Pers Z S

The Pers Z S was the symbol and the code name of the Chiffrierdienst, i.e. the Cryptanalysis Department or Signal Intelligence Agency of the German Foreign Office (German: Auswärtiges Amt) before and during World War II. Pers Z S was also called Special Service of Z Branch of the Foreign Office Personnel Department (German: Sonderdienst des Referats Z in der Personalabteilung des Auswärtigen Amtes)[1][2][3] Though similar in nature and operation to the OKW/Chi cipher bureau, it was a civilian operation as opposed to the military operation at OKW/Chi. According to TICOM interrogators it evinced an extraordinary degree of competence, primarily driven by a consistency of development not found in any other German signals bureau of the period.[4]

Short name

The letter "Chi" for the Chiffrierabteilung is, contrary to what one might expect, not the Greek letter Chi, nor anything to do with the chi test,[5] a common cryptographic test used as part of deciphering of enciphered message, and invented by Solomon Kullback, but only to the first three letters of the word Chiffrierabteilung (English:cipher department).

History

Little was known about Pers Z S before April 1945, when the first section was captured. TICOM, the United States effort to capture German intelligence assets after the war, found that captured documents provided little information on the execution of the unit, with the records of the Mathematical and Cryptological section having been destroyed. The field covered by Pers Z S, over 25 countries for a period of 25 years, stymied TICOM as so few interrogators were available, who also lacked experience in cryptographic diplomatic system, as this was the first TICOM investigation. Inevitably there were some areas which were not covered.

In May 1945, the usual approach by TICOM to force captured personnel to write homework describing processes used in a particular intelligence unit under interrogation was not fully developed.[6] The only document prepared as homework was prepared on 6 August 1945 by Professor Dr Hans Rohrbach, along with several of his Pers Z S colleagues, which described the cryptanalysis of the American O-2 strip cypher, which was considered a most significant piece of work.[6][7]

1919–1937

The original name for Pers Z S was unknown but was likely called Political Intelligence Department, and was placed with Bureau I (German: Abteilung), the normal administrative department in a German government organization at the time. As the cryptography unit grew, it changed its name to Personnel Bureau[8] It was later called Chiffrierabteilung, later still the Sonderdienst des Referats Z in der Personalabteilung des Auswärtigen Amtes. In 1925, it was known that both cryptographic and cryptanalysis were unified under a single director.

The strength of the organization during this period was unknown. In 1945 Dr Paschke and Dr Schauffler stated that between 20 and 30 people were employed in 1918. A May 1919 lists 63 personnel employed, and would likely cover clerks, administrators, communications and liaison individuals.[6] By 1930 the Pers Z S unit strength was around 50 personnel[9]

1937–1939

On November 1, 1937, Pers Z S has around 77 employees working and by July 1, 1938, this had decreased to 72 people.[10] It was thought that the cryptanalysis unit had around 20 people. Under interrogation, Paschke and Kunze estimated that in 1939, Pers S Z personnel was between 80 and 100 people.[11] A Document captured on December 1, 1939, showed a total strength of 92 people,[10] but another document stated that 45 new appointments were made between September 1, 1939, and November 1939.[10] Thus it would seem reasonable to assume that at the start of the war that Pers Z S had a personnel count of 50.

The available documentation from the 1937 to 1939 period indicate that Z Branch suffered personnel shortage and a certain inertia within management. The job descriptions (German: Begruendungen) attached to the recommendation for promotion documentation detailed that Dr. Kunze was a Specialist (German: Regierungsrat) since 1923 and that Dr Paschke had held the same grade since 1927.

Positions with comparable activities and responsibilities in other ministries are given the grade of Principle Specialist (German: Ministerialrat) or Senior Specialist (German: Oberregierungsrat). This is spite of the fact that the personnel concerned are usually younger and have less time in grade.[10]

Chi complained in 1938 that it couldn't function efficiently without additional personnel.[10] Ten of its thirteen cryptographers were over fifty years old, six of them over sixty.

Due to the overloading of the cryptographic section, outgoing messages cannot be enciphered and checked with the necessary care. This regrettable state of affair was most noticeable during May 1938 and September 1938, when the political atmosphere was at its tensest.

The cipher bureau was organized as follows:

Location Unit Strength Total
Luisenstift, Managed by Dr Schauffler Schauffler's Group 8
Paschke's Group 13
Scherschmidt's Group 10
Zastrow's Group 9
Karstien's Group 4
Hagen's Group 4
Records Group 3
Clerical Personnel 3 72
Jaegerstrasse 12 III, Managed by Dr Kunze Special Group Mathematical cryptanalysis 20 20

Wartime

Little is known about Pers Z at the start of the war.

By October 1, 1940, there were around 290 employees, with Dr Kunze reporting to TICOM that he had 53 people working in his section in January 1941 at the Jaegerstrasse location, and Dr Schauffler reporting that 88 personnel were employed in January 1941, at the Berlin-Dahlem Avenue location. As with other cipher bureaus, similar to the OKW/Chi, the high command bureau and B-Dienst, the Navy cipher bureau, Pers Z S suffered chronic shortage of personnel. On November 26, 1940, Pers Z S submitted a list of problems to high command, primarily due to staff shortages, including 17 major countries which were neglected.[12] Doctor Kunze requested an additional 57 employees, 28 of which would be employees on British and American problems and Dr Schauffler requested an additional 17.

Pers Z S underwent no major changes until December 1943 when the unit was partially evacuated from Berlin due to continuous bombing by the Allies. Dr Schauffler and Dr Pasche's unit remained in Berlin at Im Dol 2-6,5. The rest of the unit under Dr Karstien moved to Hirschberg in Krkonoše. The mathematicians under Dr Kunze, together with all Hollerith machinery was evacuated to Hermsdorf. Towards the end of war, in February and March 1945, the unit further fragments, with the spectre of the Russian advance, the personnel located in Hirschberg group was moved to Burgscheidungen and joined there by some of the former Berlin personnel in April. The mathematics based cryptanalysts subsection fragmented with some personnel moving to Mühlhausen, with the majority of the personnel moving to Zscheppelin, a small village, around 15 km west of Delitzsch. No intercept traffic was received after March 1945, however some cryptanalysis continued in Burgscheidungen on archive material until it was overrun in April.[13]

Key personnel

Administrative Section

Minister (Gesandter I. Klasse) Selchow was chief of the Z Branch. Little is known of his background, except it is known that he engaged in similar work during World War II.[14] One source states that he had been head of Z Branch (Referat Z) since 1919.[15] He is listed as a Principal Foreign Office Specialist (Vortragender Legationsrat) on November 1, 1935, with the rank of Minister in 1945. Little is known about his abilities, but statements from personnel in other cipher bureaus imply that he was jealous and secretive. His Pers Z S staff characterized him as a competent administrator who knew little about cryptography and cryptanalysis. He was last reported in Salzburg in March 1945 and disappeared from history.

Senior Specialist (Oberregierungsrat) Dr Roy was head of Administrative Section in Z Branch. He had been with Z Branch since the early 1920s. He was taken prisoner at Mühlhausen in April 1945, but was found to be of little importance to TICOM (the United States Target Intelligence Committee).

Senior Specialist Ernst Hoffman had seniority going back to 1919. From 1940, he was head of the Communication Section in Z Branch, a section newly created at the time.

Senior Specialist Dr Horst Hauthal was head of the Cryptographic Section in Z Branch. His rise in Z Branch was considered meteoric by his peers. He joined the Nazi Party in 1937 and was a committed Nazi. A mathematician and cryptographer, he joined in January 1940 and was promoted to senior specialist before 1945.

Linguistics Cryptanalytic Section

Senior Specialist (Oberregierungsrat) Dr Rudolf Schauffler, originally a mathematician, was the nominal head of the Linguistics and Cryptanalysis section from at least November 1, 1937, and was the senior cryptanalyst in the section. He joined Z branch immediately after World War I. His main field of interest was theoretical research ((German: Grundlagenforschung) on cryptologic methodology.[16] His language specialties were Japanese and Chinese, which was also the cryptanalytic desk he headed. He also served as the primary advisor to the Foreign Office Cryptographic Section (Pers Z S Chi) on Security [17]

Senior Specialist Dr Adolf Paschke[18] became joint head of the Linguistics and Cryptanalytics section along with Schauffler during the latter half of World War II. He joined the Foreign Office group in 1919, and became a senior specialist between 1937 and 1940. In 1941, he was recommended to the rank of Principal Foreign Office Specialist (Vortragender Legationsrat). He was responsible for report publishing and translators. He was also responsible for liaison with the German armed forces. His language specialties were Italian, Greek and Russian.

Karl Zastrow was a Technical Assistant (German: Wissenschaftlicher Hilfsarbeiter). A senior member of the Cryptanalytic Section, he entered service in December 1918. Known for being a gifted analyst, he was never promoted due to being absent minded. He headed the American and Scandinavian group which was directed by Dr Hans-Kurt Mueller, with Zastrow as his deputy. He was the unit's expert on American Systems.[19]

Dr Wilhelm Brandes was a Senior Specialist (German: Oberregierungsrat). Dr Brandes headed the group directed by Dr Paschke, which worked to penetrate cyphers of Dutch, Swiss, Belgian or French origin. Having worked with Dr Paschke in World War I, he started working for Pers Z S in 1920. Known for being a capable linguist, archivist and bookbuilder, he had also certain liaison functions for his own group.

Dr Herrmann Scherschmidt was a Senior Specialist (German: Oberregierungsrat). Starting at the Foreign Office in May 1919,[20] he specialized in Slavonic and Near Eastern languages. He headed the Pers Z S Turkish group from 1934 to 1939. Thereafter he took over the Slavonic group until September 1943.[21] Wanting to return to the Turkish group, but unable to do so, he transferred to the translations unit (Foreign Office Document section) until September 1944. He then returned to his old group (Turkish, under Dr Paschke),[22] while Dr Benzing, the then current head of unit, shifted to Arabian and Iranian systems.

Dr Hans-Heidrun Karstien. Dr Karstien joined Pers Z S sometime before 1930. In November 1937, he was an unclassified employee ((German: Tarifangestellter) in Group X, then the highest pay grade. He specialized in Japanese and Chinese systems and cyphers, which he worked on from 1930 to 1938. In November 1940, he was listed as a Specialist in Balkan languages, handling Bulgarian, Croatian, Polish, Slovakian and possibly Finnish cyphers. He was taken prisoner in April 1945.

Dr Johannes Benzing[23] joined Pers Z S on July 20, 1937. He was the youngest senior official (German: Beamter) in the Pers Z S unit. A linguist, he was a specialist in Near Eastern languages and originally worked under Dr Scherschmidt. He headed this section from October 1939 until September 1944. He was then placed in charge of work for Iranian, Iraqi and Afghanistani systems.

Dr Ursula Hagen was a Technical Assistant (Grade IV) (German: Wissenschaftliche Hilfsarbeiterin).[24] It was considered difficult for women in Pers Z S to achieve proper recognition or seniority, and Dr Hagen was a case in point. Born March 23, 1901, she entered the unit on October 1, 1922. By 1939 to 1945, she was head of the group, her immediate manager being Dr Paschke. She was responsible for work in England, Ireland, Spain, Portugal and Latin American countries. As manager of the group, she was responsible for 12 staff.[25] Her grade and remuneration were never comparable to similar staff who had the same responsibilities and who were men. She was captured at Zschepplin in 1945 and evacuated to Marburg.

Dr Hans-Kurt Mueller was a Technical Assistant (Grade III), Born on May 1, 1906, he started working in Pers Z S on January 22, 1940. Specializing in American and Scandinavian systems, he was listed as Zastrow's deputy (Geman:Vertreter) at that time. By April 1945 however, he is listed as head of the group, and Zastrow as his deputy[26]

Dr Peter Olbricht was a former anthropologist with the Ethnographic Museum (German: Museum für Völkerkunde), located at Prinz Albrecht and Königgrätzer in Berlin and started working for the unit in December 1939. An orientalist of some repute, he specialized in Chinese, Japanese and Manchurian codes, working under the direction of Dr Schauffler. He was in the Hirschberg group from December 1943, and was eventually captured at Burgscheidungen.

Miss Asta Friedrichs.[27] While holding a low rank, she was however, one of the leading personalities of Pers S Z, she joined in September 1940 after studying at the Sorbonne and the America University in Sofia. Working with Dr Karstien, she deputized in the Slavonic Group when needed, while specializing in Bulgarian.

Miss Hildegarde Schrader was a Technical Assistant (Grade IV). Miss Schrader joined Pers Z S in September 1939, and specialized in French codes. In 1943 she was deputy to Dr Brandes in the French-Belgian-Swiss section and took over from Brandes when he fell ill in 1944, in Hirschberg. She was captured at Burgscheidungen.

Dr Otfried Deubner[28] was employed as a Technical Assistant (German: Wissenschaftlicher Hilfsarbeiter) Grade III. Dr Otfried started work with unit on July 7, 1940. By the end of the war, he was assistant to Dr Paschke in the group which handled the Vatican, Italian, Greece and the USSR desks. He was recommended for Specialist in 1941 but decided to stay as a Technical Assistant.

Mathematical and Cryptological Section

Senior Specialist Dr Werner Kunze[29] was a cryptanalyst and mathematician with 25 years of Pers Z S experience. A military cryptologist in World War I, he joined the Foreign Office in 1919. Kunze's subsection, the Mathematical-Cryptanalytic subsection, operated apart from the main Pers Z S department (Stammabteilung). His subsection consisted of linguist mathematicians, and he was also responsible for the Pers Z S IBM (Hollerith) machinery. They specialized in difficult systems and complex message encryption, and those problems which required a large outlay of expenditure of both time and personnel, or the applications of technical devices.[30] In December 1939, his group had 20 members.

Prof Dr Hans Rohrbach was a professor of mathematics at the Charles University in Prague. Dr Rohrbach split his duties equally between teaching and cryptanalysis. He started at Pers Z S in early 1940 as a Senior Civil Servant (German: Höherer Beamter).[31] Having an excellent command of the English language, he worked on English, American and Scandinavian as well as on the Japanese desk.[32] Through personality alone, he was one of the leading members of Pers Z S. He was awarded the War Service Cross 2nd Class (German: Kriegsverdienstkreuz II. Klasse) in September 1944 for his work on the solution of the U.S. Diplomatic Strip System O-2.

Dr Helmut Grunsky, a mathematician, started working at Pers Z S in September 1939. Previously he was teaching and conducting research at the Prussian Academy of Sciences. He was Technical Assistant Grade III (Wissenschaftlicher Hilfsarbeiter) in December 1940, and was recommended for promotion to Specialist (Regierungsrat) on March 5, 1941.

Dr Hans-Georg Krug. Little is known of when he joined Pers S Z but it was probable that he joined in early 1940. In 1941 he was recommended for promotion to Specialist. At the end of the war he was in charge of all Pers Z S Hollerith installations and other custom machinery.[33]

Dr Erika Pannwitz. It is not known when Dr Pannwitz joined Pers Z S, but was head of a group of cryptanalysts in April 1945[34]

Klaus Schultz joined Pers Z S after the start of World War II. A professional mathematician and statistician, he worked for the German Statistical Office ((German: Statistisches Reichsamt) before the war. He worked with Dr Kunze's section on December 1, 1939. His last known civil service grade was Technical Assistant Grade III (Wissenschaftlicher Hilfsarbeiter) on March 5, 1941, and he was never promoted during the war[34]

Dr Annelise Hünke started working at Pers S Z on August 31, 1939, as a Technical Assistant Grade III.

Dr Karl Schröter joined Pers Z S in the Spring of 1941. A mathematical theoretician at the University of Münster, he received his doctorate under Heinrich Scholz. In 1948 he was professor of mathematics at Humboldt University of Berlin and 1964 became a member of the German Academy of Science. He worked independently on Japanese additive and encipherment systems.

Personnel Seconded from OKW/Chi

Dr Arthur Grosse, who specialized in Chinese and Japanese codes, Edgar Hierer, a minor cryptanalyst, who also worked on Japanese and Chinese codes and Cort Rave, or Kurt Rave, also specializing in Japanese, Chinese code, were members of OKW/Chi and were seconded to Pers Z S in December 1943 after OKW/Chi was bombed out of their building, the Bendlerblock, located in Tirpltzufer section in Berlin. Working on the Chinese and Japanese desk, Dr Hans Rohrbach commented:

...definitely lower grade personnel and had come here to be trained[35]

Professor Dr Cort Rove stated in letter with Dr Otto Leiberich and Jürgen Rohwer that his team of linguists and cryptanalysts, solved on a daily basis, the Japanese PURPLE diplomatic cipher[36]

Operations

Intercept Network

Pers Z S has a single intercept station, called the Landhaus in Dahlem, that was used to cover priority communications, e.g. between Berlin and Ankara or Berlin to Lisbon,[37] however for message intercepts Pers Z S received the bulk from OKW/Chi, Hermann Göring's Research Office of the Reich Air Ministry (FA) and the German Post Office(German:Reichspost). Traffic intercepts sources were generally unknown as the traffic intercept had undergone post-processing before arriving at Pers Z S. When the FA was bombed out, the traffic was received direct from the Reichspost.[37]

Cryptographical Achievements

Organization

Per Z S grew organically before World War II and as with any small organization it grew more along with personnel factors than a logical plan. Although Dr Schauffler was the unit's leader during the interwar period, Dr Paschke, a more successful cryptanalyst, forceful personality and a Nazi, assumed more of a leadership role. However, TICOM interrogations could find no definitive documentation to assert who led the unit in 1945. It was possible there was none, but it seems probable that Dr Paschke in deference to Dr Schauffler's seniority, no actual administrative changes had occurred. Dr Kunze was the leading mathematical cryptanalyst.

Liaison

Liaison with Inspektorate 7 and OKH/GgNA

As regards Inspektorate 7/VI, (OKH/Chi), the cipher department of the German Army (Wehrmacht), and the concomitant unit OKH/GgNA, there was few examples of collaboration between it and Pers Z S at the senior administrative level. Dr Otto Buggisch, formerly of Inspektorate 7/VI and later OKW/Chi, gave the only available information to TICOM. Dr Buggisch worked in the French language group in Inspektorate 7 from November 1941 until August 1942 and during this period he collaborated with Dr Kunze on a five-digit DeGaulle code. He also worked Dr Kunze regarding the Swiss Enigma[38] General Alfred Jodl, Chief of the Armed Forces Operations Staff (Oberkommando der Wehrmacht) stated he did not receive any decodes [39] as they went directly to the Foreign minister, but knew in a general way Pers Z S professionalism and commitment.[40] The general lack of collaboration between Pers Z S and Inspektorate 7 didn't point to lack of coordination at senior administrative function, nor to professional jealously between the two agencies. Essentially the two agencies had two distinct operational foci. Pers Z S was diplomatic and OKH/Chi was a military agency. Therefore, there was little need for detailed collaboration.

Liaison with B-Dienst

As with the Army, the Navy had few occasions to work with Pers Z S. Their operation and tactical problem domains were too dissimilar to stimulate effective collaboration. Admiral Karl Dönitz, stated:

[he] had no knowledge of the cryptanalytic bureaus maintained by the other services and departments... As for civil bureaus, he had never tried to find out, [as] they were of no use to him.[41]

Wilhelm Tranow of the B-Dienst knew Dr Schauffler slightly and they had once collaborated over Japanese intercepts, but Tranow never had the time to address them[42] Miss Hagen reported in 1942 that the English desk had sent their results on the British B30 and B31 cypher's to B-Dienst, but had received nothing in return[43] It may, perhaps, not have occurred to Miss Hagen that the cypher's would have been no interest to B-Diesnt, as Pers Z S cryptanalysts were never exposed to the intelligence value of intercepts, in the same manner that other agency staff sometimes were.

Liaison with OKL-Stelle

Similar to the other agency, the Luftwaffe cipher bureau, OKL-Stelle was primarily interested in intercepts emanating from its Allied counterparts. As a military agency, diplomatic traffic would have probably been outside it's scope. However, there were two main concomitant instances of collaboration. According to Dr Schauffler, the first of these occurred in 1939, when Dr Kunze was approached by OKL-Stelle for assistance on British weather ciphers[44] Nothing is known to the extent of the success of the collaborative effort.

The second area of collaboration was noted by Chief Cryptanalyst Specialist Erich Hüttenhain of the OKW/Chi on a Letter dated July 27, 1943 which stated:[45]

Three weeks ago a discussion was held in the Foreign Office between Dr Kunze [and] Regierungsrat Dr Voegele, (Chief of the Luftwaffe cryptanalysts). Dr Voegele declared his willingness to cooperate on the AM10 cypher, (German name for a U.S Strip System) and Dr Kunze declared his willingness to provide the necessary material.
Voegele was held off for a fortnight. When he pressed for the production of the promised material, Dr. Kunze stated that he had changed his mind and would not be providing the material, as Dr. Voegele had made disparaging remarks about his work.
Suggestion: LIV or he head of the OKW/Chi should arrange for Paschke for the already planned collaboration of Pers Z S with the OKL-Stelle OBdL actually to come into force. Should Pers Z S not consent, OKW/Chi will terminate the agreement with Pers Z S to get a free hand, so that OKW/Chi can collaborate with the Air Force...

This incident is not mentioned in the Pers Z S or Dr Voegele interrogations and it suggests that the collaboration between Pers Z S and the Chi-Stelle was not all that it seemed.

Liaison with Research Office of the Reich Air Ministry

An unsigned letter, dated 23 February 1934, that was probably written by Dr Paschke stated:

Captain Oschmann...mentioned an utterance by his chief, Korvettenkapitaen Paztzig, to the effect that all cryptanalytic connections with the Forschungsamt should be dropped, since cryptanalytic work did not belong in the province of the Forschungsamt.[46]

The letter probably does not represent the then Pers Z S attitude, but it does constitute the first indication in the Pers Z S TICOM documentation to a new third competitor Goering's Research Office of the Reich Air Ministry, informally called the Forschungsamt. The later material of Pers Z S collaboration is fragmentary and none later than 1942. Although no dates are given, Hermann Göring stated:

...the Foreign Office had continuously tried to interfere [with the Research bureau].[47]

The statement might have been motivated by his professional competitive and aversion to Joachim von Ribbentrop, the diplomat and foreign minister under the Nazi regime but also that both agencies covered the same field and that there was unfortunately almost complete duplication.[48] Dir Paschke's statement that in general there was less liaison with the Forschungsamt than with the OKW/Chi[49]

The unit received a certain amount of its intercepts from the FA. Until November 1943, when the FA was bombed, it acted as the forwarding agent for the traffic intercepted by the Postoffice, both radiogram and cablegrams intercept traffic, which was forwarded to Pers Z S directly[50] After the FA was bombed out, the unit received the intercepts direct from the postoffice. There was little evidence of an official liaison between the two bureau's. Minister Seifert of the FA stated that intelligence produced by the FA was distributed to all departments including the Pers Z S...At some of these departments we had a liaison officers.[51] A Dr. Gerstmeyer is details as the FA-Pers Z S Liaison Officers (German:Verbingungs-mann).[52] Sauerbier of the FA stated that liaison with the unit ... was handled by a single representative, and never involved any exchange of visit's by operations personnel[53]

When the Pers Z S was interrogated by TICOM Team 1, they first learned the existence of the FA from the foreign office cryptanalysts, who knew the names of many of the section heads in Department IV in which their work was related[54] The Yearly Report for 1942 from AA/Per Z S inter alia, reveals an exchange of code book recoveries. The name of Senior Specialist Waechter of the FA appears in the Yearly Report and the names of other FA personnel occur in the code books stored in the AA/Per Z archives.[55] From this evidence it is clear that technical cryptanalyst liaison existed between the FA and the AA/Per Z.

Out of this evidence the following tentative assertions can be made for the period 1940-1942:

  1. There was extensive duplication of effort between AA/Pers Z S and the FA.
  2. There was an official liaison between the FA and AA/Pers Z S, but it didn't seem to be fully operative.
  3. There was significant amount of technical cryptanalyst liaison when both agencies were working on the same problem, with a concomitant exchange of information.
  4. It was unknown whether the liaison continued until the end of the war.

Notes

TICOM, the United States effort to seize German Intelligence after World War 2, document archive consists of 11 primary documents Volume I to Volume IX. These primary volumes, are aggregate summary documentation, each volume targeting a specific German military agency. The archive also consists of Team Reports, DF-Series, I-Series, IF-Series and M-series reports which cover various aspects of TICOM interrogation.

Volume VI which covers AA/Pers ZS contains over 50 references to the I-Series TICOM documents which are TICOM Intelligence reports, and covers references to the full gamut of the other types of reports, e.g. DF-Series, IF-Series, of which there are over 1500 reports. The following are those document directly referenced in this article:

References

  1. ↑ "Foreign Office Cryptanalytic Section" (PDF). NSA. p. 2. Retrieved 5 July 2016.
  2. ↑ Peter F Matthews (1 May 2013). SIGINT: The Secret History of Signals Intelligence in the World Wars. History Press. pp. 145–. ISBN 978-0-7524-9301-5.
  3. ↑ R. A. Ratcliff (14 August 2006). Delusions of Intelligence: Enigma, Ultra, and the End of Secure Ciphers. Cambridge University Press. pp. 67–. ISBN 978-0-521-85522-8.
  4. ↑ Peter Matthews (2 September 2013). SIGINT: The Secret History of Signals Intelligence in the World Wars. History Press. pp. 145–. ISBN 978-0-7524-9301-5.
  5. ↑ David Kahn (5 December 1996). The Codebreakers: The Comprehensive History of Secret Communication from Ancient Times to the Internet. Simon and Schuster. p. 574. ISBN 978-1-4391-0355-5.
  6. 1 2 3 "Foreign Office Cryptanalytic Section" (PDF). NSA. p. 2. Retrieved 30 September 2016.
  7. ↑ I-89
  8. ↑ I-1 Page 14
  9. ↑ I-22 Statement of Dr Rohrbach, who didn't join Pers Z S until after the war.
  10. 1 2 3 4 5 TF 24
  11. ↑ I-22 Para 125
  12. ↑ TF 24, Letter of Nov. 26, 1940
  13. ↑ "Foreign Office Cryptanalytic Section" (PDF). NSA. p. 9. Retrieved 8 November 2016.
  14. ↑ I-143 Paragraph 44
  15. ↑ I-1 Page 17
  16. ↑ I-22 Paragraph 8
  17. ↑ I-84 Paragraph 11
  18. ↑ Friedrich L. Bauer (24 November 2006). Decrypted Secrets: Methods and Maxims of Cryptology. Springer Science & Business Media. p. 415. ISBN 978-3-540-48121-8.
  19. ↑ I-22, Page 24
  20. ↑ DF-17 T3273
  21. ↑ I-63 Page 2
  22. ↑ Jefferson Adams (1 September 2009). Historical Dictionary of German Intelligence. Scarecrow Press. p. 345. ISBN 978-0-8108-6320-0.
  23. ↑ "Johannes Benzing", Verzeichnis der Professorinnen und Professoren der Universität Mainz (in German), Johannes Gutenberg-Universität Mainz, Gutenberg Biographics, retrieved 9 November 2016
  24. ↑ TF 24, 1941 Personnel List
  25. ↑ D-16, Report 4, Page 6
  26. ↑ I-22, Page 25
  27. ↑ Shawn Rosenheim (1997). The cryptographic imagination: secret writing from Edgar Poe to the Internet. Johns Hopkins University Press. p. 164. ISBN 978-0-8018-5331-9.
  28. ↑ David Alvarez; Robert A. Graham (5 November 2013). Nothing Sacred: Nazi Espionage Against the Vatican, 1939-1945. Routledge. p. 170. ISBN 978-1-135-21714-3.
  29. ↑ Friedrich L. Bauer (9 March 2013). Decrypted Secrets: Methods and Maxims of Cryptology. Springer Science & Business Media. p. 84. ISBN 978-3-662-03452-1.
  30. ↑ I-22 Page 25
  31. ↑ TF 24, Undated Personnel List
  32. ↑ I-89 Page 3
  33. ↑ T. W. Körner (5 December 1996). The Pleasures of Counting. Cambridge University Press. pp. 370–. ISBN 978-0-521-56823-4.
  34. 1 2 TF 24, List of personnel submitted by Doctor Kunze in April 1945.
  35. ↑ I-22, Paragraph 50
  36. ↑ Bauer, Friedrich L. (2007). "Decrypted Secrets, Methods and Maxims of Cryptology" (4th ed.). Springer-Verlag, Berlin, Heidelberg, New York. ISBN 3-540-24502-2.
  37. 1 2 I-22 Paragraph 103
  38. ↑ I-58, Pages 5-6
  39. ↑ I-143, Paragraph 12
  40. ↑ I-143, Page 5
  41. ↑ I-143 Paragraph 26
  42. ↑ I-147, Page 2
  43. ↑ I-172, Paragraph 14
  44. ↑ I-22, Paragraph 22. It is assumed by TICOM that Dr Schauffler meant the Luftwaffe okl-stelle rather than the Hermann Göring's Research Office of the Reich Air Ministry
  45. ↑ D-60, Page 5. It must be remembered that Pers Z S had solved the O-2 strip cypher and the Luftwaffe was interested in similar systems, such as CENEB cypher used by United States Army Air Forces, rather than the O-2 cypher.
  46. ↑ DF-17
  47. ↑ I-143, Paragraph 59
  48. ↑ I-143, Paragraph 49
  49. ↑ I-22, Para 101
  50. ↑ I-22, Paragraph 103
  51. ↑ I-25, Page 2
  52. ↑ I-54, Page 4
  53. ↑ I-163, Page 4
  54. ↑ IF-15
  55. ↑ D-16
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