release/src/router/nettle/arcfour-crypt.c

   1 /* arcfour-crypt.c
   2  *
   3  * The arcfour/rc4 stream cipher.
   4  */
   5
   6 /* nettle, low-level cryptographics library
   7  *
   8  * Copyright (C) 2001, 2004 Niels Möller
   9  *
  10  * The nettle library is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU Lesser General Public License as published by
  12  * the Free Software Foundation; either version 2.1 of the License, or (at your
  13  * option) any later version.
  14  *
  15  * The nettle library is distributed in the hope that it will be useful, but
  16  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  17  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
  18  * License for more details.
  19  *
  20  * You should have received a copy of the GNU Lesser General Public License
  21  * along with the nettle library; see the file COPYING.LIB.  If not, write to
  22  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
  23  * MA 02111-1301, USA.
  24  */
  25
  26 #if HAVE_CONFIG_H
  27 # include "config.h"
  28 #endif
  29
  30 #include <assert.h>
  31
  32 #include "arcfour.h"
  33
  34 void
  35 arcfour_crypt(struct arcfour_ctx *ctx,
  36               unsigned length, uint8_t *dst,
  37               const uint8_t *src)
  38 {
  39   register uint8_t i, j;
  40   register int si, sj;
  41
  42   i = ctx->i; j = ctx->j;
  43   while(length--)
  44     {
  45       i++; i &= 0xff;
  46       si = ctx->S[i];
  47       j += si; j &= 0xff;
  48       sj = ctx->S[i] = ctx->S[j];
  49       ctx->S[j] = si;
  50       *dst++ = *src++ ^ ctx->S[ (si + sj) & 0xff ];
  51     }
  52   ctx->i = i; ctx->j = j;
  53 }