The Enigma machine, recently in the news after divers found one at the bottom of the Baltic Sea, is an encryption device that was developed and used in the early- to mid-20th century to protect commercial, diplomatic and military communication. It was employed extensively by Nazi Germany during World War II, in all branches of the German military.
They are rare machines and when they come to auction, they sell for thousands of dollars, as did the ones featured here that sold in 2020.
Designed shortly after World War I by German engineer Arthur Scherbius for commercial usage, the cipher engine was adopted by many national governments and militaries.
The portable device is best-known for its use by the Axis powers to encode military commands, for safe transmission by radio, as part of their rapid “blitzkrieg” strategy.
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 26 lights above the keyboard lights up at each key press. If plain text is entered, the lit-up letters are the encoded 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 a set of machine settings, and German cryptographers upgraded the security of the machines at the outbreak of the war by changing the cipher system daily, based on secret key lists distributed in advance, and on other settings that were changed for each message. The receiving station has to know and use the exact settings employed by the transmitting station to successfully decrypt a message.
German military models — made more complex through the addition of a plugboard, for added scrambling — and their code books were highly sought by the allies.
Code books contained the daily instructions for how operators should pick and set the machine’s code wheels and plugs which encoded the messages.
At their peak, the Allied forces decoded some 3,000 German messages a day — notably helping the admiralty track down U-boats during the Battle of the Atlantic.
The Mathematician Who Cracked the Code
Polish mathematicians worked out how to read Enigma messages prior to 1939, and shared this information with a team of British researchers, including famed British mathematician Alan Turing, who eventually broke the Enigma code in 1941.
Turing's work is credited with shortening World War II by several years, but until the release of the Oscar-winning film, The Imitation Game, in 2014, not many people knew who he was.
Acknowledged as one of the most innovative and powerful thinkers of the 20th century — and sometimes called the progenitor of modern computing — Turing was born in London in 1912. He studied at Cambridge and Princeton universities and was already working for the British Government’s Code and Cypher School before WWII broke out. In 1939, he took a full-time role at Bletchley Park, where his main focus was cracking the Enigma code.
Turing — along with fellow code-breaker Gordon Welchman — invented a machine known as the Bombe. This device helped to significantly reduce the work of the code-breakers, and from mid-1940, German Air Force signals were being read at Bletchley and the intelligence gained from them was helping the war effort. Turing also worked to decrypt the more complex German naval communications that had defeated many others at Bletchley. German U-boats were inflicting heavy losses on Allied shipping and the need to understand their signals was crucial.
With the help of captured Enigma material, and Turing’s work in developing a technique he called “Banburismus,” the naval Enigma messages were able to be read from 1941. In July 1942, Turing developed a complex code-breaking technique he named “Turingery.” This method fed into work by others at Bletchley in understanding the “Lorenz” cipher machine, which enciphered German strategic messages of high importance. The ability of Bletchley to read these contributed greatly to the Allied war effort.
Turing traveled to the United States in December 1942 to advise US military intelligence in the use of Bombe machines and to share his knowledge of Enigma. While there, he also saw the latest American progress on a top-secret speech-enciphering system, and when he returned to Bletchley, he eventually developed a speech-scrambling device he named “Delilah.”
Turing had also invented a hypothetical computing device in 1936 that came to be known as the “universal Turing machine.” After WWII ended, he continued his research in this area, building on his earlier work and incorporating all he’d learned during the war. While working for the National Physical Laboratory, Turing published a design for the ACE (Automatic Computing Engine), which was arguably the forerunner to the modern computer.
In 1954, Turing died as a criminal, after having been convicted under Victorian laws two years earlier as a homosexual and forced to endure chemical castration. He was found dead from cyanide poisoning, which was ruled as a suicide. In 2013, this conviction was overturned.
The work at Bletchley Park, and Turing’s role there in cracking the Enigma code, was kept secret until the 1970s, and the full story was not known until the 1990s. It has been estimated that the efforts of Turing and his fellow code-breakers not only shortened the war, but saved countless lives and helped to determine the course and outcome of the conflict.