With advances in computing and signal processing technologies, wireless communication systems are facing severe security threats, necessitating effective countermeasures. Unlike traditional secure communication schemes, covert communication should hide not only information content but also data transmission activity from adversaries. To this end, we propose an energy dispersion-based covert communication scheme to ensure that communication signal detection by adversaries has close-to-zero probability. The proposed scheme spreads the energy of transmitted signals throughout the whole parameter space to limit the signal detection capability of adversaries and improve the covertness of signal transmission. By defining the covertness of transmitted signals with respect to the adversaries' prior knowledge of parameter spaces, we study the modeling of energy dispersion-based covert communication systems and analyze their fundamental performance limitations. With these analytical results, we further investigate the impacts of adversaries' prior knowledge on the achievable throughput of covert communications. These results demonstrate that the dispersion of signal energy can degrade the performance of coherent signal detection so that the achievable throughput of the covert communication system does not necessarily follow the power-law decrease observed in existing work on the low probability of detection communications. This work lays the theoretical foundation for covert communication based on energy dispersion.
With advances in computing and signal processing technologies, wireless communication systems are facing severe security threats, necessitating effective countermeasures. Unlike traditional secure communication schemes, covert communication should hide not only information content but also data transmission activity from adversaries. To this end, we propose an energy dispersion-based covert communication scheme to ensure that communication signal detection by adversaries has close-to-zero probability. The proposed scheme spreads the energy of transmitted signals throughout the whole parameter space to limit the signal detection capability of adversaries and improve the covertness of signal transmission. By defining the covertness of transmitted signals with respect to the adversaries' prior knowledge of parameter spaces, we study the modeling of energy dispersion-based covert communication systems and analyze their fundamental performance limitations. With these analytical results, we further investigate the impacts of adversaries' prior knowledge on the achievable throughput of covert communications. These results demonstrate that the dispersion of signal energy can degrade the performance of coherent signal detection so that the achievable throughput of the covert communication system does not necessarily follow the power-law decrease observed in existing work on the low probability of detection communications. This work lays the theoretical foundation for covert communication based on energy dispersion.
Wireless systems are of paramount importance for providing ubiquitous data transmission for smart cities. However, due to the broadcasting and openness of wireless channels, such systems face potential security challenges. UAV-assisted covert communication is a supporting technology for improving covert performances and has become a hot issue in the research of wireless communication security. This paper investigates the performance of joint covert and security communication in a tow-hop UAV-assisted wireless system, where a source transmits the covert message to a destination with the help of an untrusted UAV. We first design a transmission scheme such that use UAVs to assist in covert communications while ensuring the security of covert messages. Then, we develop a theoretical model to derive the expressions for the detection error probability of the warden and the covert and security rate, and the maximum covert and security rate is optimized by power control under a given covertness and security requirements. Finally, numerical results are provided to illustrate our theoretical analysis and the performance of covert and security communication in such systems.
Covert communication enhances the security of information transmission by protecting communication behavior, which has been widely investigated in various wireless communication systems. In this paper, we develop a covert Internet of things (IoT) network, where energy-limited IoT nodes selectively transmit information or artificial noise based on channel state information. Specifically, if the channel gains of all legitimate links are less than a given threshold, the energy-limited node emits artificial noise, otherwise, it transmits covert information. Meanwhile, we adopt the strategy of channel inversion power control (CIPC) to hide the location information of the nodes. Then, we derive Willie's detection error probability (DEP), propose an optimization problem for covert throughput, and obtain the optimal threshold and transmission energy. The results indicate that the probability of covert transmission significantly affects Willie's DEP. Moreover, the average covert throughput can be maximized by a relatively small threshold.
Covert wireless communication can prevent an adversary from knowing the existence of user's transmission, thus provide stronger security protection. In AWGN channels, a square root law was obtained and the result shows that Alice can reliably and covertly transmit O(n) bits to Bob in n channel uses in the presence of a passive eavesdropper (Willie). However, existing work presupposes that Willie is static and only samples the channels at a fixed place. If Willie can dynamically adjust the testing distance between him and Alice according to his sampling values, his detection probability of error can be reduced significantly via a trend test. We found that, if Alice has no prior knowledge about Willie, she cannot hide her transmission behavior in the presence of an active Willie, and the square root law does not hold in this situation. We then proposed a novel countermeasure to deal with the active Willie. Through randomized transmission scheduling, Willie cannot detect Alice's transmission attempts if Alice can set her transmission probability below a threshold. Additionally, we systematically evaluated the security properties of covert communications in a dense wireless network, and proposed a density-based routing scheme to deal with multi-hop covert communication in a wireless network. As the network grows denser, Willie's uncertainty increases, and finally resulting in a "shadow" network to Willie.
In this work, we consider a covert communication scenario, where a transmitter Alice communicates to a receiver Bob with the aid of a probabilistic and uninformed jammer against an adversary warden’s detection. The transmission status and power of the jammer are random and follow some priori probabilities. We first analyze the warden’s detection performance as a function of the jammer’s transmission probability, transmit power distribution, and Alice’s transmit power. We then maximize the covert throughput from Alice to Bob subject to a covertness constraint, by designing the covert communication strategies from three different perspectives: Alice’s perspective, the jammer’s perspective, and the global perspective. Our analysis reveals that the minimum jamming power should not always be zero in the probabilistic jamming strategy, which is different from that in the continuous jamming strategy presented in the literature. In addition, we prove that the minimum jamming power should be the same as Alice’s covert transmit power, depending on the covertness and average jamming power constraints. Furthermore, our results show that the probabilistic jamming can outperform the continuous jamming in terms of achieving a higher covert throughput under the same covertness and average jamming power constraints.
Covert communication is the undetected transmission of sensitive information over a communication channel. In wireless communication systems, channel impairments such as signal fading present challenges in the effective implementation and analysis of covert communication systems. This paper generalizes early work in the covert communication field by considering asymptotic results for the number of bits that can be covertly transmitted in n channel uses on a block fading channel. Critical to the investigation is characterizing the performance of optimal detectors at the adversary. Matching achievable and converse results are presented.
Wireless channels are increasingly being used to transmit highly sensitive information in the Internet of Things. However, traditional cryptography methods cannot solve all security problems in IoT systems. Covert wireless communication can prevent an adversary from knowing the existence of a user's transmission; thus, it can provide stronger security protection for IoT devices. In this article, we consider the covert communication in a noisy wireless network, and find that the uncertainty of the aggregated interference experienced by the adversary is beneficial to the potential transmitters. From the network perspective, wireless communications can be hidden in the interference of the noisy wireless network, which the adversary observes as a "shadow" network to a certain extent. Furthermore, we discuss some new results on the effect of active eavesdropper. Square root law becomes invalid, and even jammer-assisted schemes have little effect on the covertness in the presence of active eavesdropper. Finally, we provide a vision for future research.