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generator: verify correctness of point when parsing

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This commit is contained in:
Andrew Poelstra
2018-10-02 16:23:35 +00:00
committed by Tim Ruffing
parent c50b218698
commit fca4c3b62f
3 changed files with 41 additions and 24 deletions
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45
src/modules/generator/main_impl.h
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@@ -15,36 +15,55 @@
#include "scalar.h"
static void secp256k1_generator_load(secp256k1_ge* ge, const secp256k1_generator* gen) {
secp256k1_fe fe;
secp256k1_fe_set_b32(&fe, &gen->data[1]);
secp256k1_ge_set_xquad(ge, &fe);
if (gen->data[0] & 1) {
secp256k1_ge_neg(ge, ge);
}
int succeed;
succeed = secp256k1_fe_set_b32(&ge->x, &gen->data[0]);
VERIFY_CHECK(succeed != 0);
succeed = secp256k1_fe_set_b32(&ge->y, &gen->data[32]);
VERIFY_CHECK(succeed != 0);
ge->infinity = 0;
(void) succeed;
}
static void secp256k1_generator_save(secp256k1_generator* commit, secp256k1_ge* ge) {
secp256k1_fe_normalize(&ge->x);
secp256k1_fe_get_b32(&commit->data[1], &ge->x);
commit->data[0] = 11 ^ secp256k1_fe_is_quad_var(&ge->y);
static void secp256k1_generator_save(secp256k1_generator *gen, secp256k1_ge* ge) {
VERIFY_CHECK(!secp256k1_ge_is_infinity(ge));
secp256k1_fe_normalize_var(&ge->x);
secp256k1_fe_normalize_var(&ge->y);
secp256k1_fe_get_b32(&gen->data[0], &ge->x);
secp256k1_fe_get_b32(&gen->data[32], &ge->y);
}
int secp256k1_generator_parse(const secp256k1_context* ctx, secp256k1_generator* gen, const unsigned char *input) {
secp256k1_fe x;
secp256k1_ge ge;
VERIFY_CHECK(ctx != NULL);
ARG_CHECK(gen != NULL);
ARG_CHECK(input != NULL);
if ((input[0] & 0xFE) != 10) {
if ((input[0] & 0xFE) != 10 ||
!secp256k1_fe_set_b32(&x, &input[1]) ||
!secp256k1_ge_set_xquad(&ge, &x)) {
return 0;
}
memcpy(gen->data, input, sizeof(gen->data));
if (input[0] & 1) {
secp256k1_ge_neg(&ge, &ge);
}
secp256k1_generator_save(gen, &ge);
return 1;
}
int secp256k1_generator_serialize(const secp256k1_context* ctx, unsigned char *output, const secp256k1_generator* gen) {
secp256k1_ge ge;
VERIFY_CHECK(ctx != NULL);
ARG_CHECK(output != NULL);
ARG_CHECK(gen != NULL);
memcpy(output, gen->data, sizeof(gen->data));
secp256k1_generator_load(&ge, gen);
output[0] = 11 ^ secp256k1_fe_is_quad_var(&ge.y);
secp256k1_fe_normalize_var(&ge.x);
secp256k1_fe_get_b32(&output[1], &ge.x);
return 1;
}