aesdata.c

#include <assert.h>
#include <inttypes.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#if 1
# define BYTE_FORMAT "0x%02x"
# define BYTE_COLUMNS 8
#else
# define BYTE_FORMAT "%3d"
# define BYTE_COLUMNS 0x10
#endif

#define WORD_FORMAT "0x%08x"
#define WORD_COLUMNS 4

uint8_t sbox[0x100];
uint8_t isbox[0x100];

uint8_t log[0x100];
uint8_t ilog[0x100];

uint32_t dtable[4][0x100];
uint32_t itable[4][0x100];

static unsigned
xtime(unsigned x)
{
  assert (x < 0x100);

  x <<= 1;
  if (x & 0x100)
    x ^= 0x11b;

  assert (x < 0x100);

  return x;
}

/* Computes the expoenntiatiom and logarithm tables for GF_2, to the
 * base x+1 (0x03). The unit element is 1 (0x01).*/
static void
compute_log(void)
{
  unsigned i = 0;
  unsigned x = 1;

  memset(log, 0, 0x100);
  
  for (i = 0; i < 0x100; i++, x = x ^ xtime(x))
    {
      ilog[i] = x;
      log[x] = i;
    }
  /* Invalid. */
  log[0] = 0;
  /* The loop above sets log[1] = 0xff, which is correct,
   * but log[1] = 0 is nicer. */
  log[1] = 0;
}

static unsigned
mult(unsigned a, unsigned b)
{
  return (a && b) ? ilog[ (log[a] + log[b]) % 255] : 0;
}

static unsigned
invert(unsigned x)