During the Second World War German officials
and military forces used an innovative electro-mechanical device
known as the Enigma machine to protect their top-secret radio traffic.
Though the historical documents (held at the Public Record Office)
remained classified until the 1970s, the story of the breaking of
the Enigma cipher is now one of the most celebrated of the war.
The Enigma machine was invented by Arthur Scherbius
and produced commercially for the banking industry in 1918. The
German Navy saw its potential for military use and adapted the system
of rotors, keyboard and electrical wires. Resembling a typewriter,
the machine was portable and ideally suited to use in combat, and
was quickly adopted by all branches of the German armed forces.
made great strides in understanding the design of the military Enigmas and even
constructed several versions of the machine. In 1939 the Germans
began strengthening their system by changing the cipher every day.
The German Navy equipped their Enigma machines with extra rotors
and separate codebooks to create ever more complex encryptions.
Enigma protected German radio communications, allowing U-boats to
inflict massive losses on commercial and military shipping around
Britain and the Luftwaffe to strike suddenly with devastating effect.
Throughout the war a team of British and Polish
mathematicians and cryptanalysts were based at Bletchley Park (codenamed
Station X), working round the clock to unscramble the streams of
intercepted information. Enigma created a new form of encryption
based on mathematics, not language. An understanding of letter frequency
and linguistic patterns would not crack enigma encoded messages. The capture
of an Enigma machine and codebooks from a German U-boat on 9 May
1941 and other more conventional acts of espionage led to significant breakthroughs.