_ Git - BearSSL/blob - src/hash/ghash_ctmul.c

   1 /*
   2  * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining
   5  * a copy of this software and associated documentation files (the
   6  * "Software"), to deal in the Software without restriction, including
   7  * without limitation the rights to use, copy, modify, merge, publish,
   8  * distribute, sublicense, and/or sell copies of the Software, and to
   9  * permit persons to whom the Software is furnished to do so, subject to
  10  * the following conditions:
  11  *
  12  * The above copyright notice and this permission notice shall be
  13  * included in all copies or substantial portions of the Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  16  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  17  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  18  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  19  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  20  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  21  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  22  * SOFTWARE.
  23  */
  24
  25 #include "inner.h"
  26
  27 /*
  28  * We compute "carryless multiplications" through normal integer
  29  * multiplications, masking out enough bits to create "holes" in which
  30  * carries may expand without altering our bits; we really use 8 data
  31  * bits per 32-bit word, space every fourth bit. Accumulated carries
  32  * may not exceed 8 in total, which fits in 4 bits.
  33  *
  34  * It would be possible to use a 3-bit spacing, allowing two operands,
  35  * one with 7 non-zero data bits, the other one with 10 or 11 non-zero
  36  * data bits; this asymmetric splitting makes the overall code more
  37  * complex with thresholds and exceptions, and does not appear to be
  38  * worth the effort.
  39  */
  40
  41 /*
  42  * We cannot really autodetect whether multiplications are "slow" or
  43  * not. A typical example is the ARM Cortex M0+, which exists in two
  44  * versions: one with a 1-cycle multiplication opcode, the other with
  45  * a 32-cycle multiplication opcodes. They both use exactly the same
  46  * architecture and ABI, and cannot be distinguished from each other
  47  * at compile-time.
  48  *
  49  * Since most modern CPU (even embedded CPU) still have fast
  50  * multiplications, we use the "fast mul" code by default.
  51  */
  52
  53 #if BR_SLOW_MUL
  54
  55 /*
  56  * This implementation uses Karatsuba-like reduction to make fewer
  57  * integer multiplications (9 instead of 16), at the expense of extra
  58  * logical operations (XOR, shifts...). On modern x86 CPU that offer
  59  * fast, pipelined multiplications, this code is about twice slower than
  60  * the simpler code with 16 multiplications. This tendency may be
  61  * reversed on low-end platforms with expensive multiplications.
  62  */
  63
  64 #define MUL32(h, l, x, y)   do { \
  65                 uint64_t mul32tmp = MUL(x, y); \
  66                 (h) = (uint32_t)(mul32tmp >> 32); \
  67                 (l) = (uint32_t)mul32tmp; \
  68         } while (0)
  69
  70 static inline void
  71 bmul(uint32_t *hi, uint32_t *lo, uint32_t x, uint32_t y)
  72 {
  73         uint32_t x0, x1, x2, x3;
  74         uint32_t y0, y1, y2, y3;
  75         uint32_t a0, a1, a2, a3, a4, a5, a6, a7, a8;
  76         uint32_t b0, b1, b2, b3, b4, b5, b6, b7, b8;
  77
  78         x0 = x & (uint32_t)0x11111111;
  79         x1 = x & (uint32_t)0x22222222;
  80         x2 = x & (uint32_t)0x44444444;
  81         x3 = x & (uint32_t)0x88888888;
  82         y0 = y & (uint32_t)0x11111111;
  83         y1 = y & (uint32_t)0x22222222;
  84         y2 = y & (uint32_t)0x44444444;
  85         y3 = y & (uint32_t)0x88888888;
  86
  87         /*
  88          * (x0+W*x1)*(y0+W*y1) -> a0:b0
  89          * (x2+W*x3)*(y2+W*y3) -> a3:b3
  90          * ((x0+x2)+W*(x1+x3))*((y0+y2)+W*(y1+y3)) -> a6:b6
  91          */
  92         a0 = x0;
  93         b0 = y0;
  94         a1 = x1 >> 1;
  95         b1 = y1 >> 1;
  96         a2 = a0 ^ a1;
  97         b2 = b0 ^ b1;
  98         a3 = x2 >> 2;
  99         b3 = y2 >> 2;
 100         a4 = x3 >> 3;
 101         b4 = y3 >> 3;
 102         a5 = a3 ^ a4;
 103         b5 = b3 ^ b4;
 104         a6 = a0 ^ a3;
 105         b6 = b0 ^ b3;
 106         a7 = a1 ^ a4;
 107         b7 = b1 ^ b4;
 108         a8 = a6 ^ a7;
 109         b8 = b6 ^ b7;
 110
 111         MUL32(b0, a0, b0, a0);
 112         MUL32(b1, a1, b1, a1);
 113         MUL32(b2, a2, b2, a2);
 114         MUL32(b3, a3, b3, a3);
 115         MUL32(b4, a4, b4, a4);
 116         MUL32(b5, a5, b5, a5);
 117         MUL32(b6, a6, b6, a6);
 118         MUL32(b7, a7, b7, a7);
 119         MUL32(b8, a8, b8, a8);
 120
 121         a0 &= (uint32_t)0x11111111;
 122         a1 &= (uint32_t)0x11111111;
 123         a2 &= (uint32_t)0x11111111;
 124         a3 &= (uint32_t)0x11111111;
 125         a4 &= (uint32_t)0x11111111;
 126         a5 &= (uint32_t)0x11111111;
 127         a6 &= (uint32_t)0x11111111;
 128         a7 &= (uint32_t)0x11111111;
 129         a8 &= (uint32_t)0x11111111;
 130         b0 &= (uint32_t)0x11111111;
 131         b1 &= (uint32_t)0x11111111;
 132         b2 &= (uint32_t)0x11111111;
 133         b3 &= (uint32_t)0x11111111;
 134         b4 &= (uint32_t)0x11111111;
 135         b5 &= (uint32_t)0x11111111;
 136         b6 &= (uint32_t)0x11111111;
 137         b7 &= (uint32_t)0x11111111;
 138         b8 &= (uint32_t)0x11111111;
 139
 140         a2 ^= a0 ^ a1;
 141         b2 ^= b0 ^ b1;
 142         a0 ^= (a2 << 1) ^ (a1 << 2);
 143         b0 ^= (b2 << 1) ^ (b1 << 2);
 144         a5 ^= a3 ^ a4;
 145         b5 ^= b3 ^ b4;
 146         a3 ^= (a5 << 1) ^ (a4 << 2);
 147         b3 ^= (b5 << 1) ^ (b4 << 2);
 148         a8 ^= a6 ^ a7;
 149         b8 ^= b6 ^ b7;
 150         a6 ^= (a8 << 1) ^ (a7 << 2);
 151         b6 ^= (b8 << 1) ^ (b7 << 2);
 152         a6 ^= a0 ^ a3;
 153         b6 ^= b0 ^ b3;
 154         *lo = a0 ^ (a6 << 2) ^ (a3 << 4);
 155         *hi = b0 ^ (b6 << 2) ^ (b3 << 4) ^ (a6 >> 30) ^ (a3 >> 28);
 156 }
 157
 158 #else
 159
 160 /*
 161  * Simple multiplication in GF(2)[X], using 16 integer multiplications.
 162  */
 163
 164 static inline void
 165 bmul(uint32_t *hi, uint32_t *lo, uint32_t x, uint32_t y)
 166 {
 167         uint32_t x0, x1, x2, x3;
 168         uint32_t y0, y1, y2, y3;
 169         uint64_t z0, z1, z2, z3;
 170         uint64_t z;
 171
 172         x0 = x & (uint32_t)0x11111111;
 173         x1 = x & (uint32_t)0x22222222;
 174         x2 = x & (uint32_t)0x44444444;
 175         x3 = x & (uint32_t)0x88888888;
 176         y0 = y & (uint32_t)0x11111111;
 177         y1 = y & (uint32_t)0x22222222;
 178         y2 = y & (uint32_t)0x44444444;
 179         y3 = y & (uint32_t)0x88888888;
 180         z0 = MUL(x0, y0) ^ MUL(x1, y3) ^ MUL(x2, y2) ^ MUL(x3, y1);
 181         z1 = MUL(x0, y1) ^ MUL(x1, y0) ^ MUL(x2, y3) ^ MUL(x3, y2);
 182         z2 = MUL(x0, y2) ^ MUL(x1, y1) ^ MUL(x2, y0) ^ MUL(x3, y3);
 183         z3 = MUL(x0, y3) ^ MUL(x1, y2) ^ MUL(x2, y1) ^ MUL(x3, y0);
 184         z0 &= (uint64_t)0x1111111111111111;
 185         z1 &= (uint64_t)0x2222222222222222;
 186         z2 &= (uint64_t)0x4444444444444444;
 187         z3 &= (uint64_t)0x8888888888888888;
 188         z = z0 | z1 | z2 | z3;
 189         *lo = (uint32_t)z;
 190         *hi = (uint32_t)(z >> 32);
 191 }
 192
 193 #endif
 194
 195 /* see bearssl_hash.h */
 196 void
 197 br_ghash_ctmul(void *y, const void *h, const void *data, size_t len)
 198 {
 199         const unsigned char *buf, *hb;
 200         unsigned char *yb;
 201         uint32_t yw[4];
 202         uint32_t hw[4];
 203
 204         buf = data;
 205         yb = y;
 206         hb = h;
 207         yw[3] = br_dec32be(yb);
 208         yw[2] = br_dec32be(yb + 4);
 209         yw[1] = br_dec32be(yb + 8);
 210         yw[0] = br_dec32be(yb + 12);
 211         hw[3] = br_dec32be(hb);
 212         hw[2] = br_dec32be(hb + 4);
 213         hw[1] = br_dec32be(hb + 8);
 214         hw[0] = br_dec32be(hb + 12);
 215         while (len > 0) {
 216                 const unsigned char *src;
 217                 unsigned char tmp[16];
 218                 int i;
 219                 uint32_t a[9], b[9], zw[8];
 220                 uint32_t c0, c1, c2, c3, d0, d1, d2, d3, e0, e1, e2, e3;
 221
 222                 if (len >= 16) {
 223                         src = buf;
 224                         buf += 16;
 225                         len -= 16;
 226                 } else {
 227                         memcpy(tmp, buf, len);
 228                         memset(tmp + len, 0, (sizeof tmp) - len);
 229                         src = tmp;
 230                         len = 0;
 231                 }
 232                 yw[3] ^= br_dec32be(src);
 233                 yw[2] ^= br_dec32be(src + 4);
 234                 yw[1] ^= br_dec32be(src + 8);
 235                 yw[0] ^= br_dec32be(src + 12);
 236
 237                 /*
 238                  * y[0,1]*h[0,1] -> 0..2
 239                  * y[2,3]*h[2,3] -> 3..5
 240                  * (y[0,1]+y[2,3])*(h[0,1]+h[2,3]) -> 6..8
 241                  */
 242                 a[0] = yw[0];
 243                 b[0] = hw[0];
 244                 a[1] = yw[1];
 245                 b[1] = hw[1];
 246                 a[2] = a[0] ^ a[1];
 247                 b[2] = b[0] ^ b[1];
 248
 249                 a[3] = yw[2];
 250                 b[3] = hw[2];
 251                 a[4] = yw[3];
 252                 b[4] = hw[3];
 253                 a[5] = a[3] ^ a[4];
 254                 b[5] = b[3] ^ b[4];
 255
 256                 a[6] = a[0] ^ a[3];
 257                 b[6] = b[0] ^ b[3];
 258                 a[7] = a[1] ^ a[4];
 259                 b[7] = b[1] ^ b[4];
 260                 a[8] = a[6] ^ a[7];
 261                 b[8] = b[6] ^ b[7];
 262
 263                 for (i = 0; i < 9; i ++) {
 264                         bmul(&b[i], &a[i], b[i], a[i]);
 265                 }
 266
 267                 c0 = a[0];
 268                 c1 = b[0] ^ a[2] ^ a[0] ^ a[1];
 269                 c2 = a[1] ^ b[2] ^ b[0] ^ b[1];
 270                 c3 = b[1];
 271                 d0 = a[3];
 272                 d1 = b[3] ^ a[5] ^ a[3] ^ a[4];
 273                 d2 = a[4] ^ b[5] ^ b[3] ^ b[4];
 274                 d3 = b[4];
 275                 e0 = a[6];
 276                 e1 = b[6] ^ a[8] ^ a[6] ^ a[7];
 277                 e2 = a[7] ^ b[8] ^ b[6] ^ b[7];
 278                 e3 = b[7];
 279
 280                 e0 ^= c0 ^ d0;
 281                 e1 ^= c1 ^ d1;
 282                 e2 ^= c2 ^ d2;
 283                 e3 ^= c3 ^ d3;
 284                 c2 ^= e0;
 285                 c3 ^= e1;
 286                 d0 ^= e2;
 287                 d1 ^= e3;
 288
 289                 zw[0] = c0 << 1;
 290                 zw[1] = (c1 << 1) | (c0 >> 31);
 291                 zw[2] = (c2 << 1) | (c1 >> 31);
 292                 zw[3] = (c3 << 1) | (c2 >> 31);
 293                 zw[4] = (d0 << 1) | (c3 >> 31);
 294                 zw[5] = (d1 << 1) | (d0 >> 31);
 295                 zw[6] = (d2 << 1) | (d1 >> 31);
 296                 zw[7] = (d3 << 1) | (d2 >> 31);
 297
 298                 for (i = 0; i < 4; i ++) {
 299                         uint32_t lw;
 300
 301                         lw = zw[i];
 302                         zw[i + 4] ^= lw ^ (lw >> 1) ^ (lw >> 2) ^ (lw >> 7);
 303                         zw[i + 3] ^= (lw << 31) ^ (lw << 30) ^ (lw << 25);
 304                 }
 305                 memcpy(yw, zw + 4, sizeof yw);
 306         }
 307         br_enc32be(yb, yw[3]);
 308         br_enc32be(yb + 4, yw[2]);
 309         br_enc32be(yb + 8, yw[1]);
 310         br_enc32be(yb + 12, yw[0]);
 311 }