This Machine Kills Fascists (Just Not Quite As Fast As Your Laptop Does)

When I heard people talk about “The Greatest Generation”, I tend to assume they’re talking about human beings, like the soldiers that landed on Omaha Beach or fought at Anzio.

However it seems that nostalgia for the World War II era extends past mere mortals and encompasses machines as well.

For example, a group of British computer enthusiasts spent over a decade rebuilding a massive 1944-vintage Colossus Mk2 computer. The Colossus, one of the first “supercomputers”, was originally used by the British government to decode encrypted German teletype communiqués during World War II. In case you think the name “Colossus” is a result of wartime morale-boosting hyperbole, it’s actually more of an example of British understatement, since each Colossus machine used 1,500 vacuum tubes and took up over 80 square feet of floor space.

The Colossus Mk2 was designed to break the codes created by German encryption machines known as the Lorenz SZ40 and SZ42. The comparatively svelte and low-tech Lorenz machines used five spinning metal wheels to mix seemingly random digits in with the standard code to transmit messages via teletype, making it impossible for average teletype machines to decode the transmission. British codebreakers figured out how to reverse engineer the Lorenz encryption in 1941 after some hapless German teletype operators re-transmitted the same encrypted message twice in a row with slight variations. Comparing the two transmissions along with the other unencrypted German messages allowed British cryptographers to figure out the pattern the Lorenz machines used to add extraneous digits.

However, it took another two years for the British to create a machine that could decode the encrypted German messages quickly and reliably enough for that information to be useful. Going through the messages by hand took weeks. The first attempt at a Lorenz codebreaking machine compared a printout of the encrypted German message to another printout of various possible Lorenz encoding patterns. While this machine, known as the “Heath Robinson”, allowed codebreakers to ideally decode up to 1,000 characters a second, it depended on keeping the two paper printouts in sync with each other. The Colossus sidestepped this problem by replacing the decoding printout with what was basically a computerized Lorenz emulator that would electronically generate Lorenz encoding patterns and compare them to the encoded message. The Colossus Mk2 could easily decode 5,000 characters per second, meaning that paper printouts of encrypted German messages could be fed into the Colossus at a rate of 30 miles of paper per hour. The Colossus was even tested at a speed of over 9,000 characters per second, but paper printouts going at 60 miles per hour tended to disintegrate.

And no, for the handful of ‘70s sci-fi geeks reading this, none of the scientists involved was named “Forbin”.

The Colossus was so fast and efficient at doing its decoding job that during the rebuilding process the scientists involved claimed that a modern-day desktop PC wouldn’t be able to do a much faster job of decoding the same messages.

This is what we in the writing biz call “foreshadowing”.

The reason it took a good deal longer to rebuilt the Colossus than it’d take to solder together a Pong arcade machine is that due to the top-secret nature of the Colossus, eight of the ten Colossus machines were destroyed after WW2 (Winston Churchill supposedly decreed that they be demolished into “pieces no larger than a man’s fist”). The remaining two Colossi were destroyed and the diagrams for their construction were burned in 1960. The volunteers looking to rebuilt Colossus had to rely at first on only a handful of photographs and a few partial circuit diagrams that some of the engineers involved had secretly and illegally held on to.

Of course, once the rebuilt Colossus Mk2 was back in action, the scientists that rebuilt it wanted to show off how awesomely fast it was, so they devised a challenge. German radio enthusiasts would encrypt a message using a vintage Lorenz machine and then transmit it by radio, while scientists manning both the rebuilt Colossus and a “virtual Colossus” program being run on a laptop would wait to intercept the message and start a race to see how quickly they could decode the message. Amateur codebreakers were challenged to tune in for the encrypted message and try and beat the Colossus to the decoding punch. The suspense was, if not gripping, at least slathered in a layer of retro technogeekery thicker than London fog.

Would the WW2-era Colossus be able to beat those pesky newfangled PC whippersnappers and show them how to decrypt it old school?

No.

In what scientific terms is called an “anti-climax”, a German amateur codebreaker who had “written a suite of software specifically for the challenge” managed to decrypt the transmitted message before the British team even got a chance to start feeding it into their rebuilt Colossus.

To make things worse, the laptop virtual Colossus managed to decode the message several hours before the real deal did, although to be fair, most laptops don’t have to deal with exploding vacuum tubes.

Despite its Michael Jordan-esque comeback (Wizards, not Bulls), the rebuilt Colossus is at least going out in style, as it’s now the centerpiece of the British National Museum Of Computing.

No word yet if anyone’s been able to program it to play Tetris.