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mbedtls/library/bignum_mod.h
Werner Lewis eed01aabd3 Clarify wording in documentation 
Signed-off-by: Werner Lewis <werner.lewis@arm.com>
2022-12-14 09:44:00 +00:00

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/**
* Modular bignum functions
*
* This module implements operations on integers modulo some fixed modulus.
*/
/*
* 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
/* Skip 1 as it is slightly easier to accidentally pass to functions. */
typedef enum
{
MBEDTLS_MPI_MOD_REP_INVALID = 0,
MBEDTLS_MPI_MOD_REP_MONTGOMERY = 2,
MBEDTLS_MPI_MOD_REP_OPT_RED
} mbedtls_mpi_mod_rep_selector;
/* Make mbedtls_mpi_mod_rep_selector and mbedtls_mpi_mod_ext_rep disjoint to
* make it easier to catch when they are accidentally swapped. */
typedef enum
{
MBEDTLS_MPI_MOD_EXT_REP_INVALID = 0,
MBEDTLS_MPI_MOD_EXT_REP_LE = 8,
MBEDTLS_MPI_MOD_EXT_REP_BE
} mbedtls_mpi_mod_ext_rep;
typedef struct
{
mbedtls_mpi_uint *p;
size_t limbs;
} mbedtls_mpi_mod_residue;
typedef struct {
mbedtls_mpi_uint const *rr; /* The residue for 2^{2*n*biL} mod N */
mbedtls_mpi_uint mm; /* Montgomery const for -N^{-1} mod 2^{ciL} */
} mbedtls_mpi_mont_struct;
typedef void *mbedtls_mpi_opt_red_struct;
typedef struct {
const mbedtls_mpi_uint *p;
size_t limbs; // number of limbs
size_t bits; // bitlen of p
mbedtls_mpi_mod_rep_selector 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;
/** Setup a residue structure.
*
* The residue will be set up with the buffer \p p and modulus \p m.
*
* The memory pointed to by \p p will be used by the resulting residue structure.
* The value at the pointed-to memory will be the initial value of \p r and must
* hold a value that is less than the modulus. This value will be used as-is
* and interpreted according to the value of the `m->int_rep` field.
*
* The modulus \p m will be the modulus associated with \p r. The residue \p r
* should only be used in operations where the modulus is \p m.
*
* \param[out] r The address of the residue to setup.
* \param[in] m The address of the modulus related to \p r.
* \param[in] p The address of the limb array containing the value of \p r.
* The memory pointed to by \p p will be used by \p r and must
* not be modified in any way until after
* mbedtls_mpi_mod_residue_release() is called. The data
* pointed to by \p p must be less than the modulus (the value
* pointed to by `m->p`) and already in the representation
* indicated by `m->int_rep`.
* \param p_limbs The number of limbs of \p p. Must be the same as the number
* of limbs in the modulus \p m.
*
* \return \c 0 if successful.
* \return #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if \p p_limbs 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,
const mbedtls_mpi_mod_modulus *m,
mbedtls_mpi_uint *p,
size_t p_limbs );
/** 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[out] r The address of residue to release.
*/
void mbedtls_mpi_mod_residue_release( mbedtls_mpi_mod_residue *r );
/** Initialize a modulus structure.
*
* \param[out] m The address of the modulus structure to initialize.
*/
void mbedtls_mpi_mod_modulus_init( mbedtls_mpi_mod_modulus *m );
/** Setup a modulus structure.
*
* \param[out] m The address of the modulus structure to populate.
* \param[in] p The address of the limb array storing the value of \p m.
* The memory pointed to by \p p will be used by \p m and must
* not be modified in any way until after
* mbedtls_mpi_mod_modulus_free() is called.
* \param p_limbs The number of limbs of \p p.
* \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 int_rep is invalid.
*/
int mbedtls_mpi_mod_modulus_setup( mbedtls_mpi_mod_modulus *m,
const mbedtls_mpi_uint *p,
size_t p_limbs,
mbedtls_mpi_mod_rep_selector 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[in,out] m The address of the modulus structure to free.
*/
void mbedtls_mpi_mod_modulus_free( mbedtls_mpi_mod_modulus *m );
/* BEGIN MERGE SLOT 1 */
/* END MERGE SLOT 1 */
/* BEGIN MERGE SLOT 2 */
/* END MERGE SLOT 2 */
/* BEGIN MERGE SLOT 3 */
/**
* \brief Perform a fixed-size modular subtraction.
*
* Calculate `A - B modulo N`.
*
* \p A, \p B and \p X must all have the same number of limbs as \p N.
*
* \p X may be aliased to \p A or \p B, or even both, but may not overlap
* either otherwise.
*
* \note This function does not check that \p A or \p B are in canonical
* form (that is, are < \p N) - that will have been done by
* mbedtls_mpi_mod_residue_setup().
*
* \param[out] X The address of the result MPI. Must be initialized.
* Must have the same number of limbs as the modulus \p N.
* \param[in] A The address of the first MPI.
* \param[in] B The address of the second MPI.
* \param[in] N The address of the modulus. Used to perform a modulo
* operation on the result of the subtraction.
*
* \return \c 0 if successful.
* \return #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if the given MPIs do not
* have the correct number of limbs.
*/
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 );
/* END MERGE SLOT 3 */
/* BEGIN MERGE SLOT 4 */
/* END MERGE SLOT 4 */
/* BEGIN MERGE SLOT 5 */
/**
* \brief Perform a fixed-size modular addition.
*
* Calculate `A + B modulo N`.
*
* \p A, \p B and \p X must all be associated with the modulus \p N and must
* all have the same number of limbs as \p N.
*
* \p X may be aliased to \p A or \p B, or even both, but may not overlap
* either otherwise.
*
* \note This function does not check that \p A or \p B are in canonical
* form (that is, are < \p N) - that will have been done by
* mbedtls_mpi_mod_residue_setup().
*
* \param[out] X The address of the result residue. Must be initialized.
* Must have the same number of limbs as the modulus \p N.
* \param[in] A The address of the first input residue.
* \param[in] B The address of the second input residue.
* \param[in] N The address of the modulus. Used to perform a modulo
* operation on the result of the addition.
*
* \return \c 0 if successful.
* \return #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if the given MPIs do not
* have the correct number of limbs.
*/
int mbedtls_mpi_mod_add( mbedtls_mpi_mod_residue *X,
const mbedtls_mpi_mod_residue *A,
const mbedtls_mpi_mod_residue *B,
const mbedtls_mpi_mod_modulus *N );
/* END MERGE SLOT 5 */
/* BEGIN MERGE SLOT 6 */
/* END MERGE SLOT 6 */
/* BEGIN MERGE SLOT 7 */
/** Read a residue from a byte buffer.
*
* The residue will be automatically converted to the internal representation
* based on the value of the `m->int_rep` field.
*
* The modulus \p m will be the modulus associated with \p r. The residue \p r
* should only be used in operations where the modulus is \p m or a modulus
* equivalent to \p m (in the sense that all their fields or memory pointed by
* their fields hold the same value).
*
* \param[out] r The address of the residue. It must have exactly the same
* number of limbs as the modulus \p m.
* \param[in] m The address of the modulus.
* \param[in] buf The input buffer to import from.
* \param buflen The length in bytes of \p buf.
* \param ext_rep The endianness of the number in the input buffer.
*
* \return \c 0 if successful.
* \return #MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL if \p r isn't
* large enough to hold the value in \p buf.
* \return #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if \p ext_rep
* is invalid or the value in the buffer is not less than \p m.
*/
int mbedtls_mpi_mod_read( mbedtls_mpi_mod_residue *r,
const mbedtls_mpi_mod_modulus *m,
const unsigned char *buf,
size_t buflen,
mbedtls_mpi_mod_ext_rep ext_rep );
/** Write a residue into a byte buffer.
*
* The modulus \p m must be the modulus associated with \p r (see
* mbedtls_mpi_mod_residue_setup() and mbedtls_mpi_mod_read()).
*
* The residue will be automatically converted from the internal representation
* based on the value of `m->int_rep` field.
*
* \warning If the buffer is smaller than `m->bits`, the number of
* leading zeroes is leaked through timing. If \p r is
* secret, the caller must ensure that \p buflen is at least
* (`m->bits`+7)/8.
*
* \param[in] r The address of the residue. It must have the same number of
* limbs as the modulus \p m. (\p r is an input parameter, but
* its value will be modified during execution and restored
* before the function returns.)
* \param[in] m The address of the modulus associated with \r.
* \param[out] buf The output buffer to export to.
* \param buflen The length in bytes of \p buf.
* \param ext_rep The endianness in which the number should be written into
* the output buffer.
*
* \return \c 0 if successful.
* \return #MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL if \p buf isn't
* large enough to hold the value of \p r (without leading
* zeroes).
* \return #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if \p ext_rep is invalid.
* \return #MBEDTLS_ERR_MPI_ALLOC_FAILED if couldn't allocate enough
* memory for conversion. Can occur only for moduli with
* MBEDTLS_MPI_MOD_REP_MONTGOMERY.
*/
int mbedtls_mpi_mod_write( const mbedtls_mpi_mod_residue *r,
const mbedtls_mpi_mod_modulus *m,
unsigned char *buf,
size_t buflen,
mbedtls_mpi_mod_ext_rep ext_rep );
/* END MERGE SLOT 7 */
/* BEGIN MERGE SLOT 8 */
/* END MERGE SLOT 8 */
/* BEGIN MERGE SLOT 9 */
/* END MERGE SLOT 9 */
/* BEGIN MERGE SLOT 10 */
/* END MERGE SLOT 10 */
#endif /* MBEDTLS_BIGNUM_MOD_H */
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