Studies On Wireless Covert Channels Based On Constellation Modulation

Wireless communication technology represented by 5G has become the mainstream way for people to access the Internet.However,due to the open nature of transmission media and the development of wireless interception and interception technologies,wireless communications are facing increasing security threats,and their security and privacy protection have become hot topics in the field of information security.As a new wireless security communication technology,the wireless covert channel hides the transmission of secret information in the normal wireless communication process so as not to be discovered by third parties.Compared with other wireless covert channels,wireless covert channels based on constellation modulation use modulation redundancy of general physical layer to embed secret information into a single symbol of normal wireless signals for transmission.This wireless covert channel has a higher transmission rate,and the communication behaviors can be covered in supervised or strong confrontation scenarios to avoid interception and active interference,so it is the most promising type.However,the current design of such covert channel methods still lacks consideration of the resistance of statistical detection tools.At the same time,the reliability of covert communication is susceptible to channel interference and it lacks expansion to common application scenarios.Aiming at the shortcomings of existing research,this dissertation conducts research on wireless covert channel based on constellation modulation from the aspects of improving undetectability,improving reliability,expanding to multiple input multiple output(MIMO)and multicast scenarios.The main research work carried out in this dissertation is as follows:(1)Aiming at the defect in undetectability of current wireless covert channels based on constellation modulation,a wireless covert channel based on constellation shaping modulation is proposed.According to the distribution characteristics of typical wireless channel noise,the secret information is modulated into artificial noise with the distribution similar to channel noise by the mechanisms of distribution matching and model fitting.Then artificial noise is superimposed on normal wireless signal for transmission The simulation results show that compared with the existing wireless covert channels based on constellation modulation,this scheme has a significant improvement in undetectability when the reliability has also been improved.(2)In order to improve the reliability while maintaining the undetectability,based on the central dense and symmetrical distribution characteristics of typical channel noise,from the perspective of adding jitters to randomize the covert channel demodulation boundary,a wireless covert channel based on constellation jittering modulation is proposed.In the modulation process of artificial noise,the jittering parameters shared by the sender and receiver are added to increase the distance between the dense constellation points.To enhance the reliability,analog chaotic codes are used in the modulation process to encode the jittering secret information at the same time.The simulation results show that compared with the constellation shaping modulation method,this scheme can significantly improve the reliability while maintaining the same undetectability.(3)Based on that the components of artificial noise with larger amplitude have stronger reliability while the distribution of artificial noise is kept,a wireless covert channel based on constellation division modulation is proposed.The scheme only modulates the secret information into partial components of the artificial noise,and generates the other components to keep the distribution of whole artificial noise unchanged.At the same time,according to the symmetrical distribution of typical wireless channel noise,the mirror mapping strategies are applied to reduce the influence of carrier signal demodulation errors on the reliability of covert communication.The simulation results show that,compared with the constellation jittering modulation method,the wireless covert channel based on constellation division modulation maintains the same undetectability and significantly improves the reliability under strong channel interference conditions.(4)In order to make the wireless covert channels based on constellation modulation suitable for the common MIMO communication scenarios,MIMO wireless covert channels for static and dynamic channel state information scenarios are proposed,and the correlation of multiple sighals are removed by precoding and channel state information dithering to resist correlation test.The simulation results show that compared with the existing MIMO methods,the two proposed MIMO wireless covert channels can effectively remove the correlation between multiple signals in corresponding scenarios,their undetectability is significantly improved,and the reliability also has a certain improvement.(5)The open characteristics of the wireless covert channel make it naturally suitable for multicast scenarios.The expansion of wireless covert channels to the multicast scenario is analyzed,privacy is used as an additional performance evaluation.Then the multicast wireless covert channels based on orthogonal frequency division multiple access and differential nonorthogonal multiple access are proposed,the former focuses on improving reliability,and the latter focuses on enhancing privacy.The simulation results show that compared to unicast wireless covert channels,the multicast scheme based on orthogonal frequency division multiple access maintains the same undetectability and privacy while further improving reliability,the multicast scheme based on differential non-orthogonal multiple access has a significant improvement in privacy while maintaining the same undetectability and reliability.Finally,the dissertation is summarized,the development trend of wireless covert channel based on constellation modulation is prospected,and the future research direction is pointed out.