Colossus

BLETCHLEY, England--They say that it would have taken at least two more years to defeat the German military had not some of the Nazis' secret codes fallen into the hands of the Allies.

For decades, since 1918, the Germans had been using Enigma cyphers as the core of their intelligence and military communications system. The Enigma was first invented for scrambling financial communications, but while that use never took off, the military saw the promise of the system. For one thing, the Germans thought Enigma was unbreakable.

But based on techniques arrived at, and a version of Enigma built by, Polish mathematicians, the master codebreakers at Bletchley Park, a secret installation about 45 minutes outside London, eventually proved the Germans wrong. Still, it took years to beat Enigma, a machine with "complexity [that] was bewildering," according to information provided on the Bletchley Park Museum's Web site.

At the same time, the Nazi high command was sending coded messages using a device called the Lorenz. To solve that, Bletchley Park's code breakers came up with a machine called Colossus.

This is a rebuild of the famous Colossus Mark 2 machine (left) that finally allowed the code breakers to quickly and efficiently break the high command's ciphers. The original Colossus was so secret that after the war was over, it was broken apart and its components destroyed. But because there were 11 surviving pictures of the machine, Bletchley Park museum personnel have been able to build a fully working reconstruction, and visitors to the National Museum of Computing here can see the new Colossus for themselves.

CNET reporter Daniel Terdiman visited Bletchley Park as part of Road Trip 2011. And last year, as part of Road Trip 2010, he visited the U.S. National Security Agency's National Cryptologic Museum in Ft. Meade, Maryland, where many related items such as a collection of Enigmas, are on display. This gallery showcases some items from Ft. Meade that complement what's on display at Bletchley Park.

Correction (Monday, 3:50 p.m. PDT): This article has been modified to correct errors that confused work done at Bletchley Park on Colossus with that done there on the Bombe machine, as well as to credit work done on Enigma by Polish mathematicians.

• CNET Road Trip 2011

July 4, 2011 4:00 AM PDT

Photo by: Daniel Terdiman/CNET

| Caption by: Daniel Terdiman