Security is a demanding request for wireless networks, with physical layer security the problems in traditional encryption algorithms and key management are vanished. In this paper, a novel beamforming scheme is proposed to improve secrecy rate in an untrusted relay network, where the untrusted relay helps to improve the network coverage area but may act as a potential eavesdroper. A destination-assisted-jamming (DAJ) is used to protect the confidential information against untrusted relays and eavesdroppers. By optimizing beamforming, we align the confidential signal to the equivalent valid signal space and force it to be orthogonal to the cooperative jamming signal space. The correctness and efficiency of the proposed beamforming scheme are validated by numerical simulations.
Security is a demanding request for wireless networks, with physical layer security the problems in traditional encryption algorithms and key management are vanished. In this paper, a novel beamforming scheme is proposed to improve secrecy rate in an untrusted relay network, where the untrusted relay helps to improve the network coverage area but may act as a potential eavesdroper. A destination-assisted-jamming (DAJ) is used to protect the confidential information against untrusted relays and eavesdroppers. By optimizing beamforming, we align the confidential signal to the equivalent valid signal space and force it to be orthogonal to the cooperative jamming signal space. The correctness and efficiency of the proposed beamforming scheme are validated by numerical simulations.
Destination-assisted jamming (DAJ) is usually used to protect confidential information against untrusted relays and eavesdroppers in wireless networks. In this paper, a DAJ-based untrusted relay network with multiple antennas installed is presented. To increase the secrecy, a joint optimization of beamforming and power allocation at the source and destination is studied. A matched-filter precoder is introduced to maximize the cooperative jamming signal by directing cooperative jamming signals toward untrusted relays. Then, based on generalized singular-value decomposition (GSVD), a novel transmitted precoder for confidential signals is devised to align the signal into the subspace corresponding to the confidential transmission channel. To decouple the precoder design and optimal power allocation, an iterative algorithm is proposed to jointly optimize the above parameters. Numerical results validate the effectiveness of the proposed scheme. Compared with other schemes, the proposed scheme shows significant improvement in terms of security performance.
In this paper, a joint beamforming alignment and suboptimal power allocation (Sub-OPA) for a two-way untrusted relay network is presented. Considering the link between users is established via only an untrusted relay because of either the shadowing fading or long distance between users, we utilize a destination-assisted-jamming (DAJ) technique to improve the security performance. In each time slot, a user transmits confidential signals and the other emits jamming signals simultaneously to prevent the untrusted relay from intercepting the confidential signals. First, we design a novel beamforming to align the confidential signal to the subspace corresponding to the confidential transmission channel and direct the cooperative jamming signal toward untrusted relay. Then, an iterative algorithm is presented to generate the Sub-OPA of each user for the transmission of confidential and cooperative jamming signal. The correctness and efficiency of the proposed beamforming scheme and the Sub-OPA are validated by numerical simulations and the results are compared via MatLab optimization toolbox. Moreover, the simulations show the iterative algorithm is converged after the fourth iteration at lower signal-to-noise ratios (SNRs) and rapidly converged with allocating more power to the confidential signals at higher SNRs.
The broadcast nature of wireless communications makes the propagation medium vulnerable to security attacks such as eavesdropping and jamming from adversarial or unauthorized users. Applying physical layer secrecy approaches will enable the exchange of confidential messages over a wireless medium in the presence of unauthorized eavesdroppers, without using any secret keys. However, physical layer security approaches are typically feasible only when the source-eavesdropper channel is weaker than the source-destination channel. Cooperative jamming can be used to overcome this challenge and increase the secrecy rate. In this paper, the security of two-phase relaying system with multiple intermediate nodes and in the presence of an eavesdropper is investigated. To enhance the system secrecy rate, a joint cooperative beamforming and jamming combined with relay and jammer selections is proposed. In phase I, the source node broadcasts a signal to relays while three intermediate nodes (which act as jammers) help the source node by transmitting random jamming signals to confuse the eavesdropper. Since the friendly (cooperative) jammers create interference for both the intended relays and the eavesdropper, optimal beamforming is applied such that no interference is caused at two preselected desired relays (that are going to receive the confidential massage in phase I). In phase II, two preselected relays transmit the source message with beamforming coefficients such that the received signal at the eavesdropper is completely nulled out. Our goal in this paper is to minimize the received SNR at the eavesdropper while increasing it at the destination as much as possible by applying different methods such as cooperative beamforming, cooperative jamming and relay selection. To avoid operational complexity, we consider the minimum number of intermediate nodes that are necessary without losing the performance. Numerical results demonstrate the advantage of our proposed scheme compared with the scheme with no cooperative jamming.
In this paper, we propose a destination-assisted jamming and beamforming (DAJB) scheme for physical layer security in a one-way cooperative amplify-and-forward (AF) relay communication system. The system model consists of one source, one destination, one eavesdropper, and N relay nodes, with the individual power constraint of each relay node and the destination-assisted jamming node as well as unknown instantaneous channel state information (CSI) of the eavesdropper. Due to the half-duplex constraint of the relay nodes, there are two phases in our proposed DAJB scheme. In the first phase, the source node broadcasts information signal and all N relay nodes listen simultaneously. In the meantime, the destination node transmits the jamming signal to confuse the potential eavesdropper. In the second phase, all N relay nodes amplify and forward the received signals, covered by the artificial noise (AN), to the destination using the distributed beamforming technology. The optimal beamformer weights and power allocation are obtained by solving the second-order convex cone programming (SOCP) together with a linear programming (LP) problem. Furthermore, the performance of the DAJB scheme is analyzed in terms of the achievable secrecy rate. Compared with the scheme that selects a relay node as the jammer, we obtain larger power gain to achieve higher secrecy rates. Finally, the simulation results verify that the DAJB scheme greatly improves the secrecy rate of a one-way cooperative AF relay communication system.
This paper proposes a joint cooperative relaying and jamming scheme based on distributed beamforming to enhance the secrecy rate of a wireless channel in the presence of an eavesdropper. Specifically, we consider the scenario that a source node transmits messages to a destination with the help of multiple cooperative relays, where a relay might be compromised to become an eavesdropper as an inside attacker. Our joint relaying and jamming approach is to assign some relay nodes to act as jammers to interfere the eavesdropper, while the remaining ones continue relaying information to the destination. We propose a protocol to implement the joint cooperative relaying and jamming. Our protocol further considers the particular challenge brought by the inside attacker: it may know the jamming signal and can use it to remove the interference from the jammers. The issue of phase and frequency synchronization in the distributed beamforming is also taken into account. A mixed integer programming problem is formulated to maximize the secrecy rate with the proposed joint relaying and jamming, by which the optimal role assignment to a relay and the associated optimal power assignment can be solved. Numerical results are presented to demonstrate the efficiency of the proposed joint relaying and jamming in improving the secrecy rate, with comparison to existing approaches.
In this paper, the security of two-phase relaying system with multiple intermediate nodes in the presence of a malicious eavesdropper is investigated. To enhance the secrecy, a joint cooperative beamforming and jamming combined with relay and jammer selection is proposed. First, the source broadcasts its signal to the relays that are located close to source in a cluster, i.e., the source node uses a small amount of power to broadcast its message locally to other nodes of the cluster, while destination and the eavesdropper are located outside this cluster. In the second phase, two relays transmit re-encoded signal with optimal beamforming such that the secrecy rate is maximized. Simultaneously, two other intermediate nodes (which act as friendly jammers) transmit random jamming signals to degrade the eavesdropper’s channel. Our goal in this paper is to maximize the secrecy rate by applying different methods such as cooperative beamforming, cooperative jamming and relay and jammer selection. To avoid operational complexity, we consider the minimum number of intermediate nodes needed for relaying and jamming without losing the performance, i.e., achieving a non-zero secrecy rate. Cooperative beamforming with multiple relays demands high amount of information exchange and therefore increases the operational complexity. Thus, we aim to reduce the number of relays which take part in cooperative beamforming. Limiting the number of relays may have a bad effect on the coding gain which we compensate it with a proposed selection gain scheme. Numerical results demonstrate the advantage of our proposed scheme compared to the scheme with no cooperative jamming. The main contribution of this work is combining cooperative beamforming and jamming with relay and jammer selection to enhance the physical layer security.