Secret Group-Key Generation at Physical Layer for Multi-Antenna Mesh Topology

In this paper, we propose a secret group-key generation scheme in physical layer, where an arbitrary number of multi-antenna LNs (LN) exist in mesh topology with a multi-antenna passive eavesdropper. In the first phase of the scheme, pilot signals are transmitted from selected antennas of all nodes and each node estimates channels linked to it. In the second phase, each node sequentially broadcasts a weighted combination of the estimated channel information using selected coefficients. The other LNs can obtain the channel information used for group-key generation while the eavesdropper cannot. Each node then can generate a group key by quantizing and encoding the estimated channels into keys. We apply well-known quantization schemes, such as scalar and vector quantizations, and compare their performance. To further enhance the key-generation performance, we also provide how to determine the antennas at each node used for group-key generation and the coefficients used in the broadcast phase. The simulation results verify the performance of the proposed secret group-key generation scheme using various key-related metrics. We also verify the practical robustness of our scheme by implementing a testbed using universal software radio peripheral. After generating secret common key among three nodes, we also test it using the National Institute of Standards and Technology test suit. The generated key passes the test and it is random enough for communication secrecy.