We propose a method to conceal data on a physical layer of the OSI reference model by disturbing them with some random noises, and moreover, a method to restore the concealed data to the original ones by using the noise filtering based on a proper stochastic filtering theory. Our concealing-restoring system manages the data from the data link layer of the OSI reference model... Although we introduced a linear concealing-restoring system in our previous work, we study its nonlinearization and improve the security of the concealing-restoring system in this paper. (read more)