Editing History of cryptography (section)

== Cryptography from 1800 to World War I ==
{{Main|World War I cryptography}}
Although cryptography has a long and complex history, it wasn't until the 19th century that it developed anything more than ad hoc approaches to either encryption or [[cryptanalysis]] (the science of finding weaknesses in crypto systems). Examples of the latter include [[Charles Babbage]]'s [[Crimean War]] era work on mathematical cryptanalysis of [[polyalphabetic cipher]]s, redeveloped and published somewhat later by the Prussian [[Friedrich Kasiski]].  Understanding of cryptography at this time typically consisted of hard-won rules of thumb; see, for example, [[Auguste Kerckhoffs]]' cryptographic writings in the latter 19th century.  [[Edgar Allan Poe]] used systematic methods to solve ciphers in the 1840s. In particular he placed a notice of his abilities in the [[Philadelphia]] paper ''Alexander's Weekly (Express) Messenger'', inviting submissions of ciphers, most of which he proceeded to solve. His success created a public stir for some months.<ref>Silverman, Kenneth. ''Edgar A. Poe: Mournful and Never-ending Remembrance''. New York: Harper Perennial, 1991. p. 152-3</ref> He later wrote an essay on methods of cryptography which proved useful as an introduction for novice British cryptanalysts attempting to break German codes and ciphers during World War I, and a famous story, ''[[The Gold-Bug]]'', in which cryptanalysis was a prominent element.

Cryptography, and its misuse, were involved in the execution of [[Mata Hari]] and in [[Dreyfus affair|Dreyfus' conviction]] and imprisonment, both in the early 20th century. Cryptographers were also involved in exposing the machinations which had led to the Dreyfus affair; Mata Hari, in contrast, was shot.

In World War I the [[British Admiralty|Admiralty]]'s [[Room 40]] broke German naval codes and played an important role in several naval engagements during the war, notably in detecting major German sorties into the [[North Sea]] that led to the battles of [[Battle of Dogger Bank (1915)|Dogger Bank]] and [[Battle of Jutland|Jutland]] as the British fleet was sent out to intercept them. However, its most important contribution was probably in [[cryptanalysis|decrypting]] the [[Zimmermann Telegram]], a [[telegram|cable]] from the German Foreign Office sent via Washington to its [[ambassador]] [[Heinrich von Eckardt]] in Mexico which played a major part in bringing the United States into the war.

In 1917, [[Gilbert Vernam]] proposed a teleprinter cipher in which a previously prepared key, kept on paper tape, is combined character by character with the plaintext message to produce the cyphertext. This led to the development of electromechanical devices as cipher machines, and to the only unbreakable cipher, the [[one time pad]].

During the 1920s, Polish naval-officers assisted the Japanese military with code and cipher development.

Mathematical methods proliferated in the period prior to World War II (notably in [[William F. Friedman]]'s application of statistical techniques to cryptanalysis and cipher development and in [[Marian Rejewski]]'s initial break into the German Army's version of the [[Enigma (machine)|Enigma]] system in 1932).