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IET Communications

Secure communications with untrusted relays: a multi‐pair two‐way relaying approach

Tantan Zhao, Guobing Li, Gangming Lv, Yizhen Zhang

Published Sep 13, 2018• 4 citations
Publisher

Abstract

Physical‐layer security is usually ensured by the injection of artificial noise (AN) at the legitimate source or destination when relays are cooperative but untrusted. In this work, in order to avoid the power‐consuming AN at the legitimate user pairs, the authors investigate multi‐pair two‐way relaying as a solution for secure transmission in wireless relay networks with untrusted relays. They formulate a generalised problem for the joint design of cooperative beamforming (CB) and AN at relays to maximise the secrecy sum‐rate in wireless networks with multi‐pair legal users, multiple untrusted relays as well as multiple non‐colluding eavesdroppers. Further, they reformulate, approximate and relax the original non‐convex problem into a sequence of convex sub‐problems based on semi‐definite relaxation (SDR) and Taylor series approximation. Particularly, for the reformulated problem they prove that the SDR is in fact tight, and hence propose an iterative algorithm for CB and AN design at the relays. In the simulations, they demonstrate the fast convergence and high achievable secrecy sum‐rate of the proposed algorithm. Also, they simulate and discuss the impact of the number of user pairs on the secrecy sum‐rate, and reveal the change of performance gain with the number of multiple user pairs.

DOI
10.1049/iet-com.2018.5640

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Physical‐layer security is usually ensured by the injection of artificial noise (AN) at the legitimate source or destination when relays are cooperative but untrusted. In this work, in order to avoid the power‐consuming AN at the legitimate user pairs, the authors investigate multi‐pair two‐way relaying as a solution for secure transmission in wireless relay networks with untrusted relays. They formulate a generalised problem for the joint design of cooperative beamforming (CB) and AN at relays to maximise the secrecy sum‐rate in wireless networks with multi‐pair legal users, multiple untrusted relays as well as multiple non‐colluding eavesdroppers. Further, they reformulate, approximate and relax the original non‐convex problem into a sequence of convex sub‐problems based on semi‐definite relaxation (SDR) and Taylor series approximation. Particularly, for the reformulated problem they prove that the SDR is in fact tight, and hence propose an iterative algorithm for CB and AN design at the relays. In the simulations, they demonstrate the fast convergence and high achievable secrecy sum‐rate of the proposed algorithm. Also, they simulate and discuss the impact of the number of user pairs on the secrecy sum‐rate, and reveal the change of performance gain with the number of multiple user pairs.
This paper studies cooperative secure transmission in wireless relay networks, where a source sends a confidential message to a legitimate destination through a set of amplify-and-forward (AF) relays in the presence of multiple eavesdroppers. To prevent the eavesdroppers from retrieving the message, we assume that the relays employ a joint cooperative beamforming (CB) and artificial noise (AN) strategy. Under both the total and individual relay power constraints, we propose an optimal joint CB-AN design based on secrecy rate maximization (SRM). We treat the SRM problem by a combination of two-level optimization and semidefinite relaxation (SDR). For the latter, we prove that SDR always has a rank-one solution for the SRM problem - which identifies that SDR is optimal. Simulation results are presented to show the efficacy of the proposed joint CB-AN design.
Abstract In this paper, the selective cooperation with untrusted relays is studied for wireless multipair two‐way relay networks. We first investigate the feasibility of secure transmission in the presence of cooperative but untrusted relays and then formulate a general optimization problem of secrecy sum‐rate maximization under the constraints of relay selection. By decomposing the original problem into solvable subproblems, we develop a low‐complexity greedy algorithm for selective cooperation, in which the untrusted relays are selected as cooperators or the potential eavesdroppers according to the overall contributions to the secrecy sum rate. Simulation results reveal that the proposed greedy algorithm for selective cooperation with untrusted relays achieves performance gain both in instantaneous and average secrecy sum rate and that the algorithm can converge quickly with the iterations.
In this paper, we address physical layer security for amplify-and-forward (AF) multi-antenna relay systems in the presence of multiple eavesdroppers. A robust joint design of cooperative beamforming (CB) and artificial noise (AN) is proposed with imperfect channel state information (CSI) of both the destination and the eavesdroppers. We aim to maximize the worst-case secrecy rate subject to the sum power and the per-antenna power constraints at the relay. Such joint design problem is non-convex. By utilizing the semidefinite relaxation (SDR) technique, S-procedure and the successive convex approximation (SCA) algorithm, the original non-convex optimization problem is recast into a series of semidefinite programs (SDPs) which can be efficiently solved using interior-methods. Simulation results are presented to verify the effectiveness of the proposed design.
In this letter, a joint design of cooperative beamforming (CB) and artificial noise (AN) is proposed for two-way amplify-and-forward (AF) relay networks to improve the security of the date exchange. Based on secrecy sum rate maximization (SSRM) criterion, such joint design problem under individual relay power constraints is mathematically hard due to the non-convex objective function. By utilizing the semidefinite relaxation (SDR) technique and successive convex approximation (SCA) algorithm, we efficiently develop a stationary point for the original SSRM design problem. Proof is also given to show that SDR is always tight and yields a rank-one solution. Simulations are presented to validate the efficiency and merits of our proposed joint CB and AN design in enhancing the secrecy sum rate.
We investigate the physical-layer security problems of two-way relay networks in this paper. The whole network consists of two legitimate users and one eavesdropper, where the legal users need the help of some intermediate nodes to exchange information. We propose joint jamming and relaying mechanism, where a jamming node is selected from all intermediate nodes, to create interference upon eavesdropper, while other nodes are used to relay data for two users. All intermediate nodes are subjected to per-node power constraints. Based on null-space beamforming, we propose two different transmission schemes when the number of relay nodes is large enough. One scheme is designed to maximize the secrecy sum rate (MSSR) of the network, and the other is designed to maximize the minimum secrecy rate (MMSR) between two users. In the MMSR scheme, a series of semi-definite programming problems with a rank-1 constraint needs to be solved. We prove that this rank-1 constraint does not affect the solutions of original problems. In addition, we propose two modified secure transmission schemes when the number of relay nodes is less abundant. In short, no matter how many intermediate nodes in the communication networks, one can find suitable transmission schemes to ensure communication security.
In this study, physical layer security techniques are studied for multi‐user peer‐to‐peer relay networks using amplify‐and‐forward protocol in the presence of an eavesdropper. Two system designs are considered: the minimum achievable secrecy rate maximisation and the total transmit power minimisation. First, considering user fairness, the authors study the max–min achievable secrecy rate problem subject to a total transmit power constraint. Mathematically, the optimisation problem is non‐linear and non‐convex. They propose a polynomial time algorithm based on the bisection technique to solve it. Second, they study the total transmit power minimisation problem which aims at minimising the total transmit power at relays such that individual secrecy rate for each user is satisfied. The total power optimisation problem is also non‐convex, so they use the relaxation technique to transform it into a convex problem which can be efficiently solved by the gradient‐based algorithms. Numerical evaluation of the obtained secrecy rate and transmit power results shows that the proposed designs can significantly improve the performance of secure wireless communications.