Gisbert Hasenjaeger

Gisbert F. R. Hasenjaeger (1 June 1919 – 2 September 2006) was a German mathematical logician. Independently and simultaneously with Leon Henkin in 1949, he developed a new proof of the completeness theorem of Kurt Gödel for predicate logic. He worked as an assistant to Heinrich Scholz at Section IVa of Oberkommando der Wehrmacht Chiffrierabteilung, and was responsible for the security of the Enigma machine.

Personal life Gisbert Hasenjaeger went to high school in Mülheim, where his father was a lawyer and local politician. After completing school in 1936, Gisbert volunteered for labour service. He was drafted for military service in World War II, and fought as an artillerist in the Russian campaign, where he was badly wounded in January 1942. After his recovery, in October 1942, Heinrich Scholz got him employment in the Cipher Department of the High Command of the Wehrmacht (OKW/Chi), where he was the youngest member at 24. He attended a cryptography training course by Erich Hüttenhain, and was put into the recently founded Section IVa "Security check of own Encoding Procedures" under Karl Stein, who assigned him the security check of the Enigma machine. At the end of the war as OKW/Chi disintegrated, Hasenjaeger managed to escape TICOM, the United States effort to roundup and seize captured German intelligence people and material. His doctoral students at Bonn included Ronald B. Jensen, his most famous pupil.

Work

Safety Testing the Enigma Machine In October 1942, after starting work at OKW/Chi, Hasenjaeger was trained in cryptology, given by the mathematician, Erich Hüttenhain, who was widely considered the most important German cryptologist of his time. Hasenjaeger was put into a newly formed department, whose principal responsibility was the defensive testing and security control of their own methods and devices. Hasenjaeger was ordered, by the mathematician Karl Stein who was also conscripted at OKW/Chi, to examine the Enigma machine for cryptologic weaknesses, while Stein was to examine the Siemens and Halske T52 and the Lorenz SZ-42.

Construction of Turing Machines In 1963, Hasenjaeger built a Universal Turing machine out of old telephone relays. Although Hasenjaeger's work on UTMs was largely unknown and he never published any details of the machinery during his lifetime, his family decided to donate the machine to the Heinz Nixdorf Museum in Paderborn, Germany, after his death. In an academic paper presented at the International Conference of History and Philosophy of Computing in 2012. Rainer Glaschick, Turlough Neary, Damien Woods, Niall Murphy had examined Hasenjaeger's UTM machine at the request of Hasenjaeger family and found that the UTM was remarkably small and efficiently universal. Hasenjaeger UTM contained 3-tapes, 4 states, 2 symbols and was an evolution of ideas from Edward F. Moore's first universal machine and Hao Wang's B-machine. Hasenjaeger went on to build a small efficient Wang B-machine simulator. This was again proven by the team assembled by Rainer Glaschick to be efficiently universal.

Comments on the Enigma Machine weakness It was only in the 1970s that Hasenjaeger learned that the Enigma Machine had been so comprehensively broken. It impressed him that Alan Turing himself, considered one of the greatest mathematicians of the 20th century, had worked on breaking the device. The fact that the Germans had so comprehensively underestimated the weaknesses of the device, in contrast to Turing and Welchman's work, was seen by Hasenjaeger today as entirely positive. Hasenjaeger stated: