Walter Ernst Fricke (1 April 1915 – 21 March 1988) was a distinguished German professor of theoretical astronomy at the University of Heidelberg.
[1] He was a mathematician and cryptanalyst during World War II at the Wehrmacht signals intelligence agency, Inspectorate 7/VI from 1941 to 1942 (which would later become the General der Nachrichtenaufklärung.
After high school, he enrolled as a student at Frederick William University in East Berlin, studying astronomy, mathematics and physics.
His teachers there included Paul ten Bruggencate and August Kopff in astronomy, Erhard Schmidt in mathematics and Max von Laue in physics.
[2] In 1939, while resident at the Göttingen Observatory, he received his doctorate with a thesis titled Influence of a resisting agent in the dynamics of dense stellar systems (Einfluß eines widerstehenden Mittels in der Dynamik dichter Sternsysteme).
On 15 May 1941 he was posted to Inspektorate 7, the cipher bureau of the Wehrmacht (German Armed Forces) high command,[2] although as an astronomer he knew nothing about cryptography and cryptanalysis.
Professor Otto Heckmann, director of the Hamburg Observatory, tried to lure him back to continue working on problems specifically related to war work that he had been occupied with before he was drafted: tables of air and ship navigation, aerodynamic problems for aeroplanes traveling at speeds over 1300 km/hour as well as rockets flying at speeds of more than 3000 km/hour.
In 1953, after receiving a fellowship from the German Science Foundation, he went to the United States for a year, working at the Yerkes, Mount Wilson, Palomar and Princeton University Observatories.
[1] In addition, in 1951 he published with Otto Heckmann and Pascual Jordan an important work for the extension of Einstein's theory of gravity.
[1] The production of this kind of fundamental catalogue, which provided the astronomical representation of an inertial system, was part of the institute's important work.
His finest contribution to astronomy was the derivation, together with his colleagues and his predecessor August Kopff, of the Fourth Fundamental Catalogue (FK4), published in 1963.
[2] The Army, Air Force and Police used the Double Playfair system as a medium-grade hand cipher in World War II.
Hollerith counts (frequency analysis) were undertaken against messages from the Polish War, but as these were of a stereotypical nature, words could only be guessed after high-frequency digraphs (i.e. pairs of letters) had been created.
However, the solution was never used, as even though they believed 3000 letters would be enough to break a message, the Army never informed them what the actual volume of traffic was, so the system continued in use.
[2] Around the same time, he worked on the French C36 cipher machine with fixed lugs, designed by Boris Hagelin, which was solved by cribs.
Late in the war, the Hollerith machine section moved to Weimar, so Walter Fricke told the printer to make up a set of three-letter slugs of type corresponding to the code groups, which were called Logotypen.
Fricke found it to be excellent, a very secure and practical hand cipher, but he didn't know if it had been broken, with the English using 40 letters and large number of abbreviations.