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

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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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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) {