Typex was the name for the principal encryption device, or cipher machine, used by the military, intelligence, and diplomatic services of the British Empire during World War II. In the 1920s, the British were still using book cipher systems, and became aware of the need to modernize using new cipher machinery. They initially planned to use the Enigma system, but instead settled on an improved Enigma machine known as "Type X." The Typex system remained in use among British forces throughout the war.
In 1926, the British government formed an interdepartmental committee to study technology as a means of finding a replacement for the laborious system of encryption by hand. For the purposes of evaluation, the government purchased two Enigma machines, but in January 1935, the committee advised the Royal Ministry to acquire three of the "Type X" machines, which represented an improved Enigma design. Satisfied with the machine, Whitehall commissioned the Creed & Company to manufacture Type X machines to specification.
As war broke out in September 1939, the British War Office and Air Ministry had fully adopted the Typex system, although the Royal Navy would continue to perform encryption by hand until 1943. Unlike the Germans, who encrypted nearly every official message on their Enigma machines, the British used their Typex system sparingly. This may have given them an unexpected advantage, because the Germans' proliferation of enciphered messages gave the British plenty of material to study. By contrast, the Germans made no significant attempt to crack the Typex ciphers, even though they captured several of the machines at Dunkirk and in North Africa.
Britain undertook the joint development of a Combined Cipher Machine with the Americans, who developed their own Sigaba system. In 1943, the Royal Navy began using the Combined Cipher Machine. Meanwhile, the rest of the British forces continued to use Typex, though British units in the China-Burma-India theatre adopted Sigaba, while some American units adopted Typex. After the war, many Typex machines remained in use among English-speaking nations for several decades until finally, in 1973, New Zealand became the last nation to set aside its Typex system.
█ FURTHER READING:
Freedman, Maurice. Unravelling Enigma: Winning the Code War at Station X. Barnsley, South Yorkshire, England: Leo Cooper, 2000.
Kozaczuk, Wladyslaw. Enigma: How the German Machine Cipher Was Broken, and How It Was Read by the Allies in World War Two. Frederick, MD: University Publications of America, 1984.
Melton, H. Keith. The Ultimate Spy Book. New York: DK Publishing, 1996.
Miller, A. Ray. The Cryptographic Mathematics of Enigma. Ft. Meade, MD: National Security Agency, 2001.
Polmar, Norman, and Thomas B. Allen. Spy Book: The Encyclopedia of Espionage. New York: Random House, 1998.
COMINT (Communications Intelligence)
SIGINT (Signals intelligence)
Special Relationship: Technology Sharing Between the Intelligence Agencies of the United States and United Kingdom