Page MenuHomePhabricator
Differential D5030 Diff 15727 src/secp256k1/src/ecmult_impl.h

Changeset View

Standalone View

View Options

src/secp256k1/src/ecmult_impl.h

Show All 24 Lines
# define WINDOW_A 4 # define WINDOW_A 4
# define WINDOW_G 4 # define WINDOW_G 4
# else # else
# define WINDOW_A 2 # define WINDOW_A 2
# define WINDOW_G 2 # define WINDOW_G 2
# endif # endif
#else #else
/* optimal for 128-bit and 256-bit exponents. */ /* optimal for 128-bit and 256-bit exponents. */
#define WINDOW_A 5 # define WINDOW_A 5
/** larger numbers may result in slightly better performance, at the cost of /** Larger values for ECMULT_WINDOW_SIZE result in possibly better
exponentially larger precomputed tables. */ * performance at the cost of an exponentially larger precomputed
#ifdef USE_ENDOMORPHISM * table. The exact table size is
/** Two tables for window size 15: 1.375 MiB. */ * (1 << (WINDOW_G - 2)) * sizeof(secp256k1_ge_storage) bytes,
#define WINDOW_G 15 * where sizeof(secp256k1_ge_storage) is typically 64 bytes but can
#else * be larger due to platform-specific padding and alignment.
/** One table for window size 16: 1.375 MiB. */ * If the endomorphism optimization is enabled (USE_ENDOMORMPHSIM)
#define WINDOW_G 16 * two tables of this size are used instead of only one.
*/
# define WINDOW_G ECMULT_WINDOW_SIZE
#endif #endif
/* Noone will ever need more than a window size of 24. The code might
* be correct for larger values of ECMULT_WINDOW_SIZE but this is not
* tested.
*
* The following limitations are known, and there are probably more:
* If WINDOW_G > 27 and size_t has 32 bits, then the code is incorrect
* because the size of the memory object that we allocate (in bytes)
* will not fit in a size_t.
* If WINDOW_G > 31 and int has 32 bits, then the code is incorrect
* because certain expressions will overflow.
*/
#if ECMULT_WINDOW_SIZE < 2 || ECMULT_WINDOW_SIZE > 24
# error Set ECMULT_WINDOW_SIZE to an integer in range [2..24].
#endif #endif
#ifdef USE_ENDOMORPHISM #ifdef USE_ENDOMORPHISM
#define WNAF_BITS 128 #define WNAF_BITS 128
#else #else
#define WNAF_BITS 256 #define WNAF_BITS 256
#endif #endif
#define WNAF_SIZE_BITS(bits, w) (((bits) + (w) - 1) / (w)) #define WNAF_SIZE_BITS(bits, w) (((bits) + (w) - 1) / (w))
▲ Show 20 Lines • Show All 255 Lines • ▼ Show 20 Linesstatic void secp256k1_ecmult_context_build(secp256k1_ecmult_context *ctx, const secp256k1_callback *cb) {
if (ctx->pre_g != NULL) { if (ctx->pre_g != NULL) {
return; return;
} }
/* get the generator */ /* get the generator */
secp256k1_gej_set_ge(&gj, &secp256k1_ge_const_g); secp256k1_gej_set_ge(&gj, &secp256k1_ge_const_g);
ctx->pre_g = (secp256k1_ge_storage (*)[])checked_malloc(cb, sizeof((*ctx->pre_g)[0]) * ECMULT_TABLE_SIZE(WINDOW_G)); {
size_t size = sizeof((*ctx->pre_g)[0]) * ((size_t)ECMULT_TABLE_SIZE(WINDOW_G));
/* check for overflow */
VERIFY_CHECK(size / sizeof((*ctx->pre_g)[0]) == ((size_t)ECMULT_TABLE_SIZE(WINDOW_G)));
ctx->pre_g = (secp256k1_ge_storage (*)[])checked_malloc(cb, size);
}
/* precompute the tables with odd multiples */ /* precompute the tables with odd multiples */
secp256k1_ecmult_odd_multiples_table_storage_var(ECMULT_TABLE_SIZE(WINDOW_G), *ctx->pre_g, &gj); secp256k1_ecmult_odd_multiples_table_storage_var(ECMULT_TABLE_SIZE(WINDOW_G), *ctx->pre_g, &gj);
#ifdef USE_ENDOMORPHISM #ifdef USE_ENDOMORPHISM
{ {
secp256k1_gej g_128j; secp256k1_gej g_128j;
int i; int i;
ctx->pre_g_128 = (secp256k1_ge_storage (*)[])checked_malloc(cb, sizeof((*ctx->pre_g_128)[0]) * ECMULT_TABLE_SIZE(WINDOW_G)); size_t size = sizeof((*ctx->pre_g_128)[0]) * ((size_t) ECMULT_TABLE_SIZE(WINDOW_G));
/* check for overflow */
VERIFY_CHECK(size / sizeof((*ctx->pre_g_128)[0]) == ((size_t)ECMULT_TABLE_SIZE(WINDOW_G)));
ctx->pre_g_128 = (secp256k1_ge_storage (*)[])checked_malloc(cb, size);
/* calculate 2^128*generator */ /* calculate 2^128*generator */
g_128j = gj; g_128j = gj;
for (i = 0; i < 128; i++) { for (i = 0; i < 128; i++) {
secp256k1_gej_double_var(&g_128j, &g_128j, NULL); secp256k1_gej_double_var(&g_128j, &g_128j, NULL);
} }
secp256k1_ecmult_odd_multiples_table_storage_var(ECMULT_TABLE_SIZE(WINDOW_G), *ctx->pre_g_128, &g_128j); secp256k1_ecmult_odd_multiples_table_storage_var(ECMULT_TABLE_SIZE(WINDOW_G), *ctx->pre_g_128, &g_128j);
} }
#endif #endif
} }
static void secp256k1_ecmult_context_clone(secp256k1_ecmult_context *dst, static void secp256k1_ecmult_context_clone(secp256k1_ecmult_context *dst,
const secp256k1_ecmult_context *src, const secp256k1_callback *cb) { const secp256k1_ecmult_context *src, const secp256k1_callback *cb) {
if (src->pre_g == NULL) { if (src->pre_g == NULL) {
dst->pre_g = NULL; dst->pre_g = NULL;
} else { } else {
size_t size = sizeof((*dst->pre_g)[0]) * ECMULT_TABLE_SIZE(WINDOW_G); size_t size = sizeof((*dst->pre_g)[0]) * ((size_t)ECMULT_TABLE_SIZE(WINDOW_G));
dst->pre_g = (secp256k1_ge_storage (*)[])checked_malloc(cb, size); dst->pre_g = (secp256k1_ge_storage (*)[])checked_malloc(cb, size);
memcpy(dst->pre_g, src->pre_g, size); memcpy(dst->pre_g, src->pre_g, size);
} }
#ifdef USE_ENDOMORPHISM #ifdef USE_ENDOMORPHISM
if (src->pre_g_128 == NULL) { if (src->pre_g_128 == NULL) {
dst->pre_g_128 = NULL; dst->pre_g_128 = NULL;
} else { } else {
size_t size = sizeof((*dst->pre_g_128)[0]) * ECMULT_TABLE_SIZE(WINDOW_G); size_t size = sizeof((*dst->pre_g_128)[0]) * ((size_t)ECMULT_TABLE_SIZE(WINDOW_G));
dst->pre_g_128 = (secp256k1_ge_storage (*)[])checked_malloc(cb, size); dst->pre_g_128 = (secp256k1_ge_storage (*)[])checked_malloc(cb, size);
memcpy(dst->pre_g_128, src->pre_g_128, size); memcpy(dst->pre_g_128, src->pre_g_128, size);
} }
#endif #endif
} }
static int secp256k1_ecmult_context_is_built(const secp256k1_ecmult_context *ctx) { static int secp256k1_ecmult_context_is_built(const secp256k1_ecmult_context *ctx) {
return ctx->pre_g != NULL; return ctx->pre_g != NULL;
▲ Show 20 Lines • Show All 826 Lines • Show Last 20 Lines