Editing History of cryptography (section)

== World War II cryptography ==
<!-- This section is linked from World War II -->
{{See also|World War II cryptography|Cryptanalysis|List of cryptographers}}
[[Image:Enigma.jpg|thumb|The [[Enigma machine]] was widely used by Nazi Germany; its cryptanalysis by the Allies provided vital [[Ultra (cryptography)|Ultra]] intelligence.]]
By World War II, mechanical and electromechanical [[cipher|cipher machines]] were in wide use, although—where such machines were impractical—[[code book]]s and manual systems continued in use. Great advances were made in both cipher design and [[cryptanalysis]], all in secrecy. Information about this period has begun to be declassified as the official British 50-year secrecy period has come to an end, as US archives have slowly opened, and as assorted memoirs and articles have appeared.

===Germany===
The Germans made heavy use, in several variants, of an electromechanical [[rotor machine]] known as [[Enigma machine|Enigma]].<ref>{{cite web|url=http://www.egress.com/history-of-encryption-infographic/|title=Infographic - The History of Encryption|website=www.egress.com|access-date=19 March 2018}}</ref> Mathematician [[Marian Rejewski]], at Poland's [[Biuro Szyfrów|Cipher Bureau]], in December 1932 deduced the detailed structure of the German Army Enigma, using mathematics and limited documentation supplied by Captain [[Gustave Bertrand]] of French [[military intelligence]] acquired from a German clerk. This "was one of the great achievements of cryptology," according to historian [[David Kahn (writer)|David Kahn]]. <ref>{{cite book|last1=David Kahn|title=The Codebreakers|date=December 1996|publisher=Simon and Schuster|isbn=9781439103555|page=1073|url=https://books.google.com/books?id=SEH_rHkgaogC|access-date=25 November 2015}}</ref> Rejewski and his mathematical Cipher Bureau colleagues, [[Jerzy Różycki]] and [[Henryk Zygalski]], continued reading Enigma and keeping pace with the evolution of the German Army machine's components and encipherment procedures for some time. As the Poles' resources became strained by the changes being introduced by the Germans, and as war loomed, the [[Biuro Szyfrów|Cipher Bureau]], on the Polish [[General Staff]]'s instructions, on 25 July 1939, at [[Warsaw]], initiated French and British intelligence representatives into the secrets of Enigma decryption.

Soon after the [[invasion of Poland]] by Germany on 1 September 1939, key [[Biuro Szyfrów|Cipher Bureau]] personnel were evacuated southeastward; on 17 September, as the [[Soviet invasion of Poland|Soviet Union attacked Poland]] from the East, they crossed into [[Romania]]. From there they reached Paris, France; at [[PC Bruno]], near Paris, they continued working toward breaking Enigma, collaborating with British [[cryptologist]]s at [[Bletchley Park]] as the British got up to speed on their work breaking Enigma. In due course, the British cryptographers{{snd}}whose ranks included many chess masters and mathematics dons such as [[Gordon Welchman]], [[Max Newman]], and [[Alan Turing]] (the conceptual founder of modern [[computer|computing]]){{snd}} made substantial breakthroughs in the scale and technology of [[cryptanalysis of the Enigma|Enigma decryption]].

[[German code breaking in World War II]] also had some success, most importantly by [[B-Dienst#Combined Naval Cipher No. 3|breaking the Naval Cipher No. 3]]. This enabled them to track and sink Atlantic convoys. It was only [[Ultra (cryptography)|Ultra]] intelligence that finally persuaded the admiralty to change their codes in June 1943. This is surprising given the success of the British [[Room 40]] code breakers in the previous world war.

At the end of the War, on 19 April 1945, Britain's highest level civilian and military officials were told that they could never reveal that the German Enigma cipher had been broken because it would give the defeated enemy the chance to say they "were not well and fairly beaten".<ref>{{cite news| url=https://www.telegraph.co.uk/news/main.jhtml?xml=/news/2006/06/22/nenigma22.xml&sSheet=/news/2006/06/22/ixuknews.html | archive-url=https://web.archive.org/web/20071215125646/http://www.telegraph.co.uk/news/main.jhtml?xml=/news/2006/06/22/nenigma22.xml&sSheet=/news/2006/06/22/ixuknews.html | url-status=dead | archive-date=15 December 2007 | location=London | work=The Daily Telegraph | first=Ben | last=Fenton | title=Enigma and the British code of honour | date=22 June 2006}}</ref>

The German military also deployed several [[teleprinter]] [[stream cipher]]s. Bletchley Park called them the [[FISH (cryptography)|Fish cipher]]s; [[Max Newman]] and colleagues designed and deployed the [[Heath Robinson (codebreaking machine)|Heath Robinson]], and then the world's first programmable digital electronic computer, the [[Colossus computer|Colossus]], to help with their cryptanalysis. The German Foreign Office began to use the [[one-time pad]] in 1919; some of this traffic was read in World War II partly as the result of recovery of some key material in South America that was discarded without sufficient care by a German courier.

The ''[[Schlüsselgerät 41]]'' was developed late in the war as a more secure replacement for Enigma, but only saw limited use.

===Japan===
A US Army group, the [[Signals Intelligence Service|SIS]], managed to break the highest security Japanese diplomatic cipher system (an electromechanical [[stepping switch]] machine called [[Purple code|Purple]] by the Americans) in 1940, before the attack on Pearl Harbor. The locally developed Purple machine replaced the earlier "Red" machine used by the Japanese Foreign Ministry, and a related machine, the M-1, used by Naval attachés which was broken by the U.S. Navy's [[Agnes Driscoll]].  All the Japanese machine ciphers were broken, to one degree or another, by the Allies.

The Japanese Navy and Army largely used code book systems, later with a separate numerical additive. [[US Navy]] cryptographers (with cooperation from British and Dutch cryptographers after 1940) broke into several [[Imperial Japanese Navy|Japanese Navy]] crypto systems. The break into one of them, [[JN-25]], famously led to the US victory in the [[Battle of Midway]]; and to the publication of that fact in the [[Chicago Tribune]] shortly after the battle, though the Japanese seem not to have noticed for they kept using the JN-25 system.

===Allies===
The Americans referred to the intelligence resulting from cryptanalysis, perhaps especially that from the Purple machine, as '[[Magic cryptography|Magic]]'. The British eventually settled on '[[Ultra (cryptography)|Ultra]]' for intelligence resulting from cryptanalysis, particularly that from message traffic protected by the various Enigmas. An earlier British term for Ultra had been 'Boniface' in an attempt to suggest, if betrayed, that it might have an individual agent as a source.
[[Image:SIGABA-patent.png|right|320px|thumbnail|SIGABA is described in {{US patent|6175625}}, filed in 1944 but not issued until 2001.]]

[[Allies of World War II|Allied]] cipher machines used in World War II included the British [[TypeX]] and the American [[SIGABA]]; both were electromechanical rotor designs similar in spirit to the Enigma, albeit with major improvements. Neither is known to have been broken by anyone during the War. The Poles used the [[Lacida]] machine, but its security was found to be less than intended (by Polish Army cryptographers in the UK), and its use was discontinued. US troops in the field used the [[M-209]] and the still less secure [[M-94]] family machines. British [[Special Operations Executive|SOE]] agents initially used 'poem ciphers' (memorized poems were the encryption/decryption keys), but later in the War, they began to [[Leo Marks|switch]] to [[one-time pad]]s.

The [[VIC cipher]] (used at least until 1957 in connection with [[Rudolf Abel]]'s NY spy ring) was a very complex hand cipher, and is claimed to be the most complicated known to have been used by the Soviets, according to David Kahn in ''Kahn on Codes''. For the decrypting of Soviet ciphers (particularly when ''one-time pads'' were reused), see [[Venona project]].

===Role of women===
The UK and US employed large numbers of women in their code-breaking operation, with close to 7,000 reporting to Bletchley Park<ref>{{cite news|url=https://www.smithsonianmag.com/smart-news/women-were-key-code-breaking-bletchley-park-180954044/|title=Women Were Key to WWII Code-Breaking at Bletchley Park|first=Marissa|last=Fessenden|publisher=Smithsonian Magazine|date=27 January 2015|access-date=10 May 2019|quote=At its height there were more than 10,000 people working at Bletchley Park, of whom more than two-thirds were women.}}</ref>  
and 11,000 to the separate US Army and Navy operations, around Washington, DC.<ref name=mundy>{{cite book|last=Mundy|first=Liza|title=Code Girls: The Untold Story of the American Women Code Breakers of World War II|publisher=Hachette Books|location=New York, Boston|date=2017|isbn=978-0-316-35253-6}}</ref> By tradition in Japan and [[Kinder, Küche, Kirche|Nazi doctrine]] in Germany, women were excluded from war work, at least until late in the war. Even after encryption systems were broken, large amounts of work were needed to respond to changes made, recover daily key settings for multiple networks, and intercept, process, translate, prioritize and analyze the huge volume of enemy messages generated in a global conflict. A few women, including [[Elizabeth Friedman]] and [[Agnes Meyer Driscoll]], had been major contributors to US code-breaking in the 1930s and the Navy and Army began actively recruiting top graduates of women's colleges shortly before the attack on Pearl Harbor. Liza Mundy argues that this disparity in utilizing the talents of women between the Allies and Axis made a strategic difference in the war.<ref name=mundy />{{rp|p.29}}