Cross-layer security in two-hop wireless Gaussian relay network with untrusted relays

This paper deals with the challenge of providing information-theoretic secrecy in a two-hop wireless channel with multiple untrusted relay nodes. Instead of perfect secrecy (in the information-theoretic sense), of interest here is a cross-layer approach where only parts of relayed information are protected at the physical layer against eavesdropping at relay nodes. For both decode-and-forward and amplify-and-forward relaying strategies, we present a novel framework for designing secrecy schemes for two-hop relay channels that ensure some predefined level of partial secrecy. The paper is concluded by some numerical simulations to show the interplay between different system parameters such as the the rate, secrecy factor, the number of relays and antennas.