Editing Playfair cipher (section)

==History==
[[Image:Lyon Playfair.jpg|thumbnail|[[Lord Playfair]], who heavily promoted its use.]]
Playfair cipher was the first cipher to encrypt pairs of letters in cryptologic history.<ref>[https://books.google.com/books?id=3S8rhOEmDIIC&dq=%22the+cipher+is+the+first+literal+one%22&pg=PT220 ''The Codebreakers''] (1996) David Kahn, Scribner Books from Simon & Schuster </ref> [[Charles Wheatstone|Wheatstone]] invented the cipher for secrecy in [[telegraphy]], but it carries the name of his friend [[Lord Playfair]], first Baron Playfair of St. Andrews, who promoted its use.<ref name=":0">{{Cite web|url=https://www.nku.edu/~christensen/section%2019%20playfair%20cipher.pdf|title=Polygraphic Ciphers|last=Christensen|first=Chris|date=2006|website=Northern Kentucky University, Chris Christensen|access-date=January 9, 2018}}</ref><ref name=":1" /><ref name=":2" /> The first recorded description of the Playfair cipher was in a document signed by Wheatstone on 26 March 1854. 

It was initially rejected by the [[British Foreign Office]] when it was developed because of its perceived complexity. Wheatstone offered to demonstrate that three out of four boys in a nearby school could learn to use it in 15 minutes, but the Under Secretary of the Foreign Office responded, "That is very possible, but you could never teach it to attachés."<ref>{{Cite book|url=https://books.google.com/books?id=YpbKDTpVOAcC|title=Memoirs and Correspondence of Lyon Playfair: First Lord Playfair of St. Andrews ...|last=Reid|first=Thomas Wemyss|date=1899|publisher=Harper & Brothers|pages=158–159|language=en}}</ref> 

It was however later used for tactical purposes by British forces in the [[Second Boer War]] and in [[World War I]] and for the same purpose by the British and Australians during [[World War II]].<ref name=":1">{{cite book|last1=Kahn|first1=David|title=The Codebreakers: The comprehensive history of secret communi cation from ancient times to the internet|date=1996|publisher=Scribner|isbn=978-0684831305}}</ref><ref name=":2">{{Cite web|url=http://www.appstate.edu/~klimare/MAT3530_2_3.pdf|title=Secret Codes Through World War II|last=Klima|first=Rick|date=2018|website=Appalachian State University, Dr. Rick Klima|access-date=2018-01-09|archive-date=2017-10-13|archive-url=https://web.archive.org/web/20171013122801/http://www.appstate.edu/~klimare/MAT3530_2_3.pdf|url-status=dead}}</ref> This was because Playfair is reasonably fast to use and requires no special equipment - just a pencil and some paper. A typical scenario for Playfair use was to protect important but non-critical secrets during actual combat e.g. the fact that an artillery barrage of [[White phosphorus munitions|smoke shells]] would commence within 30 minutes to cover soldiers' advance towards the next objective. By the time enemy cryptanalysts could decode such messages hours later, such information would be useless to them because it was no longer relevant.<ref>{{cite book |last1=Lord |first1=Walter |title=Lonely Vigil: Coastwatchers of the Solomons |date=2012 |publisher=Open Road Media. Kindle Edition. |page=6 }}</ref> 

During World War II, the [[Government of New Zealand]] used it for communication among [[New Zealand]], the [[Chatham Islands]], and the [[coastwatchers]] in the Pacific Islands.<ref>[http://rnzncomms.org/ourhistory/chapter8/ "A History of Communications Security in New Zealand By Eric Mogon"], Chapter 8</ref><ref>{{cite web| title =The History of Information Assurance (IA)| work =Government Communications Security Bureau| publisher =New Zealand Government| url =http://www.gcsb.govt.nz/about-us/history-ia.html| access-date =2011-12-24| url-status =dead| archive-url =https://web.archive.org/web/20111112144636/http://www.gcsb.govt.nz/about-us/history-ia.html| archive-date =2011-11-12}}</ref> [[Coastwatchers]] established by [[Royal Australian Navy]] Intelligence also used this cipher.<ref>{{cite book |last1=Lord |first1=Walter |title=Lonely Vigil: Coastwatchers of the Solomons |date=2012 |publisher=Open Road Media. Kindle Edition. |page=6 }}</ref>