A New Secrecy Metric for Relay-Eavesdropper Channel

This paper investigates a relay-eavesdropper channel with orthogonal components from the source to the relay and from the source and relay to the destination, where the eavesdropper can eavesdrop on either one or both of two orthogonal channels depending on its receiving capabilities. We first present a new information-theoretic metric called symbol secrecy, which, in contrast to Wyner’weak secrecy defining perfect secrecy as an average information leakage rate approaching 0, provides a new standard to analyze the secrecy performance of the relayeavesdropper channel based on the number of leaked symbols. Then, we present a list-source coding scheme, based on which to acquire the outer bound of $\epsilon$-symbol secrecy of the relayeavesdropper channel model. Extensive theoretical proofs are also provided to demonstrate our significant findings.