ec_mult.c revision 279264
1/* crypto/ec/ec_mult.c */ 2/* 3 * Originally written by Bodo Moeller and Nils Larsch for the OpenSSL project. 4 */ 5/* ==================================================================== 6 * Copyright (c) 1998-2007 The OpenSSL Project. All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in 17 * the documentation and/or other materials provided with the 18 * distribution. 19 * 20 * 3. All advertising materials mentioning features or use of this 21 * software must display the following acknowledgment: 22 * "This product includes software developed by the OpenSSL Project 23 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 24 * 25 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 26 * endorse or promote products derived from this software without 27 * prior written permission. For written permission, please contact 28 * openssl-core@openssl.org. 29 * 30 * 5. Products derived from this software may not be called "OpenSSL" 31 * nor may "OpenSSL" appear in their names without prior written 32 * permission of the OpenSSL Project. 33 * 34 * 6. Redistributions of any form whatsoever must retain the following 35 * acknowledgment: 36 * "This product includes software developed by the OpenSSL Project 37 * for use in the OpenSSL Toolkit (http://www.openssl.org/)" 38 * 39 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 40 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 41 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 42 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 43 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 44 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 45 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 46 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 47 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 48 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 49 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 50 * OF THE POSSIBILITY OF SUCH DAMAGE. 51 * ==================================================================== 52 * 53 * This product includes cryptographic software written by Eric Young 54 * (eay@cryptsoft.com). This product includes software written by Tim 55 * Hudson (tjh@cryptsoft.com). 56 * 57 */ 58/* ==================================================================== 59 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED. 60 * Portions of this software developed by SUN MICROSYSTEMS, INC., 61 * and contributed to the OpenSSL project. 62 */ 63 64#include <string.h> 65 66#include <openssl/err.h> 67 68#include "ec_lcl.h" 69 70 71/* 72 * This file implements the wNAF-based interleaving multi-exponentation method 73 * (<URL:http://www.informatik.tu-darmstadt.de/TI/Mitarbeiter/moeller.html#multiexp>); 74 * for multiplication with precomputation, we use wNAF splitting 75 * (<URL:http://www.informatik.tu-darmstadt.de/TI/Mitarbeiter/moeller.html#fastexp>). 76 */ 77 78 79 80 81/* structure for precomputed multiples of the generator */ 82typedef struct ec_pre_comp_st { 83 const EC_GROUP *group; /* parent EC_GROUP object */ 84 size_t blocksize; /* block size for wNAF splitting */ 85 size_t numblocks; /* max. number of blocks for which we have precomputation */ 86 size_t w; /* window size */ 87 EC_POINT **points; /* array with pre-calculated multiples of generator: 88 * 'num' pointers to EC_POINT objects followed by a NULL */ 89 size_t num; /* numblocks * 2^(w-1) */ 90 int references; 91} EC_PRE_COMP; 92 93/* functions to manage EC_PRE_COMP within the EC_GROUP extra_data framework */ 94static void *ec_pre_comp_dup(void *); 95static void ec_pre_comp_free(void *); 96static void ec_pre_comp_clear_free(void *); 97 98static EC_PRE_COMP *ec_pre_comp_new(const EC_GROUP *group) 99 { 100 EC_PRE_COMP *ret = NULL; 101 102 if (!group) 103 return NULL; 104 105 ret = (EC_PRE_COMP *)OPENSSL_malloc(sizeof(EC_PRE_COMP)); 106 if (!ret) 107 { 108 ECerr(EC_F_EC_PRE_COMP_NEW, ERR_R_MALLOC_FAILURE); 109 return ret; 110 } 111 ret->group = group; 112 ret->blocksize = 8; /* default */ 113 ret->numblocks = 0; 114 ret->w = 4; /* default */ 115 ret->points = NULL; 116 ret->num = 0; 117 ret->references = 1; 118 return ret; 119 } 120 121static void *ec_pre_comp_dup(void *src_) 122 { 123 EC_PRE_COMP *src = src_; 124 125 /* no need to actually copy, these objects never change! */ 126 127 CRYPTO_add(&src->references, 1, CRYPTO_LOCK_EC_PRE_COMP); 128 129 return src_; 130 } 131 132static void ec_pre_comp_free(void *pre_) 133 { 134 int i; 135 EC_PRE_COMP *pre = pre_; 136 137 if (!pre) 138 return; 139 140 i = CRYPTO_add(&pre->references, -1, CRYPTO_LOCK_EC_PRE_COMP); 141 if (i > 0) 142 return; 143 144 if (pre->points) 145 { 146 EC_POINT **p; 147 148 for (p = pre->points; *p != NULL; p++) 149 EC_POINT_free(*p); 150 OPENSSL_free(pre->points); 151 } 152 OPENSSL_free(pre); 153 } 154 155static void ec_pre_comp_clear_free(void *pre_) 156 { 157 int i; 158 EC_PRE_COMP *pre = pre_; 159 160 if (!pre) 161 return; 162 163 i = CRYPTO_add(&pre->references, -1, CRYPTO_LOCK_EC_PRE_COMP); 164 if (i > 0) 165 return; 166 167 if (pre->points) 168 { 169 EC_POINT **p; 170 171 for (p = pre->points; *p != NULL; p++) 172 { 173 EC_POINT_clear_free(*p); 174 OPENSSL_cleanse(p, sizeof *p); 175 } 176 OPENSSL_free(pre->points); 177 } 178 OPENSSL_cleanse(pre, sizeof *pre); 179 OPENSSL_free(pre); 180 } 181 182 183 184 185/* Determine the modified width-(w+1) Non-Adjacent Form (wNAF) of 'scalar'. 186 * This is an array r[] of values that are either zero or odd with an 187 * absolute value less than 2^w satisfying 188 * scalar = \sum_j r[j]*2^j 189 * where at most one of any w+1 consecutive digits is non-zero 190 * with the exception that the most significant digit may be only 191 * w-1 zeros away from that next non-zero digit. 192 */ 193static signed char *compute_wNAF(const BIGNUM *scalar, int w, size_t *ret_len) 194 { 195 int window_val; 196 int ok = 0; 197 signed char *r = NULL; 198 int sign = 1; 199 int bit, next_bit, mask; 200 size_t len = 0, j; 201 202 if (BN_is_zero(scalar)) 203 { 204 r = OPENSSL_malloc(1); 205 if (!r) 206 { 207 ECerr(EC_F_COMPUTE_WNAF, ERR_R_MALLOC_FAILURE); 208 goto err; 209 } 210 r[0] = 0; 211 *ret_len = 1; 212 return r; 213 } 214 215 if (w <= 0 || w > 7) /* 'signed char' can represent integers with absolute values less than 2^7 */ 216 { 217 ECerr(EC_F_COMPUTE_WNAF, ERR_R_INTERNAL_ERROR); 218 goto err; 219 } 220 bit = 1 << w; /* at most 128 */ 221 next_bit = bit << 1; /* at most 256 */ 222 mask = next_bit - 1; /* at most 255 */ 223 224 if (BN_is_negative(scalar)) 225 { 226 sign = -1; 227 } 228 229 if (scalar->d == NULL || scalar->top == 0) 230 { 231 ECerr(EC_F_COMPUTE_WNAF, ERR_R_INTERNAL_ERROR); 232 goto err; 233 } 234 235 len = BN_num_bits(scalar); 236 r = OPENSSL_malloc(len + 1); /* modified wNAF may be one digit longer than binary representation 237 * (*ret_len will be set to the actual length, i.e. at most 238 * BN_num_bits(scalar) + 1) */ 239 if (r == NULL) 240 { 241 ECerr(EC_F_COMPUTE_WNAF, ERR_R_MALLOC_FAILURE); 242 goto err; 243 } 244 window_val = scalar->d[0] & mask; 245 j = 0; 246 while ((window_val != 0) || (j + w + 1 < len)) /* if j+w+1 >= len, window_val will not increase */ 247 { 248 int digit = 0; 249 250 /* 0 <= window_val <= 2^(w+1) */ 251 252 if (window_val & 1) 253 { 254 /* 0 < window_val < 2^(w+1) */ 255 256 if (window_val & bit) 257 { 258 digit = window_val - next_bit; /* -2^w < digit < 0 */ 259 260#if 1 /* modified wNAF */ 261 if (j + w + 1 >= len) 262 { 263 /* special case for generating modified wNAFs: 264 * no new bits will be added into window_val, 265 * so using a positive digit here will decrease 266 * the total length of the representation */ 267 268 digit = window_val & (mask >> 1); /* 0 < digit < 2^w */ 269 } 270#endif 271 } 272 else 273 { 274 digit = window_val; /* 0 < digit < 2^w */ 275 } 276 277 if (digit <= -bit || digit >= bit || !(digit & 1)) 278 { 279 ECerr(EC_F_COMPUTE_WNAF, ERR_R_INTERNAL_ERROR); 280 goto err; 281 } 282 283 window_val -= digit; 284 285 /* now window_val is 0 or 2^(w+1) in standard wNAF generation; 286 * for modified window NAFs, it may also be 2^w 287 */ 288 if (window_val != 0 && window_val != next_bit && window_val != bit) 289 { 290 ECerr(EC_F_COMPUTE_WNAF, ERR_R_INTERNAL_ERROR); 291 goto err; 292 } 293 } 294 295 r[j++] = sign * digit; 296 297 window_val >>= 1; 298 window_val += bit * BN_is_bit_set(scalar, j + w); 299 300 if (window_val > next_bit) 301 { 302 ECerr(EC_F_COMPUTE_WNAF, ERR_R_INTERNAL_ERROR); 303 goto err; 304 } 305 } 306 307 if (j > len + 1) 308 { 309 ECerr(EC_F_COMPUTE_WNAF, ERR_R_INTERNAL_ERROR); 310 goto err; 311 } 312 len = j; 313 ok = 1; 314 315 err: 316 if (!ok) 317 { 318 OPENSSL_free(r); 319 r = NULL; 320 } 321 if (ok) 322 *ret_len = len; 323 return r; 324 } 325 326 327/* TODO: table should be optimised for the wNAF-based implementation, 328 * sometimes smaller windows will give better performance 329 * (thus the boundaries should be increased) 330 */ 331#define EC_window_bits_for_scalar_size(b) \ 332 ((size_t) \ 333 ((b) >= 2000 ? 6 : \ 334 (b) >= 800 ? 5 : \ 335 (b) >= 300 ? 4 : \ 336 (b) >= 70 ? 3 : \ 337 (b) >= 20 ? 2 : \ 338 1)) 339 340/* Compute 341 * \sum scalars[i]*points[i], 342 * also including 343 * scalar*generator 344 * in the addition if scalar != NULL 345 */ 346int ec_wNAF_mul(const EC_GROUP *group, EC_POINT *r, const BIGNUM *scalar, 347 size_t num, const EC_POINT *points[], const BIGNUM *scalars[], BN_CTX *ctx) 348 { 349 BN_CTX *new_ctx = NULL; 350 const EC_POINT *generator = NULL; 351 EC_POINT *tmp = NULL; 352 size_t totalnum; 353 size_t blocksize = 0, numblocks = 0; /* for wNAF splitting */ 354 size_t pre_points_per_block = 0; 355 size_t i, j; 356 int k; 357 int r_is_inverted = 0; 358 int r_is_at_infinity = 1; 359 size_t *wsize = NULL; /* individual window sizes */ 360 signed char **wNAF = NULL; /* individual wNAFs */ 361 size_t *wNAF_len = NULL; 362 size_t max_len = 0; 363 size_t num_val; 364 EC_POINT **val = NULL; /* precomputation */ 365 EC_POINT **v; 366 EC_POINT ***val_sub = NULL; /* pointers to sub-arrays of 'val' or 'pre_comp->points' */ 367 const EC_PRE_COMP *pre_comp = NULL; 368 int num_scalar = 0; /* flag: will be set to 1 if 'scalar' must be treated like other scalars, 369 * i.e. precomputation is not available */ 370 int ret = 0; 371 372 if (group->meth != r->meth) 373 { 374 ECerr(EC_F_EC_WNAF_MUL, EC_R_INCOMPATIBLE_OBJECTS); 375 return 0; 376 } 377 378 if ((scalar == NULL) && (num == 0)) 379 { 380 return EC_POINT_set_to_infinity(group, r); 381 } 382 383 for (i = 0; i < num; i++) 384 { 385 if (group->meth != points[i]->meth) 386 { 387 ECerr(EC_F_EC_WNAF_MUL, EC_R_INCOMPATIBLE_OBJECTS); 388 return 0; 389 } 390 } 391 392 if (ctx == NULL) 393 { 394 ctx = new_ctx = BN_CTX_new(); 395 if (ctx == NULL) 396 goto err; 397 } 398 399 if (scalar != NULL) 400 { 401 generator = EC_GROUP_get0_generator(group); 402 if (generator == NULL) 403 { 404 ECerr(EC_F_EC_WNAF_MUL, EC_R_UNDEFINED_GENERATOR); 405 goto err; 406 } 407 408 /* look if we can use precomputed multiples of generator */ 409 410 pre_comp = EC_EX_DATA_get_data(group->extra_data, ec_pre_comp_dup, ec_pre_comp_free, ec_pre_comp_clear_free); 411 412 if (pre_comp && pre_comp->numblocks && (EC_POINT_cmp(group, generator, pre_comp->points[0], ctx) == 0)) 413 { 414 blocksize = pre_comp->blocksize; 415 416 /* determine maximum number of blocks that wNAF splitting may yield 417 * (NB: maximum wNAF length is bit length plus one) */ 418 numblocks = (BN_num_bits(scalar) / blocksize) + 1; 419 420 /* we cannot use more blocks than we have precomputation for */ 421 if (numblocks > pre_comp->numblocks) 422 numblocks = pre_comp->numblocks; 423 424 pre_points_per_block = (size_t)1 << (pre_comp->w - 1); 425 426 /* check that pre_comp looks sane */ 427 if (pre_comp->num != (pre_comp->numblocks * pre_points_per_block)) 428 { 429 ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR); 430 goto err; 431 } 432 } 433 else 434 { 435 /* can't use precomputation */ 436 pre_comp = NULL; 437 numblocks = 1; 438 num_scalar = 1; /* treat 'scalar' like 'num'-th element of 'scalars' */ 439 } 440 } 441 442 totalnum = num + numblocks; 443 444 wsize = OPENSSL_malloc(totalnum * sizeof wsize[0]); 445 wNAF_len = OPENSSL_malloc(totalnum * sizeof wNAF_len[0]); 446 wNAF = OPENSSL_malloc((totalnum + 1) * sizeof wNAF[0]); /* includes space for pivot */ 447 val_sub = OPENSSL_malloc(totalnum * sizeof val_sub[0]); 448 449 /* Ensure wNAF is initialised in case we end up going to err */ 450 if (wNAF) wNAF[0] = NULL; /* preliminary pivot */ 451 452 if (!wsize || !wNAF_len || !wNAF || !val_sub) 453 { 454 ECerr(EC_F_EC_WNAF_MUL, ERR_R_MALLOC_FAILURE); 455 goto err; 456 } 457 458 /* num_val will be the total number of temporarily precomputed points */ 459 num_val = 0; 460 461 for (i = 0; i < num + num_scalar; i++) 462 { 463 size_t bits; 464 465 bits = i < num ? BN_num_bits(scalars[i]) : BN_num_bits(scalar); 466 wsize[i] = EC_window_bits_for_scalar_size(bits); 467 num_val += (size_t)1 << (wsize[i] - 1); 468 wNAF[i + 1] = NULL; /* make sure we always have a pivot */ 469 wNAF[i] = compute_wNAF((i < num ? scalars[i] : scalar), wsize[i], &wNAF_len[i]); 470 if (wNAF[i] == NULL) 471 goto err; 472 if (wNAF_len[i] > max_len) 473 max_len = wNAF_len[i]; 474 } 475 476 if (numblocks) 477 { 478 /* we go here iff scalar != NULL */ 479 480 if (pre_comp == NULL) 481 { 482 if (num_scalar != 1) 483 { 484 ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR); 485 goto err; 486 } 487 /* we have already generated a wNAF for 'scalar' */ 488 } 489 else 490 { 491 signed char *tmp_wNAF = NULL; 492 size_t tmp_len = 0; 493 494 if (num_scalar != 0) 495 { 496 ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR); 497 goto err; 498 } 499 500 /* use the window size for which we have precomputation */ 501 wsize[num] = pre_comp->w; 502 tmp_wNAF = compute_wNAF(scalar, wsize[num], &tmp_len); 503 if (!tmp_wNAF) 504 goto err; 505 506 if (tmp_len <= max_len) 507 { 508 /* One of the other wNAFs is at least as long 509 * as the wNAF belonging to the generator, 510 * so wNAF splitting will not buy us anything. */ 511 512 numblocks = 1; 513 totalnum = num + 1; /* don't use wNAF splitting */ 514 wNAF[num] = tmp_wNAF; 515 wNAF[num + 1] = NULL; 516 wNAF_len[num] = tmp_len; 517 if (tmp_len > max_len) 518 max_len = tmp_len; 519 /* pre_comp->points starts with the points that we need here: */ 520 val_sub[num] = pre_comp->points; 521 } 522 else 523 { 524 /* don't include tmp_wNAF directly into wNAF array 525 * - use wNAF splitting and include the blocks */ 526 527 signed char *pp; 528 EC_POINT **tmp_points; 529 530 if (tmp_len < numblocks * blocksize) 531 { 532 /* possibly we can do with fewer blocks than estimated */ 533 numblocks = (tmp_len + blocksize - 1) / blocksize; 534 if (numblocks > pre_comp->numblocks) 535 { 536 ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR); 537 goto err; 538 } 539 totalnum = num + numblocks; 540 } 541 542 /* split wNAF in 'numblocks' parts */ 543 pp = tmp_wNAF; 544 tmp_points = pre_comp->points; 545 546 for (i = num; i < totalnum; i++) 547 { 548 if (i < totalnum - 1) 549 { 550 wNAF_len[i] = blocksize; 551 if (tmp_len < blocksize) 552 { 553 ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR); 554 goto err; 555 } 556 tmp_len -= blocksize; 557 } 558 else 559 /* last block gets whatever is left 560 * (this could be more or less than 'blocksize'!) */ 561 wNAF_len[i] = tmp_len; 562 563 wNAF[i + 1] = NULL; 564 wNAF[i] = OPENSSL_malloc(wNAF_len[i]); 565 if (wNAF[i] == NULL) 566 { 567 ECerr(EC_F_EC_WNAF_MUL, ERR_R_MALLOC_FAILURE); 568 OPENSSL_free(tmp_wNAF); 569 goto err; 570 } 571 memcpy(wNAF[i], pp, wNAF_len[i]); 572 if (wNAF_len[i] > max_len) 573 max_len = wNAF_len[i]; 574 575 if (*tmp_points == NULL) 576 { 577 ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR); 578 OPENSSL_free(tmp_wNAF); 579 goto err; 580 } 581 val_sub[i] = tmp_points; 582 tmp_points += pre_points_per_block; 583 pp += blocksize; 584 } 585 OPENSSL_free(tmp_wNAF); 586 } 587 } 588 } 589 590 /* All points we precompute now go into a single array 'val'. 591 * 'val_sub[i]' is a pointer to the subarray for the i-th point, 592 * or to a subarray of 'pre_comp->points' if we already have precomputation. */ 593 val = OPENSSL_malloc((num_val + 1) * sizeof val[0]); 594 if (val == NULL) 595 { 596 ECerr(EC_F_EC_WNAF_MUL, ERR_R_MALLOC_FAILURE); 597 goto err; 598 } 599 val[num_val] = NULL; /* pivot element */ 600 601 /* allocate points for precomputation */ 602 v = val; 603 for (i = 0; i < num + num_scalar; i++) 604 { 605 val_sub[i] = v; 606 for (j = 0; j < ((size_t)1 << (wsize[i] - 1)); j++) 607 { 608 *v = EC_POINT_new(group); 609 if (*v == NULL) goto err; 610 v++; 611 } 612 } 613 if (!(v == val + num_val)) 614 { 615 ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR); 616 goto err; 617 } 618 619 if (!(tmp = EC_POINT_new(group))) 620 goto err; 621 622 /* prepare precomputed values: 623 * val_sub[i][0] := points[i] 624 * val_sub[i][1] := 3 * points[i] 625 * val_sub[i][2] := 5 * points[i] 626 * ... 627 */ 628 for (i = 0; i < num + num_scalar; i++) 629 { 630 if (i < num) 631 { 632 if (!EC_POINT_copy(val_sub[i][0], points[i])) goto err; 633 } 634 else 635 { 636 if (!EC_POINT_copy(val_sub[i][0], generator)) goto err; 637 } 638 639 if (wsize[i] > 1) 640 { 641 if (!EC_POINT_dbl(group, tmp, val_sub[i][0], ctx)) goto err; 642 for (j = 1; j < ((size_t)1 << (wsize[i] - 1)); j++) 643 { 644 if (!EC_POINT_add(group, val_sub[i][j], val_sub[i][j - 1], tmp, ctx)) goto err; 645 } 646 } 647 } 648 649#if 1 /* optional; EC_window_bits_for_scalar_size assumes we do this step */ 650 if (!EC_POINTs_make_affine(group, num_val, val, ctx)) 651 goto err; 652#endif 653 654 r_is_at_infinity = 1; 655 656 for (k = max_len - 1; k >= 0; k--) 657 { 658 if (!r_is_at_infinity) 659 { 660 if (!EC_POINT_dbl(group, r, r, ctx)) goto err; 661 } 662 663 for (i = 0; i < totalnum; i++) 664 { 665 if (wNAF_len[i] > (size_t)k) 666 { 667 int digit = wNAF[i][k]; 668 int is_neg; 669 670 if (digit) 671 { 672 is_neg = digit < 0; 673 674 if (is_neg) 675 digit = -digit; 676 677 if (is_neg != r_is_inverted) 678 { 679 if (!r_is_at_infinity) 680 { 681 if (!EC_POINT_invert(group, r, ctx)) goto err; 682 } 683 r_is_inverted = !r_is_inverted; 684 } 685 686 /* digit > 0 */ 687 688 if (r_is_at_infinity) 689 { 690 if (!EC_POINT_copy(r, val_sub[i][digit >> 1])) goto err; 691 r_is_at_infinity = 0; 692 } 693 else 694 { 695 if (!EC_POINT_add(group, r, r, val_sub[i][digit >> 1], ctx)) goto err; 696 } 697 } 698 } 699 } 700 } 701 702 if (r_is_at_infinity) 703 { 704 if (!EC_POINT_set_to_infinity(group, r)) goto err; 705 } 706 else 707 { 708 if (r_is_inverted) 709 if (!EC_POINT_invert(group, r, ctx)) goto err; 710 } 711 712 ret = 1; 713 714 err: 715 if (new_ctx != NULL) 716 BN_CTX_free(new_ctx); 717 if (tmp != NULL) 718 EC_POINT_free(tmp); 719 if (wsize != NULL) 720 OPENSSL_free(wsize); 721 if (wNAF_len != NULL) 722 OPENSSL_free(wNAF_len); 723 if (wNAF != NULL) 724 { 725 signed char **w; 726 727 for (w = wNAF; *w != NULL; w++) 728 OPENSSL_free(*w); 729 730 OPENSSL_free(wNAF); 731 } 732 if (val != NULL) 733 { 734 for (v = val; *v != NULL; v++) 735 EC_POINT_clear_free(*v); 736 737 OPENSSL_free(val); 738 } 739 if (val_sub != NULL) 740 { 741 OPENSSL_free(val_sub); 742 } 743 return ret; 744 } 745 746 747/* ec_wNAF_precompute_mult() 748 * creates an EC_PRE_COMP object with preprecomputed multiples of the generator 749 * for use with wNAF splitting as implemented in ec_wNAF_mul(). 750 * 751 * 'pre_comp->points' is an array of multiples of the generator 752 * of the following form: 753 * points[0] = generator; 754 * points[1] = 3 * generator; 755 * ... 756 * points[2^(w-1)-1] = (2^(w-1)-1) * generator; 757 * points[2^(w-1)] = 2^blocksize * generator; 758 * points[2^(w-1)+1] = 3 * 2^blocksize * generator; 759 * ... 760 * points[2^(w-1)*(numblocks-1)-1] = (2^(w-1)) * 2^(blocksize*(numblocks-2)) * generator 761 * points[2^(w-1)*(numblocks-1)] = 2^(blocksize*(numblocks-1)) * generator 762 * ... 763 * points[2^(w-1)*numblocks-1] = (2^(w-1)) * 2^(blocksize*(numblocks-1)) * generator 764 * points[2^(w-1)*numblocks] = NULL 765 */ 766int ec_wNAF_precompute_mult(EC_GROUP *group, BN_CTX *ctx) 767 { 768 const EC_POINT *generator; 769 EC_POINT *tmp_point = NULL, *base = NULL, **var; 770 BN_CTX *new_ctx = NULL; 771 BIGNUM *order; 772 size_t i, bits, w, pre_points_per_block, blocksize, numblocks, num; 773 EC_POINT **points = NULL; 774 EC_PRE_COMP *pre_comp; 775 int ret = 0; 776 777 /* if there is an old EC_PRE_COMP object, throw it away */ 778 EC_EX_DATA_free_data(&group->extra_data, ec_pre_comp_dup, ec_pre_comp_free, ec_pre_comp_clear_free); 779 780 if ((pre_comp = ec_pre_comp_new(group)) == NULL) 781 return 0; 782 783 generator = EC_GROUP_get0_generator(group); 784 if (generator == NULL) 785 { 786 ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, EC_R_UNDEFINED_GENERATOR); 787 goto err; 788 } 789 790 if (ctx == NULL) 791 { 792 ctx = new_ctx = BN_CTX_new(); 793 if (ctx == NULL) 794 goto err; 795 } 796 797 BN_CTX_start(ctx); 798 order = BN_CTX_get(ctx); 799 if (order == NULL) goto err; 800 801 if (!EC_GROUP_get_order(group, order, ctx)) goto err; 802 if (BN_is_zero(order)) 803 { 804 ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, EC_R_UNKNOWN_ORDER); 805 goto err; 806 } 807 808 bits = BN_num_bits(order); 809 /* The following parameters mean we precompute (approximately) 810 * one point per bit. 811 * 812 * TBD: The combination 8, 4 is perfect for 160 bits; for other 813 * bit lengths, other parameter combinations might provide better 814 * efficiency. 815 */ 816 blocksize = 8; 817 w = 4; 818 if (EC_window_bits_for_scalar_size(bits) > w) 819 { 820 /* let's not make the window too small ... */ 821 w = EC_window_bits_for_scalar_size(bits); 822 } 823 824 numblocks = (bits + blocksize - 1) / blocksize; /* max. number of blocks to use for wNAF splitting */ 825 826 pre_points_per_block = (size_t)1 << (w - 1); 827 num = pre_points_per_block * numblocks; /* number of points to compute and store */ 828 829 points = OPENSSL_malloc(sizeof (EC_POINT*)*(num + 1)); 830 if (!points) 831 { 832 ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_MALLOC_FAILURE); 833 goto err; 834 } 835 836 var = points; 837 var[num] = NULL; /* pivot */ 838 for (i = 0; i < num; i++) 839 { 840 if ((var[i] = EC_POINT_new(group)) == NULL) 841 { 842 ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_MALLOC_FAILURE); 843 goto err; 844 } 845 } 846 847 if (!(tmp_point = EC_POINT_new(group)) || !(base = EC_POINT_new(group))) 848 { 849 ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_MALLOC_FAILURE); 850 goto err; 851 } 852 853 if (!EC_POINT_copy(base, generator)) 854 goto err; 855 856 /* do the precomputation */ 857 for (i = 0; i < numblocks; i++) 858 { 859 size_t j; 860 861 if (!EC_POINT_dbl(group, tmp_point, base, ctx)) 862 goto err; 863 864 if (!EC_POINT_copy(*var++, base)) 865 goto err; 866 867 for (j = 1; j < pre_points_per_block; j++, var++) 868 { 869 /* calculate odd multiples of the current base point */ 870 if (!EC_POINT_add(group, *var, tmp_point, *(var - 1), ctx)) 871 goto err; 872 } 873 874 if (i < numblocks - 1) 875 { 876 /* get the next base (multiply current one by 2^blocksize) */ 877 size_t k; 878 879 if (blocksize <= 2) 880 { 881 ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_INTERNAL_ERROR); 882 goto err; 883 } 884 885 if (!EC_POINT_dbl(group, base, tmp_point, ctx)) 886 goto err; 887 for (k = 2; k < blocksize; k++) 888 { 889 if (!EC_POINT_dbl(group,base,base,ctx)) 890 goto err; 891 } 892 } 893 } 894 895 if (!EC_POINTs_make_affine(group, num, points, ctx)) 896 goto err; 897 898 pre_comp->group = group; 899 pre_comp->blocksize = blocksize; 900 pre_comp->numblocks = numblocks; 901 pre_comp->w = w; 902 pre_comp->points = points; 903 points = NULL; 904 pre_comp->num = num; 905 906 if (!EC_EX_DATA_set_data(&group->extra_data, pre_comp, 907 ec_pre_comp_dup, ec_pre_comp_free, ec_pre_comp_clear_free)) 908 goto err; 909 pre_comp = NULL; 910 911 ret = 1; 912 err: 913 if (ctx != NULL) 914 BN_CTX_end(ctx); 915 if (new_ctx != NULL) 916 BN_CTX_free(new_ctx); 917 if (pre_comp) 918 ec_pre_comp_free(pre_comp); 919 if (points) 920 { 921 EC_POINT **p; 922 923 for (p = points; *p != NULL; p++) 924 EC_POINT_free(*p); 925 OPENSSL_free(points); 926 } 927 if (tmp_point) 928 EC_POINT_free(tmp_point); 929 if (base) 930 EC_POINT_free(base); 931 return ret; 932 } 933 934 935int ec_wNAF_have_precompute_mult(const EC_GROUP *group) 936 { 937 if (EC_EX_DATA_get_data(group->extra_data, ec_pre_comp_dup, ec_pre_comp_free, ec_pre_comp_clear_free) != NULL) 938 return 1; 939 else 940 return 0; 941 } 942