At the end of
WWII the Western Allies were able to arrest and interrogate many German
codebreakers. In addition the archives (or parts of them) of several German
signal intelligence agencies fell into their hands.
This
information is contained in the numerous TICOM (Target Intelligence Committee)
reports that I have uploaded
to the internet.
However is
the information from the TICOM reports accurate? Or were the Germans either
exaggerating or downplaying their successes?
The validity
of some of the statements made in TICOM reports can be assessed by checking the
archives of the agencies mentioned in them.
If a German
Naval codebreaker said that they broke a specific code in a specific time
period then the archives of the B-Dienst would be expected to confirm this
information. Same thing for the codebreakers of other agencies of the Third
Reich.
However what
happens when the relevant archives are either not available or have parts
missing?
Then it
becomes difficult to judge the truthfulness of some of the statements made by
the Germans.
Three
different agencies worked on the US diplomatic M-138-A
strip cipher. The German High Command’s deciphering department – OKW/Chi, the Foreign Ministry’s
deciphering deparment Pers Z and the
Air Ministry’s Research Department - Reichsluftfahrtministerium Forschungsamt.
Since many
officials from these organizations were arrested and interrogated by the Allies
one would expect that we would have a clear picture of their success against
the strip cipher. Yet this is not true. On the contrary, there many gaps in our
knowledge of their efforts and successes against this system.
At the Forschungsamt
some work was done on the strip but apart from the fact that they solved some
traffic we don’t know any more details.
At OKW/Chi an
entire team worked on the strip, led by the mathematician Wolfgang
Franz. The information given by
Franz who was interrogated in 1949 is limited. In his report DF-176 he said in
pages 6-9:
‘Especially laborious and difficult
work was connected with an American system which, judging by all indications was
of great importance. This was the strip cipher system of the American
diplomatic service which was subsequently solved in part.’
This system
was so important that more workers were hired to work on it.
‘On the basis of gradual successes
with the Am10 –that was the designation of the strip cipher system- Dr
Huettenhain succeeded in securing the appointment of assistants despite
vigorous opposition on the part of the administrative office and the
philological sections.’
But Franz
doesn’t give any details about the links that were solved or the information
gained. He simply said:
‘All told, some 28 circuits were solved at
the Bureau under my guidance, likewise six numerical keys-some of them only in
part.’
He also
downplayed his success:
‘To be sure, only a few solutions came
in good time; in most cases there were lags of one to one and a half years.
Since the essential principles were recognized too late and necessary personnel
and aids were not available at the time.’
Would the
Germans invest more manpower and even build cryptanalytic equipment in order to
solve traffic that was years old? It does seem strange…
Even stranger
is what Franz says in page 11:
‘At the end
of the war I was on an official journey to retrieve some material which had
been lent to the Foreign Office and
was overtaken by American troops in Northern Germany.’
Hmm what kind
of material did Dr Franz want to retrieve? Maybe it was relevant to the strip
solution, maybe not, we’ll probably never know.
Erich Huettenhain, who was the chief cryptanalyst of
OKW/Chi also had a leaky memory when it came to the strip cipher. In TICOM I-2 ‘Interrogation of Dr. Huettenhain
and Dr. Fricke at Flenshurg,21 May 1945’, he said:
‘Q. What work was done on British and
American codes and ciphers?
A. Diplomatic - most of the American strip cipher was read,
strip cipher was used by the military as well as by the diplomatic.’
In TICOM
I-145 ‘Report on the US strip system by Reg Rat Dr Huettenhain’ he changed his
mind:
‘Only a
little of the material received could be read at once. Generally it was back traffic that was read.
As, however, the different sets of strips were used at different times by other
stations, it was possible, in
isolated cases, to read one or the other of the special traffics currently. We
are of opinion that of the total material received, at the most one fifth was read, inclusive of back
traffic. None was read after the
beginning of 1944.’
In TICOM
I-145 ‘Report on the US strip system by Reg Rat Dr Huettenhain’ he said:
‘On the basis of the cypher data received, the
traffic on the one key could be read. In the course of time, as a result
of compromises or partial compromises of the traffic on this key, or with the
aid of other readable cypher traffic, other sets of strips were discovered by cryptanalysis. can no longer
state how many different sets of strips were reconstructed; probably 10 to 20.’
But in an unpublished manuscript written in 1970 he said:
‘Auf diese
Weise wurden von 1942 bis September 1944 insgesamt 22 verschiedene Linien und
alle cq-Sprüche mitgelesen’
Translation: In this way, were read by 1942 to September 1944, a total
of 22 different links and all cq
(call to quarters) messages.
‘Government codes and ciphers 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 USA, Poland and Turkey.’
‘A number of complicated recipherings, principally American (USA)
and Polish, have been broken.’
This must have been a reference to the US strip cipher, in which case
Huettenhain’s statements about limited success ring false.
Apart from
the Forschungsamt and OKW/Chi the Pers Z department worked on the strip cipher.
The Foreign
Ministry’s deciphering deparment Pers Z devoted significant resources against
the US diplomatic strip cipher. A team of mathematicians, led by Professor Hans Rohrbach made
extensive use of IBM/Hollerith punch card equipment in their efforts to solve
the alphabet strips. Rohrbach admitted to solving the circular set 0-2 but
what of other sets?
Rohrbach says
that systematic work on the solution of the cipher began in November 1942 but
in Huettenhain’s files there is a report that says that Pers Z was working on a
US diplomatic system since 1939-40…
Rohrbach also
says that:
‘As to technical means, we had at our
disposal in 1942-44 a good selection of Hollerith machines. We frequently used
probability and statistics theory mainly in order to decide whether or not an
observed phenomenon was caused by chance or was, in fact, due to some
encipherment.’
But another
Pers Z cryptanalyst, Dr Schultz, said in
TICOM report I-22 ‘Interrogation of German Cryptographers of Pers Z S
Department of the Auswaertiges Amt’, p16 that the greatest achievement of the
mathematical research section was the solution of the 0-2 strips entirely by
hand.
So what can we conclude from all these conflicting statements? Obviously we do
not know the full story of the German success with the State Department’s strip
cipher!
Acknowledgements: I have to thank Michael van der Muelen for sharing the
TICOM report DF-176 ’Answers written by professor doctor Wolfgang Franz to
questions of ASA Europe’
