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

   1 /* -*-c-*-
   2  *
   3  * $Id: gfshare-mktab.c,v 1.1 2000/06/17 10:56:30 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 1.1  2000/06/17 10:56:30  mdw
  34  * Fast but nonstandard secret sharing system.
  35  *
  36  */
  37
  38 /*----- Header files ------------------------------------------------------*/
  39
  40 #include <stdio.h>
  41 #include <stdlib.h>
  42
  43 #include <mLib/bits.h>
  44
  45 /*----- Magic numbers -----------------------------------------------------*/
  46
  47 #define MOD 0x11d
  48
  49 /*----- Main code ---------------------------------------------------------*/
  50
  51 int main(int argc, char *argv[])
  52 {
  53   octet log[256], alog[256];
  54   unsigned x;
  55   unsigned i;
  56
  57   x = 1;
  58   for (i = 0; i < 255; i++) {
  59     alog[i] = x;
  60     log[x] = i;
  61     x <<= 1;
  62     if (x & 0x100)
  63       x ^= MOD;
  64   }
  65   log[0] = 0;
  66   alog[255] = 1;
  67
  68   fputs("\
  69 /* -*-c-*-\n\
  70  *\n\
  71  * Log tables for secret sharing in %$\\gf(2^8)$% [generated]\n\
  72  */\n\
  73 \n\
  74 #ifndef GFSHARE_TAB_H\n\
  75 #define GFSHARE_TAB_H\n\
  76 \n\
  77 #define GFSHARE_LOG {                                                   \\\n\
  78   ", stdout);
  79
  80   for (i = 0; i < 256; i++) {
  81     printf("0x%02x", log[i]);
  82     if (i == 255)
  83       puts("                    \\\n}\n");
  84     else if (i % 8 == 7)
  85       fputs(",                  \\\n  ", stdout);
  86     else
  87       fputs(", ", stdout);
  88   }
  89
  90   fputs("\
  91 #define GFSHARE_EXP {                                                   \\\n\
  92   ", stdout);
  93
  94   for (i = 0; i < 510; i++) {
  95     printf("0x%02x", alog[i % 255]);
  96     if (i == 509)
  97       puts("                                    \\\n}\n");
  98     else if (i % 8 == 7)
  99       fputs(",                  \\\n  ", stdout);
 100     else
 101       fputs(", ", stdout);
 102   }
 103
 104   /* --- Done --- */
 105
 106   fputs("#endif\n", stdout);
 107
 108   if (fclose(stdout)) {
 109     fprintf(stderr, "error writing data\n");
 110     exit(EXIT_FAILURE);
 111   }
 112
 113   return (0);
 114 }
 115
 116 /*----- That's all, folks -------------------------------------------------*/