diff --git a/library/common.h b/library/common.h
index 9b10ec8..8dfa816 100644
--- a/library/common.h
+++ b/library/common.h
@@ -227,6 +227,78 @@
 #endif
 
 /**
+ * Get the unsigned 24 bits integer corresponding to four bytes in
+ * big-endian order (MSB first).
+ *
+ * \param   data    Base address of the memory to get the four bytes from.
+ * \param   offset  Offset from \p base of the first and most significant
+ *                  byte of the four bytes to build the 24 bits unsigned
+ *                  integer from.
+ */
+#ifndef MBEDTLS_GET_UINT24_BE
+#define MBEDTLS_GET_UINT24_BE( data , offset )                  \
+    (                                                           \
+          ( (uint32_t) ( data )[( offset )    ] << 16 )         \
+        | ( (uint32_t) ( data )[( offset ) + 1] << 8  )         \
+        | ( (uint32_t) ( data )[( offset ) + 2]       )         \
+    )
+#endif
+
+/**
+ * Put in memory a 24 bits unsigned integer in big-endian order.
+ *
+ * \param   n       24 bits unsigned integer to put in memory.
+ * \param   data    Base address of the memory where to put the 24
+ *                  bits unsigned integer in.
+ * \param   offset  Offset from \p base where to put the most significant
+ *                  byte of the 24 bits unsigned integer \p n.
+ */
+#ifndef MBEDTLS_PUT_UINT24_BE
+#define MBEDTLS_PUT_UINT24_BE( n, data, offset )                \
+{                                                               \
+    ( data )[( offset )    ] = MBEDTLS_BYTE_2( n );             \
+    ( data )[( offset ) + 1] = MBEDTLS_BYTE_1( n );             \
+    ( data )[( offset ) + 2] = MBEDTLS_BYTE_0( n );             \
+}
+#endif
+
+/**
+ * Get the unsigned 24 bits integer corresponding to four bytes in
+ * little-endian order (LSB first).
+ *
+ * \param   data    Base address of the memory to get the four bytes from.
+ * \param   offset  Offset from \p base of the first and least significant
+ *                  byte of the four bytes to build the 24 bits unsigned
+ *                  integer from.
+ */
+#ifndef MBEDTLS_GET_UINT24_LE
+#define MBEDTLS_GET_UINT24_LE( data, offset )                   \
+    (                                                           \
+          ( (uint32_t) ( data )[( offset )    ]       )         \
+        | ( (uint32_t) ( data )[( offset ) + 1] <<  8 )         \
+        | ( (uint32_t) ( data )[( offset ) + 2] << 16 )         \
+    )
+#endif
+
+/**
+ * Put in memory a 24 bits unsigned integer in little-endian order.
+ *
+ * \param   n       24 bits unsigned integer to put in memory.
+ * \param   data    Base address of the memory where to put the 24
+ *                  bits unsigned integer in.
+ * \param   offset  Offset from \p base where to put the least significant
+ *                  byte of the 24 bits unsigned integer \p n.
+ */
+#ifndef MBEDTLS_PUT_UINT24_LE
+#define MBEDTLS_PUT_UINT24_LE( n, data, offset )                \
+{                                                               \
+    ( data )[( offset )    ] = MBEDTLS_BYTE_0( n );             \
+    ( data )[( offset ) + 1] = MBEDTLS_BYTE_1( n );             \
+    ( data )[( offset ) + 2] = MBEDTLS_BYTE_2( n );             \
+}
+#endif
+
+/**
  * Get the unsigned 64 bits integer corresponding to eight bytes in
  * big-endian order (MSB first).
  *