How it began
Marian Rejewski, a civilian mathematician at the Polish General Staff's Cipher Bureau in Warsaw, designed the bomba kryptologiczna around October 1938. He had already worked out the internal wiring of the military Enigma from the way operators encrypted each message key twice. Engineers of the AVA Radio Manufacturing Company built the machines. Six were made in Warsaw before September 1939, and by mid-November 1938 they were ready for use.
Before it existed
Even with Enigma's wiring known, each possible daily key still had to be checked to read a message, and there were many thousands. The Poles' earlier manual technique, the grill method, depended on pairs of letters left unchanged by the plugboard. As the Germans added plug connections and changed procedures, the hand methods became an increasingly daunting task.
How it works
Each bomba was in essence an electrically powered aggregate of six Enigmas, with an electric motor turning its sets of rotors. It exploited the German habit of typing the three-letter message key twice at the start of a message. Unlike the grill, it needed only single letters left unchanged by the plugboard, so it still worked when five to eight plug connections were in use. One bomba took the place of about one hundred workers.
How it spread
On July 25, 1939, the Poles disclosed their Enigma-breaking methods and equipment to their French and British allies. Rejewski stated that the deteriorating political situation prompted the decision, not technical difficulty. The later British machine at Bletchley Park was called the bombe. In recognition, IEEE has designated the Polish Cipher Bureau's breaking of Enigma from 1932 to 1939 an engineering Milestone.
What changed first
With the machines running, reconstructing a daily key took about two hours. On December 15, 1938, the Germans introduced two new rotors, which raised the number of possible rotor orders from 6 to 60 and multiplied the work tenfold. Rejewski later wrote that the change was one of quantity, requiring far more machines, sheets and staff.
