Skip to content

CT: Declassify sig in test instead of at the end of signing #835

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
mkannwischer wants to merge 1 commit into from
Closed

CT: Declassify sig in test instead of at the end of signing #835

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
8 changes: 4 additions & 4 deletions mldsa/src/sign.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -113,6 +113,10 @@ static int mld_check_pct(uint8_t const pk[MLDSA_CRYPTO_PUBLICKEYBYTES],
}
#endif /* MLD_CONFIG_KEYGEN_PCT_BREAKAGE_TEST */

/* Constant time: Declassify signature as it is considered public in
* verification */
MLD_CT_TESTING_DECLASSIFY(signature, MLDSA_CRYPTO_BYTES);

/* Verify the signature using the (potentially corrupted) public key */
ret = crypto_sign_verify(signature, siglen, message, sizeof(message), NULL, 0,
pk_test);
Expand Down Expand Up @@ -616,10 +620,6 @@ __contract__(
}

/* All is well - write signature */
/* Constant time: At this point it is clear that the signature is valid - it
* can, hence, be considered public. */
MLD_CT_TESTING_DECLASSIFY(h, sizeof(*h));
MLD_CT_TESTING_DECLASSIFY(z, sizeof(*z));
mld_pack_sig(sig, challenge_bytes, z, h, n);

ret = 0; /* success */
Expand Down
26 changes: 26 additions & 0 deletions test/test_mldsa.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,10 @@ static int test_sign_core(uint8_t pk[MLDSA_CRYPTO_PUBLICKEYBYTES],

CHECK(crypto_sign(sm, &smlen, m, MLEN, ctx, CTXLEN, sk) == 0);

/* Constant time: Declassify signature as it is considered public in
* verification */
MLD_CT_TESTING_DECLASSIFY(sm, MLEN + MLDSA_CRYPTO_BYTES);

rc = crypto_sign_open(m2, &mlen, sm, smlen, ctx, CTXLEN, pk);

/* Constant time: Declassify outputs to check them. */
Expand Down Expand Up @@ -120,6 +124,11 @@ static int test_sign_extmu(void)
MLD_CT_TESTING_SECRET(mu, sizeof(mu));

CHECK(crypto_sign_signature_extmu(sig, &siglen, mu, sk) == 0);

/* Constant time: Declassify signature as it is considered public in
* verification */
MLD_CT_TESTING_DECLASSIFY(sig, MLDSA_CRYPTO_BYTES);

CHECK(crypto_sign_verify_extmu(sig, siglen, mu, pk) == 0);

return 0;
Expand Down Expand Up @@ -147,6 +156,11 @@ static int test_sign_pre_hash(void)

CHECK(crypto_sign_signature_pre_hash_shake256(sig, &siglen, m, MLEN, ctx,
CTXLEN, rnd, sk) == 0);

/* Constant time: Declassify signature as it is considered public in
* verification */
MLD_CT_TESTING_DECLASSIFY(sig, MLDSA_CRYPTO_BYTES);

CHECK(crypto_sign_verify_pre_hash_shake256(sig, siglen, m, MLEN, ctx, CTXLEN,
pk) == 0);

Expand Down Expand Up @@ -240,6 +254,10 @@ static int test_wrong_pk(void)

pk[idx] ^= 1;

/* Constant time: Declassify signature as it is considered public in
* verification */
MLD_CT_TESTING_DECLASSIFY(sm, MLEN + MLDSA_CRYPTO_BYTES);

rc = crypto_sign_open(m2, &mlen, sm, smlen, ctx, CTXLEN, pk);

/* Constant time: Declassify outputs to check them. */
Expand Down Expand Up @@ -291,6 +309,10 @@ static int test_wrong_sig(void)

sm[idx] ^= 1;

/* Constant time: Declassify signature as it is considered public in
* verification */
MLD_CT_TESTING_DECLASSIFY(sm, MLEN + MLDSA_CRYPTO_BYTES);

rc = crypto_sign_open(m2, &mlen, sm, smlen, ctx, CTXLEN, pk);

/* Constant time: Declassify outputs to check them. */
Expand Down Expand Up @@ -343,6 +365,10 @@ static int test_wrong_ctx(void)

ctx[idx] ^= 1;

/* Constant time: Declassify signature as it is considered public in
* verification */
MLD_CT_TESTING_DECLASSIFY(sm, MLEN + MLDSA_CRYPTO_BYTES);

rc = crypto_sign_open(m2, &mlen, sm, smlen, ctx, CTXLEN, pk);

/* Constant time: Declassify outputs to check them. */
Expand Down