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 } 81