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
RC4_set_key(RC4_KEY * key,const int len,const unsigned char * data)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
RC4(RC4_KEY * key,const int len,const unsigned char * in,unsigned char * out)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 }
81