The Enigma machine
Codebreaking in world war two
The enigma machine was a machine developed in Germany, and used by the German army, to encrypt messages for use by all areas of the german armed forces, including intelligence services. Another enigma machine at the other end on the same settings was used to decode it.
How it worked
The Operator would type in their message, and the specifically set rotors scrambled it into random letters. Whoever was receiving the message had to have exactly the same settings on their Enigma machine to decipher the code.
How they solved it
A Polish mathematician called Marian Rejewski built an Enigma machine himself. Then, after finding out that the Germans changed the code constantly, he wired several enigma machines together, to run through possible combinations. This was used by the Poles for several years to read the German messages. When they added more rotors to the machine to make it harder to decipher, the Poles handed over replica enigma machines to the British codebreakers at Bletchley Park. Alan Turing connected several 'bombes', the codebreaking machines, to quickly look for possible settings. This allowed the codebreakers to continue deciphering German messages.