Add ECDH primitives
diff --git a/include/polarssl/ecp.h b/include/polarssl/ecp.h
index e1b0995..b8b1997 100644
--- a/include/polarssl/ecp.h
+++ b/include/polarssl/ecp.h
@@ -147,12 +147,23 @@
 /**
  * \brief           Set a point to zero
  *
+ * \param pt        Destination point
+ *
  * \return          0 if successful,
  *                  POLARSSL_ERR_MPI_MALLOC_FAILED if memory allocation failed
  */
 int ecp_set_zero( ecp_point *pt );
 
 /**
+ * \brief           Tell if a point is zero
+ *
+ * \param pt        Point to test
+ *
+ * \return          1 if point is zero, 0 otherwise
+ */
+int ecp_is_zero( ecp_point *pt );
+
+/**
  * \brief           Copy the contents of point Q into P
  *
  * \param P         Destination point