Group Secret Key Distribution Based on Physical-Layer Key Generation and NOMA-Assisted Downlink

In this paper, we propose a novel non-orthogonal multiple access (NOMA)-based physical-layer group secret key distribution (GSKD) for a star network in the presence of an eavesdropper. In the proposed scheme, a random group secret key generated at a base station (BS) is distributed to legitimate users in an information-theoretically secure manner. More specifically, the BS and each user share a secret key from the associated channel state information (CSI), which is then used to encrypt the group secret key with a one-time pad. Then, each of the encrypted group secret keys is superimposed and efficiently broadcast to the users in the NOMA downlink. Moreover, we derive the theoretical group key rate bound of the proposed scheme. Our performance results demonstrate that the proposed NOMA-based GSKD scheme outperforms the conventional benchmark schemes.