src/xyssl/arc4.c

   1 /*
   2  *  An implementation of the ARCFOUR algorithm
   3  *
   4  *  Copyright (C) 2006-2007  Christophe Devine
   5  *
   6  *  This program is free software; you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation; either version 2 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  This program is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License along
  17  *  with this program; if not, write to the Free Software Foundation, Inc.,
  18  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  19  */
  20 /*
  21  *  The ARCFOUR algorithm was publicly disclosed on 94/09.
  22  *
  23  *  http://groups.google.com/group/sci.crypt/msg/10a300c9d21afca0
  24  */
  25
  26 #include "xyssl/config.h"
  27
  28 #if defined(XYSSL_ARC4_C)
  29
  30 #include "xyssl/arc4.h"
  31
  32 /*
  33  * ARC4 key schedule
  34  */
  35 void arc4_setup( arc4_context *ctx, unsigned char *key, int keylen )
  36 {
  37     int i, j, k, a;
  38     unsigned char *m;
  39
  40     ctx->x = 0;
  41     ctx->y = 0;
  42     m = ctx->m;
  43
  44     for( i = 0; i < 256; i++ )
  45         m[i] = (unsigned char) i;
  46
  47     j = k = 0;
  48
  49     for( i = 0; i < 256; i++, k++ )
  50     {
  51         if( k >= keylen ) k = 0;
  52
  53         a = m[i];
  54         j = ( j + a + key[k] ) & 0xFF;
  55         m[i] = m[j];
  56         m[j] = (unsigned char) a;
  57     }
  58 }
  59
  60 /*
  61  * ARC4 cipher function
  62  */
  63 void arc4_crypt( arc4_context *ctx, unsigned char *buf, int buflen )
  64 {
  65     int i, x, y, a, b;
  66     unsigned char *m;
  67
  68     x = ctx->x;
  69     y = ctx->y;
  70     m = ctx->m;
  71
  72     for( i = 0; i < buflen; i++ )
  73     {
  74         x = ( x + 1 ) & 0xFF; a = m[x];
  75         y = ( y + a ) & 0xFF; b = m[y];
  76
  77         m[x] = (unsigned char) b;
  78         m[y] = (unsigned char) a;
  79
  80         buf[i] = (unsigned char)
  81             ( buf[i] ^ m[(unsigned char)( a + b )] );
  82     }
  83
  84     ctx->x = x;
  85     ctx->y = y;
  86 }
  87
  88 #if defined(XYSSL_SELF_TEST)
  89
  90 #include <string.h>
  91 #include <stdio.h>
  92
  93 /*
  94  * ARC4 tests vectors as posted by Eric Rescorla in sep. 1994:
  95  *
  96  * http://groups.google.com/group/comp.security.misc/msg/10a300c9d21afca0
  97  */
  98 static const unsigned char arc4_test_key[3][8] =
  99 {
 100     { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
 101     { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
 102     { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }
 103 };
 104
 105 static const unsigned char arc4_test_pt[3][8] =
 106 {
 107     { 0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF },
 108     { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
 109     { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }
 110 };
 111
 112 static const unsigned char arc4_test_ct[3][8] =
 113 {
 114     { 0x75, 0xB7, 0x87, 0x80, 0x99, 0xE0, 0xC5, 0x96 },
 115     { 0x74, 0x94, 0xC2, 0xE7, 0x10, 0x4B, 0x08, 0x79 },
 116     { 0xDE, 0x18, 0x89, 0x41, 0xA3, 0x37, 0x5D, 0x3A }
 117 };
 118
 119 /*
 120  * Checkup routine
 121  */
 122 int arc4_self_test( int verbose )
 123 {
 124     int i;
 125     unsigned char buf[8];
 126     arc4_context ctx;
 127
 128     for( i = 0; i < 3; i++ )
 129     {
 130         if( verbose != 0 )
 131             printf( "  ARC4 test #%d: ", i + 1 );
 132
 133         memcpy( buf, arc4_test_pt[i], 8 );
 134
 135         arc4_setup( &ctx, (unsigned char *) arc4_test_key[i], 8 );
 136         arc4_crypt( &ctx, buf, 8 );
 137
 138         if( memcmp( buf, arc4_test_ct[i], 8 ) != 0 )
 139         {
 140             if( verbose != 0 )
 141                 printf( "failed\n" );
 142
 143             return( 1 );
 144         }
 145
 146         if( verbose != 0 )
 147             printf( "passed\n" );
 148     }
 149
 150     if( verbose != 0 )
 151         printf( "\n" );
 152
 153     return( 0 );
 154 }
 155
 156 #endif
 157
 158 #endif