Operating a German Enigma Machine

The Enigma machine was a crude mechanical computer that the Nazis used during WWII to send and receive coded communications. This example is owned by the National Cryptologic Museum in Ft. Meade, MD.

TO ENCRYPT:
1. Write down beginning rotor settings. [There are three rotors on the machine]
2. Type name or short message slowly (Plain Text).
3. Write down each letter as the light comes on (Cipher Text).

TO DECRYPT:
1. Return rotor settings to original settings.
2. Type in Cipher Text.
3. Write down Plain Text as lights come on.

You can't see it clearly in the video, but I set the three rotors to 01 01 01 initially. I wanted to encode the word "CODE." Typing this into the machine, it output "NKIC," and each time I typed a letter, the rightmost rotor advanced a notch until the final rotor setting was 01 01 05. [My cell phone then rang. ] Resetting the rotors to 01 01 01, I then typed "NKIC" and got "CODE" as the output. Hence, the same machine can be used to encrypt and decrypt the same text messages, provided both teams know to use the same rotor settings.

One disadvantage of the Enigma was that it required a three man team to be quickly operated (one guy had to type the message out, the other had to watch the lights and write down what those were, and the third did something else). In theory, it could all have been done by one person, but this would have been really slow and tedious.

But the biggest problem with the Enigma was that the Allies had cracked its code early in the war. People really don't realize how enormously superior logistics, supplies and intelligence helped the Allies during WWII.