X-Git-Url: https://git.openssl.org/gitweb/?p=openssl.git;a=blobdiff_plain;f=crypto%2Fec%2Fec_mult.c;h=2ba173ef36422ad1c715fe3ebd5b0dc9b17cb03d;hp=0515e728ec4a1e8c2ff37578b49163ca1a814ada;hb=19f6c524bf78e37ab27cbc53d36655ca709b9675;hpb=48fe4d6233ac2d60745742a27f820dd88bc6689d diff --git a/crypto/ec/ec_mult.c b/crypto/ec/ec_mult.c index 0515e728ec..2ba173ef36 100644 --- a/crypto/ec/ec_mult.c +++ b/crypto/ec/ec_mult.c @@ -1,6 +1,9 @@ /* crypto/ec/ec_mult.c */ +/* + * Originally written by Bodo Moeller and Nils Larsch for the OpenSSL project. + */ /* ==================================================================== - * Copyright (c) 1998-2001 The OpenSSL Project. All rights reserved. + * Copyright (c) 1998-2007 The OpenSSL Project. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions @@ -52,108 +55,552 @@ * Hudson (tjh@cryptsoft.com). * */ +/* ==================================================================== + * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED. + * Portions of this software developed by SUN MICROSYSTEMS, INC., + * and contributed to the OpenSSL project. + */ + +#include #include #include "ec_lcl.h" -/* TODO: width-m NAFs */ +/* + * This file implements the wNAF-based interleaving multi-exponentation method + * (); + * for multiplication with precomputation, we use wNAF splitting + * (). + */ + + + + +/* structure for precomputed multiples of the generator */ +typedef struct ec_pre_comp_st { + const EC_GROUP *group; /* parent EC_GROUP object */ + size_t blocksize; /* block size for wNAF splitting */ + size_t numblocks; /* max. number of blocks for which we have precomputation */ + size_t w; /* window size */ + EC_POINT **points; /* array with pre-calculated multiples of generator: + * 'num' pointers to EC_POINT objects followed by a NULL */ + size_t num; /* numblocks * 2^(w-1) */ + int references; +} EC_PRE_COMP; + +/* functions to manage EC_PRE_COMP within the EC_GROUP extra_data framework */ +static void *ec_pre_comp_dup(void *); +static void ec_pre_comp_free(void *); +static void ec_pre_comp_clear_free(void *); + +static EC_PRE_COMP *ec_pre_comp_new(const EC_GROUP *group) + { + EC_PRE_COMP *ret = NULL; + + if (!group) + return NULL; + + ret = (EC_PRE_COMP *)OPENSSL_malloc(sizeof(EC_PRE_COMP)); + if (!ret) + { + ECerr(EC_F_EC_PRE_COMP_NEW, ERR_R_MALLOC_FAILURE); + return ret; + } + ret->group = group; + ret->blocksize = 8; /* default */ + ret->numblocks = 0; + ret->w = 4; /* default */ + ret->points = NULL; + ret->num = 0; + ret->references = 1; + return ret; + } + +static void *ec_pre_comp_dup(void *src_) + { + EC_PRE_COMP *src = src_; + + /* no need to actually copy, these objects never change! */ + + CRYPTO_add(&src->references, 1, CRYPTO_LOCK_EC_PRE_COMP); + + return src_; + } + +static void ec_pre_comp_free(void *pre_) + { + int i; + EC_PRE_COMP *pre = pre_; + + if (!pre) + return; + + i = CRYPTO_add(&pre->references, -1, CRYPTO_LOCK_EC_PRE_COMP); + if (i > 0) + return; + + if (pre->points) + { + EC_POINT **p; + + for (p = pre->points; *p != NULL; p++) + EC_POINT_free(*p); + OPENSSL_free(pre->points); + } + OPENSSL_free(pre); + } + +static void ec_pre_comp_clear_free(void *pre_) + { + int i; + EC_PRE_COMP *pre = pre_; + + if (!pre) + return; + + i = CRYPTO_add(&pre->references, -1, CRYPTO_LOCK_EC_PRE_COMP); + if (i > 0) + return; + + if (pre->points) + { + EC_POINT **p; + + for (p = pre->points; *p != NULL; p++) + EC_POINT_clear_free(*p); + OPENSSL_cleanse(pre->points, sizeof pre->points); + OPENSSL_free(pre->points); + } + OPENSSL_cleanse(pre, sizeof pre); + OPENSSL_free(pre); + } + + + + +/* Determine the modified width-(w+1) Non-Adjacent Form (wNAF) of 'scalar'. + * This is an array r[] of values that are either zero or odd with an + * absolute value less than 2^w satisfying + * scalar = \sum_j r[j]*2^j + * where at most one of any w+1 consecutive digits is non-zero + * with the exception that the most significant digit may be only + * w-1 zeros away from that next non-zero digit. + */ +static signed char *compute_wNAF(const BIGNUM *scalar, int w, size_t *ret_len) + { + int window_val; + int ok = 0; + signed char *r = NULL; + int sign = 1; + int bit, next_bit, mask; + size_t len = 0, j; + + if (BN_is_zero(scalar)) + { + r = OPENSSL_malloc(1); + if (!r) + { + ECerr(EC_F_COMPUTE_WNAF, ERR_R_MALLOC_FAILURE); + goto err; + } + r[0] = 0; + *ret_len = 1; + return r; + } + + if (w <= 0 || w > 7) /* 'signed char' can represent integers with absolute values less than 2^7 */ + { + ECerr(EC_F_COMPUTE_WNAF, ERR_R_INTERNAL_ERROR); + goto err; + } + bit = 1 << w; /* at most 128 */ + next_bit = bit << 1; /* at most 256 */ + mask = next_bit - 1; /* at most 255 */ + + if (BN_is_negative(scalar)) + { + sign = -1; + } + + len = BN_num_bits(scalar); + r = OPENSSL_malloc(len + 1); /* modified wNAF may be one digit longer than binary representation + * (*ret_len will be set to the actual length, i.e. at most + * BN_num_bits(scalar) + 1) */ + if (r == NULL) + { + ECerr(EC_F_COMPUTE_WNAF, ERR_R_MALLOC_FAILURE); + goto err; + } + + if (scalar->d == NULL || scalar->top == 0) + { + ECerr(EC_F_COMPUTE_WNAF, ERR_R_INTERNAL_ERROR); + goto err; + } + window_val = scalar->d[0] & mask; + j = 0; + while ((window_val != 0) || (j + w + 1 < len)) /* if j+w+1 >= len, window_val will not increase */ + { + int digit = 0; + + /* 0 <= window_val <= 2^(w+1) */ + + if (window_val & 1) + { + /* 0 < window_val < 2^(w+1) */ + + if (window_val & bit) + { + digit = window_val - next_bit; /* -2^w < digit < 0 */ + +#if 1 /* modified wNAF */ + if (j + w + 1 >= len) + { + /* special case for generating modified wNAFs: + * no new bits will be added into window_val, + * so using a positive digit here will decrease + * the total length of the representation */ + + digit = window_val & (mask >> 1); /* 0 < digit < 2^w */ + } +#endif + } + else + { + digit = window_val; /* 0 < digit < 2^w */ + } + + if (digit <= -bit || digit >= bit || !(digit & 1)) + { + ECerr(EC_F_COMPUTE_WNAF, ERR_R_INTERNAL_ERROR); + goto err; + } + + window_val -= digit; + + /* now window_val is 0 or 2^(w+1) in standard wNAF generation; + * for modified window NAFs, it may also be 2^w + */ + if (window_val != 0 && window_val != next_bit && window_val != bit) + { + ECerr(EC_F_COMPUTE_WNAF, ERR_R_INTERNAL_ERROR); + goto err; + } + } + + r[j++] = sign * digit; -/* TODO: optional Lim-Lee precomputation for the generator */ + window_val >>= 1; + window_val += bit * BN_is_bit_set(scalar, j + w); + if (window_val > next_bit) + { + ECerr(EC_F_COMPUTE_WNAF, ERR_R_INTERNAL_ERROR); + goto err; + } + } -/* this is just BN_window_bits_for_exponent_size from bn_lcl.h for now; - * the table should be updated for EC */ /* TODO */ + if (j > len + 1) + { + ECerr(EC_F_COMPUTE_WNAF, ERR_R_INTERNAL_ERROR); + goto err; + } + len = j; + ok = 1; + + err: + if (!ok) + { + OPENSSL_free(r); + r = NULL; + } + if (ok) + *ret_len = len; + return r; + } + + +/* TODO: table should be optimised for the wNAF-based implementation, + * sometimes smaller windows will give better performance + * (thus the boundaries should be increased) + */ #define EC_window_bits_for_scalar_size(b) \ - ((b) > 671 ? 6 : \ - (b) > 239 ? 5 : \ - (b) > 79 ? 4 : \ - (b) > 23 ? 3 : 1) + ((size_t) \ + ((b) >= 2000 ? 6 : \ + (b) >= 800 ? 5 : \ + (b) >= 300 ? 4 : \ + (b) >= 70 ? 3 : \ + (b) >= 20 ? 2 : \ + 1)) /* Compute - * \sum scalar[i]*points[i] - * where + * \sum scalars[i]*points[i], + * also including * scalar*generator - * is included in the addition if scalar != NULL + * in the addition if scalar != NULL */ -int EC_POINTs_mul(const EC_GROUP *group, EC_POINT *r, BIGNUM *scalar, - size_t num, EC_POINT *points[], BIGNUM *scalars[], BN_CTX *ctx) +int ec_wNAF_mul(const EC_GROUP *group, EC_POINT *r, const BIGNUM *scalar, + size_t num, const EC_POINT *points[], const BIGNUM *scalars[], BN_CTX *ctx) { BN_CTX *new_ctx = NULL; - EC_POINT *generator = NULL; + const EC_POINT *generator = NULL; EC_POINT *tmp = NULL; size_t totalnum; + size_t blocksize = 0, numblocks = 0; /* for wNAF splitting */ + size_t pre_points_per_block = 0; size_t i, j; - int k, t; + int k; + int r_is_inverted = 0; int r_is_at_infinity = 1; - size_t max_bits = 0; size_t *wsize = NULL; /* individual window sizes */ - unsigned long *wbits = NULL; /* individual window contents */ - int *wpos = NULL; /* position of bottom bit of current individual windows - * (wpos[i] is valid if wbits[i] != 0) */ + signed char **wNAF = NULL; /* individual wNAFs */ + size_t *wNAF_len = NULL; + size_t max_len = 0; size_t num_val; EC_POINT **val = NULL; /* precomputation */ EC_POINT **v; - EC_POINT ***val_sub = NULL; /* pointers to sub-arrays of 'val' */ + EC_POINT ***val_sub = NULL; /* pointers to sub-arrays of 'val' or 'pre_comp->points' */ + const EC_PRE_COMP *pre_comp = NULL; + int num_scalar = 0; /* flag: will be set to 1 if 'scalar' must be treated like other scalars, + * i.e. precomputation is not available */ int ret = 0; - if (scalar != NULL) + if (group->meth != r->meth) { - generator = EC_GROUP_get0_generator(group); - if (generator == NULL) - { - ECerr(EC_F_EC_POINTS_MUL, EC_R_NO_GENERATOR_SET); - return 0; - } + ECerr(EC_F_EC_WNAF_MUL, EC_R_INCOMPATIBLE_OBJECTS); + return 0; } - + + if ((scalar == NULL) && (num == 0)) + { + return EC_POINT_set_to_infinity(group, r); + } + for (i = 0; i < num; i++) { if (group->meth != points[i]->meth) { - ECerr(EC_F_EC_POINTS_MUL, EC_R_INCOMPATIBLE_OBJECTS); + ECerr(EC_F_EC_WNAF_MUL, EC_R_INCOMPATIBLE_OBJECTS); return 0; } } - totalnum = num + (scalar != NULL); + if (ctx == NULL) + { + ctx = new_ctx = BN_CTX_new(); + if (ctx == NULL) + goto err; + } + + if (scalar != NULL) + { + generator = EC_GROUP_get0_generator(group); + if (generator == NULL) + { + ECerr(EC_F_EC_WNAF_MUL, EC_R_UNDEFINED_GENERATOR); + goto err; + } + + /* look if we can use precomputed multiples of generator */ + + pre_comp = EC_EX_DATA_get_data(group->extra_data, ec_pre_comp_dup, ec_pre_comp_free, ec_pre_comp_clear_free); + + if (pre_comp && pre_comp->numblocks && (EC_POINT_cmp(group, generator, pre_comp->points[0], ctx) == 0)) + { + blocksize = pre_comp->blocksize; + + /* determine maximum number of blocks that wNAF splitting may yield + * (NB: maximum wNAF length is bit length plus one) */ + numblocks = (BN_num_bits(scalar) / blocksize) + 1; - wsize = OPENSSL_malloc(totalnum * sizeof wsize[0]); - wbits = OPENSSL_malloc(totalnum * sizeof wbits[0]); - wpos = OPENSSL_malloc(totalnum * sizeof wpos[0]); - if (wsize == NULL || wbits == NULL || wpos == NULL) goto err; + /* we cannot use more blocks than we have precomputation for */ + if (numblocks > pre_comp->numblocks) + numblocks = pre_comp->numblocks; - /* num_val := total number of points to precompute */ + pre_points_per_block = 1u << (pre_comp->w - 1); + + /* check that pre_comp looks sane */ + if (pre_comp->num != (pre_comp->numblocks * pre_points_per_block)) + { + ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR); + goto err; + } + } + else + { + /* can't use precomputation */ + pre_comp = NULL; + numblocks = 1; + num_scalar = 1; /* treat 'scalar' like 'num'-th element of 'scalars' */ + } + } + + totalnum = num + numblocks; + + wsize = OPENSSL_malloc(totalnum * sizeof wsize[0]); + wNAF_len = OPENSSL_malloc(totalnum * sizeof wNAF_len[0]); + wNAF = OPENSSL_malloc((totalnum + 1) * sizeof wNAF[0]); /* includes space for pivot */ + val_sub = OPENSSL_malloc(totalnum * sizeof val_sub[0]); + + if (!wsize || !wNAF_len || !wNAF || !val_sub) + { + ECerr(EC_F_EC_WNAF_MUL, ERR_R_MALLOC_FAILURE); + goto err; + } + + wNAF[0] = NULL; /* preliminary pivot */ + + /* num_val will be the total number of temporarily precomputed points */ num_val = 0; - for (i = 0; i < totalnum; i++) + + for (i = 0; i < num + num_scalar; i++) { size_t bits; bits = i < num ? BN_num_bits(scalars[i]) : BN_num_bits(scalar); wsize[i] = EC_window_bits_for_scalar_size(bits); - num_val += 1 << (wsize[i] - 1); - if (bits > max_bits) - max_bits = bits; - wbits[i] = 0; - wpos[i] = 0; + num_val += 1u << (wsize[i] - 1); + wNAF[i + 1] = NULL; /* make sure we always have a pivot */ + wNAF[i] = compute_wNAF((i < num ? scalars[i] : scalar), wsize[i], &wNAF_len[i]); + if (wNAF[i] == NULL) + goto err; + if (wNAF_len[i] > max_len) + max_len = wNAF_len[i]; } - /* all precomputed points go into a single array 'val', - * 'val_sub[i]' is a pointer to the subarray for the i-th point */ + if (numblocks) + { + /* we go here iff scalar != NULL */ + + if (pre_comp == NULL) + { + if (num_scalar != 1) + { + ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR); + goto err; + } + /* we have already generated a wNAF for 'scalar' */ + } + else + { + signed char *tmp_wNAF = NULL; + size_t tmp_len = 0; + + if (num_scalar != 0) + { + ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR); + goto err; + } + + /* use the window size for which we have precomputation */ + wsize[num] = pre_comp->w; + tmp_wNAF = compute_wNAF(scalar, wsize[num], &tmp_len); + if (!tmp_wNAF) + goto err; + + if (tmp_len <= max_len) + { + /* One of the other wNAFs is at least as long + * as the wNAF belonging to the generator, + * so wNAF splitting will not buy us anything. */ + + numblocks = 1; + totalnum = num + 1; /* don't use wNAF splitting */ + wNAF[num] = tmp_wNAF; + wNAF[num + 1] = NULL; + wNAF_len[num] = tmp_len; + if (tmp_len > max_len) + max_len = tmp_len; + /* pre_comp->points starts with the points that we need here: */ + val_sub[num] = pre_comp->points; + } + else + { + /* don't include tmp_wNAF directly into wNAF array + * - use wNAF splitting and include the blocks */ + + signed char *pp; + EC_POINT **tmp_points; + + if (tmp_len < numblocks * blocksize) + { + /* possibly we can do with fewer blocks than estimated */ + numblocks = (tmp_len + blocksize - 1) / blocksize; + if (numblocks > pre_comp->numblocks) + { + ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR); + goto err; + } + totalnum = num + numblocks; + } + + /* split wNAF in 'numblocks' parts */ + pp = tmp_wNAF; + tmp_points = pre_comp->points; + + for (i = num; i < totalnum; i++) + { + if (i < totalnum - 1) + { + wNAF_len[i] = blocksize; + if (tmp_len < blocksize) + { + ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR); + goto err; + } + tmp_len -= blocksize; + } + else + /* last block gets whatever is left + * (this could be more or less than 'blocksize'!) */ + wNAF_len[i] = tmp_len; + + wNAF[i + 1] = NULL; + wNAF[i] = OPENSSL_malloc(wNAF_len[i]); + if (wNAF[i] == NULL) + { + ECerr(EC_F_EC_WNAF_MUL, ERR_R_MALLOC_FAILURE); + OPENSSL_free(tmp_wNAF); + goto err; + } + memcpy(wNAF[i], pp, wNAF_len[i]); + if (wNAF_len[i] > max_len) + max_len = wNAF_len[i]; + + if (*tmp_points == NULL) + { + ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR); + OPENSSL_free(tmp_wNAF); + goto err; + } + val_sub[i] = tmp_points; + tmp_points += pre_points_per_block; + pp += blocksize; + } + OPENSSL_free(tmp_wNAF); + } + } + } + + /* All points we precompute now go into a single array 'val'. + * 'val_sub[i]' is a pointer to the subarray for the i-th point, + * or to a subarray of 'pre_comp->points' if we already have precomputation. */ val = OPENSSL_malloc((num_val + 1) * sizeof val[0]); - if (val == NULL) goto err; + if (val == NULL) + { + ECerr(EC_F_EC_WNAF_MUL, ERR_R_MALLOC_FAILURE); + goto err; + } val[num_val] = NULL; /* pivot element */ - val_sub = OPENSSL_malloc(totalnum * sizeof val_sub[0]); - if (val_sub == NULL) goto err; - /* allocate points for precomputation */ v = val; - for (i = 0; i < totalnum; i++) + for (i = 0; i < num + num_scalar; i++) { val_sub[i] = v; - for (j = 0; j < (1 << (wsize[i] - 1)); j++) + for (j = 0; j < (1u << (wsize[i] - 1)); j++) { *v = EC_POINT_new(group); if (*v == NULL) goto err; @@ -162,19 +609,12 @@ int EC_POINTs_mul(const EC_GROUP *group, EC_POINT *r, BIGNUM *scalar, } if (!(v == val + num_val)) { - ECerr(EC_F_EC_POINTS_MUL, ERR_R_INTERNAL_ERROR); + ECerr(EC_F_EC_WNAF_MUL, ERR_R_INTERNAL_ERROR); goto err; } - if (ctx == NULL) - { - ctx = new_ctx = BN_CTX_new(); - if (ctx == NULL) - goto err; - } - - tmp = EC_POINT_new(group); - if (tmp == NULL) goto err; + if (!(tmp = EC_POINT_new(group))) + goto err; /* prepare precomputed values: * val_sub[i][0] := points[i] @@ -182,7 +622,7 @@ int EC_POINTs_mul(const EC_GROUP *group, EC_POINT *r, BIGNUM *scalar, * val_sub[i][2] := 5 * points[i] * ... */ - for (i = 0; i < totalnum; i++) + for (i = 0; i < num + num_scalar; i++) { if (i < num) { @@ -196,20 +636,21 @@ int EC_POINTs_mul(const EC_GROUP *group, EC_POINT *r, BIGNUM *scalar, if (wsize[i] > 1) { if (!EC_POINT_dbl(group, tmp, val_sub[i][0], ctx)) goto err; - for (j = 1; j < (1 << (wsize[i] - 1)); j++) + for (j = 1; j < (1u << (wsize[i] - 1)); j++) { if (!EC_POINT_add(group, val_sub[i][j], val_sub[i][j - 1], tmp, ctx)) goto err; } } } -#if 1 /* optional, maybe we should only do this if total_num > 1 */ - if (!EC_POINTs_make_affine(group, num_val, val, ctx)) goto err; +#if 1 /* optional; EC_window_bits_for_scalar_size assumes we do this step */ + if (!EC_POINTs_make_affine(group, num_val, val, ctx)) + goto err; #endif r_is_at_infinity = 1; - for (k = max_bits - 1; k >= 0; k--) + for (k = max_len - 1; k >= 0; k--) { if (!r_is_at_infinity) { @@ -218,48 +659,52 @@ int EC_POINTs_mul(const EC_GROUP *group, EC_POINT *r, BIGNUM *scalar, for (i = 0; i < totalnum; i++) { - if (wbits[i] == 0) + if (wNAF_len[i] > (size_t)k) { - BIGNUM *s; + int digit = wNAF[i][k]; + int is_neg; - s = i < num ? scalars[i] : scalar; - - if (BN_is_bit_set(s, k)) + if (digit) { - /* look at bits k - wsize[i] + 1 .. k for this window */ - t = k - wsize[i] + 1; - while (!BN_is_bit_set(s, t)) /* BN_is_bit_set is false for t < 0 */ - t++; - wpos[i] = t; - wbits[i] = 1; - for (t = k - 1; t >= wpos[i]; t--) + is_neg = digit < 0; + + if (is_neg) + digit = -digit; + + if (is_neg != r_is_inverted) { - wbits[i] <<= 1; - if (BN_is_bit_set(s, t)) - wbits[i]++; + if (!r_is_at_infinity) + { + if (!EC_POINT_invert(group, r, ctx)) goto err; + } + r_is_inverted = !r_is_inverted; + } + + /* digit > 0 */ + + if (r_is_at_infinity) + { + if (!EC_POINT_copy(r, val_sub[i][digit >> 1])) goto err; + r_is_at_infinity = 0; + } + else + { + if (!EC_POINT_add(group, r, r, val_sub[i][digit >> 1], ctx)) goto err; } - /* now wbits[i] is the odd bit pattern at bits wpos[i] .. k */ - } - } - - if ((wbits[i] != 0) && (wpos[i] == k)) - { - if (r_is_at_infinity) - { - if (!EC_POINT_copy(r, val_sub[i][wbits[i] >> 1])) goto err; - r_is_at_infinity = 0; - } - else - { - if (!EC_POINT_add(group, r, r, val_sub[i][wbits[i] >> 1], ctx)) goto err; } - wbits[i] = 0; } } } if (r_is_at_infinity) + { if (!EC_POINT_set_to_infinity(group, r)) goto err; + } + else + { + if (r_is_inverted) + if (!EC_POINT_invert(group, r, ctx)) goto err; + } ret = 1; @@ -270,10 +715,17 @@ int EC_POINTs_mul(const EC_GROUP *group, EC_POINT *r, BIGNUM *scalar, EC_POINT_free(tmp); if (wsize != NULL) OPENSSL_free(wsize); - if (wbits != NULL) - OPENSSL_free(wbits); - if (wpos != NULL) - OPENSSL_free(wpos); + if (wNAF_len != NULL) + OPENSSL_free(wNAF_len); + if (wNAF != NULL) + { + signed char **w; + + for (w = wNAF; *w != NULL; w++) + OPENSSL_free(*w); + + OPENSSL_free(wNAF); + } if (val != NULL) { for (v = val; *v != NULL; v++) @@ -287,3 +739,200 @@ int EC_POINTs_mul(const EC_GROUP *group, EC_POINT *r, BIGNUM *scalar, } return ret; } + + +/* ec_wNAF_precompute_mult() + * creates an EC_PRE_COMP object with preprecomputed multiples of the generator + * for use with wNAF splitting as implemented in ec_wNAF_mul(). + * + * 'pre_comp->points' is an array of multiples of the generator + * of the following form: + * points[0] = generator; + * points[1] = 3 * generator; + * ... + * points[2^(w-1)-1] = (2^(w-1)-1) * generator; + * points[2^(w-1)] = 2^blocksize * generator; + * points[2^(w-1)+1] = 3 * 2^blocksize * generator; + * ... + * points[2^(w-1)*(numblocks-1)-1] = (2^(w-1)) * 2^(blocksize*(numblocks-2)) * generator + * points[2^(w-1)*(numblocks-1)] = 2^(blocksize*(numblocks-1)) * generator + * ... + * points[2^(w-1)*numblocks-1] = (2^(w-1)) * 2^(blocksize*(numblocks-1)) * generator + * points[2^(w-1)*numblocks] = NULL + */ +int ec_wNAF_precompute_mult(EC_GROUP *group, BN_CTX *ctx) + { + const EC_POINT *generator; + EC_POINT *tmp_point = NULL, *base = NULL, **var; + BN_CTX *new_ctx = NULL; + BIGNUM *order; + size_t i, bits, w, pre_points_per_block, blocksize, numblocks, num; + EC_POINT **points = NULL; + EC_PRE_COMP *pre_comp; + int ret = 0; + + /* if there is an old EC_PRE_COMP object, throw it away */ + EC_EX_DATA_free_data(&group->extra_data, ec_pre_comp_dup, ec_pre_comp_free, ec_pre_comp_clear_free); + + if ((pre_comp = ec_pre_comp_new(group)) == NULL) + return 0; + + generator = EC_GROUP_get0_generator(group); + if (generator == NULL) + { + ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, EC_R_UNDEFINED_GENERATOR); + goto err; + } + + if (ctx == NULL) + { + ctx = new_ctx = BN_CTX_new(); + if (ctx == NULL) + goto err; + } + + BN_CTX_start(ctx); + order = BN_CTX_get(ctx); + if (order == NULL) goto err; + + if (!EC_GROUP_get_order(group, order, ctx)) goto err; + if (BN_is_zero(order)) + { + ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, EC_R_UNKNOWN_ORDER); + goto err; + } + + bits = BN_num_bits(order); + /* The following parameters mean we precompute (approximately) + * one point per bit. + * + * TBD: The combination 8, 4 is perfect for 160 bits; for other + * bit lengths, other parameter combinations might provide better + * efficiency. + */ + blocksize = 8; + w = 4; + if (EC_window_bits_for_scalar_size(bits) > w) + { + /* let's not make the window too small ... */ + w = EC_window_bits_for_scalar_size(bits); + } + + numblocks = (bits + blocksize - 1) / blocksize; /* max. number of blocks to use for wNAF splitting */ + + pre_points_per_block = 1u << (w - 1); + num = pre_points_per_block * numblocks; /* number of points to compute and store */ + + points = OPENSSL_malloc(sizeof (EC_POINT*)*(num + 1)); + if (!points) + { + ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_MALLOC_FAILURE); + goto err; + } + + var = points; + var[num] = NULL; /* pivot */ + for (i = 0; i < num; i++) + { + if ((var[i] = EC_POINT_new(group)) == NULL) + { + ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_MALLOC_FAILURE); + goto err; + } + } + + if (!(tmp_point = EC_POINT_new(group)) || !(base = EC_POINT_new(group))) + { + ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_MALLOC_FAILURE); + goto err; + } + + if (!EC_POINT_copy(base, generator)) + goto err; + + /* do the precomputation */ + for (i = 0; i < numblocks; i++) + { + size_t j; + + if (!EC_POINT_dbl(group, tmp_point, base, ctx)) + goto err; + + if (!EC_POINT_copy(*var++, base)) + goto err; + + for (j = 1; j < pre_points_per_block; j++, var++) + { + /* calculate odd multiples of the current base point */ + if (!EC_POINT_add(group, *var, tmp_point, *(var - 1), ctx)) + goto err; + } + + if (i < numblocks - 1) + { + /* get the next base (multiply current one by 2^blocksize) */ + size_t k; + + if (blocksize <= 2) + { + ECerr(EC_F_EC_WNAF_PRECOMPUTE_MULT, ERR_R_INTERNAL_ERROR); + goto err; + } + + if (!EC_POINT_dbl(group, base, tmp_point, ctx)) + goto err; + for (k = 2; k < blocksize; k++) + { + if (!EC_POINT_dbl(group,base,base,ctx)) + goto err; + } + } + } + + if (!EC_POINTs_make_affine(group, num, points, ctx)) + goto err; + + pre_comp->group = group; + pre_comp->blocksize = blocksize; + pre_comp->numblocks = numblocks; + pre_comp->w = w; + pre_comp->points = points; + points = NULL; + pre_comp->num = num; + + if (!EC_EX_DATA_set_data(&group->extra_data, pre_comp, + ec_pre_comp_dup, ec_pre_comp_free, ec_pre_comp_clear_free)) + goto err; + pre_comp = NULL; + + ret = 1; + err: + if (ctx != NULL) + BN_CTX_end(ctx); + if (new_ctx != NULL) + BN_CTX_free(new_ctx); + if (pre_comp) + ec_pre_comp_free(pre_comp); + if (points) + { + EC_POINT **p; + + for (p = points; *p != NULL; p++) + EC_POINT_free(*p); + OPENSSL_free(points); + } + if (tmp_point) + EC_POINT_free(tmp_point); + if (base) + EC_POINT_free(base); + return ret; + } + + +int ec_wNAF_have_precompute_mult(const EC_GROUP *group) + { + if (EC_EX_DATA_get_data(group->extra_data, ec_pre_comp_dup, ec_pre_comp_free, ec_pre_comp_clear_free) != NULL) + return 1; + else + return 0; + }