In WWII Poland fought on the side of the Allies and suffered for it since it was the first country occupied by Nazi Germany. In the period 1940-45 the Polish Government in Exile and its military forces contributed to the Allied cause by taking part in multiple campaigns of war. Polish pilots fought for the RAF during the Battle of Britain, Polish troops fought in N.Africa, Italy and Western Europe and the Polish intelligence service operated in occupied Europe and even had agents inside the German High Command.
Although it
is not widely known the Polish intelligence service had spy networks operating
throughout Europe and the Middle East. The Poles established their own spy
networks and also cooperated with foreign agencies such as Britain’s Secret
Intelligence Service and Special Operations Executive, the American Office
of Strategic Services and even the Japanese intelligence service. During
the war the Poles supplied roughly 80.000 reports to the British intelligence
services (1), including information on the German V-weapons (V-1
cruise missile and V-2 rocket) and reports from the German High Command (though
the agent ‘Knopf’) (2).
The
activities of the Polish government departments and intelligence agencies
attracted the attention of both Germany and the USA and UK and their
codebreakers were able to solve most of the Polish cipher systems.
Compromise
of Polish communications by foreign powers
The
Polish diplomatic and consular systems
German
effort
Foreign
diplomatic codes and ciphers were worked on by three different German agencies,
the German High Command’s deciphering department – OKW/Chi, the Foreign
Ministry’s deciphering department Pers Z and the Air Ministry’s Research
Department - Reichsluftfahrtministerium Forschungsamt.
The first
Polish diplomatic cipher system solved by the Germans was a 4-figure codebook
introduced in the 1920’s. The basic values were enciphered by simply
substituting each number by its cipher equivalent. The cipher system changed on
a daily basis. Obviously, this system offered little security and was easily
solved by the Germans, who were quickly able to reconstruct the tables giving
the daily substitution settings (3).
In 1933 a new main 4-figure codebook was introduced called ‘Code 45’ (4), which was enciphered using numerical sequences generated from two tables, each with 100 4-digit groups. The previous codebook was used for consular traffic (5).
The codebook
was basically a dictionary that assigned a 4-figure group to each word. For
example, the word ‘France’ would have the code 5538, ‘Foreign Minister’ 2090,
‘negotiations’ 0231 etc etc
So, the
cipher clerk would first use the codebook in order to find the code groups
corresponding to the words of the message and then he would have to use the
subtractor tables in order to encipher them. This means that each code group
would be subtracted from the key groups (of the subtractor table) without
carrying over the numbers.
For example,
let’s say that the following message is handed to the cipher clerk:
Foreign
Minister requires clarification of your previous telegram
Let’s assume
that using the codebook this becomes: Foreign Minister =2591 , requires =7482 ,
clarification =5556 , of =3309 , your = 4610 , previous= 4349 , telegram= 0144
So, the
message becomes 2591 7482 5556 3309 4610 4349 0144
This will be
enciphered using the subtractor tables valid for this time period using the
system described in the following paragraphs.
Let’s assume
that the numerical sequence selected is 5668 8301 3496 3540 7778 3985 8589
Now he would
subtract the code groups of the message from these key groups, without
carrying.
5668 8301
3496 3540 7778 3985 8589 - key groups
2591 7482
5556 3309 4610 4349 0144 - code groups
---------------------------------------------------
3177 1929
8940 0241 3168 9646 8445 - cipher groups
The cipher
groups would be transmitted and the receiving party would identify from the
indicator of the message the numerical sequence used for encipherment and
reverse the process by subtracting the cipher groups from the key groups. This
would reveal the code groups whose meaning would be deduced from the codebook.
Obviously,
this was a time-consuming operation and prone to errors due to mistakes in
encipherment. However, it was thought at the time that the use of both a
codebook and enciphering tables provided a high level of security against enemy
codebreakers.
The indicator
system worked on the following principle (6):
a). A
10-letter word or phrase was selected and each letter was numbered from 0-9
according to their position in the alphabet. If the same letter is present more
than once, we number them starting from the one to the left. For example,
PONIESIONA
9753204861
b). In the
two subtractor tables containing 10x10 4-figure groups the numerical key is
written vertically on the left of each table. For the first table the numerical
key is added to its first value without carrying so 9753204861+9=8642193750.
The value 8642193750 is written at the top of the first table. For the second
table the numerical key is added to its second value without carrying so
9753204861+7=6420971538. This value is written at the top of the second table.
Thus, in
both tables each subtractor value can be identified by its coordinates from the
left and top.
c). The
first subtractor value to be used in enciphering the code values will be the
one in the first table designated by the coordinates 1-1, the second subtractor
value will be the one in the second table designated by the coordinates 1-1,
the third value will be taken from the first table 1-2, the fourth from the
second table 1-2,……, the 20th value will be the one in the second table with
coordinates 1-0, the 21st the one from the first table with coordinates 2-1 etc
Thus the 200
subtractor values of the two tables can be used in mixed order.
d). The tables can be reused for another 200 subtractor values by inverting the top numerical coordinates sequences. So, in the first table the sequence becomes 0573912468 and in the second table 8351790246. The same procedure as before is used to get the subtractor values.
The new
‘Code 45’ was investigated by Pers Z in the 1930’s without success but in 1939
the effort was restarted and thanks to captured material and the indicator
instructions it was possible to solve it and the first messages were decoded in
early 1940. Solution continued in 1940 and the system was solved currently in
1941 and 1942, till October ’42 when it was replaced by the enciphered
codebooks ‘Alpha’ and ‘Code 50’. The traffic intercepted came from London,
Washington, Bern, Moscow, Madrid, Rome (Vatican), Istanbul (7).
Apart from
the main diplomatic codebook, several low-level systems were solved by the
Germans throughout the war (8).
UK effort
In Britain
foreign diplomatic cipher systems were worked on at the Diplomatic Section of
the Government Code and Cypher School (GCCS), located in Berkeley Street,
London. The official title of the unit was Government Communications Bureau (GCB)
(9).
According to
a report from 1942 no Polish diplomatic codes had been solved since 1928 (10). The
new systems ‘Alpha’ and ‘Code 50’ had not been solved by 1945. The low level ‘Cypher
Z’ (single transposition of text) was solved (11).
US effort
In the
Unites States diplomatic traffic from European countries was worked on at the Army
Security Agency. The agency only started to work on this type of traffic in
1944 and the unit working on Chinese, Bulgarian, Greek, Yugoslav, Croat,
Polish, Czechoslovakian and Slovakian traffic was B-III-d-2 (12). Difficult
cipher procedures were first solved at the Research Section before being passed
on to the other departments for regular exploitation.
It doesn’t seem like the systems ‘Alpha’ and
‘Code 50’ had been solved by 1945, although progress had been made in sorting
the traffic and working on the encipherment and indicator systems (13).
Two low
level systems called PLA and PLE were solved in 1943 and 1944 (14).
The PLA system used mono-alphabetic substitution and carried mostly financial messages between London, New York, Washington, Algiers and Dakar.
The PLE
system used single columnar transposition and carried diplomatic and consular
traffic between the Polish foreign ministry in London and various American
capitals (Washington, Ottawa, Mexico City, Santiago de Chile, Buenos Aires, Rio
de Janeiro, Havana).
During the
war there was exchange of information and traffic between the US and the
British codebreakers on European diplomatic systems. The British had an
advantage in this area since they had been intercepting this traffic for
decades and they had been following the development of these cipher systems.
Meanwhile interception from the USA was difficult and in the interwar period the
Army Security Agency had focused on the solution of Japanese traffic.
Polish
military intelligence ciphers
The
organization in charge of military intelligence was the Second Section of the
Polish General Staff. Information from occupied Europe was gathered by military
attaches through their spy networks and by undercover resistance networks
controlled by the Department.
The military
intelligence service cooperated with foreign agencies such as Britain’s Secret
Intelligence Service and Special Operations Executive, the American Office
of Strategic Services and even the Japanese intelligence service.
Their main
cipher system was the 4-figure codebook (10.000 groups non alphabetical)
enciphered with subtractor tables (15). In 1944 they introduced the stencil
subtractor system, so the security of the system was dependent on the codebook,
the subtractor tables and from 1944 the stencils used in each link.
The codebooks were the 555 (probably prewar), 666 (probably introduced in 1941), 777 (probably introduced in 1943), 888 (introduced in September 1944).
Initially
the subtractor tables were issued with 3 pages, each page valid for 4 months.
Tables consisted of 4-figure groups, usually 20 lines of 30 columns, with
bigram indicators placed around the table. Some improvements were introduced
during the war such as sets of 4 tables for use at the same time, 3-figure
indicators and tables of different sizes.
The biggest
improvement in cipher security was the introduction of the stencil subtractor
frame in 1944. The new system was used with tables that had 3-4 pages and the
tables were not made of 4-figure groups but had uninterrupted lines of numbers.
Each stencil
was used for about 3 months and then replaced together with the subtractor
tables (although sometimes the same stencil was used for longer periods of time
with several sets of tables). The stencils could be set in different positions
vertically and horizontally and they could also be reversed.
German
effort
Polish military
intelligence ciphers were worked on at the German High Command’s deciphering
department – OKW/Chi. The section dealing with Polish systems was headed by the
civil servant Berndt and had about 20 workers (16). The solution of the
enciphered 4-figure codebook was their greatest achievement and one of the
outstanding achievements of OKW/Chi. An activity report of OKW/Chi (17),
covering the 1st half of 1944, says:
‘Government
codes and cyphers of 33 European and extra-European States and Agents Lines
were worked on and deciphered. 17,792 VN were produced, including 6.000 agents'
messages. From point of view of numbers, the list was headed by Government
reports of the U.S.A., POLAND, and TURKEY’.
‘A number
of complicated recypherings, principally American (U.S.A.) and Polish, have
been broken’.
Since the
war diary of OKW/Chi is not available the information we have comes from
postwar TICOM reports and thus not all the details of this case are known.
The
mathematical research section of OKW/Chi was responsible for solving
complicated encipherment so that they could be exploited by the country
sections. The person responsible for the investigation and solution of the
Polish cipher was the mathematician Ernst Witt. According to his colleague
Wolfgang Franz (18) ‘the most successful work along with that on the Am10
was that of professor WITT, who very skillfully solved a cipher of the Polish
Government in Exile in London. This was a complicated grille which was laid
over a large number sheet. Several such grilles were constructed and messages
were read currently’.
According to Erich Hüttenhain, head of the mathematical research department, they initially solved the system when only subtractor tables were used and the codebook was recovered but after some time their solution failed and by solving messages in depth, they found that a stencil was used on the subtractor tables. This new system was then broken since they had the basic codebook and they only had to recover the stencil and the subtractor tables. By 1945 roughly 12 different stencils and a large number of subtractor tables had been solved (19).
Mechanical
aids to cryptanalysis were used against the Polish cipher system. Apart from
standard IBM punch card machines there was also a specialized device called
‘Witzkiste’. The ‘Witzkiste’ or ‘Brainbox’ was a photoelectric device using
lattice frames for removing additive from a column of super-enciphered code
groups arranged in depth. It could be used with any four-digit (or smaller)
enciphered code, the frequency of whose unenciphered code groups had been
discovered from previous removal of additives (20).
If the codebook, the stencils and the subtractor tables had been changed at the same time solution would not have been possible (21). It seems that the Poles believed that even if their codebooks had been compromised this would not affect the overall security of their cryptosystem since the main protection was the encipherment method (22).
Notable
cases:
The greatest
successes were achieved against the Polish military intelligence networks Ekspozytura
S in Switzerland and Ekspozytura F2 in France (23).
Ekspozytura
S (network of Major Choynacki)
The Polish
intelligence network in Switzerland was controlled by Major Szczesny Choynacki,
Polish Vice-Consul in Berne. 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 ran intelligence networks in Switzerland.
The Poles had
their own networks and also collaborated with the other Allied intelligence
agencies such as the intelligence service of the Free French, the American OSS
and the British SIS. The messages of Major Choynacki were read by the Germans
and they revealed details about intelligence operations as well as the
identities of highly placed agents numbered in the 500 series (such as agent
‘594’).
German decodes of the Bern-London traffic can be found in pages 878-916 of ‘KODY WOJNY. Niemiecki wywiad elektroniczny w latach 1907–1945’. They date from October 1942 to September 1944 and are signed ‘Szef II Oddzialu Sztabu’, ‘Darek’, ‘Gano’, ‘Hugo’, ‘Mak’, ‘Orkan’, ‘Espe’, ‘Jerzy’.
Ekspozytura
F2
In occupied
France the intelligence department of the Polish Army’s General Staff organized
several resistance/intelligence groups tasked not only with obtaining
information on the German military but also with evacuating Polish men so
they could serve in the Armed Forces. These networks soon attracted the
attention of the German security services and from 1943 the communications of
the F2 network were continuously solved.
This allowed
the Germans to monitor the activities of these groups and keep them under
control, especially in the period preceding the Normandy invasion of 1944.
German
decodes of the London-Grenoble traffic can be found in pages 793-877 of ‘KODY
WOJNY. Niemiecki wywiad elektroniczny w latach 1907–1945’. They date from
July 1943 to October 1944 and are signed ‘Szef II Oddzialu Sztabu’, ‘Marian’,
‘Alfred’, ‘Szef Ekspozytury II Oddzialu Sztabu’, ‘Lubicz’,
‘Vox’, ‘Los’, ‘Rawa’, ‘Klemens’, ‘Major Zychon’,
‘Mikolaj’, ‘Bernard’, ‘Biz’, ‘Zenon’.
UK effort
The Polish
military intelligence ciphers were worked on at the Government Communications
Bureau (GCB), located in Berkeley Street, London.
The traffic was
first solved in 1942 thanks to a captured codebook and subtractor tables (24)
and the links identified were between the Polish General Staff in London and
the military attaches in Bern, Washington, Stockholm, Mexico.
The solution of Polish ciphers was an important undertaking for the GCB codebreakers. The introduction of the stencil subtractor frame in 1944 made solution harder but they developed methods for dealing with this system and they continuously exploited this traffic in the period 1942-45 (25).
Their
reports from the period March ’44 to March ’45 show that they concentrated on
the links London-Bern and London-Washington (26).
There is no
evidence that the British were aware of the German success against the Ekspozytura
S network during the war. However, decoded messages from the Ekspozytura F2
network (London-Grenoble) were identified in German intelligence traffic in
August 1944 (ISK/ISBA decodes) (27). No information is available regarding
their actions in response to this compromise.
US effort
As has been
stated previously the Army Security Agency started to work on the traffic of
Central European countries in 1944. The unit responsible for exploitation of
this traffic was B-III-d-2, with difficult cipher procedures first solved by
the Research Section.
The military
intelligence cipher was designated system PLF. Despite the close contact with
the British codebreakers it seems that in this case they refused to share all their
results with the Americans, since a report from 1945 says (28):
‘This is to acknowledge receipt of the query on PLF (Militpologne) by O.I.C. SPSIS-9, recently brought to me. I saw Commander Denniston and Mr. Jones Williams on this. They believe it improper to furnish us with any results of their analysis, beyond a general description of the system, and are sorry if we obtained a different impression at any time’.
By
intercepting and evaluating this traffic the US codebreakers might have been
able to solve the PLF system in 1945 but no details are available on their effort
pi(29).
Polish
intelligence ciphers Middle East and occupied Poland
German
effort
The
organization responsible for the solution and exploitation of Polish agents’
traffic was the German Army High Command’s codebreaking department Inspectorate
7/VI. Specifically, Referat 12, which was formed in August 1942 in order to
deal with Allied agents’ systems. In November 1943 the entire department was
moved close to the OKW Funkabwehr HQ at Dorf Zinna, Jüterbog and became
subordinate to OKW/Chi (30).
The reports
of Referat 12 show that the Polish networks were called PS nets by the Germans
and after investigation of their cipher procedures in July and August 1942
the first messages were solved in September ’42. The traffic of several nets was
solved in the period 1942-44, mainly lines 6521 London-Warsaw (RIS), 6509, 6508
Bucharest-Turkey, 6003 London-Nice (31). However, the last report of Referat 12
found in the War Diary of Inspectorate 7/VI is that of February ’44 so our
knowledge of their successes is incomplete.
According to Major Mettig, head of Inspectorate 7/VI in the period 1941-43 and later moved to OKW/Chi, the solution of the messages between the Polish Government in exile in London and the Polish resistance movement was one of the outstanding achievements of Referat 12 (32).
UK effort
The radio
traffic of the minor European Allied countries was monitored by the British for
security reasons and in March 1944 they carried out an investigation of Polish
radio traffic in the Middle East (33). In general, they found few issues with
signals security with the notable exception of a consular cipher used between Cairo,
Jerusalem, Istanbul. The cipher used was single transposition and it was not
considered secure. The Poles were told not to use this system for important
messages and a subsequent check showed that they adhered to this rule (34).
Regarding the Polish resistance movement traffic there is no indication that it was monitored and solved by the British codebreakers prior to 1944. In September 1944 they decoded German messages containing the translations of decoded Polish resistance traffic on the link London-Warsaw (35).
US effort
There is no
indication that the traffic of the Polish intelligence networks in the M.E. and
in occupied Poland were worked on by the US codebreakers.
Conclusion
In the
interwar period the Poles distinguished themselves by being the first to solve
the German military’s Enigma machine. During the war their intelligence
department operated throughout occupied Europe, gathering information from
spies and resistance groups and they even penetrated the German High Command.
However,
while they were busy gathering intelligence for the Allies they neglected to
secure their crypto systems. The Germans were able to solve their diplomatic,
military intelligence and resistance movement codes and they gained valuable
information from the decoded messages. The compromise of the communications of
Major Choynacki in Switzerland, of the Ekspozytura F2 network in France and of
the Polish resistance movement were major German successes.
The British
and American codebreakers were also able to solve the ciphers of the military
intelligence service and they obviously thought so highly of this source that
they never made an attempt to warn the Poles and get them to secure their
systems.
This was a
risky operation since the information passing on Polish links could also
endanger the security of Allied military and diplomatic plans. This is admitted
in the British report DS/24/1556 of October 1945, written by Commander Russell
Dudley-Smith (head of cryptosecurity at Bletchley Park) (36), which said:
‘The whole
question of the control of Polish traffic during the war was a major headache
which was never satisfactorily resolved’.
………………………………………………………………………………………….
‘I doubt
whether a further post-mortem into this matter would achieve very much, but
there does seem to be a real lesson to be learnt for the future. Owing to a
combination of circumstances, (including a delicate political situation,
certain special security requirements, and so on), large quantities of
uncontrolled and unknown traffic in low grade systems were passing from U.K.
throughout the war, not only in undeposited systems (as indeed was the case
with all Allied diplomatic traffic) but without our having any knowledge of the
contents of the messages or the nature and extent of the leakage, owing to the
fact that the cypher versions never reached Berkeley Street’.
Considering the inaction of those in charge, it is evident they believed the potential rewards outweighed the risks involved.
Additional
information
British
SS Frame vs Polish SS Frame
The basic
British cryptosystem for important radio-traffic was the enciphered codebook.
These 4-figure codebooks were enciphered with subtractor tables, using the
non-carrying system. In 1943 the British changed their cipher procedures by
introducing the SS Frame. The stencil subtractor frame was used together with
the day’s enciphering table in order to reveal the numerical values to be used
in enciphering and deciphering messages. The Royal Navy started using the SS
Frame in July 1943 and it was introduced for combined British-US- Canadian
service in January 1944 (37).
The Poles
used 4-figure codebooks enciphered with subtractor tables and in 1944 they also
introduced the SS Frame. Their version differed from the British SS Frame in
the number of apertures. While the British version had 100 apertures (38) the
Polish version only had from 28 to 40 randomly placed apertures (39) or according
to another source 24 to 50 (40). It is not clear why the Poles used a weaker
version of the SS Frame…
Polish cipher
machines
Lacida
The Poles
used hand ciphers and codebooks during the war. Their only cipher machine was
the LCD-Lacida, a non-reciprocal rotor machine equipped with 6 rotors (3 moved
during encipherment). The machine was used during the period 1935-45 but a
security investigation in 1941 revealed that it could be solved in a few hours.
It is not known if after this discovery the device was modified in some way or
if the operating procedures were changed in order to increase security (41).
Typex
The Poles
must have learned of the British Typex cipher machine, since in 1944 they
requested 40 machines for use by their Foreign Ministry (42). The British
position was that due to production difficulties ‘it is probably impossible
to meet their requirements for the time being’ however ‘provided the
Type X machines supplied were not fitted with Plugboard and provided also we
wired for them and supplied the necessary drums, the advantages to be gained by
meeting their request would outweigh the disadvantages’…
The Russian connection
In the
period 1941-45 the Soviet codebreaking agencies were the 5th Department of the
People's Commissariat for Internal Affairs - NKVD and the 8th department of the
Intelligence Directorate of the Army General Staff - GRU.
At this time
there is no information on whether the Polish diplomatic and military
intelligence ciphers were worked on by the Soviet codebreakers. However, it is
reasonable to assume that the Soviet leadership would have been very interested
in the communications of the Poles.
Sources:
(1). Journal
of U.S. Intelligence Studies, vol. 15, no. 2: ‘England’s Poles in the Game:
WWII Intelligence Cooperation’
(2). War in
History Vol. 18, No. 1 article: ‘Penetrating Hitler's High Command:
Anglo-Polish HUMINT, 1939-1945’
(3). TICOM
report DF 187G ‘Replies by ministerialrat Fenner to questions regarding
cryptologic matters’, p11-19
(4). Cryptologia
Volume 31, Issue 3: ‘From the Archives: Polish Interwar MFA's Cipher
Compromised?’
(5). TICOM
report I-63 ‘Interrogation Report on ORR Herrmann Scherschmidt of Pers Z S,
Auswaertiges Amt’, p3
(6). UK
Archives - HW 47/2 "Polish Cyphers 1942-1945", write-up by
Jones-Williams (Berkeley St.) - TICOM report D-3 ‘The Polish Cyphers
for Diplomatic and Consular Traffic’ by Scherschmidt (1943)
(7). TICOM
report I-63 ‘Interrogation Report on ORR Herrmann Scherschmidt of Pers Z S,
Auswaertiges Amt’, TICOM report D-3 ‘The Polish Cyphers for Diplomatic and
Consular Traffic’ by Scherschmidt (1943), Cryptologia Volume 31, Issue 3: ‘From
the Archives: Polish Interwar MFA's Cipher Compromised?’ (the compromised
material was probably recovered from the archives of the Czechoslovak crypto
service)
(8). TICOM
report I-159 'Report on GAF Intelligence based on Interrogation of Hauptmann
Zetzsche', p3 (link Washington-London)
It is
reasonable to assume that these were the systems designated PLA and PLE by the
US codebreakers.
(9). Journal
of Intelligence History, Vol. 13: ‘A note on diplomatic intercepts in England
during World War II’
(10). UK
Archives - HW 53/38 ‘DSH 15 - Cryptographic Reports’
(11). UK
Archives - HW 47/2 "Polish Cyphers 1942-1945", write-up by
Jones-Williams (Berkeley St.)
(12). SRH-361
‘History of the Signal Security Agency volume two - The general cryptanalytic
problems’, chapter XI ‘Far Eastern and Central European systems’.
(13). The
relevant report ‘Polish cipher systems - January 1945’ has not been
declassified.
(14). NARA -
RG 457 - Entry 9032 - NR 3819 ‘Cryptographic codes and ciphers: Polish cipher
systems 1942-44’
(15). UK
Archives - HW 47/2 "Polish Cyphers 1942-1945", write-up by
Jones-Williams (Berkeley St.)
(16). TICOM
report I-150 ‘Report by Uffz. Heinz W. Beyreuther on the organisation of
OKH/Chi’, p3
(17). TICOM
report DF-9 ‘Captured Wehrmacht Sigint Document: Translation of Activity Report
of OKW/Chi for the Period 1st January, 1944 to 25th June, 1944’, p3
(18). TICOM
report DF-176 ‘Answers written by professor doctor Wolfgang Franz to questions
of ASA Europe’, p11
(19). TICOM
report I-118 ‘Joint reports by Reg. Rat. Dr. Hüttenhain and Sdf. Dr. Fricke,
written at CSDIC on or about 28 August 1945’, p8-9
(20). TICOM
report I-37 ‘Translation of paper written by Reg.Rat.Dr Huettenhain of OKW/Chi
on special apparatus used as aids to cryptanalysis’, p4-5, European Axis
Signals Intelligence vol. 2, p61-63, Histocrypt 2020: ‘The Auxiliary Devices of
OKW/Chi’
(21). TICOM
report I-31 ‘Detailed interrogations of Dr. Hüttenhain, formerly head of
research section of OKW/Chi, 18-21 June 1945’, p21
(22). The
Enigma Bulletin no13: ‘The decryption of Polish intelligence communications
during World War II: A view from inside the OKW/Chi’
(23). ‘Intelligence
Past’ website: ‘Major Choynacki's Ace: The solution to an old puzzle of wartime
intelligence’, UK Archives - KV 2/1329 ‘Willy PIERT / Hans Von PESCATORE’, The
Enigma Bulletin no13: ‘The decryption of Polish intelligence communications
during World War II: A view from inside the OKW/Chi’, ‘KODY WOJNY. Niemiecki
wywiad elektroniczny w latach 1907–1945 a losy polskich, sowieckich, alianckich
kodów i szyfrów’, TICOM report I-31 ‘Detailed interrogations of Dr. Hüttenhain,
formerly head of research section of OKW/Chi, 18-21 June 1945’, TICOM report I-118
‘Joint reports by Reg. Rat. Dr. Hüttenhain and Sdf. Dr. Fricke, written at
CSDIC on or about 28 August 1945’, TICOM report DF-187B ‘The cryptanalytic
successes of OKW/Chi after 1938’, CSDIC SIR 1719 - 'Notes on Leitstelle III
West Fur Frontaufklarung'
(24). UK
Archives - HW 53/38 ‘DSH 15 - Cryptographic Reports’
(25). UK
Archives - HW 47/2 "Polish Cyphers 1942-1945", write-up by
Jones-Williams (Berkeley St.)
(26). UK Archives - HW 53/36 ‘DSH 17 - Supplementary Cryptological Reports Nos. 1-9’
(27). UK
Archives - HW 40/221 ‘Poland: reports and correspondence relating to the
security of Polish communications’
(28). G40
Small’s report January 1945 (Ralph Erskine files)
(29). The
relevant report ‘Polish cipher systems - January 1945’ has not been
declassified.
(30). German
Foreign Ministry’s Political Archive - TICOM collection - Inspectorate 7/VI War
Diary - Referat 12 reports
(31).
Referat 12 reports, ‘KODY WOJNY. Niemiecki wywiad elektroniczny w latach
1907–1945’, Facebook page of Marian Zacharski, TICOM report I-180 ‘Homework by
Uffz. Keller of In 7/VI and WNV/Chi’
(32). TICOM
report I-115 ‘Further interrogation of Oberstlt. Mettig of OKH/Chi on the
German wireless security service (Funküberwachung)’, p9
(33). UK
Archives - HW 40/221 ‘Poland: reports and correspondence relating to the
security of Polish communications’
(34). UK
Archives - HW 40/222 ‘Poland: reports and correspondence relating to the
security of Polish communications’
(35). UK
Archives - HW 40/221 ‘Poland: reports and correspondence relating to the
security of Polish communications’ and HW 40/244 ‘Polish: evidence that the OKW
(High Command of the German Armed Forces) was reading traffic passing between
London and the Polish underground’
(36). UK
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