Information on the German Lorenz SZ42 cipher teleprinter

Frode Weierud has created a webpage with links to original German documents on the Lorenz SZ42 cipher teleprinter, used by the German military in WWII.

The ciphers of Czechoslovakia’s government in exile

At the end of the First World War the multiethnic Austro-Hungarian Empire collapsed and out of its ruins emerged several new countries. One of these was Czechoslovakia, containing the Czech areas of Bohemia and Moravia together with Slovakia and Carpathian Ruthenia in the east.

In the interwar period Czechoslovakia followed a foreign policy supportive of France and was part of the Little Entente. The country had a stable democracy and its industrial resources were large (based on the Skoda works) for such a small country. However there were two important problems affecting Czech national security. On the one hand the rise of Nazi Germany and its rearmament was a clear security threat. At the same time there were serious problems with the German and Slovak minorities that resented Czech rule.

Czechoslovakia contained a large number of minorities that were dissatisfied with the ruling Czech establishment. Especially the German minority made up roughly 23% of the population (according to the 1921 census) and a large part of it was concentrated in the border with Germany called Sudetenland. Many of the Sudeten Germans wanted for their areas to be unified with Germany and in the 1930’s Hitler’s Germany supported the demands of the Sudeten German Party. These claims were rejected by the Czech government of Edvard Beneš and as the Czech crisis threatened Europe with a new war a conference took place in Munich between the governments of Germany, Italy, Britain and France.  

Without support from Britain and France the Czech government was forced to cede the Sudeten territories to Germany and also lost other disputed areas to Hungary and Poland. Even though Germany had succeeded in absorbing the Sudeten areas and in weakening Czechoslovakia that did not stop Hitler’s offensive plans and in March 1939 German troops invaded and occupied the rest of the country. From then on the country was ruled by Germany and special attention was given to its heavy industry which produced weapons for the German armed forces.

During the war the Czechoslovak Government in Exile, headed by Beneš, was based in London and had regular communications with the Czech resistance and with its diplomatic missions and intelligence service stations abroad. In order to protect these communications several cryptosystems were used by the Czech crypto department.

Information on these systems is available from books and articles written recently:

1). The books Odhalena tajemstvi šifrovacich kličů minulosti, Gentlemani (ne)čtou cizi dopisy and Válka šifer. Výhry a prohry československé vojenské rozvědky (1939-1945) by Jiri Janecek have descriptions of the ciphers and the author’s conclusion was that the security afforded by these systems was limited.

2). A series of articles written for ‘Crypto World’ by Jozef Kollár describe each cipher system, explain how to encipher and decipher and also evaluate their security. The articles are:

Cipher ‘TTS’ (double transposition of the text followed by letter to figure substitution)

Cipher ’Rimska dva’ (letter to figure substitution followed by double transposition of the digits)

Cipher ‘Rimska osem’ (homophonic letter to figure substitution followed by encipherment with repeating 10-figure additive sequence)

Cipher ‘Rimska devat’ (letter to figure substitution followed by additive encipherment, repeating additive created from a passphrase)

Cipher ‘Rimska desat’ (letter to figure substitution followed by transposition then additive encipherment, repeating additive created from a passphrase, passphrase is also used to limit the cells of the transposition table)

Cipher ‘Rimska trinast’ (transposition of the text followed by polyalphabetic substitution)

Cipher ‘Eva’ (transposition of the text using a pyramid shaped transposition table)

Cipher ‘Marta’ (letter to figure substitution followed by additive encipherment, additive created via passphrase autoclave procedure)

Cipher ‘Ruzena’ (letter to figure substitution followed by additive encipherment, additive created via passphrase procedure)

Cipher ‘Utility’ (letter to figure substitution followed by transposition)

Cipher ‘Palacky’ (letter to figure substitution followed by additive encipherment, additive created via passphrase procedure, cipher digits multiplied by a constant)

Compromise of Czech ciphers

The Czech resistance movement and the Czech intelligence service caused serious problems for the German authorities with their most audacious operation being the assassination of Reinhard Heydrich, protector of Bohemia and Moravia and former head of the Reich Main Security Office. However after this episode the Germans took many security measures and were generally able to keep the resistance activities under control. Keeping the Czech areas pacified was particularly important since Czechoslovakia had a developed heavy industry sector which produced weapons for the German armed forces.

In their counterintelligence operations the Germans benefitted from having the ability to read a substantial amount of the traffic exchanged between the Czech IS in Britain and the Czech resistance in the occupied territories. This case has been covered in detail in Svetova Revoluce and the codes of the Czechoslovak resistance.

Report on the compromise of the communications of the government in exile

After the end of WWII it seems that the Czechoslovak authorities learned from POW interrogations about the compromise of their ciphers. Karol Cigáň, who worked in the Defense Ministry’s cipher department, summarized some of this information in a report written in 1989.

The report ‘Dopady lúštenia šifrovacieho systému čs. londýnskeho MNO z rokov 1940-1945 na domáci odboj’, can be found in the archive of the Museum of the Slovak National Uprising in Banská Bystrica and in the Central Military Archive at Prague.

In the report Cigan analyzed the Czechoslovak STP cipher and found it insecure. In addition he proved the compromise of Czechoslovak ciphers by examining reports from the office of the high ranking SS official Karl Hermann Frank.

A report from November 1944 had a summary of Funkwabwehr (Radio Defense) operations and it said that during the previous month 8 radio links, whose cipher procedures could be solved, were kept under observation. Of special interest was traffic between the Protectorate and London regarding the preparations for the uprising.

In the month of October a total of 488 messages were solved and 8 cipher keys derived for the STP cipher.

In pages 37-41 Cigan directly compared the Funkawbehr decodes with some of the Czechoslovak telegrams found in the country’s national archives.

For example messages exchanged between the Minister of National Defense General Ingr and Ján Golian and Jaroslav Krátký in the Protectorate and with Heliodor Píka in Moscow. 

The author’s conclusion was that the use of insecure ciphers during wartime played an important role in undermining the operations of the Czechoslovak resistance movement and these events should be acknowledged by the country’s historians. 

Acknowledgments: I have to thank Jozef Krajcovic for his help in locating the report ‘Dopady lúštenia šifrovacieho systému čs. londýnskeho MNO z rokov 1940-1945 na domáci odboj’ and Štefan Porubský for informing me of the articles from Crypto World. 

Crypto World articles on the ciphers of Czechoslovakia’s government in exile

Information on Czechoslovak ciphers of WWII is available from a series of articles written for crypto world. Jozef Krajcovic has added links to these articles at katkryptolog.

These were hand systems using mostly letter to figure substitution and transposition. 

The value of teamwork

Recently I mentioned that I’ve been trying to locate the report ‘Dopady lúštenia šifrovacieho systému čs. londýnskeho MNO z rokov 1940-1945 na domáci odboj’.

After contacting the Czech Defense Ministry’s history department I was told that they could not find it. I thought this was the end of that story but it seems I was wrong!

Thanks to two friends from abroad I’ve not only managed to learn where the report is kept but I’ve also found details about the ciphers used by the Czechoslovak Government in Exile.

If all goes well this information will be presented during the month. 

Update

I’ve added links to Crypto World and janeckovokrypto.

Overview of reports on compromise of Allied communications in WWII

When researching WWII signals intelligence and codebreaking operations it is important to track down all the available sources of information, from POW interrogations and captured documents to detailed reports summarizing Allied cipher policy, decisions and compromises.

It is reasonable to assume that in the postwar era all the Allied countries tried to assess the extent of the compromise of their communications during WWII. Thus I’ve tried to track down these reports. In the following space i’m going to list the reports I know of and give a short summary of each one. I’ve used most of them in my essays but there are some that I haven’t been able to locate (yet).

USA

Military cryptosystems

1). The ‘European Axis Signal Intelligence in World War II’ volumes are available from the NSA’s website. They are dated May 1946 and have a lot of information on German cipher machines, the German codebreaking agencies and their major achievements. Unfortunately I don’t think that the EASI volumes are entirely accurate.

2). The report Special conference on M-209 security is dated 1950 and looks into the German exploitation of the US M-209 cipher machine. It is difficult to explain why the people involved looked only at the available TICOM reports and not the actual files of the German Army’s codebreaking agency Inspectorate 7/VI. These had been retrieved in 1947 from a camp in Austria.

Overall it seems to me that US reports are not as thorough as they should be.

State Department

I am not aware of any State Department communications security report written after the end of WWII. The ones available were produced during the war and submitted to the US Joint Chiefs of Staff.

1). The reports of June 1941 and November/December 1943 are available online via the NSA’s Friedman collection.

2). The report of June 1944 can be found in the US National Archives and Records Administration - collection RG 457- Entry 9032- box 1384 - 'JCS Ad hoc committee report on cryptographic security of government communications'.

The problem is that these reports only have theoretical evaluations of the State Department cryptosystems, not information on their compromise by the Axis powers.

OSS

The Office of Strategic Services was the predecessor of the CIA and during WWII its overseas stations gathered military and political intelligence on the Axis powers. For example in Bern, Switzerland the local OSS station (headed by Allen Dulles) kept in contact with members of the German Resistance.

According to an OSS veteran a report on WWII crypto security was prepared but I don’t have any details.

Soviet Union

Both in the Soviet era and today in modern Russia the files and archives of the signal intelligence organizations remain closed to researchers. This makes it very difficult to find information on Soviet cryptosystems and on whether the Soviet authorities evaluated their communications security during WWII.

According to Anatoly Klepov's “The historical truth” of Beria and Suvorov about cryptography and radio intelligence, there were evaluations of Soviet cryptosecurity in 1941, in 1943 and at the end of WWII. These investigations came to the conclusion that Soviet ciphers had not been compromised by the Germans but that they were theoretically solvable. This led to the introduction of new, more secure systems.

UK

Army

There are files dealing with British Army communications at the National Archives, collections WO 219 and WO 193. However these deal with cipher policy, not cipher compromises.

Navy

The report ADM 1/27186 ‘Review of security of naval codes and cyphers 1939-1945’ is available from my Google docs and Scribd folders. It is dated November 1945 and it was written after examining the files of the German Navy’s codebreaking agency B-Dienst. Thus it has an excellent analysis both of Royal Navy cipher policy and the compromise of RN codes and ciphers.

RAF

The report AIR 20/1531 ’R.A.F. signal communications: security’ can be found in the National Archives but the information on the compromise of RAF systems is only based on decrypted German messages, not other sources.

SOE

The Special Operations Executive was an intelligence organization created during WWII. I don’t know if a report on the compromise of SOE codes was ever prepared. The British authorities certainly had the available information, since they captured the War Diary of Inspectorate 7/VI in 1947 and this included the summary reports of Referat 12 which dealt with Allied agents’ codes.

The report HS 7/41 ‘Section II: field cyphers; appendices L, M, N and O’ has a file titled S.O.E. FIELD CIPHERS which is available from the Arcre website. This file points out theoretical and practical problems with SOE cipher security but does not have information on the compromise of said systems by enemy codebreakers. 

France

French military high level codes were solved by the Germans in the 1930’s and up to the Battle of France. Unfortunately I am not aware of any French report summarizing their cryptosystems and their compromise during the war.

Czech Republic

During WWII the communications of the Czech resistance movement were solved by the Germans. It seems that at the end of the war the Czechoslovak government found out about this case and personnel of the Defense Ministry prepared the report ‘Dopady lúštenia šifrovacieho systému čs. londýnskeho MNO z rokov 1940-1945 na domáci odboj’.

I requested this report from the Czech Defense Ministry’s history department but they were not able to locate it. Let’s hope that some Czech researcher will be able to find it.

Poland

Polish military, diplomatic, resistance movement and intelligence service codes were read by the Germans during WWII. I don’t know if there are detailed reports in the Polish government archives but the following sources have valuable information.

1). The Cryptologia article ‘From the Archives: Polish Interwar MFA's Cipher Compromised?’ by Jan Bury presents two reports written in 1940 and 1947 by the intelligence officer Major Tadeusz Szumowski, concerning the security of the Polish diplomatic Code 45.  According to Szumowski this codebook had been compromised and the Germans could read the Polish diplomatic traffic since the leadership of the Polish Foreign Ministry chose to keep using it despite his warnings. Szumowski was correct about this case.

2). Recently the book KODY WOJNY. Niemiecki wywiad elektroniczny w latach 1907–1945 a losy polskich, sowieckich, alianckich kodów i szyfrów has been published by Marian Zacharski. I don’t know if the author has information on the Polish ciphers from Polish sources but he has uncovered material from the recently released TICOM files on the extensive compromise of Polish cryptosystems during the war.

Conclusion

Compromises of communications security are usually difficult to acknowledge by the countries that suffer them. For example since the 1970’s countless books have been written about the successes of Bletchley Park, yet detailed information on the Axis solution of Allied codes only started to become available in the 2000’s when TICOM reports and other relevant documents were released to the public archives by the US and UK authorities.

I’ve listed some reports that deal with the compromise of Allied codes but I hope that researchers will be able to locate more. Specifically:

1). State Department postwar reports on WWII compromises (especially the M-138-A strip cipher case)

2). The OSS report on WWII cryptosecurity.

3). The Soviet reports of 1941, 1943 and postwar period.

4). Reports similar to ADM 1/27186 for the British Army, RAF and SOE.

5). French reports on their WWII cryptosystems.

6). The Czech report ‘Dopady lúštenia šifrovacieho systému čs. londýnskeho MNO z rokov 1940-1945 na domáci odboj’.

7). Polish government-in-exile reports on their codes and ciphers. 

Did the German codebreakers solve the Japanese Purple cipher machine? – Information from mr Otto Leiberich

In the late 1930’s the Japanese Foreign Ministry distributed the Purple cipher machine to its most important embassies and it was used to encipher high level messages to and from Tokyo. Unfortunately for the Japanese the introduction of this new cipher machine wasn’t able to secure their diplomatic communications.

The codebreakers of the US Signal Intelligence Service were able to solve this device in 1940 and according to Russian historians the codebreakers of the Soviet Union, led by Sergei Tolstoy, also solved it.

The British codebreakers were not able to solve this system on their own but they received information and a copy of the device from their American allies in 1941.

Speculation on the German effort versus the Purple cipher machine

US reports based on the interrogation of German cryptanalysts claim that the Germans made an effort to solve the Purple cipher machine but were not succesful. However the German historian Jürgen Rohwer mentioned in his book ‘Stalin's ocean-going fleet’ that in 1996 he received a letter from a mr Cort Rave, who claimed that the Germans were in fact able to solve the Purple machine and decode the Japanese messages.

According to US reports Kurt Rave was an OKW/Chi employee detached to the Foreign Office Cryptanalytic Section (Pers Z S), so his testimony has to be taken seriously.

I have looked into this case and presented all the available information in German success with Purple?.

Unfortunately I haven’t been able to get a copy of the letter written by Rave. When I emailed mr Rohwer in 2011 he said he would look into it but he never got back to me.

Another person who made similar statements regarding the German solution of the Purple machine was Otto Leiberich, chief cryptologist of the German cipher department in the period 1972-1990.

In his article Vom diplomatischen Code zur Falltürfunktion. Hundert Jahre Kryptographie in Deutschland he said:

‘Zwei Erfolge verdienen eine besondere Würdigung: die Entzifferung des Purple-Verfahrens der Japaner und die Entzifferung der amerikanischen Chiffriermaschine M 209.

Während des Krieges hatten die Japaner eine Chiffriermaschine entwickelt und zum Einsatz gebracht, die der amerikanischen Aufklärung größte Probleme bereitete. Da gelang es einer amerikanischen Gruppe um den Kryptologen William Friedman, diese Maschine, die als purple machine bezeichnet wurde, zu rekonstruieren und zu entziffern.

Dies gilt seither in Amerika als der größte Erfolg in der Kryptologie-Geschichte. Angeregt durch eine kürzlich ausgestrahlte Fernsehsendung fragte ich bei einem ehemaligen Kollegen nach, der während des Krieges auf diesem Gebiet tätig gewesen war, und erhielt bestätigt, woran ich bis dahin nur eine ungefähre Erinnerung hatte: Auch die Deutschen hatten die Sendungen der verbündeten Japaner bearbeitet, insbesondere die Meldungen, die der japanische Botschafter Oshima aus Berlin nach Tokio sandte. Einer Gruppe von Kryptologen und Technikern der Chiffrierabteilung des Oberkommandos der Wehrmacht (OKW) unter der Leitung des Mathematikers Erich Hüttenhain war die Entzifferung ebenso gelungen wie den Amerikanern. Hin und wieder war ein Bericht schon entziffert und weitergeleitet, wenn Tokio wegen Übermittlungsfehlern um nochmalige Übersendung bitten mußte. Wenn also die Entzifferung der purple machine der größte Entzifferungserfolg während des Zweiten Weltkrieges gewesen wäre (er war es nicht!), so hätten ihn Hüttenhain und sein Team ebenfalls errungen. Leider existieren in Deutschland hierzu keine Unterlagen mehr.’

Since I was interested in this case I managed to contact mr Leiberich in 2013 and we had a short telephone conversation. Since his article was written a long time ago he didn’t remember all the details but he was able to give me the following information:

1). He did not have any documentary evidence and his statements were based on discussions with his colleagues.

2). Rave said it was a cipher machine and he remembered specific messages.

3). Regarding the years of solution he said probably 1943-44.

4). He had asked Rave why he hadn’t mentioned this success to the American interrogators and he responded that he feared it would be dangerous for him to say too much.

The last statement can be confirmed, in part, by the ‘Final report of TICOM team 3’, p12 which shows that some of the captured Pers Z higher-ups wanted to give away as little as possible and tried to influence their coworkers to do the same.

Update

I added the following information in The Irish Government Telegraph Code:

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.