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Physical Communication

A new practical physical layer secret key generation in the presence of an untrusted relay

Mohammadreza Keshavarzi, Hadi Zayyani, Ali Kuhestani, Hossein Ahmadi

Published May 31, 2024• 6 citations
Publisher
DOI
10.1016/j.phycom.2024.102407

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Physical layer (PHY) secret key generation (SKG) has been widely studied as a promising approach to achieving One-Time-Pad security. The improvement of SKG rate is quite a huge challenge, especially in scenarios with untrusted internal helpers or eavesdroppers that aim to wiretap the negotiated secret keys between legitimate parties. In this paper, we propose a token-based SKG scheme to deal with the problem of information leakage with internal eavesdropping attacks. The basic idea is to cover random pilots with protective tokens to confuse eavesdroppers. Three scenarios including passive external eavesdropping, active internal eavesdropping with a reconfigurable intelligent surface (RIS)-assisted untrusted helper, and active internal eavesdropping with an untrusted relay are considered and analyzed to evaluate the performance of the proposed anti-eavesdropping scheme. Theoretical analysis shows that the proposed token-based SKG scheme can perfectly secure the key negotiation, achieving zero information leakage even in the untrusted relaying scenario without a direct link between Alice and Bob. Moreover, closed-form expressions for secret key capacity (SKC) are obtained. Finally, numerical results indicate that the proposed scheme outperforms the state-of-the-art methods. Using a token-generation mapping function with greater diversity in amplitude and phase, our approach achieves enhanced SKC performance across various scenarios, including those with a passive eavesdropper, a RIS-assisted untrusted helper, and an untrusted relay.

IEEE Transactions on Information Forensics and Security•Jan 1, 2025•9 citations
In this paper, we propose a physical-layer secret key generation scheme for multi-antenna legitimate nodes with the help from multiple untrusted relays with single antenna. The relays' actions conform to the rules but they passively eavesdrop the information. Different from most previous key generation schemes, where a key is generated based on a channel coefficient, in the proposed scheme, we use the linear combination of channel coefficients to generate a key. Simulation results show that the rate leaked to the untrusted relays is low and the secret key rate is therefore high. We also point out that the relay communication can achieve higher secret key rate than the direct communication in several distance ranges.
In this paper, we propose a physical-layer secret key generation scheme for multiantenna legitimate nodes with the help of multiple untrusted relays, equipped with multiple antennas. The untrusted relays conform to the relaying transmission protocol of legitimate nodes, but they also eavesdrop the confidential information of an legitimate transmitter. The key generation scheme is designed with zero forcing (ZF) and minimum mean square error (MMSE) channel estimators for non-, partially, and fully colluding modes of untrusted relays. Furthermore, we propose a scheme adaptive to channel coherence time. Specifically, to achieve a higher secret key rate (SKR) within the channel coherence time, the number of relay and legitimate nodes' antennas are optimally determined and the most suitable antennas are selected for the key generation. Our results show that the proposed scheme achieves a higher SKR than a prior work, and non- and partially colluding modes provide a higher SKR than the fully colluding mode through the proposed scheme. We also verify that exploiting more antennas of untrusted relays does not always enhance the SKR by showing the existence of the optimal number of antennas of the relays participating in the scheme.
Physical layer (PHY) secret key generation (SKG) has been widely studied as a promising approach to achieving One-Time-Pad security. The improvement of SKG rate is quite a huge challenge, especially in scenarios with untrusted internal helpers or eavesdroppers that aim to wiretap the negotiated secret keys between legitimate parties. In this paper, we propose a token-based SKG scheme to deal with the problem of information leakage with internal eavesdropping attacks. The basic idea is to cover random pilots with protective tokens to confuse eavesdroppers. Three scenarios including passive external eavesdropping, active internal eavesdropping with a reconfigurable intelligent surface (RIS)-assisted untrusted helper, and active internal eavesdropping with an untrusted relay are considered and analyzed to evaluate the performance of the proposed anti-eavesdropping scheme. Theoretical analysis shows that the proposed token-based SKG scheme can perfectly secure the key negotiation, achieving zero information leakage even in the untrusted relaying scenario without a direct link between Alice and Bob. Moreover, closed-form expressions for secret key capacity (SKC) are obtained. Finally, numerical results indicate that the proposed scheme outperforms the state-of-the-art methods. Using a token-generation mapping function with greater diversity in amplitude and phase, our approach achieves enhanced SKC performance across various scenarios, including those with a passive eavesdropper, a RIS-assisted untrusted helper, and an untrusted relay.