sys/crypto/arc4/arc4.c

   1 /*      $NetBSD: arc4.c,v 1.4.6.3 2004/09/21 13:26:15 skrll Exp $       */
   2
   3 /*
   4  * ARC4 implementation
   5  *      A Stream Cipher Encryption Algorithm "Arcfour"
   6  *      <draft-kaukonen-cipher-arcfour-03.txt>
   7  */
   8
   9 /*        This code illustrates a sample implementation
  10  *                 of the Arcfour algorithm
  11  *         Copyright (c) April 29, 1997 Kalle Kaukonen.
  12  *                    All Rights Reserved.
  13  *
  14  * Redistribution and use in source and binary forms, with or
  15  * without modification, are permitted provided that this copyright
  16  * notice and disclaimer are retained.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY KALLE KAUKONEN AND CONTRIBUTORS ``AS
  19  * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  21  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL KALLE
  22  * KAUKONEN OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  23  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  24  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  27  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  28  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  29  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  30  */
  31
  32 #include <sys/cdefs.h>
  33 __KERNEL_RCSID(0, "$NetBSD: arc4.c,v 1.4.6.3 2004/09/21 13:26:15 skrll Exp $");
  34
  35 #include <sys/types.h>
  36
  37 #include <crypto/arc4/arc4.h>
  38
  39 struct arc4_ctx {
  40         unsigned int    x;
  41         unsigned int    y;
  42         unsigned int    state[256];
  43         /* was unsigned char, changed to int for performance -- onoe */
  44 };
  45
  46 int
  47 arc4_ctxlen(void)
  48 {
  49         return sizeof(struct arc4_ctx);
  50 }
  51
  52 void
  53 arc4_setkey(void *ctxp, const u_char *key, u_int keylen)
  54 {
  55         struct arc4_ctx *ctx = ctxp;
  56         unsigned int i, t, u, ki, si;
  57         unsigned int *state;
  58
  59         state = ctx->state;
  60         ctx->x = 0;
  61         ctx->y = 0;
  62         for (i = 0; i < 256; i++)
  63                state[i] = i;
  64         ki = si = 0;
  65         for (i = 0; i < 256; i++) {
  66                 t = state[i];
  67                 si = (si + key[ki] + t) & 0xff;
  68                 u = state[si];
  69                 state[si] = t;
  70                 state[i] = u;
  71                 if (++ki >= keylen)
  72                         ki = 0;
  73         }
  74 }
  75
  76 void
  77 arc4_encrypt(void *ctxp, u_char *dst, const u_char *src, int len)
  78 {
  79         struct arc4_ctx *ctx = ctxp;
  80         unsigned int x, y, sx, sy;
  81         unsigned int *state;
  82         const unsigned char *endsrc;
  83
  84         state = ctx->state;
  85         x = ctx->x;
  86         y = ctx->y;
  87         for (endsrc = src + len; src != endsrc; src++, dst++) {
  88                 x = (x + 1) & 0xff;
  89                 sx = state[x];
  90                 y = (sx + y) & 0xff;
  91                 state[x] = sy = state[y];
  92                 state[y] = sx;
  93                 *dst = *src ^ state[(sx + sy) & 0xff];
  94         }
  95         ctx->x = x;
  96         ctx->y = y;
  97 }
  98
  99 void
 100 arc4_decrypt(void *ctxp, u_char *dst, const u_char *src, int len)
 101 {
 102
 103         arc4_encrypt(ctxp, dst, src, len);
 104 }