The Enigma machine is a cipher device developed and used in the early- to midth century to protect commercial , diplomatic, and military communication. The Enigma machine was considered so secure that it was used to encipher the most top-secret messages.
The Enigma has an electromechanical rotor mechanism that scrambles the 26 letters of the alphabet. In typical use, one person enters text on the Enigma's keyboard and another person writes down which of the 26 lights above the keyboard illuminated at each key press. If plaintext is entered, the illuminated letters are the ciphertext. Entering ciphertext transforms it back into readable plaintext. The rotor mechanism changes the electrical connections between the keys and the lights with each keypress.
The security of the system depends on machine settings that were generally changed daily, based on secret key lists distributed in advance, and on other settings that were changed for each message.
The receiving station would have to know and use the exact settings employed by the transmitting station to decrypt a message. Although Nazi Germany introduced a series of improvements to the Enigma over the years that hampered decryption efforts, they did not prevent Poland from cracking the machine as early as December and reading messages prior to and into the war.
Poland's sharing of their achievements enabled the Allies to exploit Enigma-enciphered messages as a major source of intelligence. Several Enigma models were produced, [ 7 ] but the German military models, having a plugboard , were the most complex. Japanese and Italian models were also in use. Pre-war German military planning emphasized fast, mobile forces and tactics, later known as blitzkrieg , which depended on radio communication for command and coordination.
