This paper introduces a new perspective on securing wireless status-update systems by combining physical-layer security with the concept of information freshness. Instead of relying on traditional secrecy metrics such as secrecy capacity or outage probability, the authors focus on Age of Information (AoI) to evaluate how effectively a system prevents an eavesdropper from keeping up with the legitimate receiver. Since the value of information in IoT and monitoring applications depends heavily on how fresh it is, the goal in the presence of a passive adversary is not only to limit what the eavesdropper can decode but also to ensure that their view of the system becomes outdated. To capture this, the paper proposes two secrecy metrics: secrecy age, which measures how much “staler” the eavesdropper’s information is compared to the legitimate receiver’s, and secrecy age outage probability, which quantifies the likelihood that the eavesdropper’s information is not sufficiently outdated.
The study then analyzes how different transmission strategies influence secrecy. Under a randomized stationary policy, the source transmits new updates with a fixed probability, enabling closed-form characterization of both secrecy metrics. Under a threshold-based policy, the source transmits only when the legitimate receiver’s age exceeds a specified threshold, allowing for more intentional control of update timing to keep the eavesdropper further behind. Both policies are modeled using a two-dimensional Markov chain that tracks the joint age evolution at the legitimate receiver and the eavesdropper, and the paper provides guidelines for optimizing the transmission probability or threshold. Overall, by shifting the focus from channel capacity to information freshness, the work shows that secrecy in IoT systems can be enhanced without heavy cryptographic mechanisms: well-designed transmission policies alone can ensure that the eavesdropper consistently receives outdated information, even under unreliable wireless conditions.
Secure_Status_Updates_under_Eavesdropping_Age_of_Information-based_Secrecy_Metrics