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again sorta not -
07-22-2010, 03:56 AM
The IJN - Japanese navy used more than one code and the diplomatic corp used a entirely different code.
JN-25 was the name the US encryption experts gave the IJN most secure and highest code. This code was an enciphered code.
It was frequently revised during its lifetime, and each new version required a more or less fresh cryptanalytic start.
In particular, JN-25 was significantly changed immediately before the Pearl Harbor attack on 7 December 1941. It was that edition of the JN-25 system which was sufficiently broken by late May 1942 to provide the forewarning which led to the U.S. victory at the Battle of Midway.
No the Japanese JN-25 or any other code was 'broken' prior to Pearl Harbor.
period
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