In covert communications,joint jammer selection and power optimization are important to improve performance.However,existing schemes usually assume a warden with a known location and perfect Channel State Information(...In covert communications,joint jammer selection and power optimization are important to improve performance.However,existing schemes usually assume a warden with a known location and perfect Channel State Information(CSI),which is difficult to achieve in practice.To be more practical,it is important to investigate covert communications against a warden with uncertain locations and imperfect CSI,which makes it difficult for legitimate transceivers to estimate the detection probability of the warden.First,the uncertainty caused by the unknown warden location must be removed,and the Optimal Detection Position(OPTDP)of the warden is derived which can provide the best detection performance(i.e.,the worst case for a covert communication).Then,to further avoid the impractical assumption of perfect CSI,the covert throughput is maximized using only the channel distribution information.Given this OPTDP based worst case for covert communications,the jammer selection,the jamming power,the transmission power,and the transmission rate are jointly optimized to maximize the covert throughput(OPTDP-JP).To solve this coupling problem,a Heuristic algorithm based on Maximum Distance Ratio(H-MAXDR)is proposed to provide a sub-optimal solution.First,according to the analysis of the covert throughput,the node with the maximum distance ratio(i.e.,the ratio of the distances from the jammer to the receiver and that to the warden)is selected as the friendly jammer(MAXDR).Then,the optimal transmission and jamming power can be derived,followed by the optimal transmission rate obtained via the bisection method.In numerical and simulation results,it is shown that although the location of the warden is unknown,by assuming the OPTDP of the warden,the proposed OPTDP-JP can always satisfy the covertness constraint.In addition,with an uncertain warden and imperfect CSI,the covert throughput provided by OPTDP-JP is 80%higher than the existing schemes when the covertness constraint is 0.9,showing the effectiveness of OPTDP-JP.展开更多
Watermarking is embedding visible or invisible data within media to verify its authenticity or protect copyright.The watermark is embedded in significant spatial or frequency features of the media to make it more resi...Watermarking is embedding visible or invisible data within media to verify its authenticity or protect copyright.The watermark is embedded in significant spatial or frequency features of the media to make it more resistant to intentional or unintentional modification.Some of these features are important perceptual features according to the human visual system(HVS),which means that the embedded watermark should be imperceptible in these features.Therefore,both the designers of watermarking algorithms and potential attackers must consider these perceptual features when carrying out their actions.The two roles will be considered in this paper when designing a robust watermarking algorithm against the most harmful attacks,like volumetric scaling,histogram equalization,and non-conventional watermarking attacks like the Denoising Convolution Neural Network(DnCNN),which must be considered in watermarking algorithm design due to its rising role in the state-of-the-art attacks.The DnCNN is initialized and trained using watermarked image samples created by our proposed Covert and Severe Attacks Resistant Watermarking Algorithm(CSRWA)to prove its robustness.For this algorithm to satisfy the robustness and imperceptibility tradeoff,implementing the Dither Modulation(DM)algorithm is boosted by utilizing the Just Noticeable Distortion(JND)principle to get an improved performance in this sense.Sensitivity,luminance,inter and intra-block contrast are used to adjust the JND values.展开更多
The purpose of the covert communication scheme is to conceal the communication behavior entirely.In such schemes,the sender and receiver rely on secret keys to establish a covert channel.However,conventional key excha...The purpose of the covert communication scheme is to conceal the communication behavior entirely.In such schemes,the sender and receiver rely on secret keys to establish a covert channel.However,conventional key exchange protocols would expose the key exchange process between them.An adversary who observes the key exchange would be aware of the existence of communication behavior.The keys used in covert communication are not suitable to be generated through conventional key exchange schemes.To address this,we propose a blockchain-based covert elliptic-curve Diffie-Hellman key exchange scheme(BCDH)to conceal the process of the key exchange in blockchain transactions.Following a straightforward setup,BCDH allows the sender and receiver to covertly exchange a secret key on a blockchain without direct communication.Furthermore,we expand the BCDH approach to operate across multiple blockchains,further enhancing its covertness and stability.We analyze BCDH from several perspectives,including covertness,security,randomness,etc.Additionally,we implement a prototype of BCDH on the Ethereum platform to assess its feasibility and performance.Our evaluation demonstrates that BCDH is efficient and well-suited for real-world applications.展开更多
This paper investigates the reconfigurable intelligent surface(RIS)-aided MIMO covert communications in high-speed railway(HSR)scenario.In the scenario,RIS controls the phases of reflection elements dynamically to sen...This paper investigates the reconfigurable intelligent surface(RIS)-aided MIMO covert communications in high-speed railway(HSR)scenario.In the scenario,RIS controls the phases of reflection elements dynamically to send the signal in the desired direction,which facilitates the covert communication between base station(BS)and train mobile relay(MR)in the existence of a watchful warden(Willie).To protect the desired transmission,it is assumed that MR sends out jamming signals with a varying power to confuse the Willie.Considering the Doppler spread caused by the time-varying wireless channel,the joint optimization problem of the BS beamforming matrix,MR beamforming matrix,and the RIS phase shifts is established to maximize the covert throughput.An alternating optimization(AO)method for handling non convex problems is proposed based on coupling effects and the constraints of constant modulus,and a semidefinite relaxation method is provided.Finally,we achieve the optimal solutions of the multi-objective optimization problem by interior-point method.The simulation results demonstrate that the proposed algorithm exhibits the superior robustness and covert performances in high-speed railway scenarios.展开更多
Blockchain,as a distributed ledger,inherently possesses tamper-resistant capabilities,creating a natural channel for covert communication.However,the immutable nature of data storage might introduce challenges to comm...Blockchain,as a distributed ledger,inherently possesses tamper-resistant capabilities,creating a natural channel for covert communication.However,the immutable nature of data storage might introduce challenges to communication security.This study introduces a blockchain-based covert communication model utilizing dynamic Base-K encoding.The proposed encoding scheme utilizes the input address sequence to determine K to encode the secret message and determines the order of transactions based on K,thus ensuring effective concealment of the message.The dynamic encoding parameters enhance flexibility and address issues related to identical transaction amounts for the same secret message.Experimental results demonstrate that the proposed method maintains smooth communication and low susceptibility to tampering,achieving commendable concealment and embedding rates.展开更多
The emerging deployment of large-scale Low Earth Orbit(LEO)satellite constellations provides seamless global coverage.However,the increasing number of satellites also introduces significant security challenges,such as...The emerging deployment of large-scale Low Earth Orbit(LEO)satellite constellations provides seamless global coverage.However,the increasing number of satellites also introduces significant security challenges,such as eavesdropping and illegal communication behavior detection.This paper investigates covert wireless communication over uplink satellite-terrestrial network,focusing on scenarios with warden satellites.By accounting for shot noise generated by ambient signals from terrestrial interferers,the terrestrial transmitter Alice can effectively hide its signal from warden satellites.Leveraging stochastic geometry,the distributions of distances between transmitter and satellites are analyzed,enabling the assessment of uplink performance and interference within a satellite’s coverage area.Approximate expressions for detection error probability and transmission outage probability are derived.Based on the theoretical analysis,an optimal scheme is proposed to maximize covert throughput under the constraint of the average detection error probability of the most detrimental warden satellite.Extensive Monte Carlo simulations experiments are conducted to validate the accuracy of analytical methods for evaluating covert performance.展开更多
Unmanned aerial vehicles(UAVs),characterized by their low cost and operational flexibility,have been increasingly deployed across civilian,military,and commercial applications.To improve the coverage and connectivity,...Unmanned aerial vehicles(UAVs),characterized by their low cost and operational flexibility,have been increasingly deployed across civilian,military,and commercial applications.To improve the coverage and connectivity,UAVs can be utilized to realize the comprehensive spatial coverage for the sixth-generation mobile networks.However,the private data in UAV networks is easy to be exposed due to the light-of-sight links and openness of wireless transmission.Covert communication as an emerging technique has shown its superiority in hiding the transmission behavior,which can further enhance the security of UAV networks compared with the traditional physical-layer security.Therefore,in this article,we present a survey on the recent advanced research about covert UAV communications.First,the roles of UAVs for covert communications are described.Then,the covert UAV communications with different uncertainties are introduced.Moreover,the wireless techniques for covert UAV communications are explored.In addition,we point out the applications in covert UAV communications.Finally,the open research issues concerning practical scenarios and promising applications are highlighted.展开更多
With the widespread application of com-munication technology in the non-terrestrial network(NTN),the issue of the insecure communication due to the inherent openness of the NTN is increasingly being recognized.Consequ...With the widespread application of com-munication technology in the non-terrestrial network(NTN),the issue of the insecure communication due to the inherent openness of the NTN is increasingly being recognized.Consequently,safeguarding com-munication information in the NTN has emerged as a critical challenge.To address this issue,we pro-pose a beamforming and horizontal trajectory joint op-timization method for unmanned aerial vehicle(UAV)covert communications in the NTN.First,we formu-late an optimization problem that considers constraints such as the transmitting power and the distance.More-over,we employ the integrated communication and jamming(ICAJ)signal as Alice’s transmitting signal,further protecting the content of communication in-formation.Next,we construct two subproblems,and we propose an alternate optimization(AO)algorithm based on quadratic transform and penalty term method to solve the proposed two subproblems.Simulation re-sults demonstrate that the proposed method is effective and has better performance than benchmarks.展开更多
In this work,we consider an Unmanned Aerial Vehicle(UAV)aided covert edge computing architecture,where multiple sensors are scattered with a certain distance on the ground.The sensor can implement several computation ...In this work,we consider an Unmanned Aerial Vehicle(UAV)aided covert edge computing architecture,where multiple sensors are scattered with a certain distance on the ground.The sensor can implement several computation tasks.In an emergency scenario,the computational capabilities of sensors are often limited,as seen in vehicular networks or Internet of Things(IoT)networks.The UAV can be utilized to undertake parts of the computation tasks,i.e.,edge computing.While various studies have advanced the performance of UAV-based edge computing systems,the security of wireless transmission in future 6G networks is becoming increasingly crucial due to its inherent broadcast nature,yet it has not received adequate attention.In this paper,we improve the covert performance in a UAV aided edge computing system.Parts of the computation tasks of multiple ground sensors are offloaded to the UAV,where the sensors offload the computing tasks to the UAV,and Willie around detects the transmissions.The transmit power of sensors,the offloading proportions of sensors and the hovering height of the UAV affect the system covert performance,we propose a deep reinforcement learning framework to jointly optimize them.The proposed algorithm minimizes the system average task processing delay while guaranteeing that the transmissions of sensors are not detected by the Willie under the covertness constraint.Extensive simulations are conducted to verify the effectiveness of the proposed algorithm to decrease the average task processing delay with comparison with other algorithms.展开更多
In this work,we consider an Unmanned Aerial Vehicle(UAV)-aided covert transmission network,which adopts the uplink transmission of Communication Nodes(CNs)as a cover to facilitate covert transmission to a Primary Comm...In this work,we consider an Unmanned Aerial Vehicle(UAV)-aided covert transmission network,which adopts the uplink transmission of Communication Nodes(CNs)as a cover to facilitate covert transmission to a Primary Communication Node(PCN).Specifically,all nodes transmit to the UAV exploiting uplink non-Orthogonal Multiple Access(NOMA),while the UAV performs covert transmission to the PCN at the same frequency.To minimize the average age of covert information,we formulate a joint optimization problem of UAV trajectory and power allocation designing subject to multi-dimensional constraints including covertness demand,communication quality requirement,maximum flying speed,and the maximum available resources.To address this problem,we embed Signomial Programming(SP)into Deep Reinforcement Learning(DRL)and propose a DRL framework capable of handling the constrained Markov decision processes,named SP embedded Soft Actor-Critic(SSAC).By adopting SSAC,we achieve the joint optimization of UAV trajectory and power allocation.Our simulations show the optimized UAV trajectory and verify the superiority of SSAC compared with various existing baseline schemes.The results of this study suggest that by maintaining appropriate distances from both the PCN and CNs,one can effectively enhance the performance of covert communication by reducing the detection probability of the CNs.展开更多
In this paper,we investigate covert communications under multi-antenna detection,and explore the impacts of the warden’s channel state information(CSI)availability and the noise uncertainty on system covert capabilit...In this paper,we investigate covert communications under multi-antenna detection,and explore the impacts of the warden’s channel state information(CSI)availability and the noise uncertainty on system covert capability.The detection performance at warden is analyzed in two cases under the perfect and statistical CSI at warden,respectively.In particular,for the former one,the warden utilizes the likelihood ratio(LR)detector,while for the latter one,the generalized likelihood ratio(GLR)detector is adopted.We first consider the scenario where the blocklength is finite,and demonstrate that the covert rate under both cases asymptotically goes to zero as the blocklength goes to infinity.Subsequently,we take the noise uncertainty at the warden into account which leads to positive covert rate,and characterize the covert rate for infinite blocklength.Specially,we derive the optimal transmit power for the legitimate transmitter that maximizes the covert rate.Besides,the rate gap under two cases,with different CSI availability at the warden,can be presented in closed form.Finally,numerical results validate the effectiveness of our theoretical analysis and also demonstrate the impacts of the factors studied on the system covertness.展开更多
The access of massive Internet of Things(IoT)users poses several challenges for Unmanned Aerial Vehicle(UAV)-aided communications,particularly in terms of security and reliability.This paper investigates a secure and ...The access of massive Internet of Things(IoT)users poses several challenges for Unmanned Aerial Vehicle(UAV)-aided communications,particularly in terms of security and reliability.This paper investigates a secure and robust power allocation scheme for UAV-aided IoT Non-Orthogonal Multiple Access(NOMA)downlink networks with a potential eavesdropper,considering imperfect Channel State Information(CSI).Given the noise uncertainty caused by the UAV’s mobility and the statistical channel estimation error,we formulate a robust optimization problem to maximize the total covert rate of all NOMA users,subject to covertness and rate-based reliability constraints.To solve this optimization problem,we first derive the minimum detection error rate and utilize the statistical characteristics(i.e.,the mean and variance of channel gain errors)to obtain the deterministic covertness and reliability constraints,respectively.We then prove that the problem is concave and determine the optimal power allocation algorithm using the Karush–Kuhn–Tucker conditions.Extensive numerical simulations validate the effectiveness of the proposed algorithm and demonstrate its ability to realize more secure and robust UAV-aided IoT systems.展开更多
Covert communication guarantees the security of wireless communications via hiding the existence of the transmission.This paper focuses on the first and second order asymptotics of covert communication in the AWGN cha...Covert communication guarantees the security of wireless communications via hiding the existence of the transmission.This paper focuses on the first and second order asymptotics of covert communication in the AWGN channels.The covertness is measured by the total variation distance between the channel output distributions induced with and without the transmission.We provide the exact expressions of the maximum amount of information that can be transmitted with the maximum error probability and the total variation less than any small numbers.The energy detection and the random coding are employed to prove our results.We further compare our results with those under relative entropy.The results show how many additional amounts of information can be transmitted covertly when changing the covertness constraint to total variation.展开更多
With the future substantial increase in coverage and network heterogeneity,emerging networks will encounter unprecedented security threats.Covert communication is considered a potential enhanced security and privacy s...With the future substantial increase in coverage and network heterogeneity,emerging networks will encounter unprecedented security threats.Covert communication is considered a potential enhanced security and privacy solution for safeguarding future wireless networks,as it can enable monitors to detect the transmitter's transmission behavior with a low probability,thereby ensuring the secure transmission of private information.Due to its favorable security,it is foreseeable that covert communication will be widely used in various wireless communication settings such as medical,financial,and military scenarios.However,existing covert communication methods still present many challenges toward practical applications.In particular,it is difficult to guarantee the effectiveness of covert schemes based on the randomness of eavesdropping environments,and it is challenging for legitimate users to detect weak covert signals.Considering that emerging artificial-intelligence-aided transmission technologies can open up entirely new opportunities to address the above challenges,we provide a comprehensive review of recent advances and potential research directions in the field of intelligent covert communications in this work.First,the basic concepts and performance metrics of covert communications are introduced.Then,existing effective covert communication techniques in the time,frequency,spatial,power,and modulation domains are reviewed.Finally,this paper discusses potential implementations and challenges for intelligent covert communications in future networks.展开更多
The increasing importance of terminal privacy in the Unmanned Aerial Vehicle(UAV)network has led to a growing recognition of the crucial role of authentication technology in UAV network security.However,traditional au...The increasing importance of terminal privacy in the Unmanned Aerial Vehicle(UAV)network has led to a growing recognition of the crucial role of authentication technology in UAV network security.However,traditional authentication approaches are vulnerable due to the transmission of identity information between UAVs and cryptographic paradigm management centers over a public channel.These vulnerabilities include brute-force attacks,single point of failure,and information leakage.Blockchain,as a decentralized distributed ledger with blockchain storage,tamper-proof,secure,and trustworthy features,can solve problems such as single-point-of-failure and trust issues,while the hidden communication in the physical layer can effectively resist information leakage and violent attacks.In this paper,we propose a lightweight UAV network authentication mechanism that leverages blockchain and covert communication,where the identity information is transmitted as covert tags carried by normal modulated signals.In addition,a weight-based Practical Byzantine Fault-Tolerant(wPBFT)consensus protocol is devised,where the weights are determined by the channel states of UAVs and the outcomes of past authentication scenarios.Simulation results demonstrate that the proposed mechanism outperforms traditional benchmarks in terms of security and robustness,particularly under conditions of low Signal-to-Noise Ratio(SNR)and short tag length.展开更多
Dear Editor,Industrial Internet of things(IIoT) is a typical application of cyberphysical system(CPS). In the IIoT, wireless communication is an inevitable trend to replace the deployment-limited wired transmission fo...Dear Editor,Industrial Internet of things(IIoT) is a typical application of cyberphysical system(CPS). In the IIoT, wireless communication is an inevitable trend to replace the deployment-limited wired transmission for cases with large-scale and mobile devices. However, wireless communication gives rise to critical issues related to physical security, such as malicious detections and attacks [1].展开更多
Due to the characteristics of line-of-sight(LoS)communication in unmanned aerial vehicle(UAV)networks,these systems are highly susceptible to eavesdropping and surveillance.To effectively address the security concerns...Due to the characteristics of line-of-sight(LoS)communication in unmanned aerial vehicle(UAV)networks,these systems are highly susceptible to eavesdropping and surveillance.To effectively address the security concerns in UAV communication,covert communication methods have been adopted.This paper explores the joint optimization problem of trajectory and transmission power in a multi-hop UAV relay covert communication system.Considering the communication covertness,power constraints,and trajectory limitations,an algorithm based on multi-agent proximal policy optimization(MAPPO),named covert-MAPPO(C-MAPPO),is proposed.The proposed method leverages the strengths of both optimization algorithms and reinforcement learning to analyze and make joint decisions on the transmission power and flight trajectory strategies for UAVs to achieve cooperation.Simulation results demonstrate that the proposed method can maximize the system throughput while satisfying covertness constraints,and it outperforms benchmark algorithms in terms of system throughput and reward convergence speed.展开更多
Due to the high flexibility of Unmanned Aerial Vehicles(UAVs),equipping Mobile Edge Computing(MEC)servers on UAVs can effectively and rapidly handle the high computing requirements of computation-intensive tasks.Howev...Due to the high flexibility of Unmanned Aerial Vehicles(UAVs),equipping Mobile Edge Computing(MEC)servers on UAVs can effectively and rapidly handle the high computing requirements of computation-intensive tasks.However,the Line-of-Sight(LoS)transmission between the UAV and ground users makes the offloading information be easily monitored.Therefore,this paper proposes a covert communication scheme against a flying warden in UAV-assisted MEC system.In the proposed scheme,the UAV server assists ground users in completing the computation of offloading tasks.To reduce the possibility of the flying warden detecting the transmission behavior of ground users to the UAV server,a ground jamming device sends jamming signals to the flying warden.The minimum computing capacity of the system is maximized by jointly optimizing ground users’resources and the UAV server’s trajectory under the constraint of system covertness.Due to the multivariable coupling,the optimization problem is non-convex.The optimization problem is first transformed into a tractable form,and then the optimizing solution is iteratively obtained using Successive Convex Approximation(SCA)and Block Coordinate Descent(BCD)algorithms.Numerical results show that,compared to the benchmark schemes,the proposed scheme effectively enhances the computing capacity of the system while meeting the system’s covertness requirements.展开更多
Unmanned Aerial Vehicle(UAV)-aided communication holds great potential to enhance the transmission performance.However,the information security remains a fundamental requirement due to the high possibilities of line-o...Unmanned Aerial Vehicle(UAV)-aided communication holds great potential to enhance the transmission performance.However,the information security remains a fundamental requirement due to the high possibilities of line-of-sight links and the broadcast nature.展开更多
Covert timing channels(CTC)exploit network resources to establish hidden communication pathways,posing signi cant risks to data security and policy compliance.erefore,detecting such hidden and dangerous threats remain...Covert timing channels(CTC)exploit network resources to establish hidden communication pathways,posing signi cant risks to data security and policy compliance.erefore,detecting such hidden and dangerous threats remains one of the security challenges. is paper proposes LinguTimeX,a new framework that combines natural language processing with arti cial intelligence,along with explainable Arti cial Intelligence(AI)not only to detect CTC but also to provide insights into the decision process.LinguTimeX performs multidimensional feature extraction by fusing linguistic attributes with temporal network patterns to identify covert channels precisely.LinguTimeX demonstrates strong e ectiveness in detecting CTC across multiple languages;namely English,Arabic,and Chinese.Speci cally,the LSTM and RNN models achieved F1 scores of 90%on the English dataset,89%on the Arabic dataset,and 88%on the Chinese dataset,showcasing their superior performance and ability to generalize across multiple languages. is highlights their robustness in detecting CTCs within security systems,regardless of the language or cultural context of the data.In contrast,the DeepForest model produced F1-scores ranging from 86%to 87%across the same datasets,further con rming its e ectiveness in CTC detection.Although other algorithms also showed reasonable accuracy,the LSTM and RNN models consistently outperformed them in multilingual settings,suggesting that deep learning models might be better suited for this particular problem.展开更多
基金supported by the CAS Project for Young Scientists in Basic Research under Grant YSBR-035Jiangsu Provincial Key Research and Development Program under Grant BE2021013-2.
文摘In covert communications,joint jammer selection and power optimization are important to improve performance.However,existing schemes usually assume a warden with a known location and perfect Channel State Information(CSI),which is difficult to achieve in practice.To be more practical,it is important to investigate covert communications against a warden with uncertain locations and imperfect CSI,which makes it difficult for legitimate transceivers to estimate the detection probability of the warden.First,the uncertainty caused by the unknown warden location must be removed,and the Optimal Detection Position(OPTDP)of the warden is derived which can provide the best detection performance(i.e.,the worst case for a covert communication).Then,to further avoid the impractical assumption of perfect CSI,the covert throughput is maximized using only the channel distribution information.Given this OPTDP based worst case for covert communications,the jammer selection,the jamming power,the transmission power,and the transmission rate are jointly optimized to maximize the covert throughput(OPTDP-JP).To solve this coupling problem,a Heuristic algorithm based on Maximum Distance Ratio(H-MAXDR)is proposed to provide a sub-optimal solution.First,according to the analysis of the covert throughput,the node with the maximum distance ratio(i.e.,the ratio of the distances from the jammer to the receiver and that to the warden)is selected as the friendly jammer(MAXDR).Then,the optimal transmission and jamming power can be derived,followed by the optimal transmission rate obtained via the bisection method.In numerical and simulation results,it is shown that although the location of the warden is unknown,by assuming the OPTDP of the warden,the proposed OPTDP-JP can always satisfy the covertness constraint.In addition,with an uncertain warden and imperfect CSI,the covert throughput provided by OPTDP-JP is 80%higher than the existing schemes when the covertness constraint is 0.9,showing the effectiveness of OPTDP-JP.
文摘Watermarking is embedding visible or invisible data within media to verify its authenticity or protect copyright.The watermark is embedded in significant spatial or frequency features of the media to make it more resistant to intentional or unintentional modification.Some of these features are important perceptual features according to the human visual system(HVS),which means that the embedded watermark should be imperceptible in these features.Therefore,both the designers of watermarking algorithms and potential attackers must consider these perceptual features when carrying out their actions.The two roles will be considered in this paper when designing a robust watermarking algorithm against the most harmful attacks,like volumetric scaling,histogram equalization,and non-conventional watermarking attacks like the Denoising Convolution Neural Network(DnCNN),which must be considered in watermarking algorithm design due to its rising role in the state-of-the-art attacks.The DnCNN is initialized and trained using watermarked image samples created by our proposed Covert and Severe Attacks Resistant Watermarking Algorithm(CSRWA)to prove its robustness.For this algorithm to satisfy the robustness and imperceptibility tradeoff,implementing the Dither Modulation(DM)algorithm is boosted by utilizing the Just Noticeable Distortion(JND)principle to get an improved performance in this sense.Sensitivity,luminance,inter and intra-block contrast are used to adjust the JND values.
文摘The purpose of the covert communication scheme is to conceal the communication behavior entirely.In such schemes,the sender and receiver rely on secret keys to establish a covert channel.However,conventional key exchange protocols would expose the key exchange process between them.An adversary who observes the key exchange would be aware of the existence of communication behavior.The keys used in covert communication are not suitable to be generated through conventional key exchange schemes.To address this,we propose a blockchain-based covert elliptic-curve Diffie-Hellman key exchange scheme(BCDH)to conceal the process of the key exchange in blockchain transactions.Following a straightforward setup,BCDH allows the sender and receiver to covertly exchange a secret key on a blockchain without direct communication.Furthermore,we expand the BCDH approach to operate across multiple blockchains,further enhancing its covertness and stability.We analyze BCDH from several perspectives,including covertness,security,randomness,etc.Additionally,we implement a prototype of BCDH on the Ethereum platform to assess its feasibility and performance.Our evaluation demonstrates that BCDH is efficient and well-suited for real-world applications.
基金supported by the National Natural Science Foundation of China(62161016)the Key Research and Development Project of Lanzhou Jiaotong University(ZDYF2304)the Beijing Engineering Research Center of High-Speed Railway Broadband Mobile Communications(BHRC-2022-1),Beijing Jiaotong University.
文摘This paper investigates the reconfigurable intelligent surface(RIS)-aided MIMO covert communications in high-speed railway(HSR)scenario.In the scenario,RIS controls the phases of reflection elements dynamically to send the signal in the desired direction,which facilitates the covert communication between base station(BS)and train mobile relay(MR)in the existence of a watchful warden(Willie).To protect the desired transmission,it is assumed that MR sends out jamming signals with a varying power to confuse the Willie.Considering the Doppler spread caused by the time-varying wireless channel,the joint optimization problem of the BS beamforming matrix,MR beamforming matrix,and the RIS phase shifts is established to maximize the covert throughput.An alternating optimization(AO)method for handling non convex problems is proposed based on coupling effects and the constraints of constant modulus,and a semidefinite relaxation method is provided.Finally,we achieve the optimal solutions of the multi-objective optimization problem by interior-point method.The simulation results demonstrate that the proposed algorithm exhibits the superior robustness and covert performances in high-speed railway scenarios.
基金sponsored by the National Natural Science Foundation of China No.U24B201114,6247070859,62302114 and No.62172353Innovation Fund Program of the Engineering Research Center for Integration and Application of Digital Learning Technology of Ministry of Education No.1331007 and No.1311022Natural Science Foundation of Guangdong Province No.2024A1515010177.
文摘Blockchain,as a distributed ledger,inherently possesses tamper-resistant capabilities,creating a natural channel for covert communication.However,the immutable nature of data storage might introduce challenges to communication security.This study introduces a blockchain-based covert communication model utilizing dynamic Base-K encoding.The proposed encoding scheme utilizes the input address sequence to determine K to encode the secret message and determines the order of transactions based on K,thus ensuring effective concealment of the message.The dynamic encoding parameters enhance flexibility and address issues related to identical transaction amounts for the same secret message.Experimental results demonstrate that the proposed method maintains smooth communication and low susceptibility to tampering,achieving commendable concealment and embedding rates.
基金supported in part by the National Natural Science Foundation of China under Grant No.U22B2006.
文摘The emerging deployment of large-scale Low Earth Orbit(LEO)satellite constellations provides seamless global coverage.However,the increasing number of satellites also introduces significant security challenges,such as eavesdropping and illegal communication behavior detection.This paper investigates covert wireless communication over uplink satellite-terrestrial network,focusing on scenarios with warden satellites.By accounting for shot noise generated by ambient signals from terrestrial interferers,the terrestrial transmitter Alice can effectively hide its signal from warden satellites.Leveraging stochastic geometry,the distributions of distances between transmitter and satellites are analyzed,enabling the assessment of uplink performance and interference within a satellite’s coverage area.Approximate expressions for detection error probability and transmission outage probability are derived.Based on the theoretical analysis,an optimal scheme is proposed to maximize covert throughput under the constraint of the average detection error probability of the most detrimental warden satellite.Extensive Monte Carlo simulations experiments are conducted to validate the accuracy of analytical methods for evaluating covert performance.
基金supported by the National Natural Science Foundation of China(Nos.U23A20271 and 62325103).
文摘Unmanned aerial vehicles(UAVs),characterized by their low cost and operational flexibility,have been increasingly deployed across civilian,military,and commercial applications.To improve the coverage and connectivity,UAVs can be utilized to realize the comprehensive spatial coverage for the sixth-generation mobile networks.However,the private data in UAV networks is easy to be exposed due to the light-of-sight links and openness of wireless transmission.Covert communication as an emerging technique has shown its superiority in hiding the transmission behavior,which can further enhance the security of UAV networks compared with the traditional physical-layer security.Therefore,in this article,we present a survey on the recent advanced research about covert UAV communications.First,the roles of UAVs for covert communications are described.Then,the covert UAV communications with different uncertainties are introduced.Moreover,the wireless techniques for covert UAV communications are explored.In addition,we point out the applications in covert UAV communications.Finally,the open research issues concerning practical scenarios and promising applications are highlighted.
基金supported in part by the National Natural Science Foundation of China under Grant U2441250 and 62231027in part by Natural Science Basic Research Programof Shaanxi under Grant 2024JC-JCQN-63+2 种基金in part by InnovationCapability Support Program of Shaanxi under Grant2024RS-CXTD-01in part by New Technology Research University Cooperation Project under Grant SKX242010031in part by the FundamentalResearch Funds for the Central Universities and theInnovation Fund of Xidian University under GrantYJSJ25007.
文摘With the widespread application of com-munication technology in the non-terrestrial network(NTN),the issue of the insecure communication due to the inherent openness of the NTN is increasingly being recognized.Consequently,safeguarding com-munication information in the NTN has emerged as a critical challenge.To address this issue,we pro-pose a beamforming and horizontal trajectory joint op-timization method for unmanned aerial vehicle(UAV)covert communications in the NTN.First,we formu-late an optimization problem that considers constraints such as the transmitting power and the distance.More-over,we employ the integrated communication and jamming(ICAJ)signal as Alice’s transmitting signal,further protecting the content of communication in-formation.Next,we construct two subproblems,and we propose an alternate optimization(AO)algorithm based on quadratic transform and penalty term method to solve the proposed two subproblems.Simulation re-sults demonstrate that the proposed method is effective and has better performance than benchmarks.
基金co-supported by the National Natural Science Foundation of China(No.62271093)the Natural Science Foundation of Chongqing,China(No.CSTB2023NSCQ-LZX0108)the Chongqing Graduate Research Innovation Project,China(No.CYS23093).
文摘In this work,we consider an Unmanned Aerial Vehicle(UAV)aided covert edge computing architecture,where multiple sensors are scattered with a certain distance on the ground.The sensor can implement several computation tasks.In an emergency scenario,the computational capabilities of sensors are often limited,as seen in vehicular networks or Internet of Things(IoT)networks.The UAV can be utilized to undertake parts of the computation tasks,i.e.,edge computing.While various studies have advanced the performance of UAV-based edge computing systems,the security of wireless transmission in future 6G networks is becoming increasingly crucial due to its inherent broadcast nature,yet it has not received adequate attention.In this paper,we improve the covert performance in a UAV aided edge computing system.Parts of the computation tasks of multiple ground sensors are offloaded to the UAV,where the sensors offload the computing tasks to the UAV,and Willie around detects the transmissions.The transmit power of sensors,the offloading proportions of sensors and the hovering height of the UAV affect the system covert performance,we propose a deep reinforcement learning framework to jointly optimize them.The proposed algorithm minimizes the system average task processing delay while guaranteeing that the transmissions of sensors are not detected by the Willie under the covertness constraint.Extensive simulations are conducted to verify the effectiveness of the proposed algorithm to decrease the average task processing delay with comparison with other algorithms.
基金This study was co-supported by the National Natural Science Foundation of China(No.62025110&62271093)the Natural Science Foundation of Chongqing,China(No.CSTB2023NSCQ-LZX0108).
文摘In this work,we consider an Unmanned Aerial Vehicle(UAV)-aided covert transmission network,which adopts the uplink transmission of Communication Nodes(CNs)as a cover to facilitate covert transmission to a Primary Communication Node(PCN).Specifically,all nodes transmit to the UAV exploiting uplink non-Orthogonal Multiple Access(NOMA),while the UAV performs covert transmission to the PCN at the same frequency.To minimize the average age of covert information,we formulate a joint optimization problem of UAV trajectory and power allocation designing subject to multi-dimensional constraints including covertness demand,communication quality requirement,maximum flying speed,and the maximum available resources.To address this problem,we embed Signomial Programming(SP)into Deep Reinforcement Learning(DRL)and propose a DRL framework capable of handling the constrained Markov decision processes,named SP embedded Soft Actor-Critic(SSAC).By adopting SSAC,we achieve the joint optimization of UAV trajectory and power allocation.Our simulations show the optimized UAV trajectory and verify the superiority of SSAC compared with various existing baseline schemes.The results of this study suggest that by maintaining appropriate distances from both the PCN and CNs,one can effectively enhance the performance of covert communication by reducing the detection probability of the CNs.
基金supported in part by the National Natural Science Foundation of China under Grants 62301117,62001094,and U19B2014in part by the National Key Laboratory of Wireless Communications Foundation under Grant 2023KP01602in part by the Natural Science Foundation of Xinjiang Uygur Autonomous Region under Grant 2022D01B184 and 2022D01A297.
文摘In this paper,we investigate covert communications under multi-antenna detection,and explore the impacts of the warden’s channel state information(CSI)availability and the noise uncertainty on system covert capability.The detection performance at warden is analyzed in two cases under the perfect and statistical CSI at warden,respectively.In particular,for the former one,the warden utilizes the likelihood ratio(LR)detector,while for the latter one,the generalized likelihood ratio(GLR)detector is adopted.We first consider the scenario where the blocklength is finite,and demonstrate that the covert rate under both cases asymptotically goes to zero as the blocklength goes to infinity.Subsequently,we take the noise uncertainty at the warden into account which leads to positive covert rate,and characterize the covert rate for infinite blocklength.Specially,we derive the optimal transmit power for the legitimate transmitter that maximizes the covert rate.Besides,the rate gap under two cases,with different CSI availability at the warden,can be presented in closed form.Finally,numerical results validate the effectiveness of our theoretical analysis and also demonstrate the impacts of the factors studied on the system covertness.
基金supported in part by the National Natural Science Foundation of China(No.62403500)in part by the Hubei Provincial Natural Science Foundation,China(No.2023AFB202)+4 种基金in part by the Fundamental Research Funds for the Central Universities,South-Central Minzu University,China(No.CZQ23016)in part by the Chunhui Program of Ministry of Education(No.HZKY20220331)in part by the Research Start-up Funds of South-Central Minzu University,China(Nos.YZZ18006,YZY23001)in part by the Fund for Academic Innovation Teams and Research Platform of South-Central Minzu University,China(Nos.XTZ24003,PTZ24001)in part by the Research Matching Grant Scheme from the Research Grants Council of Hong Kong。
文摘The access of massive Internet of Things(IoT)users poses several challenges for Unmanned Aerial Vehicle(UAV)-aided communications,particularly in terms of security and reliability.This paper investigates a secure and robust power allocation scheme for UAV-aided IoT Non-Orthogonal Multiple Access(NOMA)downlink networks with a potential eavesdropper,considering imperfect Channel State Information(CSI).Given the noise uncertainty caused by the UAV’s mobility and the statistical channel estimation error,we formulate a robust optimization problem to maximize the total covert rate of all NOMA users,subject to covertness and rate-based reliability constraints.To solve this optimization problem,we first derive the minimum detection error rate and utilize the statistical characteristics(i.e.,the mean and variance of channel gain errors)to obtain the deterministic covertness and reliability constraints,respectively.We then prove that the problem is concave and determine the optimal power allocation algorithm using the Karush–Kuhn–Tucker conditions.Extensive numerical simulations validate the effectiveness of the proposed algorithm and demonstrate its ability to realize more secure and robust UAV-aided IoT systems.
基金supported in part by the Natural Science Foundation of Xinjiang Uygur Autonomous Region under Grant 2022D01B184the National Natural Science Foundation of China under Grant 62301117,62131005.
文摘Covert communication guarantees the security of wireless communications via hiding the existence of the transmission.This paper focuses on the first and second order asymptotics of covert communication in the AWGN channels.The covertness is measured by the total variation distance between the channel output distributions induced with and without the transmission.We provide the exact expressions of the maximum amount of information that can be transmitted with the maximum error probability and the total variation less than any small numbers.The energy detection and the random coding are employed to prove our results.We further compare our results with those under relative entropy.The results show how many additional amounts of information can be transmitted covertly when changing the covertness constraint to total variation.
基金supported by the National Natural Science Foundation of China(62425103)the National Key Research and Development Program of China(2022YFC3301300)。
文摘With the future substantial increase in coverage and network heterogeneity,emerging networks will encounter unprecedented security threats.Covert communication is considered a potential enhanced security and privacy solution for safeguarding future wireless networks,as it can enable monitors to detect the transmitter's transmission behavior with a low probability,thereby ensuring the secure transmission of private information.Due to its favorable security,it is foreseeable that covert communication will be widely used in various wireless communication settings such as medical,financial,and military scenarios.However,existing covert communication methods still present many challenges toward practical applications.In particular,it is difficult to guarantee the effectiveness of covert schemes based on the randomness of eavesdropping environments,and it is challenging for legitimate users to detect weak covert signals.Considering that emerging artificial-intelligence-aided transmission technologies can open up entirely new opportunities to address the above challenges,we provide a comprehensive review of recent advances and potential research directions in the field of intelligent covert communications in this work.First,the basic concepts and performance metrics of covert communications are introduced.Then,existing effective covert communication techniques in the time,frequency,spatial,power,and modulation domains are reviewed.Finally,this paper discusses potential implementations and challenges for intelligent covert communications in future networks.
基金supported by the Hainan Province Science and Technology Special Fund,China(No.ZDYF2024GXJS292).
文摘The increasing importance of terminal privacy in the Unmanned Aerial Vehicle(UAV)network has led to a growing recognition of the crucial role of authentication technology in UAV network security.However,traditional authentication approaches are vulnerable due to the transmission of identity information between UAVs and cryptographic paradigm management centers over a public channel.These vulnerabilities include brute-force attacks,single point of failure,and information leakage.Blockchain,as a decentralized distributed ledger with blockchain storage,tamper-proof,secure,and trustworthy features,can solve problems such as single-point-of-failure and trust issues,while the hidden communication in the physical layer can effectively resist information leakage and violent attacks.In this paper,we propose a lightweight UAV network authentication mechanism that leverages blockchain and covert communication,where the identity information is transmitted as covert tags carried by normal modulated signals.In addition,a weight-based Practical Byzantine Fault-Tolerant(wPBFT)consensus protocol is devised,where the weights are determined by the channel states of UAVs and the outcomes of past authentication scenarios.Simulation results demonstrate that the proposed mechanism outperforms traditional benchmarks in terms of security and robustness,particularly under conditions of low Signal-to-Noise Ratio(SNR)and short tag length.
基金partly supported by the National Natural Science Foundation of China(62273298,62273295)Hebei Natural Science Foundation(F2023203063,F2022203025)+1 种基金China Scholarship Council(CSC)(202308130180)Provincial Key Laboratory Performance Subsidy Project(22567612H)
文摘Dear Editor,Industrial Internet of things(IIoT) is a typical application of cyberphysical system(CPS). In the IIoT, wireless communication is an inevitable trend to replace the deployment-limited wired transmission for cases with large-scale and mobile devices. However, wireless communication gives rise to critical issues related to physical security, such as malicious detections and attacks [1].
基金supported by the Natural Science Foundation of Jiangsu Province,China(No.BK20240200)in part by the National Natural Science Foundation of China(Nos.62271501,62071488,62471489 and U22B2002)+1 种基金in part by the Key Technologies R&D Program of Jiangsu,China(Prospective and Key Technologies for Industry)(Nos.BE2023022 and BE2023022-4)in part by the Post-doctoral Fellowship Program of CPSF,China(No.GZB20240996).
文摘Due to the characteristics of line-of-sight(LoS)communication in unmanned aerial vehicle(UAV)networks,these systems are highly susceptible to eavesdropping and surveillance.To effectively address the security concerns in UAV communication,covert communication methods have been adopted.This paper explores the joint optimization problem of trajectory and transmission power in a multi-hop UAV relay covert communication system.Considering the communication covertness,power constraints,and trajectory limitations,an algorithm based on multi-agent proximal policy optimization(MAPPO),named covert-MAPPO(C-MAPPO),is proposed.The proposed method leverages the strengths of both optimization algorithms and reinforcement learning to analyze and make joint decisions on the transmission power and flight trajectory strategies for UAVs to achieve cooperation.Simulation results demonstrate that the proposed method can maximize the system throughput while satisfying covertness constraints,and it outperforms benchmark algorithms in terms of system throughput and reward convergence speed.
基金supported in part by the Zhejiang Provincial Natural Science Foundation of China(No.LR25F010003)in part by the National Natural Science Foundation of China(Nos.62271447,61871348 and 62471090)+1 种基金in part by the Natural Science Foundation of Sichuan Province of China(No.2023NSFSC047)in part by the Fundamental Research Funds for the Provincial Universities of Zhejiang,China(No.RF-C2023008).
文摘Due to the high flexibility of Unmanned Aerial Vehicles(UAVs),equipping Mobile Edge Computing(MEC)servers on UAVs can effectively and rapidly handle the high computing requirements of computation-intensive tasks.However,the Line-of-Sight(LoS)transmission between the UAV and ground users makes the offloading information be easily monitored.Therefore,this paper proposes a covert communication scheme against a flying warden in UAV-assisted MEC system.In the proposed scheme,the UAV server assists ground users in completing the computation of offloading tasks.To reduce the possibility of the flying warden detecting the transmission behavior of ground users to the UAV server,a ground jamming device sends jamming signals to the flying warden.The minimum computing capacity of the system is maximized by jointly optimizing ground users’resources and the UAV server’s trajectory under the constraint of system covertness.Due to the multivariable coupling,the optimization problem is non-convex.The optimization problem is first transformed into a tractable form,and then the optimizing solution is iteratively obtained using Successive Convex Approximation(SCA)and Block Coordinate Descent(BCD)algorithms.Numerical results show that,compared to the benchmark schemes,the proposed scheme effectively enhances the computing capacity of the system while meeting the system’s covertness requirements.
文摘Unmanned Aerial Vehicle(UAV)-aided communication holds great potential to enhance the transmission performance.However,the information security remains a fundamental requirement due to the high possibilities of line-of-sight links and the broadcast nature.
基金This study is financed by the European Union-NextGenerationEU,through the National Recovery and Resilience Plan of the Republic of Bulgaria,Project No.BG-RRP-2.013-0001.
文摘Covert timing channels(CTC)exploit network resources to establish hidden communication pathways,posing signi cant risks to data security and policy compliance.erefore,detecting such hidden and dangerous threats remains one of the security challenges. is paper proposes LinguTimeX,a new framework that combines natural language processing with arti cial intelligence,along with explainable Arti cial Intelligence(AI)not only to detect CTC but also to provide insights into the decision process.LinguTimeX performs multidimensional feature extraction by fusing linguistic attributes with temporal network patterns to identify covert channels precisely.LinguTimeX demonstrates strong e ectiveness in detecting CTC across multiple languages;namely English,Arabic,and Chinese.Speci cally,the LSTM and RNN models achieved F1 scores of 90%on the English dataset,89%on the Arabic dataset,and 88%on the Chinese dataset,showcasing their superior performance and ability to generalize across multiple languages. is highlights their robustness in detecting CTCs within security systems,regardless of the language or cultural context of the data.In contrast,the DeepForest model produced F1-scores ranging from 86%to 87%across the same datasets,further con rming its e ectiveness in CTC detection.Although other algorithms also showed reasonable accuracy,the LSTM and RNN models consistently outperformed them in multilingual settings,suggesting that deep learning models might be better suited for this particular problem.
