[REBOL] Re: subtracting binaries
From: mauro:fontana:speedautomazione:it at: 2-Apr-2004 10:16
On Thu, 01 Apr 2004 16:55:27 +0200, Maarten Koopmans
> As anybody (efficiently) tackled suntracting two binary! values. I want
> to compute the difference between two 160 bit SHA1 keys, with the
> outcome a new binary. And I also need addition which sould be circular
> in 160bit space. E.g 2^160 + 1 = 1
> Before re-inventing yet another wheel I'd thought I'd ask to see if
> anybody has already written this.
If you are trying to build a Galois Field the best way is probably
building an array with the exponential form so that you can do math on
exponents only (you do the modulus on the exponent).