Physical-level secure wireless communication using random-signal-excited reprogrammable metasurface

Security is a critical issue in wireless communication due to the broadcast nature of the wireless environment; thus, physical-level secure wireless communication is of great importance in modern society, especially with the advent of the Internet-of-Things, fifth-generation, and beyond. In this Letter, we present an efficient scheme of physical-level secure wireless communication by exploring the reprogrammable metasurface excited with random signals at the transmission side (Alice) and the dual-receiver decoding method at the receiving side (Bob). To that end, the bit stream to be transferred is first encoded into the reprogrammable metasurface on the physical level, then the information-carrying metasurface is excited by a sequence of random radio signals; finally, Alice's information is retrieved by processing coherently the random signals acquired by two receivers at Bob. It is apparent that the eavesdropper (Eve) with a single antenna somewhere only receives the noise radiated from the metasurface and cannot decode the information correctly. Note that the reprogrammable metasurface with the time-space coding pattern shows the information-dependent radiation pattern, i.e., different noises in different directions. Therefore, our wireless communication method is also effective to the eavesdropper with multiple antennas. We implement a proof-of-principle system working at around 2.442 GHz and demonstrate experimentally that the proposed method enables to transmit the Mbps-rate bitstream. Our work will pave the way toward next-generation secure wireless communication.