As Nazi troops invaded Europe during World War II, it was of dire importance that the Allied troops stay one step ahead. Cryptologists were instrumental in this endeavor, working tirelessly to decipher the coded messages that the German high command transmitted to its troops via radio. These efforts might have been impossible without the work of three Polish mathematicians who, in the early 1930s, managed to build their own versions of the German Enigma coding machines and crack the code these machines produced.
Working for the Polish Cipher Bureau, in Warsaw, Marian Rejewski, Jerzy Różycki, and Henryk Zygalski helped build the “bomba”—the first cryptanalytic machine to crack the Enigma machine. The machine scrambled messages in such a way that Germany believed they could be sent secretly and safely to its officers. In 1939, with the Nazi invasion of Poland imminent, the mathematicians shared their machine and methods with cryptanalysts at Bletchley Park, the main campus of the U.K. Government Code and Cypher School in Buckinghamshire, England. Thanks to this collaboration, the Allies were able to intercept and decode messages transmitted to Nazi troops—an important advantage that helped bring the war in Europe to an end in May 1945.
The mathematicians were recognized this month with an IEEE Milestone. Administered by the IEEE History Center, the Milestone program recognizes outstanding technical developments from around the world.
WORKING WITH INDICATORS
In 1917, Arthur Scherbius, a German electrical engineer, patented the Enigma: an electromechanical machine used to encrypt and decrypt messages based on the positions of its three rotors. The machine looked like a typewriter: As operators pressed a key, the corresponding letter of the encrypted message would light up. Six symbols, known as indicators, were used at the beginning of each Enigma message. The operator on the receiving end would use these indicators to position the rotors on his machine and decipher the message.
The machine was initially used for commercial purposes and was adopted by the German military in the late 1920s. The rotors—and the indicators—were rearranged frequently to throw off anyone trying to crack the code. The German army later adopted a new Enigma cipher machine with a control panel that further scrambled messages, making communications even more difficult to decode.
BUILDING A FOUNDATION
Rejewski, Różycki, and Zygalski got their start in 1928 when the Polish Cipher Bureau, then in the city of Poznań, began offering a cryptography course for math students at Poznań University. The three completed it and were recruited by the bureau, an arm of Polish military intelligence, which moved to Warsaw in 1932. By the end of that year, Rejewski had figured out the wiring of the rotors in the Enigma cipher machine. He then wrote a system of equations that analyzed the six indicators.
While Rejewski worked to figure out how the messages were constructed, Różycki and Zygalski were developing techniques to determine the Enigma machine’s settings and create an identical device that could help them decipher coded messages as they were intercepted.
Working with AVA Radio Manufacturing Co., in Warsaw, the three men produced the bomba—a system of six machines that searched through all 105,456 possible rotor settings of an Enigma machine and scanned indicators for patterns that the men noticed after several messages were intercepted. However, in December 1938, just months after the bomba was completed, the German military added two rotors to the Enigma. As a result, the Polish bureau could break very few Enigma messages using its machines alone.
Despite this setback, the mathematicians set up a meeting in Warsaw in 1939 with British and French code breakers, where they divulged their bomba system. They also began working with British cryptologists at Bletchley Park (also an IEEE Milestone) to develop more machines to analyze Enigma and its ciphers. One of these machines was the bombe, developed by mathematicians Alan Turing and Gordon Welchman, which also searched through all possible Enigma machine settings and studied the resulting patterns. While the Polish Cipher Bureau’s bomba searched for patterns in indicators, the Bletchley Park bombe analyzed patterns in messages. During 1940, nearly 178 German messages were successfully deciphered using both types of machines.
A ceremony for the Milestone honoring the three mathematicians was held on 5 August. IEEE President J. Roberto Boisson De Marca unveiled two plaques—one in Polish and one in English—which were mounted in front of the Polish Academy of Sciences’ Institute of Mathematics, in Warsaw. The plaque in English reads:
Polish Cipher Bureau mathematicians Marian Rejewski, Jerzy Różycki and Henryk Zygalski broke the German Enigma cipher machine codes. Working with engineers from the AVA Radio Manufacturing Company, they built the ‘bomba’—the first cryptanalytic machine to break Enigma codes. Their work was a foundation of British code breaking efforts, which, with later American assistance, helped end World War II.