Can Colossus still do it?

[Evan Burton]

It's like World War Two all over again. On Thursday, Germany will transmit secret, enciphered radio messages that Britain will attempt to intercept and then decipher using Colossus, a rebuilt version of the 1940s computer that cracked Nazi war-time codes.

To add to the pressure on old Colossus, a machine the size of a truck that took 14 years to rebuild, modern PC operators will be racing to see if they can unscramble the encoded transmissions first.

"It's going to be an interesting challenge, but I think we'll win," said Tony Sale, the engineer who led the project to reconstruct the computer, which along with many others was dismantled after the war to retain its secrecy.

Britain's war-time Prime Minister Winston Churchill credited those who built and operated Colossus at the Bletchley Park estate near London, including famed code-breaker Alan Turing, with helping to shorten World War Two by up to 18 months.

The Germans never fully worked out that their high-level encryption machine, called the Lorenz SZ42, had been cracked and continued to use it to encipher military commands, including crucial details on troop movements, ammunition and supplies.

Thursday's experiment is not just the culmination of a labour of love for Sale and his team, but an opportunity to show just how powerful and effective a 63-year-old computer can be and how avant-garde it was for its time.

The challenge will involve engineers at the Heinz Nixdorf Museum in Paderborn, Germany encoding three secret German texts using the Lorenz cipher and then transmitting them via radio.

In Britain, a team of experts will use World War Two era equipment to intercept the messages and transfer them to Sale to be loaded into the Colossus. The computer will then try to work out the cipher settings, allowing the messages to be read.

It's a laborious process.

Just the transmission of the messages - 6000 characters of German text in all - will take 20 minutes, while the deciphering could take anything from six hours to a day, although Sale hopes it will be at the shorter end of the range.

In its heyday, Colossus and several other computers like it were able to crack codes in a few hours, allowing Britain's war-time leaders to understand Germany's battle plans and adjust tactics accordingly.

Even though the Colossi, as they were known, were dismantled after the war, and their existence only properly discovered in the late 1970s when the Official Secrets Act provisions expired, they laid the groundwork for modern computing.

While their return to service will echo World War Two, the messages will bear no resemblance to secret war plans.

"There are sensitivities in Germany about such things, so we are just transmitting detailed descriptions of the Heinz Nixdorf Museum," Sale told Reuters. "It was the safest thing to do."

http://www.smh.com.au/news/technology/can-...4766927938.html