This is getting way off topic for UA, tell me to stop if this is more than anyone wants to see (but hey, the Sun isn't doing anything, so why not?) Polish cryptographers had cracked the 3-rotor Enigma in the early 30's, but it was an all-manual process. So they developed the bomba in the mid-to-late '30s. IIRC, the Poles had 6 bombas built (each bomba could simulate 6 Enigma machines). They were primitive versions of Turing's bombes (note the difference in spelling). They were hand-cranked, where the bombe was electric. I know they were working on more bombas to crack the 4 and 5 rotor machines developed later, but by 1939 it was a little hard for them to work on it. They were able to decrypt the diplomatic messages, since they still used the 3 rotor system, but the military started using the others. It didn't introduce complexity, the machines always used 3 rotors, but they had up to 5 to choose from...so it was a question of scale. The hand cranked versions took several hours to do a run, and Turing's were something like 10-20 minutes a run. With that many possible combinations, it was weeks to get complex messages decoded on the hand-cranked machines. Bletchley would still take days on the later messages. Even later enigmas added a plugboard so certain settings could be changed, and reflector wheels to further encrypt things. Again, nothing that wasn't known, but it just added complexity to the brute-force method of decryption that was used. It was only as fast as it was because of a few things like knowing a certain word or phrase was likely in the message, and the first 6 letters were 3 letters repeated that helped narrow down the possible combinations. For example if (german word for) 'capture' was thought to be in the message, they could spend their time looking at all the words with that length in it, and use that to backtrack the enigma settings. If they were wrong, well, it was back to square one and guess again. It was billions of possible combinations, and trillions in the later ones. So the algorithm for the bombe was previously developed by the Polish cryptographers, it wasn't workable for large scale timely cryptographic use until Turing came along (each of his bombes were 36 functionally equivalent Enigmas)--and even then it took a few others working on it (forget their names though) to refine them further. The British built 4 or 5 hundred of the devices, and the US Navy developed about that many--although the US versions were even more advanced, and further reduced the run time. I remember reading somewhere that in wartime Britain there were times they had trouble keeping power going to the bombes. The US didn't have any such issues, so were much speedier. Large pools of mathematicians were called upon to help as well...they became human computer pools to help jump start the programming menus of the bombes. It was really lucky that they were able to decrypt things at all. Really, the main weakness of the enigma was in using the same key for the day--so if a somewhat unimportant message was decrypted, everything for that day could be decrypted...so they had a larger pool of data to work with. Also, the german operators played fast and loose with some of their operational orders--they didn't rotate wheels as far as they needed to, send out easily deciphered first 6 letter combos, etc. Shows you that no matter how strong your encryption method is, the weakest point of a password system is the 6 inches between the user's ears. I've got some books somewhere around here on Bletchley if you are interested. When I was in school, I was really interested in cryptography, and gathered quite a few resource materials. There's even a military crypto museum in Maryland that I'd like to visit one of these days. Dan On Jun 23, 2012, at 11:25 PM, Larry Holmes wrote:
Dan, did not the English expand on the work performed with the drum style computer developed by the Polish cryptographers? I am in no way devaluing the work of Turing & the people at Bletchley, but the Poles originally broke the cyphers. Then, I believe, the Germans made some improvements, including one or two more rotors, etc., and then the Poles lost the ability to continue decoding the Enigma cyphers. But, I believe their bomba was essentially refined and up- graded by Turing. 73, lh
On 6/23/2012 4:11 PM, Daniel Holmes wrote:
Yeah, its a simple Turing machine.
Turing was a fascinating man. He invented the bombe, the machine used to break the enigma code during world war 2, and is considered the father of artificial intelligence with his Turing tests. He was a brilliant mathematician and cryptographer.
Turing machines are a hypothetical computational machine that help to understand the limits of mechanical computational algorithms. Turing tests are tests given to humans that try to have the human distinguish the answers given by a machine as indistinguishable from an humans answers. Basically to see how far we can go with artificial intelligence.
I've always wondered what modern computer science would look like if he hadn't committed suicide in his early forties.
Dan
-- Sent from my iPhone. Please pardon any mispelings or errors.
On Jun 23, 2012, at 3:38 PM, Patrick Wiggins <paw@wirelessbeehive.com> wrote:
Hi Chuck,
I don't think the image on the page is supposed to be a slide rule. Turing's device used a paper tape and I think that's what they are trying to show..
patrick
On 23 Jun 2012, at 15:30, Chuck Hards wrote:
I get the impression that nobody on the Google staff has ever used a slide rule.
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-- Daniel Holmes, danielh@holmesonics.com "Laugh while you can, monkey boy!" -- Lord John Whorfin