Encrypt

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 ciphers, rediscovered 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, of which he proceeded to solve almost all. His success created a public stir for some months. He later wrote an essay on methods of cryptography which proved useful as an introduction for novice Room 40 British cryptanalysts of attempting to break German codes and ciphers during World War I.

In 1917, Gilbert Vernam proposed a teletype 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 lead to the development of the one time pad and the use of electromechanical devices as cipher machines.

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 system) in 1932. Both cryptography and cryptanalysis have become far more mathematical since WWII. Even so, it has taken the wide availability of computers, and the Internet as a communications medium, to bring effective cryptography into common use by anyone other than national governments or similarly large enterprises.

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