phantom/bitcoin
1
0
Fork 0
mirror of https://github.com/bitcoin/bitcoin.git synced 2025-01-13 13:22:38 -03:00
Code Issues Projects Releases Packages Wiki Activity Actions

Don't split the g factor when not using endomorphism

Browse source
This commit is contained in:
Pieter Wuille 2014-11-25 14:29:02 +01:00
parent 9431d6b112
commit 665775b2b9
1 changed files with 24 additions and 7 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

31
src/ecmult_impl.h
View file

@ -16,7 +16,11 @@
/** larger numbers may result in slightly better performance, at the cost of
exponentially larger precomputed tables. WINDOW_G == 14 results in 640 KiB. */
#ifdef USE_ENDOMORPHISM
#define WINDOW_G 14
#else
#define WINDOW_G 15
#endif
/** Fill a table 'pre' with precomputed odd multiples of a. W determines the size of the table.
* pre will contains the values [1*a,3*a,5*a,...,(2^(w-1)-1)*a], so it needs place for
@ -69,7 +73,9 @@ static void secp256k1_ecmult_table_precomp_ge_var(secp256k1_ge_t *pre, const sec
typedef struct {
/* For accelerating the computation of a*P + b*G: */
secp256k1_ge_t pre_g[ECMULT_TABLE_SIZE(WINDOW_G)]; /* odd multiples of the generator */
#ifdef USE_ENDOMORPHISM
secp256k1_ge_t pre_g_128[ECMULT_TABLE_SIZE(WINDOW_G)]; /* odd multiples of 2^128*generator */
#endif
} secp256k1_ecmult_consts_t;
static const secp256k1_ecmult_consts_t *secp256k1_ecmult_consts = NULL;
@ -85,14 +91,18 @@ static void secp256k1_ecmult_start(void) {
const secp256k1_ge_t *g = &secp256k1_ge_consts->g;
secp256k1_gej_t gj; secp256k1_gej_set_ge(&gj, g);
#ifdef USE_ENDOMORPHISM
/* calculate 2^128*generator */
secp256k1_gej_t g_128j = gj;
for (int i=0; i<128; i++)
secp256k1_gej_double_var(&g_128j, &g_128j);
#endif
/* precompute the tables with odd multiples */
secp256k1_ecmult_table_precomp_ge_var(ret->pre_g, &gj, WINDOW_G);
#ifdef USE_ENDOMORPHISM
secp256k1_ecmult_table_precomp_ge_var(ret->pre_g_128, &g_128j, WINDOW_G);
#endif
/* Set the global pointer to the precomputation table. */
secp256k1_ecmult_consts = ret;
@ -172,7 +182,6 @@ static void secp256k1_ecmult(secp256k1_gej_t *r, const secp256k1_gej_t *a, const
secp256k1_gej_t pre_a_lam[ECMULT_TABLE_SIZE(WINDOW_A)];
for (int i=0; i<ECMULT_TABLE_SIZE(WINDOW_A); i++)
secp256k1_gej_mul_lambda(&pre_a_lam[i], &pre_a[i]);
#endif
/* Splitted G factors. */
secp256k1_num_t ng_1, ng_128;
@ -185,6 +194,10 @@ static void secp256k1_ecmult(secp256k1_gej_t *r, const secp256k1_gej_t *a, const
int wnaf_ng_128[129]; int bits_ng_128 = secp256k1_ecmult_wnaf(wnaf_ng_128, &ng_128, WINDOW_G);
if (bits_ng_1 > bits) bits = bits_ng_1;
if (bits_ng_128 > bits) bits = bits_ng_128;
#else
int wnaf_ng[257]; int bits_ng = secp256k1_ecmult_wnaf(wnaf_ng, ng, WINDOW_G);
if (bits_ng > bits) bits = bits_ng;
#endif
secp256k1_gej_set_infinity(r);
secp256k1_gej_t tmpj;
@ -202,12 +215,6 @@ static void secp256k1_ecmult(secp256k1_gej_t *r, const secp256k1_gej_t *a, const
ECMULT_TABLE_GET_GEJ(&tmpj, pre_a_lam, n, WINDOW_A);
secp256k1_gej_add_var(r, r, &tmpj);
}
#else
if (i < bits_na && (n = wnaf_na[i])) {
ECMULT_TABLE_GET_GEJ(&tmpj, pre_a, n, WINDOW_A);
secp256k1_gej_add_var(r, r, &tmpj);
}
#endif
if (i < bits_ng_1 && (n = wnaf_ng_1[i])) {
ECMULT_TABLE_GET_GE(&tmpa, c->pre_g, n, WINDOW_G);
secp256k1_gej_add_ge_var(r, r, &tmpa);
@ -216,6 +223,16 @@ static void secp256k1_ecmult(secp256k1_gej_t *r, const secp256k1_gej_t *a, const
ECMULT_TABLE_GET_GE(&tmpa, c->pre_g_128, n, WINDOW_G);
secp256k1_gej_add_ge_var(r, r, &tmpa);
}
#else
if (i < bits_na && (n = wnaf_na[i])) {
ECMULT_TABLE_GET_GEJ(&tmpj, pre_a, n, WINDOW_A);
secp256k1_gej_add_var(r, r, &tmpj);
}
if (i < bits_ng && (n = wnaf_ng[i])) {
ECMULT_TABLE_GET_GE(&tmpa, c->pre_g, n, WINDOW_G);
secp256k1_gej_add_ge_var(r, r, &tmpa);
}
#endif
}
}