63 lines
1.6 KiB
C
63 lines
1.6 KiB
C
/* arcfour.c */
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/*
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This file is part of the Crypto-avr-lib/microcrypt-lib.
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Copyright (C) 2008 Daniel Otte (daniel.otte@rub.de)
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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: arcfour.c
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* Author: Daniel Otte
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* email: daniel.otte@rub.de
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* Date: 2006-06-07
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* License: GPLv3 or later
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* Description: Implementation of the ARCFOUR (RC4 compatible) stream cipher algorithm.
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*
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*/
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#include <stdint.h>
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#include "arcfour.h"
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/*
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* length is length of key in bytes!
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*/
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void arcfour_init(arcfour_ctx_t *c, uint8_t *key, uint8_t length){
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uint8_t t;
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unsigned x,y=0;
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for(x=0; x<= 255; ++x)
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c->s[x]=x;
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for(x=0; x<= 255; ++x){
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y += c->s[x] + key[x % length];
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y &= 0xff;
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t = c->s[y];
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c->s[y] = c->s[x];
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c->s[x] = t;
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};
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c->i = c->j = 0;
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}
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uint8_t arcfour_gen(arcfour_ctx_t *c){
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uint8_t t;
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c->i++;
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c->j += c->s[c->i];
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t = c->s[c->j];
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c->s[c->j] = c->s[c->i];
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c->s[c->i] = t;
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return c->s[(c->s[c->j] + c->s[c->i]) & 0xff];
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}
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