The breaking of the Enigma Code is one of the most interesting stories in the history of computing -- but it's not necessarily easy to get your head around. Fortunately, this video provides an amazingly straightforward explanation of how the code was cracked.
James Grime, a mathematician from Cambridge University, explains how Turing and his coworkers managed to defeat the German encryption. It all stemmed from the fact that the code contained a subtle flaw: a letter was never encrypted in such a way that it was represented by itself once coded. From there, Turing was able to work out a solution.
Of course, the problem was that the code changed every night. So Turing built the Bombe: a machine that could crack the code, every morning, in just 20 minutes. At this point, I'll hand over to James -- who can describe the whole process far more elegantly than I could ever hope to. [YouTube]