Otto Buggisch (28 June 1910 – 15 September 1991) was a German mathematician who, during World War II, was a cryptanalyst working in the cipher bureau, the Cipher Department of the High Command of the Wehrmacht (OKW/Chi) responsible for deciphering of the opposing forces Communications. He also dealt with the security control of own key procedures. Through research and revelations exposed by two Polish officers, late in the war, he recognized the true cryptographic weaknesses of the Enigma rotor cipher, key machine used by the German armed forces to encrypt their secret communications, in World War II. History Buggisch graduated from the Ludwig-Georgs Gymnasium (LGG) in Darmstadt in 1928. He studied pure mathematics and physics and the subsidiary subject applied mathematics at the Technische Universität Darmstadt. In 1938, Buggisch was promoted to Dr. rer. nat. with a mathematical dissertation titled On the Rarity of Equations with Affect (German: Über die Seltenheit der Gleichungen mit Affekt) which was supervised by Udo Wegner at the Technische Universität Darmstadt. During the war, Buggisch held the military rank of a sergeant in group 7/VI at OKW/Chi. Military career 1940 From May 1940 to July 40, DBuggisch was posted to a Wireless Telegraphy (abbr. W/T) Listening Interpretation Station (colloquially Out-Station or Intercept station) of Army Group C in Bad Schwalbach, Bad Kreuznach, Saarbrücken. Buggisch was working with Hauptmann Mettig, a signals officer, who became second-in-command of OKW/Chi, the mathematician, Hauptmann Wolfgang Franz and Inspecktor Kühn. Cryptographic systems/ciphers worked on were F90, F110. F90 and F110 were German designations for French Army cipher systems before and during the Battle of France. These were based on 4-figure codes and in one case the recipher consisted of a periodic adder, or subtractor of length 11. In the other, it was ordinary transposition, the transposition key being obtained from a key word which itself was taken from the code and shown by an indicator group. Both systems were being read from the winter of 1939 to the end of the Battle of France in June 1940. Buggisch also worked on analysing the diagonal write-out transposition (Transposition cipher), C-36 cipher machine These were simple field codes. From 20 July 1940, he was posted and attached to an intercept station in Berlin at 29/30 Bendlerstrasse, where there were other specialist sections for interception of Russian and Balkan traffic. During this period, he undertook the completion of two works on the C-36