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International Conference on Communications and Broadband Networking (ICCBN)

LOBBY: A Novel Physical-layer Key Generation Method

Yinghao Xu, Aiqun Hu, Guyue Li

Published Feb 25, 2021• 0 citations
Publisher

Abstract

Physical-layer key generation (PKG) relying on wireless channel reciprocity has become a potential research topic as it can provide information-theoretic security guarantees. Various PKG protocols have been proposed to improve key generation rate. However, as a key generation scheme, key rate is not the only important feature. Availability in practical scenario and security resistance are also valuable to be focused on. In order to achieve the availability under quasi-static environment and nearby attack, a scheme named loop-one-block-back key (LOBBY) key generation is proposed. Compared with algorithms raised before, LOBBY only needs one time-frequency block to transmit signal back which saves a quarter energy than conventional algorithms, but still has a powerful bit generation rate (BGR) as before. The simulation of LOBBY shows that correlation of subsequent keys keeps flat near 0.5 in quasi-static environment. As for bit disagreement ratio (BDR) between authorized users, it is less than 0.05 when SNR is 15dB.

DOI
10.1145/3456415.3456464

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Physical-layer key generation (PKG) relying on wireless channel reciprocity has become a potential research topic as it can provide information-theoretic security guarantees. Various PKG protocols have been proposed to improve key generation rate. However, as a key generation scheme, key rate is not the only important feature. Availability in practical scenario and security resistance are also valuable to be focused on. In order to achieve the availability under quasi-static environment and nearby attack, a scheme named loop-one-block-back key (LOBBY) key generation is proposed. Compared with algorithms raised before, LOBBY only needs one time-frequency block to transmit signal back which saves a quarter energy than conventional algorithms, but still has a powerful bit generation rate (BGR) as before. The simulation of LOBBY shows that correlation of subsequent keys keeps flat near 0.5 in quasi-static environment. As for bit disagreement ratio (BDR) between authorized users, it is less than 0.05 when SNR is 15dB.
Physical layer security key generation exploits unpredictable features from wireless channels to achieve high security, which requires high reciprocity in order to set up symmetric keys between two users. This paper investigates enhancing the channel reciprocity using a loop-back scheme with multiple frequency bands in time-division duplex (TDD) communication systems, in order to mitigate the effect of hardware fingerprint interference and synchronization offset. The scheme is evaluated to be robust to passive eavesdropping and active Man-in-the-Middle attack through both theoretical analyses and practical measurements. A secret key generation protocol is subsequently designed. The performance of the proposed secret key generation method is then evaluated through both numerical simulation and experiments. Results demonstrate that the proposed scheme can effectively mitigate non-reciprocity and outperforms the classical TDD scheme in both key disagreement rate and key generation rate.
In physical-layer secret key generation, key generation performance is susceptible to hardware impairments (HIs), which can degrade channel reciprocity. Additionally, the security of loop-back mechanism based schemes in frequency division duplex (FDD) systems requires further enhancement. To address these challenges, this paper proposes a secure key generation scheme based on a loop-back mechanism for FDD systems. By transmitting signals across different frequency bands in a loop-back fashion, the proposed scheme mitigates the adverse effects of HI variations across frequency bands and enhances system security. Theoretical analyses are conducted on the normalized mean square error and the secret key rate of the loop-back mechanism in both FDD and time division duplex (TDD) systems, providing a clear security assessment of the proposed scheme. Simulation and experimental results demonstrate that by accounting for HI differences in the frequency domain, the proposed scheme improves channel reciprocity, enhances the secret key rate, achieves a higher key generation ratio (KGR), and reduces the key disagreement rate (KDR) compared to state-of-the-art methods.
In the physical-layer key generation, the channel reciprocity is vulnerable to hardware impairments (HIs) that can adversely impact the performance of key generation, and the security of loop-back mechanism based schemes in frequency division duplex (FDD) systems remains to be improved. To enhance both channel reciprocity and system security, this paper proposes a secure and highly reciprocal key generation scheme in FDD system by increasing the number of loop backs. By transmitting signals via different frequency bands in the loop-back mechanism, the proposed scheme can eliminate the adverse effects of the variations in HIs across different frequency bands and can improve system security. The normalized mean square error performance of the proposed scheme is theoretically analyzed and the security of the proposed method is illustrated. The simulation and experimental results demonstrate that by considering HIs differences during the design process, the proposed loop-back mechanism based scheme can enhance the channel reciprocity and achieve higher key generation ratio, and lower key disagreement rate compared with the state-of-the-art method.
Physical-layer key generation (PKG) establishes cryptographic keys from highly correlated measurements of wireless channels, which relies on reciprocal channel characteristics between uplink and downlink, is a promising wireless security technique for Internet of Things (IoT). However, it is challenging to extract common features in frequency-division duplexing (FDD) systems as uplink and downlink transmissions operate at different frequency bands whose channel frequency responses are not reciprocal anymore. Existing PKG methods for FDD systems have many limitations, i.e., high overhead and security problems. This article proposes a novel PKG scheme that uses the feature mapping function between different frequency bands obtained by deep learning to make two users generate highly similar channel features in FDD systems. In particular, this is the first time to apply deep learning for PKG in FDD systems. We first prove the existence of the band feature mapping function for a given environment and a feedforward network with a single hidden layer can approximate the mapping function. Then, a key generation neural network (KGNet) is proposed for reciprocal channel feature construction, and a key generation scheme based on the KGNet is also proposed. Numerical results verify the excellent performance of the KGNet-based key generation scheme in terms of randomness, key generation ratio, and key error rate. Besides, the overhead analysis shows that the method proposed in this article can be used for resource-constrained IoT devices in FDD systems.
Wireless network security is crucial for modern communication systems, requiring robust security mechanisms to safeguard transmitted data. Physical layer security, leveraging channel characteristics for key generation, has emerged as a promising approach. In this paper, we study the process of generating and sharing keys among authorized users without compromising secrecy. However, existing methods face challenges, particularly with a high rate of errors in the generated keys and the risk of using the same key multiple times, which could compromise security. We have explored generating a unique key for each session. Our study examines the bit generation rate and verify the consistency of the secure key. We found the trade-off between the number of symbols and the quantization levels for quadrature amplitude modulation as well as binary phase shift keying. Further, the discussion delves into the impact of channel non-reciprocity on the process of secure key generation. Moreover, we achieved almost zero bit error rate at high signal-to-noise ratio.
Physical layer key generation that exploits reciprocity and randomness of wireless fading channels has attracted considerable research attention in recent years. Although theoretical study has shown its potential to generate information- theoretic secure keys, great challenges remain when transforming the theory into practice. This article provides an overview of the physical layer key generation process and discusses its practical challenges. Different passive and active attacks are analyzed and evaluated through numerical study. A new key generation scheme using random probing signals, and combining user generated randomness and channel randomness, is introduced as a countermeasure against active attacks. The numerical results show that the proposed scheme achieves higher security strength than existing schemes using constant probing signals under active attacks. Future research topics on physical layer key generation are discussed.