git.distorted.org.uk Git - u/mdw/catacomb/blob - gfshare-mktab.c

   1 /* -*-c-*-
   2  *
   3  * $Id: gfshare-mktab.c,v 1.3 2000/06/18 23:26:09 mdw Exp $
   4  *
   5  * Generate tables for %$\gf{2^8}$% multiplication
   6  *
   7  * (c) 2000 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Catacomb.
  13  *
  14  * Catacomb is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * Catacomb is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with Catacomb; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 /*----- Revision history --------------------------------------------------*
  31  *
  32  * $Log: gfshare-mktab.c,v $
  33  * Revision 1.3  2000/06/18 23:26:09  mdw
  34  * Whoops.  Fix a typo.
  35  *
  36  * Revision 1.2  2000/06/18 23:12:15  mdw
  37  * Change typesetting of Galois Field names.
  38  *
  39  * Revision 1.1  2000/06/17 10:56:30  mdw
  40  * Fast but nonstandard secret sharing system.
  41  *
  42  */
  43
  44 /*----- Header files ------------------------------------------------------*/
  45
  46 #include <stdio.h>
  47 #include <stdlib.h>
  48
  49 #include <mLib/bits.h>
  50
  51 /*----- Magic numbers -----------------------------------------------------*/
  52
  53 #define MOD 0x11d
  54
  55 /*----- Main code ---------------------------------------------------------*/
  56
  57 int main(int argc, char *argv[])
  58 {
  59   octet log[256], alog[256];
  60   unsigned x;
  61   unsigned i;
  62
  63   x = 1;
  64   for (i = 0; i < 255; i++) {
  65     alog[i] = x;
  66     log[x] = i;
  67     x <<= 1;
  68     if (x & 0x100)
  69       x ^= MOD;
  70   }
  71   log[0] = 0;
  72   alog[255] = 1;
  73
  74   fputs("\
  75 /* -*-c-*-\n\
  76  *\n\
  77  * Log tables for secret sharing in %$\\gf{2^8}$% [generated]\n\
  78  */\n\
  79 \n\
  80 #ifndef GFSHARE_TAB_H\n\
  81 #define GFSHARE_TAB_H\n\
  82 \n\
  83 #define GFSHARE_LOG {                                                   \\\n\
  84   ", stdout);
  85
  86   for (i = 0; i < 256; i++) {
  87     printf("0x%02x", log[i]);
  88     if (i == 255)
  89       puts("                    \\\n}\n");
  90     else if (i % 8 == 7)
  91       fputs(",                  \\\n  ", stdout);
  92     else
  93       fputs(", ", stdout);
  94   }
  95
  96   fputs("\
  97 #define GFSHARE_EXP {                                                   \\\n\
  98   ", stdout);
  99
 100   for (i = 0; i < 510; i++) {
 101     printf("0x%02x", alog[i % 255]);
 102     if (i == 509)
 103       puts("                                    \\\n}\n");
 104     else if (i % 8 == 7)
 105       fputs(",                  \\\n  ", stdout);
 106     else
 107       fputs(", ", stdout);
 108   }
 109
 110   /* --- Done --- */
 111
 112   fputs("#endif\n", stdout);
 113
 114   if (fclose(stdout)) {
 115     fprintf(stderr, "error writing data\n");
 116     exit(EXIT_FAILURE);
 117   }
 118
 119   return (0);
 120 }
 121
 122 /*----- That's all, folks -------------------------------------------------*/