frost/secp256k1-zkp
3
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Change exhaustive test groups so they have a point with X=1

Browse Source 
This enables testing overflow is correctly encoded in the recid, and
likely triggers more edge cases.

Also introduce a Sage script to generate the parameters.
This commit is contained in:
Pieter Wuille
2020-09-06 16:46:41 -07:00
parent cec7b18a34
commit b110c106fa
5 changed files with 166 additions and 48 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
src/modules/recovery/tests_exhaustive_impl.h
View File

@@ -25,6 +25,7 @@ void test_exhaustive_recovery_sign(const secp256k1_context *ctx, const secp256k1
unsigned char sk32[32], msg32[32];
int expected_recid;
int recid;
int overflow;
secp256k1_scalar_set_int(&msg, i);
secp256k1_scalar_set_int(&sk, j);
secp256k1_scalar_get_b32(sk32, &sk);
@@ -34,17 +35,18 @@ void test_exhaustive_recovery_sign(const secp256k1_context *ctx, const secp256k1
/* Check directly */
secp256k1_ecdsa_recoverable_signature_load(ctx, &r, &s, &recid, &rsig);
r_from_k(&expected_r, group, k);
r_from_k(&expected_r, group, k, &overflow);
CHECK(r == expected_r);
CHECK((k * s) % EXHAUSTIVE_TEST_ORDER == (i + r * j) % EXHAUSTIVE_TEST_ORDER ||
(k * (EXHAUSTIVE_TEST_ORDER - s)) % EXHAUSTIVE_TEST_ORDER == (i + r * j) % EXHAUSTIVE_TEST_ORDER);
/* The recid's second bit is for conveying overflow (R.x value >= group order).
* In the actual secp256k1 this is an astronomically unlikely event, but in the
* small group used here, it will always be the case.
* small group used here, it will be the case for all points except the ones where
* R.x=1 (which the group is specifically selected to have).
* Note that this isn't actually useful; full recovery would need to convey
* floor(R.x / group_order), but only one bit is used as that is sufficient
* in the real group. */
expected_recid = 2;
expected_recid = overflow ? 2 : 0;
r_dot_y_normalized = group[k].y;
secp256k1_fe_normalize(&r_dot_y_normalized);
/* Also the recovery id is flipped depending if we hit the low-s branch */
@@ -61,7 +63,7 @@ void test_exhaustive_recovery_sign(const secp256k1_context *ctx, const secp256k1
/* Note that we compute expected_r *after* signing -- this is important
* because our nonce-computing function function might change k during
* signing. */
r_from_k(&expected_r, group, k);
r_from_k(&expected_r, group, k, NULL);
CHECK(r == expected_r);
CHECK((k * s) % EXHAUSTIVE_TEST_ORDER == (i + r * j) % EXHAUSTIVE_TEST_ORDER ||
(k * (EXHAUSTIVE_TEST_ORDER - s)) % EXHAUSTIVE_TEST_ORDER == (i + r * j) % EXHAUSTIVE_TEST_ORDER);
@@ -104,7 +106,7 @@ void test_exhaustive_recovery_verify(const secp256k1_context *ctx, const secp256
should_verify = 0;
for (k = 0; k < EXHAUSTIVE_TEST_ORDER; k++) {
secp256k1_scalar check_x_s;
r_from_k(&check_x_s, group, k);
r_from_k(&check_x_s, group, k, NULL);
if (r_s == check_x_s) {
secp256k1_scalar_set_int(&s_times_k_s, k);
secp256k1_scalar_mul(&s_times_k_s, &s_times_k_s, &s_s);