Monday, February 19, 2018

Candle in the Dark: COMINT and Soviet Industrial Secrets, 1946-1956

The study ‘Candle in the Dark: COMINT and Soviet Industrial Secrets, 1946-1956’ by Carol B. Davis is available for download from the NSA website.

This version (unlike the copy at the Cryptologic Museum’s Library) is complete!

Saturday, February 17, 2018

To err is human vol 4

In my essay Rommel’s microwave link I had mentioned that a German speech cipher system was used on a microwave link connecting the German high command with Rommel’s HQ in North Africa.  

According to ‘Spread Spectrum Communications Handbook’ vol1:

'In 1935, Telefunken engineers Paul Kotowski and Kurt Dannehl applied for a German patent on a device for masking voice signals by combining them with an equally broad-band noise signal produced by a rotating generator. The receiver in their system had a duplicate rotating generator, properly synchronized so that its locally produced noise replica could be used to uncover the voice signal. The U.S. version of this patent was issued in 1940, and was considered prior art in a later patent on DSSS communication systems. Certainly, the Kotowski-Dannehl patent exemplifies the transition from the use of key-stream generators for discrete data encryption to pseudorandom signal storage for voice or continuous signal encryption. Several elements of the SS concept are present in this patent, the obvious missing notion being that of purposeful bandwidth expansion.

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.'

After having a look at google patents I saw that Vogt was credited with a patent and I thought that this was the speech cipher system but I was corrected by klausis krypto kolumne commenter ‘Thomas’, who linked the Kotowski-Dannehl patent.

Thus in Rommel’s microwave link I’ve added a link and pics to patent US2211132A.

Friday, February 2, 2018

Joint Chiefs of Staff evaluation of Office of War Information ciphers

During WWII the US Office of War Information engaged in intelligence gathering and propaganda activities against the Axis powers.

The representatives of the OWI used various cipher systems in order to protect their communications and these systems were examined by the Joint Chiefs of Staff.

A summary report was issued in July 1944 and it found problems with physical security, classification procedures, stereotyped messages and cipher reuse.

Regarding OWI ciphers it was noted that ‘Present double transposition keys have been in use since they were produced by the Signal Corps in late 1942 and early 1943’ and the recommendation was ‘That immediate supersession of these keys be accomplished and that provision be made for their more frequent supersession in the future’.

Source: US National Archives, collection RG 208, Office of Wartime Information: General Records of the Security Officer, Entry 9. Location:  350/71/17/6, Box 1. Folder Communications Survey OWI.

Acknowledgements: I have to thank Robert Hanyok for locating and copying the JCS evaluation.

Thursday, February 1, 2018

Article on Germans signals intelligence operations in occupied Yugoslavia

The ‘Journal of Intelligence History’ article ‘The German ‘ultra’: signals intelligence in Yugoslavia 1943–1944’ by Gaj Trifković has interesting information on the dissemination and use of signals intelligence by the Germans in their war against the Chetnik and Partisan resistance movements in WWII.


This article deals with the extensive signals surveillance program operated by the Wehrmacht and directed at their most dangerous enemy in the Balkans, the Yugoslav Partisans. This subject has so far received surprisingly little attention in academic circles despite the fact that it was one of the crucial pillars of the entire Axis counter-insurgency effort in Yugoslavia and that it was one of the most successful actions of its kind conducted by the German intelligence. Based largely on previously unpublished primary sources, as well as post-war literature, this article will outline the workings of the program during its heyday in the years 1943–1944 and seek to establish its impact on the battlefield. As such, it will hopefully prove to be useful to both students of wartime events in the Western Balkans and to researchers of intelligence services during the Second World War in general.

Tuesday, January 30, 2018

Monday, January 29, 2018

Staff Study on OSS Cryptographic Plan - January 1945

Another document that has information on the OSS crypto systems is ‘Staff Study on OSS Cryptographic Plan’, available from the US National Archives - collection RG457- Entry 9032 - NR 3280 ‘Staff Study on OSS Cryptographic Plan’.

The report is also available from the journal ‘Cryptologia’, vol13, no.3:


  SPSIC-6                                                                                            8 January 1945

MEMORANDUM for Assistant. Chief of Staff, G-2
Subject: Staff Study on OSS Cryptographic Plan
The enclosed staff study is forwarded for your consideration and comment,

For the Chief Signal Officer:  
                                                                                      W, Preston Corderman
                                                                                                                                                                                                                                          Colonel, Signal Corps
                                                                                                                                                                                                                                     Chiefs Signal Security Branch
1. Incl
Study on OSS Cryptographic Plan



1. How may the need of OSS for a high grade, high speed cryptographic system be satisfied?


2. OSS has a requirement for a high grade, high speed cryptographic system for the encipherment and decipherment of secret traffic.

3. At the present time OSS is using the Converter M-134-A (short title SIGMYC) to satisfy this requirement.

4. Prior to 5 April 1944, eight (8) SIGMYC were issued to OSS.

5. The Assistant Chief of Staff, G-2, authorized the issue of twenty-six (26) SIGMYC to OSS by memorandum for Col. Corderman from Col. Clarke dated 5 April 1944, to meet the expanding needs of that organization.

6. Since 5 April 1944, twenty-one (21) SIGMYC have been delivered to OSS. That organization now holds twenty-nine (29) machines; five more are available for issue.

7. In the past OSS has used one universal set of rotors with SIGMYC. These rotors were replaced once.

8. In September 1944 OSS requested two new sets of rotors, one set to be used in Europe and the other set in the Far East. Thirty-eight (38) sets of rotors SIGRHAT (for use in the Far East) have been issued in compliance with that request.

9. Twenty-five (25) sets of rotors SIGSAAD (for use in Europe) have also been issued.

10. Instructional documents associated with SIGMYC are "Operating Instructions for Converter M-134 and M-134-A (Short title SIGKOC and ‘photographs and Drawings of Converter M-134-A (short title SIGVYJ). No copies of these publications are available for issue. This situation was caused by the destruction of the instructional documents when Converters M-134-A were turned in by Army holders.

11. Requests are received for spare parts with each request for the issue of a SIGMYC. The spare parts list always include rotor stepping solenoids. There are no rotor stepping solenoids on hand in this agency. Three requests for these items have not been fulfilled.

12. In accordance with authorization of the Assistant Chief of Staff, G-2, 27 July 1944, one SIGTOT room circuit was furnished OSS in Washington. Authorization did not extend to the issuance of tapes for use with this equipment. Additional SIGTOT circuits have been made available to OSS in Europe. That organization is procuring additional tape punching equipment to meet the increased demand for tape. OSS requested the loan of such equipment until they are prepared to fulfill their own needs for tape. This branch is supplying OSS with sufficient tape until that organization is self-supporting in this respect.

13. Four (4) SIGCUM have been issued to OSS with the approval of the Assistant Chief of Staff, G-2, 28 April 1944. These machines were sent to OSS in North Africa to replace four (4) SlGCUM which were loaned to OSS by NATO and subsequently recalled by the latter organization.

14. Within the past six (6) months the communications requirements of OSS have markedly increased. The cryptographic requirements have expanded proportionately. The rapid expansion is vividly illustrated by the strip cipher requirements of that organization. In June 1944 SSA requested OSS to furnish a monthly quota of desired material in order to adjust production schedules here. The monthly quota of strip cipher systems needed is now larger than the total number of strip systems issued to OSS over a period of twenty (20) months.

15. It is believed that the OSS will request the five (5) remaining SIGMYC of the authorized allotment of twenty-six (26) machines. Instructional documents are not available for issue with these converters. The reprinting of these documents presents a major reproduction job.

16. OSS encounters an ever present maintenance problem since the machines are constantly breaking down. It is believed that the time is not far distant when it will be impossible to maintain the machines adequately,

17. In order to provide new rotors in the future it will be necessary to have rotors returned from the field by OSS for rewiring. Thus, a rotation process will be established to meet new demands for rotors which will result in the wearing out of the rotors within a relatively short time. It is noted that it would take between one to two years to procure new rotors.

18. OSS is now trying out a modification of the standard --text deleted -- device, which utilizes -*- --text deleted--. That organization is contemplating an increase in the distribution of these --text deleted – to include the standard --text deleted – held by OSS, thus, permitting inter-communication between the two machines. The cryptographic principle involved his been approved by the Signal Security Agency. OSS plans to utilize the -*- --text deleted-- for secret radio transmissions.

19.  The question arises as to what other means are available. The following items of equipment are considered:


This system provides adequate security but the scarcity of equipment and the difficultly of providing sufficient quantities of one-time tape render its use impracticable. In addition SIGTOT is not at present adapted to multi-holders of a common system, which is an operational requirement


 Under present policy, it would be necessary to assign a crypt team with each machine in order to make them available to OSS. This presents a problem of securing sufficient personnel which appears insurmountable at the present time. Furthermore, the use of SIGABA as a solution to this problem is not generally regarded with favor.


The communications and cryptographic problems of OSS are developing rapidly in the Far East where traffic is transmitted largely by radio. Since SIGCUM may not be employed for secret traffic transmitted by means of radio the use of this machine would not provide a solution to the problem, Although SIGCUM would be a satisfactory substitute for SIGMYC in Europe, a revision of the cryptographic facilities of OSS in that area is not considered feasible at this time.


This converter provides adequate security to fulfill the need for a high grade cryptographic system and is well adapted to multiple holders of a common system. Since it is not a high speed system, it would not fulfill this requirement.


This system would provide adequate security and speed to meet the outlined requirements. However, since SIGLASE is still in the development stage and the expected date of issue is unknown it is not the immediate answer to the OSS problem.

20. From the point of view of this branch the problem could be most acceptably solved by making Army facilities available to OSS. It is realized that the latter organization would probably not be favorably disposed toward such a solution,


21. The continued use of SIGMYC by OSS in the Far East will present maintenance and 
distribution problems which will be virtually impossible to solve.

22. A replacement for SIGMYC is needed.

23. SIGABA, SIGCUM and SIGTOT are not completely acceptable substitutes.

24. SIGFOY and SIGLASE would be a solution to the problem but since it will require from six to nine months to manufacture the SIGLASE, it cannot be considered an immediate solution.

25. It appears that the only immediate solution to the problem is for OSS traffic to be handled by Army cryptographic facilities.


26. That OSS be requested to utilize Army cryptographic communications facilities where such exist.

27. That OSS use its own cryptographic communications facilities where Army facilities do not exist.

28. That, at such time as the equipment referred to in paragraph 27 becomes unserviceable, service be maintained by those Army cryptographic facilities and/or equipments as may then be available.

A report dated 8 February 1946 (found in SRH-366 ‘The history of Army strip cipher devices’) has more information on the implementation of the aforementioned OSS cryptographic plan.

Wednesday, January 24, 2018

Army Security Agency operations in Early Cold War Germany

The interesting article ‘The U.S. Army Security Agency in Early Cold War Germany’ is available in the latest issue of Army History Magazine.

Sunday, January 14, 2018

Joint Chiefs of Staff evaluation of Office of Strategic Services ciphers

In 1943 and 1944 the US Joint Chiefs of Staff evaluated the cryptosystems used by the various US government agencies.

For example the report on State Department codes and ciphers for 1943 can be found in the NSA website and the report of 1944 is in the US national archives, in collection RG 457- Entry 9032- box 1384 - 'JCS Ad hoc committee report on cryptographic security of government communications'.

The ciphers of the Office of Strategic Services were also evaluated and there is some information on this topic in the US national archives, specifically Record Group 226 - Series: Correspondence Files, 1942 – 1946 - File Unit: 17) Cryptographic Security:

Unfortunately there are no detailed reports on the subject but from the information presented above it seems that even as late as 1944 OSS communications were sent on vulnerable cryptosystems (double transposition and M-138-A cipher).