In secret key generation of physical layer security technology, it is challenging to achieve high key capacity and low secret key inconsistency rate. This paper investigates intelligent reflecting surface (IRS) assisted secret key generation, which aims to maximize the secret key capacity by adjusting the placement of the IRS units. Specifically, we first analyze and deduce the key capacity expression of the IRS-assisted system from the perspective of information theory. Then we investigate how to use the channel state information (CSI) to place the IRS units effectively so as to maximize the secret key capacity. Simulation results show that our scheme could improve the quality of secret key generation significantly.

Researches on 5th generation mobile communication networks (5G) are emerging to meet the demands of rapidly developing communications applications. The reliability and security of data have become key factors of its development, and thus 5G has put forward higher requirements for new coding and encryption technologies. In this paper, a physical layer encryption algorithm based on polarization codes and chaotic sequences is proposed to improve the reliability and confidentiality of transmission. In our scheme, chaotic sequences are allocated in the frozen bits of polar codes. Therefore, error correction and encryption can be performed simultaneously. Since the frozen bits are unknown to the eavesdroppers, it is difficult for them to decode the transmitted bits without the knowledge of the chaotic sequences. To further improve the security, we propose to generate the chaotic sequences by using the channel state information. Besides, the chain effects of delayed feedback are applied to increase the decrypted complexity of the eavesdroppers in this paper. Theoretic analysis and simulation results both show that the proposed algorithms can achieve high security without any error rate performance loss.

To defend against eavesdropping and spoofing attacks, the physical layer authentication (PLA) techniques utilize the unique attributes of channel or device for identifying attackers. Among these techniques, the PLA schemes based on channel phase responses use the secret key driven channel phase to authenticate the legitimate user, which have a better performance than the channel amplitude based schemes. However, the prior phase-based schemes only consider the perfect channel correlation coefficient between the two successive timeslots, which differs from the real scenarios. Meanwhile, the closed-form expressions of the theoretical analysis results are not comprehensive in the prior schemes, which are also not tight especially at low signal-to-noise ratio (SNR) regions. In this paper, we propose a PLA scheme based on the channel phase response, aiming to offset the performance loss introduced by the channel correlation coefficient. Moreover, we derive the closed-form expressions of the theoretical analysis results, such as the mean value, the variance and the probability density functions (PDFs), which can be utilized to provide the closed-form threshold for making decision instead of a great ideal of testing. Then, the security analysis is provided to verify the resistance of the proposed scheme under the attacks. Simulation results show that the proposed scheme outperforms the benchmarks and the proposed theoretical results match well with the simulated results even under low SNR regions.

Aiming at the authentication problem in wireless communication, an improved physical layer authentication scheme based on wireless channel phase (PHY-IMACP) is proposed in this letter. In this scheme, legitimate nodes exploit the reciprocity of the channel phase response to conduct information exchange. The secret key information is hidden in the phase of the interactive information, and the authentication judgment is completed by use of binary hypothesis testing. Then the well-designed hypothesis testing statistic is proposed to obtain the better authentication performance. Additionally, mean and variance closed-form expressions of the hypothesis testing statistic in our proposed scheme are given. The simulation results show that the proposed scheme outperforms the benchmark at different conditions of eavesdropping channel.

Due to the threat of various jamming attacks in wireless communications, the efficient and general anti-jamming schemes are required to guarantee communication the quality of wireless networks. To this end, this article proposes the efficient index modulation-based frequency hopping spread spectrum (IM-FHSS) scheme. Unlike the classical IM-FHSS which only considered the reactive jamming, the efficient IM-FHSS scheme extends the anti-jamming capacity to various jamming models. Specifically, we first derive the closed-form expressions of bit error rate (BER) performance of the IM-FHSS under three jamming models in an additional white Gaussian noise (AWGN) channel and a Rayleigh fading channel, which enables the design of anti-jamming strategies. Then, the unified anti-jamming framework is provided for designing the efficient anti-jamming system. Based on the framework, we further provide the strategies of the efficient IM-FHSS for reactive jamming, constant, and random jamming. Simulations show that the theoretical derivations match well with the simulated results, which validates the performance analysis. Moreover, the efficient IM-FHSS has demonstrated the superior anti-jamming performance for three typical jamming models, which is also energy efficient and reliable for achieving targeted BER performance.

Reactive jammer has emerged as a relatively intelligent jamming with low energy cost and high jamming efficiency. Moreover, the jammer can obtain the power-correlated reactive jamming via the cooperation with a malicious user, which imposes a severe threat on the reliability of legitimate users. To solve this issue, this letter proposes an enhanced index modulation based frequency hopping spread spectrum (EIM-FHSS) scheme. Specifically, the strategy of power control in EIM-FHSS is provided where the main step of the strategy is formulated as a general optimization problem. Then we calculate a closed form solution for high signal to noise ratio (SNR), and propose a fast search algorithm for general case to obtain the approximate optimal power with low complexity. Simulation results show that EIM-FHSS can obtain enhanced anti-jamming performance as well as low-complexity compared with the benchmarks.