Suspicious Communication Research Articles

Proactive Eavesdropping of Jamming-Assisted Suspicious Communications in Fading Channels: A Stackelberg Game Approach

Proactive Eavesdropping of Jamming-Assisted Suspicious Communications in Fading Channels: A Stackelberg Game Approach

Sensing Assisted Integrated Communication and Jamming Systems With RSMA for Dynamic Suspicious Communications

Sensing Assisted Integrated Communication and Jamming Systems With RSMA for Dynamic Suspicious Communications

UAV-Assisted Maritime Legitimate Surveillance: Joint Trajectory Design and Power Allocation

This paper investigates a novel maritime wireless surveillance scenario, where a legitimate monitor vessel moves around to eavesdrop the suspicious communication from a suspicious unmanned aerial vehicle (UAV) to a suspicious vessel with the help of a cooperative UAV. Specifically, the cooperative UAV can adjust its jamming power and trajectory to exactly control the transmission rate of the suspicious link, thus improving the monitor vessel's surveillance performance. Furthermore, since the cooperative UAV cannot land or replenish energy on the sea surface, its jamming power allocation on the ocean should be carefully designed by the energy thresholds. Under such setup, we formulate a sum eavesdropping rate maximization problem, which jointly optimizes the jamming power and three-dimensional (3D) trajectory of the cooperative UAV, as well as the two-dimensional (2D) trajectory of the monitor vessel. To address this non-convex optimization problem, we decompose the design problem into three subproblems and propose an iterative algorithm to find its suboptimal solution. Numerical results show that the proposed jamming-assisted 3D joint design can significantly improve the eavesdropping rate and save the jamming power compared to the benchmark schemes.

Unsuspicious User Enabled Proactive Eavesdropping in Interference Networks Using Improper Gaussian Signaling

Proactive eavesdropping is an effective approach to improve the performance of wireless information surveillance, where suspicious users are legitimately eavesdropped by authorized monitors. For the situation when no monitor is available, we propose to authorize unsuspicious users to surveil suspicious users provided that the quality-of-service (QoS) of unsuspicious users is guaranteed. This paper considers an interference network consisting of a suspicious-transmitter (STx)/suspicious-receiver (SRx) pair and an unsuspicious-transmitter (UTx)/unsuspicious-receiver (URx) pair. We assume that URx acts as a monitor to eavesdrop the suspicious communication, and UTx adopts improper Gaussian signaling (IGS) for flexibly managing the interference to SRx. The QoS of the unsuspicious communication is guaranteed by enforcing its outage performance to be higher than a desirable level. The problem of optimizing the transmit power and the IGS circularity coefficient of UTx to maximize the average eavesdropping rate is optimally solved by the Lagrange duality method. Theoretical results show that IGS is effective when the eavesdropping is successful and the unsuspicious communication is in non-outage status. Simulation results confirm that the proposed design works well even when no additional outage of the unsuspicious communication is allowed, and show that IGS can greatly outperform proper Gaussian signaling in most cases.

Proactive Eavesdropping Over Multiple Suspicious Communication Links With Heterogeneous Services

To legitimately eavesdrop communications of suspicious users such as criminals, proactive eavesdropping has been proposed as an effective approach. Current works considered that suspicious communication links (SCLs) carry homogeneous services, which is unrealistic due to randomness of user behaviors. Thus, this paper investigates proactive eavesdropping over multiple SCLs with heterogeneous services. The relative eavesdropping non-outage probability and the relative eavesdropping rate are adopted as eavesdropping utilities for delay-sensitive (DS) and delay-tolerant (DT) suspicious services, respectively. The jamming power allocation problem to maximize the weighted sum eavesdropping utility under the average transmit power constraint at the monitor is investigated under the non-adaptive fixed power allocation and the adaptive power allocation schemes adopted by the SCLs. The problem belongs to sum-of-ratios optimization and is transformed to an equivalent parameterized subtractive-form with some extra auxiliary variables. Two nested optimizations are proposed to solve the equivalent problem based on the Lagrange duality method and the damped Newton method. Simulation results demonstrate the superiority of the proposed algorithms compared to various benchmark algorithms in existing literature. It is shown that the impacts of the power allocation schemes of the SCLs on the eavesdropping performance may be different for the DS and DT suspicious services under different system setups.

Proactive Eavesdropping Strategies Using Hybrid Reflecting-Backscatter Intelligent Surface

This correspondence proposes to employ a hybrid reflecting-backscatter intelligent surface for proactive eavesdropping in a wireless information surveillance system. To be specific, some elements of intelligent reflecting surface (IRS) are used to reflect the incoming signal from the source, while the remaining recast the signal to artificial noise through backscatter techniques. To maximize the effective proactive eavesdropping rate, which is defined as the suspicious communication rate that satisfies the condition of successful eavesdropping, three strategies are presented, including <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Enhancing-Strategy</i> , <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Jamming-Strategy</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Hybrid-Strategy</i> . For the first two, a semidefinite relaxation based algorithm is adopted to design the passive beamforming at IRS. For the last strategy, closed-form expressions of optimal solutions are derived. In addition to the passive beamforming design, the deployment of IRS is optimized by a simulated annealing algorithm. Finally, simulations verify the effectiveness of the proposed schemes.

Luring the Enemy in Deep: Jamming-Assisted Legitimate Eavesdropping Over HARQ-Based Suspicious Communications

This paper investigates the wireless surveillance with a legitimate monitor (E) over hybrid automatic repeat request (HARQ) based suspicious communications between a suspicious transmitter (S) and a suspicious destination (D). Specifically, with the HARQ protocol, S uses at most <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$L \ge 2$</tex-math></inline-formula> transmission rounds (TRs) for delivering the same message to D. Under this setup, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E deliberately jams D at each TR to decrease its signal receiving quality, so as to induce S to consume more TRs for transmitting its message. Then, as a reward, E at these TRs can overhear the suspicious message from S more clearly</i> . Our purpose is to maximize E's eavesdropping success probability, by allocating its jamming power at these <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$L$</tex-math></inline-formula> TRs, subject to its power budget constraint. The problem is highly non-convex. To solve it, we first exploit the general successive convex approximation (SCA) approach to determine the iterative solution. Considering the large complexity of the SCA-based approach, we further develop an easy-to-implement Lagrange multiplier method to find the sub-optimal solution. Numerical results show that the proposed schemes increase the eavesdropping success probability as compared with several benchmarks.

Design and Performance Analysis of Wireless Legitimate Surveillance Systems With Radar Function

Integrated sensing and communication (ISAC) has recently been considered as a promising approach to save spectrum resources and reduce hardware cost. Meanwhile, as information security becomes increasingly more critical issue, government agencies urgently need to legitimately monitor suspicious communications via proactive eavesdropping. Thus, in this paper, we investigate a wireless legitimate surveillance system with radar function. We seek to jointly optimize the receive and transmit beamforming vectors to maximize the eavesdropping success probability which is transformed into the difference of signal-to-interference-plus-noise ratios (SINRs) subject to the performance requirements of radar and surveillance. The formulated problem is challenging to solve. By employing the Rayleigh quotient and fully exploiting the structure of the problem, we apply the divide-and-conquer principle to divide the formulated problem into two subproblems for two different cases. For the first case, we aim at minimizing the total transmit power, and for the second case we focus on maximizing the jamming power. For both subproblems, with the aid of orthogonal decomposition, we obtain the optimal solution of the receive and transmit beamforming vectors in closed-form. Performance analysis and discussion of some insightful results are also carried out. Finally, extensive simulation results demonstrate the effectiveness of our proposed algorithm in terms of eavesdropping success probability.

Maxmin Fairness for UAV-Enabled Proactive Eavesdropping With Jamming Over Distributed Transmit Beamforming-Based Suspicious Communications

Unmanned aerial vehicle (UAV) plays an important role in wireless communication systems, due to the additional degree of freedom realized from its flexible deployment. Driven by this advantage and considering the security issue, this paper aims to investigate UAV-enabled proactive eavesdropping over distributed transmit beamforming-based suspicious communications. Specifically, for the suspicious system, there are multiple suspicious clusters aiming to communicate with the suspicious destination (D) using mutually orthogonal frequency bands, and distributed transmit beamforming is exploited by each cluster to strengthen the signal receiving quality at D. For the legitimate party, the full-duplex UAV exploits one antenna to jam D and uses the other antenna to overhear the signals of the suspicious clusters concurrently. By resorting to the Laguerre series approximation and the central limit theorem, we first characterize, in closed form, the approximated distributions of the receiving signal-to-interference-noise ratio (SINR) at D and the UAV, which are shown to be very tight. Based on this analysis and considering that the suspicious system works in the delay-limited transmission mode or the delay-sensitive transmission mode, we aim to maximize the minimum eavesdropping success probability of the UAV for those suspicious communications links, by jointly adjusting the UAV’s deployment and jamming power allocations over different frequency bands. The problem is highly non-convex. To tackle this, we develop an alternative optimization framework and further a novel and low-complexity solution in the high SNR regime to the optimization problem. Simulation results show the effectiveness of our proposed schemes compared to competitive benchmarks.

Proactive Eavesdropping of Physical Layer Security Aided Suspicious Communications in Fading Channels

Proactive eavesdropping is an effective approach to legitimately surveil the suspicious communications. Current studies all considered that physical layer security (PLS) techniques such as the wiretap coding are not applied by the suspicious users (SUs) to protect their communications. Contrary to that, we consider that the wiretap coding in PLS is adopted by the SUs to defend against the proactive eavesdropping from the legitimate monitor over fading channels. Under the fixed power allocation (FPA) and the water-filling power allocation (WFPA) at the SUs, the problem of jamming power allocation at the monitor to maximize the relative eavesdropping rate under the average transmit power constraint is investigated. The optimization problem is solved by two nested optimizations, where the bisection search method is used in the outer optimization, and the Lagrange duality method and the successive convex approximation method are used in the inner optimization. Simulation results confirm the effectiveness of the proposed algorithms compared to various baseline algorithms. It is shown that the proposed algorithm under the WFPA at the SUs outperforms the one under the FPA at the SUs, and the monitor achieves lower relative eavesdropping rate when the SUs adopt a stricter secure transmission scheme.

Proactive Eavesdropping With Adaptive Full-Duplex Jamming-Helping Method for Infrastructure-Free Relay Networks

With the emergence of advanced communication technologies such as infrastructure-free communication networks, the need for proactive eavesdropping which can constantly monitor and intervene in the communication network is growing. In response to those demands, we study proactive eavesdropping in the general infrastructure-free communication scenario where the legitimate eavesdropper has to monitor a suspicious communication link without the aid of other nodes. Particularly, to enhance proactive eavesdropping performances, we propose the adaptive full-duplex jamming-helping method in which the legitimate eavesdropper selects the best operating mode adaptively depending on the channel conditions unlike conventional studies where the behavior of the monitor node was predetermined. Moreover, we design the optimal power scheme for the proposed method to maximize the eavesdropping rate while minimizing total power consumption of the legitimate eavesdropper simultaneously. In the process, we classify the channel conditions into several mutual exclusive cases to simplify the optimization problem, and present the optimal solution in closed form for each case. Finally, it is verified through simulation results that the proposed method is superior in terms of both the eavesdropping rate and the outage probability than other benchmark methods.

A Proactive Eavesdropping Game in MIMO Systems Based on Multiagent Deep Reinforcement Learning

This paper considers an adversarial scenario between a legitimate eavesdropper and a suspicious communication pair. All three nodes are equipped with multiple antennas. The eavesdropper, which operates in a full-duplex model, aims to wiretap the dubious communication pair via proactive jamming. On the other hand, the suspicious transmitter, which can send artificial noise (AN) to disturb the wiretap channel, aims to guarantee secrecy. More specifically, the eavesdropper adjusts jamming power to enhance the wiretap rate, while the suspicious transmitter jointly adapts the transmit power and noise power against the eavesdropping. Considering the partial observation and complicated interactions between the eavesdropper and the suspicious pair in unknown system dynamics, we model the problem as an imperfect-information stochastic game. To approach the Nash equilibrium solution of the eavesdropping game, we develop a multi-agent reinforcement learning (MARL) algorithm, termed neural fictitious self-play with soft actor-critic (NFSP-SAC), by combining the fictitious self-play (FSP) with a deep reinforcement learning algorithm, SAC. The introduction of SAC enables FSP to handle the problems with continuous and high dimension observation and action space. The simulation results demonstrate that the power allocation policies learned by our method empirically converge to a Nash equilibrium, while the compared reinforcement learning algorithms suffer from severe fluctuations during the learning process.

Proactive Eavesdropping via Jamming Over Short Packet Suspicious Communications With Finite Blocklength

Short packet communications play key roles in the Internet-of-Things. Conventional Shannon’s coding theorem is not applicable for short packet communications, and the achievable rate in the finite blocklength regime is related to the blocklength and the decoding error probability. Contrary to conventional physical layer security, wireless information surveillance assumes that the communication users are suspicious users and the eavesdroppers are legitimate monitors, and proactive eavesdropping via jamming has been proposed to improve the eavesdropping performance. Existing works on proactive eavesdropping ignored the scenario when the suspicious users adopt the short packet communications. Thus, this paper tries to develop effective proactive eavesdropping schemes suitable for the short packet suspicious communications. Under the truncated channel inversion power allocation and the modified constant power allocation policies at the suspicious source, the problems of jamming power allocation for maximizing the monitoring success probability subject to the average transmit power constraint at the monitor are investigated. Based on the Dinkelbach-type algorithm, the Lagrange duality method and a novel tractable approximate expression for the decoding error probability, we derive suboptimal solutions to the problems. Simulation results demonstrate the effectiveness of the proposed solutions compared to various benchmark algorithms in existing literature.

Proactive eavesdropping rate maximization with UAV spoofing relay

Spoofing relay is an effective way for legitimate agencies to monitor suspicious communication links and prevent malicious behaviors. The unmanned aerial vehicles(UAVs)-assisted wireless information surveillance system can virtually improve proactive eavesdropping efficiency thanks to the high maneuverability of UAVs. This paper aims to maximize the eavesdropping rate of the surveillance system where the UAV is exploited to actively eavesdrop by spoofing relay technology. We formulate the problem to jointly optimize the amplification coefficient, splitting ratio, and UAV’s trajectory while considering successful monitoring. To make the nonconvex problem tractable, we decompose the problem into three sub-problems and propose a successive convex approximation based alternate iterative algorithm to quickly obtain the near-optimal solution. The final simulation results show that the UAV as an active eavesdropper can effectively increase the information eavesdropping rate than a passive eavesdropper.

Proactive Eavesdropping for Wireless Information Surveillance Under Suspicious Communication Quality-of-Service Constraint

This paper investigates a proactive eavesdropping scenario where multiple suspicious communication (SC) links are eavesdropped by a full-duplex monitor who can send jamming or constructive signals on each SC link. In order to avoid being discovered by the suspicious users, the monitor restricts the SC quality-of-service (QoS) degradation caused by itself. Under this SC QoS constraint and the average transmit power constraint, the problems of optimizing the mode and transmit power of the monitor to maximize the average successful eavesdropping probability and the average eavesdropping rate are investigated for the delay-sensitive suspicious service and delay-tolerant suspicious service, respectively. By proving that the time-sharing condition is satisfied, the optimal solutions are derived based on the Lagrange duality method. Simulation results validate the effectiveness of the proposed schemes. It is shown that the proposed schemes can provide satisfactory eavesdropping performance improvement even with zero SC QoS degradation requirement.

Proactive Eavesdropping via Opportunistic Energy Transfer and Jamming for Wireless-Powered Suspicious Communication

This paper investigates the information surveillance with a half-duplex legitimate monitor (E) for wireless-powered suspicious communication in Internet of Things networks, which consists of one suspicious power-beacon (PB), <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${N}$ </tex-math></inline-formula> battery-free suspicious transmitters (STs) operating in orthogonal frequency bands (FBs) and one suspicious destination (SD). The suspicious communication includes two phases: in phase 1, the PB chooses one best ST and exhausts its power over the corresponding FB for the energy transfer; in phase 2, by exploiting the harvested energy, such ST uploads its suspicious message to the SD. Under this setup, a novel proactive eavesdropping scheme is proposed to maximize the eavesdropping success probability at E. Specifically, in phase 1, E assists energy transfer in random <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> FBs, to deliberately increase the harvested energy of the corresponding <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> STs; in phase 2, E overhears in the same <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> FBs and jams in the remaining <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${N}\,\,-\,\,{K}$ </tex-math></inline-formula> FBs concurrently, to intentionally improve the interference levels of the SD in those <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${N}\,\,-\,\,{K}$ </tex-math></inline-formula> FBs. We prove that, given <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> , as E’s energy transfer power in phase 1 or jamming power in phase 2 increases: 1) the suspicious system will choose one of those unjammed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> STs for information uploading with a higher probability, thus increasing the conditional probability of E’s eavesdropping and 2) the ratio of the selected ST’s transmit power and communication rate will improve, thus enhancing the decoding success probability of E concurrently. In addition, given E’s transmit power in phases 1 and 2, as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> increases, the conclusion of i) still holds, but the conclusion of ii) reverses. Hence, to maximize the objective, which is the product of the conditional probability of eavesdropping and the decoding success probability, interestingly there exists a fundamental trade-off in deciding both <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> and the power allocations in phases 1 and 2, and a simple search can be exploited to find the optimal solution. Numerical results show the effectiveness of our proposed scheme compared to competitive benchmarks.

Legitimate Surveillance of Suspicious Computation Offloading in Mobile Edge Computing Networks

In this paper, the legitimate surveillance of a suspicious mobile edge computing (MEC) network consisting of a suspicious edge server (SES) and multiple suspicious users (SUs), in the presence of a full-duplex monitor is studied. Each SU has a computation task to complete within a time deadline and can completely or partially offload the task to SES, while the monitor can either jam or assist the suspicious communications during task uploading and result downloading. With the heterogeneous offloading model adopted by the SUs, the problem of optimizing the monitor mode and transmit power to maximize the average ratio of successfully eavesdropped tasks, subject to the monitor transmit power constraint and the task completion time deadline constraint is investigated. The problem is solved via exploring the particular problem structure and adopting the sum-of-ratios optimization. Simulation results show that the proposed algorithm significantly outperforms the benchmark algorithms, especially for the SUs with partial offloading. It is also shown that the proposed algorithm is of low-complexity and achieves almost the same performance as the high-complexity optimal algorithm. Besides, compared to the SUs with binary offloading, the eavesdropping performance for the SUs with partial offloading is shown to be much better.

Comprehensive Survey of Multimedia Steganalysis: Techniques, Evaluations, and Trends in Future Research

During recent years, emerging multimedia processing techniques with information security services have received a lot of attention. Among those trends are steganography and steganalysis. Steganography techniques aim to hide the existence of secret messages in an innocent-looking medium, where the medium before and after embedding looks symmetric. Steganalysis techniques aim to breach steganography techniques and detect the presence of invisible messages. In the modern world, digital multimedia such as audio, images, and video became popular and widespread, which makes them perfect candidates for steganography. Monitoring this huge multimedia while the user communicates with the outside world is very important for detecting whether there is a hidden message in any suspicious communication. However, steganalysis has a significant role in many fields, such as to extract the stego-message, to detect suspicious hidden messages and to evaluate the robustness of existing steganography techniques. This survey provides the general principles of hiding secret messages using digital multimedia as well as reviewing the background of steganalysis. In this survey, the steganalysis is classified based on many points of view for better understanding. In addition, it provides a deep review and summarizes recent steganalysis approaches and techniques for audio, images, and video. Finally, the existing shortcomings and future recommendations in this field are discussed to present a useful resource for future research.

Proactive Eavesdropping With Jamming Power Allocation in Training-Based Suspicious Communications

This letter studies proactive eavesdropping with one legitimate monitor (E) in the classical single-hop suspicious communication. Specifically, unlike all previous works that ignored the suspicious channel training phase and just considered the jamming power optimization of E in the suspicious data transmission phase to facilitate eavesdropping, this letter advances the research by comprehensively investigating the jamming power allocation of E in both phases, with the purpose of maximizing its eavesdropping success probability. Under this setup, we first derive an exact expression of the objective and reveal the existence of a fundamental trade-off in deciding the jamming power allocation, for which a simple one-dimensional search is employed to find the optimal solution. To simplify the analysis, we further derive a tight approximation of the objective and then develop a very fast alternating optimization algorithm to find the sub-optimal jamming power allocation. Moreover, we extend our analysis to the case where the channel state information is available at the suspicious transmitter via channel feedback. Simulation results demonstrate the effectiveness of our proposed scheme compared to competitive benchmarks.

A Rare Case of Broncho-Biliary Fistula Secondary to Carolis Disease with Multiple Cholangitic Abscesses

Bronchobiliary fistula (BBF) is a condition of abnormal intercommunication between biliary tract and bronchial tree. The diagnosis is quite challenging without high degree of suspicion and guidelines on its management are limited. Herein, we describe a case of BBF as a sequelae of Caroli’s disease leading to repeated CBD obstruction with cholangitic abscesses and hepatolithiasis managed successfully with ERCP and stenting. Patient was known case of Caroli’s disease and had undergone ERCP with CBD stenting for obstructive jaundice secondary to CBD calculi. He presented with complaints of fever with chills, cough with expectoration but no abdominal complaints. He was admitted with suspicion of LRTI and was found to have frank bile draining from right middle lobe on bronchoscopy. MRCP showed suspicious communication between a biliary radical in segment IV A of liver and a segmental bronchus of Rt Middle Lobe of lung. Patient underwent ERCP, evidence of multiple cholangitic abscesses along with hepatolithiasis. The contrast was seen flowing into pulmonary tree from the right anterior segment of the liver thereby confirming our diagnosis of BBF. A plastic biliary stent was placed across the hepatobiliary communication. Reports of BBF are far and few over the years. According to data, BBF secondary to tumours (32.3%) is the most common followed by bile duct obstruction (30.8%). To our knowledge, this is second case of patient of Caroli’s disease presenting with BBF. BBF was successfully managed with biliary drainage and patient was relieved of bilioptysis and advised liver transplant.