Skip to content

sign mem: reuse w/w0 buffer #792

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

sign mem: reuse w/w0 buffer #792

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
4 changes: 2 additions & 2 deletions mldsa/src/native/api.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -268,7 +268,7 @@ static MLD_INLINE int mld_poly_decompose_32_native(int32_t *a1, int32_t *a0,
__contract__(
requires(memory_no_alias(a1, sizeof(int32_t) * MLDSA_N))
requires(memory_no_alias(a0, sizeof(int32_t) * MLDSA_N))
requires(memory_no_alias(a, sizeof(int32_t) * MLDSA_N))
requires(a0 == a || memory_no_alias(a, sizeof(int32_t) * MLDSA_N))
requires(array_bound(a, 0, MLDSA_N, 0, MLDSA_Q))
assigns(memory_slice(a1, sizeof(int32_t) * MLDSA_N))
assigns(memory_slice(a0, sizeof(int32_t) * MLDSA_N))
Expand Down Expand Up @@ -302,7 +302,7 @@ static MLD_INLINE int mld_poly_decompose_88_native(int32_t *a1, int32_t *a0,
__contract__(
requires(memory_no_alias(a1, sizeof(int32_t) * MLDSA_N))
requires(memory_no_alias(a0, sizeof(int32_t) * MLDSA_N))
requires(memory_no_alias(a, sizeof(int32_t) * MLDSA_N))
requires(a0 == a || memory_no_alias(a, sizeof(int32_t) * MLDSA_N))
requires(array_bound(a, 0, MLDSA_N, 0, MLDSA_Q))
assigns(memory_slice(a1, sizeof(int32_t) * MLDSA_N))
assigns(memory_slice(a0, sizeof(int32_t) * MLDSA_N))
Expand Down
4 changes: 3 additions & 1 deletion mldsa/src/poly_kl.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -44,7 +44,7 @@ MLD_STATIC_TESTABLE void mld_poly_decompose_c(mld_poly *a1, mld_poly *a0,
__contract__(
requires(memory_no_alias(a1, sizeof(mld_poly)))
requires(memory_no_alias(a0, sizeof(mld_poly)))
requires(memory_no_alias(a, sizeof(mld_poly)))
requires(a0 == a || memory_no_alias(a, sizeof(mld_poly)))
requires(array_bound(a->coeffs, 0, MLDSA_N, 0, MLDSA_Q))
assigns(memory_slice(a1, sizeof(mld_poly)))
assigns(memory_slice(a0, sizeof(mld_poly)))
Expand All @@ -60,6 +60,8 @@ __contract__(
invariant(i <= MLDSA_N)
invariant(array_bound(a1->coeffs, 0, i, 0, (MLDSA_Q-1)/(2*MLDSA_GAMMA2)))
invariant(array_abs_bound(a0->coeffs, 0, i, MLDSA_GAMMA2+1))
invariant(forall(k1, i, MLDSA_N,
a->coeffs[k1] == loop_entry(*a).coeffs[k1]))
)
{
mld_decompose(&a0->coeffs[i], &a1->coeffs[i], a->coeffs[i]);
Expand Down
2 changes: 1 addition & 1 deletion mldsa/src/poly_kl.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -31,7 +31,7 @@ void mld_poly_decompose(mld_poly *a1, mld_poly *a0, const mld_poly *a)
__contract__(
requires(memory_no_alias(a1, sizeof(mld_poly)))
requires(memory_no_alias(a0, sizeof(mld_poly)))
requires(memory_no_alias(a, sizeof(mld_poly)))
requires(a0 == a || memory_no_alias(a, sizeof(mld_poly)))
requires(array_bound(a->coeffs, 0, MLDSA_N, 0, MLDSA_Q))
assigns(memory_slice(a1, sizeof(mld_poly)))
assigns(memory_slice(a0, sizeof(mld_poly)))
Expand Down
2 changes: 2 additions & 0 deletions mldsa/src/polyvec.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -681,6 +681,8 @@ void mld_polyveck_decompose(mld_polyveck *v1, mld_polyveck *v0,
array_bound(v1->vec[k1].coeffs, 0, MLDSA_N, 0, (MLDSA_Q-1)/(2*MLDSA_GAMMA2))))
invariant(forall(k2, 0, i,
array_abs_bound(v0->vec[k2].coeffs, 0, MLDSA_N, MLDSA_GAMMA2+1)))
invariant(forall(k0, i, MLDSA_K, forall(k1, 0, MLDSA_N,
v->vec[k0].coeffs[k1] == loop_entry(*v).vec[k0].coeffs[k1])))
)
{
mld_poly_decompose(&v1->vec[i], &v0->vec[i], &v->vec[i]);
Expand Down
2 changes: 1 addition & 1 deletion mldsa/src/polyvec.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -484,7 +484,7 @@ void mld_polyveck_decompose(mld_polyveck *v1, mld_polyveck *v0,
__contract__(
requires(memory_no_alias(v1, sizeof(mld_polyveck)))
requires(memory_no_alias(v0, sizeof(mld_polyveck)))
requires(memory_no_alias(v, sizeof(mld_polyveck)))
requires(v0 == v || memory_no_alias(v, sizeof(mld_polyveck)))
Copy link
Contributor

@hanno-becker hanno-becker Dec 16, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Is it worth keeping the non-aliased version, or can we rewrite the code so it uses the aliased version everywhere?

requires(forall(k0, 0, MLDSA_K,
array_bound(v->vec[k0].coeffs, 0, MLDSA_N, 0, MLDSA_Q)))
assigns(memory_slice(v1, sizeof(mld_polyveck)))
Expand Down
35 changes: 21 additions & 14 deletions mldsa/src/sign.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -447,7 +447,15 @@ __contract__(
MLD_ALIGN uint8_t challenge_bytes[MLDSA_CTILDEBYTES];
unsigned int n;
mld_polyvecl y, z;
mld_polyveck w, w1, w0, h;
mld_polyveck w1, h;
union
{
mld_polyveck w;
mld_polyveck w0;
} ww0;
mld_polyveck *w = &ww0.w;
mld_polyveck *w0 = &ww0.w0;

mld_poly cp;
uint32_t z_invalid, w0_invalid, h_invalid;
int res;
Expand All @@ -458,13 +466,13 @@ __contract__(
/* Matrix-vector multiplication */
z = y;
mld_polyvecl_ntt(&z);
mld_polyvec_matrix_pointwise_montgomery(&w, mat, &z);
mld_polyveck_reduce(&w);
mld_polyveck_invntt_tomont(&w);
mld_polyvec_matrix_pointwise_montgomery(w, mat, &z);
mld_polyveck_reduce(w);
mld_polyveck_invntt_tomont(w);

/* Decompose w and call the random oracle */
mld_polyveck_caddq(&w);
mld_polyveck_decompose(&w1, &w0, &w);
mld_polyveck_caddq(w);
mld_polyveck_decompose(&w1, w0, w);
mld_polyveck_pack_w1(sig, &w1);

mld_H(challenge_bytes, MLDSA_CTILDEBYTES, mu, MLDSA_CRHBYTES, sig,
Expand Down Expand Up @@ -505,10 +513,10 @@ __contract__(
* do not reveal secret information */
mld_polyveck_pointwise_poly_montgomery(&h, &cp, s2);
mld_polyveck_invntt_tomont(&h);
mld_polyveck_sub(&w0, &h);
mld_polyveck_reduce(&w0);
mld_polyveck_sub(w0, &h);
mld_polyveck_reduce(w0);

w0_invalid = mld_polyveck_chknorm(&w0, MLDSA_GAMMA2 - MLDSA_BETA);
w0_invalid = mld_polyveck_chknorm(w0, MLDSA_GAMMA2 - MLDSA_BETA);
/* Constant time: w0_invalid may be leaked - see comment for z_invalid. */
MLD_CT_TESTING_DECLASSIFY(&w0_invalid, sizeof(uint32_t));
if (w0_invalid)
Expand All @@ -531,7 +539,7 @@ __contract__(
goto cleanup;
}

mld_polyveck_add(&w0, &h);
mld_polyveck_add(w0, &h);

/* Constant time: At this point all norm checks have passed and we, hence,
* know that the signature does not leak any secret information.
Expand All @@ -541,9 +549,9 @@ __contract__(
* h=c*t0 is public as both c and t0 are public.
* For a more detailed discussion, refer to https://eprint.iacr.org/2022/1406.
*/
MLD_CT_TESTING_DECLASSIFY(&w0, sizeof(w0));
MLD_CT_TESTING_DECLASSIFY(w0, sizeof(mld_polyveck));
MLD_CT_TESTING_DECLASSIFY(&w1, sizeof(w1));
n = mld_polyveck_make_hint(&h, &w0, &w1);
n = mld_polyveck_make_hint(&h, w0, &w1);
if (n > MLDSA_OMEGA)
{
res = -1; /* reject */
Expand All @@ -564,9 +572,8 @@ __contract__(
mld_zeroize(challenge_bytes, MLDSA_CTILDEBYTES);
mld_zeroize(&y, sizeof(y));
mld_zeroize(&z, sizeof(z));
mld_zeroize(&w, sizeof(w));
mld_zeroize(&w1, sizeof(w1));
mld_zeroize(&w0, sizeof(w0));
mld_zeroize(&ww0, sizeof(ww0));
mld_zeroize(&h, sizeof(h));
mld_zeroize(&cp, sizeof(cp));

Expand Down