bignum_mod_raw: Ported mbedtls_mpi_get_montgomery_constant_unsafe from prototype
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
diff --git a/library/bignum_core.c b/library/bignum_core.c
index 0083729..457405d 100644
--- a/library/bignum_core.c
+++ b/library/bignum_core.c
@@ -511,4 +511,20 @@
mbedtls_ct_mpi_uint_cond_assign( AN_limbs, X, T, (unsigned char) ( carry ^ borrow ) );
}
+int mbedtls_mpi_get_montgomery_constant_unsafe( mbedtls_mpi *X,
+ mbedtls_mpi const *N )
+{
+ int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+
+ if ( X == NULL || N == NULL ) goto cleanup;
+
+ MBEDTLS_MPI_CHK( mbedtls_mpi_lset( X, 1 ) );
+ MBEDTLS_MPI_CHK( mbedtls_mpi_shift_l( X, N->n * 2 * biL ) );
+ MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( X, X, N ) );
+ MBEDTLS_MPI_CHK( mbedtls_mpi_shrink( X, N->n ) );
+
+cleanup:
+ return( ret );
+}
+
#endif /* MBEDTLS_BIGNUM_C */
diff --git a/library/bignum_core.h b/library/bignum_core.h
index 56a3bf8..3100bd5 100644
--- a/library/bignum_core.h
+++ b/library/bignum_core.h
@@ -412,4 +412,23 @@
const mbedtls_mpi_uint *N, size_t AN_limbs,
mbedtls_mpi_uint mm, mbedtls_mpi_uint *T );
+/**
+ * \brief Calculate initialisation value for fast Montgomery modular
+ * multiplication
+ *
+ * \param[out] X A pointer to the result of the calculation of
+ * Montgomery const 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.
+ * \return #MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED \p N, \p X are NULL
+ * or other operations fail.
+ */
+int mbedtls_mpi_get_montgomery_constant_unsafe( mbedtls_mpi *X,
+ mbedtls_mpi const *N );
+
#endif /* MBEDTLS_BIGNUM_CORE_H */