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ecmult_gen: Move table creation to new file and force static prec

This commit is contained in:
Tim Ruffing 2021-09-09 16:46:19 +02:00
parent ea5e8a9c47
commit 22dc2c0a0d
7 changed files with 105 additions and 97 deletions
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3
Makefile.am
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@ -28,6 +28,8 @@ noinst_HEADERS += src/ecmult_const.h
noinst_HEADERS += src/ecmult_const_impl.h
noinst_HEADERS += src/ecmult_gen.h
noinst_HEADERS += src/ecmult_gen_impl.h
noinst_HEADERS += src/ecmult_gen_prec.h
noinst_HEADERS += src/ecmult_gen_prec_impl.h
noinst_HEADERS += src/field_10x26.h
noinst_HEADERS += src/field_10x26_impl.h
noinst_HEADERS += src/field_5x52.h
@ -143,6 +145,7 @@ $(gen_context_BIN): $(gen_context_OBJECTS)
$(libsecp256k1_la_OBJECTS): src/ecmult_static_context.h
$(tests_OBJECTS): src/ecmult_static_context.h
$(exhaustive_tests_OBJECTS): src/ecmult_static_context.h
$(bench_internal_OBJECTS): src/ecmult_static_context.h
$(bench_ecmult_OBJECTS): src/ecmult_static_context.h

6
configure.ac
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@ -125,10 +125,8 @@ AC_ARG_ENABLE(exhaustive_tests,
[use_exhaustive_tests=$enableval],
[use_exhaustive_tests=yes])
AC_ARG_ENABLE(ecmult_static_precomputation,
AS_HELP_STRING([--enable-ecmult-static-precomputation],[enable precomputed ecmult table for signing [default=auto]]),
[use_ecmult_static_precomputation=$enableval],
[use_ecmult_static_precomputation=auto])
# Force static precomputation. The code handling this will be removed in a later commit.
use_ecmult_static_precomputation=yes
AC_ARG_ENABLE(module_ecdh,
AS_HELP_STRING([--enable-module-ecdh],[enable ECDH shared secret computation]),

81
src/ecmult_gen_impl.h
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@ -12,92 +12,20 @@
#include "group.h"
#include "ecmult_gen.h"
#include "hash_impl.h"
#ifdef USE_ECMULT_STATIC_PRECOMPUTATION
#include "ecmult_static_context.h"
#endif
#ifndef USE_ECMULT_STATIC_PRECOMPUTATION
static const size_t SECP256K1_ECMULT_GEN_CONTEXT_PREALLOCATED_SIZE = ROUND_TO_ALIGN(sizeof(*((secp256k1_ecmult_gen_context*) NULL)->prec));
#else
static const size_t SECP256K1_ECMULT_GEN_CONTEXT_PREALLOCATED_SIZE = 0;
#endif
static const size_t SECP256K1_ECMULT_GEN_CONTEXT_PREALLOCATED_SIZE = 0;
static void secp256k1_ecmult_gen_context_init(secp256k1_ecmult_gen_context *ctx) {
ctx->prec = NULL;
}
static void secp256k1_ecmult_gen_context_build(secp256k1_ecmult_gen_context *ctx, void **prealloc) {
#ifndef USE_ECMULT_STATIC_PRECOMPUTATION
secp256k1_ge prec[ECMULT_GEN_PREC_N * ECMULT_GEN_PREC_G];
secp256k1_gej gj;
secp256k1_gej nums_gej;
int i, j;
size_t const prealloc_size = SECP256K1_ECMULT_GEN_CONTEXT_PREALLOCATED_SIZE;
void* const base = *prealloc;
#endif
if (ctx->prec != NULL) {
return;
}
#ifndef USE_ECMULT_STATIC_PRECOMPUTATION
ctx->prec = (secp256k1_ge_storage (*)[ECMULT_GEN_PREC_N][ECMULT_GEN_PREC_G])manual_alloc(prealloc, prealloc_size, base, prealloc_size);
/* get the generator */
secp256k1_gej_set_ge(&gj, &secp256k1_ge_const_g);
/* Construct a group element with no known corresponding scalar (nothing up my sleeve). */
{
static const unsigned char nums_b32[33] = "The scalar for this x is unknown";
secp256k1_fe nums_x;
secp256k1_ge nums_ge;
int r;
r = secp256k1_fe_set_b32(&nums_x, nums_b32);
(void)r;
VERIFY_CHECK(r);
r = secp256k1_ge_set_xo_var(&nums_ge, &nums_x, 0);
(void)r;
VERIFY_CHECK(r);
secp256k1_gej_set_ge(&nums_gej, &nums_ge);
/* Add G to make the bits in x uniformly distributed. */
secp256k1_gej_add_ge_var(&nums_gej, &nums_gej, &secp256k1_ge_const_g, NULL);
}
/* compute prec. */
{
secp256k1_gej precj[ECMULT_GEN_PREC_N * ECMULT_GEN_PREC_G]; /* Jacobian versions of prec. */
secp256k1_gej gbase;
secp256k1_gej numsbase;
gbase = gj; /* PREC_G^j * G */
numsbase = nums_gej; /* 2^j * nums. */
for (j = 0; j < ECMULT_GEN_PREC_N; j++) {
/* Set precj[j*PREC_G .. j*PREC_G+(PREC_G-1)] to (numsbase, numsbase + gbase, ..., numsbase + (PREC_G-1)*gbase). */
precj[j*ECMULT_GEN_PREC_G] = numsbase;
for (i = 1; i < ECMULT_GEN_PREC_G; i++) {
secp256k1_gej_add_var(&precj[j*ECMULT_GEN_PREC_G + i], &precj[j*ECMULT_GEN_PREC_G + i - 1], &gbase, NULL);
}
/* Multiply gbase by PREC_G. */
for (i = 0; i < ECMULT_GEN_PREC_B; i++) {
secp256k1_gej_double_var(&gbase, &gbase, NULL);
}
/* Multiply numbase by 2. */
secp256k1_gej_double_var(&numsbase, &numsbase, NULL);
if (j == ECMULT_GEN_PREC_N - 2) {
/* In the last iteration, numsbase is (1 - 2^j) * nums instead. */
secp256k1_gej_neg(&numsbase, &numsbase);
secp256k1_gej_add_var(&numsbase, &numsbase, &nums_gej, NULL);
}
}
secp256k1_ge_set_all_gej_var(prec, precj, ECMULT_GEN_PREC_N * ECMULT_GEN_PREC_G);
}
for (j = 0; j < ECMULT_GEN_PREC_N; j++) {
for (i = 0; i < ECMULT_GEN_PREC_G; i++) {
secp256k1_ge_to_storage(&(*ctx->prec)[j][i], &prec[j*ECMULT_GEN_PREC_G + i]);
}
}
#else
(void)prealloc;
ctx->prec = (secp256k1_ge_storage (*)[ECMULT_GEN_PREC_N][ECMULT_GEN_PREC_G])secp256k1_ecmult_static_context;
#endif
secp256k1_ecmult_gen_blind(ctx, NULL);
}
@ -106,14 +34,7 @@ static int secp256k1_ecmult_gen_context_is_built(const secp256k1_ecmult_gen_cont
}
static void secp256k1_ecmult_gen_context_finalize_memcpy(secp256k1_ecmult_gen_context *dst, const secp256k1_ecmult_gen_context *src) {
#ifndef USE_ECMULT_STATIC_PRECOMPUTATION
if (src->prec != NULL) {
/* We cast to void* first to suppress a -Wcast-align warning. */
dst->prec = (secp256k1_ge_storage (*)[ECMULT_GEN_PREC_N][ECMULT_GEN_PREC_G])(void*)((unsigned char*)dst + ((unsigned char*)src->prec - (unsigned char*)src));
}
#else
(void)dst, (void)src;
#endif
}
static void secp256k1_ecmult_gen_context_clear(secp256k1_ecmult_gen_context *ctx) {

16
src/ecmult_gen_prec.h Normal file
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@ -0,0 +1,16 @@
/***********************************************************************
* Copyright (c) 2013, 2014, 2015 Pieter Wuille, Gregory Maxwell *
* Distributed under the MIT software license, see the accompanying *
* file COPYING or https://www.opensource.org/licenses/mit-license.php.*
***********************************************************************/
#ifndef SECP256K1_ECMULT_GEN_PREC_H
#define SECP256K1_ECMULT_GEN_PREC_H
#include "ecmult_gen.h"
static const size_t ECMULT_GEN_PREC_TABLE_SIZE = ROUND_TO_ALIGN(sizeof(*((secp256k1_ecmult_gen_context*) NULL)->prec));
static void secp256k1_ecmult_gen_create_prec_table(secp256k1_ecmult_gen_context *ctx, void **prealloc);
#endif /* SECP256K1_ECMULT_GEN_PREC_H */

78
src/ecmult_gen_prec_impl.h Normal file
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@ -0,0 +1,78 @@
/***********************************************************************
* Copyright (c) 2013, 2014, 2015 Pieter Wuille, Gregory Maxwell *
* Distributed under the MIT software license, see the accompanying *
* file COPYING or https://www.opensource.org/licenses/mit-license.php.*
***********************************************************************/
#ifndef SECP256K1_ECMULT_GEN_PREC_IMPL_H
#define SECP256K1_ECMULT_GEN_PREC_IMPL_H
#include "ecmult_gen_prec.h"
#include "group_impl.h"
#include "field_impl.h"
#include "ecmult_gen.h"
static void secp256k1_ecmult_gen_create_prec_table(secp256k1_ecmult_gen_context *ctx, void **prealloc) {
secp256k1_ge prec[ECMULT_GEN_PREC_N * ECMULT_GEN_PREC_G];
secp256k1_gej gj;
secp256k1_gej nums_gej;
int i, j;
size_t const prealloc_size = ECMULT_GEN_PREC_TABLE_SIZE;
void* const base = *prealloc;
ctx->prec = (secp256k1_ge_storage (*)[ECMULT_GEN_PREC_N][ECMULT_GEN_PREC_G])manual_alloc(prealloc, prealloc_size, base, prealloc_size);
/* get the generator */
secp256k1_gej_set_ge(&gj, &secp256k1_ge_const_g);
/* Construct a group element with no known corresponding scalar (nothing up my sleeve). */
{
static const unsigned char nums_b32[33] = "The scalar for this x is unknown";
secp256k1_fe nums_x;
secp256k1_ge nums_ge;
int r;
r = secp256k1_fe_set_b32(&nums_x, nums_b32);
(void)r;
VERIFY_CHECK(r);
r = secp256k1_ge_set_xo_var(&nums_ge, &nums_x, 0);
(void)r;
VERIFY_CHECK(r);
secp256k1_gej_set_ge(&nums_gej, &nums_ge);
/* Add G to make the bits in x uniformly distributed. */
secp256k1_gej_add_ge_var(&nums_gej, &nums_gej, &secp256k1_ge_const_g, NULL);
}
/* compute prec. */
{
secp256k1_gej precj[ECMULT_GEN_PREC_N * ECMULT_GEN_PREC_G]; /* Jacobian versions of prec. */
secp256k1_gej gbase;
secp256k1_gej numsbase;
gbase = gj; /* PREC_G^j * G */
numsbase = nums_gej; /* 2^j * nums. */
for (j = 0; j < ECMULT_GEN_PREC_N; j++) {
/* Set precj[j*PREC_G .. j*PREC_G+(PREC_G-1)] to (numsbase, numsbase + gbase, ..., numsbase + (PREC_G-1)*gbase). */
precj[j*ECMULT_GEN_PREC_G] = numsbase;
for (i = 1; i < ECMULT_GEN_PREC_G; i++) {
secp256k1_gej_add_var(&precj[j*ECMULT_GEN_PREC_G + i], &precj[j*ECMULT_GEN_PREC_G + i - 1], &gbase, NULL);
}
/* Multiply gbase by PREC_G. */
for (i = 0; i < ECMULT_GEN_PREC_B; i++) {
secp256k1_gej_double_var(&gbase, &gbase, NULL);
}
/* Multiply numbase by 2. */
secp256k1_gej_double_var(&numsbase, &numsbase, NULL);
if (j == ECMULT_GEN_PREC_N - 2) {
/* In the last iteration, numsbase is (1 - 2^j) * nums instead. */
secp256k1_gej_neg(&numsbase, &numsbase);
secp256k1_gej_add_var(&numsbase, &numsbase, &nums_gej, NULL);
}
}
secp256k1_ge_set_all_gej_var(prec, precj, ECMULT_GEN_PREC_N * ECMULT_GEN_PREC_G);
}
for (j = 0; j < ECMULT_GEN_PREC_N; j++) {
for (i = 0; i < ECMULT_GEN_PREC_G; i++) {
secp256k1_ge_to_storage(&(*ctx->prec)[j][i], &prec[j*ECMULT_GEN_PREC_G + i]);
}
}
}
#endif /* SECP256K1_ECMULT_GEN_PREC_IMPL_H */

16
src/gen_context.c
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@ -10,9 +10,6 @@
#include "libsecp256k1-config.h"
#endif
/* We can't require the precomputed tables when creating them. */
#undef USE_ECMULT_STATIC_PRECOMPUTATION
/* In principle we could use ASM, but this yields only a minor speedup in
build time and it's very complicated. In particular when cross-compiling, we'd
need to build the ASM for the build and the host machine. */
@ -22,10 +19,9 @@
#include "../include/secp256k1.h"
#include "assumptions.h"
#include "util.h"
#include "field_impl.h"
#include "scalar_impl.h"
#include "group_impl.h"
#include "ecmult_gen_impl.h"
#include "group.h"
#include "ecmult_gen.h"
#include "ecmult_gen_prec_impl.h"
static void default_error_callback_fn(const char* str, void* data) {
(void)data;
@ -63,10 +59,9 @@ int main(int argc, char **argv) {
fprintf(fp, "#endif\n");
fprintf(fp, "static const secp256k1_ge_storage secp256k1_ecmult_static_context[ECMULT_GEN_PREC_N][ECMULT_GEN_PREC_G] = {\n");
base = checked_malloc(&default_error_callback, SECP256K1_ECMULT_GEN_CONTEXT_PREALLOCATED_SIZE);
base = checked_malloc(&default_error_callback, ECMULT_GEN_PREC_TABLE_SIZE);
prealloc = base;
secp256k1_ecmult_gen_context_init(&ctx);
secp256k1_ecmult_gen_context_build(&ctx, &prealloc);
secp256k1_ecmult_gen_create_prec_table(&ctx, &prealloc);
for(outer = 0; outer != ECMULT_GEN_PREC_N; outer++) {
fprintf(fp,"{\n");
for(inner = 0; inner != ECMULT_GEN_PREC_G; inner++) {
@ -84,7 +79,6 @@ int main(int argc, char **argv) {
}
}
fprintf(fp,"};\n");
secp256k1_ecmult_gen_context_clear(&ctx);
free(base);
fprintf(fp, "#undef SC\n");

2
src/tests_exhaustive.c
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@ -12,8 +12,6 @@
#include <stdlib.h>
#include <time.h>
#undef USE_ECMULT_STATIC_PRECOMPUTATION
#ifndef EXHAUSTIVE_TEST_ORDER
/* see group_impl.h for allowable values */
#define EXHAUSTIVE_TEST_ORDER 13