270 lines
11 KiB
C
270 lines
11 KiB
C
/**
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* Core bignum functions
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*
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* This interface should only be used by the legacy bignum module (bignum.h)
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* and the modular bignum modules (bignum_mod.c, bignum_mod_raw.c). All other
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* modules should use the high-level modular bignum interface (bignum_mod.h)
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* or the legacy bignum interface (bignum.h).
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*
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* Copyright The Mbed TLS Contributors
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef MBEDTLS_BIGNUM_CORE_H
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#define MBEDTLS_BIGNUM_CORE_H
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#include "common.h"
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#if defined(MBEDTLS_BIGNUM_C)
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#include "mbedtls/bignum.h"
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#endif
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/** Count leading zero bits in a given integer.
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*
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* \param a Integer to count leading zero bits.
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*
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* \return The number of leading zero bits in \p a.
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*/
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size_t mbedtls_mpi_core_clz( mbedtls_mpi_uint a );
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/** Return the minimum number of bits required to represent the value held
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* in the MPI.
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*
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* \note This function returns 0 if all the limbs of \p A are 0.
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*
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* \param[in] A The address of the MPI.
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* \param A_limbs The number of limbs of \p A.
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*
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* \return The number of bits in \p A.
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*/
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size_t mbedtls_mpi_core_bitlen( const mbedtls_mpi_uint *A, size_t A_limbs );
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/** Convert a big-endian byte array aligned to the size of mbedtls_mpi_uint
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* into the storage form used by mbedtls_mpi.
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*
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* \param[in,out] A The address of the MPI.
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* \param A_limbs The number of limbs of \p A.
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*/
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void mbedtls_mpi_core_bigendian_to_host( mbedtls_mpi_uint *A,
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size_t A_limbs );
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/** Import X from unsigned binary data, little-endian.
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*
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* The MPI needs to have enough limbs to store the full value (including any
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* most significant zero bytes in the input).
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*
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* \param[out] X The address of the MPI.
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* \param X_limbs The number of limbs of \p X.
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* \param[in] input The input buffer to import from.
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* \param input_length The length bytes of \p input.
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*
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* \return \c 0 if successful.
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* \return #MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL if \p X isn't
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* large enough to hold the value in \p input.
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*/
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int mbedtls_mpi_core_read_le( mbedtls_mpi_uint *X,
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size_t X_limbs,
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const unsigned char *input,
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size_t input_length );
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/** Import X from unsigned binary data, big-endian.
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*
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* The MPI needs to have enough limbs to store the full value (including any
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* most significant zero bytes in the input).
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*
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* \param[out] X The address of the MPI.
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* May only be #NULL if \X_limbs is 0 and \p input_length
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* is 0.
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* \param X_limbs The number of limbs of \p X.
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* \param[in] input The input buffer to import from.
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* May only be #NULL if \p input_length is 0.
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* \param input_length The length in bytes of \p input.
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*
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* \return \c 0 if successful.
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* \return #MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL if \p X isn't
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* large enough to hold the value in \p input.
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*/
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int mbedtls_mpi_core_read_be( mbedtls_mpi_uint *X,
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size_t X_limbs,
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const unsigned char *input,
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size_t input_length );
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/** Export A into unsigned binary data, little-endian.
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*
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* \note If \p output is shorter than \p A the export is still successful if the
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* value held in \p A fits in the buffer (that is, if enough of the most
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* significant bytes of \p A are 0).
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*
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* \param[in] A The address of the MPI.
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* \param A_limbs The number of limbs of \p A.
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* \param[out] output The output buffer to export to.
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* \param output_length The length in bytes of \p output.
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*
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* \return \c 0 if successful.
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* \return #MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL if \p output isn't
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* large enough to hold the value of \p A.
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*/
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int mbedtls_mpi_core_write_le( const mbedtls_mpi_uint *A,
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size_t A_limbs,
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unsigned char *output,
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size_t output_length );
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/** Export A into unsigned binary data, big-endian.
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*
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* \note If \p output is shorter than \p A the export is still successful if the
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* value held in \p A fits in the buffer (that is, if enough of the most
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* significant bytes of \p A are 0).
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*
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* \param[in] A The address of the MPI.
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* \param A_limbs The number of limbs of \p A.
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* \param[out] output The output buffer to export to.
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* \param output_length The length in bytes of \p output.
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*
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* \return \c 0 if successful.
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* \return #MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL if \p output isn't
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* large enough to hold the value of \p A.
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*/
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int mbedtls_mpi_core_write_be( const mbedtls_mpi_uint *A,
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size_t A_limbs,
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unsigned char *output,
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size_t output_length );
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#define ciL ( sizeof(mbedtls_mpi_uint) ) /* chars in limb */
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#define biL ( ciL << 3 ) /* bits in limb */
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#define biH ( ciL << 2 ) /* half limb size */
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/*
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* Convert between bits/chars and number of limbs
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* Divide first in order to avoid potential overflows
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*/
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#define BITS_TO_LIMBS(i) ( (i) / biL + ( (i) % biL != 0 ) )
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#define CHARS_TO_LIMBS(i) ( (i) / ciL + ( (i) % ciL != 0 ) )
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/* Get a specific byte, without range checks. */
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#define GET_BYTE( X, i ) \
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( ( (X)[(i) / ciL] >> ( ( (i) % ciL ) * 8 ) ) & 0xff )
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/**
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* \brief Montgomery multiplication: X = A * B * R^-1 mod N (HAC 14.36)
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*
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* \param[out] X The destination MPI, as a little-endian array of
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* length \p AN_limbs.
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* On successful completion, X contains the result of
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* the multiplication A * B * R^-1 mod N where
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* R = (2^ciL)^AN_limbs.
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* \param[in] A Little-endian presentation of first operand.
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* Must have exactly \p AN_limbs limbs.
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* \param[in] B Little-endian presentation of second operand.
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* \param[in] B_limbs The number of limbs in \p B.
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* \param[in] N Little-endian presentation of the modulus.
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* This must be odd and have exactly \p AN_limbs limbs.
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* \param[in] AN_limbs The number of limbs in \p X, \p A, \p N.
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* \param mm The Montgomery constant for \p N: -N^-1 mod 2^ciL.
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* This can be calculated by `mbedtls_mpi_montg_init()`.
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* \param[in,out] T Temporary storage of size at least 2*AN_limbs+1 limbs.
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* Its initial content is unused and
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* its final content is indeterminate.
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*/
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void mbedtls_mpi_core_montmul( mbedtls_mpi_uint *X,
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const mbedtls_mpi_uint *A,
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const mbedtls_mpi_uint *B, size_t B_limbs,
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const mbedtls_mpi_uint *N, size_t AN_limbs,
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mbedtls_mpi_uint mm, mbedtls_mpi_uint *T );
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/**
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* \brief Calculate initialisation value for fast Montgomery modular
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* multiplication
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*
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* \param[in] N Little-endian presentation of the modulus. This must have
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* at least one limb.
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*
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* \return The initialisation value for fast Montgomery modular multiplication
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*/
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mbedtls_mpi_uint mbedtls_mpi_montg_init( const mbedtls_mpi_uint *N );
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/**
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* \brief Perform a known-size multiply accumulate operation: A += c * B
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*
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* \param[in,out] A The pointer to the (little-endian) array
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* representing the bignum to accumulate onto.
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* \param A_limbs The number of limbs of \p A. This must be
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* at least \p B_limbs.
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* \param[in] B The pointer to the (little-endian) array
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* representing the bignum to multiply with.
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* This may be the same as \p A. Otherwise,
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* it must be disjoint from \p A.
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* \param B_limbs The number of limbs of \p B.
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* \param c A scalar to multiply with.
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*
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* \return The carry at the end of the operation.
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*/
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mbedtls_mpi_uint mbedtls_mpi_core_mla( mbedtls_mpi_uint *A, size_t A_limbs,
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const mbedtls_mpi_uint *B, size_t B_limbs,
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mbedtls_mpi_uint c );
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/**
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* \brief Subtract two known-size large unsigned integers, returning the borrow.
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*
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* Calculate A - B where A and B have the same size.
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* This function operates modulo (2^ciL)^limbs and returns the carry
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* (1 if there was a wraparound, i.e. if `A < B`, and 0 otherwise).
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*
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* X may be aliased to A or B.
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*
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* \param[out] X The result of the subtraction.
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* \param[in] A Little-endian presentation of left operand.
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* \param[in] B Little-endian presentation of right operand.
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* \param limbs Number of limbs of \p X, \p A and \p B.
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*
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* \return 1 if `A < B`.
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* 0 if `A >= B`.
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*/
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mbedtls_mpi_uint mbedtls_mpi_core_sub( mbedtls_mpi_uint *X,
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const mbedtls_mpi_uint *A,
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const mbedtls_mpi_uint *B,
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size_t limbs );
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/**
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* \brief Constant-time conditional addition of two known-size large unsigned
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* integers, returning the carry.
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*
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* Functionally equivalent to
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*
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* ```
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* if( cond )
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* A += B;
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* return carry;
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* ```
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*
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* \param[in,out] A The pointer to the (little-endian) array
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* representing the bignum to accumulate onto.
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* \param[in] B The pointer to the (little-endian) array
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* representing the bignum to conditionally add
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* to \p A. This must be disjoint from \p A.
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* \param limbs Number of limbs of \p A and \p B.
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* \param cond Condition bit dictating whether addition should
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* happen or not. This must be \c 0 or \c 1.
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*
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* \warning If \p assign is neither 0 nor 1, the result of this function
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* is unspecified, and the resulting value in \p A might be
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* neither its original value nor \p A + \p B.
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*
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* \return 1 if `A + cond * B >= (2^{ciL})^limbs`, 0 otherwise.
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*/
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mbedtls_mpi_uint mbedtls_mpi_core_add_if( mbedtls_mpi_uint *A,
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const mbedtls_mpi_uint *B,
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size_t limbs,
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unsigned cond );
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#endif /* MBEDTLS_BIGNUM_CORE_H */
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