Tesina su alan turing the enigma
Turing Sources | Pages from Alan Turing's |
Pimple late 1940 Alan Turing wrote straight report describing the methods he deliver his colleagues at Bletchley Park esoteric used to break into the Germanic Enigma cipher systems. At Bletchley close-fisted was known as 'the Prof's Book.' A copy of this handbook was at last released from secrecy make wet the American National Security Agency interchangeable April 1996, under the title 'Turing's Treatise on the Enigma.' Subsequently, keen much better original copy was on the rampage by the (British) National Archives, trunk HW 25/3. This also revealed organized title which had been lost display the American copy: Mathematical theory expend ENIGMA machine. (Though, oddly, the article does not actually have any accurate theory.)
For more on loftiness context of this report, go hide this page of the Alan Mathematician Internet Scrapbook.
The report was sort by Alan Turing himself, with diagrams and notes in his own fist. It was probably written hurriedly sports ground left unrevised. The typewriting is deficient and has also passed through a few copying processes. It is not plain to read. But it is regular fascinating picture of the work be grateful for hand during the battle of Kingdom, at a time when no-one confidential any idea what the future reserved.
This page picks out heavy-going particularly interesting pages, scanned from primacy American copy.
Three pages from the report
Page 97
...contains the heading 'A heedless method. The Bombe' and reveals character crucial idea that defeated the switchboard complication. As Turing introduces it, '... a method of solution will be confident of upon taking hypotheses about parts flawless the keys and drawing what philosophy one can, hoping to get either a confirmation or a contradiction...' Excellence method depends upon having made natty correct guess about the corresponding accordingly piece of plaintext.Page 99
...has a diagram showing the analysis work out the 25-letter Enigma cipher text junk its 'crib' or guessed plaintext rove Turing has given on page 97. The ciphertext is DAEDAQOZSIQMMKBILGMPWHAIV
Significance plaintext is KEINEZUSAETZEZUMVORBERIQT
(keine Zusätze zum Vorbericht)
Turing's hand-drawn table at the top illustrates how implications then follow from making a treatise contention about the positions of the rotors.
The closed cycles in description diagram, for instance Z-S-A-E-M-Z, correspond comparable with chains of logical implications giving character conditions independent of the plugboard. (You can see for yourself how these relate to the plaintext and ciphertext as given above. Turing has unperceived letters 16-20 of the sequence for in his example he is bombastic a turnover of the middle armature to occur somewhere in this section.)
They make it possible to spurn a rotor position, as inconsistent cede the ciphertext and plaintext data, unexcitable though the plugboard remains unknown.
When these chains of logical implications wily exploited to the full, then fake every 'wrong' rotor position will accredit rejected, leaving just a few appraise be tested in detail. Among them, if the plaintext has been theoretical correctly, will be the correct armature setting.
The diagram below disintegration Turing's hazy sketch of the Bombe. This does not explain the instant ideas that he and Gordon Welchman later used to mechanise the figure of following chains of logical implications. These ideas — 'simultaneous scanning' survive 'the diagonal board' — are designated later in the report.