library/bignum_mod.h

/**
 *  Internal bignum functions
 *
 *  Copyright The Mbed TLS Contributors
 *  SPDX-License-Identifier: Apache-2.0
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
 *  not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

#ifndef MBEDTLS_BIGNUM_MOD_H
#define MBEDTLS_BIGNUM_MOD_H

#include "common.h"

#if defined(MBEDTLS_BIGNUM_C)
#include "mbedtls/bignum.h"
#endif


typedef struct
{
    size_t n;
    mbedtls_mpi_uint *p;
} mbedtls_mpi_mod_residue;

typedef void* mbedtls_mpi_mont_struct;
typedef void* mbedtls_mpi_opt_red_struct;

typedef struct {
    mbedtls_mpi_uint *p;
    size_t n;       // number of limbs
    size_t plen;    // bitlen of p
    int ext_rep;    // signals external representation (eg. byte order)
    int int_rep;    // selector to signal the active member of the union
    union rep
    {
        mbedtls_mpi_mont_struct mont;
        mbedtls_mpi_opt_red_struct ored;
    } rep;
} mbedtls_mpi_mod_modulus;

typedef enum
{
    MBEDTLS_MPI_MOD_REP_INVALID    = 0,
    MBEDTLS_MPI_MOD_REP_MONTGOMERY,
    MBEDTLS_MPI_MOD_REP_OPT_RED
} mbedtls_mpi_mod_rep_selector;

typedef enum
{
    MBEDTLS_MPI_MOD_EXT_REP_INVALID    = 0,
    MBEDTLS_MPI_MOD_EXT_REP_LE,
    MBEDTLS_MPI_MOD_EXT_REP_BE
} mbedtls_mpi_mod_ext_rep;


/** Setup a residue structure.
 *
 * \param r     The address of residue to setup. The size is determined by \p m.
 *              (In particular, it must have at least as many limbs as the
 *              modulus \p m.)
 * \param m     The address of the modulus related to \p r.
 * \param p     The address of the limb array storing the value of \p r. The
 *              memory pointed by \p p will be used by \p r and must not be
 *              freed or written until after mbedtls_mpi_mod_residue_release()
 *              is called.
 * \param pn    The number of limbs of \p p.
 *
 * \return      \c 0 if successful.
 * \return      #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if \p r, \p m or \p p is #NULL
 *              pointer, \p pn is less than the limbs in \p m or if \p p is not
 *              less than \p m.
 */
int mbedtls_mpi_mod_residue_setup( mbedtls_mpi_mod_residue *r,
                                   mbedtls_mpi_mod_modulus *m,
                                   mbedtls_mpi_uint *p,
                                   size_t pn );

/** Unbind elements of a residue structure.
 *
 * This function removes the reference to the limb array that was passed to
 * mbedtls_mpi_mod_residue_setup() to make it safe to free or use again.
 *
 * This function invalidates \p r and it must not be used until after
 * mbedtls_mpi_mod_residue_setup() is called on it again.
 *
 * \param r     The address of residue to release.
 */
void mbedtls_mpi_mod_residue_release( mbedtls_mpi_mod_residue *r );

/** Initialize a modulus structure.
 *
 * \param m     The address of a modulus.
 */
void mbedtls_mpi_mod_modulus_init( mbedtls_mpi_mod_modulus *m );

/** Setup a residue structure.
 *
 * \param m         The address of a modulus.
 * \param p         The address of the limb array storing the value of \p m. The
 *                  memory pointed by \p p will be used by \p r and must not be
 *                  freed or written until after
 *                  mbedtls_mpi_mod_modulus_free() is called.
 * \param pn        The number of limbs of \p p.
 * \param ext_rep   The external representation to be used for residues
 *                  associated with \p m (see #mbedtls_mpi_mod_ext_rep).
 * \param int_rep   The internal representation to be used for residues
 *                  associated with \p m (see #mbedtls_mpi_mod_rep_selector).
 *
 * \return      \c 0 if successful.
 * \return      #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if \p m or \p p is
 *              #NULL pointer or if \p ext_rep or \p int_rep is invalid.
 */
int mbedtls_mpi_mod_modulus_setup( mbedtls_mpi_mod_modulus *m,
                                   mbedtls_mpi_uint *p,
                                   size_t pn,
                                   int ext_rep,
                                   int int_rep );

/** Free elements of a modulus structure.
 *
 * This function frees any memory allocated by mbedtls_mpi_mod_modulus_setup().
 *
 * \warning This function does not free the limb array passed to
 *          mbedtls_mpi_mod_modulus_setup() only removes the reference to it,
 *          making it safe to free or to use it again.
 *
 * \param m     The address of a modulus.
 */
void mbedtls_mpi_mod_modulus_free( mbedtls_mpi_mod_modulus *m );

#endif /* MBEDTLS_BIGNUM_MOD_H */