bsd/crypto/rc4/rc4.c

   1 /*
   2  * rc4.c
   3  *
   4  * Copyright (c) 1996-2000 Whistle Communications, Inc.
   5  * All rights reserved.
   6  *
   7  * Subject to the following obligations and disclaimer of warranty, use and
   8  * redistribution of this software, in source or object code forms, with or
   9  * without modifications are expressly permitted by Whistle Communications;
  10  * provided, however, that:
  11  * 1. Any and all reproductions of the source or object code must include the
  12  *    copyright notice above and the following disclaimer of warranties; and
  13  * 2. No rights are granted, in any manner or form, to use Whistle
  14  *    Communications, Inc. trademarks, including the mark "WHISTLE
  15  *    COMMUNICATIONS" on advertising, endorsements, or otherwise except as
  16  *    such appears in the above copyright notice or in the software.
  17  *
  18  * THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
  19  * TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
  20  * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
  21  * INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
  22  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
  23  * WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
  24  * REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
  25  * SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
  26  * IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
  27  * RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
  28  * WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
  29  * PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
  30  * SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY
  31  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  32  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  33  * THIS SOFTWARE, EVEN IF WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
  34  * OF SUCH DAMAGE.
  35  *
  36  * $FreeBSD: src/sys/crypto/rc4/rc4.c,v 1.2.2.1 2000/04/18 04:48:31 archie Exp $
  37  */
  38
  39 #include <sys/types.h>
  40 #include <crypto/rc4/rc4.h>
  41
  42 static __inline void
  43 swap_bytes(u_char *a, u_char *b)
  44 {
  45         u_char temp;
  46
  47         temp = *a;
  48         *a = *b;
  49         *b = temp;
  50 }
  51
  52 /*
  53  * Initialize an RC4 state buffer using the supplied key,
  54  * which can have arbitrary length.
  55  */
  56 void
  57 rc4_init(struct rc4_state *const state, const u_char *key, int keylen)
  58 {
  59         u_char j;
  60         int i;
  61
  62         /* Initialize state with identity permutation */
  63         for (i = 0; i < 256; i++) {
  64                 state->perm[i] = (u_char)i;
  65         }
  66         state->index1 = 0;
  67         state->index2 = 0;
  68
  69         /* Randomize the permutation using key data */
  70         for (j = i = 0; i < 256; i++) {
  71                 j += state->perm[i] + key[i % keylen];
  72                 swap_bytes(&state->perm[i], &state->perm[j]);
  73         }
  74 }
  75
  76 /*
  77  * Encrypt some data using the supplied RC4 state buffer.
  78  * The input and output buffers may be the same buffer.
  79  * Since RC4 is a stream cypher, this function is used
  80  * for both encryption and decryption.
  81  */
  82 void
  83 rc4_crypt(struct rc4_state *const state,
  84     const u_char *inbuf, u_char *outbuf, int buflen)
  85 {
  86         int i;
  87         u_char j;
  88
  89         for (i = 0; i < buflen; i++) {
  90                 /* Update modification indicies */
  91                 state->index1++;
  92                 state->index2 += state->perm[state->index1];
  93
  94                 /* Modify permutation */
  95                 swap_bytes(&state->perm[state->index1],
  96                     &state->perm[state->index2]);
  97
  98                 /* Encrypt/decrypt next byte */
  99                 j = state->perm[state->index1] + state->perm[state->index2];
 100                 outbuf[i] = inbuf[i] ^ state->perm[j];
 101         }
 102 }