New program for generating AES-related tables.

Rev: src/nettle/aesdata.c:1.1

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)
+{
+  return x ? ilog[0xff - log[x]] : 0;
+}
+
+static unsigned
+affine(unsigned x)
+{
+  return 0xff &
+    (0x63^x^(x>>4)^(x<<4)^(x>>5)^(x<<3)^(x>>6)^(x<<2)^(x>>7)^(x<<1));
+}
+     
+static void
+compute_sbox(void)
+{
+  unsigned i;
+  for (i = 0; i<0x100; i++)
+    {
+      sbox[i] = affine(invert(i));
+      isbox[sbox[i]] = i;
+    }
+}
+
+/* Generate little endian tables, i.e. the first row of the AES state
+ * arrays occupies the least significant byte of the words.
+ *
+ * The sbox values are multiplied with the column of GF2 coefficients
+ * of the polynomial 03 x^3 + x^2 + x + 02. */
+static void
+compute_dtable(void)
+{
+  unsigned i;
+  for (i = 0; i<0x100; i++)
+    {
+      unsigned s = sbox[i];
+      unsigned j;
+      uint32_t t  =( ( (s ^ xtime(s)) << 24)
+		     | (s << 16) | (s << 8)
+		     | xtime(s) );
+
+      for (j = 0; j<4; j++, t = (t << 8) | (t >> 24))
+	dtable[j][i] = t;
+    }
+}
+
+/* The inverse sbox values are multiplied with the column of GF2 coefficients
+ * of the polynomial inverse 0b x^3 + 0d x^2 + 09 x + 0e. */
+static void
+compute_itable(void)
+{
+  unsigned i;
+  for (i = 0; i<0x100; i++)
+    {
+      unsigned s = isbox[i];
+      unsigned j;
+      uint32_t t = ( (mult(s, 0xb) << 24)
+		   | (mult(s, 0xd) << 16)
+		   | (mult(s, 0x9) << 8)
+		   | (mult(s, 0xe) ));
+      
+      for (j = 0; j<4; j++, t = (t << 8) | (t >> 24))
+	itable[j][i] = t;
+    }
+}
+
+static void
+display_byte_table(const char *name, uint8_t *table)
+{
+  unsigned i, j;
+
+  printf("uint8_t %s[0x100] =\n{", name);
+
+  for (i = 0; i<0x100; i+= BYTE_COLUMNS)
+    {
+      printf("\n  ");
+      for (j = 0; j<BYTE_COLUMNS; j++)
+	printf(BYTE_FORMAT ",", table[i + j]);
+    }
+
+  printf("\n};\n\n");
+}
+
+static void
+display_table(const char *name, uint32_t table[][0x100])
+{
+  unsigned i, j, k;
+  
+  printf("uint32_t %s[4][0x100] =\n{\n  ", name);
+
+  for (k = 0; k<4; k++)
+    {
+      printf("{ ");
+      for (i = 0; i<0x100; i+= WORD_COLUMNS)
+	{
+	  printf("\n    ");
+	  for (j = 0; j<WORD_COLUMNS; j++)
+	    printf(WORD_FORMAT ",", table[k][i + j]);
+	}
+      printf("\n  },");
+    }
+  printf("\n};\n\n");
+}
+
+static void
+display_polynomial(const unsigned *p)
+{
+  printf("(%x x^3 + %x x^2 + %x x + %x)",
+	 p[3], p[2], p[1], p[0]);
+}
+
+int
+main(int argc, char **argv)
+{
+  compute_log();
+  if (argc == 1)
+    {
+      display_byte_table("log", log);
+      display_byte_table("ilog", ilog);
+
+      compute_sbox();
+      display_byte_table("sbox", sbox);
+      display_byte_table("isbox", isbox);
+
+      compute_dtable();
+      display_table("dtable", dtable);
+
+      compute_itable();
+      display_table("itable", itable);
+  
+      return 0;
+    }
+  else if (argc == 2)
+    {
+      unsigned a;
+      for (a = 1; a<0x100; a++)
+	{
+	  unsigned a1 = invert(a);
+	  unsigned b;
+	  unsigned u;
+	  if (a1 == 0)
+	    printf("invert(%x) = 0 !\n", a);
+
+	  u = mult(a, a1);
+	  if (u != 1)
+	    printf("invert(%x) = %x; product = %x\n",
+		   a, a1, u);
+	  
+	  for (b = 1; b<0x100; b++)
+	    {
+	      unsigned b1 = invert(b);
+	      unsigned c = mult(a, b);
+
+	      if (c == 0)
+		printf("%x x %x = 0\n", a, b);
+
+	      u = mult(c, a1);
+	      if (u != b)
+		printf("%x x %x = %x, invert(%x) = %x, %x x %x = %x\n",
+		       a, b, c, a, a1, c, a1, u);
+	      
+	      u = mult(c, b1);
+	      if (u != a)
+		printf("%x x %x = %x, invert(%x) = %x, %x x %x = %x\n",
+		       a, b, c, b, b1, c, b1, u);
+	    }
+	}
+      return 0;
+    }
+  else if (argc == 4)
+    {
+      unsigned a, b, c;
+      int op = argv[2][0];
+      a = strtoul(argv[1], NULL, 16);
+      b = strtoul(argv[3], NULL, 16);
+      switch (op)
+	{
+	case '+':
+	  c = a ^ b;
+	  break;
+	case '*':
+	case 'x':
+	  c = mult(a,b);
+	  break;
+	case '/':
+	  c = mult(a, invert(b));
+	  break;
+	default:
+	  return 1;
+	}
+      printf("%x %c %x = %x\n", a, op, b, c);
+      return 0;
+    }
+#if 0
+  else if (argc == 5)
+    {
+      /* Compute gcd(a, x^4+1) */
+      unsigned d[4];
+      unsigned u[4];
+      
+      for (i = 0; i<4; i++)
+	a[i] = strtoul(argv[1+i], NULL, 16);
+    }
+#endif
+  else if (argc == 9)
+    {
+      unsigned a[4];
+      unsigned b[4];
+      unsigned c[4];
+      unsigned i;
+      for (i = 0; i<4; i++)
+	{
+	  a[i] = strtoul(argv[1+i], NULL, 16);
+	  b[i] = strtoul(argv[5+i], NULL, 16);
+	}
+
+      c[0] = mult(a[0],b[0])^mult(a[3],b[1])^mult(a[2],b[2])^mult(a[1],b[3]);
+      c[1] = mult(a[1],b[0])^mult(a[0],b[1])^mult(a[3],b[2])^mult(a[2],b[3]);
+      c[2] = mult(a[2],b[0])^mult(a[1],b[1])^mult(a[0],b[2])^mult(a[3],b[3]);
+      c[3] = mult(a[3],b[0])^mult(a[2],b[1])^mult(a[1],b[2])^mult(a[0],b[3]);
+
+      display_polynomial(a); printf(" * "); display_polynomial(b);
+      printf(" = "); display_polynomial(c); printf("\n");
+    }
+  return 1;
+}