the US State Department used several cryptosystems in order to protect its
radio communications from the Axis powers. For low level messages the
unenciphered Gray and Brown codebooks were used. For important
messages four different codebooks (A1,
B1, C1, D1) enciphered with substitution tables were available.
solution of State Department cryptosystems
signal intelligence service worked mostly on Soviet military and NKVD
cryptosystems however they did have a small diplomatic section located in Mikkeli. This department had
about 38 analysts, with the majority working on US codes.
Head of the
department was Mary Grashorn. Other important people were Pentti Aalto
(effective head of the US section) and the experts on the M-138 strip
Erik Henriksson and Kalevi Loimaranta.
wartime success was the solution of the State Department’s M-138-A cipher. The
solution of this high level system gave them access to important diplomatic
messages from US embassies in Europe and around the world.
1944 Finland signed an armistice with the Soviet Union. The people in charge of
the Finnish signal intelligence service anticipated this move and fearing a
Soviet takeover of the country had taken measures to relocate the radio service
to Sweden. This operation was called Stella Polaris (Polar Star).
September roughly 700 people, comprising members of the intelligence services
and their families were transported by ship to Sweden. The Finns had come to an
agreement with the Swedish intelligence service that their people would be
allowed to stay and in return the Swedes would get the Finnish crypto archives
and their radio equipment. At the same time colonel Hallamaa, head of the
signals intelligence service, gathered funds for the Stella Polaris group by
selling the solved codes in the Finnish archives to the Americans, British and
Polaris operation was dependent on secrecy. However the open market for Soviet
codes made the Swedish government uneasy. In the end most of the Finnish
personnel chose to return to Finland, since the feared Soviet takeover did not
1944 colonel Hallamaa met
with L. Randolph Higgs, an official of the US embassy in Sweden and told him
about their successes with US diplomatic codes and ciphers.
information was summarized in a report prepared by Higgs, dated 30 September
can be found in the US National Archives - collection RG 84 ‘Records of the
Foreign Service Posts of the Department of State’ - ‘US Legation/Embassy
Stockholm, Sweden’ - ‘Top Secret General Records File: 1944’.
with colonel Hallamaa on September 29 and the OSS officials Tikander and Cole
were also present during their discussion.
stated that he was an administrator, not a cryptanalyst and about 10-12 of his men
worked on US diplomatic codes.
His unit had
solved the US codes Gray, Brown, M-138-A strip cipher and enciphered codebooks
(probably the A1, B1, C1).
level M-138-A system had been solved mostly by taking advantage of operator
mistakes such as sending strip cipher information on other systems that had already
been broken or sending the same message in different strips one of which had
cipher was considered a strong encryption system and had been adopted by the
Finns for some of their traffic.
diplomatic messages from the US embassies in Switzerland, Sweden and Finland
were read by the Finnish codebreakers.
Regarding Bern, Switzerland most of the
messages dealt with intelligence matters:
‘Replying to my request for information
regarding the contents of the messages from our Legation in Bern to the
Department, Col. Hallamaa said the great bulk of them were intelligence
messages dealing with conditions in Germany, France, Italy and the Balkans. He
spoke in complimentary terms about ‘Harrison’s’ information service’.
Helsinki, Finland Hallamaa stated that thanks to the decoded diplomatic traffic
they were always informed of current US policy initiatives:
‘Col. Hallamaa said that they always knew
before McClintock arrived at the Foreign Office what he was coming to talk about’.
revealed a lot of confidential information to the Americans and volunteered to
have some of his experts interviewed.
The interview was conducted on friendly
terms with Higgs stating; ‘Col. Hallamaa
was most pleasant and seemed to be entirely frank and open regarding the