Physical Layer Security via Secret Sharing over Time Modulated Arrays

Shuo Feng

Amr Mohamed Abdelaziz, Ashraf D. Elbayoumy

Security in physical and application layers have been always thought of as a complementary paradigm. In this paper, we argue that potential cooperation between physical and application layers provides several advantages and unique features that are not available in each paradigm by itself. The problem of exchanging confidential messages between nodes, A and B, in the presenceof an active adversary, E, over an insecure MIMO channel is considered. We introduce a double layer spatial signature modulation (SSM) in which the transmitted information is conveyed into the spatial signature of the transmitting antenna array observed by the intended receiver. Meanwhile, any other eavesdropper does not share the same bearing angle of the legitimate receiver obtains infinitesimally small amount of information. Further, to establish a secure link, A and B are required to share a secret common information prior to communication while keeping E ignorant about it. To that end, we introduce a novel physical layer assisted secret key agreement (SKA) protocol that leverages the cooperation between physical and application layer security. Angle of Arrival (AoA) and Angle of Departure (AoD) are physical layer parameters that can be exploited not only for their well performance at low SNR, but also for their contextual meaning that provides security advantages. In the proposed SKA protocol, AoA is explored as a physical mean for message source authentication, meanwhile, AoD is used as a common source of randomness in a smart signal processing approach to generate secret key bits without any extra communication overhead. We show that E can be kept ignorant about the generated key bit stream conditioned on its physical location. This work introduces the notion of physical hardness to an adversary pursuing either active or passive strategy. After establishing a secret common information, we show that the continuous use of AoA as a mean for message source authenticity provides a considerable advantage against active adversary during the message exchange phase. Extending the proposed scheme to a mobile communication environment is also provided. Finally, quantitative analysis for the security gain due to the potential cooperation between physical and application layer security is developed..

Israt Ara, Brian Kelley

This paper presents a new class of precoder-based Physical Layer Security (PLS) algorithms for 6G mobile networks, a significant advancement that combines security and ultra-reliable low latency communications (S-URLLC). The paper also explores the potential of S-URLLC algorithms for realtime shared secret key information exchange in Layer-1 transmission and proposes AI/ML-based detection algorithms for natively securing future 6G-IoT networks against remote eavesdropping. The paper marries a temporal-spatial M-dimensional code with operator matrices drawn from the class of random unitary (precoder) operators to jointly guarantee ultra-reliability and security. The code delivers ultra-reliability, while the precoder operator safeguards the signal waveform from eavesdroppers. The shared secret key-based model operating within a Hyper-Dimensional Temporal-Spatial Precoding with ML-based decoding (HD-TSP-ML) scheme scales across multi-antenna array sizes and codebook modulation orders and delivers impressive 1215 dB improvements in link reliability. The security analysis of Bit Error Rate (BER) versus Signal-to-Noise Ratio (SNR) of intended receiver versus eavesdropper reveals a low probability of interception by malicious eavesdroppers, even when the passive eavesdropper observes in a high SNR, correlated channel with the intended recipient. The paper presents a system architecture of the shared secret key HD-TSP-ML model, discusses simulation result evaluation of the BER of secret information exchanged for the algorithm in Rayleigh fading plus noise and analyzes numerical model of the transmit data-rate versus MIMO array size as well as latency for the system along with a complexity analysis.

Li Wang

Dutliff Boshoff, Raphael E. Nkrow, Bruno Silva +1 more

Physical Layer Key sharing has become a popular topic in today's literature, as it could act as an alternative to computationally expensive RSA protocols. Its importance is emphasized by a number of resource-constrained, battery-powered autonomous robots and personal devices which need to communicate with a wider network. Physical layer key sharing often explores using temporally and spatially variant characteristics of a signal, such as a Wi-fi's channel state information, to produce the same secret keys at different devices. In recent years, Decawave has released an off-the-shelf plug-and-play ultrawideband (UWB) module, which has opened up new possibilities for key sharing. In this paper, we demonstrate how the channel impulse response (CIR) produced by the Decawave module is able to produce secret keys with a bit agreement rate(BAR) of over 89% at different devices in a network. In addition, we provide detailed information on the CIR and the BAR in different real-life environments as well as different scenarios in those environments. Finally, we examine the effect of different types of attackers and show that our system maintains a high level of security. Our paper aims to pioneer a new branch of UWB physical layer key-sharing, which utilizes off-the-shelf modules compared to complex and time-consuming setups.

Matthieu R. Bloch