Enigma Machine

The American Computer Museum in Bozeman has acquired an Enigma machine, seen here on April 11 in Bozeman, which was used by the German army to encrypt messages during World War II, and will be exhibited as part of its collection.

GAIL SCHONTZLER, Bozeman Daily Chronicle via AP

BOZEMAN (AP) – At the height of World War II, Europe was in flames, falling to Hitler's armies and bombing raids, and the Allies were desperate to crack the German military's secret codes.

A new exhibit at Bozeman's American Computer Museum tells how teams in Poland, Britain and America deciphered the code, shortened the war and accelerated the development of the computer.

The star of the "Hacking Hitler's Code" exhibit is an actual German Army Enigma machine, housed in its wooden box, still wearing its "Enigma, Berlin" label.

George Keremedjiev, computer museum founder, said he feels lucky that David Bohnett, one of the internet's pioneers, was willing to loan the fabled Enigma machine, one of about 200 to survive. Picking up the Enigma machine in California and carrying it on the plane, Keremedjiev said, felt "magical."

It seems equally magical that human beings were able to crack the Enigma code, since it generated a diabolically vast number of combinations, 107 sextillion.

Anyone who has ever seen a Little Orphan Annie decoder ring understands the idea of having the letters of the alphabet on two rings that can be turned to create a cipher – A becomes G, B becomes H, and so on.

The magic of the Enigma machine, Keremedjiev said, was that it would actually change what the letter A corresponded to every time that A appeared in the same message.

Enigma, originally created to send bank or business messages securely, came with five wheels or rotors stamped with the alphabet. The German military created a monthly codebook that set a new key for each day – telling operators which three rotors to use and which of 26 positions to start each rotor.

The military made the code more complex by adding a plug board, like an old-fashioned telephone operators board, to reroute the signal for 10 letters, changing A to W one day, for example, and A to Q the next. As the operator typed in each letter of the plain text message, a key would light up with the encrypted letter, which a second soldier would write down.

Every day at midnight, the key changed. The Germans sent messages by Morse Code or voice, confident that even though the Allies intercepted and wrote down every signal, they could never be deciphered.

The British believed linguists had the best chance to break codes. But a Polish team of mathematicians, led by Marian Rejewski, cracked it. They created a simulator machine nicknamed Bomba, after an ice cream treat. Their efforts were helped by a spy, who stole Enigma manuals and sold them to the French, who gave them to the Poles.

Weeks before Hitler invaded Poland, knowing Warsaw was about to be destroyed, the Poles handed over their materials to the British. The exhibit shows the Bozeman Chronicle's front page from Sept. 1, 1939, headlined: "Poles Ask Aid, Nazis Bomb Cities" and a front-page editorial, "Madman of Europe: Hitler."

The British set up a secret code-breaking factory at Bletchley Park, where 10,000 people, mainly young women, toiled over Enigma encoded messages. Heading the team was an English genius, mathematician Alan Turing, who'd written a paper in 1936 outlining a universal computing machine.

The Polish code-breaking method was too slow once the Germans started changing their code key daily. So the British built deciphering machines, called Bombes, to automate and speed up the search. Turing's and Bletchley Park's success in cracking the Enigma code was depicted in the movie "Imitation Game." The code crackers were helped when German signal operators got lazy, repeating easy-to-find patterns, like Heil, Hitler, "wetter" for weather or a girlfriend's name.

But then, the Germans switched from three to four rotors in each Enigma machine, and the British Bombes couldn't keep up, Keremedjiev said.

So the Americans turned to the National Cash Register company for help. It built more than 100 faster, more powerful Bombes in Dayton, Ohio, and sent them to Washington and Bletchley. The new Bombes were so fast that the Americans had to invent an electronic counter to freeze the solution once the machine found it.

The Bombe machines shaved at least two years off the war, Keremedjiev said. The Allies knew from decrypted messages, for example, that the Germans were completely fooled about the true location of the D-Day landing.

For decades after the war, German textbooks claimed that the Enigma code was never broken. It wasn't until more recent years that the story of Bletchley Park and the code breakers came out.

"This is logic in motion," said Keremedjiev, pointing to life-size photos of Turing's machines. "He proved a machine can find a solution, if a solution can be found. He understood that machines could emulate human logic."

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