Abstract : We address relay-assisted key generation whereintwo wireless nodes, that have no direct channel between them,seek the assistance of an intermediate relay to generate secretkeys. In a celebrated version of the relay-assisted protocol, asapplied by Lai et al., Zhou et al., Wang et al., and Waqas etal., the relay node generates pair-wise keys with the two nodes,and then broadcasts an XOR version of the two keys. Althoughsuch protocols are simple and effective, we observe that theyface reduction in key rates due to two problems. First, forconfidentiality, the relay broadcasts an XOR function of the pairwisekeys thereby pruning the length of the shared key to be theminimum of the key lengths of the pair-wise keys. Secondly, thebroadcast phase may also experience outages thereby not beingable to share the generated key in every round of the protocol.Identifying these issues, we propose a buffer-aided relayingprotocol wherein buffer is used at the relay to store unusedsecret bits generated in the previous rounds of the protocol so asto provide confidentiality in the subsequent rounds of broadcast.On this buffer-aided protocol, we propose a power-allocationstrategy between the phases of key generation and broadcast soas to maximize the throughput and key rate. Rigorous analysesshow that buffer-aided relay when implemented along with theproposed power-allocation strategy offer remarkable advantagesover existing baselines.
Index terms : Buffers, key generation, power-allocation.