release/src/router/nettle/gcmdata.c

   1 /* gcmdata.c
   2  *
   3  * Galois counter mode, specified by NIST,
   4  * http://csrc.nist.gov/publications/nistpubs/800-38D/SP-800-38D.pdf
   5  *
   6  */
   7
   8 /* Generation of fixed multiplication tables. */
   9
  10 /* nettle, low-level cryptographics library
  11  *
  12  * Copyright (C) 2011 Niels Möller
  13  *
  14  * The nettle library is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Lesser General Public License as published by
  16  * the Free Software Foundation; either version 2.1 of the License, or (at your
  17  * option) any later version.
  18  *
  19  * The nettle library is distributed in the hope that it will be useful, but
  20  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  21  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
  22  * License for more details.
  23  *
  24  * You should have received a copy of the GNU Lesser General Public License
  25  * along with the nettle library; see the file COPYING.LIB.  If not, write to
  26  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
  27  * MA 02111-1301, USA.
  28  */
  29
  30 #include <stdio.h>
  31 #include <stdlib.h>
  32
  33 #define GHASH_POLYNOMIAL 0xE1
  34
  35
  36 /* When x is shifted out over the block edge, add multiples of the
  37    defining polynomial to eliminate each bit. */
  38 static unsigned
  39 reduce(unsigned x)
  40 {
  41   unsigned p = GHASH_POLYNOMIAL << 1;
  42   unsigned y = 0;
  43   for (; x; x >>= 1, p <<= 1)
  44     if (x & 1)
  45       y ^= p;
  46   return y;
  47 }
  48
  49 int
  50 main(int argc, char **argv)
  51 {
  52   unsigned i;
  53   printf("4-bit table:\n");
  54
  55   for (i = 0; i<16; i++)
  56     {
  57       unsigned x;
  58       if (i && !(i%8))
  59         printf("\n");
  60
  61       x = reduce(i << 4);
  62       printf("W(%02x,%02x),", x >> 8, x & 0xff);
  63     }
  64   printf("\n\n");
  65   printf("8-bit table:\n");
  66   for (i = 0; i<256; i++)
  67     {
  68       unsigned x;
  69       if (i && !(i%8))
  70         printf("\n");
  71
  72       x = reduce(i);
  73       printf("W(%02x,%02x),", x >> 8, x & 0xff);
  74     }
  75   printf("\n");
  76   return EXIT_SUCCESS;
  77 }