During World War II, the Germans created a cipher device to protect military communications. It was used extensively by Nazi Germany throughout every branch of the military to send top-secret messages because this machine was considered to be so secure that nobody would be able to crack it and intercept the messages. This machine was called the Enigma machine.
The Enigma machine is one of the most famous encryption devices in history. It was used by the Germans during World War II to transmit coded messages about their plans between units. This machine offered billions of ways to encode a message, which made it difficult to break the code during the war. For a long period of time, the code was considered unbreakable, until Alan Turing and some of his fellow researchers exploited its weaknesses and created a machine called a Bombe machine that cracked the hardest parts of the Enigma code. Cracking this code meant that the Allied forces were able to stop the Germans in their tracks.
Enigma machines use a form of substitution encryption, which is a straightforward way of encoding messages. Encryption is way to code messages using different letters or numbers in order to hide information so people can’t see it unless they know how to decrypt it. The Caesar shift cipher is a common and easy to break form of encryption in which each letter of the alphabet is changed into another letter that’s several letters away in the alphabet. The Enigma machine took this form of encryption to another level by changing the entire encoding scheme every time another letter is added to the message.
An Enigma machine is made up of a keyboard, a set of lights, internal electronic circuitry, rotors, and a plugboard. When a letter is typed, a light lights up that corresponds to the letter it will become in the coded message. Then, the rotors turn, changing the cipher by moving which letter is connected to each light. The rotors could also be moved around within the machine, which would also change the encryption. The settings for the Enigma machines were changed every morning, but Enigma operators received codebooks that specified the settings for the machines that day.
The rotors on an Enigma machine were marked with the letters of the alphabet, so they could be aligned based on a numerical code. These machines used three rotors at a time, but the Germans had five different rotors to choose from that they could swap in and out of the machine or place in different positions. This gave them thousands of possible configurations.
The Enigma code had one major flaw: A letter could never be encoded as itself, which was a major clue for code-breakers working to piece together information that could decrypt the messages. Another thing that made decryption a bit easier was that the Germans tended to use similar phrases in their messages: They would usually start a message with a weather report and end it with “Heil Hitler.” Code-breakers could use the process of elimination to help crack the code. For the rest, Alan Turing and Gordon Welchman designed the Bombe machine, which helped to determine the settings of rotors and plugboards. Eventually, German messages could be decrypted within hours of their interception.