It was called ENIGMA, and the product was code-named ULTRA.
To simplify enormously, the Enigma machine was a transposition cipher device with a typewriter keyboard. There were three rotors inside, each with twenty-six characters. When you struck a key, the first rotor advanced one position, until it reached twenty-six, and then the next rotor advanced, like an odometer. In other words, any given letter was substituted with another, but the possible combinations were twenty-six to the power of three. The rotor settings were predetermined, but they changed every day, in theory. One weakness Bletchley Park exploited was that the German operators didn't always change the settings daily. Another was that messages were sometime sent in plaintext, for redundancy, and you could compare the coded transmission to the uncoded one. If not for German security breaches, the coded traffic might well have proved unreadable.
In the North Atlantic, the convoys that were Britain's lifeline had no effective air cover or escorts, in 1940 and '41, and crossed two thousand nautical miles of unpatrolled open ocean. Here the wolfpacks hunted. The loss of Allied tonnage was crippling. Bletchley Park needed to break the U-boat codes or the resupply would founder.
|Model of the Bombe|
Alan Turing died in 1954. He was queer, and MI-5 hounded him, as a security risk. He underwent chemical castration, and was eventually driven to suicide, his contribution to the war effort unrecognized at the time of his death. Some thirty years later, Hugh Whitemore's play "Breaking the Code" opened in the West End, with the astonishing Derek Jacobi as Turing. Sodomy hasn't been criminally prosecuted in Great Britain since the repeal of the gross indecency acts in the late '60's. A legislative motion was introduced in Parliament to grant Turing a statutory pardon, just this past year.
I don't want to wade into the question of gay civil rights, although it seems to me obvious that without legal protection, homosexuals are still fair game. Turing was blackmailed by the law. His reputation doesn't deserve just rehabilitation. This has already happened. The computer library at King's College, Cambridge, for example, is now named after him, and he's widely accepted as a pioneer in Artificial Intelligence (the Turing test), and secure speech, the Delilah program. I'm saying that he deserves a posthumous knighthood, or an Order of Chivalry, at the least. This odd, cranky-pantsed fairy did as much to beat Hitler as any divisions in the field.
Churchill was later to say: "ULTRA won the war."
Editor's note: Software developer Terry Long has created a free Enigma Simulator. If you happen to use a Macintosh, download it and try it out.