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Add trivial ecmult_multi algorithm. It is selected when no scratch space is given and just multiplies and adds the points.

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Jonas Nick
2018-12-20 20:48:19 +00:00
parent 5545e13dea
commit bade617417
3 changed files with 33 additions and 1 deletions
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30
src/ecmult_impl.h
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@@ -1084,6 +1084,33 @@ static size_t secp256k1_pippenger_max_points(secp256k1_scratch *scratch) {
return res;
}
/* Computes ecmult_multi by simply multiplying and adding each point. Does not
* require a scratch space */
static int secp256k1_ecmult_multi_simple_var(const secp256k1_ecmult_context *ctx, secp256k1_gej *r, const secp256k1_scalar *inp_g_sc, secp256k1_ecmult_multi_callback cb, void *cbdata, size_t n_points) {
size_t point_idx;
secp256k1_scalar szero;
secp256k1_gej tmpj;
secp256k1_scalar_set_int(&szero, 0);
secp256k1_gej_set_infinity(r);
secp256k1_gej_set_infinity(&tmpj);
/* r = inp_g_sc*G */
secp256k1_ecmult(ctx, r, &tmpj, &szero, inp_g_sc);
for (point_idx = 0; point_idx < n_points; point_idx++) {
secp256k1_ge point;
secp256k1_gej pointj;
secp256k1_scalar scalar;
if (!cb(&scalar, &point, point_idx, cbdata)) {
return 0;
}
/* r += scalar*point */
secp256k1_gej_set_ge(&pointj, &point);
secp256k1_ecmult(ctx, &tmpj, &pointj, &scalar, NULL);
secp256k1_gej_add_var(r, r, &tmpj, NULL);
}
return 1;
}
typedef int (*secp256k1_ecmult_multi_func)(const secp256k1_ecmult_context*, secp256k1_scratch*, secp256k1_gej*, const secp256k1_scalar*, secp256k1_ecmult_multi_callback cb, void*, size_t);
static int secp256k1_ecmult_multi_var(const secp256k1_ecmult_context *ctx, secp256k1_scratch *scratch, secp256k1_gej *r, const secp256k1_scalar *inp_g_sc, secp256k1_ecmult_multi_callback cb, void *cbdata, size_t n) {
size_t i;
@@ -1102,6 +1129,9 @@ static int secp256k1_ecmult_multi_var(const secp256k1_ecmult_context *ctx, secp2
secp256k1_ecmult(ctx, r, r, &szero, inp_g_sc);
return 1;
}
if (scratch == NULL) {
return secp256k1_ecmult_multi_simple_var(ctx, r, inp_g_sc, cb, cbdata, n);
}
max_points = secp256k1_pippenger_max_points(scratch);
if (max_points == 0) {