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/*
* Copyright (c) 2004 Kungliga Tekniska Högskolan
* (Royal Institute of Technology, Stockholm, Sweden).
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE 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 THE INSTITUTE 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.
*/
/* implemented from description in draft-kaukonen-cipher-arcfour-03.txt */
#ifdef HAVE_CONFIG_H
#include "config.h"
RCSID("$Id: rc4.c,v 1.1 2004/03/25 16:40:59 lha Exp $");
#endif
#include <rc4.h>
#define SWAP(k,x,y) \
{ unsigned int _t; \
_t = k->state[x]; \
k->state[x] = k->state[y]; \
k->state[y] = _t; \
}
void
RC4_set_key(RC4_KEY *key, const int len, unsigned char *data)
{
int i, j;
for (i = 0; i < 256; i++)
key->state[i] = i;
for (i = 0, j = 0; i < 256; i++) {
j = (j + key->state[i] + data[i % len]) % 256;
SWAP(key, i, j);
}
key->x = key->y = 0;
}
void
RC4(RC4_KEY *key, const int len, const unsigned char *in, unsigned char *out)
{
int i, t;
unsigned x, y;
x = key->x;
y = key->y;
for (i = 0; i < len; i++) {
x = (x + 1) % 256;
y = (y + key->state[x]) % 256;
SWAP(key, x, y);
t = (key->state[x] + key->state[y]) % 256;
*out++ = key->state[t] ^ *in++;
}
key->x = x;
key->y = y;
}
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