1 /** 2 * Low level bignum functions 3 * 4 * Copyright The Mbed TLS Contributors 5 * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later 6 */ 7 8 #ifndef MBEDTLS_BIGNUM_INTERNAL_H 9 #define MBEDTLS_BIGNUM_INTERNAL_H 10 11 #include "mbedtls/bignum.h" 12 13 /** 14 * \brief Calculate the square of the Montgomery constant. (Needed 15 * for conversion and operations in Montgomery form.) 16 * 17 * \param[out] X A pointer to the result of the calculation of 18 * the square of the Montgomery constant: 19 * 2^{2*n*biL} mod N. 20 * \param[in] N Little-endian presentation of the modulus, which must be odd. 21 * 22 * \return 0 if successful. 23 * \return #MBEDTLS_ERR_MPI_ALLOC_FAILED if there is not enough space 24 * to store the value of Montgomery constant squared. 25 * \return #MBEDTLS_ERR_MPI_DIVISION_BY_ZERO if \p N modulus is zero. 26 * \return #MBEDTLS_ERR_MPI_NEGATIVE_VALUE if \p N modulus is negative. 27 */ 28 int mbedtls_mpi_get_mont_r2_unsafe(mbedtls_mpi *X, 29 const mbedtls_mpi *N); 30 31 /** 32 * \brief Calculate initialisation value for fast Montgomery modular 33 * multiplication 34 * 35 * \param[in] N Little-endian presentation of the modulus. This must have 36 * at least one limb. 37 * 38 * \return The initialisation value for fast Montgomery modular multiplication 39 */ 40 mbedtls_mpi_uint mbedtls_mpi_montmul_init(const mbedtls_mpi_uint *N); 41 42 /** Montgomery multiplication: A = A * B * R^-1 mod N (HAC 14.36) 43 * 44 * \param[in,out] A One of the numbers to multiply. 45 * It must have at least as many limbs as N 46 * (A->n >= N->n), and any limbs beyond n are ignored. 47 * On successful completion, A contains the result of 48 * the multiplication A * B * R^-1 mod N where 49 * R = (2^ciL)^n. 50 * \param[in] B One of the numbers to multiply. 51 * It must be nonzero and must not have more limbs than N 52 * (B->n <= N->n). 53 * \param[in] N The modulo. N must be odd. 54 * \param mm The value calculated by 55 * `mbedtls_mpi_montg_init(&mm, N)`. 56 * This is -N^-1 mod 2^ciL. 57 * \param[in,out] T A bignum for temporary storage. 58 * It must be at least twice the limb size of N plus 2 59 * (T->n >= 2 * (N->n + 1)). 60 * Its initial content is unused and 61 * its final content is indeterminate. 62 * Note that unlike the usual convention in the library 63 * for `const mbedtls_mpi*`, the content of T can change. 64 */ 65 void mbedtls_mpi_montmul(mbedtls_mpi *A, 66 const mbedtls_mpi *B, 67 const mbedtls_mpi *N, 68 mbedtls_mpi_uint mm, 69 const mbedtls_mpi *T); 70 71 #endif /* MBEDTLS_BIGNUM_INTERNAL_H */ 72