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

[Mark K3MSB]

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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