Figure 1: Fragment of an actual Purple Machine
In June of 1938, the Japanese introduced a new code. It was called 97-shiki-obun In-ji-ki ("System 97 Printing Machine for European Characters") or Angooki Taipu B ("Type B Cipher Machine"). The US codenamed it Purple, after the binder that they used to hold materials from the system.|
Purple was completely different from all other previous codes used by the Japanese. Some sources claim that Purple was a complicated adaptation of the German Enigma cipher machine, but it appears that it was a Japanese development.
This site contains a description of the workings of Purple, some sample code from the December 6th telegram from Tokyo to Washington cutting off diplomatic relations with the US, a discussion of the history of the US decryption of the Purple cipher, the usage of the Purple cipher by the US to defeat Japan in WWII, and last some links to other sites with relevant information. All of this information can be accessed via the menu on the left.