Cooperative Group Key Generation Using IR-UWB Multipath Channels

In wireless decentralized networks, nodes physically close to each other can take advantage of the shared wireless medium to generate common secrets or keys and enhance the security of communications. Previous studies already provided models, algorithms, and proofs of concept to exploit the radio physical layer and generate symmetric keys over single links. Some of these models have been adapted to cooperative scenarios involving several nodes, either to reinforce the generated pair-wise keys or to issue a common group key (i.e., shared by more than two nodes). In this study, we focus on key agreement from Impulse Radio - Ultra Wideband (IR-UWB) multipath channels according to the source model. We propose a new method to generate group keys within cooperative scenarios, while exploiting all the available physical links in a full mesh topology and reducing over-the-air traffic. The main idea consists in adjusting the IR-UWB signals usually transmitted for channel probing so that receiving nodes have access to non-observable channels corresponding to their non-adjacent links. We describe an example where the transmitted signal is optimized using a least squares minimization routine with prior information.