Fritz Nebel

Fritz Nebel, who lived from 1891 to 1977, was a German signals intelligence officer who served as a lieutenant in the army in the First World War and as a Luftwaffe officer in the Second. He is known as the inventor of the encryption method called the Secret Cipher of the Radio Operators 1918, in German Geheimschrift der Funker 1918 or GedeFu 18, which the Imperial German Army used from March 1918 on both the Western and Eastern Fronts until the war ended on 11 November 1918. The Allies, led by the French officer Georges Painvin, broke it and named it ADFGX and ADFGVX after its letters. In 1966 Nebel learned it had been broken, and said he had proposed a double columnar transposition that his superiors rejected for a simpler one. He met Painvin in 1968.