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bignum_mod_raw: Adjusted OPT_RED limb size requirements for mod_raw_mul().

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Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
This commit is contained in:
Minos Galanakis 2023-06-25 20:56:59 +01:00
parent a984d77f3a
commit c7408a432e
1 changed files with 13 additions and 6 deletions
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19
library/bignum_mod_raw.c
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@ -130,18 +130,25 @@ void mbedtls_mpi_mod_raw_mul(mbedtls_mpi_uint *X,
const mbedtls_mpi_mod_modulus *N,
mbedtls_mpi_uint *T)
{
const size_t T_limbs = (N->limbs * 2);
/* Standard (A * B) multiplication stored into pre-allocated T
* buffer of fixed limb size of (2N + 1).
* The space may not not fully filled by when
* MBEDTLS_MPI_MOD_REP_OPT_RED is used, with most
* curves using (2N) limbs.
*
* The 521-bit Weierstrass curve is the only
* that which requires a limb size of (2N + 1). */
const size_t T_limbs = (N->bits == 521) ?
BITS_TO_LIMBS(N->bits * 2) + 1 :
BITS_TO_LIMBS(N->bits * 2);
switch (N->int_rep) {
case MBEDTLS_MPI_MOD_REP_MONTGOMERY:
mbedtls_mpi_core_montmul(X, A, B, N->limbs, N->p, N->limbs,
N->rep.mont.mm, T);
break;
case MBEDTLS_MPI_MOD_REP_OPT_RED:
/* Standard (A * B) multiplication stored into pre-allocated T
* buffer of fixed size of ((2N + 1) * ciL) bytes.
* The space is not fully filled by MBEDTLS_MPI_MOD_REP_OPT_RED
* which requires at max (2N * ciL) bytes. */
mbedtls_mpi_core_mul(T, A, N->limbs, B, N->limbs);
/* Optimised Reduction */