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Hans Rohrbach
Hans Rohrbach (27 February 1903 – 19 December 1993) 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 (née 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.
While studying at Berlin University, Rohrbach met fellow student Rose Gadebusch (born 1905), who studied mathematics starting in 1925. Gadebusch took a major role in the Mathematisch-Physikalische Arbeitsgemeinschaft. After graduation she took a position at the Women's Gymnasium. Rohrbach married her sometime around 1932.
In 1936, Rohrbach was appointed senior assistant at the University of Göttingen. In 1937, he undertook his habilitation there with a thesis paper titled Ein Beitrag zur additiven Zahlentheorie nebst einer Anwendung auf eine Gruppentheoretische Frage (A contribution to additive number theory together with an application on a group theoretical question).
On 1 April 1938 he was appointed as a senior assistant at the Mathematical Institute of the German University of Prague. In 1941 he was promoted to extraordinary professor and in 1942 he became an ordinary professor. He also served as Director of the Mathematical Institute there.
Rohrbach was a member of the Nazi Party and the Sturmabteilung (the party's original paramilitary wing, later superseded by the SS), but was considered not fully reliable due to his friendship with Jewish colleagues.
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Hans Rohrbach
Hans Rohrbach (27 February 1903 – 19 December 1993) 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 (née 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.
While studying at Berlin University, Rohrbach met fellow student Rose Gadebusch (born 1905), who studied mathematics starting in 1925. Gadebusch took a major role in the Mathematisch-Physikalische Arbeitsgemeinschaft. After graduation she took a position at the Women's Gymnasium. Rohrbach married her sometime around 1932.
In 1936, Rohrbach was appointed senior assistant at the University of Göttingen. In 1937, he undertook his habilitation there with a thesis paper titled Ein Beitrag zur additiven Zahlentheorie nebst einer Anwendung auf eine Gruppentheoretische Frage (A contribution to additive number theory together with an application on a group theoretical question).
On 1 April 1938 he was appointed as a senior assistant at the Mathematical Institute of the German University of Prague. In 1941 he was promoted to extraordinary professor and in 1942 he became an ordinary professor. He also served as Director of the Mathematical Institute there.
Rohrbach was a member of the Nazi Party and the Sturmabteilung (the party's original paramilitary wing, later superseded by the SS), but was considered not fully reliable due to his friendship with Jewish colleagues.