Untrusted Relay Research Articles

An Optimization Strategy for Security and Reliability in a Diamond Untrusted Relay Network with Cooperative Jamming

An Optimization Strategy for Security and Reliability in a Diamond Untrusted Relay Network with Cooperative Jamming

Secure communication with a multiple-antennas untrusted relay in presence of randomly distributed adversary jammers

In this article, we examine the achievable secrecy rate of a cooperative network including one source, one destination, and one untrusted amplify-and-forward relay, where randomly located adversary jammers attempt to disrupt the wireless communications. The relay has multiple antennas, while the other nodes have a single antenna. The adversary jammers are placed following a Poisson Point Process (PPP) and aim to interfere with the untrusted relay's channel. The relay employs maximal-ratio combining (MRC) to mitigate the jammers' impact and retransmits the signal to the destination using maximum ratio transmission (MRT). To prevent the relay from capturing the message, the destination injects pre-known artificial noise, known as destination-assisted cooperative jamming. We present a closed-form solution for the Ergodic secrecy rate (ESR) of the system with Rayleigh fading channels. An optimization problem for maximizing the secrecy rate is also designed, resulting in a closed-form formula for optimal power allocation (OPA) between the source and destination.

Achievable secrecy rate analysis of OFDM‐based multi‐user untrusted relay networks with imperfect CSI

AbstractThis study investigates the impact of imperfect channel state information (CSI), caused by channel estimation errors and feedback delays, on the physical‐layer security performance of multi‐user relay networks. More specifically, a multi‐user untrusted half/full‐duplex (HD/FD) uni/bi‐directional wireless amplify‐and‐forward (AF) relay network is studied, adopting orthogonal frequency division multiplexing (OFDM). In order to minimize the information leakage, it is considered that a limited number of friendly jammers affect the untrusted relay. In this context, the achievable secrecy rate of the relay network is theoretically analyzed and optimization problems are formulated and solved for the untrusted relay's location and power allocation. Monte Carlo simulations are conducted to validate the theoretical findings, revealing that channel estimation errors cause coding gain losses for low signal‐to noise ratio (SNR) while their impact becomes negligible for high SNR. Also, a large number of user‐pairs achieves higher secrecy rate while FD relaying further improves the secrecy performance. Finally, bi‐directional relaying provides higher achievable secrecy rate over uni‐directional relaying.

A new practical physical layer secret key generation in the presence of an untrusted relay

Physical layer secret key generation (SKG) has recently been introduced as a lightweight and efficient solution for sixth-generation (6G) networks. In this area, schemes based on local random generators are used for high-rate key generation. One of these schemes is random phase injection, where channel probe signals with random phases are exchanged between communication parties (source and destination). This paper proposes an SKG scheme in the presence of an untrusted relay, which helps the SKG process while cannot extract the secret key. To make the scheme operational, for the first time, the channel probe signals are considered discrete random phase based on M-PSK signals and a multi-bit quantizer is used in the reception. In addition, to reduce the key error rate, quantization with guard bands (GB) is used for key extraction. For such a scenario, we derive expressions for key agreement rate, key mismatch rate (KMR), key discarding rate (KDR) and key generation rate (KGR). Additionally, for the first time, this work examines the context of geometric secrecy for the proposed discrete phase key generation scheme for both direct and relaying scenarios. Through simulations, several engineering insights are presented to enhance the quality of the proposed SKG and its security.

Boosting asymmetric measurement-device-independent quantum key distribution via numerical-analysis technology

Asymmetric measurement-device-independent quantum key distribution (MDI-QKD) enables building a scalable, high-rate quantum network with an untrusted relay in real-world scenarios. In this study, we improve the performance of asymmetric MDI-QKD using numerical analysis techniques. Simulation results show a twofold increase in tolerance to basis misalignment compared to the previous state-of-the-art method. Specifically, for instances of substantial basis misalignment, the key rate increases by an order of magnitude, and the maximum communication distance extends by 20 km. Our work significantly enhances the robustness and feasibility of asymmetric MDI-QKD, thereby promoting the widespread deployment of MDI-QKD networks.

Key Exchange for Two-Way Untrusted Relaying Systems Through Constellation Overlapping

Key Exchange for Two-Way Untrusted Relaying Systems Through Constellation Overlapping

Secrecy Performance Analysis of Energy Harvesting Untrusted Relay Networks with Hardware Impairments

In this work, we focus on the issue of secure communication in energy harvesting untrusted relay networks taking into account the impact of hardware impairments, where an energy‐constrained relay, powered by received radio frequency signals, attempts to decode sensitive data from the source without authorization. To achieve secure communication, we employ destination‐assisted jamming to prevent the untrusted relay from decoding sensitive data while serving as a useful energy source. We derive the interception probability (IP), connection outage probability (COP), and effective secrecy throughput (EST) in closed form for time switching relaying (TSR) strategy. Subsequently, we conduct an asymptotic analysis in the high signal‐to‐noise ratio (SNR) regime to provide practical insights into how various system parameters affect security, reliability, and efficiency, including time switching factor and the level of hardware impairments. Our findings demonstrate that the presence of hardware impairments improves security performance but compromises reliability performance, which does more harm than good.

Optimal power allocation for secure transmission in untrusted relay networks with Alamouti space-time block coding

Optimal power allocation for secure transmission in untrusted relay networks with Alamouti space-time block coding

Deep Learning Aided Secure Transmission in Wirelessly Powered Untrusted Relaying in the Face of Hardware Impairments

Deep Learning Aided Secure Transmission in Wirelessly Powered Untrusted Relaying in the Face of Hardware Impairments

Constellation Superposition and Artificial Noise Against Interior and Exterior Eavesdropping in Bidirectional Untrusted Relaying Systems

Constellation Superposition and Artificial Noise Against Interior and Exterior Eavesdropping in Bidirectional Untrusted Relaying Systems

Joint optimization scheme for the reconfigurable intelligent surface-assisted untrusted relay networks

To further improve the secrecy rate, a joint optimization scheme for the reconfigurable intelligent surface (RIS) phase shift and the power allocation is proposed in the untrusted relay (UR) networks assisted by the RIS. The eavesdropping on the UR is interfered by a source-based jamming strategy. Under the constraints of unit modulus and total power, the RIS phase shift, the power allocation between the confidential signal and the jamming signal, and the power allocation between the source node and the UR are jointly optimized to maximize the secrecy rate. The complex multivariable coupling problem is decomposed into three sub-problems, and the non-convexity of the objective function and the constraints is solved with semi-definite relaxation. Simulation results indicate that the secrecy rate is remarkably enhanced with the proposed scheme compared with the equal power allocation scheme, the random phase shift scheme, and the no-RIS scheme.

A Segment-Based Multipath Distribution Method in Partially-Trusted Relay Quantum Networks

As a promising application of quantum information technology, Quantum Key Distribution (QKD) can provide information-theoretically secure key exchange for adjacent communication parties. To achieve long-distance secure communication and scale expansion against inherent channel loss, trusted relays, which are assumed to be absolutely secure, are introduced into QKD networks. However, in practice, trusted relays may be compromised by attacks from ubiquitous eavesdroppers even protected by powerful hardware. Thus, how to ensure the security of end-to-end key distribution in partially-trusted relay QKD networks with the coexistence of trusted relays and untrusted relays becomes a challenging but urgent problem to be solved. To address this critical problem, in this article, we design a segment-based multipath key distribution method. The basic idea of the method is to maximize the security of the end-toend key distribution through the segment-based multipath key distribution. Under the premise of security level requirements, we further propose a flexible key reconstruction scheme to improve the efficiency of key distribution and obtain available secret keys as many as possible. The extensive simulations are conducted and the results reveal that our method significantly outperforms the traditional multipath QKD method in terms of both security and efficiency.

IRS-Aided Secure Communications Over an Untrusted AF Relay System

In this paper, an intelligent reflecting surface (IRS) assisted wireless secure communication system is studied. A multi-antenna access point (AP) intends to send confidential information to a single-antenna user in the presence of an amplify-and-forward (AF) untrusted relay, which may eavesdrop the message when helping relay the signal. It is assumed that the direct link between the AP and the user is blocked by the obstacles. The achievable secrecy rate maximization problem is then formulated. To overcome the non-convexity of the formulated problem, an alternating iteration algorithm is proposed to jointly optimize the active and passive beamforming. Specifically, the transmit beamforming vector at the AP, the phase shift matrix at the IRS, and the relay beamforming matrix are jointly optimized to maximize the secrecy rate. Moreover, the asymptotic expressions for the maximum secrecy rates of the proposed scheme in the high and low transmitted signal-to-noise ratio (SNR) regimes are derived as well. Finally, numerical evaluations demonstrate the superiority of the proposed scheme compared with other benchmark schemes, highlight the importance of properly designed phase shifts at the IRS, and validate the theoretical analysis. It is also demonstrated that the number of antennas at the AP should be strictly larger than the number of antennas at the relay to harvest the benefits of increasing the transmit power at the AP in increasing the secrecy rate.

Cooperative Jamming-Assisted Untrusted Relaying Based on Game Theory for Next-Generation Communication Systems

In this contribution, we investigate the performance of an untrusted relaying system when Cooperative Jammers (CJs) are available. We propose two scenarios, Untrusted Relaying-aided Multiple Cooperative-Jammers-based Simultaneous Transmission (UR-MCJST) and an Untrusted Relaying-aided Multiple Cooperative Jammers-based Time-Division Transmission (UR-MCJTDT). The performances of both UR-MCJST and UR-MCJTDT schemes are investigated. The source node is the primary user (PU) that has access to a transmission bandwidth. An untrusted relay is employed for improving the reliability of the PU transmission, while CJs are invoked for improving the secrecy rate of the PU transmission. The transmission strategy for the scheme proposed in this paper is split into three unique phases. The first phase is called the broadcast-and-jamming phase, while the second phase is called the relaying phase, and the final phase is called CJ’s secondary phase, which is used for transmitting the secondary user message. More explicitly, CJs transmit noise for impairing the untrusted relay node’s ability to decode the message during the broadcast-and-jamming phase. In compensation for their help, CJs are allocated part of the available spectrum by the PU for their transmission during the secondary transmission phase. A Stackelberg leader–follower game was considered between the PU and the CJs, while a power control game that is based on the well-known Nash equilibrium is employed by the CJs. Furthermore, an investigation into the effect of invoking simultaneous transmission and time-division-based transmission scenarios during the CJs’ secondary transmission phase was carried out. Finally, we evaluated the achievable secrecy rate of the PU and the utility rate of the CJs in our proposed scheme.

Optimal Secure Channel Access in Distributed Cooperative Networks With Untrusted Relay

This paper investigates optimal channel access strategies to improve secure communications over a distributed cooperative wireless network with multiple user pairs and an untrusted amplify-and-forward (AF) relay. The user pairs communicate directly or via the relay. To enable secure communication, we formulate a channel access problem to maximize the average secrecy system throughput with destination-based jamming. Using optimal sequential planned decision theory, we propose an optimal channel access strategy where the winning user pair uses direct transmission, cooperative AF relaying, or cooperative jamming in an adaptive manner. We rigorously prove the optimality of the solution and provide a distributed channel access algorithm based on the pure threshold structure, which is easy to implement. Numerical results demonstrate effectiveness and efficiency of the proposed strategy compared to alternatives.

Cost-Optimization-Based Quantum Key Distribution over Quantum Key Pool Optical Networks

The Measurement-Device-Independent-Quantum Key Distribution (MDI-QKD) has the advantage of extending the secure transmission distances. The MDI-QKD combined with the Hybrid-Trusted and Untrusted Relay (HTUR) is used to deploy large-scale QKD networks, which effectively saves deployment cost. We propose an improved scheme for the QKD network architecture and cost analysis, which simplifies the number of QKD transmitters and incorporates the quantum key pool (QKP) in the QKD network. We developed a novel Hybrid-QKD-Network-Cost (HQNC) heuristic algorithm to solve the cost optimization problem. Simulations verified that the scheme in this paper could save the cost by over 50 percent and 90 percent, respectively.

Diamond untrusted relay networks with cooperative jamming: physical layer security perspective

This letter considers a diamond network with two untrusted relays with low-security clearance level. Lossy decoder-and-forward is utilized at both the untrusted relays to enhance the reliability of transmission and to keep the source information confidential to the untrusted relays. The reliable-and-secure probability (RSP), which is the probability that the original messages can be retrieved at the destination while keeping confidential to the relays, is derived. It is found that with the help of cooperative jamming signal, superior reliability and security performance in terms of RSP can be achieved.

Plug‐and‐Play Continuous Variable Measurement‐Device‐Independent Quantum Key Distribution

AbstractIn this paper, a continuous variable (CV) measurement‐device‐independent (MDI) quantum key distribution (QKD) protocol using Gaussian modulated coherent states is proposed. The MDI is first proposed to resist the attacks on the detection equipment by introducing an untrusted relay. However, the necessity of propagation of local oscillator between legitimate users and the relay makes the implementation of CV‐MDI‐QKD highly impractical. By introducing the plug‐and‐play (P&P) technique into CV‐MDI‐QKD, the problems of polarization drifts caused by environmental disturbance and the security loopholes during the local oscillator transmission are solved naturally. The proposed scheme is superior to the previous CV‐MDI‐QKD protocol on the aspect of implementation. The security bounds of the P&P CV‐MDI‐QKD under the Gaussian collective attack are analyzed. It is believed that the technique presented in this paper can be extended to quantum network.

Cooperative Rate Splitting Secure Transmission With an Untrusted User Relay

Combining rate splitting (RS) with cooperative relay, cooperative RS (CRS) can reduce the interference and improve the sum rate of conventional RS networks. However, since the common message can be decoded by both users, how to prevent the untrusted relay from eavesdropping the other user's private message remains a challenge. In this correspondence, we propose a two-slot CRS scheme to guarantee the security of the far legitimate user from the other untrusted relay. The problem is a non-convex joint optimization of the precoding matrix, slot allocation and rate allocation, which is approximated as a convex one. Then, an iterative algorithm is designed to solve the problem. Simulation results show that the proposed scheme can effectively guarantee the security of the far user towards eavesdropping.

Joint Secure Transceiver Design for an Untrusted MIMO Relay Assisted Over-the-Air Computation Networks With Perfect and Imperfect CSI

In this paper, we investigate the physical layer security of an untrusted relay assisted over-the-air computation (AirComp) network, where each node is equipped with multiple antennas and the relay is operated in an amplify-and-forward mode. The relay receives the data from each sensor and sends them to the access point (AP) in the first and second time slot, respectively. The AP applies artificial noise (AN) to protect the aggregation of sensors’ data from being wiretapped by the untrusted relay in the first time slot. In particular, we are interested in minimizing the computation distortion measured by the mean-squared error (MSE) via jointly optimizing beamforming matrices at all nodes, subject to the MSE constraint at the relay and individual power constraints at the AP, the relay and each sensor. In the case of the perfect channel state information (CSI), we convert the nonconvex MSE minimization problem into a difference-of-convex (DC) form and propose a constrained concave-convex procedure that can obtain a local minimum to solve the DC problem. We also generalize the framework to an imperfect CSI case where the additional interference term due to incomplete interference cancellation is considered, and the nonconvex robust MSE minimization problem is solved by a proposed inexact block coordinate descent algorithm. Numerical results are presented to show the effectiveness of our proposed schemes.