Friday, December 1, 2017

Compromise of State Department communications in WWII

In the course of WWII both the Allies and the Axis powers were able to gain information of great value from reading their enemies secret communications. In Britain the codebreakers of Bletchley Park solved several enemy systems with the most important ones being the German Enigma and Tunny cipher machines and the Italian C-38m. Codebreaking played a role in the Battle of the Atlantic, the North Africa Campaign and the Normandy invasion. 

In the United States the Army and Navy codebreakers solved many Japanese cryptosystems and used this advantage in battle. The great victory at Midway would probably not have been possible if the Americans had not solved the Japanese Navy’s JN25 code.

On the other side of the hill the codebreakers of Germany, JapanItaly and Finland also solved many important enemy cryptosystems both military and diplomatic. The German codebreakers could eavesdrop on the radio-telephone conversations of Franklin Roosevelt and Winston Churchill, they could decode the messages of the British and US Navies during their convoy operations in the Atlantic and together with the Japanese and Finns they could solve State Department messages (both low and high level)  from embassies around the world.

Britain, the Soviet Union and the United States did not have impenetrable codes. In the course of WWII all three suffered setbacks from their compromised communications. One of the worst failures of US crypto security was the extensive compromise of State Department communications in the period 1940-44.

Sunday, November 26, 2017

Progress of my FOIA cases

So far in 2017 my following NSA FOIA cases have been processed:

1). TICOM report DF-229 ‘Three reports on the work of OKW/Chi’:

2). Request for any postwar interrogation reports on Georg Schroeder, head of the Forschungsamt’s cryptanalysis department:

I received a reference to files transferred to NARA in 2016. The NARA research department checked the reference and they could not locate any file on Schroeder.

3). Special Research History SRH-361 ‘History of the Signal Security Agency Volume Two: The General Cryptanalytic Problems’:

4). Request for two Japanese TICOM reports – ‘Report on Saburo Nomura’ and ‘Interrogation of mr Hayashi’:

I copied the first one from NARA. The second has also been sent to NARA but the reference points to 36 boxes that have not been indexed, so the file could not be located by my researcher. 

5). TICOM report I-170 ‘Report on French and Greek Systems by Oberwachtmeister Dr. Otto Karl Winkler of OKH/FNAST 4’:

6). TICOM report I-40:

I requested this file in 2015 and now it has been placed in the review queue.

7). Request for TICOM report DF-196 ‘Report on Russian decryption in the former German Army’ and TICOM document 2765 ‘Die Entwicklung des russ. Geheimschriftenwesens’:

DF-196 has been placed in the review queue. TICOM document 2765 cannot be located. 

However pages 31-37 of that report are available as TICOM DF-94 ‘The development of Russian cryptographic systems’.

8). Reports ‘E-Bericht der NAAst 5’ for second half 1944:

9). Report ‘Polish cipher systems - January 1945’ (S-007.253):

The NSA FOIA office gave me a reference which the NARA research department checked without success.

10). TICOM reports I-26, I-31, I-84, I-116, I-118, I-120, I-137, I-160, I-176, I-181:

11). TICOM report DF-240 ‘Characteristics, analysis and security of cryptographic systems’ and DF-241 ‘The Forschungsamt’:

12). Carlson-Goldsberry report:

It is still in the review queue.

Overall it’s been a very good year so far as I’ve received a lot of material. Let’s hope the rest of the reports are released soon.

Sunday, November 19, 2017

War Over the Steppes - The Air Campaigns on the Eastern Front 1941-45

The war between Nazi German and the Soviet Union was the largest land campaign of WWII and it involved millions of troops and tens of thousands of tanks and warplanes.

In the East the Luftwaffe played a vital role by establishing air superiority, supporting the ground troops at the front, bombing important targets deep behind enemy lines and keeping the enemy under constant observation with its recon planes.

The Red Air force suffered great losses in 1941-42 but in the period 1943-45 it was rebuilt and it managed to play an important role in the actual fighting.

Until recently studies of the air war in the Eastern front were hampered by the lack of adequate sources for both participants. Authors either had to rely on the surviving Luftwaffe records, which meant they would have to use German estimates of Soviet strength and losses instead of the actual data, or they were forced to use the official Soviet post war histories, which downplayed Soviet defeats and exaggerated German strength and losses.

Hooton’s books are different from other similar works due to their emphasis on statistical analysis of the Luftwaffe operations.

His new book ‘War over the Steppes: The air campaigns on the Eastern Front 1941–45’ covers the air war in the Eastern front and the main battles between the Luftwaffe and the Red Air force.

The book has the following chapters:

1. From friends to foes: Russian and German air power 1924 to 1941.

2. Invasion and retreat: June 1941 to April 1942.

3. The tide turns: May 1942 to February 1943.

4. The Russian advance: March 1943 to April 1944.

5. Red Star triumphant: May 1944 to May 1945.

The main strength of the book is the addition of detailed tables on the strength, loss and sortie statistics for both sides. After the fall of the Soviet Union the government archives were opened to researchers and new material on WWII has became widely available. Hooton was able to take this data and incorporate it into his book, thus offering detailed and most of all reliable information for both air forces.  

I consider this book to be on the same level as ‘Stopped at Stalingrad: The Luftwaffe and Hitler's Defeat in the East, 1942-1943’, meaning it is essential reading for anyone interested in military aviation history. 

Sunday, November 12, 2017

British Tank Production and the War Economy, 1934-1945

All the major powers of WWII used tanks and especially in North Africa and in Europe they played an important role in the actual combat operations. Some of these tanks like the German Tiger were famous for their combat record, while others like the Soviet T-34 and American M4 Sherman were produced in huge numbers.

However both during the war and afterwards British tanks were criticized for being inferior. The design and combat performance of British WWII tanks is a subject that has received attention by historians and several authors like Correlli Barnett, David Fletcher and Peter Beale are critical of British tanks.

The new book ‘British Tank Production and the War Economy, 1934-1945’ by Benjamin Coombs covers the administrative and production history of the British tank program in WWII and its greatest strength is that it tries to explain why certain decisions were made and what effects they had regarding production numbers, tank quality and combat performance.

The book has the following chapters:


1. Government and Industry during Disarmament and Rearmament

2. Government and Industry during Wartime

3. General Staff Requirements and Industrial Capabilities

4. The Tank Workforce and Industrial Output

5. Overcoming Production Problems and Delays

6. Influence of North America upon the British Tank Industry


A great review is available at by user ‘VinceReeves’ so I’ll repeat it here:

‘This is a long-needed objective view of British tank production during World War II that finally manages to eschew the hysteria and nonsense that generally attends this subject. Coombs chronicles the evolution of tank design, and the shifting priorities of production with authority and objectivity, and demonstrates how much misunderstanding has attended the controversies over real and perceived quality issues and inefficient tank production. 

Basically, British tank production underwent three stages during the war; an early stage in which tank production was downgraded in favour of more vital air defence work, a second stage in which quality was sacrificed to boost quantity production to rectify numerical deficiencies, and finally a mature third stage in which quality was emphasised, and British tanks became more effective and reliable.

Coombs makes sense of what appear to be irrational decisions to continue the manufacture of obsolete tanks long after they were required - more often than not this was undertaken to keep production facilities and skilled labour within the tank programme so that they would be available when newer tanks were ready for introduction.’

If you are interested in military history and you want to learn more about the British tank program then this book is a valuable resource.

For me the value of the book is that it helps explain German victories in N.Africa in 1941-42. The Germans benefited by fighting against an opponent whose tanks constantly broke down. In the period 1943-45 the British tanks became more reliable because a determined effort was made to thoroughly check and fix flaws and a high priority was assigned to spare parts production.

Thursday, November 9, 2017

Waiting for the Carlson-Goldsberry report...

I have one more essay that I’m going to upload and it covers, in some detail, the compromise of State Department communications in WWII.

Ideally I would like to get a copy of the Carlson-Goldsberry report from the NSA’s FOIA office but if that doesn’t happen soon I’ll just go ahead and post it anyway. If I need to update it I’ll do so in 2018.

Let’s hope I get lucky and the file is released soon.

Thursday, November 2, 2017

The code of mr Seymour Parker Gilbert - Agent General for Reparations to Germany

After the Allied victory in WWI, the leaders of the US, UK and France imposed harsh peace terms on the defeated Germans. Germany (and the other defeated Central Powers) had to make reparations to the Allied countries.

The problem was that the payments that the German government was supposed to make were so great that they would bankrupt the country. Due to German unwillingness and inability to service the payments the Allies resorted to military measures such as the occupation in 1923 of the Ruhr industrial area.

In order to defuse the situation and find a realistic solution to the reparations problem the Dawes Plan was implemented. Allied troops would leave the Ruhr area and the German government would resume payments, after receiving a US loan that would revitalize the German economy.

In Germany the Allied representative responsible for monitoring the German compliance with the Dawes plan was mr Seymour Parker Gilbert and his official title was Agent General for Reparations by the Allied Reparations Commission.

It seems that the German government closely monitored Gilbert’s communications and was able to solve some of his encrypted traffic to New York (Federal Reserve bank), Paris and Rome.

Documents of the German Foreign Ministry’s decryption department Pers Z, captured at the end of WWII, show that his messages were solved by the German codebreakers:

Source: TICOM report DF-15 ‘Reports of Group A’ (US National archives - RG 457)

Additional information: Gilbert’s 1927 report.

Monday, October 30, 2017

WWII documentary

Interesting newfound footage from WWII. Hitler’s mental and physical deterioration can be clearly seen in this documentary.

Friday, October 27, 2017

The reconstructed Slidex card

At Crypto museum I saw that they’ve uploaded some Slidex cards from 1944. I had a quick look to see if I could locate the one solved by the German codebreakers and found in the report E-Bericht FNASt 9 (US National archives - RG 457 - Entry 9032 - box 22 ‘German deciphering reports’).

I didn’t expect to find anything so imagine my surprise when I saw that the Air Support Signals Unit card No. 1 (from 1944) had the same code values:

I’ve added this card in The Slidex code.

Tuesday, October 24, 2017

Signals intelligence and codebreaking operations during the Greek-Italian War of 1940-41

At the start of WWII the Kingdom of Greece, ruled by Ioannis Metaxas  (head of the 4th of August Regime) followed a neutral foreign policy and tried to avoid taking part in the conflict. However constant Italian harassment and provocations (such as the sinking of the cruiser Elli) and the transfer of Italian army units to Albania made it clear that war could not be avoided for long.

In October 1940 Italian forces invaded Greece, in the area of Epirus, and the Greek-Italian war started. The Greek forces were able to contain the assault and the Greek counterattack forced the Italians back into Albanian territory. After the defeat of a major Italian offensive in spring 1941 the front stabilized inside Albania.

At the time Britain was overextended with obligations in Europe, Middle East and Asia. However the British armed forces made a small contribution with an RAF expeditionary corps. When more British forces started to arrive in March 1941, their involvement gave Germany an excuse to become involved in the conflict.

German forces invaded Greece in April 1941 and made rapid progress due to the fact that almost the entire Greek Army was fighting in the Epirus area. The remaining units and the small British forces transferred to Greece in March-April 1941 were unable to stop them. 

Then in May 1941 the Germans were also able to defeat the Greek and British forces that had retreated to the strategic island of Crete.

What role did signals intelligence and codebreaking play during that short conflict? Let’s have a look at the limited information available:

The Italian effort

Italy had two codebreaking departments, one under Army and the other under Navy control.

The Italian army’s intelligence agency SIM (Servizio Informazioni Militari) had a cryptanalytic department that attacked foreign crypto-systems. This section was headed by General Vittorio Gamba and was located in Rome. Personnel strength was roughly 50 people (half cryptanalysts-half linguists and clerks).

The naval intelligence agency SIS (Servizio informazioni Speciali della Royal Marina) was divided into 4 branches. Branch B (Beta) was tasked with signals intelligence. It was subdivided into cryptanalysis, interception and direction finding, security and clandestine radio intercepts. The cryptanalytic department was located in Rome and headed by Commander Mario De Monte.

It is not clear if the Italians had success with Greek Army or Air force codes and ciphers. However in the Archivio dell' Ufficio Storico della Marina Militare there are decoded Greek Navy messages.

Regarding the Greek Air force communications, it seems that the cipher system used was simple transposition (1). Considering the limited security of this system it is reasonable to assume that it was solved by the Italian codebreakers.

The Greek effort

At this time there is almost no information available on the Greek Army’s cryptologic and cryptanalytic effort during WWII. A report from 1938 (2) mentions the Greek Army codebooks: small unit code 1937, large unit code 1937, small unit code 1938, mobilization code 1937, cryptographic lexicon 1935.

Regarding cryptanalysis it seems that the Greek Army Signal Corps may have been able to exploit Italian communications (3). According to an article on Greek military intelligence this information comes from British liaison signal officers:

In addition, according to British liaison signals officers, Greek Signals Corps managed to decipher some Italian traffic during the November/December battles in Albania. On 6 December, a British lieutenant-colonel informed his superiors: “Herewith a batch of Italian traffic intercepted by the Greek General Staff. Also, one copy of cipher ‘O.M.’ for internal use of the Italian Army in Albania.” On 8 December, the reply confirmed Greek success: “Many thanks to Greeks for citrario O.M. Tell them I do not remember having seen it but I am very grateful for it and for any further documents of this nature which may be of assistance in reading Italian codes in Albania which I am afraid are not readable.” We could imagine that Greek Signals Corps may have deciphered key traffic during October, prior to the invasion. Unfortunately, at the Army History Service no files of Greek signals operations can be found. Perhaps some material might be held at the Military Archives Service but we must bear in mind that the 1941 German invasion and the 1941-1944 occupation caused the destruction of many files of sensitive army archives. As to Metaxas, he did not make any reference to signals intelligence in his diary’.

The German effort

The German Army’s signal intelligence agency solved Greek Army and Air force ciphers. According to the TICOM report I-170 in spring 1941 Greek AF single transposition messages were solved and translated (4):

My first employment was on the breaking and translating of Greek Air Force messages in Spring 1941. The unit was in BUCHAREST at that time and later it was at BANJA KOSTENIC in Bulgaria. C.O. was Hptm. SCHMIDT, head of the cryptography and translation department from then until Autumn 1944 was Prof. Alfred KNESCHKE, a Professor of Mathematics from Saxony.

The Greek Air Force messages were a matter of simple boxes, the text being sent in T/L groups. The indicator took the form of 3 letters which were always in a given position, the first three T/L groups and had to be knocked out before entering the cipher text in the clear box. This was broken by writing out the cipher text in vertical strips of varying depth and sliding them against each other until a few Greek syllables appeared above one another. After the initial break it became clear that a large part of the messages began with the words ‘parakalw', 'anaferw’ and ‘apesteilamen’ and that the width of the box was as a rule between 15 and 22 columns. On the basis of the above, initial words, all messages were tried out on the normal number of columns and nearly everything was read. I had less to do with the actual evaluation, firstly because the two departments were kept separate and secondly because we were kept fully occupied with our own job. In any case the content of the messages was usually of insignificant strategic value, although the continuous check on officer personalities, deliveries of stores and knowledge of airfields combined with D/F bearings indirectly contributed to considerable tactical results'.

Regarding Greek Army ciphers there is some information available from the postwar interrogations of Army cryptanalyst dr Buggisch. According to TICOM report I-58, in early 1941 he investigated a Greek codebook enciphered with a 35 figure repeating additive sequence (5). Progress was made in the solution of the cipher but the campaign ended just as the system was starting to be exploited operationally:

c. Greek - In early 1941, B. solved a 5-letter code with a 7-cyclic recipherment (period of 35). Just getting to operational speed when the campaign ended.

German exploitation of Italian communications

It seems that the codebreakers of the German Army did not only monitor the communications of their enemies but also solved the codes and ciphers of their Italian allies.

The War Diary of Inspectorate 7/VI shows that Italian codes and ciphers were worked on by Referat 4 (6). According to the reports of Referat 4 for early 1941, 5-figure and 3-figure codes were worked on:

The 3-figure Army code was successfully solved and read. A 5-figure Air Force code was also worked on and the encipherment solved. A 5-figure enciphered code used by the higher command in Albania was worked on and code groups recovered.

The reports say that emphasis was put on the analysis of the systems used by the higher echelons of command.

Some interesting statements regarding Italian radio communications are made in ‘War Secrets in the Ether’ - vol 3, p25 written by Wilhelm Flicke (he was in charge of the OKW/Chi’s Lauf intercept station):

‘Mussolini had decided on war in the Balkans. Von Papen's warnings made Hitler averse to any immediate action there, but he was only able to restrain Mussolini to the extent of limiting Italy to war with Greece. In less than two months the Italians, who had the advantage in everything save morale, were badly beaten. The political leaders were terribly surprised and the Chief of General Staff, Marshal Badoglio, and numerous other high officers were relieved of their duties. This did not help matters.

One of the most decisive factors during those weeks was the manner in which the Italians employed radio. The set-up was the same as that used in maneuvers of previous years. They employed open circular traffic; that is, they used one uniform frequency for a group of stations belonging to the same unit (e.g., the stations of three infantry regiments of a division for traffic with one another and with the divisional station) and each station used only one call sign for all its traffic. The call sign was supposed to change daily but was often used for several days; not infrequently a change in call sign was followed by errors which betrayed the change. Traffic was so heavy that the enemy always had a chance to take bearings and fix locations. Frequently messages were sent in clear. Several units of the Italian Eleventh Army distinguished themselves in this respect. Moreover, the Greeks had obtained at least two Italian army cryptographic systems, how I do not know, but it is certain that in the very first days of the campaign they could decipher a large part of the Italian messages. This enabled them to learn promptly most of the dispositions of the Italian command and to take appropriate action. The superiority thus gained was utilized cleverly and a series of military actions took place which heretofore would never have been deemed possible’.


(2). German Foreign Ministry’s Political archive - TICOM collection - file Nr. 3.676 - Griechenland 1940 - Korresp. betr. Neue milit. Schlüssel u. Vernichtung alter.

(3). Journal of Intelligence History: ‘Greek Military Intelligence and the Italian Threat, 1934–1940

(6). Kriegstagebuch Inspectorate 7/VI - German Foreign Ministry’s Political Archive - TICOM collection – files Nr 2.755-2.757

Acknowledgments: I have to thank Enrico Cernuschi for sharing the messages from the Archivio dell' Ufficio Storico della Marina Militare.

Monday, October 23, 2017


In Decoding Prime Minister Chamberlain’s messages I’ve added the following:

A clue regarding the cipher system used is available from the TICOM report DF-241 ‘The Forschungsamt - Part IV’, p40

Of the numerous examples which might be adduced, the following may serve as an example: The additive number used by Great Britain, which ran to 40,000 elements and served for the encipherment of the 5-digit code and was replaced at definite intervals of time, offered as a rule adequate assurance of security. But if in periods of greatly increased diplomatic activity with telegraphic traffic many times the usual volume the additive is not replaced correspondingly sooner, especially since increased security is desirable in such periods, then this is a sign of deficient control’.

Thus it is possible that the German codebreakers were able to solve the British Foreign Office cipher in the 1930’s.

The official history ‘British Intelligence in the Second World War’ - vol2, p642 says that:


1. Main Cypher Books

Despite an extensive attack in 1938 and 1939, the Germans failed to break the long subtractor system used to re-cypher the Foreign Office's basic cypher books. Against similar tables that were in force from November 1940 to January 1941 they had some limited success, but not enough to enable them to reconstruct the book before both the basic book and the tables were again changed. There is no evidence of later success, and according to German testimony after the war the main Foreign Office systems were never broken’.

However in the notes it also says:

The discovery after the war in the archives of the German Ministry of Foreign Affairs of  a 90-page volume of British diplomatic signals for the immediately pre-war period led to a  Foreign Office enquiry in 1968. This established that a number of the signals had been dispatched en clair. It also noted that there was reliable evidence that the Italians had obtained temporary possession of the cyphers of the Rome Embassy in 1935, and had photographed them, and that they had had fairly regular access to the cyphers at the Mission to the Holy See during the war, so that they might have read all telegrams to Rome up to the outbreak of war and telegrams to and from the Mission to the Holy See from the outbreak of war to the autumn of 1943. After the war the cryptanalysts of the German Foreign Ministry asserted that they obtained no information about British cyphers from the Italians’.

The British statements may have been accurate about the work of the decryption department of the German Foreign Ministry but they do not mention the Forschungsamt effort…

Sunday, October 8, 2017

2017 Cryptologic History Symposium

The NSA’s Center for Cryptologic History and the National Cryptologic Museum Foundation are co-sponsoring the 2017 Cryptologic History Symposium:

19 - 20 October, 2017, Johns Hopkins Applied Physics Laboratory Kossiakoff Center, Laurel, Maryland

The theme for the 2017 Symposium is "Milestones, Memories, and Momentum." There are many milestones to mark in 2017: the 160th anniversary of the first attempt to span the Atlantic with a telegraph cable, 100 years since both the entry of the United States into World War I and the Russian October Revolution, and 75 years after the World War II battles of Coral Sea and Midway. The Symposium will take place just a few months before the 50th anniversary of the Tet Offensive in Vietnam, and during the 25th year after the fall of the Soviet Union and the end of the Cold War. These milestone events and advances in cryptology, as well as how we remember their significance, provide momentum to create the systems of today and the future.

Saturday, October 7, 2017

The Communist agents cipher solved by the Forschungsamt

In the recently released TICOM report DF-240 ‘Characteristics, Analysis and security of cryptographic systems’ there is a short description of a cryptosystem used by communist agents:

It is interesting that the names mentioned in the example are Harri Meier, Theodor Felder, Albert Schwarz, Max Hamburger and Karl Gutmann. 

Wednesday, October 4, 2017


1). In Soviet cipher teleprinters of WWII, I’ve added the following:

More details about the Forschungsamt solution of the Soviet cipher teleprinter are given by Bruno Kröger in TICOM reports DF-240 and DF-241. Kröger was the FA’s cipher machine expert and during the war he solved not only the Soviet machine but also the Swiss diplomatic Enigma K.

The Soviet cipher teleprinter was used on 2-channel networks and the FA’s Technical Division was able to build equipment that automatically intercepted and printed this radio traffic. The cipher text was then examined by Kröger’s department and it was discovered that during transmission pauses the Russian letter П was enciphered seven times in succession. Messages interrupted by transmission pauses were examined and their first and last seven characters analyzed in order to uncover the operating principles of the device.

Through this cryptanalytic procedure it was possible to find out that the machine had 6 wheels that stepped regularly, then their pin arrangement was identified and with the daily key recovered all the day’s traffic could be solved.

This success however turned out to be short lived since in late 1943 the Soviet cipher machine was modified and no pure ‘key’ was transmitted during transmission pauses. It seems that from then on this traffic was only examined by the Army’s Inspectorate 7/VI.

From TICOM DF-240 ‘Characteristics, Analysis and security of cryptographic systems’ - Parts III and IV, p37-39

Both texts indicated the pauses in transmission by - - - - - etc.  The cipher tape has the peculiarity that in passing from the preliminary call-up to the transmission pause, the Russian letter Π, represented in the radio alphabet by + + + + +, occurs seven times.
Now since it was natural to assume that in this transition to and from cipher texts the same letter Π= + + + + + likewise appeared seven times in each case but vas no longer recognizable due to the encipherment the first and last seven cipher values of all cipher texts interrupted by transmission pauses were subjected to special study. Since the machine, once the daily key had been set up, was used very frequently during the course of the day for sending cipher text with numerous pauses in transmission without any new daily key being set up, rather numerous fragments of a length of seven letters were available at known intervals of greater or lesser lengths.
From this it could be concluded that the first seven and the last seven letters of each secret text came from enciphering the letter Π= + + + + + seven times and hence these fragments of cipher text represented pure key text. The following study of these fragments of pure key text led to a recognition of the fact that the first impulses show the same repeated picture in the chain of plus and minus impulses at an interval of 37, the second impulses at an interval of 39, the third impulses at an interval of 41, the fourth and fifth at an interval of 43 and 45 respectively (the intervals may have been 35, 37, 39, 41, 43). This showed the length of the five cipher wheels and their cam pattern according to the day’s setting. Each cam crest caused the inversion of the plain impulse into its opposite while a cam trough left a plain impulse unchanged. The wheels regularly moved one step after each cipher letter.

With this the decipherment of the cipher text had been accomplished. The reconstruction of the cam pattern of the wheels, which was set up new each day, was easily accomplished.

From TICOM DF-241 ‘The Forschungsamt’- Part I, p25

18. The Russian radio [2-channel] cipher machine with a channel for plain text and a channel for cipher text could be studied after the Technical Division had constructed a receiving device which at the same time removed the scrambling. The five elements of the radio alphabet [bands] ware enciphered singly through five wheels which move evenly. The wheels could be set up new each day corresponding to the daily key; but the period was constant and invariable. It was possible to solve this completely.

From TICOM DF-241 ‘The Forschungsamt’- Part IV, p38

It need only be mentioned here that the 2-channel cipher machine was withdrawn from use a few days after the Forschungsamt succeeded in solving it. When the machine was put into use again some weeks later, the cipher device of the cipher channel had been so altered that solution by the previous method was no longer possible since, when switching the machine from procedure traffic to cipher text and between a pause in transmission and cipher text, the switching became effective at once and the idling period of 7 elements had dropped out. That the same machine was involved was proven only by the receiver device which still broke up the scrambled text into a clear and a cipher text in the same manner as before. Because OKH had great interest in this traffic and its own receivers did not work perfectly, and because further detailed work at this time (Autumn 1943) in the Forschungsamt was not possible, OKH received all new traffic on this machine for processing. 

2). In Compromise of Soviet codes in WWII, I’ve added information from various reports including TICOM sources and FMS P-038 ‘German radio intelligence’.

Sunday, October 1, 2017

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).

Wednesday, September 27, 2017


The NSA FOIA office has released the TICOM report DF-240 ‘Characteristics, Analysis and security of cryptographic systems’. Google drive link.

Contents of the file:

240 A - Table of contents

240 B - Analysis of Enigma cipher machine type K

240 Part 1 - Treatise on cryptography

240 Part 2 - Treatise on cryptography

240 Part 3 and 4 - Treatise on cryptography


Friday, September 1, 2017


In The Japanese FUJI diplomatic cipher 1941-43 I’ve added the following:

1). In ‘Allied exploitation of the improved J series codes’:

When the new J-19 system was introduced the US codebreakers were already familiar with the basic characteristics of the cipher and Rowlett quickly made important discoveries regarding the underlying code. However solution of the daily key settings was a difficult problem, especially since more resources were put into the solution of the traffic sent on the PURPLE cipher machine.

2). In ‘Australian effort’:

Progress in 1941 was slow and up to February 1942 the only keys solved were those for messages whose content was known (for example messages reporting the departure of ships). However in 1942 things progressed rapidly.

In March ‘42 a member of the British Foreign Office from Singapore who possessed an excellent knowledge of Japanese joined the section. At the same time personnel of the unit developed elaborate cryptanalytic methods for recovering the daily settings and by May ‘42 the section was able to read virtually all FUJI traffic and ‘all bigrams, except those of very rare occurrence, and most tetragrams had been recovered’.

3). In ‘OKW/Chi effort’:

The OKW/Chi designation for FUJI was system J-13/J2B4BCüRuW (Japanese 2-letter and 4-letter code with stencil and transposition – Raster und Würfel). FUJI messages were first solved thanks to a repeat message sent from Paris to Tokyo. The first message and the repeat had the same plaintext (with small variations) and they had both been enciphered with the same key. This mistake facilitated their solution and the basic characteristics of the system were identified.

The solution of the daily transposition settings and the different stencils was taken over by personnel of the mathematical research department, specifically by the mathematician dr Werner Weber.

According to Part 3 of the report I-181 ‘Homework by Dr Werner Weber of OKW/Chi’, Weber started working on Japanese diplomatic messages in July ’41 and he identified the system as a transposed code. The underlying code for some of the messages was the previously solved LA code, thus they could be read. The rest of the messages had a new code.

Solution of the new system and recovery of the code proceeded slowly in 1941. In September ’41 Weber was allocated a small staff to help him with the Japanese traffic and by February ’42 some material could be read. During the year the new system was solved and most of the circular and European/Middle East traffic could be read. In the period summer ’42 to summer ’43 the previous year’s indicators were reused and the old transposition keys and stencils were either repeated or were modified in a predictable manner (with some exceptions).