He was still living under this cloud when he died of a serious illness. Unfortunately the British authorities played dirty yet again and had Welchman put into a legal limbo where his security clearance was revoked and they threatened to prosecute as at that time things were getting “political” in Britain. It lead to a bitter row and Welchman leaving Britain for the US, where he wrote his book. However Welchman did not officially get credit, apparently that went to “Doc” Kean who made the engineering drawings up from Welchman’s sketches. Apparently what blew Turings sicks off was when he sketched out the diagonal board design infront of Turing. Eventually he was told about the Turing bombe after he had exolained his own method. On approaching his managment he was initially given the cold shoulder. He did this in his spare time over about a three week period. However Gordon Welchman was brought in compleatly uninitiated and came up with a design for his own bombe in issolation not knowing of Turings previous work. The story is Turing took considerable time to improve the Polish bomba possibly due to having to spend quite a bit of time dealing with incompetent managment. Sadly, Bletchley didn’t use Rejewki and company. Welchman came up with the diagonal board which cut down false stops. That’s not to say I would not like to own one, I could add it to my collection of cold war spy-sets and similar bits such as the 807 based antenna amplifier from a Y-Station. All in all even in a software implementation they really are not worth the effort from a security perspective. That’s not to say that rotor machines can not be secure in certain circumstances, but you really need to know what you are doing with wiring the rotors and stepping them. In essence you can ignore them and break the rotor polyalphabetic cipher then do a fairly simple “fix-up” frequency analysis to get the plain text. Nor will any rotor machine that uses an Enigma style “reflector”, “predictable rotor stepping”, or deficient rotor wiring…Īlso the “plug board” and “hour box” whilst apparently adding many many more states actually do not do that much as they become a simple substitution cipher for the whole time they are in use at any given setting. As a security researcher it really is important for you to emphasize that the four-rotor design is not secure
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