On Wed, 23 May 2007 18:13:37 -0400, Tom Del Rosso wrote:

"Stephen J. Rush" wrote in message
news

You haven't Googled it? [.....]

[....]. Then there was the Allied SIGABA, which, as far as anyone
is willing to admit, was never broken. It used rotors to control the
motion of other rotors.

I've googled, but SIGABA never came up. Thanks.

I found SIGABA at wikipedia, but of Purple, I can find only the fact that
it was broken before December 1941, so the message instructing the embassy
in Washington to break off negotiations was intercepted. That was an
ominous sign, but no Purple message ever mentioned the Pearl Harbor
strike, because the Japanese military planners didn't trust the Foreign
Office.

I can't find any hint of how the American cryptanalysts were able to break
Purple and the more important Japanese naval code with only cyphertext to
work with. Remember, Bletchley Park had Enigma machines.