source/arcfour.c

   1 /*
   2    Unix SMB/Netbios implementation.
   3    Version 1.9.
   4
   5    a implementation of arcfour designed for use in the
   6    SMB password change protocol based on the description
   7    in 'Applied Cryptography', 2nd Edition.
   8
   9    Copyright (C) Jeremy Allison 1997
  10
  11    This program is free software; you can redistribute it and/or modify
  12    it under the terms of the GNU General Public License as published by
  13    the Free Software Foundation; either version 2 of the License, or
  14    (at your option) any later version.
  15
  16    This program is distributed in the hope that it will be useful,
  17    but WITHOUT ANY WARRANTY; without even the implied warranty of
  18    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19    GNU General Public License for more details.
  20
  21    You should have received a copy of the GNU General Public License
  22    along with this program; if not, write to the Free Software
  23    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  24 */
  25
  26 #include "arcfour.h"
  27
  28 void set_arc4_key(unsigned char *data, int key_length, arc4_key *arckey)
  29 {
  30   unsigned int i;
  31   unsigned char j;
  32   unsigned char tc;
  33   unsigned char *s_box = &arckey->s_box[0];
  34
  35   arckey->index_i = 0;
  36   arckey->index_j = 0;
  37   for(i = 0; i < 256; i++)
  38     s_box[i] = (unsigned char)i;
  39
  40   j = 0;
  41   for( i = 0; i < 256; i++)
  42   {
  43      j += (s_box[i] + data[i%key_length]);
  44      tc = s_box[i];
  45      s_box[i] = s_box[j];
  46      s_box[j] = tc;
  47   }
  48 }
  49
  50 void arc4(arc4_key *arckey, unsigned char *data_in, unsigned char *data_out,
  51           int length)
  52 {
  53   unsigned char tc;
  54   int ind;
  55   unsigned char i, j;
  56   unsigned char t;
  57   unsigned char *s_box = &arckey->s_box[0];
  58
  59   for( ind = 0; ind < length; ind++)
  60   {
  61     i = ++arckey->index_i;
  62     j = arckey->index_j += s_box[i];
  63     tc = s_box[i];
  64     s_box[i] = s_box[j];
  65     s_box[j] = tc;
  66     t = s_box[i] + s_box[j];
  67     *data_out++ = *data_in++ ^ s_box[t];
  68   }
  69 }
  70
  71 #if 0
  72 /* Test vector */
  73 unsigned char key_data[] = { 0x61, 0x8a, 0x63, 0xd2, 0xfb };
  74 unsigned char plaintext[] = { 0xdc, 0xee, 0x4c, 0xf9, 0x2c };
  75 unsigned char ciphertext[] = { 0xf1, 0x38, 0x29, 0xc9, 0xde };
  76
  77 int main(int argc, char *argv[])
  78 {
  79   unsigned char out[5];
  80   arc4_key key;
  81
  82   set_arc4_key(key_data, 5, &key);
  83   arc4(&key, plaintext, out, 5);
  84
  85   if(memcmp(out, ciphertext, 5) ==0)
  86     printf("Test ok !\n");
  87   else
  88     printf("Test fail !\n");
  89   return 0;
  90 }
  91 #endif