workbench/network/WirelessManager/src/crypto/rc4.c

   1 /*
   2  * RC4 stream cipher
   3  * Copyright (c) 2002-2005, Jouni Malinen <j@w1.fi>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  *
   9  * Alternatively, this software may be distributed under the terms of BSD
  10  * license.
  11  *
  12  * See README and COPYING for more details.
  13  */
  14
  15 #include "includes.h"
  16
  17 #include "common.h"
  18 #include "crypto.h"
  19
  20 #define S_SWAP(a,b) do { u8 t = S[a]; S[a] = S[b]; S[b] = t; } while(0)
  21
  22 int rc4_skip(const u8 *key, size_t keylen, size_t skip,
  23              u8 *data, size_t data_len)
  24 {
  25         u32 i, j, k;
  26         u8 S[256], *pos;
  27         size_t kpos;
  28
  29         /* Setup RC4 state */
  30         for (i = 0; i < 256; i++)
  31                 S[i] = i;
  32         j = 0;
  33         kpos = 0;
  34         for (i = 0; i < 256; i++) {
  35                 j = (j + S[i] + key[kpos]) & 0xff;
  36                 kpos++;
  37                 if (kpos >= keylen)
  38                         kpos = 0;
  39                 S_SWAP(i, j);
  40         }
  41
  42         /* Skip the start of the stream */
  43         i = j = 0;
  44         for (k = 0; k < skip; k++) {
  45                 i = (i + 1) & 0xff;
  46                 j = (j + S[i]) & 0xff;
  47                 S_SWAP(i, j);
  48         }
  49
  50         /* Apply RC4 to data */
  51         pos = data;
  52         for (k = 0; k < data_len; k++) {
  53                 i = (i + 1) & 0xff;
  54                 j = (j + S[i]) & 0xff;
  55                 S_SWAP(i, j);
  56                 *pos++ ^= S[(S[i] + S[j]) & 0xff];
  57         }
  58
  59         return 0;
  60 }