By Noah | March 12, 2012
Google has posted a nice little video about Bletchley Park and the Colossus machine, including nice remembrances of hardware designer Tommy Flowers. There’s also a posting about Tommy Flowers in the Google blog.
I had the opportunity to see the reconstruction of Colossus in operation, breaking actual codes, when I visited the British National Museum of Computing last year. “Lynetter” has posted to Youtube a video introduction to the reconstructed machine and also video of the late Tony Sale showing the reconstruction in operation. Unfortunately, when I visited, Tony had just recently died.
One twist on all this struck me as interesting: when Colossus was (partially) declassified in the mid 1970’s, books like The Ultra Secret claimed that it was used to break the German enigma code. Recently, more information has been declassified, and it’s now clear that’s wrong. The British did break the enigma at Bletchley park using a machine known as the Bombe. The Bombe (not bomb!) was not an electronic digital computer and it did not use valves (what we Americans call vacuum tubes). The Bombe was built of technology similar to old phone company rotary stepping switches and relays. Patch panels encoded information relating to the keys to be broken, and the switches would rotate through all possible positions until patterns suggesting a possible key match were detected. The switches would then stop in position, and from the final positions keys could be determined.
The enigma was used to encipher field and naval communications. In fact, we now know that Colossus, which was an electronic computer using large numbers of “valves” (along with relays, high speed paper tape, etc.) was built specifically to crack the much more difficult Lorenz cipher, which was used by the German high command. The British were thus able to decrypt traffic going to and from Adolf Hitler himself.