http://chris-intel-corner.blogspot.gr/2014/07/compromise-of-soviet-codes-in-... Overview of Soviet cryptosystems The secretive Soviet state used various cryptosystems in order to secure its communications from outsiders. The task of preparing and evaluating cipher procedures was handled by two main Soviet organizations, the NKVD’s 5th Department and the Army’s 8th department of the main intelligence directorate GRU. In the 1920’s simple substitution systems were used and these were solved by ...