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WWII's Colossus computer cracks codes once again

Rebuilt vacuum-tube computer runs at Bletchley Park, tackles new messages enciphered with Nazi hardware

November 15, 2007 12:00 PM ET

Computerworld - A reconstructed World War II-era British computer is trying to crack messages enciphered on Nazi hardware in an event sponsored by the National Museum of Computing, located at Bletchley Park, the wartime organization famous for breaking the German Enigma codes.

Dubbed the Colossus, the vacuum tube-based computer was built using all that remained -- photographs and fragments of some circuit board schematics -- after the original 10 machines were disassembled when the war ended. In another attempt at keeping the code-breaking secret, the Colossus original drawings were deliberately burned in 1960, more than a decade before the work of Bletchley Park was revealed.

Regarded as one of the earliest electronic digital computers -- if not the first -- Colossus was used to break messages enciphered by the Germans' Lorenz machines. Lorenz, a teletype-connected system that relied on 12 ciphering wheels, was used to encipher high-level traffic between German high command and other headquarters. Unlike the more familiar portable Enigma, Lorenz wasn't used in the field.

In what the museum has called the Cipher Challenge, the rebuilt Colossus will attempt to turn back time and decipher radio messages sent from Germany today and Friday. The messages have been encrypted using one of the few remaining Lorenz machines, and have been classified as easy, hard or hardest to decipher by virtue of the clues -- or lack of them -- in the form of some starting positions of the Lorenz wheels.

Although the messages will be transmitted from Paderborn, Germany, using modern shortwave equipment, one of the two teams in the U.K. will try to receive the messages on World War II hardware that spits out paper tape, which was used by Bletchley Park to input data into the real Colossus computers.

Amateur radio operators can intercept the transmissions, and using a virtual Colossus program on the PC -- or its Web-based cousin -- try to uncover the starting position for the Lorenz's dozen wheels. Another program, a virtual Tunny -- the latter was the nickname for the Lorenz emulator that the British code breakers created during WWII -- is needed to actually decipher the message text. Users can then submit their results to the Challenge by e-mail.

As of 2 p.m. Eastern time in the U.S., no results had been posted to the Challenge Web site. A malfunction on the German end -- the aged Lorenz's main transformer went out -- stalled work yesterday.

The Challenge is also being used to spark donations to the museum. Contributions are being taken online. More information on the Cipher Challenge can be found on the museum's Web site.

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