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Initialize field elements when resulting in infinity #699

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Merged
real-or-random merged 2 commits into from
Sep 9, 2020
Merged

Initialize field elements when resulting in infinity #699

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61d1ecb
Added test with additions resulting in infinity
elichai Dec 10, 2019
47a7b83
Clear field elements when writing infinity
elichai Dec 10, 2019
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6 changes: 3 additions & 3 deletions src/group_impl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -397,7 +397,7 @@ static void secp256k1_gej_add_var(secp256k1_gej *r, const secp256k1_gej *a, cons
if (rzr != NULL) {
secp256k1_fe_set_int(rzr, 0);
}
r->infinity = 1;
secp256k1_gej_set_infinity(r);
}
return;
}
Expand Down Expand Up @@ -447,7 +447,7 @@ static void secp256k1_gej_add_ge_var(secp256k1_gej *r, const secp256k1_gej *a, c
if (rzr != NULL) {
secp256k1_fe_set_int(rzr, 0);
}
r->infinity = 1;
secp256k1_gej_set_infinity(r);
}
return;
}
Expand Down Expand Up @@ -506,7 +506,7 @@ static void secp256k1_gej_add_zinv_var(secp256k1_gej *r, const secp256k1_gej *a,
if (secp256k1_fe_normalizes_to_zero_var(&i)) {
secp256k1_gej_double_var(r, a, NULL);
} else {
r->infinity = 1;
secp256k1_gej_set_infinity(r);
}
return;
}
Expand Down
34 changes: 34 additions & 0 deletions src/tests.c
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Expand Up @@ -2258,6 +2258,39 @@ void test_ge(void) {
free(zinv);
}


void test_intialized_inf(void) {
secp256k1_ge p;
secp256k1_gej pj, npj, infj1, infj2, infj3;
secp256k1_fe zinv;

/* Test that adding P+(-P) results in a fully initalized infinity*/
random_group_element_test(&p);
secp256k1_gej_set_ge(&pj, &p);
secp256k1_gej_neg(&npj, &pj);

secp256k1_gej_add_var(&infj1, &pj, &npj, NULL);
CHECK(secp256k1_gej_is_infinity(&infj1));
CHECK(secp256k1_fe_is_zero(&infj1.x));
CHECK(secp256k1_fe_is_zero(&infj1.y));
CHECK(secp256k1_fe_is_zero(&infj1.z));

secp256k1_gej_add_ge_var(&infj2, &npj, &p, NULL);
CHECK(secp256k1_gej_is_infinity(&infj2));
CHECK(secp256k1_fe_is_zero(&infj2.x));
CHECK(secp256k1_fe_is_zero(&infj2.y));
CHECK(secp256k1_fe_is_zero(&infj2.z));

secp256k1_fe_set_int(&zinv, 1);
secp256k1_gej_add_zinv_var(&infj3, &npj, &p, &zinv);
CHECK(secp256k1_gej_is_infinity(&infj3));
CHECK(secp256k1_fe_is_zero(&infj3.x));
CHECK(secp256k1_fe_is_zero(&infj3.y));
CHECK(secp256k1_fe_is_zero(&infj3.z));


}

void test_add_neg_y_diff_x(void) {
/* The point of this test is to check that we can add two points
* whose y-coordinates are negatives of each other but whose x
Expand Down Expand Up @@ -2331,6 +2364,7 @@ void run_ge(void) {
test_ge();
}
test_add_neg_y_diff_x();
test_intialized_inf();
}

void test_ec_combine(void) {
Expand Down