Encryption department of the Wehrmacht High Command

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Soldiers from the OKW's secret radio reporting service encrypting or decrypting messages using the Enigma key machine

The Cipher Department of the High Command of the Wehrmacht (also: cipher of the OKW , in short, Chi or OKW / Chi ) was the Department of the Army , dedicated to the deciphering of the opposing message traffic and the security checkpoint own key processes such as the rotor cipher machine Enigma , before and dealt during the time of World War II . It was subordinate to the OKW and was the successor to the former Chi -stelle (encryption office) of the Reichswehr Ministry .

The founder of the encryption office in October 1920 was Lieutenant Buschenhagen. Rudolf Schmidt , brother of the "Enigma spy" Hans-Thilo Schmidt, was in charge of the Reichswehr cipher station from 1925 to 1928 . In 1931 Rudolf was promoted to lieutenant colonel and chief of staff in the intelligence department.

OKW / Chi is to be seen as a counterpart to OKH / Chi (actually: Inspection 7 Group VI in the General Army Office , in7 / VI for short ), i.e. the cipher group of the Army High Command (OKH), or its successor OKH / GdNA , i.e. the Office of the General of Intelligence in the OKH. Other counterparts or competing cryptanalytic services were the so-called B-Dienst of the Navy , the Research Office (FA) of the Air Force , Amt IV E (Defense) in the Reich Security Main Office (RSHA) and Pers Z , the encryption service of the Foreign Office (AA).

Short name

The official abbreviation "Chi" for the cipher department goes back - contrary to what one might assume - not from the Greek letter Chi , but solely from the first three letters of the word cipher department. The chi test (not to be confused with the chi-square test ), a tool in the cryptanalysis of texts as important as the cross-correlation function in the analysis of signals, was only proposed in 1935 by the American cryptanalyst Solomon Kullback and was when it was founded the Chi -stelle of the Reichswehr Ministry, the forerunner of the encryption department, still unknown during the Weimar Republic .

Insinuation

One of the now partially publicly accessible archive (see also: Weblinks ) of the Allied Target Intelligence Committee (TICOM) , then classified as TOP SECRET , shows the subordination of OKW / Chi within the OKW .

  • Encryption Department (Chi), Colonel Kettler

structure

Another interrogation protocol, also available in the TICOM archive, shows the organizational structure of the OKW / Chi at the end of the war.

  • Encryption Department of the High Command of the Wehrmacht, Department Head Colonel Kettler
    • Size Z, central tasks, Maj. Lober
    • Size I, organization and commitment, Hptm. Grotz
  • Main group A, Maj. Mettig
    • Size II, development of own key processes
    • Size III, key supply, Maj. Metzger

According to this, the encryption department, headed by Colonel Kettler, was divided into eight groups (group), beginning with group Z for central tasks such as personnel matters, administration and accounting, and the other groups I to VII, numbered with Roman numerals . The group I was responsible for organization and deployment, Group II for developing its own key processes and Group III for key supply. Group IV under Hüttenhain dealt with "analytical deciphering", and the task of group V was the "practical deciphering of the secret writings of foreign governments, military attaches and agents". Group VI recorded radio and press reports and evaluated them, and finally Group VII was responsible for evaluating, distributing and archiving the intelligence findings. Groups II and III as well as IV and V, which are particularly important for the actual cryptology, were organizationally combined into two main groups, namely main group A and main group B, which represented the classic division of tasks in cryptology. While main group A dealt with its own encryption methods and the security of its own secret communication against unauthorized decryption , main group B was responsible for cryptanalysis , i.e. breaking and obtaining information from encrypted foreign messages if possible. These two opposing areas of responsibility are also known as defensive and offensive cryptology. Below the group level, the encryption department was further subdivided into sections , for example Group II consisted of section IIa (camouflage procedures, service regulations, security check) under Captain Bernsdorf, section IIb ( codes and encryption) under Frick and section IIc (agent encryption) under Fritz Menzer .

Cryptanalysis

The American strip pusher M-138-A embodies one of the methods that OKW / Chi was able to break successfully

One of the most important tasks, initially the Chi department of the Reichswehr and, after the establishment of the Wehrmacht High Command in 1938, the encryption department, was cryptanalysis, i.e. the investigation of opposing encryption methods and, if possible, their deciphering. The main group cryptanalysis was headed since 1922 by Wilhelm Fenner (who was promoted to Ministerialrat in the summer of 1938 ) . He reported to Erich Hüttenhain as head of Group IV Analytical Cryptanalysis . A number of special cryptanalytic machines were designed and built here. This included a period and phase search device developed by Hüttenhains employee Willi Jensen to determine coincidences (" Doppler ") of two secret texts and their spacing, which worked according to the so-called "sawhorse principle". Jensen also developed a parallel point finder which, like the American "Tetra-Tester" , was able to automatically track down bigram , trigram and tetragram parallel positions when comparing two texts on the basis of the Kasiski test . In addition, an electro-mechanical differences computing device for stripping was superencryption served at over encrypted codes.

The German cryptanalyst Otto Buggisch carried out an analysis of the British key machine Typex , but, like all other German agencies, could not achieve a break-in. The TypeX remained unbreakable for the Germans.

Security control of own key procedures

Enigma radio message intercepted in Bletchley Park (Part two of a three-part message)

Another task of the OKW's encryption department was - in addition to offensive cryptology, i.e. cryptanalysis - defensive cryptology, i.e. checking and maintaining the security of one's own cryptosystems . For this purpose, the Division IVa Security Control headed by Karl Stein existed within Group IV with its own key procedures . There, 23-year-old Gisbert Hasenjaeger was specifically responsible for the security of the Enigma . The attack method on the Enigma, devised by the British code breaker Alan Turing and further improved by his colleague Gordon Welchman , was not recognized by Hasenjaeger. As a result, British code breakers in Bletchley Park , England , were able to continuously break radio messages encrypted with the German key machine using a special electromechanical machine (" Turing bomb ") throughout the entire World War II under the code name " Ultra " .

literature

  • Friedrich L. Bauer : Deciphered Secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin a. a. 2000, ISBN 3-540-67931-6 .
  • Friedrich L. Bauer: Historical Notes on Computer Science . Springer, Berlin 2009. ISBN 3-540-85789-3 .
  • Wilhelm Fenner : The history of the encryption department. Report on behalf of the head of the Ag WNV, January 1945.
  • Randy Rezabek: TICOM and the Search for OKW / Chi . Cryptologia. Rose-Hulman Institute of Technology. Taylor & Francis, Philadelphia PA 37.2013,2 (April), pp. 139-153. ISSN  0161-1194 .

Web links

Individual evidence

  1. ↑ Friedrich L. Bauer: Deciphered secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin a. a. 2000, p. 412.
  2. ^ A b Wilhelm Fenner: The history of the encryption department. Report on behalf of the head of the Ag WNV, January 1945, p. 1.
  3. ^ Friedrich L. Bauer: Historical Notes on Computer Science . Springer, Berlin 2009, p. 173. ISBN 3-540-85789-3 .
  4. ↑ Friedrich L. Bauer: Deciphered secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin a. a. 2000, p. 326ff and p. 357ff.
  5. ↑ Friedrich L. Bauer: Deciphered secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin a. a. 2000, p. 342.
  6. ^ TICOM DF-187A Organization of the Cryptologic Agency of the Armed Forces High Command , accessed: May 11, 2015
  7. ↑ TICOM I-39 Organization of OKH / Chi English and German, accessed: May 11, 2015
  8. ↑ Friedrich L. Bauer: Deciphered secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin a. a. 2000, p. 447.
  9. ↑ Friedrich L. Bauer: Deciphered secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin a. a. 2000, p. 338.
  10. ↑ a b Friedrich L. Bauer: Deciphered secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin a. a. 2000, p. 347.
  11. ^ Army Security Agency: Notes on German High Level Cryptography and Cryptanalysis. European Axis Signal Intelligence in World War II. Volume 2. Washington (DC), 1946 (May), p. 49. Retrieved Nov 22, 2010. PDF; 7.5 MB ( memento from June 11, 2014 in the Internet Archive )
  12. ^ Army Security Agency: Notes on German High Level Cryptography and Cryptanalysis. European Axis Signal Intelligence in World War II. Volume 2. Washington (DC), 1946 (May), p. 77. Accessed: Nov 22, 2010. PDF; 7.5 MB ( memento from June 11, 2014 in the Internet Archive )
  13. ↑ Friedrich L. Bauer: Deciphered secrets. Methods and maxims of cryptology. 3rd, revised and expanded edition. Springer, Berlin a. a. 2000, p. 429.
  14. ↑ Gordon Welchman : The Hut Six Story. Breaking the Enigma Codes. Allen Lane, London 1982, ISBN 0-7139-1294-4 , p. 230.