Hans Rohrbach
| Hans Rohrbach | |
|---|---|
 |
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| Born |
27 February 1903 Berlin |
| Died | 19 December 1993 (aged 90) Bischofsheim an der Rhön |
| Theses |
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| Doctoral advisor | Issai Schur, Erhard Schmidt (1932) |
| Known for | Breaking the American diplomatic O-2 cypher which was a variant of the M-138-A strip cipher during World War II. |
| Influences | Ludwig Bieberbach, Eugen Blasius, Max Dessoir, Georg Feigl, Heinz Hopf, Wolfgang Köhler, Max von Laue, Karl Löwner, Richard von Mises, Max Planck, Hans Rademacher, Heinrich Rubens, Wilhelm Schlenk, Erhard Schmidt, Issai Schur, Gabor Szegö, Arthur Wehnelt, and Wilhelm Westphal |
| Notable awards | Order of Merit, Federal Cross of Merit, Order of Merit of Rhineland-Palatinate |
Hans Rohrbach was a German mathematician. He worked both as an algebraist and a number theorist and later worked as cryptanalyst at Pers Z S, the German Foreign Office cipher bureau, during World War II. He was latterly known as the person who broke the American diplomatic O-2 cypher, a variant of the M-138-A strip cipher during 1943. Rohrbach wrote a report on the breaking of the strip cypher when he was captured by TICOM, the allied effort to roundup and seize captured German intelligence people and material.
Hans Rohrbach was a son of journalist Paul Rohrbach and his wife Clara born Müller who were married in Berlin in 1897. There was always confusion around Rohrbachs' name, one source gives his full name as Hans Joachim Albert Rohrbach, while the mathematician Bernhard Neumann believed this full name to be Hans Wolfgang Rohrbach, and was sure his middle initial was a 'W'.
Rohrbach entered the Gymnasium (school) at Berlin-Friedenau in the Autumn of 1909 and studied there until Autumn 1917. He then entered the Fichte Gymnasium in Berlin-Wilmersdorf. After having successfully passed the school leaving exam in 1921, he entered the Friedrich-Wilhelm University in Berlin, where he studied mathematics, physics, and philosophy for two years. In 1923, as a head of the Berlin student organization Mathematisch-Physikalische Arbeitsgemeinschaft (Mathematics and Physics Working Group), he went with his father to the United States. The visit, which Rohrbach called his propaganda visit, was a tour of American universities to raise money for impoverished Berlin students. Germany's economy, which was undergoing a period of hyperinflation, was making life extremely difficult for students, who had to take employment to supplement their income.
In the autumn of 1924 Rohrbach resumed his studies at the University of Berlin and studied there until 1929. In the late 1920s he started work on his PhD thesis, titled Die Charaktere der binären Kongruenzgruppen mod p2 (The characters of the binary congruence groups mod p2), advised by Issai Schur. He submitted it and was awarded his doctorate on 25 July 1932.
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