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Bignum: Implement mbedtls_mpi_mod_raw_inv_prime() and tests

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Fixes #6023.

Signed-off-by: Tom Cosgrove <tom.cosgrove@arm.com>
This commit is contained in:
Tom Cosgrove
2022-12-08 09:44:10 +00:00
parent a7f0d7b029
commit 6129268fee
6 changed files with 187 additions and 4 deletions
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28
library/bignum_mod_raw.c
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@ -124,6 +124,34 @@ void mbedtls_mpi_mod_raw_sub( mbedtls_mpi_uint *X,
/* BEGIN MERGE SLOT 3 */
size_t mbedtls_mpi_mod_raw_inv_prime_working_limbs( size_t AN_limbs )
{
/* mbedtls_mpi_mod_raw_inv_prime() needs a temporary for the exponent,
* which will be the same size as the modulus and input (AN_limbs),
* and additional space to pass to mbedtls_mpi_core_exp_mod(). */
return( AN_limbs +
mbedtls_mpi_core_exp_mod_working_limbs( AN_limbs, AN_limbs ) );
}
void mbedtls_mpi_mod_raw_inv_prime( mbedtls_mpi_uint *X,
const mbedtls_mpi_uint *A,
const mbedtls_mpi_uint *N,
size_t AN_limbs,
const mbedtls_mpi_uint *RR,
mbedtls_mpi_uint *T )
{
/* Inversion by power: g^|G| = 1 => g^(-1) = g^(|G|-1), and
* |G| = N - 1, so we want
* g^(|G|-1) = g^(N - 2)
*/
mbedtls_mpi_uint *Nminus2 = T;
(void) mbedtls_mpi_core_sub_int( Nminus2, N, 2, AN_limbs );
mbedtls_mpi_core_exp_mod( X,
A, N, AN_limbs, Nminus2, AN_limbs,
RR, T + AN_limbs );
}
/* END MERGE SLOT 3 */
/* BEGIN MERGE SLOT 4 */