Code 97

The code 97 or code PURPLE (“code CRIMSON”) one of the methods of coding was used by the Japanese during the Second world war.

The 97 comes from its original Japanese name: 97-shiki O-bun In-ji-ki (九七式欧文印字機) which means “typewriter roughly of type 97 for the European characters” or Angooki Taipu B (暗号機 B 型), that is to say “machine of coding of the type B”. The machine took in entry European characters and produced a quantified exit

The 97 fact allusion to year 2597 of the Japanese Calendar, are 1937. Less known than Enigma, the machine used to apply this coding had similarities with Enigma from the presence of several rotors and a table of connections. It was especially intended for a diplomatic use for the connections between Germany and Japan. The first uses started right before the war.

Cryptanalyse

“Machine PURPLE” was an improvement of a preceding named version “Machine M” as well as “Machine RED”. These codings had been developed by the captain of the Japanese navy Risaburo Ito. Under cover of code name “Magic”, the operations of deciphering occupied the Americans as of 1938. A good part of the Cryptanalyse had been carried out before even the entry in war of the United States. The Japanese (just like Germans) thought that their coding was impossible to break but William Friedman and Frank Rowlett of the US Army Signals Intelligence Service succeeded in discovering weaknesses, with in particular the weak presence of key who made coding vulnerable.

The December 7th 1941, the stop of the diplomatic relations by the Japanese, little before the Attack on Pearl Harbor, was already known cipher offices before even as the Japanese ambassador announces it itself. This episode will be at the origin of a polemic post-war period as for the responsibilities related to the disaster for Pearl Harbor.

External bonds

http://home.att.net/~mleary/pennl7.htm

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