Bill Robinson has penned a nice essay Marking 70 years of eavesdropping in Canada. The essay gives the background of Canada’s signals intelligence unit, the Communications Security Establishment (CSE) which just marked its 70th anniversary (on Sept. 1st.)
The original unit was the peacetime version of the Joint Discrimination Unit called the CBNRC (Communications Branch of the National Research Council). I can’t help wondering what was meant by “discrimination”?
Unable to read the Soviets’ most secret messages, the UKUSA allies resorted to plain-language (unencrypted) communications and traffic analysis, the study of the external features of messages such as sender, recipient, length, date and time of transmission—what today we call metadata. By compiling, sifting, and fusing a myriad of apparently unimportant facts from the huge volume of low-level Soviet civilian and military communications, it was possible to learn a great deal about the USSR’s armed forces, the Soviet economy, and other developments behind the Iron Curtain without breaking Soviet codes. Plain language and traffic analysis remained key sources of intelligence on the Soviet Bloc for much of the Cold War.
Robinson is particularly interesting on “The birth of metadata collection” as the Soviets frustrated developed encryption that couldn’t be broken.