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766 lines
34 KiB
C
766 lines
34 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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* This module is about processing non-negative integers with a fixed upper
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* bound that's of the form 2^n-1 where n is a multiple of #biL.
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* These can be thought of integers written in base 2^#biL with a fixed
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* number of digits. Digits in this base are called *limbs*.
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* Many operations treat these numbers as the principal representation of
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* a number modulo 2^n or a smaller bound.
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*
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* The functions in this module obey the following conventions unless
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* explicitly indicated otherwise:
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*
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* - **Overflow**: some functions indicate overflow from the range
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* [0, 2^n-1] by returning carry parameters, while others operate
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* modulo and so cannot overflow. This should be clear from the function
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* documentation.
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* - **Bignum parameters**: Bignums are passed as pointers to an array of
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* limbs. A limb has the type #mbedtls_mpi_uint. Unless otherwise specified:
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* - Bignum parameters called \p A, \p B, ... are inputs, and are
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* not modified by the function.
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* - For operations modulo some number, the modulus is called \p N
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* and is input-only.
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* - Bignum parameters called \p X, \p Y are outputs or input-output.
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* The initial content of output-only parameters is ignored.
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* - Some functions use different names that reflect traditional
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* naming of operands of certain operations (e.g.
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* divisor/dividend/quotient/remainder).
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* - \p T is a temporary storage area. The initial content of such
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* parameter is ignored and the final content is unspecified.
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* - **Bignum sizes**: bignum sizes are always expressed in limbs.
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* Most functions work on bignums of a given size and take a single
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* \p limbs parameter that applies to all parameters that are limb arrays.
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* All bignum sizes must be at least 1 and must be significantly less than
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* #SIZE_MAX. The behavior if a size is 0 is undefined. The behavior if the
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* total size of all parameters overflows #SIZE_MAX is undefined.
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* - **Parameter ordering**: for bignum parameters, outputs come before inputs.
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* Temporaries come last.
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* - **Aliasing**: in general, output bignums may be aliased to one or more
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* inputs. As an exception, parameters that are documented as a modulus value
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* may not be aliased to an output. Outputs may not be aliased to one another.
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* Temporaries may not be aliased to any other parameter.
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* - **Overlap**: apart from aliasing of limb array pointers (where two
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* arguments are equal pointers), overlap is not supported and may result
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* in undefined behavior.
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* - **Error handling**: This is a low-level module. Functions generally do not
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* try to protect against invalid arguments such as nonsensical sizes or
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* null pointers. Note that some functions that operate on bignums of
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* different sizes have constraints about their size, and violating those
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* constraints may lead to buffer overflows.
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* - **Modular representatives**: functions that operate modulo \p N expect
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* all modular inputs to be in the range [0, \p N - 1] and guarantee outputs
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* in the range [0, \p N - 1]. If an input is out of range, outputs are
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* fully unspecified, though bignum values out of range should not cause
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* buffer overflows (beware that this is not extensively tested).
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*/
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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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#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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/** Count leading zero bits in a given integer.
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*
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* \warning The result is undefined if \p a == 0
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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, if \p a != 0.
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* If \p a == 0, the result is undefined.
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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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/** \brief Compare a machine integer with an MPI.
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*
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* This function operates in constant time with respect
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* to the values of \p min and \p A.
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*
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* \param min A machine integer.
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* \param[in] A An MPI.
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* \param A_limbs The number of limbs of \p A.
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* This must be at least 1.
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*
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* \return 1 if \p min is less than or equal to \p A, otherwise 0.
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*/
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unsigned mbedtls_mpi_core_uint_le_mpi(mbedtls_mpi_uint min,
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const mbedtls_mpi_uint *A,
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size_t A_limbs);
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/**
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* \brief Perform a safe conditional copy of an MPI which doesn't reveal
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* whether assignment was done or not.
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*
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* \param[out] X The address of the destination MPI.
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* This must be initialized. Must have enough limbs to
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* store the full value of \p A.
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* \param[in] A The address of the source MPI. This must be initialized.
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* \param limbs The number of limbs of \p A.
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* \param assign The condition deciding whether to perform the
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* assignment or not. Must be either 0 or 1:
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* * \c 1: Perform the assignment `X = A`.
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* * \c 0: Keep the original value of \p X.
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*
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* \note This function avoids leaking any information about whether
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* the assignment was done or not.
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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 indeterminate, and the resulting value in \p X might be
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* neither its original value nor the value in \p A.
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*/
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void mbedtls_mpi_core_cond_assign(mbedtls_mpi_uint *X,
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const mbedtls_mpi_uint *A,
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size_t limbs,
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unsigned char assign);
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/**
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* \brief Perform a safe conditional swap of two MPIs which doesn't reveal
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* whether the swap was done or not.
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*
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* \param[in,out] X The address of the first MPI.
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* This must be initialized.
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* \param[in,out] Y The address of the second MPI.
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* This must be initialized.
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* \param limbs The number of limbs of \p X and \p Y.
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* \param swap The condition deciding whether to perform
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* the swap or not. Must be either 0 or 1:
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* * \c 1: Swap the values of \p X and \p Y.
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* * \c 0: Keep the original values of \p X and \p Y.
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*
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* \note This function avoids leaking any information about whether
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* the swap was done or not.
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*
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* \warning If \p swap is neither 0 nor 1, the result of this function
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* is indeterminate, and both \p X and \p Y might end up with
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* values different to either of the original ones.
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*/
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void mbedtls_mpi_core_cond_swap(mbedtls_mpi_uint *X,
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mbedtls_mpi_uint *Y,
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size_t limbs,
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unsigned char swap);
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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 \p 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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/** \brief Shift an MPI in-place right by a number of bits.
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*
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* Shifting by more bits than there are bit positions
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* in \p X is valid and results in setting \p X to 0.
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*
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* This function's execution time depends on the value
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* of \p count (and of course \p limbs).
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*
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* \param[in,out] X The number to shift.
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* \param limbs The number of limbs of \p X. This must be at least 1.
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* \param count The number of bits to shift by.
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*/
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void mbedtls_mpi_core_shift_r(mbedtls_mpi_uint *X, size_t limbs,
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size_t count);
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/**
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* \brief Shift an MPI in-place left by a number of bits.
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*
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* Shifting by more bits than there are bit positions
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* in \p X will produce an unspecified result.
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*
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* This function's execution time depends on the value
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* of \p count (and of course \p limbs).
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* \param[in,out] X The number to shift.
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* \param limbs The number of limbs of \p X. This must be at least 1.
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* \param count The number of bits to shift by.
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*/
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void mbedtls_mpi_core_shift_l(mbedtls_mpi_uint *X, size_t limbs,
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size_t count);
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/**
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* \brief Add two fixed-size large unsigned integers, returning the carry.
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*
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* Calculates `A + B` where `A` and `B` have the same size.
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*
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* This function operates modulo `2^(biL*limbs)` and returns the carry
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* (1 if there was a wraparound, and 0 otherwise).
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*
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* \p X may be aliased to \p A or \p B.
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*
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* \param[out] X The result of the addition.
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* \param[in] A Little-endian presentation of the left operand.
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* \param[in] B Little-endian presentation of the 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 >= 2^(biL*limbs)`, 0 otherwise.
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*/
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mbedtls_mpi_uint mbedtls_mpi_core_add(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 Conditional addition of two fixed-size large unsigned integers,
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* 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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* X += A;
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* return carry;
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* ```
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*
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* This function operates modulo `2^(biL*limbs)`.
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*
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* \param[in,out] X The pointer to the (little-endian) array
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* representing the bignum to accumulate onto.
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* \param[in] A The pointer to the (little-endian) array
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* representing the bignum to conditionally add
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* to \p X. This may be aliased to \p X but may not
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* overlap otherwise.
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* \param limbs Number of limbs of \p X and \p A.
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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 cond is neither 0 nor 1, the result of this function
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* is unspecified, and the resulting value in \p X might be
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* neither its original value nor \p X + \p A.
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*
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* \return 1 if `X + cond * A >= 2^(biL*limbs)`, 0 otherwise.
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*/
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mbedtls_mpi_uint mbedtls_mpi_core_add_if(mbedtls_mpi_uint *X,
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const mbedtls_mpi_uint *A,
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size_t limbs,
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unsigned cond);
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/**
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* \brief Subtract two fixed-size large unsigned integers, returning the borrow.
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*
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* Calculate `A - B` where \p A and \p B have the same size.
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* This function operates modulo `2^(biL*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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* \p X may be aliased to \p A or \p B, or even both, but may not overlap
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* either otherwise.
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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 Perform a fixed-size multiply accumulate operation: X += b * A
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*
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* \p X may be aliased to \p A (when \p X_limbs == \p A_limbs), but may not
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* otherwise overlap.
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*
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* This function operates modulo `2^(biL*X_limbs)`.
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*
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* \param[in,out] X The pointer to the (little-endian) array
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* representing the bignum to accumulate onto.
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* \param X_limbs The number of limbs of \p X. This must be
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* at least \p A_limbs.
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* \param[in] A The pointer to the (little-endian) array
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* representing the bignum to multiply with.
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* This may be aliased to \p X but may not overlap
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* otherwise.
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* \param A_limbs The number of limbs of \p A.
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* \param b X 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 *X, size_t X_limbs,
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const mbedtls_mpi_uint *A, size_t A_limbs,
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mbedtls_mpi_uint b);
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/**
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* \brief Perform a known-size multiplication
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*
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* \p X may not be aliased to any of the inputs for this function.
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* \p A may be aliased to \p B.
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*
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* \param[out] X The pointer to the (little-endian) array to receive
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* the product of \p A_limbs and \p B_limbs.
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* This must be of length \p A_limbs + \p B_limbs.
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* \param[in] A The pointer to the (little-endian) array
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* representing the first factor.
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* \param A_limbs The number of limbs in \p A.
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* \param[in] B The pointer to the (little-endian) array
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* representing the second factor.
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* \param B_limbs The number of limbs in \p B.
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*/
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void mbedtls_mpi_core_mul(mbedtls_mpi_uint *X,
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const 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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/**
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* \brief Calculate initialisation value for fast Montgomery modular
|
|
* multiplication
|
|
*
|
|
* \param[in] N Little-endian presentation of the modulus. This must have
|
|
* at least one limb.
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|
*
|
|
* \return The initialisation value for fast Montgomery modular multiplication
|
|
*/
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|
mbedtls_mpi_uint mbedtls_mpi_core_montmul_init(const mbedtls_mpi_uint *N);
|
|
|
|
/**
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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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* \p A and \p B must be in canonical form. That is, < \p N.
|
|
*
|
|
* \p X may be aliased to \p A or \p N, or even \p B (if \p AN_limbs ==
|
|
* \p B_limbs) but may not overlap any parameters otherwise.
|
|
*
|
|
* \p A and \p B may alias each other, if \p AN_limbs == \p B_limbs. They may
|
|
* not alias \p N (since they must be in canonical form, they cannot == \p N).
|
|
*
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|
* \param[out] X The destination MPI, as a little-endian array of
|
|
* length \p AN_limbs.
|
|
* On successful completion, X contains the result of
|
|
* the multiplication `A * B * R^-1` mod N where
|
|
* `R = 2^(biL*AN_limbs)`.
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|
* \param[in] A Little-endian presentation of first operand.
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|
* Must have the same number of limbs as \p N.
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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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* Must be <= \p AN_limbs.
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* \param[in] N Little-endian presentation of the modulus.
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* This must be odd, and have exactly the same number
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* of limbs as \p A.
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|
* It may alias \p X, but must not alias or otherwise
|
|
* overlap any of the other parameters.
|
|
* \param[in] AN_limbs The number of limbs in \p X, \p A and \p N.
|
|
* \param mm The Montgomery constant for \p N: -N^-1 mod 2^biL.
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|
* This can be calculated by `mbedtls_mpi_core_montmul_init()`.
|
|
* \param[in,out] T Temporary storage of size at least 2*AN_limbs+1 limbs.
|
|
* Its initial content is unused and
|
|
* its final content is indeterminate.
|
|
* It must not alias or otherwise overlap any of the
|
|
* other parameters.
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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);
|
|
|
|
/**
|
|
* \brief Calculate the square of the Montgomery constant. (Needed
|
|
* for conversion and operations in Montgomery form.)
|
|
*
|
|
* \param[out] X A pointer to the result of the calculation of
|
|
* the square of the Montgomery constant:
|
|
* 2^{2*n*biL} mod N.
|
|
* \param[in] N Little-endian presentation of the modulus, which must be odd.
|
|
*
|
|
* \return 0 if successful.
|
|
* \return #MBEDTLS_ERR_MPI_ALLOC_FAILED if there is not enough space
|
|
* to store the value of Montgomery constant squared.
|
|
* \return #MBEDTLS_ERR_MPI_DIVISION_BY_ZERO if \p N modulus is zero.
|
|
* \return #MBEDTLS_ERR_MPI_NEGATIVE_VALUE if \p N modulus is negative.
|
|
*/
|
|
int mbedtls_mpi_core_get_mont_r2_unsafe(mbedtls_mpi *X,
|
|
const mbedtls_mpi *N);
|
|
|
|
#if defined(MBEDTLS_TEST_HOOKS)
|
|
/**
|
|
* Copy an MPI from a table without leaking the index.
|
|
*
|
|
* \param dest The destination buffer. This must point to a writable
|
|
* buffer of at least \p limbs limbs.
|
|
* \param table The address of the table. This must point to a readable
|
|
* array of \p count elements of \p limbs limbs each.
|
|
* \param limbs The number of limbs in each table entry.
|
|
* \param count The number of entries in \p table.
|
|
* \param index The (secret) table index to look up. This must be in the
|
|
* range `0 .. count-1`.
|
|
*/
|
|
void mbedtls_mpi_core_ct_uint_table_lookup(mbedtls_mpi_uint *dest,
|
|
const mbedtls_mpi_uint *table,
|
|
size_t limbs,
|
|
size_t count,
|
|
size_t index);
|
|
#endif /* MBEDTLS_TEST_HOOKS */
|
|
|
|
/**
|
|
* \brief Fill an integer with a number of random bytes.
|
|
*
|
|
* \param X The destination MPI.
|
|
* \param X_limbs The number of limbs of \p X.
|
|
* \param bytes The number of random bytes to generate.
|
|
* \param f_rng The RNG function to use. This must not be \c NULL.
|
|
* \param p_rng The RNG parameter to be passed to \p f_rng. This may be
|
|
* \c NULL if \p f_rng doesn't need a context argument.
|
|
*
|
|
* \return \c 0 if successful.
|
|
* \return #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if \p X does not have
|
|
* enough room for \p bytes bytes.
|
|
* \return A negative error code on RNG failure.
|
|
*
|
|
* \note The bytes obtained from the RNG are interpreted
|
|
* as a big-endian representation of an MPI; this can
|
|
* be relevant in applications like deterministic ECDSA.
|
|
*/
|
|
int mbedtls_mpi_core_fill_random(mbedtls_mpi_uint *X, size_t X_limbs,
|
|
size_t bytes,
|
|
int (*f_rng)(void *, unsigned char *, size_t),
|
|
void *p_rng);
|
|
|
|
/** Generate a random number uniformly in a range.
|
|
*
|
|
* This function generates a random number between \p min inclusive and
|
|
* \p N exclusive.
|
|
*
|
|
* The procedure complies with RFC 6979 §3.3 (deterministic ECDSA)
|
|
* when the RNG is a suitably parametrized instance of HMAC_DRBG
|
|
* and \p min is \c 1.
|
|
*
|
|
* \note There are `N - min` possible outputs. The lower bound
|
|
* \p min can be reached, but the upper bound \p N cannot.
|
|
*
|
|
* \param X The destination MPI, with \p limbs limbs.
|
|
* It must not be aliased with \p N or otherwise overlap it.
|
|
* \param min The minimum value to return.
|
|
* \param N The upper bound of the range, exclusive, with \p limbs limbs.
|
|
* In other words, this is one plus the maximum value to return.
|
|
* \p N must be strictly larger than \p min.
|
|
* \param limbs The number of limbs of \p N and \p X.
|
|
* This must not be 0.
|
|
* \param f_rng The RNG function to use. This must not be \c NULL.
|
|
* \param p_rng The RNG parameter to be passed to \p f_rng.
|
|
*
|
|
* \return \c 0 if successful.
|
|
* \return #MBEDTLS_ERR_MPI_NOT_ACCEPTABLE if the implementation was
|
|
* unable to find a suitable value within a limited number
|
|
* of attempts. This has a negligible probability if \p N
|
|
* is significantly larger than \p min, which is the case
|
|
* for all usual cryptographic applications.
|
|
*/
|
|
int mbedtls_mpi_core_random(mbedtls_mpi_uint *X,
|
|
mbedtls_mpi_uint min,
|
|
const mbedtls_mpi_uint *N,
|
|
size_t limbs,
|
|
int (*f_rng)(void *, unsigned char *, size_t),
|
|
void *p_rng);
|
|
|
|
/**
|
|
* \brief Returns the number of limbs of working memory required for
|
|
* a call to `mbedtls_mpi_core_exp_mod()`.
|
|
*
|
|
* \note This will always be at least
|
|
* `mbedtls_mpi_core_montmul_working_limbs(AN_limbs)`,
|
|
* i.e. sufficient for a call to `mbedtls_mpi_core_montmul()`.
|
|
*
|
|
* \param AN_limbs The number of limbs in the input `A` and the modulus `N`
|
|
* (they must be the same size) that will be given to
|
|
* `mbedtls_mpi_core_exp_mod()`.
|
|
* \param E_limbs The number of limbs in the exponent `E` that will be given
|
|
* to `mbedtls_mpi_core_exp_mod()`.
|
|
*
|
|
* \return The number of limbs of working memory required by
|
|
* `mbedtls_mpi_core_exp_mod()`.
|
|
*/
|
|
size_t mbedtls_mpi_core_exp_mod_working_limbs(size_t AN_limbs, size_t E_limbs);
|
|
|
|
/**
|
|
* \brief Perform a modular exponentiation with secret exponent:
|
|
* X = A^E mod N, where \p A is already in Montgomery form.
|
|
*
|
|
* \p X may be aliased to \p A, but not to \p RR or \p E, even if \p E_limbs ==
|
|
* \p AN_limbs.
|
|
*
|
|
* \param[out] X The destination MPI, as a little endian array of length
|
|
* \p AN_limbs.
|
|
* \param[in] A The base MPI, as a little endian array of length \p AN_limbs.
|
|
* Must be in Montgomery form.
|
|
* \param[in] N The modulus, as a little endian array of length \p AN_limbs.
|
|
* \param AN_limbs The number of limbs in \p X, \p A, \p N, \p RR.
|
|
* \param[in] E The exponent, as a little endian array of length \p E_limbs.
|
|
* \param E_limbs The number of limbs in \p E.
|
|
* \param[in] RR The precomputed residue of 2^{2*biL} modulo N, as a little
|
|
* endian array of length \p AN_limbs.
|
|
* \param[in,out] T Temporary storage of at least the number of limbs returned
|
|
* by `mbedtls_mpi_core_exp_mod_working_limbs()`.
|
|
* Its initial content is unused and its final content is
|
|
* indeterminate.
|
|
* It must not alias or otherwise overlap any of the other
|
|
* parameters.
|
|
* It is up to the caller to zeroize \p T when it is no
|
|
* longer needed, and before freeing it if it was dynamically
|
|
* allocated.
|
|
*/
|
|
void mbedtls_mpi_core_exp_mod(mbedtls_mpi_uint *X,
|
|
const mbedtls_mpi_uint *A,
|
|
const mbedtls_mpi_uint *N, size_t AN_limbs,
|
|
const mbedtls_mpi_uint *E, size_t E_limbs,
|
|
const mbedtls_mpi_uint *RR,
|
|
mbedtls_mpi_uint *T);
|
|
|
|
/**
|
|
* \brief Subtract unsigned integer from known-size large unsigned integers.
|
|
* Return the borrow.
|
|
*
|
|
* \param[out] X The result of the subtraction.
|
|
* \param[in] A The left operand.
|
|
* \param b The unsigned scalar to subtract.
|
|
* \param limbs Number of limbs of \p X and \p A.
|
|
*
|
|
* \return 1 if `A < b`.
|
|
* 0 if `A >= b`.
|
|
*/
|
|
mbedtls_mpi_uint mbedtls_mpi_core_sub_int(mbedtls_mpi_uint *X,
|
|
const mbedtls_mpi_uint *A,
|
|
mbedtls_mpi_uint b,
|
|
size_t limbs);
|
|
|
|
/**
|
|
* \brief Determine if a given MPI has the value \c 0 in constant time with
|
|
* respect to the value (but not with respect to the number of limbs).
|
|
*
|
|
* \param[in] A The MPI to test.
|
|
* \param limbs Number of limbs in \p A.
|
|
*
|
|
* \return 0 if `A == 0`
|
|
* non-0 (may be any value) if `A != 0`.
|
|
*/
|
|
mbedtls_mpi_uint mbedtls_mpi_core_check_zero_ct(const mbedtls_mpi_uint *A,
|
|
size_t limbs);
|
|
|
|
/**
|
|
* \brief Returns the number of limbs of working memory required for
|
|
* a call to `mbedtls_mpi_core_montmul()`.
|
|
*
|
|
* \param AN_limbs The number of limbs in the input `A` and the modulus `N`
|
|
* (they must be the same size) that will be given to
|
|
* `mbedtls_mpi_core_montmul()` or one of the other functions
|
|
* that specifies this as the amount of working memory needed.
|
|
*
|
|
* \return The number of limbs of working memory required by
|
|
* `mbedtls_mpi_core_montmul()` (or other similar function).
|
|
*/
|
|
static inline size_t mbedtls_mpi_core_montmul_working_limbs(size_t AN_limbs)
|
|
{
|
|
return 2 * AN_limbs + 1;
|
|
}
|
|
|
|
/** Convert an MPI into Montgomery form.
|
|
*
|
|
* \p X may be aliased to \p A, but may not otherwise overlap it.
|
|
*
|
|
* \p X may not alias \p N (it is in canonical form, so must be strictly less
|
|
* than \p N). Nor may it alias or overlap \p rr (this is unlikely to be
|
|
* required in practice.)
|
|
*
|
|
* This function is a thin wrapper around `mbedtls_mpi_core_montmul()` that is
|
|
* an alternative to calling `mbedtls_mpi_mod_raw_to_mont_rep()` when we
|
|
* don't want to allocate memory.
|
|
*
|
|
* \param[out] X The result of the conversion.
|
|
* Must have the same number of limbs as \p A.
|
|
* \param[in] A The MPI to convert into Montgomery form.
|
|
* Must have the same number of limbs as the modulus.
|
|
* \param[in] N The address of the modulus, which gives the size of
|
|
* the base `R` = 2^(biL*N->limbs).
|
|
* \param[in] AN_limbs The number of limbs in \p X, \p A, \p N and \p rr.
|
|
* \param mm The Montgomery constant for \p N: -N^-1 mod 2^biL.
|
|
* This can be determined by calling
|
|
* `mbedtls_mpi_core_montmul_init()`.
|
|
* \param[in] rr The residue for `2^{2*n*biL} mod N`.
|
|
* \param[in,out] T Temporary storage of size at least
|
|
* `mbedtls_mpi_core_montmul_working_limbs(AN_limbs)`
|
|
* limbs.
|
|
* Its initial content is unused and
|
|
* its final content is indeterminate.
|
|
* It must not alias or otherwise overlap any of the
|
|
* other parameters.
|
|
*/
|
|
void mbedtls_mpi_core_to_mont_rep(mbedtls_mpi_uint *X,
|
|
const mbedtls_mpi_uint *A,
|
|
const mbedtls_mpi_uint *N,
|
|
size_t AN_limbs,
|
|
mbedtls_mpi_uint mm,
|
|
const mbedtls_mpi_uint *rr,
|
|
mbedtls_mpi_uint *T);
|
|
|
|
/** Convert an MPI from Montgomery form.
|
|
*
|
|
* \p X may be aliased to \p A, but may not otherwise overlap it.
|
|
*
|
|
* \p X may not alias \p N (it is in canonical form, so must be strictly less
|
|
* than \p N).
|
|
*
|
|
* This function is a thin wrapper around `mbedtls_mpi_core_montmul()` that is
|
|
* an alternative to calling `mbedtls_mpi_mod_raw_from_mont_rep()` when we
|
|
* don't want to allocate memory.
|
|
*
|
|
* \param[out] X The result of the conversion.
|
|
* Must have the same number of limbs as \p A.
|
|
* \param[in] A The MPI to convert from Montgomery form.
|
|
* Must have the same number of limbs as the modulus.
|
|
* \param[in] N The address of the modulus, which gives the size of
|
|
* the base `R` = 2^(biL*N->limbs).
|
|
* \param[in] AN_limbs The number of limbs in \p X, \p A and \p N.
|
|
* \param mm The Montgomery constant for \p N: -N^-1 mod 2^biL.
|
|
* This can be determined by calling
|
|
* `mbedtls_mpi_core_montmul_init()`.
|
|
* \param[in,out] T Temporary storage of size at least
|
|
* `mbedtls_mpi_core_montmul_working_limbs(AN_limbs)`
|
|
* limbs.
|
|
* Its initial content is unused and
|
|
* its final content is indeterminate.
|
|
* It must not alias or otherwise overlap any of the
|
|
* other parameters.
|
|
*/
|
|
void mbedtls_mpi_core_from_mont_rep(mbedtls_mpi_uint *X,
|
|
const mbedtls_mpi_uint *A,
|
|
const mbedtls_mpi_uint *N,
|
|
size_t AN_limbs,
|
|
mbedtls_mpi_uint mm,
|
|
mbedtls_mpi_uint *T);
|
|
|
|
#endif /* MBEDTLS_BIGNUM_CORE_H */
|