Colossus: The Secret of Bletchley Park's Codebreaking Computers

"After Enigma, the Germans developed more powerful encryption with higher-speed digital equipment that was much harder to break. The British side, led by [the engineer] Tommy Flowers, built a vacuum tube machine called Colossus – an extremely powerful and sophisticated digital computer which helped the British to break these even stronger codes. By the end of the war there were at least 10 of these Colossus machines. Essentially, it was the birth of the computing industry at a time when no one else was building 10 copies of the same machine. But it was all kept under wraps at the end of the war. My suspicion is that it just didn’t go with the heroic history of the war to publicise that it was won partly by breaking codes and not purely by heroism in battle. Also, it may be a valid argument that we still depend on breaking codes and don’t want a new enemy to know how we are doing it. That’s certainly true in the US today. The NSA is a huge organisation that still keeps its secrets. But in the case of Bletchley Park and Colossus, I don’t think it’s done any harm to finally publicise what really happened. Copeland’s book is another masterpiece. I wish I had been able to read it 20 years ago, when I first became interested in this. It reveals in a very technically correct way how the German codes got broken. It’s a marvellous collection of first-person documents, memories and editorial glue to hold it all together. Yes they are. America sent people to Britain during and after the war, to learn what had been done, and Alan Turing came over to America to debrief the people who became the NSA. Very much so. There is still a cat and mouse arms race between computers which both make it easier to write harder codes and easier to break them."