Introduced 4-bit tables. Gives gmac performance of 45 cycles per

byte (still on intel x86_64).
* gcm.c (gcm_gf_shift): Renamed. Tweaked little-endian masks.
(gcm_rightshift): ... old name.
(gcm_gf_mul): New argument for the output. Added length argument
for one of the inputs (implicitly padding with zeros).
(shift_table): New table (in 4-bit and 8-bit versions), generated
by gcmdata.
(gcm_gf_shift_chunk): New function shifting 4 bits at
a time.
(gcm_gf_mul_chunk): New function processing 4 bits at a time.
(gcm_set_key): Generation of 4-bit key table.
(gcm_hash): Use tables, when available.

Rev: nettle/gcm.c:1.5

diff --git a/gcm.c b/gcm.c
index 1f065f11c32b92865dacb5f0f3e5dba95bfa0841..ad40acc3aa3d4782fae8a18bcfae72c0a96654f4 100644 (file)
--- a/gcm.c
+++ b/gcm.c
@@ -49,9 +49,9 @@
 
 /* Multiplication by 010...0; a big-endian shift right. If the bit
    shifted out is one, the defining polynomial is added to cancel it
-   out. */
+   out. The argument must be properly aligned for word accesses. */
 static void
-gcm_rightshift (uint8_t *x)
+gcm_gf_shift (uint8_t *x)
 {
   unsigned long *w = (unsigned long *) x;
   long mask;
@@ -74,7 +74,7 @@ gcm_rightshift (uint8_t *x)
 # if SIZEOF_LONG == 4
 #define RSHIFT_WORD(x) \
   ((((x) & 0xfefefefeUL) >> 1) \
-   | (((x) & 0x01010101) << 15))
+   | (((x) & 0x00010101) << 15))
   mask = - ((w[3] >> 24) & 1);
   w[3] = RSHIFT_WORD(w[3]) | ((w[2] >> 17) & 0x80);
   w[2] = RSHIFT_WORD(w[2]) | ((w[1] >> 17) & 0x80);
@@ -83,20 +83,22 @@ gcm_rightshift (uint8_t *x)
 # elif SIZEOF_LONG == 8
 #define RSHIFT_WORD(x) \
   ((((x) & 0xfefefefefefefefeUL) >> 1) \
-   | (((x) & 0x0101010101010101UL) << 15))
+   | (((x) & 0x0001010101010101UL) << 15))
   mask = - ((w[1] >> 56) & 1);
   w[1] = RSHIFT_WORD(w[1]) | ((w[0] >> 49) & 0x80);
   w[0] = RSHIFT_WORD(w[0]) ^ (mask & GHASH_POLYNOMIAL);
 # else
 #  error Unsupported word size. */
 # endif
+# undef RSHIFT_WORD
 #endif /* ! WORDS_BIGENDIAN */
 }
 
-/* Sets a <- a * b mod r, using the plain bitwise algorithm from the
-   specification. */
+/* Sets r <- x * y mod r, using the plain bitwise algorithm from the
+   specification. y may be shorter than a full block, missing bytes
+   are assumed zero. */
 static void
-gcm_gf_mul (uint8_t *x, const uint8_t *y)
+gcm_gf_mul (uint8_t *r, const uint8_t *x, unsigned yn, const uint8_t *y)
 {
   uint8_t V[GCM_BLOCK_SIZE];
   uint8_t Z[GCM_BLOCK_SIZE];
@@ -105,7 +107,7 @@ gcm_gf_mul (uint8_t *x, const uint8_t *y)
   memcpy(V, x, sizeof(V));
   memset(Z, 0, sizeof(Z));
 
-  for (i = 0; i < GCM_BLOCK_SIZE; i++)
+  for (i = 0; i < yn; i++)
     {
       uint8_t b = y[i];
       unsigned j;
@@ -114,11 +116,136 @@ gcm_gf_mul (uint8_t *x, const uint8_t *y)
          if (b & 0x80)
            memxor(Z, V, sizeof(V));
          
-         gcm_rightshift(V);
+         gcm_gf_shift(V);
        }
     }
+  memcpy (r, Z, sizeof(Z));
+}
+
+#if GCM_TABLE_BITS
+# if WORDS_BIGENDIAN
+#  define W(left,right) (0x##left##right)
+# else
+#  define W(left,right) (0x##right##left)
+# endif
+
+#if GCM_TABLE_BITS == 4
+static const uint16_t
+shift_table[0x10] = {
+  W(00,00),W(1c,20),W(38,40),W(24,60),W(70,80),W(6c,a0),W(48,c0),W(54,e0),
+  W(e1,00),W(fd,20),W(d9,40),W(c5,60),W(91,80),W(8d,a0),W(a9,c0),W(b5,e0),
+};
+#elif GCM_TABLE_BITS == 8
+static const uint16_t
+shift_table[0x100] = {
+  W(00,00),W(01,c2),W(03,84),W(02,46),W(07,08),W(06,ca),W(04,8c),W(05,4e),
+  W(0e,10),W(0f,d2),W(0d,94),W(0c,56),W(09,18),W(08,da),W(0a,9c),W(0b,5e),
+  W(1c,20),W(1d,e2),W(1f,a4),W(1e,66),W(1b,28),W(1a,ea),W(18,ac),W(19,6e),
+  W(12,30),W(13,f2),W(11,b4),W(10,76),W(15,38),W(14,fa),W(16,bc),W(17,7e),
+  W(38,40),W(39,82),W(3b,c4),W(3a,06),W(3f,48),W(3e,8a),W(3c,cc),W(3d,0e),
+  W(36,50),W(37,92),W(35,d4),W(34,16),W(31,58),W(30,9a),W(32,dc),W(33,1e),
+  W(24,60),W(25,a2),W(27,e4),W(26,26),W(23,68),W(22,aa),W(20,ec),W(21,2e),
+  W(2a,70),W(2b,b2),W(29,f4),W(28,36),W(2d,78),W(2c,ba),W(2e,fc),W(2f,3e),
+  W(70,80),W(71,42),W(73,04),W(72,c6),W(77,88),W(76,4a),W(74,0c),W(75,ce),
+  W(7e,90),W(7f,52),W(7d,14),W(7c,d6),W(79,98),W(78,5a),W(7a,1c),W(7b,de),
+  W(6c,a0),W(6d,62),W(6f,24),W(6e,e6),W(6b,a8),W(6a,6a),W(68,2c),W(69,ee),
+  W(62,b0),W(63,72),W(61,34),W(60,f6),W(65,b8),W(64,7a),W(66,3c),W(67,fe),
+  W(48,c0),W(49,02),W(4b,44),W(4a,86),W(4f,c8),W(4e,0a),W(4c,4c),W(4d,8e),
+  W(46,d0),W(47,12),W(45,54),W(44,96),W(41,d8),W(40,1a),W(42,5c),W(43,9e),
+  W(54,e0),W(55,22),W(57,64),W(56,a6),W(53,e8),W(52,2a),W(50,6c),W(51,ae),
+  W(5a,f0),W(5b,32),W(59,74),W(58,b6),W(5d,f8),W(5c,3a),W(5e,7c),W(5f,be),
+  W(e1,00),W(e0,c2),W(e2,84),W(e3,46),W(e6,08),W(e7,ca),W(e5,8c),W(e4,4e),
+  W(ef,10),W(ee,d2),W(ec,94),W(ed,56),W(e8,18),W(e9,da),W(eb,9c),W(ea,5e),
+  W(fd,20),W(fc,e2),W(fe,a4),W(ff,66),W(fa,28),W(fb,ea),W(f9,ac),W(f8,6e),
+  W(f3,30),W(f2,f2),W(f0,b4),W(f1,76),W(f4,38),W(f5,fa),W(f7,bc),W(f6,7e),
+  W(d9,40),W(d8,82),W(da,c4),W(db,06),W(de,48),W(df,8a),W(dd,cc),W(dc,0e),
+  W(d7,50),W(d6,92),W(d4,d4),W(d5,16),W(d0,58),W(d1,9a),W(d3,dc),W(d2,1e),
+  W(c5,60),W(c4,a2),W(c6,e4),W(c7,26),W(c2,68),W(c3,aa),W(c1,ec),W(c0,2e),
+  W(cb,70),W(ca,b2),W(c8,f4),W(c9,36),W(cc,78),W(cd,ba),W(cf,fc),W(ce,3e),
+  W(91,80),W(90,42),W(92,04),W(93,c6),W(96,88),W(97,4a),W(95,0c),W(94,ce),
+  W(9f,90),W(9e,52),W(9c,14),W(9d,d6),W(98,98),W(99,5a),W(9b,1c),W(9a,de),
+  W(8d,a0),W(8c,62),W(8e,24),W(8f,e6),W(8a,a8),W(8b,6a),W(89,2c),W(88,ee),
+  W(83,b0),W(82,72),W(80,34),W(81,f6),W(84,b8),W(85,7a),W(87,3c),W(86,fe),
+  W(a9,c0),W(a8,02),W(aa,44),W(ab,86),W(ae,c8),W(af,0a),W(ad,4c),W(ac,8e),
+  W(a7,d0),W(a6,12),W(a4,54),W(a5,96),W(a0,d8),W(a1,1a),W(a3,5c),W(a2,9e),
+  W(b5,e0),W(b4,22),W(b6,64),W(b7,a6),W(b2,e8),W(b3,2a),W(b1,6c),W(b0,ae),
+  W(bb,f0),W(ba,32),W(b8,74),W(b9,b6),W(bc,f8),W(bd,3a),W(bf,7c),W(be,be),
+};
+#else
+#error Unsupported table size
+#endif
+#undef W
+
+/* Like gcm_rightshift, but shifts GCM_TABLE_BITS steps. */
+#if GCM_TABLE_BITS == 4
+
+static void
+gcm_gf_shift_chunk(uint8_t *x)
+{
+  unsigned long *w = (unsigned long *) x;
+  unsigned long reduce;
+
+  /* Shift uses big-endian representation. */
+#if WORDS_BIGENDIAN
+# if SIZEOF_LONG == 4
+  reduce = shift_table[w[3] & 0xf];
+  w[3] = (w[3] >> 4) | ((w[2] & 0xf) << 28);
+  w[2] = (w[2] >> 4) | ((w[1] & 0xf) << 28);
+  w[1] = (w[1] >> 4) | ((w[0] & 0xf) << 28);
+  w[0] = (w[0] >> 4) ^ (reduce << 16);
+# elif SIZEOF_LONG == 8
+  reduce = shift_table[w[3] & 0xf];
+  w[1] = (w[1] >> 4) | ((w[0] & 0xf) << 63);
+  w[0] = (w[0] >> 4) ^ (reduce << 48);
+# else
+#  error Unsupported word size. */
+#endif
+#else /* ! WORDS_BIGENDIAN */
+# if SIZEOF_LONG == 4
+#define RSHIFT_WORD(x) \
+  ((((x) & 0xf0f0f0f0UL) >> 4)                 \
+   | (((x) & 0x000f0f0f) << 12))
+  reduce = shift_table[(w[3] >> 24) & 0xf];
+  w[3] = RSHIFT_WORD(w[3]) | ((w[2] >> 20) & 0xf0);
+  w[2] = RSHIFT_WORD(w[2]) | ((w[1] >> 20) & 0xf0);
+  w[1] = RSHIFT_WORD(w[1]) | ((w[0] >> 20) & 0xf0);
+  w[0] = RSHIFT_WORD(w[0]) ^ reduce;
+# elif SIZEOF_LONG == 8
+#define RSHIFT_WORD(x) \
+  ((((x) & 0xf0f0f0f0f0f0f0f0UL) >> 4) \
+   | (((x) & 0x000f0f0f0f0f0f0fUL) << 12))
+  reduce = shift_table[(w[1] >> 56) & 0xf];
+  w[1] = RSHIFT_WORD(w[1]) | ((w[0] >> 52) & 0xf0);
+  w[0] = RSHIFT_WORD(w[0]) ^ reduce;
+# else
+#  error Unsupported word size. */
+# endif
+# undef RSHIFT_WORD
+#endif /* ! WORDS_BIGENDIAN */
+}
+
+/* FIXME: Table should be const. */
+static void
+gcm_gf_mul_chunk (uint8_t *x, const uint8_t *h, uint8_t table[16][16])
+{
+  uint8_t Z[GCM_BLOCK_SIZE];
+  unsigned i;
+
+  memset(Z, 0, sizeof(Z));
+
+  for (i = GCM_BLOCK_SIZE; i-- > 0;)
+    {
+      uint8_t b = x[i];
+
+      gcm_gf_shift_chunk(Z);
+      memxor(Z, table[b & 0xf], GCM_BLOCK_SIZE);
+      gcm_gf_shift_chunk(Z);
+      memxor(Z, table[b >> 4], GCM_BLOCK_SIZE);
+    }
   memcpy (x, Z, sizeof(Z));
 }
+#endif /* GCM_TABLE_BITS == 4 */
+#endif /* GCM_TABLE_BITS */
 
 /* Increment the rightmost 32 bits. */
 #define INC32(block) INCREMENT(4, (block) + GCM_BLOCK_SIZE - 4)
@@ -135,9 +262,20 @@ gcm_set_key(struct gcm_ctx *ctx,
   memset (ctx->h, 0, sizeof (ctx->h));
   f (cipher, GCM_BLOCK_SIZE, ctx->h, ctx->h);  /* H */
 #if GCM_TABLE_BITS
-  /* FIXME: Expand hash subkey */
+#if GCM_TABLE_BITS == 4
+  {
+    unsigned i;
+    for (i = 0; i < 16; i++)
+      {
+       uint8_t x;
+       x = i << 4;
+       gcm_gf_mul(ctx->h_table[i], ctx->h, 1, &x);
+      }
+  }
+#else
   abort();
 #endif
+#endif /* GCM_TABLE_BITS */
 }
 
 /*
@@ -171,12 +309,20 @@ gcm_hash(struct gcm_ctx *ctx, unsigned length, const uint8_t *data)
        length -= GCM_BLOCK_SIZE, data += GCM_BLOCK_SIZE)
     {
       memxor (ctx->x, data, GCM_BLOCK_SIZE);
-      gcm_gf_mul (ctx->x, ctx->h);
+#if GCM_TABLE_BITS
+      gcm_gf_mul_chunk (ctx->x, ctx->h, ctx->h_table);
+#else
+      gcm_gf_mul (ctx->x, ctx->x, GCM_BLOCK_SIZE, ctx->h);
+#endif
     }
   if (length > 0)
     {
       memxor (ctx->x, data, length);
-      gcm_gf_mul (ctx->x, ctx->h);
+#if GCM_TABLE_BITS
+      gcm_gf_mul_chunk (ctx->x, ctx->h, ctx->h_table);
+#else
+      gcm_gf_mul (ctx->x, ctx->x, GCM_BLOCK_SIZE, ctx->h);
+#endif
     }
 }