Practical Physical-Layer Group Secret-Key Generation in Three-User Wireless Networks

摘要

Group secret-key (GSK) generation using temporal variation in wireless channels is an effective way of synthesizing symmetric keys across multiple nodes (more than two) in wireless networks. Unlike the case of two-node key-generation, GSK generation necessitates some nodes to act as facilitators by transmitting linear combinations of the channel realizations. However, in practice, radio devices are designed to transmit baseband signals from finite complex constellations. Due to such constraints, the linear combinations of channel realizations are typically quantized by the facilitator which in turn impacts the overall secret-key rate. Identifying this issue, we propose a practical GSK generation protocol in a network of three nodes. Under special conditions, we analytically show that the proposed method provides higher key-rate than the case when only the facilitator quantizes the channel realizations before transmission. Through simulations, we show that the proposed method yields higher key-rate than the baselines when the facilitator employs finite constellations such as 4-, 16-, and 64-QAM.