Secrecy Capacity of Two-Hop Relay Assisted Wiretap Channels

Abstract

Incorporating the physical layer characteristics to secure communications has received considerable attention in recent years. Moreover, cooperation with some nodes of network can give benefits of multiple-antenna systems, increasing the secrecy capacity of such channels. In this paper, we consider cooperative wiretap channel with the help of an Amplify and Forward (AF) relay to transmit confidential messages from source to legitimate receiver in the presence of an eavesdropper. In this regard, the secrecy capacity of AF relying is derived, assuming the relay is subject to a peak power constraint. To this end, an achievable secrecy rate for Gaussian input is evaluated through solving a non-convex optimization problem. Then, it is proved that any rates greater than this secrecy rate is not achievable. To do this, the capacity of a genie-aided channel as an upper bound for the secrecy capacity of the underlying channel is derived, showing this upper bound is equal to the computed achievable secrecy rate with Gaussian input. Accordingly, the corresponding secrecy capacity is compared to the Decode and Forward (DF) strategy which is served as the benchmark in the current work.Index Terms-Secrecy capacity, achievable secrecy rate, physical layer security, cooperative wiretap channel.

Optimal power allocation for physical layer security in device‐to‐device communications using untrusted relays

“…In Figure , ESR in terms of ρ in WJ scenario is evaluated for OPA and non‐OPA modes in the first phase for topologies T1 and T2, and for untrusted relays and trusted relays. In this figure, the untrusted relay scenario in this paper is compared with the trusted relay mentioned in other works . It is assumed that in the second phase, OPA has been done for ξ = ξ * .…”

“…In this figure, the untrusted relay scenario in this paper is compared with the trusted relay mentioned in other works. [4][5][6][7][8][9][10][11][12][13] It is assumed that in the second phase, OPA has been done for ξ = ξ * . Simulation results show that ESR in T1 for OPA mode is totally consistent with trusted relay mode since in this mode, the relay plays no role in providing a D2D connection and acts only as an eavesdropper.…”

“…A long this line, we proceed to the OPA problem and secrecy rate analysis for the mentioned scenarios under two topologies T1 and T2. So far, the relays assisted cellular communications, [3][4][5][6][7][8][9][10][11][12][13] D2D communication using trusted relays, 22,26,27 and the security in cellular and D2D communications [14][15][16][17][18]23,28 are investigated. Here, we consider an overlay D2D pair that communicates with each other through an untrusted AF relay, where in addition to helping data transmission also plays the role of the eavesdropper.…”

“…This method requires double coding of the transmitted signal. Mirzaee and Akhlaghi and Fang et al examine secure transmission between a transmitter and a receiver through an amplify‐and‐forward (AF) relay in the presence of an eavesdropper. In the work of Mirzaee and Akhlaghi, by using power assignment among the relays, some results for the optimal power allocation (OPA) have been obtained and it is shown that OPA will improve the secrecy rate.…”

“…Mirzaee and Akhlaghi and Fang et al examine secure transmission between a transmitter and a receiver through an amplify‐and‐forward (AF) relay in the presence of an eavesdropper. In the work of Mirzaee and Akhlaghi, by using power assignment among the relays, some results for the optimal power allocation (OPA) have been obtained and it is shown that OPA will improve the secrecy rate. Two cooperative jamming protocols have been proposed in the work of Fang et al, where the confidentially of communication is supported by sending the jamming signal either by the transmitter or the relay.…”