288 lines
9.6 KiB
C
288 lines
9.6 KiB
C
/*
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* Low-level modular bignum functions
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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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#include "common.h"
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#if defined(MBEDTLS_BIGNUM_C)
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#include <string.h>
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#include "mbedtls/error.h"
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#include "mbedtls/platform_util.h"
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#include "mbedtls/platform.h"
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#include "bignum_core.h"
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#include "bignum_mod_raw.h"
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#include "bignum_mod.h"
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#include "constant_time_internal.h"
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#include "bignum_mod_raw_invasive.h"
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void mbedtls_mpi_mod_raw_cond_assign(mbedtls_mpi_uint *X,
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const mbedtls_mpi_uint *A,
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const mbedtls_mpi_mod_modulus *N,
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unsigned char assign)
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{
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mbedtls_mpi_core_cond_assign(X, A, N->limbs, mbedtls_ct_bool(assign));
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}
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void mbedtls_mpi_mod_raw_cond_swap(mbedtls_mpi_uint *X,
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mbedtls_mpi_uint *Y,
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const mbedtls_mpi_mod_modulus *N,
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unsigned char swap)
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{
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mbedtls_mpi_core_cond_swap(X, Y, N->limbs, mbedtls_ct_bool(swap));
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}
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int mbedtls_mpi_mod_raw_read(mbedtls_mpi_uint *X,
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const mbedtls_mpi_mod_modulus *N,
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const unsigned char *input,
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size_t input_length,
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mbedtls_mpi_mod_ext_rep ext_rep)
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{
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int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
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switch (ext_rep) {
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case MBEDTLS_MPI_MOD_EXT_REP_LE:
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ret = mbedtls_mpi_core_read_le(X, N->limbs,
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input, input_length);
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break;
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case MBEDTLS_MPI_MOD_EXT_REP_BE:
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ret = mbedtls_mpi_core_read_be(X, N->limbs,
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input, input_length);
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break;
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default:
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return MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
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}
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if (ret != 0) {
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goto cleanup;
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}
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if (!mbedtls_mpi_core_lt_ct(X, N->p, N->limbs)) {
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ret = MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
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goto cleanup;
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}
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cleanup:
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return ret;
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}
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int mbedtls_mpi_mod_raw_write(const mbedtls_mpi_uint *A,
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const mbedtls_mpi_mod_modulus *N,
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unsigned char *output,
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size_t output_length,
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mbedtls_mpi_mod_ext_rep ext_rep)
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{
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switch (ext_rep) {
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case MBEDTLS_MPI_MOD_EXT_REP_LE:
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return mbedtls_mpi_core_write_le(A, N->limbs,
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output, output_length);
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case MBEDTLS_MPI_MOD_EXT_REP_BE:
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return mbedtls_mpi_core_write_be(A, N->limbs,
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output, output_length);
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default:
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return MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
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}
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}
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void mbedtls_mpi_mod_raw_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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const mbedtls_mpi_mod_modulus *N)
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{
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mbedtls_mpi_uint c = mbedtls_mpi_core_sub(X, A, B, N->limbs);
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(void) mbedtls_mpi_core_add_if(X, N->p, N->limbs, (unsigned) c);
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}
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MBEDTLS_STATIC_TESTABLE
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void mbedtls_mpi_mod_raw_fix_quasi_reduction(mbedtls_mpi_uint *X,
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const mbedtls_mpi_mod_modulus *N)
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{
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mbedtls_mpi_uint c = mbedtls_mpi_core_sub(X, X, N->p, N->limbs);
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(void) mbedtls_mpi_core_add_if(X, N->p, N->limbs, (unsigned) c);
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}
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void mbedtls_mpi_mod_raw_mul(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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const mbedtls_mpi_mod_modulus *N,
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mbedtls_mpi_uint *T)
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{
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/* Standard (A * B) multiplication stored into pre-allocated T
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* buffer of fixed limb size of (2N + 1).
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*
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* The space may not not fully filled by when
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* MBEDTLS_MPI_MOD_REP_OPT_RED is used. */
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const size_t T_limbs = BITS_TO_LIMBS(N->bits) * 2;
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switch (N->int_rep) {
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case MBEDTLS_MPI_MOD_REP_MONTGOMERY:
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mbedtls_mpi_core_montmul(X, A, B, N->limbs, N->p, N->limbs,
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N->rep.mont.mm, T);
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break;
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case MBEDTLS_MPI_MOD_REP_OPT_RED:
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mbedtls_mpi_core_mul(T, A, N->limbs, B, N->limbs);
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/* Optimised Reduction */
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(*N->rep.ored.modp)(T, T_limbs);
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/* Convert back to canonical representation */
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mbedtls_mpi_mod_raw_fix_quasi_reduction(T, N);
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memcpy(X, T, N->limbs * sizeof(mbedtls_mpi_uint));
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break;
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default:
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break;
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}
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}
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size_t mbedtls_mpi_mod_raw_inv_prime_working_limbs(size_t AN_limbs)
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{
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/* mbedtls_mpi_mod_raw_inv_prime() needs a temporary for the exponent,
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* which will be the same size as the modulus and input (AN_limbs),
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* and additional space to pass to mbedtls_mpi_core_exp_mod(). */
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return AN_limbs +
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mbedtls_mpi_core_exp_mod_working_limbs(AN_limbs, AN_limbs);
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}
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void mbedtls_mpi_mod_raw_inv_prime(mbedtls_mpi_uint *X,
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const mbedtls_mpi_uint *A,
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const mbedtls_mpi_uint *N,
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size_t AN_limbs,
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const mbedtls_mpi_uint *RR,
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mbedtls_mpi_uint *T)
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{
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/* Inversion by power: g^|G| = 1 => g^(-1) = g^(|G|-1), and
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* |G| = N - 1, so we want
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* g^(|G|-1) = g^(N - 2)
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*/
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/* Use the first AN_limbs of T to hold N - 2 */
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mbedtls_mpi_uint *Nminus2 = T;
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(void) mbedtls_mpi_core_sub_int(Nminus2, N, 2, AN_limbs);
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/* Rest of T is given to exp_mod for its working space */
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mbedtls_mpi_core_exp_mod(X,
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A, N, AN_limbs, Nminus2, AN_limbs,
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RR, T + AN_limbs);
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}
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void mbedtls_mpi_mod_raw_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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const mbedtls_mpi_mod_modulus *N)
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{
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mbedtls_mpi_uint carry, borrow;
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carry = mbedtls_mpi_core_add(X, A, B, N->limbs);
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borrow = mbedtls_mpi_core_sub(X, X, N->p, N->limbs);
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(void) mbedtls_mpi_core_add_if(X, N->p, N->limbs, (unsigned) (carry ^ borrow));
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}
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int mbedtls_mpi_mod_raw_canonical_to_modulus_rep(
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mbedtls_mpi_uint *X,
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const mbedtls_mpi_mod_modulus *N)
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{
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switch (N->int_rep) {
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case MBEDTLS_MPI_MOD_REP_MONTGOMERY:
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return mbedtls_mpi_mod_raw_to_mont_rep(X, N);
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case MBEDTLS_MPI_MOD_REP_OPT_RED:
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return 0;
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default:
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return MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
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}
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}
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int mbedtls_mpi_mod_raw_modulus_to_canonical_rep(
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mbedtls_mpi_uint *X,
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const mbedtls_mpi_mod_modulus *N)
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{
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switch (N->int_rep) {
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case MBEDTLS_MPI_MOD_REP_MONTGOMERY:
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return mbedtls_mpi_mod_raw_from_mont_rep(X, N);
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case MBEDTLS_MPI_MOD_REP_OPT_RED:
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return 0;
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default:
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return MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
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}
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}
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int mbedtls_mpi_mod_raw_random(mbedtls_mpi_uint *X,
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mbedtls_mpi_uint min,
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const mbedtls_mpi_mod_modulus *N,
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int (*f_rng)(void *, unsigned char *, size_t),
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void *p_rng)
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{
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int ret = mbedtls_mpi_core_random(X, min, N->p, N->limbs, f_rng, p_rng);
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if (ret != 0) {
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return ret;
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}
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return mbedtls_mpi_mod_raw_canonical_to_modulus_rep(X, N);
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}
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int mbedtls_mpi_mod_raw_to_mont_rep(mbedtls_mpi_uint *X,
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const mbedtls_mpi_mod_modulus *N)
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{
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mbedtls_mpi_uint *T;
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const size_t t_limbs = mbedtls_mpi_core_montmul_working_limbs(N->limbs);
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if ((T = (mbedtls_mpi_uint *) mbedtls_calloc(t_limbs, ciL)) == NULL) {
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return MBEDTLS_ERR_MPI_ALLOC_FAILED;
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}
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mbedtls_mpi_core_to_mont_rep(X, X, N->p, N->limbs,
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N->rep.mont.mm, N->rep.mont.rr, T);
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mbedtls_zeroize_and_free(T, t_limbs * ciL);
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return 0;
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}
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int mbedtls_mpi_mod_raw_from_mont_rep(mbedtls_mpi_uint *X,
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const mbedtls_mpi_mod_modulus *N)
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{
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const size_t t_limbs = mbedtls_mpi_core_montmul_working_limbs(N->limbs);
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mbedtls_mpi_uint *T;
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if ((T = (mbedtls_mpi_uint *) mbedtls_calloc(t_limbs, ciL)) == NULL) {
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return MBEDTLS_ERR_MPI_ALLOC_FAILED;
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}
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mbedtls_mpi_core_from_mont_rep(X, X, N->p, N->limbs, N->rep.mont.mm, T);
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mbedtls_zeroize_and_free(T, t_limbs * ciL);
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return 0;
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}
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void mbedtls_mpi_mod_raw_neg(mbedtls_mpi_uint *X,
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const mbedtls_mpi_uint *A,
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const mbedtls_mpi_mod_modulus *N)
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{
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mbedtls_mpi_core_sub(X, N->p, A, N->limbs);
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/* If A=0 initially, then X=N now. Detect this by
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* subtracting N and catching the carry. */
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mbedtls_mpi_uint borrow = mbedtls_mpi_core_sub(X, X, N->p, N->limbs);
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(void) mbedtls_mpi_core_add_if(X, N->p, N->limbs, (unsigned) borrow);
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}
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#endif /* MBEDTLS_BIGNUM_C */
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