Multilevel Secrecy over 1-2-1 Networks

This paper studies the problem of secure communication over noiseless 1-2-1 networks, an abstract model for networks with directional communication capabilities such as mmWave networks. A secure transmission scheme is designed and shown to achieve a secure rate that is larger than state-of-the-art lower bounds for a class of 1-2-1 network topologies. The proposed scheme leverages the scheduling nature of 1-2-1 networks, the network topology, as well as storage at intermediate nodes to create shared randomness with the source to improve the secure rate. Finally, a novel outer bound is derived and shown to match the achievability bound under certain network conditions, hence characterizing the secure capacity in such regimes.