This week, Alex Chan was invited to give us a talk about Colossus, a British code-breaking machine from World War II. The former Queens’ student noted three remarkable facts about the Colossus: that it was created to decrypt a machine the British know nothing about; that it was created in such a short time frame; and that despite being a huge advance in computing at the time, it had almost no impact on the history of the modern computer.
Alex began with a brief description of the cipher that the Colossus was eventually built to crack, and the machine that was used to implement it. The folk at Bletchley Park knew none of this to begin with, and deduced it entirely by studying the intercepted messages — an incredible feat! Eventually, the team at Bletchley figured how how to decrypt the messages, but unfortunately the process was too slow. To speed this up, they built successively faster and more reliable machines, requiring less and less human input, and this resulted in the construction of the Colossus. This machine could translate any message in about 5 hours, and provided the British war effort with crucial intelligence in time for the D-Day landings in 1944.
In total, there were 10 Colossi at Bletchley Park. What made this collection special is that together, these machines were the first to be Turing complete — a key benchmark in measuring how powerful a computer is. Unfortunately, this achievement was buried deep under the veil of secrecy that covered all that transpired in Bletchley Park, which is why the Colossus did not make its rightful contribution to the field of computing. The talk concluded with a quick summary of the the timeline and how incredible it was that Colossus came around to be.
Apart from finding about a fascinating topic in the history of Computer Science, we also learned plenty from Alex’s polished presentation and delivery. Thank you for a wonderful talk!
University of Cambridge, Queens' College - Computer Science 