Editing History of cryptography (section)

== Medieval cryptography ==
[[File:Al-kindi cryptographic.png|right|thumb|The first page of [[al-Kindi]]'s manuscript ''On Deciphering Cryptographic Messages'', containing the first descriptions of cryptanalysis and frequency analysis.]]
{{See also|Classical cipher|Voynich manuscript}}
[[David Kahn (writer)|David Kahn]] notes in ''[[The Codebreakers]]'' that modern cryptology originated among the [[Arabs]], the first people to systematically document cryptanalytic methods.<ref>{{cite book|last1=Kahn|first1=David|title=The Codebreakers: The Comprehensive History of Secret Communication from Ancient Times to the Internet|date=1996|publisher=Simon and Schuster|isbn=9781439103555|url=https://books.google.com/books?id=3S8rhOEmDIIC&q=Arabs+cryptology+born}}</ref> [[Al-Khalil ibn Ahmad al-Farahidi|Al-Khalil]] (717–786) wrote the ''Book of Cryptographic Messages'', which contains the first use of [[wikt:permutation|permutations and combinations]] to list all possible [[Arabic language|Arabic]] words with and without vowels.<ref name="LB">{{cite journal|last=Broemeling|first=Lyle D.|title=An Account of Early Statistical Inference in Arab Cryptology|journal=[[The American Statistician]]|date=1 November 2011|volume=65|issue=4|pages=255–257|doi=10.1198/tas.2011.10191|s2cid=123537702}}</ref>

The invention of the [[frequency analysis]] technique for breaking monoalphabetic [[substitution cipher]]s, by [[Al-Kindi]], an [[Mathematics in medieval Islam|Arab mathematician]],<ref>{{cite book|url=https://books.google.com/books?id=2wS2CAAAQBAJ&q=al+kindi+Arab%2F&pg=PA279|title=The Biographical Encyclopedia of Islamic Philosophy|first=Oliver|last=Leaman|date=16 July 2015|publisher=Bloomsbury Publishing|isbn=9781472569455}}</ref><ref>{{cite book|url=https://books.google.com/books?id=3xJjNG5CNdwC&q=Al+Kindi+Arab%2F&pg=PA199|title=History of Islamic Philosophy: With View of Greek Philosophy and Early History of Islam|first=I. M. N.|last=Al-Jubouri|date=19 March 2018|publisher=Authors on Line Ltd|isbn=9780755210114}}</ref> sometime around AD 800, proved to be the single most significant cryptanalytic advance until World War II. Al-Kindi wrote a book on cryptography entitled ''Risalah fi Istikhraj al-Mu'amma'' (''Manuscript for the Deciphering Cryptographic Messages''), in which he described the first cryptanalytic techniques, including some for [[polyalphabetic cipher]]s, cipher classification, Arabic phonetics and syntax, and most importantly, gave the first descriptions on frequency analysis.<ref>
[[Simon Singh]], ''[[The Code Book]]'', pp. 14–20</ref> He also covered methods of encipherments, cryptanalysis of certain encipherments, and statistical analysis of letters and letter combinations in Arabic.<ref>{{cite web | url = http://www.muslimheritage.com/topics/default.cfm?ArticleID=372 |title= Al-Kindi, Cryptgraphy, Codebreaking and Ciphers |access-date=12 January 2007 }}</ref><ref name="Kadi">[[Ibrahim A. Al-Kadi]] (April 1992), "The origins of cryptology: The Arab contributions", ''[[Cryptologia]]'' '''16''' (2): 97–126</ref> An important contribution of [[Ibn Adlan]] (1187–1268) was on [[sample size]] for use of frequency analysis.<ref name="LB"/>

In early medieval England between the years 800–1100, substitution ciphers were frequently used by scribes as a playful and clever way to encipher notes, solutions to riddles, and colophons. The ciphers tend to be fairly straightforward, but sometimes they deviate from an ordinary pattern, adding to their complexity, and possibly also to their sophistication.<ref>{{Cite journal|last=Saltzman|first=Benjamin A.|title=Ut hkskdkxt: Early Medieval Cryptography, Textual Errors, and Scribal Agency (Speculum, forthcoming)|url=https://www.academia.edu/35034685|journal=Speculum|year=2018 |volume=93 |issue=4 |page=975 |doi=10.1086/698861 |s2cid=165362817 }}</ref> This period saw vital and significant cryptographic experimentation in the West.

[[Ahmad al-Qalqashandi]] (AD 1355–1418) wrote the ''Subh al-a 'sha'', a 14-volume encyclopedia which included a section on cryptology. This information was attributed to [[Ibn al-Durayhim]] who lived from AD 1312 to 1361, but whose writings on cryptography have been lost. The list of ciphers in this work included both [[Substitution cipher|substitution]] and [[Transposition cipher|transposition]], and for the first time, a [[polyalphabetic cipher]]<ref>{{cite book |last1=Lennon |first1=Brian |url=https://books.google.com/books?id=jbpTDwAAQBAJ&pg=PT26 |title=Passwords: Philology, Security, Authentication |date=2018 |publisher=[[Harvard University Press]] |isbn=9780674985377 |page=26}}</ref> with multiple substitutions for each [[plaintext]] letter (later called homophonic substitution). Also traced to Ibn al-Durayhim is an exposition on and a worked example of cryptanalysis, including the use of tables of [[letter frequencies]] and sets of letters which cannot occur together in one word.

The earliest example of the homophonic [[substitution cipher]] is the one used by [[Duke of Mantua]] in the early 1400s.<ref>David Salamon [https://books.google.com/books?id=A88kvYwIVu0C Coding for Data and Computer Communications]. Springer, 2006.</ref> Homophonic cipher replaces each letter with multiple symbols depending on the letter frequency. The cipher is ahead of the time because it combines monoalphabetic and polyalphabetic features.

Essentially all ciphers remained vulnerable to the cryptanalytic technique of frequency analysis until the development of the polyalphabetic cipher, and many remained so thereafter. The polyalphabetic cipher was most clearly explained by [[Leon Battista Alberti]] around AD 1467, for which he was called the "father of Western cryptology".<ref name="Brief Hist"/> [[Johannes Trithemius]], in his work [[Polygraphia (book)|Poligraphia]], invented the [[tabula recta]], a critical component of the Vigenère cipher. Trithemius also wrote the ''[[Steganographia]]''. [[Giovan Battista Bellaso]] in 1553 first described the cipher that would become known in the 19th century as the [[Vigenère cipher]], misattributed to [[Blaise de Vigenère]].<ref>{{Citation |last= Rodriguez-Clark |first= Dan |title= Vigenère Cipher |publisher= Crypto Corner |year= 2017 |url= https://crypto.interactive-maths.com/vigenegravere-cipher.html }}</ref>
In Europe, cryptography became (secretly) more important as a consequence of political competition and religious revolution. For instance, in Europe during and after the [[Renaissance]], citizens of the various Italian states—the [[Papal States]] and the Roman Catholic Church included—were responsible for rapid proliferation of cryptographic techniques, few of which reflect understanding (or even knowledge) of Alberti's polyalphabetic advance. "Advanced ciphers", even after Alberti, were not as advanced as their inventors/developers/users claimed (and probably even they themselves believed). They were frequently broken. This over-optimism may be inherent in cryptography, for it was then – and remains today – difficult in principle to know how vulnerable one's own system is. In the absence of knowledge, guesses and hopes are predictably common.

Cryptography, [[cryptanalysis]], and secret-agent/courier betrayal featured in the [[Babington plot]] during the reign of Queen [[Elizabeth I of England|Elizabeth I]] which led to the execution of [[Mary, Queen of Scots]]. [[Robert Hooke]] suggested in the chapter ''Of Dr. Dee's Book of Spirits'', that [[John Dee]] made use of Trithemian steganography, to conceal his communication with Queen Elizabeth I.<ref>{{cite book|url=https://books.google.com/books?id=6xVTAAAAcAAJ|title=The Posthumous Works of Robert Hooke|page=203|author=Robert Hooke|year=1705|publisher=Richard Waller, London}}</ref>

The chief cryptographer of King Louis XIV of France was [[Rossignols#Antoine Rossignol|Antoine Rossignol]]; he and his family created what is known as the [[Great Cipher]] because it remained unsolved from its initial use until 1890, when French military cryptanalyst, [[Étienne Bazeries]] solved it.<ref>{{cite book|last1=Lund|first1=Paul|title=The Book of Codes|date=2009|publisher=University of California Press|location=Berkeley and Los Angeles, California|isbn=9780520260139|pages=[https://archive.org/details/bookofcodesunder0000unse/page/106 106–107]|url=https://archive.org/details/bookofcodesunder0000unse/page/106}}</ref> An encrypted message from the time of the [[Man in the Iron Mask]] (decrypted just prior to 1900 by [[Étienne Bazeries]]) has shed some, regrettably non-definitive, light on the identity of that real, if legendary and unfortunate, prisoner.

Outside of Europe, after the Mongols brought about the end of the [[Islamic Golden Age]], cryptography remained comparatively undeveloped. [[Cryptography in Japan]] seems not to have been used until about 1510, and advanced techniques were not known until after the opening of the country to the West beginning in the 1860s.