Ludwig Föppl

Ludwig Föppl
Föppl on the western front during World War I
Born February 27, 1887 (1887-02-27)
Berlin, German Empire
Died May 13, 1976(1976-05-13) (aged 89)
Münster, West Germany
Citizenship German
Alma mater University of Göttingen
Scientific career
Fields Mathematics
Engineering
Cryptology
Thesis
  • Stabile Anordnungen von Elektronen im Atom (1912)
Doctoral advisor David Hilbert
Doctoral students Harald Ludvig Westergaard

Karl Ludwig Föppl (27 February 1887 in Leipzig – 13 May 1976 in Munich) was a German mechanical engineer who succeeded his father as Professor of Technical Mechanics at the Technical University of Munich. During World War I, Föppl worked as a cryptanalyst.[1] During World War II he worked as a mathematician and cryptographer, initially in Inspectorate 7/VI, and later in the war within General der Nachrichtenaufklärung.[2]

Since 1940, he has been a full member of the Bavarian Academy of Sciences.[3] Föppl was one of the earliest cryptoanalysts in the Germany Army, working at this profession during both the first and second world wars, eventually becoming Chief of Sixth Army’s Evaluation Office. His work was kept secret from both his family and his colleagues, even his assistant Friedrich L. Bauer, who would also become a well known cryptologist, never knew. The work of Hilmar-Detlef Brückner of the Bavarian State Archive (German: Bayerisches Hauptstaatsarchiv) brought Föppl to prominence. After he died, more of his papers were eventually brought to the light by his daughter Liselotte; they were called Lebenserinnerungen: Ludwig Föppl and fleshed out the work of Brückner by providing details of Föppl's work during World War I.[1]

Early life

Föppl was the son of August Föppl, a German structuralist and university lecturer as well as brother-in-law of the physicist Ludwig Prandtl. Föppl completed his Abitur in 1906 and studied mechanical engineering for two years at the Polytechnical Institute. He then spent a year at the University of Göttingen studying the theoretical aspects of engineering. He was promoted in 1912 to Dr Phil in mathematics, with a thesis titled Stable arrangements of electrons in the atom (German: Stabile Anordnungen von Elektronen im Atom).[1][4] He worked as an assistant to Felix Klein, a leading mathematician on Group theory, complex analysis and non-Euclidean geometry. In March 1914, Föppl habilitated in mathematics. He started teaching as a Privatdozent at the Physics Institute at the University of Würzburg, working with Wilhelm Wien.[1] From 1925-1955 he was Director of the Mechanical-Technical Laboratory of the Technical University of Munich.

In July 1918, Föppl became engaged to Friederike Pühn.[1]

Military life

World War I

At the beginning of the World War I, Föppl was keen to enlist and experience life at the front as part of the infantry, but found the process less than straightforward due to the high number of volunteer men enlisting. He ran into a friend of his parents, Peter Vogel, who taught mathematics at the Munich War Academy (German: Bayerische Kriegsakademie). Vogel suggested that Föppl would be better being able to serve by joining the wireless telegraphy service, and provided a contact for a colonel in the Ministry of War. Föppl subsequently followed through and became a volunteer in the Wireless Telegraphy Replacement Company.[1]

After finishing his basic training, Föppl was posted to Roubaix, arriving on 15 December 1914. The units remit to intercept wireless communications of the British Expeditionary Force and the ships of the Royal Navy in the channel. However, Föppl ended up working as a kitchen boy, as he was unable to transcribe nonencrypted messages due to his lack of French.[1] By early 1915, there were thousands of encrypted messages, which were believed by the German Army and German Navy to be unusable. Föppl sought permission to attempt to decipher them during his spare time.[1]

Föppl began by determining which messages had been encrypted using the same key; this was accomplished by looking for common sequences of characters. These messages were structured and transmitted in sets of five letters, transcribed on square paper, and each message was represented as a series of columns of letters. As an emergent property of this transcribing method, standard sequences of characters stood out readily.[1] Foppl focused on groups of four or more characters. When a sequence appeared more than once in a message, or in several messages, he indicated that it was enciphered with the same key. Having sorted all the messages into groups, he focused on the group which seemed easiest to analyse as it contained the largest number of messages and the most repetitions of common sequences. He used frequency analysis against the message, then compared it against the equivalent statistics for a plaintext English document. He was able to instantly determine the key. Since this key was still in use, the Roubaix station was able to start reading incoming messages that were encrypted with that key.[1] The news of the deciphering spread rapidly through the German Navy. The majority of the decrypts were related to British minesweeping operations in the English Channel.

The key that Föppl discovered was termed a Caesar[5] and the cipher was a variant of the Gronsfeld cipher. Föppl suggested it was used as it enabled the cipher clerk to encrypt messages very quickly and could be easily enciphered by ordinary sailors, with a key that was changed every few weeks, that could be broken within a single day.[1]

During this period Föppl read the lengthy daily telegrams sent by Second Sea Lord George Egerton and managed to break the cipher, the Allied Fleet Code that was long considered unbreakable by the German Navy, and was considered thus to be a new source of intelligence which was of the greatest importance. From July 1915, daily reports compiled by Foppl and Lieutenant Martin Braune, the director of marine intelligence (German Naval Intelligence Service), were now sent to senior staff. Vizeadmiral Hugo von Pohl stated:

They have proved to be a great help for our submarine and Zeppelin missions.

Föppl was promoted to sergeant (German: Vizwachtmeister) on the 9th January 1916 and subsequently promoted to Lieutenant on 14 July 1916, which was subsequently converted into a full commissioned officer post in the regular army on the August 1918. His promotion enabled him to build a small team which included physicists Dr Wilhelm Lenz and Dr Hans Rau. Föppl found that due to his work, he was able to rescue academically gifted individuals from the front line, for use as cryptanalysts and evaluators, an idealised sentiment which was not always successfully achieved. The mathematician Richard Courant offered several suggestions to Föppl, including one individual whom he arranged to be transferred to the unit but found out he was killed in action. By the end of the first world war, Föppl was head of Sixth Army’s Evaluation Office, located in Lille and then Tournai.[1] Ludwig Föppl was demobilized at the end of World War One.

World War II

In March 1938, Föppl was reactivated and told to report to Army HQ after the Anschluss, where he was sent to Vienna to work at a German wireless company. Upon arrival and some confusion as to his purpose, since he was now in his mid 50's, and with no uniform, and having spent the last 21 years during the interwar period employed as an academic. He was ordered to visit the TU Wien, where he meet the Rector of the Institute and attended a meeting of the Senate to answer extensive questions from staff and academics about the Anschluss. After a week, he was demobilized and sent back to Munich.[1]

On the 25th August 1939, Föppl was again reactivated and requested (ordered) to Army HQ in Berlin for assignment, which put his whole family into a deep depression. Föppl was assigned an Evaluation Office working on the Invasion of Poland. He was eventually asked to be posted closer to his family and was eventually posted to western Army HQ in Frankfurt, working in a cryptanalysis role. He susbquently made a request to move back to work at the Technical University of Munich and was discharged on 20 January 1940, with his military career at an end.[1]

Works

He was editor of the later editions of Vorlesungen über Technische Mechanik[6] of his father August Föppl (with Otto Föppl) and co-author of Drang und Zwan.

  • Practical voltage optics., Praktische Spannungsoptik with Ernst Mönch: 3rd Edition, Springer Verlag, 1972[7]
  • Elementary mechanics from the higher point of view., Elementare Mechanik vom höheren Standpunkt, Oldenbourg, 1959
  • Festigkeitslehre mittels Spannungsoptik with Heinz Neuber: Oldenbourg, 1935
  • The strict solution for rolling friction., Die strenge Lösung für die rollende Reibung, Munich, Leibniz-Verlag, 1947[8]
  • Tables and Tables of Strength Theory with Gerhard Sonntag., Tafeln und Tabellen zur Festigkeitslehre with Gerhard Sonntag: Oldenbourg, 1951[9]

Literature

  • Hilmar-Detlef Brückner: Germany's First Cryptanalysis on the Western Front – Decrypting British and French Naval Ciphers in World War I. Cryptologia. Rose-Hulman Institute of Technology. Taylor & Francis, Philadelphia PA 29.2005,1 (January), S. 1–22. ISSN 0161-1194.
  • Martin Samuels: Ludwig Föppl – A Bavarian cryptanalyst on the Western front. Cryptologia, 2016. doi:10.1080/01611194.2015.1084960

Honours

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Samuels, Martin (3 June 2016). "Ludwig Föppl: A Bavarian cryptanalyst on the Western front". Cryptologia (pdf)|format= requires |url= (help). Taylor and Francis Journals. 40 (4): 355–373. doi:10.1080/01611194.2015.1084960.
  2. ↑ "CSDIC (UK) SIR 1704 - Herzfeld. The organisation and history of the Cryptographic Service within the German Army". Google drive. CSDIC. 8 July 1945. p. Appendix 2. Retrieved 27 October 2017.
  3. ↑ "Prof. Dr. Ludwig Föppl". Bavarian Academy of Sciences. Bayerische Akademie der Wissenschaften. Retrieved 28 October 2017.
  4. ↑ Mehra, Jagdish; Rechenberg, Helmut (28 December 2000). The Historical Development of Quantum Theory. Springer Science & Business Media. p. 37. ISBN 978-0-387-95177-5. Retrieved 29 October 2017.
  5. ↑ Singh, Simon (2000). The Code Book: The Secret History of Codes & Code-breaking. London: Fourth Estate. pp. 9–14. |access-date= requires |url= (help)
  6. ↑ "University of Michigan Historical Math Collection". Michigan University Book Collection. The University of Michigan Historical Mathematics Collection. 19 April 2007. Retrieved 30 October 2017.
  7. ↑ Ludwig, Föppl; Ernst, Mönch (1950). Praktische Spannungsoptik. Springer-Verlag Berlin Heidelberg. ISBN 978-3-642-52730-2. Retrieved 30 October 2017.
  8. ↑ Föppl, Ludwig (1947). Die strenge Lösung für die rollende Reibung. Leibniz. Retrieved 30 October 2017.
  9. ↑ Föppl, Ludwig; Gerhard, Sunday (1951). "Tables and tables on strength theory German:Tafeln und Tabellen zur Festigkeitslehre" (pamphlet) (in German). Munich: Oldenbourg. OCLC 5734320. Retrieved 30 October 2017.
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