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The Index of Coincidence

created by legbagede

(thing) by legbagede (2.8 d) (print)   ?   (I like it!) 1 C! Wed Jul 05 2000 at 19:30:56

"... Cryptology became almost entirely a technology, an applied science in the service of power ...even though cryptanalysis is quintessentially statistical, cryptology did not take any steps of importance toward quantification until William F. Friedman in 1920 matched frequency distribution to reconstruct a plaintext alphabet in his groundbreaking The index of coincidence and its applications in cryptography (Geneva, Ill. : Riverbank Laboratories, 1922). -from David Kuhn, "The Grand Lines of Cryptology's development", Computers and Security , Nov. 1982.

Precursors of this text, however, for all the cypherpunk history geeks out there, also included Leon Baltista Albertiæ, who in 1466 adapted a disk device, which when turned in various combinations, generated an exhaustive list of arguments to convert Muslims (essentially the first disk polyalphabetic substitution cipher , using polyalphabetic substitution ).

Alberti's contemporary Johannes Trithemius (1462-1516) was at the same time mingling cryptographic methods with angelic script in his treatise Steganographia, hoc est, Ars per occultam scripturam animi sui voluntatem absentibus aperiendi certa (Frankfurt : 1608), which while only clocking in at 70 p. is still one of the earliest European works on the subject of invisible writing and practical cryptography .Oe
æAlbertis' treatise was entitled De Cifris, was 26p., and outlined the use of two interlocked rings, forming a disk, which could be rotated to produce different correspondences between opposed rings of letters- which may have been inspired by the Islamic astrolabe introduced to Europe the century beforehand, following the last Crusades.
Oe And should you be curious, and in the Montreal area, stop by McGill University , and if you can find the Rare Books room, then you can have a look for yourself . . .but bring photo ID.

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Cypherpunk The Hacker Crackdown polyalphabetic substitution cipher The "My parents suck with computers" node
Johannes Trithemius August 4, 1907 RC4 The Arabian contribution to Cryptology
hypercube Dictionary of Angels frequency analysis William F. Friedman
coincidence Analyzing spam: A journey into conspiracy theory and steganography Microsoft site server Incoincident
Dictionary of Sexology Triptych The Kinks Astrolabe
Applied Science McGill University Cryptography Cryptographic
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