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/* arc4.c
*
* Copyright (C) 2006-2011 Sawtooth Consulting Ltd.
*
* This file is part of CyaSSL.
*
* CyaSSL is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* CyaSSL is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#include "arc4.h"
void Arc4SetKey(Arc4* arc4, const byte* key, word32 length)
{
word32 i;
word32 keyIndex = 0, stateIndex = 0;
arc4->x = 1;
arc4->y = 0;
for (i = 0; i < ARC4_STATE_SIZE; i++)
arc4->state[i] = i;
for (i = 0; i < ARC4_STATE_SIZE; i++) {
word32 a = arc4->state[i];
stateIndex += key[keyIndex] + a;
stateIndex &= 0xFF;
arc4->state[i] = arc4->state[stateIndex];
arc4->state[stateIndex] = a;
if (++keyIndex >= length)
keyIndex = 0;
}
}
static INLINE word32 MakeByte(word32* x, word32* y, byte* s)
{
word32 a = s[*x], b;
*y = (*y+a) & 0xff;
b = s[*y];
s[*x] = b;
s[*y] = a;
*x = (*x+1) & 0xff;
return s[(a+b) & 0xff];
}
void Arc4Process(Arc4* arc4, byte* out, const byte* in, word32 length)
{
word32 x = arc4->x;
word32 y = arc4->y;
while(length--)
*out++ = *in++ ^ MakeByte(&x, &y, arc4->state);
arc4->x = x;
arc4->y = y;
}
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