The good
news
The war diary
of the German Army’s signal intelligence agency Inspectorate 7/VI and the
reports of the cryptanalytic centre in the East Horchleitstelle Ost (later
named Leitstelle der Nachrichtenaufklärung)
are available for the period 1941-43. Also summaries on the solution of Soviet
codes are available for the period October 1944-March 1945.
The bad news
I haven’t been able to find the reports of Horchleitstelle Ost for the second half of 1941 and for
the period February- September 1944.
The
unexpected
According to
a recently declassified TICOM report the Germans were able to read the first
version of the Soviet diplomatic one time pad code in the 1930’s and the codes
of the Comintern. In the first case their success was due to the fact that the
system was not true one time pad in that one additive page was assigned to each
message. If the values were not enough to encipher the entire message then they
were reused.
In the case
of the Comintern it seems that the main system used by Communist Parties around
the world was a numerical code used together with a letter to number
substitution table. The table was used as a ‘key’ generator for additive
sequences used to encipher the coded message. A common book would be used for
this purpose and the user would identify through the indicator the page and
line that the sequence would start from. In one such case the Germans solved the ‘encipherment sequence of about five million
digits’ and identified the five books used as cipher.
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