Add low-level Montgomery conversion functions to bignum_core
Signed-off-by: Tom Cosgrove <tom.cosgrove@arm.com>
diff --git a/library/bignum_core.h b/library/bignum_core.h
index 7b5787c..b898527 100644
--- a/library/bignum_core.h
+++ b/library/bignum_core.h
@@ -606,6 +606,81 @@
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 stricly 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*m->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 stricly 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*m->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 );
+
/* END MERGE SLOT 3 */
/* BEGIN MERGE SLOT 4 */