Clive D.W. Feather wrote:
>
> In article <[EMAIL PROTECTED]>, MCKAY john
> <[EMAIL PROTECTED]> writes
> >Another curiosity of the Mark I's instruction set was a sideways
> >add ('population count'), also specified by Turing. I've always
> >assumed that the two instructions could be useful for cryptography -
>
> Think about how the Bombes worked. You injected signal into one line,
> and wanted to know when it didn't come back on all of the other 25. A
> software implementation of this could use a population count to
> advantage.
I don't see how ... this is a known bit pattern, rather than a
particular bit count. A simple XOR and test for zero will do this
efficiently.
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
