Enigma machine
At the Victory Show, Leicester, I got to see and touch a genuine German, wartime Enigma machine. This one belongs to Mark Baldwin, who tours and lectures on Enigma and Bletchley Park codebreaking. I still don't fully understand the details of Enigma, but here's my summary. The current code (for the day, week, or whatever) is set according to the codebook. The codebook defines plugboard setting, choice of rotors, order of rotors and their initial positions. The encoding is made by several sequential stages. First, a small number of letters are substituted using the plugboard at the very front of the machine. Further substitutions then take place in each of the rotors (4 on this model). Each rotor has concealed internal wiring which converts a letter input into a different letter output. The input is fed through each rotor in turn, then back again. Finally, the resulting letter is illuminated in the rows of lights above the keyboard. Just to make it a little tougher, the rotors are automatically advanced as the message is encoded. Encoding is done letter by letter, with an operator typing the message and another person writing the encoded letters as they are illuminated.
Enigma machine
At the Victory Show, Leicester, I got to see and touch a genuine German, wartime Enigma machine. This one belongs to Mark Baldwin, who tours and lectures on Enigma and Bletchley Park codebreaking. I still don't fully understand the details of Enigma, but here's my summary. The current code (for the day, week, or whatever) is set according to the codebook. The codebook defines plugboard setting, choice of rotors, order of rotors and their initial positions. The encoding is made by several sequential stages. First, a small number of letters are substituted using the plugboard at the very front of the machine. Further substitutions then take place in each of the rotors (4 on this model). Each rotor has concealed internal wiring which converts a letter input into a different letter output. The input is fed through each rotor in turn, then back again. Finally, the resulting letter is illuminated in the rows of lights above the keyboard. Just to make it a little tougher, the rotors are automatically advanced as the message is encoded. Encoding is done letter by letter, with an operator typing the message and another person writing the encoded letters as they are illuminated.