lib/hcrypto/rc4.c

   1 /*
   2  * Copyright (c) 2004 Kungliga Tekniska Högskolan
   3  * (Royal Institute of Technology, Stockholm, Sweden).
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  *
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  *
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * 3. Neither the name of the Institute nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 /* implemented from description in draft-kaukonen-cipher-arcfour-03.txt */
  35
  36 #ifdef HAVE_CONFIG_H
  37 #include "config.h"
  38
  39 RCSID("$Id$");
  40 #endif
  41
  42 #include <rc4.h>
  43
  44 #define SWAP(k,x,y)                             \
  45 { unsigned int _t;                              \
  46   _t = k->state[x];                             \
  47   k->state[x] = k->state[y];                    \
  48   k->state[y] = _t;                             \
  49 }
  50
  51 void
  52 RC4_set_key(RC4_KEY *key, const int len, unsigned char *data)
  53 {
  54     int i, j;
  55
  56     for (i = 0; i < 256; i++)
  57         key->state[i] = i;
  58     for (i = 0, j = 0; i < 256; i++) {
  59         j = (j + key->state[i] + data[i % len]) % 256;
  60         SWAP(key, i, j);
  61     }
  62     key->x = key->y = 0;
  63 }
  64
  65 void
  66 RC4(RC4_KEY *key, const int len, const unsigned char *in, unsigned char *out)
  67 {
  68     int i, t;
  69     unsigned x, y;
  70
  71     x = key->x;
  72     y = key->y;
  73     for (i = 0; i < len; i++) {
  74         x = (x + 1) % 256;
  75         y = (y + key->state[x]) % 256;
  76         SWAP(key, x, y);
  77         t = (key->state[x] + key->state[y]) % 256;
  78         *out++ = key->state[t] ^ *in++;
  79     }
  80     key->x = x;
  81     key->y = y;
  82 }