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      1 /*	$NetBSD: rc4.c,v 1.2 2017/01/28 21:31:47 christos Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 2004 Kungliga Tekniska Hgskolan
      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 #include <krb5/roken.h>
     40 
     41 #include <rc4.h>
     42 
     43 #define SWAP(k,x,y)				\
     44 { unsigned int _t; 				\
     45   _t = k->state[x]; 				\
     46   k->state[x] = k->state[y]; 			\
     47   k->state[y] = _t;				\
     48 }
     49 
     50 void
     51 RC4_set_key(RC4_KEY *key, const int len, const unsigned char *data)
     52 {
     53     int i, j;
     54 
     55     for (i = 0; i < 256; i++)
     56 	key->state[i] = i;
     57     for (i = 0, j = 0; i < 256; i++) {
     58 	j = (j + key->state[i] + data[i % len]) % 256;
     59 	SWAP(key, i, j);
     60     }
     61     key->x = key->y = 0;
     62 }
     63 
     64 void
     65 RC4(RC4_KEY *key, const int len, const unsigned char *in, unsigned char *out)
     66 {
     67     int i, t;
     68     unsigned x, y;
     69 
     70     x = key->x;
     71     y = key->y;
     72     for (i = 0; i < len; i++) {
     73 	x = (x + 1) % 256;
     74 	y = (y + key->state[x]) % 256;
     75 	SWAP(key, x, y);
     76 	t = (key->state[x] + key->state[y]) % 256;
     77 	*out++ = key->state[t] ^ *in++;
     78     }
     79     key->x = x;
     80     key->y = y;
     81 }
     82