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Use group element storage type in EC multiplications

This commit is contained in:
Pieter Wuille 2015-01-25 00:32:22 -04:00
parent e68d7208ec
commit 41f8455434
1 changed files with 27 additions and 14 deletions
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41
src/ecmult_impl.h
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@ -43,16 +43,21 @@ static void secp256k1_ecmult_table_precomp_gej_var(secp256k1_gej_t *pre, const s
secp256k1_gej_add_var(&pre[i], &d, &pre[i-1]);
}
static void secp256k1_ecmult_table_precomp_ge_var(secp256k1_ge_t *pre, const secp256k1_gej_t *a, int w) {
static void secp256k1_ecmult_table_precomp_ge_storage_var(secp256k1_ge_storage_t *pre, const secp256k1_gej_t *a, int w) {
const int table_size = 1 << (w-2);
secp256k1_gej_t *prej = checked_malloc(sizeof(secp256k1_gej_t) * table_size);
secp256k1_ge_t *prea = checked_malloc(sizeof(secp256k1_ge_t) * table_size);
prej[0] = *a;
secp256k1_gej_t d; secp256k1_gej_double_var(&d, a);
for (int i=1; i<table_size; i++) {
secp256k1_gej_add_var(&prej[i], &d, &prej[i-1]);
}
secp256k1_ge_set_all_gej_var(table_size, pre, prej);
secp256k1_ge_set_all_gej_var(table_size, prea, prej);
for (int i=0; i<table_size; i++) {
secp256k1_ge_to_storage(&pre[i], &prea[i]);
}
free(prej);
free(prea);
}
/** The number of entries a table with precomputed multiples needs to have. */
@ -60,24 +65,32 @@ static void secp256k1_ecmult_table_precomp_ge_var(secp256k1_ge_t *pre, const sec
/** The following two macro retrieves a particular odd multiple from a table
* of precomputed multiples. */
#define ECMULT_TABLE_GET(r,pre,n,w,neg) do { \
#define ECMULT_TABLE_GET_GEJ(r,pre,n,w) do { \
VERIFY_CHECK(((n) & 1) == 1); \
VERIFY_CHECK((n) >= -((1 << ((w)-1)) - 1)); \
VERIFY_CHECK((n) <= ((1 << ((w)-1)) - 1)); \
if ((n) > 0) \
*(r) = (pre)[((n)-1)/2]; \
else \
(neg)((r), &(pre)[(-(n)-1)/2]); \
secp256k1_gej_neg((r), &(pre)[(-(n)-1)/2]); \
} while(0)
#define ECMULT_TABLE_GET_GE_STORAGE(r,pre,n,w) do { \
VERIFY_CHECK(((n) & 1) == 1); \
VERIFY_CHECK((n) >= -((1 << ((w)-1)) - 1)); \
VERIFY_CHECK((n) <= ((1 << ((w)-1)) - 1)); \
if ((n) > 0) \
secp256k1_ge_from_storage((r), &(pre)[((n)-1)/2]); \
else {\
secp256k1_ge_from_storage((r), &(pre)[(-(n)-1)/2]); \
secp256k1_ge_neg((r), (r)); \
} \
} while(0)
#define ECMULT_TABLE_GET_GEJ(r,pre,n,w) ECMULT_TABLE_GET((r),(pre),(n),(w),secp256k1_gej_neg)
#define ECMULT_TABLE_GET_GE(r,pre,n,w) ECMULT_TABLE_GET((r),(pre),(n),(w),secp256k1_ge_neg)
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 */
secp256k1_ge_storage_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 */
secp256k1_ge_storage_t pre_g_128[ECMULT_TABLE_SIZE(WINDOW_G)]; /* odd multiples of 2^128*generator */
#endif
} secp256k1_ecmult_consts_t;
@ -101,9 +114,9 @@ static void secp256k1_ecmult_start(void) {
#endif
/* precompute the tables with odd multiples */
secp256k1_ecmult_table_precomp_ge_var(ret->pre_g, &gj, WINDOW_G);
secp256k1_ecmult_table_precomp_ge_storage_var(ret->pre_g, &gj, WINDOW_G);
#ifdef USE_ENDOMORPHISM
secp256k1_ecmult_table_precomp_ge_var(ret->pre_g_128, &g_128j, WINDOW_G);
secp256k1_ecmult_table_precomp_ge_storage_var(ret->pre_g_128, &g_128j, WINDOW_G);
#endif
/* Set the global pointer to the precomputation table. */
@ -224,11 +237,11 @@ static void secp256k1_ecmult(secp256k1_gej_t *r, const secp256k1_gej_t *a, const
secp256k1_gej_add_var(r, r, &tmpj);
}
if (i < bits_ng_1 && (n = wnaf_ng_1[i])) {
ECMULT_TABLE_GET_GE(&tmpa, c->pre_g, n, WINDOW_G);
ECMULT_TABLE_GET_GE_STORAGE(&tmpa, c->pre_g, n, WINDOW_G);
secp256k1_gej_add_ge_var(r, r, &tmpa);
}
if (i < bits_ng_128 && (n = wnaf_ng_128[i])) {
ECMULT_TABLE_GET_GE(&tmpa, c->pre_g_128, n, WINDOW_G);
ECMULT_TABLE_GET_GE_STORAGE(&tmpa, c->pre_g_128, n, WINDOW_G);
secp256k1_gej_add_ge_var(r, r, &tmpa);
}
#else
@ -237,7 +250,7 @@ static void secp256k1_ecmult(secp256k1_gej_t *r, const secp256k1_gej_t *a, const
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);
ECMULT_TABLE_GET_GE_STORAGE(&tmpa, c->pre_g, n, WINDOW_G);
secp256k1_gej_add_ge_var(r, r, &tmpa);
}
#endif