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Avoid calling keccak_absorb with partial lanes #450

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Avoid calling keccak_absorb with partial lanes #450

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0dd40db
Avoid calling keccak_absorb with partial lanes
bremoran Sep 10, 2025
d868cc1
Fix pos reset, fix linting errors
bremoran Sep 10, 2025
a8d2d6a
Fix after FIPS202 function renaming
mkannwischer Oct 4, 2025
f82f729
Remove contract of mld_shake256_absorb_with_residual
mkannwischer Oct 4, 2025
8184453
Increase CBMC_OBJECT_BITS for this proof to complete.
rod-chapman Oct 4, 2025
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51 changes: 43 additions & 8 deletions mldsa/sign.c
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Original file line number Diff line number Diff line change
Expand Up @@ -231,6 +231,41 @@ int crypto_sign_keypair(uint8_t *pk, uint8_t *sk)
return result;
}

static void mld_shake256_absorb_with_residual(mld_shake256ctx *state,
const uint8_t *in, size_t inlen,
uint8_t *residual, size_t *pos)
{
size_t nb;
if (in)
{
if (*pos)
{
nb = inlen < 8 - *pos ? inlen : 8 - *pos;
memcpy(residual + *pos, in, nb);
inlen -= nb;
in += nb;
*pos += nb;
if (*pos == 8)
{
mld_shake256_absorb(state, residual, 8U);
*pos = 0;
}
}
nb = inlen & ~7UL;
if (nb)
{
mld_shake256_absorb(state, in, nb);
in += nb;
inlen -= nb;
}
if (inlen)
{
memcpy(residual, in, inlen);
*pos = inlen;
}
}
}

/*************************************************
* Name: mld_H
*
Expand Down Expand Up @@ -269,22 +304,22 @@ __contract__(
)
{
mld_shake256ctx state;
uint8_t buf[8];
size_t pos = 0;
mld_shake256_init(&state);
mld_shake256_absorb(&state, in1, in1len);
if (in2 != NULL)
{
mld_shake256_absorb(&state, in2, in2len);
}
if (in3 != NULL)
mld_shake256_absorb_with_residual(&state, in1, in1len, buf, &pos);
mld_shake256_absorb_with_residual(&state, in2, in2len, buf, &pos);
mld_shake256_absorb_with_residual(&state, in3, in3len, buf, &pos);
if (pos)
{
mld_shake256_absorb(&state, in3, in3len);
mld_shake256_absorb(&state, buf, pos);
}
mld_shake256_finalize(&state);
mld_shake256_squeeze(out, outlen, &state);
mld_shake256_release(&state);

/* @[FIPS204, Section 3.6.3] Destruction of intermediate values. */
mld_zeroize(&state, sizeof(state));
mld_zeroize(&buf, sizeof(buf));
}

/* Reference: The reference implementation does not explicitly */
Expand Down
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