Who was Arne Beurling? According to Svensk Uppslagsbok (Swedish Encyclopaedia) he was ``Arne Karl August Beurling, born 5 February 1905, mathematician. Beurling defended his thesis in Uppsala in 1933 (Etudes sur un problème de majoration), senior lecturer same year, Ph.D in 1934, professor in 1937. Beurling is an ingenious and all-round scientist who has attained beautiful results in function theory, prime number theory, modern integration theory and in several other areas.'' After the war Arne Beurling was offered an excellent position at Princeton University in USA in 1954. In 1965 he was given Albert Einstein's office, No. 115, at The Institute for Advanced Study, a distinction granted very few people. Arne Beurling died in 1986.
It is now known that Professor Arne Beurling was the man behind the breaking of the German Geheimschreiber. David Kahn writes in ``The Codebreakers'', page 482: ``Quite possibly the finest feat of cryptanalysis performed during the Second World war was Arne Beurling's solution of the secret of the Geheimschreiber.'' Arne Beurling's greatness is given by the fact he had at his disposal only the teleprinter tapes with the cipher text. He had no access to any machine, no plaintext and no knowledge about the logical construction of the cipher machine. Everything had to be reconstructed, something which was done in a remarkably short time.
It is known that he based his analysis on only 24 hours of traffic intercepted on 25 May 1940. A quick analysis showed that the first assumptions probably were correct. A check was made with the traffic intercepted for 27 May. Two weeks later the construction principles for the cipher machine were solved.
On the other hand it is not known how he set about it. That secret Arne Beurling took with him in the grave. However, a reconstruction has been made by FRA (Forsvarets Radioanstalt). The credit for this reconstruction goes to Carl Gösta Borelius who served at the Defence Staff's crypto section, later on FRA, from 1941 to 1985. Borelius' description of the reconstruction work is the basis for what is shown here.