Add mbedtls_mpi_mod_inv()
Signed-off-by: Tom Cosgrove <tom.cosgrove@arm.com>
This commit is contained in:
parent
786848b5c5
commit
4302d02fa8
2 changed files with 127 additions and 0 deletions
|
@ -191,6 +191,107 @@ int mbedtls_mpi_mod_sub( mbedtls_mpi_mod_residue *X,
|
|||
|
||||
return( 0 );
|
||||
}
|
||||
|
||||
int mbedtls_mpi_mod_inv( mbedtls_mpi_mod_residue *X,
|
||||
const mbedtls_mpi_mod_residue *A,
|
||||
const mbedtls_mpi_mod_modulus *N )
|
||||
{
|
||||
if( X->limbs != N->limbs || A->limbs != N->limbs )
|
||||
return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
|
||||
|
||||
/* Zero has the same value regardless of Montgomery form or not */
|
||||
if( mbedtls_mpi_core_check_zero_ct( A->p, A->limbs ) == 0 )
|
||||
return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
|
||||
|
||||
/* Will we need to do Montgomery conversion? */
|
||||
int mont_conv_needed;
|
||||
switch( N->int_rep )
|
||||
{
|
||||
case MBEDTLS_MPI_MOD_REP_MONTGOMERY:
|
||||
mont_conv_needed = 0;
|
||||
break;
|
||||
case MBEDTLS_MPI_MOD_REP_OPT_RED:
|
||||
mont_conv_needed = 1;
|
||||
break;
|
||||
default:
|
||||
return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
|
||||
}
|
||||
|
||||
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
|
||||
|
||||
/* If the input is already in Montgomery form, we have little to do but
|
||||
* allocate working memory and call mbedtls_mpi_mod_raw_inv_prime().
|
||||
*
|
||||
* If it's not, we need to
|
||||
* 1. Create a Montgomery version of the modulus;
|
||||
* 2. Convert the input into Mont. form, using X->p to hold it;
|
||||
* 3. (allocate and convert, same as if already in Mont. form);
|
||||
* 4. Convert the inverted output back from Mont. form.
|
||||
*
|
||||
* Since the Montgomery conversion functions are in-place, we'll need to
|
||||
* copy A into X before we start working on it (which could be avoided if
|
||||
* there was a not-in-place function to convert to Montgomery form.
|
||||
*/
|
||||
|
||||
/* Montgomery version of modulus (if not already in Mont. form).
|
||||
* We will only call setup if the input is not already in Montgomery form.
|
||||
* We will re-use N->p from input modulus, and make use of the fact that
|
||||
* mbedtls_mpi_mod_raw_to_mont_rep() won't free it. */
|
||||
mbedtls_mpi_mod_modulus Nmont;
|
||||
mbedtls_mpi_mod_modulus_init( &Nmont );
|
||||
|
||||
size_t working_limbs =
|
||||
mbedtls_mpi_mod_raw_inv_prime_working_limbs( N->limbs );
|
||||
|
||||
mbedtls_mpi_uint *working_memory = mbedtls_calloc( working_limbs,
|
||||
sizeof(mbedtls_mpi_uint) );
|
||||
if( working_memory == NULL )
|
||||
{
|
||||
ret = MBEDTLS_ERR_MPI_ALLOC_FAILED;
|
||||
goto cleanup;
|
||||
}
|
||||
|
||||
const mbedtls_mpi_uint *to_invert; /* Will alias A->p or X->p */
|
||||
const mbedtls_mpi_mod_modulus *Nuse; /* Which of N and Nmont to use */
|
||||
|
||||
if( mont_conv_needed )
|
||||
{
|
||||
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_modulus_setup( &Nmont, N->p, N->limbs,
|
||||
MBEDTLS_MPI_MOD_REP_MONTGOMERY ) );
|
||||
|
||||
mbedtls_mpi_core_to_mont_rep( X->p, A->p, Nmont.p, Nmont.limbs,
|
||||
Nmont.rep.mont.mm, Nmont.rep.mont.rr,
|
||||
working_memory );
|
||||
to_invert = X->p;
|
||||
Nuse = &Nmont;
|
||||
}
|
||||
else
|
||||
{
|
||||
to_invert = A->p;
|
||||
Nuse = N;
|
||||
}
|
||||
|
||||
mbedtls_mpi_mod_raw_inv_prime( X->p, to_invert,
|
||||
Nuse->p, Nuse->limbs,
|
||||
Nuse->rep.mont.rr,
|
||||
working_memory );
|
||||
|
||||
if( mont_conv_needed )
|
||||
mbedtls_mpi_core_from_mont_rep( X->p, X->p, Nmont.p, Nmont.limbs,
|
||||
Nmont.rep.mont.mm, working_memory );
|
||||
|
||||
cleanup:
|
||||
mbedtls_mpi_mod_modulus_free( &Nmont );
|
||||
|
||||
if (working_memory != NULL )
|
||||
{
|
||||
mbedtls_platform_zeroize( working_memory,
|
||||
working_limbs * sizeof(mbedtls_mpi_uint) );
|
||||
mbedtls_free( working_memory );
|
||||
}
|
||||
|
||||
return( ret );
|
||||
}
|
||||
/* END MERGE SLOT 3 */
|
||||
|
||||
/* BEGIN MERGE SLOT 4 */
|
||||
|
|
|
@ -192,6 +192,32 @@ int mbedtls_mpi_mod_sub( mbedtls_mpi_mod_residue *X,
|
|||
const mbedtls_mpi_mod_residue *A,
|
||||
const mbedtls_mpi_mod_residue *B,
|
||||
const mbedtls_mpi_mod_modulus *N );
|
||||
|
||||
/**
|
||||
* \brief Perform modular inversion of an MPI with respect to a modulus \p N.
|
||||
*
|
||||
* \p X may be aliased to \p A.
|
||||
*
|
||||
* \warning Currently only supports prime moduli, but does not check for them.
|
||||
*
|
||||
* \param[out] X The modular inverse of \p A with respect to \p N.
|
||||
* \param[in] A The number to calculate the modular inverse of.
|
||||
* Must not be 0.
|
||||
* \param[in] N The modulus to use.
|
||||
*
|
||||
* \return \c 0 if successful.
|
||||
* \return #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if \p A and \p N do not
|
||||
* have the same number of limbs.
|
||||
* \return #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if \p A is zero.
|
||||
* \return #MBEDTLS_ERR_MPI_ALLOC_FAILED if couldn't allocate enough
|
||||
* memory (needed for conversion to and from Mongtomery form
|
||||
* when not in Montgomery form already, and for temporary use
|
||||
* by the inversion calculation itself).
|
||||
*/
|
||||
|
||||
int mbedtls_mpi_mod_inv( mbedtls_mpi_mod_residue *X,
|
||||
const mbedtls_mpi_mod_residue *A,
|
||||
const mbedtls_mpi_mod_modulus *N );
|
||||
/* END MERGE SLOT 3 */
|
||||
|
||||
/* BEGIN MERGE SLOT 4 */
|
||||
|
|
Loading…
Reference in a new issue