diff --git a/library/bn_mul.h b/library/bn_mul.h
index 17d057f..bf45193 100644
--- a/library/bn_mul.h
+++ b/library/bn_mul.h
@@ -44,6 +44,46 @@
 
 #include "mbedtls/bignum.h"
 
+
+/*
+ * Conversion macros for embedded constants:
+ * build lists of mbedtls_mpi_uint's from lists of unsigned char's grouped by 8, 4 or 2
+ */
+#if defined(MBEDTLS_HAVE_INT32)
+
+#define BYTES_TO_T_UINT_4( a, b, c, d )                       \
+    ( (mbedtls_mpi_uint) (a) <<  0 ) |                        \
+    ( (mbedtls_mpi_uint) (b) <<  8 ) |                        \
+    ( (mbedtls_mpi_uint) (c) << 16 ) |                        \
+    ( (mbedtls_mpi_uint) (d) << 24 )
+
+#define BYTES_TO_T_UINT_2( a, b )                   \
+    BYTES_TO_T_UINT_4( a, b, 0, 0 )
+
+#define BYTES_TO_T_UINT_8( a, b, c, d, e, f, g, h ) \
+    BYTES_TO_T_UINT_4( a, b, c, d ),                \
+    BYTES_TO_T_UINT_4( e, f, g, h )
+
+#else /* 64-bits */
+
+#define BYTES_TO_T_UINT_8( a, b, c, d, e, f, g, h ) \
+    ( (mbedtls_mpi_uint) (a) <<  0 ) |                        \
+    ( (mbedtls_mpi_uint) (b) <<  8 ) |                        \
+    ( (mbedtls_mpi_uint) (c) << 16 ) |                        \
+    ( (mbedtls_mpi_uint) (d) << 24 ) |                        \
+    ( (mbedtls_mpi_uint) (e) << 32 ) |                        \
+    ( (mbedtls_mpi_uint) (f) << 40 ) |                        \
+    ( (mbedtls_mpi_uint) (g) << 48 ) |                        \
+    ( (mbedtls_mpi_uint) (h) << 56 )
+
+#define BYTES_TO_T_UINT_4( a, b, c, d )             \
+    BYTES_TO_T_UINT_8( a, b, c, d, 0, 0, 0, 0 )
+
+#define BYTES_TO_T_UINT_2( a, b )                   \
+    BYTES_TO_T_UINT_8( a, b, 0, 0, 0, 0, 0, 0 )
+
+#endif /* bits in mbedtls_mpi_uint */
+
 #if defined(MBEDTLS_HAVE_ASM)
 
 #ifndef asm