Not quite true…

During WWII the top Allied officials in the US and the UK frequently communicated via a radio-telephone link protected by the Bell Labs A-3 speech scrambler. This device was not secure enough to be used at such a high level but since no other alternative was available it was used extensively by military personnel, diplomats and even Roosevelt and Churchill.

In order to secure these sensitive communications the Americans designed and built the Sigsaly device. The NSA website says about Sigsaly:

‘The SIGSALY system was inaugurated on 15 July 1943 in a conference between London and the Pentagon (the original plan had called for one of the terminals to be installed in the White House, but Roosevelt, aware of Churchill's penchant for calling at all hours of the night, had decided to have the Washington terminal moved to the Pentagon with extensions to the White House and the Navy Department building.) In London, the bulk of the SIGSALY equipment was stored in the basement of Selfridges Department Store, with an extension to Churchill's war room, approximately a mile away……….. With the coming of SIGSALY, the shortcomings of the less than effective A-3 were now a thing of the past’. 

This doesn’t appear to be the whole truth. While it is true that the system was installed in July 1943 it didn’t work properly till late 1943 and it only become fully operational in April 1944. Even after it was installed officials continued to use the A-3 for most of their communications since the only Sigsaly link was available at the Cabinet War Rooms and only a small number of officials had authorization to use it.

This information comes from the book ‘The woman who censored Churchill’, p112-3. I’ve added this information in Intercepted conversations - Bell Labs A-3 Speech scrambler and German codebreakers and German intelligence on operation Overlord.

The US AN/GSQ-1 (SIGJIP) speech scrambler

During WWII all the major participants used a number of speech privacy systems in order to protect their confidential voice communications sent over landline or radio-telephone links.

The US authorities used up to mid 1943 the Bell Labs A-3 speech scrambler, a device that utilized band-splitting and inversion. The A-3 was not secure and in the period 1941-44 the Germans were able to decode the conversations in real-time. American cryptologists knew that the A-3 was insecure and they developed the SIGSALY, a device that was a quantum leap in terms of security. However SIGSALY weighed over 50 tons and thus could only be used at prepared sites.

For field communications a speech privacy system was urgently needed but at the time it was not possible to combine a high level of crypto-security with a small and compact design. According to the postwar history of the US Army’s SSA-Signal Security Agency, in page 45, a portable speech scrambler called AN/GSQ-1 - SIGJIP was developed by Bell Telephone Laboratories in collaboration with the Signal Corps and in 1943 the responsibility for its further development was transferred to the SSA. The device was tested and its security was found wanting, however the need for such a device was so great that in 1944 several units were sent to the European, Mediterranean and South Pacific theaters. 

According to TICOM reports the Germans were able to retrieve such a device from a downed Mustang fighter and although they solved the cryptologic system, in practice it was thought that finding the ‘key’ used for each mission would be difficult due to the time element.

From TICOM I-31 ‘Detailed interrogations of Dr. Hüttenhain, formerly head of research section of OKW/Chi, at Flensburg on 18-21 June 1945’

From TICOM I-58 ‘Interrogation of Dr. Otto Buggisch of OKW/Chi’

More information on the AN/GSQ-1 is available from the book ‘Information security: An elusive goal’ by George F. Jelen, pages II-17 and II-18. According to the author the AN/GSQ-1 divided the speech signal into 37 -1/2 millisecond segments and then rearranged them based on the ‘key’. In 1944-45 they were installed on P-51 reconnaissance planes operating in Europe and one of the first in service was lost over Germany. The AN/GSQ-1 was not a success and was retired after a brief period of time not only because it offered limited security but also because P-51 pilots preferred to remove the SIGJIP and in its place install a tail-warning radar.

For those who want more info on the AN/GSQ-1- SIGJIP in the US National Archives and Records Administration - RG 457 - Entry 9032 - box 792- there is the file NR 2228 CBLL24 6144A 19450927 ‘PERFORMANCE SPEECH EQUIPMENT AN/GSQ-1 AN/GSQ-1A SIGJIP-SIGMAR’.

German 80mm Photophone - Carl Zeiss Lichtsprechgerät

One interesting communications device used by the German Armed forces during WWII was the photophone. This was a device that used light waves to transmit speech over long distances.

The photophone models built by the Germans were constructed by the well known Carl Zeiss company. One of these, the 80mm model, was captured by Allied forces in North Africa and it was evaluated by scientific personnel.

The report they produced is called ‘The 80mm German Photophone’ and can be found at the US National Archives and Records Administration.

The file can be downloaded from my Scribd and Google docs accounts.

 

Additional information on the photophone is available from site fieldgear.org and wehrmacht-awards.

Rommel’s microwave link

The North African campaign provides authors and researchers of signals intelligence with many interesting cases of ‘broken’ codes and compromised communications. Just as the German and British forces went back and forth like a see-saw the same thing happened in the field of intelligence.

Initially it was the Germans who had the upper hand and from mid 1941 to summer 1942 they benefited greatly from codebreaking. From then on however it would be the British who would succeed at reading their enemy’s codes (while keeping their own secure).

An exception to this story is something i found out about recently. Apparently Rommel had a microwave link from Derna, Libya to Athens, Greece and using it he could communicate with Higher Headquarters in Athens, Rome and Berlin.

Here is a map of the communication link, from FMS P-132 Supplement: ‘Signal Communications in the East: The Balkans and Finland’, p34

Apart from being difficult to intercept the traffic on this link was enciphered by cipher teletype, probably the Siemens and Halske T52 type. Voice communications were also enciphered with a prototype speech privacy system, at least for a time.

As far as I am aware there is no evidence that the British were able to intercept this traffic much less decrypt it.

This adds another layer in the intelligence war between Bletchley Park and Berlin and definitely diminishes the effects of reading Rommel’s Enigma ‘keys’ in the second half of 1942.

The information I’ve used comes from the following sources:

Microwave link Derna-Crete:

From FMS P-132 Supplement , p33 :

A permanent Ultra-short-wave radio communication channel operated by the Army Ordnance office later extended the Athens-Crete decimeter lines as far as Derna in Africa. By means of this channel the German Africa Corps could communicate by telephone and teletype over the permanent Balkan lines with the Italian Supreme Command in Rome, the German Luftwaffe Command in Sicily (later in Rome), the Luftwaffe units in Crete and Greece, and the Wehrmacht High Command. The line established communications between the outermost wing of the eastern Front and the Afrika Korps in Libya.

More details are given in FMS B-644 ‘Luftwaffe Communications (Greece and Crete)’ By Generalmajor Walter Gosewisch. 1947, p30

During the German drive on El Alamein one advance command post of the Commander in Chief South had been established at Derna (Libia). From here orders were issued daily by means of radio to the X Air corps stationed on Herakleion, (Crete). Owing to the danger of interception any concentrations of radio messages had to be avoided and consequently extension of the ground radio network became a matter of necessity. It was impossible, due to excessive diffraction, to transmit communications between Crete and Africa across the Mediterranean, a distance of 370 kilometers, by means of standard beam-microwave equipment which operated on a wave length of 53 centimeters.

An attempt was made, therefore, to accomplish this by installing extra powerful ultrashort wave transmitters operating on a wave length of about seven meters and by using intensely focused directional antennas. These transmitters made it possible to establish a sufficiently reliable connection which could be used for telephone and teletype traffic. The danger of interception was considerably greater when operating on a 7-meter wave length than on decimeter wave range and therefore this line was used mainly for teletype traffic by means of self coding teletype machines. (Geheimfernschreiber)

Speech privacy system:

From TICOM I-46 ‘Preliminary Report on Interrogation of Dr. Otto Buggisch (of OKH/Gen.d.NA) and Dr. Werner Liebknecht (employed by OKH and OKW as tester of cryptographic equipment) 23  June 1945’ , p3

Voice cipher machines:


C. Superimposing noise of electrons on speech and taking it out by 180 degree phase; A fixed noise level was not at all successful, but a variable number when employed had some small degree of success. This plan was actually employed back in the North African Campaign when communication from Athens, Greece to Derna, North Africa via Crete was maintained. A noise level of 1 to 4 was employed; however, the problems involved outweigh the advantages derived and the equipment was destroyed by fire and never replaced.

From  ‘Spread spectrum communications handbook, Volume 1’  , p49 [Reference found via historykb user eunometic]

The Germans used Kotowski’s concept as the starting point for developing a more sophisticated capability that was urgently needed in the early years of World War II. Gottfried Vogt, a Telefunken engineer under Kotowski, remembers testing a system for analog speech encryption in 1939. This employed a pair of irregularly slotted or sawtoothed disks turning at different speeds, for generating a noise-like signal at the transmitter,to be modulated/multiplied by the voice signal.The receiver’s matching disks were synchronized by means of two transmitted tones, one above and one below the encrypted voice band. This system was used on a wire link from Germany, through Yugoslavia and Greece, to a very  and/or ultra-high frequency (VHF/UHF) link across the Mediterranean to General Erwin Rommel’s forces in Derna, Libya.

The speech cipher device is described in the US patent US2211132A (found via klausis krypto kolumne commenter ‘Thomas’).

Intercepted conversations - Bell Labs A-3 Speech scrambler and German codebreakers

One of the most interesting codebreaking successes for the German side, during WWII, was the solution of the American A-3 speech scrambling device. This system was used on the radio-telephone link between Washington-London throughout the war. Up to summer 1943 it was the only speech privacy system employed on this link. Then the new SIGSALY device entered service and both systems were used concurrently.

The efforts of Post Office engineer Kurt Vetterlein have been mentioned in numerous books, so that part of the story is well known. However there was also another team under the Army Ordnance, Development and Testing Group, Signal Branch - Wa Pruef 7 which successfully solved the A-3 system.

As far as I know the work of this second team has not been mentioned in any book or article.

Time to take a closer look at the work of both teams and the intelligence they got from the A-3 system:

The A-3 device

In the 1920’s, when radio-telephone communications began to used by government departments and private citizens, it became clear that there was demand for devices that would protect these communications from eavesdroppers. The first system built by Bell Laboratories utilized speech inversion, meaning that the frequency of the speech was inverted on a fixed point. This system was first used on the radio-telephone circuit between Catalina Island, California and the US mainland in the early 1920’s (1). The inverter device offered protection from casual listeners, as the speech was rendered unintelligible, but the procedure could be reversed by any technically minded individual. In fact a Bell Labs report says ‘This device was thus an effective privacy arrangement against the casual listener but was very easy to crack, even in those days. An inverter can be built by any reasonably competent high school boy and, in fact, there have been instructions on how to build one in QST’ (2).

The next step was to design a device that worked on the principle of band-splitting. The speech segment was divided into separate frequency bands, these were then rearranged and in addition some of them were inverted. This became the A-3 speech privacy system. The A-3 was a 5 band system and since each band could be either in the right side up or inverted there were in theory 3.840 possible combinations (3). Field tests however showed that out of these combinations only a small number ensured speech unintelligibility and out of these only 6 were selected to be used by the A-3 (4). Every 15 or 20 seconds one of these 6 combinations was used and after 36 steps the ‘key’ was repeated (5).

Although the A-3 device was technically complex it was understood even at that time that a determined opponent with the necessary skills and with access to specialized equipment could eventually discover the operating procedure and descramble the conversations. That’s why Bell Labs called the A-3 a speech privacy system and not a secrecy system (6). Still the fact that for most of the war it was the only device available meant that it was used widely by the Anglo-Americans.

The A-3 was used by US civilian and military authorities and on the link Washington-London during WWII. The most important intercepted discussions were those between the leaders of the Anglo-American alliance, Franklin Roosevelt and Winston Churchill. It seems that in at least one case their conversations gave the Germans vital clues on impending military actions.

The Post Office effort:

The Post Office - Deutsche Reichspost was the organization responsible for telephone, telegraph and wireless communications in Germany. The Reichspostminister from 1937 to 1945 was Wilhelm Ohnesorge, a convinced National Socialist with close ties to Hitler. Ohnesorge was interested in the new radio technologies and was willing to fund research in decoding the A-3 device. How he came to know of the existence and use of this machine is not mentioned in any of the books I’ve read.

The unit that handled this operation was the Forschungsstelle der Reichspost (Research Post of the Reichspost). After the initial decision was made, two factors made things relatively easy for the Post Office people. First was the fact that the Post Office already owned an A-3 device. The second factor was their gifted engineer Kurt Vetterlein who headed the effort to decode the A-3. After researching the A-3’s operating procedure, Vetterlein and his team were able to build equipment that decoded the conversations in real-time and carried out this mission from September 1941 till 1945. Each day a large number of calls were intercepted, usually up to 60 and never less than 30 (7).

The equipment and the team were originally based in Noordwijk, Holland where the reception was excellent. However the threat of British commando raids in 1943 forced the German team to move inland to a more secure location near Eindhoven, Holland and in late 1944 because of the advancing Allied armies they returned to Germany.

The transcripts of the intercepted conversations were sent by teletype to the foreign intelligence department of the Sicherheitsdienst (security service of the SS). Then these were forwarded to Himmler, Hitler and other personalities of the Third Reich. Interesting details regarding the intercepted material are given by Dr Hans Wilhelm Thost, a journalist and employee of the SD. Thost had a strange background. In 1935 he was the London correspondent of the Völkischer Beobachter, the newspaper of the National Socialist Party. In October of that year he was ordered to leave the country. What was the reason for his expulsion? It seems that Thost may have taken part in unlawful activities like espionage. Whatever the case he was one of the people who translated the incoming A-3 material and his interrogation TICOM I-190 ’Extracts from report on interrogation of Dr Hans Wilhelm Thost’ is very interesting.

According to him the Post Office minister Ohnesorge distrusted the military and did not want to give them the transcripts of the intercepted communications. That was the reason for the Reichs Post-SD connection. Thost says that the address for Washington was Republic 2020.

In his interrogation he lists the memorable calls as follows:

a). Between War Office ,London and British Army staff ,Washington. Most of the time the caller was Brigadier Leslie Dawes and in London Brigadier Owen Young. The discussions concerned British orders of American military equipment. Cover words were used for the items (‘grapefruits ‘, ‘pineapples‘)

b). Between the Ministry of War Transport, London and British Shipping Mission, Washington. Talks concerned the allocation of shipping space. Theatres of war were referred to by cover name. (‘Arthur’s place’, ‘John’s place’)

c). Ministry of War Transport, London and representative of same organization in Washington. Talks concerned the allocation of tanker shipping space. Thost says that there was a serious shortage of tanker ships.

d).Concerning political and diplomatic matters:

Cases include British Embassy, Washington to Foreign Office, London , Dutch Government, London to its representative in Washington, in one or two cases Soviet ambassador Maisky to Soviet ambassador in Washington. Also conversations between Eden in Washington and Churchill in London.

e). Concerning economic matters. (Foreign Economic Administration , United Nations Relief and Rehabilitation Administration – UNRRA)

The most interesting calls were of course those between Roosevelt and Churchill. Their conversation of 29 July 1943 alerted the Germans to the impending Italian surrender and allowed them to take swift measures against the Italian army (8).

Other top level officials were also recorded: General Mark Clark, Lord Halifax, Averell Harriman and Harry Hopkins.

Walter Schellenberg, head of SD foreign intelligence, was the recipient of the transcripts and he mentioned the Roosevelt-Churchill talks in his memoirs and in his postwar interrogations. In ‘Report on interrogation of Walter Schellenberg 27 June- 12 July 1945’, p31 he said:

Amt Vi telephone monitoring of the Trans-Atlantic telephone service between London and Washington was very successful. This monitoring was effected from Holland, and a highly complicated machinery was used for that purpose. Before the Teheran conference, SCHELLENBERG received a report of a conversation between CHURCHILL and ROOSEVELT. Most trans-Atlantic calls referred to questions of supply. Decoding of these talks was difficult as the essential words were coded twice. Oberpostrap VETTERLEIN supervised the monitoring service in Holland. This service offered great difficulties from the technical side.

In his autobiography ’The memoirs of Hitler’s spymaster’, p418 he said:

Early in 1944 we hit a bull's eye by tapping a telephone conversation between Roosevelt and Churchill which was overheard and deciphered by the giant German listening post in Holland. Though the conversation was scrambled, we unscrambled it by means of a highly complicated apparatus. It lasted almost five minutes, and disclosed a crescendo of military activity in Britain, thereby corroborating the many reports of impending invasion. Had the two statesmen known that the enemy was listening to their conversation, Roosevelt would hardly have been likely to say good-bye to Churchill with the words, 'Well, we will do our best—now I will go fishing.'

The Post Office operation was undoubtedly a great success but it was not the only effort against the A-3 device.

The Army directed its own separate operation through the Army Ordnance, Development and Testing Group, Signal Branch Group IV - Waffenpruefung Abteilung 7/IV.

Alfred Muche and the 5B machine

Now I said earlier that all the books on codebreaking mention the Vetterlein-Post office story. However that is only 50% of the puzzle.

In TICOM report I-213 ‘Report on interrogation of Alfred Muche’, recently declassified by the NSA, a German engineer named Muche working for the Army Ordnance, Development and Testing Group, Signal Branch Group IV Section E (Wa Pruef 7 /IVe), describes his own successful effort versus the A-3 scrambler.

The WaPruef 7/IV agency was involved in special tasks during the war. They analyzed and decoded Soviet speech scramblers and built equipment that intercepted and printed Allied multichannel radioteletype traffic. Section E, headed by Dr Loetze, did research in speech privacy systems. Muche was an engineer with Section E. His life story was as follows: from 1927-37 he worked for Heliowatt Werke and in 1937 moved to WaPruef 7/IVe. For the period up to 1940 he studied domestic and foreign speech privacy systems. At the end of 1940 or the beginning of 1941 his department started the study of the encrypted transatlantic telephone link. Under Muche’s direction single sideband receivers were built and the traffic recorded at ‘Nordwyk,Holland’ [note that this was the same area that the Post Office used for their interception facility]. In order to build the receivers he got assistance from Professor Koomans of the Dutch Post Office (PTT-Staatsbedrijf der Posterijen, Telegrafie en Telefonie)

After studying the recordings with specialized equipment the Section E party found out that ‘the speech spectrum was being split into 5 bands, inverted and translated ’ …. ‘it was found that the cipher controlling the switching repeated cyclically after 36 sections.’ Since the operating procedure of the A-3 had been solved a descrambling machine known as 5B was built. The equipment was moved from Nordwyk to Ludwigsfelde (near Berlin) in late 1942. Ludwigsfelde housed a large army intercept station.

According to Muche the 5B machine became operational in the summer of ’43 and one of the conversations between Roosevelt and Churchill foreshadowed the Sicily landings and allowed the Germans to withdraw their forces with minimal losses. Unfortunately for the Germans the 5B machine was destroyed by aerial bombardment in late 1943. Muche then spent 8 months building an improved version and completed that task in the summer of 1944. The machine continued to intercept and decode the traffic till ’45 when the unit was forced to move. He did not know what happened to the machine at the end of the war. For his efforts he was given the Kriegsverdienstkreuz and a Speer reward of 10.000 marks.

Regarding the equipment he used the following companies are mentioned :

1. AEG-parts for the SSB receivers

2. Siemens - ring modulators

3. AEG - ‘‘star‘‘ modulators

4. Filters for the 5B machine - Dr Vierling ( of the Feuerstein laboratory)

5. Speech analysis equipment – Breusing Tonsystem, Berlin

More information about the disposal of the 5B machine is given in TICOM I-203 ‘Interrogation of Herbert MARINIOK and Herbert Korn, Former Members of the Reichspost and OKW/CHI’, p4

KORN confirmed MARINIOK’s statement that X Geraet was invented by Dr. LOTZE assisted by Mr MUCHE to enable the Germans to intercept transatlantic telephone conversations. Asked about the history of the apparatus, however, he stated that he had been concerned with it only since its installation at Ludwigsfelde in August 1944. He had worked with it until April 1945 when it had been taken to the Schliersee, and he had himself been one of the group which accompanied it by truck. KORN had also been on the raft which had dropped the apparatus into the Schliersee on 1 - 2 May 1945. Contrary to MARINIOK's statement, KORN claimed that the apparatus was sunk in several sections and not in one piece. The frame, which had consisted of three large parts, was dropped in sections, and the compartments of the apparatus itself were dropped separately. KORN was certain he could pick out the exact spot where the parts were sank, and stated that the nearest village was MIESBACH. Although he was certain that the construction of the apparatus could be seen should the parts be retrieved , KORN thought that no part would be usable because of the corrosive influence of the water.

Muche was just as successful as Vetterlein but until now his story was not known. Although the army’s effort wasted resources, by duplicating the Post Office operation, it was nevertheless successful and provided valuable information during the war.

Conclusion

By eavesdropping on the Allied conversations the Germans got military, diplomatic and economic intelligence. In at least one case (Italian surrender) the information they received allowed them to take swift military action and preempt the Allied plans. That event alone justified the resources spent on the A-3 both by the Post Office and the Army.

The intercepted communications between Roosevelt and Churchill are an embarrassing episode in the signals intelligence war. However the Allies knew the A-3 system was vulnerable and the SIGSALY machine which replaced it was a quantum leap in terms of security. In theory thanks to SIGSALY the Allies had absolute security from mid ’43 onwards. However it seems that the device installed in London did not work properly till October ‘43 and only became fully operational in April ‘44. Even then officials continued to use the A-3 for most of the traffic since the only Sigsaly link could be accessed at the Cabinet War Rooms and only a few people had authorization to use it (9).

Overall the story of the A-3 scrambler and the German efforts against it is an interesting chapter in the history of communications security.

Notes:

(1). Bell Labs report ‘History of speech privacy systems-1970’, p2

(2). Bell Labs report ‘History of speech privacy systems-1970’, p3

(3). According to Bell Labs report ‘History of speech privacy systems-1970’, p4 the bands used on the A-3 were A: 250-800Hz, B: 800-1.350Hz, C: 1.350-1.900Hz, D: 1.900-2.450Hz, E: 2.450-3.000Hz. The possible combinations are: (5x2)x(4x2)x(3x2)x(2x2)x(1x2)=3.840.

(4). Bell Labs report ‘History of speech privacy systems-1970’, p4 says: ‘In other words, a certain amount of intelligibility could be obtained by just listening, particularly if the listener practiced a bit. It finally turned out that there were only about eight truly private combinations which were reasonably proof against an expert listener. Even these could be understood by an expert if one combination was used for quite a time. Later tests made in the laboratory on a 5 band system resulted in the choice of just six out of 3.640 possible combinations. These are used today in the A3 system. This taught us a considerable amount about the "toughness" of speech’.

(5). Historian David Kahn says after 20 sec in ‘The Codebreakers’ and ‘Hitler’s Spies’ while the Bell Labs report ‘History of speech privacy systems-1970’, p4 says almost 15 sec.

(6). General Marshall’s testimony on A-3 insecurity, Bell Labs report ‘History of speech privacy systems-1970’, ‘A History of engineering and science in the Bell System: National Service in War and Peace’.

(7). ‘Hitler's Spies: German Military Intelligence in World War II’, p173

(8). ‘Kriegstagebuch des OKW - 1943 Teilband II’ by Percy Schramm, p853-4

(9). ‘The woman who censored Churchill’, p112-3

Sources: European Axis Signals Intelligence, NSA website, ‘The Codebreakers – The Story of Secret Writing’,  ‘Hitler's Spies: German Military Intelligence in World War II’, TICOM reports I-190 , I-203 , I-213, ‘Nazis in pre-war London’ , ‘The memoirs of Hitler’s spymaster’ , Wikipedia , ‘The woman who censored Churchill’, KV 2/95 ‘Walter Friedrich SCHELLENBERG: rose to be No. 2 in the S.D. and was close to Himmler’, National Cryptologic Museum library - David Kahn collection, Bell Telephone Laboratories report ‘History of speech privacy systems-1970’, National Defense Research Committee reports: ‘Final report on project C-43 Continuation of Decoding Speech Codes’, ‘Speech Privacy Decoding - Final Report, January 31, 1942’, ‘Kriegstagebuch des OKW-1943 Teilband II’, ‘A History of engineering and science in the Bell System: National Service in War and Peace’, Cryptologia article: ‘Review of Forschungsstelle Langeveld: Duits Afluisterstation in bezet Nederland’, General Marshall’s testimony on A-3 insecurity.

Acknowledgments: I have to thank Rene Stein of the National Cryptologic Museum for the reports from the David Kahn collection, William Caughlin and George Kupczak of the AT&T Archives and History Center for the report ‘History of speech privacy systems-1970’ and Randy Rezabek for sending me information from ‘A History of engineering and science in the Bell System: National Service in War and Peace’.

Soviet speech scrambers

Apart from codebooks and ciphers machines the major powers of WWII also used speech privacy systems to protect their sensitive radiotelephone communications.

The American A-3 device, built by Bell Telephone Laboratories , was used for the link London-Washington. Unfortunately for the Allies it was solved by two German teams .One working for the Army Ordnance, Development and Testing Group, Signal Branch – Wa Pruef 7 and the other working for the Post Office.

The successor of A-3 was the SIGSALY device which offered absolute security. The drawback was the huge size of the equipment .According to the  NSA  website it weighed 55 tons !

The Germans used devices similar to the A-3 but did not consider them secure (for obvious reasons). Michael Pröse mentions the Siemens & Halske   ’’Kleiner Leitungsverzerrer GK III’’ [Source: Pröse dissertation ,p172] .During the war they tried to develop a secure system but did not go beyond prototypes.

The Soviet government was also concerned about the security of its voice communications. According to an article in Agentura in the late 30’s they developed a scrambling device called EU-2 which used speech inversion. A more secure system was developed by ’42, the Cobol-P. 

German Signals intelligence units in the East intercepted those radiotelephone conversations and according to Karrenberg scientists at Wa Pruef 7 were able to solve them at will  up to 1943. It seems to me that this Soviet device, which the Germans called  X, must have been the EU-2 or one of its modifications.

In 1944 however a new scrambling device was introduced which proved secure. The Germans called this X². Again by comparing with the  Agentura article it seems they were referring to the Cobol-P. By the end of the war however their research had identified the principle of the Soviet device (time division scrambling with wobble inversion) and they may have reconstructed some conversations according to Huettenhain.

Time to take a closer look at all this information.

1). From EASI vol2 – p73,

37.Early Russian ciphony was solved by analysis of spectrograms

Radio telephone conversations between Moscow, Leningrad; Irkutsk, Alma Ata and Tcheljabinks, involving Russian Army and People's Commissariats, up until 1943, were enciphered by two simple methods which were said to be easily solvable by German engineers at  the Army Ordnance, Development and Testing Group, Signal Branch.(Wa Pruef 7), according to Corporal Karrenberg, of the Signal Intelligence Agency of the Army High Command (OKH/GdNA) .These two methods of Russian enciphering were:

a. Inversion, employing superimposed modulation of several audio frequencies; and,

b. Distortion, by artificial raising of amplitudes of speech harmonics.

German scientists were able to solve these two simple enciphering methods by recording the enciphered speech, making spectrograms from the recordings, and analyzing them .Evidently the voice engineers could see the results of the inversion and distortion, on careful inspection, and could readily identify the frequencies and methods used for encipherment. They tried it: only a few times, according to Karrenberg, but were successful at will. At the beginning of 1944, however, the simple enciphering methods were dropped by the Russians, radio telephone traffic networks themselves were changed, and no further entry was gained by the Germans. Dr. Buggisch of the Signal Intelligence Agency of the Supreme Command, Armed Forces (OKW/Chi) studied spectrograms of this later unsolved Moscow-Madrid radiophone traffic at the Army Ordnance, Development and Testing Group, Signal Branch Laboratories (Wa Pruef 7) where he became convinced that Russian ciphony then involved time scrambling, with the length of the individual time segments being 10 milliseconds each, and a  synchronizing pulse occurring every .6 second. The number of "pickup heads" used by the Russians to obtain this time, scrambling was reported in one interrogation to be three and, in another to be four. German engineers were unable to learn any more than this from the spectrograms. They could reconstruct fragments of speech, they thought, but "the validity of the solution did not satisfy Dr. Huettenhain's critical sense," when shown to him. Dr. Huettenhain, who consulted with Dr. Buggisch, believed that some form of one-time strip might have been used to key the time transposition, as he could find no: period whatever in the encipherments.

2). From EASI vol4,p44

The four independent Stationary Intercept Companies assigned to work on the eastern front had the following assignments. To Feste 11 was assigned coverage of high-frequency traffic on the Red Army and the NKVD. Originally, this Feste was located at Winniza, latterly at Kiev. The other two Feste, 7 and 8, concentrated an special Russian traffic. Feste 7 was the Russian Baudot reception station at Minsk. In 1942-43 it was moved to Loetzen where it became part of Section 4 or the HLS Ost and continued to intercept Russian Baudot traffic. Feste 8 was the former Army intercept station at Koenigsberg. After 1942, this station concentrated on Russian wireless telephone traffic called by the Germans Russian X-traffic. Attempts were made to pick up this traffic by equipment developed by Army Ordnance, Signal Equipment Testing Laboratory (Waffenpruefung, abbreviated Wa Fruef 7). The channels monitored ran east of Moscow; the traffic was mainly economic. From 1942 to 1944, this traffic was successfully recorded; but after 1944 the Russians scrambled their wireless telephone traffic, and after unsuccessful efforts to intercept this scrambled type had been made, the monitoring was dropped.

3). From TICOM I-213 ''Report on interrogation of Alfred Muche'' ,p3

Russian Systems. 

17. MUCHE himself never worked on Russian systems but he stated that they were first recorded and worked on in 1944 by a party headed by LOTZE. In February 1945 MUCHE was visited in hospital by LOTZE who told him that the Russian system had been broken and that basically it was a TIGERSTEDT system ( =TDS), with wobble inversion. MUCHE could not remember, or was never told, the number of TIGERSTEDT heads involved; he thought it might have been seven. He did not know the period of the TIGERSTEDT key, or even if it had one.

4). From I-31 ‘Detailed interrogations of Dr. Hüttenhain, formerly head of research section of OKW/Chi, at Flensburg on 18-21 June 1945’, p12

5). From TICOM I-2 ‘Interrogation of Dr. Huettenhain and Dr. Fricke at Flenshurg, 21 May 1945’, p2

A. THEY HAD FINALLY A SECRET R/T OF WHICH ONLY A  SMALL PART OF A FEW MESSAGES WERE READ. THIS WAS PROBABLY USED IN DIPLOMATIC AND ECONOMIC CIRCLES. WE WERE NOT SURE BECAUSE ONLY BITS WERE READ. WE KNOW HOWEVER THAT THE RUSSIANS WERE EXPERIMENTING WITH IT.

Q. WHAT ARE THE PRINCIPLES OF THIS MACHINE?

A. SYSTEM IS KNOWN AS TIGER-STEDT AND IS THE SAME AS THAT USED BY AMERICAN MUSTANG GROUPS. SPOKEN PLAIN TEXT IS OSCILLOGRAPHED ON STEEL TAPE AND LENGTHS OF TAPE ARE CUT AND THEN REASSEMBLED.