Re: Computing Rijndael's SBox?
From: Björn Fay (mail_at_bfay.de)
Date: 08/30/05
 Next message: tomstdenis_at_gmail.com: "Re: Resecured Algorithm?"
 Previous message: Håvard Raddum: "Re: computing modul"
 In reply to: cobussteyn_at_absamail.co.za: "Computing Rijndael's SBox?"
 Next in thread: contini_at_matmail.com: "Re: Computing Rijndael's SBox?"
 Reply: contini_at_matmail.com: "Re: Computing Rijndael's SBox?"
 Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] [ attachment ]
Date: Tue, 30 Aug 2005 12:04:25 +0200
cobussteyn@absamail.co.za wrote:
> I'm a newbie when it comes to cryptography and currently I'm hooked on
> Rijndael. I know most of the implementations of it have the Sbox
> hardcoded into the app for speed gain, but I would like to compute
> that sbox myself.
>
> You probably know it is defined by the finite field mapping in GF(2^8)
> onto its inverse, and then it is transformed by a certain matrix (i
> have that one) and then 0x63 is added.
>
> Can someone help me to compute that first mapping of GF(2^8) onto its
> inverse? How do you compute the inverse?
>
> Thanx !
You have to use the Extended Euclidean Algorithm an explanation can be found in books for discrete mthematics or in wikipedia:
http://en.wikipedia.org/wiki/Extended_Euclidean_algorithm
 Next message: tomstdenis_at_gmail.com: "Re: Resecured Algorithm?"
 Previous message: Håvard Raddum: "Re: computing modul"
 In reply to: cobussteyn_at_absamail.co.za: "Computing Rijndael's SBox?"
 Next in thread: contini_at_matmail.com: "Re: Computing Rijndael's SBox?"
 Reply: contini_at_matmail.com: "Re: Computing Rijndael's SBox?"
 Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] [ attachment ]
Relevant Pages
