A Recovery-Mechanism-Driven Wireless Group Key Generation Protocol for Multiuser Scenarios

Physical-layer key generation (PKG) leveraging the reciprocity of wireless channel provides an effective approach for key agreement among resource-constrained Internet of Things devices. However, current researches on PKG predominantly focus on pairwise communication scenarios, and there remain challenges in achieving group key generation for multiuser scenarios. In this article, we propose a novel recovery mechanism-driven wireless group key generation protocol to facilitate key sharing in the star network typology. Specifically, the root node will assign each member node its unique group key component before initiating group key distribution. Subsequently, all group key components are distributed to member nodes using a forward error correction mechanism, which helps reduce system overhead. Finally, all member nodes utilize a recovery mechanism and their respective group key component to obtain the same complete group key, thereby achieving group key distribution. Compared to existing schemes, our protocol can avoid the significant information leakage caused by repeated distribution of the same group key, thereby enhancing security. We further design and implement a practical wireless group key generation system using ESP32. Additionally, a group channel state information (CSI) extraction tool for multiuser channel measurements is developed. Experimental results demonstrate that our protocol can generate the group key with high randomness while benefiting from good channel reciprocity, making it suitable for cryptographic applications in multiuser communication scenarios.