The compromise of the Swiss diplomatic Enigma K cipher machine in WWII

In the course of WWII the Allied and Axis codebreakers attacked not only the communications of their enemies but also those of the neutral powers, such as Switzerland, Spain, Portugal, Turkey, Ireland, the Vatican State and others (1).

Switzerland was a traditionally neutral country but during the war it had close economic relations with Germany and it also acted as an intermediary in negotiations between the warring nations. Important international organizations like the Red Cross and the Bank of International Settlements were based in Switzerland.

Naturally both the Allies and the Germans were interested in the communications of the Swiss government.

Swiss diplomatic codes and ciphers

The Swiss Foreign Ministry used several cryptologic systems for securing its radio messages. According to US reports (2) several codebooks were used, both enciphered and unenciphered. These systems were of low cryptographic complexity but had an interesting characteristic in that the same codebooks were available in three languages.

French, German and Italian were the recognized official languages of Switzerland. The codebooks of the Swiss foreign ministry had versions in French, German and English.

Apart from codebooks the Swiss also used a number of commercial Enigma cipher machines at their most important embassies.

The Swiss Enigma K cipher machine

Since the 1920’s the Enigma cipher machine was sold to governments and companies that wanted to protect their messages from eavesdroppers.

The latest version of the commercial Enigma machine was Enigma K. In WWII this device was used by the Swiss diplomatic service and armed forces.

The device worked according to the Enigma principle with a scrambler unit containing an entry plate, 3 cipher wheels and a reflector. Each of the cipher wheels had a tyre, marked either with the letters of the alphabet or with the numbers 1-26, settable in any position relative to the core wheel, which contained the wiring. The tyre had a turnover notch on its left side which affected the stepping motion of the device.

The position of the tyre relative to the core was controlled by a clip called Ringstellung (ring setting) and it was part of the cipher key, together with the position of the 3 cipher wheels. 

The commercial version was different from the version used by the German Armed Forces in that it lacked a plugboard (stecker). Thus in German reports it was called unsteckered Enigma.

In 1938 the Swiss government purchased 14 Enigma D cipher machines, together with radio equipment. The next order was in 1939 for another 65 machines and in 1940 they received 186 Enigma K machines in two batches in May and July ’40. The Enigma cipher machines were used by the Swiss Army, Air Force and the Foreign Ministry (3).

Cipher machines of WWII

In the period 1939-45 most countries enciphered their communications using hand methods (codebooks, transposition etc). Only a few countries used cipher machines.

The following list covers these countries and the specific models they used.

United States

SIGABA

SIGCUM/Converter M-228 T/P

SIGTOT T/P (one time tape system)

CCM - Combined Cipher Machine

M-209 (US version of the Hagelin C-38)

AT&T double tape machine

Hebern cipher machine (5 rotor version)

SIGFOY/M-325 (Enigma type)

Britain

Typex (Enigma type)

Rockex T/P (one time tape system)

CCM - Combined Cipher Machine

Poland

Lacida

Soviet Union

K-37 (Hagelin B-211 copy)

Pogoda or Pagoda (copy of US AT&T double tape machine)

M-100/101 T/P

France

Hagelin B-211

Hagelin B-211 modified

Hagelin C-38 (US M-209 version)

Hagelin C-36

Sweden

Hagelin B-211

Hagelin C-38

Norway

Hagelin C-38

Holland

Hagelin C-38

Enigma G

Portugal

Hagelin C-38

Switzerland

Enigma K

Germany

Kryha

Enigma K

Enigma G

Enigma I (plugboard machine)

Enigma M4 (4 rotor naval version)

SG (Schlüsselgerät) 41 (Hagelin type)

SZ-40/42 T/P

T-52 T/P

T-43 T/P (one time tape system)

Italy

Enigma K

Enigma G

Enigma I

OMI NISTRI

Hagelin C-38

Olivetti T/P

Japan

RED/Angōki Taipu-A

PURPLE/Angōki B-gata

JADE

CORAL

Enigma T

Finland

Hagelin C-36

Romania

Enigma G

Enigma I

Hungary

Enigma I

Slovakia

Enigma I

Bulgaria

Enigma I

Croatia

Enigma K

Spain

Enigma K

Decoded messages in the Finnish national archives

The history of signals intelligence and codebreaking is usually focused on the achievements of the codebreakers of large countries such as the USA, Britain, Germany, Soviet Union etc. However small nations have often managed to achieve great victories in the field of signals intelligence despite being hampered by limited resources.

The Finnish signals intelligence service of WWII was able to solve many foreign cryptosystems including Soviet military and NKVD codes and the diplomatic systems of the United States. Many of these messages can be found in the Finnish national archives. The decoded diplomatic traffic can be found in folders T-21810/4 and T-21810/5.

It is interesting to note that a lot of the traffic from Bern, Switzerland consists of reports on the German military and the war industry. These were probably prepared by the OSS Bern Station and the US military attaché Barnwell R. Legge.

Here are some of these messages:

The codebreakers of the Japanese Foreign Ministry and the compromise of US codes prior to Pearl Harbor

Imperial Japan entered WWII with three separate codebreaking agencies under the control of the Army, Navy and Foreign Ministry. The Army and Navy signal intelligence agencies intercepted foreign radio traffic and decrypted several military and civilian US, UK, Chinese and Soviet cryptosystems. However relations between these two organizations were strained and in many cases they withheld valuable information from each other. Compared to them the decryption department of the Foreign Ministry was much smaller and had access to limited resources, both in terms of manpower and radio equipment.

Information on the decryption department of the Japanese Foreign Ministry is limited since their archives were destroyed twice during the war. First in a bombing on 25 May 1945 and then in August 1945, when they were ordered by their superiors to burn all secret documents.

According to the recently declassified TICOM report DF-169 ‘Cryptanalytic section Japanese Foreign Office’ this department was established in 1923 and by the end of WWII had approximately 14 officials and 16 clerks. The radio intercept unit supplying it with messages had a station in Tokyo equipped with 10 receivers and 19 operators. They usually intercepted 40-60 messages per day with 100 being the maximum.

The emphasis was on the solution of the codes of the United States, Britain, China and France but some German, Turkish, Spanish, Italian, Swiss, Thailand and Portuguese codes were also read. Despite their limited resources it seems that the Foreign Ministry’s codebreakers were able to achieve their goals mainly thanks to compromised material that they received from their Army and Navy counterparts.

 

Overview of exploited foreign codes

British codes

In the case of Britain the Government Telegraph Code, R Code, Interdepartmental Cypher and Cypher M were read.

According to one of the Japanese analysts a 4-figure diplomatic codebook and its substitution tables were received from either the Army or the Navy in January 1940, thus a great deal of the traffic could be read. Even though the substitution tables changed every 4-6 months the Japanese were able to get a copy roughly one month after their introduction.

 

Chinese codes

The Chinese government used several codebooks but only a few were enciphered properly. This allowed the Japanese to solve most of the traffic. One of the codebooks they solved was the ’27 DEMPON’.

 

French codes

Some French codes and their substitution tables were received from the Army and thus it was possible to solve this traffic. These were called ‘PC 149’, ‘PC 150’, ‘PC 151’ and ‘CGX’ by the Japanese and they were used by the French embassies in Tokyo, Peking, Hanoi, Nanking and Chungking.

 

It seems that the numbered codes were used mostly for reports on administrative matters while ‘CGX’ carried important reports on the political and military developments.

German codes

Even though Japan and Germany were allies in WWII it seems that the Japanese authorities did not neglect to solve German diplomatic codes. According to DF-169, p2 a German diplomatic unenciphered code of 100.000 values was solved in part and from 1942 it was possible to read some messages even when they were enciphered with additive sequences, thanks to the reuse of the additive pads.

This must have been the German Foreign Ministry’s basic codebook used unenciphered for low level messages, enciphered with reusable additive pads for important messages and also with one time pads for the most important traffic.

 Swiss codes

The code of the Swiss legation in Tokyo was received from the military in summer 1945 and messages were read till the end of the war.

USA codes

The main target of the Foreign Ministry’s codebreakers were the diplomatic systems of the United States. The State Department used the Gray and Brown codes, the enciphered codebooks A1, B1, C1, D1 and the M-138-A strip cipher. By 1940 the Japanese had managed to get copies of Gray, Brown, A1 and several sets of strips of the M-138-A.

 

With these codes and with the M-138-A strips and keylists the Japanese could read all US diplomatic traffic in the period 1940-41. The importance of this compromise for Japanese foreign policy is something that needs to be investigated by historians.

During the war they received more strips and keylists from their Finnish and German allies.

The Pope’s codes

                                                                                                                          
                                                 The Pope! How many divisions has he got?

                                                                                 Joseph Stalin

 

Although the Pope doesn’t have any divisions he has always been one of the most powerful men on the planet. As leader of the Catholic Church and head of the Vatican State he can wield great influence on world affairs.

With millions of followers all over the globe the Catholic Church has traditionally been well informed of world events. The numerous Catholic churches with their priests, bishops and other officials have always transmitted information back to the Vatican. In order to protect its communications from outsiders the Catholic Church has used various cryptologic systems.

During WWII the communications of the Vatican attracted the attention of numerous codebreaking agencies. Both the Axis and the Allies tried to exploit these messages and they succeeded, in part.

Axis:

German effort:

Three different agencies worked on Vatican codes. The German High Command’s deciphering department – OKW/Chi, the Foreign Ministry’s deciphering deparment Pers Z and the Air Ministry’s Research Department - Reichsluftfahrtministerium Forschungsamt.

The Germans spied on the Catholic Church because they knew that the internal opposition to Hitler and the Polish intelligence service had connections with the Vatican.

Unfortunately the information on their successes and failures versus Vatican systems is limited.

OKW/Chi

European Axis Signal Intelligence in World War II, vol3 says in page 69:

‘Around the beginning of the war, a desk was established for attacks on Vatican traffic. Seifert, a former member of the Austrian Cryptanalytic Bureau, joined OKW/Chi at the time of the Anschluss and broke a Vatican book.’

Pers Z

European Axis Signal Intelligence in World War II, vol6 says in page 33:

‘Vatican

The 1940 Report of the Italian Group (Paschke) made it clear that while approximately 50 per cent of the Vatican traffic could be read, the traffic was not a major Pers Z S commitment. Reference was made to a one part, three-letter code, enciphered by a transposition within the groups, and to a one-part figure code, enciphered by means of substitution alphabets and a sliding strip. Most of the book groups were secured from Goering's "Research" Bureau (FA).’

Forschungsamt

It seems that serious work on Vatican cryptosystems was done at Goering’s Forschungsamt. However the information from TICOM reports on the work and successes of the FA is very limited.

European Axis Signal Intelligence in World War II, vol7 says in page 88:

‘Vatican Code,

In  a captured Pers ZS reconstruction of a Vatican Code Book the signature of a Fraulien Titschak appears with the date of August 1939 and a notation that she had copied out values at that time for the FA (Fraulien Titschak was a member of the Foreign Office Cryptanalytic Bureau). The Annual Report of the Italian Group of Pars ZS for 1940 indicates that while Pers ZS did some work on Vatican systems most or the identifications on Vatican systems were received, from the FA.’

Several reports were written in the postwar period by former workers of the FA but these have not yet been declassified by the NSA.

Italian effort:

The Italian Army’s codebreaking department solved Vatican codes during WWI and in the interwar period. According to David Alvarez’s ‘Left in the Dust: Italian Signals Intelligence, 1915-1943’:

‘Access to Vatican traffic proved a boon to Italian intelligence. Such traffic provided Rome with advance word of papal diplomatic initiatives, such as the pope’s peace proposal of August 1917 and his efforts in 1918 to mobilize Catholic opinion and lobby foreign leaders on behalf of Vatican representation at the peace conference.’

However during WWII the small number of cryptanalysts had too many commitments and it doesn’t seem like they could solve the high level Vatican messages.

Finnish effort:

According to David Kahn’s ‘Finland's Codebreaking in World War II':

‘Among the simplest codes to crack were those of the Vatican. In the 16th century the papal curia led the world in cryptology, and AaIto thought that they had not advanced beyond that level, as described in a couple of studies of nomenclators of that period in a Finnish journal by H. Biaudet in 1910. Vatican codes were attacked by O. Nikulainen because he was the only cryptanalyst who knew Italian. However, the results had little value.’

Allies:

Anglo-American effort:

Information on the efforts of British and US codebreakers versus Vatican codes is available from the article ‘No immunity: Signals intelligence and the European neutrals, 1939-45’.

The British codebreakers solved in 1942-43 parts of the low level code RED, a three-letter code of 12,000 groups enciphered by substitution tables. The information was shared with the US Army’s cryptanalytic agency that assigned a group of codebreakers to tackle Vatican traffic. This section was called ‘Gold’.

Neither the British nor the Americans were able to solve the high level codes used by the Vatican.

According to the article:

‘The cryptanalysts in Gold Section were surprised at the sophistication of Vatican cryptosystems. Explaining their lack of success, they noted that 'The difficulties encountered showed that considerable intelligence was matched against the analysts', and they concluded that they were dealing with 'a cryptographer of no mean ability.' The effort against papal cryptosystems was also undermined by the complete absence of compromised cryptographic materials and the communication discipline of papal diplomats.’

Conclusion:

In the course of WWII the communications of the Vatican attracted the attention of both the Axis and the Allies. Both sides were able to exploit some Vatican cryptosystems but according to the information available, the Pope’s high level codes proved secure.

Perhaps a guardian angel was looking out for the Pope.

Sources: ‘European Axis Signal Intelligence in World War II’ volumes 3,6,7, Intelligence and National Security article: ‘No immunity: Signals intelligence and the European neutrals, 1939-45’, ‘In the Name of Intelligence: Essays in Honor of Walter Pforzheimer’, International Journal of Intelligence and CounterIntelligence article: ‘Left in the Dust: Italian Signals Intelligence, 1915-1943’,

Pic: mapsofworld.com

Greek radio stations 1940

An interesting file can be found in the British archives, folder HW 40/195 ‘Selected correspondence from the archives of OKW/CHI’.

In 1940 the Lauf and Treuenbrietzen stations that intercepted foreign radio traffic for the German High Command’s decryption department - OKW/Chi, were ordered to give special attention to Greek radio traffic.

The report of 19 January 1940 says:

‘Because of the geographical dispersion of the Greek state in a large number of islands separated from each other by long distances there has been for some time an internal Greek wireless traffic, above all between the mainland and individual islands (e.g. Crete) and probably between island and island also.’

Then a list of Greek radio stations follows.

 

German interest in Portuguese cipher machines

The cipher machines of Boris Hagelin were an alternative to the Enigma and in the 1930’s and 1940’s many countries bought them.

In 1944 the Germans had a chance to examine Hagelin machines purchased by Portugal. There were 24 large and 30 small machines being flown from Sweden to Portugal.

These were examined on 11 January 1944 at Tempelhof airport by Dr Erich Huettenhain (chief cryptanalyst of OKW/Chi), Dr Karl Stein (a member of the cipher security department) and Rotscheidt (an engineer in charge of development of cryptanalytic machinery)

 Source: TICOM report D-60 ‘Miscellaneous Papers from a file of RR Dr. Huettenhain of OKW/Chi’, p2-3

More information on the Irish codebreakers

I’ve already given some information on the secretive Irish codebreakers of WWII. Mr David Mee has uploaded a few pages from the book ‘G2, Irish Military Intelligence for the period 1918-45’ by Maurice Walsh.

These mention the arrest of German agents and the examination of their cipher systems. They also reveal cooperation between the Irish unit and Bletchley Park.

There is also a nice picture of dr Richard Hayes, the top cryptanalyst, whom the British called ‘extremely able’.

Wartime exploitation of Turkish codes by Axis and Allied powers

The Republic of Turkey remained neutral during most of WWII, while at the same time maintaining close economic relations with Germany. The Turkish leaders were successful in protecting their country’s territorial integrity through constant negotiations with Germany, Britain and the Soviet Union. They finally joined the Allied cause and declared war on the Axis only in February 1945. 

During the war Turkey, as a neutral power, had a major advantage since it could operate embassies in both Allied and Axis nations. This gave Turkish officials the opportunity to get valuable information from both sides. For this reason Turkish diplomatic communications became a target for Axis and Allied cryptanalysts.

The Turks used mainly 4-figure codebooks (INKILAP, ZAFER, SAKARYA, CANKAYA, INONU, ISMET) enciphered with additive sequences.

Turkish systems were attacked by several German agencies. The diplomatic codes were attacked by the Pers Z, Forschungsamt and OKW/Chi. Military systems by the OKL Chi Stelle, the Army’s Inspectorate 7/VI and OKW/Chi.

Italy, Hungary and Finland also read Turkish traffic with significant success throughout the war.

All the Axis powers took advantage of the fact that some of the Turkish codebooks were simply repaginations of previous versions.

The mysterious Irish codebreakers

A British report investigating the security of US diplomatic codes mentions that the Irish had a codebreaking department and were ‘thoroughly well equipped in the art of code breaking’.

According to another report ‘their head cryptographer is extremely able’.

Who could they be referring to? It seems that the head of the Irish codebreaking department was a mr Richard Hayes.

Swedish Army codes and Aussenstelle Halden

During WWII Sweden was neutral but maintained close economic relations with Germany. The German signal intelligence agencies were interested in Swedish communications and they tried to solve their diplomatic and military systems.

Diplomatic systems

The Swedish diplomatic traffic was mainly enciphered with Hagelin cipher machines. The Germans analyzed the traffic but according to postwar reports could not solve it (although one message of 5.000 words may have been solved).

The Allies also targeted Swedish Hagelin traffic and had some success, mainly through physical compromise, but according to a report dated August 1944 (Fish notes report 102) ‘the keys have not been broken since January 1942 and none of this traffic has been read since June of that year’.

Military systems

The military traffic was intercepted and decoded successfully by a unit in Halden, Norway. This was outstation Halden (Aussenstelle Halden). This unit belonged to Feste 9 (Feste Nachrichten Aufklärungsstelle -Stationary Intercept Company) but was attached to the Halden Police battalion for administrative purposes. It was commanded by Lieutenant Thielcke.

The systems solved by the Germans were:

1). SC2 - Slidex type system, read in May ’43.

2). SC3 - 3-letter field code without reciphering, read in April ’43.

3). SC4 - 3-letter alphabetical code without reciphering, read in June ’43.

4). SRA1 and SRA5 - Grille/Stencil systems. First broken in the spring or summer of ’43.

5). SM-1 (Schwedische Maschine 1) - version of the Hagelin C-38. This was solved on operator mistakes and ‘depths’. Some details are given by Luzius, an expert on Hagelin cipher machines at the German army’s signal intelligence agency:

‘7. He was then asked whether they had achieved any other successes with this type of machine. He recalled that the Hagelin had been used by the Swedes, in a form known as BC-38. This was similar to the M-209, but with the additional security feature that, whereas with the American machine in the zero position A = Z, B = Y, etc., In the Swedish machine the relationship between these alphabets could be changed. He could not remember whether it had changed daily or for each message. He himself had worked on this machine and had solved a few messages. It had been an unimportant sideline, and he could not remember details; he thought that it had been done by the same method, when two messages occurred with the same indicators. This had only happened very rarely.

The report E-Bericht 7/44 of Feste 9 has some information on Swedish systems:

The people of Aussenstelle Halden were not successful with all the Swedish codes. According to ‘European Axis signals intelligence’ vol4 the high level grille HCA and the ‘large’ Hagelin (probably a version of the Hagelin B-211) were not solved.

The solution of the tactical codes and the C-38 allowed the Germans to build up the Swedish army’s OOB. Why were the Germans so interested in the army’s dispositions? It seems that in 1943 they contemplated an attack on Sweden.

Sources: European Axis signals intelligence’ vol4, CSDIC/CMF/Y 40 - 'First Detailed Interrogation Report on Barthel Thomas’, TICOM reports I-55, I-64, I-211, ‘Hitler’s war’, E-Bericht Feste 9 - 7/44

The Irish Government Telegraph Code

In the course of WWII the diplomatic communications of the neutral countries became a target for the codebreakers of the Allied and Axis powers. Although Ireland was a small country the Irish diplomatic codes attracted the attention of the German Foreign Ministry’s Pers Z and Goering’s Forschungsamt. These two organizations were able to read the Irish codes during WWII.

The Republic of Ireland used for its secret diplomatic communications the British Government Telegraph Code, a five-letter, one-part, 84,000 group system. This was used unenciphered for low level messages and enciphered for more important traffic. The Germans had managed to capture a copy of the Government Telegraph Code from the British consulate in Bergen, Norway in 1940.

The section of Pers Z that was responsible for Irish codes was Dr Ursula Hagen’s group. This covered England, Ireland, Spain, Portugal and Latin American countries. Technical Assistant (Wissenschaftliche Hilfsarbeiterin) Dr.  Ursula Hagen was born March 23, 1901. She entered Pers Z S on October 1, 1922 and by 1939 (and through 1945) she was head of the group which was responsible for work on England, Ireland, Spain, Portugal, and Latin American countries. In 1942 her group had 12 people assigned to it (1). 

Irish codes were also worked on by Goering’s Forchungsamt. The Forschungsamt’s Abteilung 7 had considerable success (‘ziemlich laufend’) with Irish codes up to the end of the war (2). Abt. 7 covered: USA, England, Ireland, South America, Spain, Portugal, Turkey, Egypt and Far East. Personnel were roughly 60-70.

More details on the Irish codes are given in TICOM I-172 ‘Interrogations of Hagen and Paschke of Pers Z S’, p3-4

11. Eire

HAGEN described the work done by Pers Z S on Irish Diplomatic substitution recoding tables for use with G.T.C. There were 26 hatted alphabets, each group being taken from one alphabet. The alphabets were not necessarily used in order but always systematically. The last group of a telegram indicated the system to be used in the next message, e.g, if the last group was recyphered with alphabet 5, then this alphabet would also be used for the first group of the next message. The tables changed at irregular intervals - only about four times during the war. Different keys were used for various posts, e.g. Berne, Rome, Berlin, Paris, Madrid. The traffic became more difficult to read in 1942-43, when there was insufficient material and not enough staff. Then the Forschungsamt started work on it and solved the Berlin and Madrid links. Pers Z S took over the keys from the Forschungsamt in 1944. The first three figures of the message gave the page number, the fourth figure the number of the block, and the fifth and sixth figures the line-numbers. This new system used a 300-figure subtractor; each end of the link was allotted 25 such keys, e.g. 25 Dublin-Berlin and 25 Berlin-Dublin, etc. If the length of the message exceeded 300 figures, the key was repeated, but a new key was used for each new message, always in the order 1 to 25.

Messages consisted of reports from the Irish minister on the state of affairs in Germany. The Staatssekretär was interested in diplomatic reports on the trend of events, air-raids; etc. The traffic was regarded as valuable by Ribbentrop and some messages were shown to Hitler. HAGEN said that with any luck six fairly long messages were sufficient to break a new substitution recoding table, and this work took less than a week.

Irish messages in plain G.T.C. did not provide information of any value.

Translated Pers Z reports from 1941 and 1942 confirm these statements (3). The 1941 report says that ‘all the Irish telegrams can be read completely’ and 223 decoded telegrams were published. In 1942 126 decoded telegrams were published.

Some decrypted Irish telegrams from 1944 can be found in the TICOM collection of the German Foreign Ministry’s Political Archive (4), for example:

Notes:

(1). European Axis Signal Intelligence in World War II, vol6

(2). TICOM report I-54 ‘Second interrogation of five members of the RLM/Forschungsamt’, p2-3

(3). British national archives HW 40/180 ‘PERS Z-S, the Diplomatic Decryption Bureau of the German Ministry of Foreign Affairs: reports and POW interrogations’ (Annual report of section dealing with British empire, Eire, Thailand, Portugal, Spain and Latin America).

(4). German Foreign Ministry’s Political Archive - TICOM collection – File Nr. 795 Irland 1944 Entschl. Verkehr (übersetzt) zw. d. versch. Irischen Botschaften