44 lines
1.1 KiB
C
44 lines
1.1 KiB
C
/* gf256mul.c */
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/*
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This file is part of the AVR-Crypto-Lib.
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Copyright (C) 2006-2015 Daniel Otte (bg@nerilex.org)
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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/**
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* \file gf256mul.c
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* \email bg@nerilex.org
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* \author Daniel Otte
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* \date 2009-01-13
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* \license GPLv3 or later
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*
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*/
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#include <stdint.h>
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#include "gf256mul.h"
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uint8_t gf256mul(uint8_t a, uint8_t b, uint8_t reducer){
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uint8_t i;
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uint8_t p=0,t;
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for(i=0; i<8; ++i){
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if(b&1)
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p ^= a;
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t=a&0x80;
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a<<=1;
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if(t)
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a ^= reducer;
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b>>=1;
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}
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return p;
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}
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