and Germany, along with other countries started to use wireless radio for their diplomatic, commercial and military communications. By the end of WW1, cipher machines started to appear to protect these communications from unintended recipients. A cipher replaces each character of a message with another letter, as randomly as possible. The German Arthur Scherbius acquired a patent for a commercial cipher device in the 1920s and gave it the brand name, ‘Enigma’. Eventually, various versions of Scherbius’s machine were adopted by all branches of the German military apparatus as well as the German Police and Railways. Standard procedures for the Enigma operators were introduced and gradually strengthened throughout the war.
In the case of the German Army and Air Force, the machine’s settings were changed every 24 hours. The machine was used primarily for operational messages, usually no longer than 250 characters. By 1943, GC&CS was working on over 100 German Army and Air Force communication networks, each with its own daily setting of which there were 158.9 million, million, million possibilities. The Enigma machine worked on the principal of symmetry. If two machines were set up in the same way, if on one you typed ‘A’ and it turned it into ‘B’, on the other machine if you typed ‘B’, it would turn it into ‘A’. The sending operator would encrypt his message using the daily setting and then send it to other operators in Morse code over wireless radio. The receiving operators would have their machines set up exactly the same as the sending operator. They would simply type in the encrypted characters to recover the original text of the message. BP initially used methods developed by Polish codebreakers to read Enigma encrypted messages. Eventually, a new hand method was developed which was supported by machines called ‘Bombes’, developed by Cambridge mathematicians Alan Turing and Gordon Welchman.
48 Envoy Spring 2015
www.raf-ff.org.uk
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