Re: Questions regarding using ciphers as stream ciphers

Ben Laurie (ben@algroup.co.uk)
Tue, 27 Apr 1999 10:01:53 +0100

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Wall, Kevin wrote:
> However, when I pointed out Bruce Schneier's above paragraph to my
> supervisor (to justify additional time for my colleague to fix the
> problem -- see below), I met with some resistance from my supervisor.
> I think that part of the problem was not knowing how exactly to
> correctly interpret the "+" and "-" operations mentioned above.
> (We presume that the "+" is bitwise XOR, and "-" is bitwise
> subtraction, but we aren't really sure.) But the biggest problem
> is that my supervisor isn't convinced veracuty of the statement:

"+" is "the operation you use to combine the plaintext and the output of
the cipher", and "-" is the inverse operation. Commonly they are both
XOR, but they don't have to be.

Cheers,

Ben.

--
http://www.apache-ssl.org/ben.html
"My grandfather once told me that there are two kinds of people: those
who work and those who take the credit. He told me to try to be in the
first group; there was less competition there."
     - Indira Gandhi

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