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Analog of the Japanese Type B Cipher Machine (codenamed Purple) built by the U.S. Army Signal Intelligence Service Purple analog in use. In the history of cryptography, the "System 97 Typewriter for European Characters" (九七式欧文印字機 kyūnana-shiki ōbun injiki) or "Type B Cipher Machine", codenamed Purple by the United States, was an encryption machine used by the Japanese Foreign ...
For eighteen months, she worked with other SIS codebreakers to analyze the encryption system used in the Japanese Type B Cipher Machine, code named Purple by the SIS [3]: p. 8 She played a key role in cracking the cipher, [4] discovering cyclical behavior in the code on September 20, 1940.
The most important diplomatic cipher used by the Foreign Office was Purple. The Japanese military (army) effectively controlled Japanese foreign policy, and told the Foreign Office little. But decrypted Purple traffic was valuable militarily, particularly reports from Nazi Germany by Japanese diplomats and military and naval attachés.
In the mid-1930s, they solved the first Japanese machine for encipherment of diplomatic communications, known to the Americans as RED. In 1939–40, Rowlett led the SIS effort that solved a more sophisticated Japanese diplomatic machine cipher, codenamed PURPLE by the U.S. Once, when asked what his greatest contribution to that effort had been ...
PURPLE was an enticing, but quite tactically limited, window into Japanese planning and policy because of the peculiar nature of Japanese policy making prior to the War (see above). Early on, a better tactical window was the Japanese Fleet Code (an encoded cypher), called JN-25 by U.S. Navy cryptanalysts.
The Japanese used three 7-layer switches for each stage of the cipher; Rosen used four 6-layer switches per stage. Cryptographically, there was no difference. Rosen built a replica of PURPLE which turned out (when a machine was found years later) to use stepping switches similar to those in common use at that time in the U.S. This machine was ...
Japanese Navy ORANGE cryptographic device captured by US Navy. In the history of cryptography, 91-shiki ōbun injiki (九一式欧文印字機, "System 91 Typewriter for European Characters") or Angōki Taipu-A (暗号機 タイプA, "Type A Cipher Machine"), codenamed Red by the United States, was a diplomatic cryptographic machine used by the Japanese Foreign Office before and during World ...
A similar break into the most secure Japanese diplomatic cipher, designated Purple by the US Army Signals Intelligence Service, started before the US entered the war. Product from this source was called Magic. On the other side, German code breaking in World War II achieved some notable successes cracking British naval and other ciphers.