rosapps/smartpdf/fitz/stream/crypt_arc4.c

   1 /*        This code illustrates a sample implementation
   2  *                 of the Arcfour algorithm
   3  *         Copyright (c) April 29, 1997 Kalle Kaukonen.
   4  *                    All Rights Reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or
   7  * without modification, are permitted provided that this copyright
   8  * notice and disclaimer are retained.
   9  *
  10  * THIS SOFTWARE IS PROVIDED BY KALLE KAUKONEN AND CONTRIBUTORS ``AS
  11  * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  12  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  13  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL KALLE
  14  * KAUKONEN OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  15  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  16  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  17  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  18  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  19  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  20  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  21  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  22  */
  23
  24 #include "fitz-base.h"
  25 #include "fitz-stream.h"
  26
  27 void
  28 fz_arc4init(fz_arc4 *arc4, unsigned char *key, unsigned keylen)
  29 {
  30         unsigned int t, u;
  31         unsigned int keyindex;
  32         unsigned int stateindex;
  33         unsigned char *state;
  34         unsigned int counter;
  35
  36         state = arc4->state;
  37
  38         arc4->x = 0;
  39         arc4->y = 0;
  40
  41         for (counter = 0; counter < 256; counter++) {
  42                 state[counter] = counter;
  43         }
  44
  45         keyindex = 0;
  46         stateindex = 0;
  47
  48         for (counter = 0; counter < 256; counter++) {
  49                 t = state[counter];
  50                 stateindex = (stateindex + key[keyindex] + t) & 0xff;
  51                 u = state[stateindex];
  52
  53                 state[stateindex] = t;
  54                 state[counter] = u;
  55
  56                 if (++keyindex >= keylen) {
  57                         keyindex = 0;
  58                 }
  59         }
  60 }
  61
  62 unsigned char
  63 fz_arc4next(fz_arc4 *arc4)
  64 {
  65         unsigned int x;
  66         unsigned int y;
  67         unsigned int sx, sy;
  68         unsigned char *state;
  69
  70         state = arc4->state;
  71
  72         x = (arc4->x + 1) & 0xff;
  73         sx = state[x];
  74         y = (sx + arc4->y) & 0xff;
  75         sy = state[y];
  76
  77         arc4->x = x;
  78         arc4->y = y;
  79
  80         state[y] = sx;
  81         state[x] = sy;
  82
  83         return state[(sx + sy) & 0xff];
  84 }
  85
  86 void
  87 fz_arc4encrypt(fz_arc4 *arc4, unsigned char *dest, unsigned char *src, unsigned len)
  88 {
  89         unsigned int i;
  90         for (i = 0; i < len; i++) {
  91                 unsigned char x;
  92                 x = fz_arc4next(arc4);
  93                 dest[i] = src[i] ^ x;
  94         }
  95 }
  96