diff --git a/library/bignum.c b/library/bignum.c
index 55325b4..870365d 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -39,6 +39,7 @@
 
 #include "mbedtls/bignum.h"
 #include "bignum_internal.h"
+#include "bignum_core.h"
 #include "bn_mul.h"
 #include "mbedtls/platform_util.h"
 #include "mbedtls/error.h"
@@ -57,24 +58,8 @@
 #define mbedtls_free       free
 #endif
 
-#define MPI_VALIDATE_RET( cond )                                       \
-    MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_MPI_BAD_INPUT_DATA )
-#define MPI_VALIDATE( cond )                                           \
-    MBEDTLS_INTERNAL_VALIDATE( cond )
-
-#define ciL    (sizeof(mbedtls_mpi_uint))         /* chars in limb  */
-#define biL    (ciL << 3)               /* bits  in limb  */
-#define biH    (ciL << 2)               /* half limb size */
-
 #define MPI_SIZE_T_MAX  ( (size_t) -1 ) /* SIZE_T_MAX is not standard */
 
-/*
- * Convert between bits/chars and number of limbs
- * Divide first in order to avoid potential overflows
- */
-#define BITS_TO_LIMBS(i)  ( (i) / biL + ( (i) % biL != 0 ) )
-#define CHARS_TO_LIMBS(i) ( (i) / ciL + ( (i) % ciL != 0 ) )
-
 /* Implementation that should never be optimized out by the compiler */
 static void mbedtls_mpi_zeroize( mbedtls_mpi_uint *v, size_t n )
 {