Signals Intercepts & Cryptography

Canadians’ interception and decryption of enemies’ (and in some instances, neutrals’ or allies’) signals communications during the Second World War remained the country’s “best-kept secret” for decades. Canadian military intelligence officers forwarded specific decrypts of interest to the BSC. They also alerted counterparts in New York when British and American personnel committed wireless security blunders. 

CDBS00220 is evidence of the limits of cooperation between allies. Canadians sought FBI advice on the security of electromechanical communications through BSC intermediaries but were rebuffed by J. Edgar Hoover.