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Merge bitcoin-core/secp256k1#1373: Add invariant checking for scalars

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d23da6d557 use secp256k1_scalar_verify checks (stratospher)
c7d0454932 add verification for scalars (stratospher)
ad152151b0 update max scalar in scalar_cmov_test and fix schnorrsig_verify exhaustive test (stratospher)

Pull request description:

  From #1360. This PR:
  1. adds `secp256k1_scalar_verify` to make sure scalars are reduced mod the group order in VERIFY mode
  2. uses `secp256k1_scalar_verify` in all the scalar functions except `secp256k1_scalar_clear`, `secp256k1_scalar_reduce_512`, `secp256k1_scalar_mul_512` and `secp256k1_scalar_*_var` functions in `scalar_low_impl.h`

ACKs for top commit:
  real-or-random:
    utACK d23da6d557
  theStack:
    Code-review ACK d23da6d557

Tree-SHA512: a371b319d948198c4038d35c9ea58f4b94de4dc312215e2b78a323c2acd4ae1355d97935c558b388774832d6d0058b97ff8ca50c3aab40b9ede5307760d0a505
This commit is contained in:
Tim Ruffing
2023-08-18 11:43:29 +02:00
parent 060e32cb60 d23da6d557
commit 0ba2b94551
7 changed files with 241 additions and 24 deletions
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10
src/modules/schnorrsig/tests_exhaustive_impl.h
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@@ -110,15 +110,15 @@ static void test_exhaustive_schnorrsig_verify(const secp256k1_context *ctx, cons
if (!e_done[e]) {
/* Iterate over the possible valid last 32 bytes in the signature.
0..order=that s value; order+1=random bytes */
int count_valid = 0, s;
int count_valid = 0;
unsigned int s;
for (s = 0; s <= EXHAUSTIVE_TEST_ORDER + 1; ++s) {
int expect_valid, valid;
if (s <= EXHAUSTIVE_TEST_ORDER) {
secp256k1_scalar s_s;
secp256k1_scalar_set_int(&s_s, s);
secp256k1_scalar_get_b32(sig64 + 32, &s_s);
memset(sig64 + 32, 0, 32);
secp256k1_write_be32(sig64 + 60, s);
expect_valid = actual_k != -1 && s != EXHAUSTIVE_TEST_ORDER &&
(s_s == (actual_k + actual_d * e) % EXHAUSTIVE_TEST_ORDER);
(s == (actual_k + actual_d * e) % EXHAUSTIVE_TEST_ORDER);
} else {
secp256k1_testrand256(sig64 + 32);
expect_valid = 0;