In WWII the Finnish codebreakers solved the codes and ciphers of several countries. In the diplomatic field their greatest success was achieved against the State Department’s M-138-A strip cipher. One of the people who played a key role in this operation was the cryptanalyst Karl Erik Henriksson.
However there was another person working for Finnish signals intelligence named Henriksson. This was the radio operator Toivo Erik Henriksson. It seems that I mixed them up.
Thus the passage ‘Other important people were Pentti Aalto (effective head of the US section) and the experts on the M-138 strip cipher Toivo Erik Henriksson and Kalevi Loimaranta’, in The Finnish cryptologic service in WWII turns into:
‘Other important people were Pentti Aalto (effective head of the US section) and the experts on the M-138 strip cipher Karl Erik Henriksson and Kalevi Loimaranta’
I have to thank Craig McKay for pointing out this mistake and my friends in Finland for clarifying that Toivo was a radio operator.