Kyrre Aalerud wrote:
> Does anyone have any examples on fast 512 bit multiplication ?
> I'm talking about 512bit x 512bit.
>
> Is there any PIC's that have a MULT operation easing this ?
>
>     KreAture


I think there is no much to speed up the usual

shift
if carry bit then do a 64 bytes ADD
decrement 512 loop counter
do it again.

The worst case of all 512+512 bits ON, will take a total of
1024 shifts + 32768 adds, generating a 1023 bits number.

Gross numbers on an AVR (with enough internal RAM), would take around 80k+
instructions (also clock cycles), if running at 8MHz, would take aprox 10ms
to complete the multiplication.  If thinking about descrambling some
encription code, it will do around 100 calculations per second, less than 9
million calculations a day.  Considering the permutarion of 512 bits
encription, it can take almost 40 years to complete the whole range... :)

Wagner.

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