 begin forwarded text delivered to fork URL to fork URL subject re optical analog computing from dave long dl silcom com sender fork admin URL date wed NUMBER oct NUMBER NUMBER NUMBER NUMBER NUMBER the first computer to crack enigma was optical computing with interference patterns etc makes perfect sense but enigma was cracked by building mechanical systems that were essentially enigma machines and brute forcing look for zygalski sheets by koerner s narrative it wound up being a hybrid affair bletchley had mock enigmas which cycled through the enigma s NUMBERk starting positions in a quarter of an hour but the germans started using a plugboard which then had NUMBER NUMBERxNUMBER NUMBER possibilities the poles noticed that there were some patterns in the messages which were only possible via certain plugboard settings and so when we have collected several such cards corresponding to different initial signals we place them in a pile so that the squares corresponding to the same daily settings are aligned and shine a light beneath the pile only those squares which let the light through will correspond to possible daily settings so the brute force hardware allowed precalculation of optical computing devices which then narrowed down the possibilities enough for brute force to again be used for daily decodes until on NUMBER may the germans invaded france and on the same day in accordance with the best cryptographic principles they changed their enigma procedures in such a way that the NUMBER zygalski sheets each with their carefully drilled NUMBER or so holes became just so much waste cardboard dave the first synthetic aperture radar processor was optical this is also easy to believe given dr elachi s description of the NUMBER shuttle imaging radar the received signal is recorded on an optical film which is retrieved after landing the film is then processed in an optical correlator to generate the final image which makes sense as one wishes to shift each component of the return in proportion to its frequency for which one presumably needs a glorified prism alternatively the signal can be digitized and then recorded on board or transmitted to the ground via a digital data link this was the case with the sensor flown in NUMBER koerner _the pleasures of counting_ in which various aspects of the enigma decoding cover four chapters of which i quote from two sections of one NUMBER NUMBER beautiful polish females and NUMBER NUMBER passing the torch churchill s romantic soul loved the excitement and secrecy surrounding bletchley he relished the way that t he old procedures like the setting up of agents the suborning of informants the sending of messages written in invisible ink the masquerading the dressing up the secret transmitters and the examining of the contents of waste paper baskets all turned out to be largely cover for this other source as one might keep some old established business in rare books going in order to be able under cover of it to do a thriving trade in pornography and erotica looking at the disparate unkempt and definitely unmilitary crew formed by his top code breakers he is said to have added to his head of intelligence i know i told you to leave no stone unturned to find the necessary staff but i did not mean you to take me so literally end forwarded text r a hettinga mailto rah ibuc com the internet bearer underwriting corporation URL NUMBER farquhar street boston ma NUMBER usa however it may deserve respect for its usefulness and antiquity predicting the end of the world has not been found agreeable to experience edward gibbon decline and fall of the roman empire 