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How did the Enigma machine encrypt German military messages?

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Ultra The British government established a code-breaking effort, known as Ultra, at Bletchley Park in Buckinghamshire, England, during World War II.

The Enigma machine encrypted German military messages using a polyalphabetic substitution cipher generated through a combination of a plugboard and a series of rotating wheels, or rotors.12

The encryption process functioned as follows:
* Rotor System: The machine utilized a stack of rotors that provided an electrical path for a current. When a key was pressed on the keyboard, the current passed through the maze of interconnections defined by the rotors' relative positions, outputting a ciphertext letter.3
* Daily Settings: Operators configured the machine daily using codebooks that specified the initial positions of the rotors and the plugboard settings.12
* Message Keys: To increase security, the Germans added a unique message key for each transmission. This key was encrypted using the day's settings, and the message itself was then encrypted using the specific scrambler orientation dictated by that unique message key.2

This electromechanical design created a vast number of potential permutations, making the code exceptionally difficult to break without the specialized cryptanalysis efforts developed by the Allies under the Ultra project.142