[ARC5] FW: How the U.S. Cracked Japan's 'Purple Encryption Machine' at the Dawn of World War II

[Joe Connor]

Fascinating topic. In retrospect, it may be puzzling that our intelligence experts did not see the Pearl Harbor attack coming, but it's even more amazing that the Japanese never figured out that the U.S. Navy had broken their JN-25 code.

                           Joe Connor 

    On Tuesday, December 6, 2016 9:31 AM, Mark K3MSB <mark.k3msb at gmail.com> wrote:
 
 

 Hi Andy
“The U.S. ceased and broke a multitude of Japanese secret messages, even some containing the plans for the attack on Pearl Harbor which could have been used to prepare.”
No they didn’t contain the plans.   Purple was primarily a diplomatic cipher,  while the Imperial Japanese Navy used JN-25.  JN-25 was largely unbroken at the time of Pearl Harbor, and as I recall they changed the JN-25 variant a few days beforehand.
We did crack Purple, but it never contained “plans for the attack on Pearl Harbor”.    At most it gave a strong indication that something was going to happen on that day,  but unfortunately nobody seriously thought it would be the Hawaiian Islands.
Could Kimmel have done things differently with the Purple based information he had and thereby significantly mitigate Pearl Harbor?   My opinion is yes he could have,  but he couldn’t have known “the plans” from Purple or JN-25 intercepts.
As a side comment,  did any of you see “Pearl Harbor – The Truth” on Sunday night on the History Channel?   I was not impressed at all with the program.
73 Mark K3MSB


On Dec 6, 2016 2:07 AM, "Andy" <w5acm at swbell.net> wrote:

In case you have not seen this item...
73 de Andy W5ACM

-----Original Message-----
From: Charlie
Sent: Monday, December 05, 2016 10:19 AM
Subject: How the U.S. Cracked Japan's 'Purple Encryption Machine' at the
Dawn of World War II

However, it did not save Pearl Harbor due to no method to put the
information to use.
The US has all the parts of the information but no system to put all the
parts together.

http://io9.gizmodo.com/how- the-u-s-cracked-japans-purple- encryption-machine-
458385664



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