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

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