diff --git a/library/bignum_core.c b/library/bignum_core.c
index e50f043c5..1ec5340b7 100644
--- a/library/bignum_core.c
+++ b/library/bignum_core.c
@@ -448,6 +448,15 @@ mbedtls_mpi_uint mbedtls_mpi_core_mla(mbedtls_mpi_uint *d, size_t d_len,
     return c;
 }
 
+void MPI_CORE(mul)( mbedtls_mpi_uint *X,
+                    const mbedtls_mpi_uint *A, size_t a,
+                    const mbedtls_mpi_uint *B, size_t b )
+{
+    memset( X, 0, ( a + b ) * ciL );
+    for( size_t i=0; i < b; i++ )
+        (void) mbedtls_mpi_core_mla( X + i, a + 1, A, a, B[i] );
+}
+
 /*
  * Fast Montgomery initialization (thanks to Tom St Denis).
  */
diff --git a/library/bignum_core.h b/library/bignum_core.h
index 05bc923d2..f66db8fd4 100644
--- a/library/bignum_core.h
+++ b/library/bignum_core.h
@@ -398,6 +398,25 @@ mbedtls_mpi_uint mbedtls_mpi_core_mla(mbedtls_mpi_uint *X, size_t X_limbs,
                                       const mbedtls_mpi_uint *A, size_t A_limbs,
                                       mbedtls_mpi_uint b);
 
+#define MPI_CORE(func) mbedtls_mpi_core_ ## func ## _minimal
+
+/**
+ * \brief Perform a known-size multiplication
+ *
+ * \param[out] X        The pointer to the (little-endian) array
+ *                      representing the product of \p a and \p b.
+ *                      This must be of length \p a + \p b.
+ * \param[in] A         The pointer to the (little-endian) array
+ *                      representing the first factor.
+ * \param a             The number of limbs in \p A.
+ * \param[in] B         The pointer to the (little-endian) array
+ *                      representing the second factor.
+ * \param b             The number of limbs in \p B.
+ */
+void MPI_CORE(mul)( mbedtls_mpi_uint *X,
+                    const mbedtls_mpi_uint *A, size_t a,
+                    const mbedtls_mpi_uint *B, size_t b );
+
 /**
  * \brief Calculate initialisation value for fast Montgomery modular
  *        multiplication