Integrating Communication, Sensing and Security: Progress and Prospects of PLS in ISAC Systems

The sixth generation of wireless networks (6G) defines several key performance indicators (KPIs) for assessing its networks, mainly in terms of reliability, coverage, and sensing. In this regard, remarkable attention has been paid recently to the integrated sensing and communication (ISAC) paradigm as an enabler for efficiently and jointly performing communication and sensing using the same spectrum and hardware resources. On the other hand, ensuring communication and data security has been an imperative requirement for wireless networks throughout their evolution. The physical-layer security (PLS) concept paved the way to catering to the security needs in wireless networks in a sustainable way while guaranteeing theoretically secure transmissions, independently of the computational capacity of adversaries. Therefore, it is of paramount importance to consider a balanced trade-off between communication reliability, sensing, and security in future networks, such as the fifth generation of wireless networks (5G) and beyond and the 6G. In this paper, a comprehensive and system-wise review of designed secure ISAC systems, from a PLS point of view, is provided. In particular, the impact of various physical-layer techniques, schemes, and wireless technologies to ensure the sensing-security trade-off is studied from the surveyed work. In addition, the review is enriched by notable takeaways on each transmission technique and wireless technology’s potential and limitations in establishing robust and secure ISAC networks. Different from previous related surveys, the current work reviews and categorizes PLS schemes in the context of ISAC under three main categories, namely confidentiality, communication covertness, and authentication, covering a broader secrecy perspective with different types of attacks, such as eavesdropping, sensing spoofing, and jamming. The paper also serves as a tutorial by presenting several theoretical foundations on secure ISAC networks, which represents a practical guide for readers to develop novel secure ISAC network designs.