crypto/external/bsd/heimdal/dist/lib/hcrypto/rc4.c

   1 /*      $NetBSD: rc4.c,v 1.1.1.1 2011/04/13 18:14:51 elric Exp $        */
   2
   3 /*
   4  * Copyright (c) 2004 Kungliga Tekniska Högskolan
   5  * (Royal Institute of Technology, Stockholm, Sweden).
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  *
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  *
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * 3. Neither the name of the Institute nor the names of its contributors
  20  *    may be used to endorse or promote products derived from this software
  21  *    without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
  24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
  27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  33  * SUCH DAMAGE.
  34  */
  35
  36 /* implemented from description in draft-kaukonen-cipher-arcfour-03.txt */
  37
  38 #include "config.h"
  39
  40 #include <rc4.h>
  41
  42 #define SWAP(k,x,y)                             \
  43 { unsigned int _t;                              \
  44   _t = k->state[x];                             \
  45   k->state[x] = k->state[y];                    \
  46   k->state[y] = _t;                             \
  47 }
  48
  49 void
  50 RC4_set_key(RC4_KEY *key, const int len, const unsigned char *data)
  51 {
  52     int i, j;
  53
  54     for (i = 0; i < 256; i++)
  55         key->state[i] = i;
  56     for (i = 0, j = 0; i < 256; i++) {
  57         j = (j + key->state[i] + data[i % len]) % 256;
  58         SWAP(key, i, j);
  59     }
  60     key->x = key->y = 0;
  61 }
  62
  63 void
  64 RC4(RC4_KEY *key, const int len, const unsigned char *in, unsigned char *out)
  65 {
  66     int i, t;
  67     unsigned x, y;
  68
  69     x = key->x;
  70     y = key->y;
  71     for (i = 0; i < len; i++) {
  72         x = (x + 1) % 256;
  73         y = (y + key->state[x]) % 256;
  74         SWAP(key, x, y);
  75         t = (key->state[x] + key->state[y]) % 256;
  76         *out++ = key->state[t] ^ *in++;
  77     }
  78     key->x = x;
  79     key->y = y;
  80 }