On the Achievable Secrecy Diversity of Cooperative Networks With Untrusted Relays

Abstract

Cooperative relaying is often deployed to enhance the communication reliability (i.e., diversity order) and consequently the end-to-end achievable rate. However, this raises several security concerns when the relays are untrusted since they may have access to the relayed message. In this paper, we study the achievable secrecy diversity order of cooperative networks with untrusted relays. In particular, we consider a network with an N -antenna transmitter (Alice), K single-antenna relays, and a single-antenna destination (Bob). We consider the general scenario where there is no relation between N and K, and therefore K can be larger than N . Alice and Bob are assumed to be far away from each other, and all communication is done through the relays, i.e., there is no direct link. Providing secure communication while enhancing the diversity order has been shown to be very challenging. In fact, it has been shown in the literature that the maximum achievable secrecy diversity order for the adopted system model is one (while using artificial noise jamming). In this paper, we adopt a nonlinear interference alignment scheme that we have proposed recently to transmit the signals from Alice to Bob. We analyze the proposed scheme in terms of the achievable secrecy rate and secrecy diversity order. Assuming Gaussian inputs, we derive an explicit expression for the achievable secrecy rate and show analytically that a secrecy diversity order of up to minpN, Kq´1 can be achieved using the proposed technique. We provide several numerical examples to validate the obtained analytical results and demonstrate the superiority of the proposed technique to its counterparts that exist in the literature. Index Terms-Cooperative networks, interference alignment, interference dissolution, secrecy diversity, untrusted relays.M. Chraiti is with the

Buffer‐aided relaying: a survey on relay selection policies

“…Similar to the case of external eavesdropper, the best relaying scheme depends on the physical outline of the system, mainly the distances between the nodes [126]. Another scheme with multiple un‐trusted relays [105] implements multiple antennas at the transmitter relay to attain a secrecy diversity order of (min( N , K )), where K , the number of single antenna relays, is larger than N , the number of antennas in the transmitter. Chraiti et al [105] utilise pre‐coding signals non‐linearly with the channel gains in a way that only the destination will be capable of separating interfering signals in an efficient manner.…”

“…Another scheme with multiple un‐trusted relays [105] implements multiple antennas at the transmitter relay to attain a secrecy diversity order of (min( N , K )), where K , the number of single antenna relays, is larger than N , the number of antennas in the transmitter. Chraiti et al [105] utilise pre‐coding signals non‐linearly with the channel gains in a way that only the destination will be capable of separating interfering signals in an efficient manner. This scheme does not exploit any type of AN, leading to remarkable power savings compared with those that do [105].…”

“…Chraiti et al [105] utilise pre‐coding signals non‐linearly with the channel gains in a way that only the destination will be capable of separating interfering signals in an efficient manner. This scheme does not exploit any type of AN, leading to remarkable power savings compared with those that do [105].…”

Impact of Outdated CSI on the Secrecy Performance of Multiple Untrusted Relay Networks with Direct Link and Destination-Based Jamming

“…where and refers to the index of the selected relay, , according to the criterion presented in the next section. In addition, after performing a MRC technique, the instantaneous received end-to-end SINR at D is given by (10) Herein, we consider that the RSI channel is not time varying, as there is no relative movement of the collocated transmit and receive antennas at D, so that the RSI channel is not subject to outdated CSI. Also, in this system, any relay node is considered a potential eavesdropper, thus being untrustworthy.…”

“…In particular, in [9], a source-based jamming technique was evaluated in combination with power allocation to improve the security in a network with one untrusted relay and the presence of direct link between source and destination. In [10], the achievable secrecy diversity order was studied for a cooperative network with a multiple-antenna source and multiple untrusted relays. In [11], the secrecy capacity and the secrecy outage probability (SOP) of a two-hop amplify-and-forward (AF) relaying network was evaluated in the presence of multiple untrusted relays and without the presence of direct link.…”