American Cryptology during the Cold War, 1945-1989, by Thomas R. Johnson: documents 1, 2, 3, 4, 5, and 6. In response to a declassification request by the National Security Archive, the secretive National Security Agency has declassified large portions of a four-part "top-secret Umbra" study, American Cryptology during the Cold War. Despite major redactions, this history discloses much new information...