Protecting secrets: British diplomatic cipher machines in the early Cold War, 1945-1970

This article examines how effectively Britain secured its diplomatic communications against hostile decryption during the early Cold War. It shows that between 1945 and 1970 the Foreign Office and the Commonwealth Relations Office introduced and operated four advanced cipher machines, Typex, Rockex, Noreen and Alvis, which produced very strong ciphers. However, Britain did suffer physical compromises of Rockex through Soviet espionage and an attack on the British embassy in Beijing. Rockex was also vulnerable to technical surveillance of its acoustic and Tempest emissions, and the Soviets exploited this to read the encrypted communications of the British embassy in Moscow.