Editing ADFGVX cipher (section)

{{Short description|Type of cipher used in World War I}}
{{Use dmy dates|date=February 2021}}
In [[cryptography]], the '''ADFGVX''' cipher was a manually applied field [[cipher]] used by the [[German Army (German Empire)|Imperial German Army]] during [[World War I]]. It was used to transmit messages secretly using [[wireless telegraphy]]. ADFGVX was in fact an extension of an earlier cipher called '''ADFGX''' which was first used on 1 March 1918 on the German [[Western Front (World War I)|Western Front]]. ADFGVX was applied from 1 June 1918 on both the Western Front and [[Eastern Front (World War I)|Eastern Front]].

Invented by the Germans [[signal corps]] officers Lieutenant {{Interlanguage link|Fritz Nebel|de|Fritz Nebel}} (1891–1977)<ref>Friedrich L. Bauer: ''Decrypted Secrets, Methods and Maxims of Cryptology''. Springer, Berlin 2007 (4.&nbsp;Aufl.), S.&nbsp;173, {{ISBN|3-540-24502-2}}.</ref><ref>Friedrich L. Bauer: ''Decrypted Secrets, Methods and Maxims of Cryptology''. Springer, Berlin 2007 (4.&nbsp;Aufl.), S.&nbsp;53, {{ISBN|3-540-24502-2}}.</ref> and introduced in March 1918 with the designation "Secret Cipher of the Radio Operators 1918" (''Geheimschrift der Funker 1918'', in short ''GedeFu 18''), the cipher was a [[transposition cipher#Fractionation|fractionating]] [[transposition cipher]] which combined a modified [[Polybius square]] with a single columnar transposition.

The cipher is named after the six possible letters used in the ciphertext: {{code|A}}, {{code|D}}, {{code|F}}, {{code|G}}, {{code|V}} and {{code|X}}. The letters were chosen deliberately because they are very different from one another in the [[Morse code]]. That reduced the possibility of operator error.

Nebel designed the cipher to provide an army on the move with encryption that was more convenient than [[trench code]]s but was still secure. In fact, the Germans believed the ADFGVX cipher was unbreakable.<ref name="WWI_Codebreaking">{{cite web|url=http://www.vectorsite.net/ttcode_04.html#m3|title=Codes and Codebreaking in World War I|url-status=usurped|access-date=10 March 2010|archive-url=https://web.archive.org/web/20100503103848/http://www.vectorsite.net/ttcode_04.html#m3|archive-date=3 May 2010}}</ref>