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/* This code illustrates a sample implementation
* of the Arcfour algorithm
* Copyright (c) April 29, 1997 Kalle Kaukonen.
* All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that this copyright
* notice and disclaimer are retained.
*
* THIS SOFTWARE IS PROVIDED BY KALLE KAUKONEN AND CONTRIBUTORS ``AS
* IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL KALLE
* KAUKONEN OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "mupdf/fitz.h"
void
fz_arc4_init(fz_arc4 *arc4, const unsigned char *key, size_t keylen)
{
unsigned int t, u;
size_t keyindex;
unsigned int stateindex;
unsigned char *state;
unsigned int counter;
state = arc4->state;
arc4->x = 0;
arc4->y = 0;
for (counter = 0; counter < 256; counter++)
{
state[counter] = counter;
}
keyindex = 0;
stateindex = 0;
for (counter = 0; counter < 256; counter++)
{
t = state[counter];
stateindex = (stateindex + key[keyindex] + t) & 0xff;
u = state[stateindex];
state[stateindex] = t;
state[counter] = u;
if (++keyindex >= keylen)
{
keyindex = 0;
}
}
}
static unsigned char
fz_arc4_next(fz_arc4 *arc4)
{
unsigned int x;
unsigned int y;
unsigned int sx, sy;
unsigned char *state;
state = arc4->state;
x = (arc4->x + 1) & 0xff;
sx = state[x];
y = (sx + arc4->y) & 0xff;
sy = state[y];
arc4->x = x;
arc4->y = y;
state[y] = sx;
state[x] = sy;
return state[(sx + sy) & 0xff];
}
void
fz_arc4_encrypt(fz_arc4 *arc4, unsigned char *dest, const unsigned char *src, size_t len)
{
size_t i;
for (i = 0; i < len; i++)
{
unsigned char x;
x = fz_arc4_next(arc4);
dest[i] = src[i] ^ x;
}
}
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