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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 ...
The U.S. called this the "Purple" code, because they kept intercepted traffic in purple binders. Although the Japanese purchased the Enigma machine, they chose to base their cipher machine on a different technology, using a stepping switch rather than several rotors. [20]
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 PURPLE machine itself was first used by Japan in 1940. U.S. and British cryptographers had broken some PURPLE traffic well before the attack on Pearl Harbor. However, the PURPLE machines were used only by the Foreign Office to carry diplomatic traffic to its embassies. The Japanese Navy used a completely different crypto-system, known as JN-25.
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 ...
A cipher machine developed for Japanese naval attaché ciphers, similar to JADE. It was not used extensively, [5] [6] but Vice Admiral Katsuo Abe, a Japanese representative to the Axis Tripartite Military Commission, passed considerable information about German deployments in CORAL, intelligence "essential for Allied military decision making in the European Theater."
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 ...
With the duplicate machines and an understanding of PURPLE, SIS could decrypt increasing amounts of Japanese traffic. One such intercept was the message to the Japanese Embassy in Washington, D.C., ordering an end (on December 7, 1941) to negotiations with the US.