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[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 <[maarten--vrijheid--net]> wrote:
> Hi, > > 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). M&F