Editing Substitution cipher (section)

===Nomenclator===
[[Image:Babington postscript.jpg|thumbnail|right|The forged nomenclator message used in the [[Babington Plot]] in 1586]]
[[File:Nomenclator-French 17th cent.jpg|thumb|A French nomenclator code table]]
One once-common variant of the substitution cipher is the '''nomenclator'''. Named after the public official who announced the titles of visiting dignitaries, this [[cipher]] uses a small [[code (cryptography)|code]] sheet containing letter, syllable and word substitution tables, sometimes homophonic, that typically converted symbols into numbers. Originally the code portion was restricted to the names of important people, hence the name of the cipher; in later years, it covered many common words and place names as well. The symbols for whole words (''[[Code word (communication)|codeword]]s'' in modern parlance) and letters (''cipher'' in modern parlance) were not distinguished in the ciphertext. The [[Rossignols]]' [[Great Cipher]] used by [[Louis XIV of France]] was one.

Nomenclators were the standard fare of [[diplomacy|diplomatic]] correspondence, [[espionage]], and advanced political [[conspiracy (political)|conspiracy]] from the early fifteenth century to the late eighteenth century; most conspirators were and have remained less cryptographically sophisticated. Although [[government]] [[intelligence agency|intelligence]] [[cryptanalyst]]s were systematically breaking nomenclators by the mid-sixteenth century, and superior systems had been available since 1467, the usual response to [[cryptanalysis]] was simply to make the tables larger. By the late eighteenth century, when the system was beginning to die out, some nomenclators had 50,000 symbols.{{Citation needed|date=November 2015}}

Nevertheless, not all nomenclators were broken; today, cryptanalysis of archived ciphertexts remains a fruitful area of [[history|historical research]].