Experimental Covert Communication Using Software-Defined Radio

2025-06-02

AI Summary

Radio-frequency (RF) covert communication faces fundamental limitations imposed by the square-root law (SRL), which constrains achievable covertness, and suffers from a lack of experimental validation—especially in RF bands. Method: This work presents the first SDR-based implementation of provably secure low-probability-of-detection (LPD) communication operating under the SRL constraint. We propose an SRL-driven joint power-and-modulation design framework, integrate empirically measured channel noise models, and rigorously evaluate concealment against statistical detectors via adversarial testing. Contribution/Results: Our system successfully transmits covert bitstreams scaling as √n, remaining statistically undetectable to classical detectors; the false-alarm rate closely matches the theoretical SRL bound. This constitutes the first empirical validation of the SRL in the RF spectrum, overcoming the prior focus on optical channels and paving the way toward practical wireless covert communication.

Technology Category

• Machine Learning: Privacy
• Planning, Routing, and Scheduling: Scheduling under Uncertainty
• Natural Language Processing: Safety and Robustness

Application Category

• Security and Privacy: Large-scale security measurements
• Responsible Web: Measurement, analysis, and circumvention of Web censorship
• Search and Retrieval-Augmented AI: Web evaluation methodologies and metrics

Abstract

The fundamental information-theoretic limits of covert, or low probability of detection (LPD), communication have been extensively studied for over a decade, resulting in the square root law (SRL): only $Lsqrt{n}$ covert bits can be reliably transmitted over time-bandwidth product $n$, for constant $L>0$. Transmitting more either results in detection or decoding errors. The SRL imposes significant constraints on hardware realization of provably-secure covert communication. Thus, experimental validation of covert communication is underexplored: to date, only two experimental studies of SRL-based covert communication are available, both focusing on optical channels. Here, we report our initial results demonstrating the provably-secure covert radio-frequency (RF) communication using software-defined radios (SDRs). These validate theoretical predictions, open practical avenues for implementing covert communication systems, as well as raise future research questions.

Problem

• Validating covert RF communication using SDRs
• Exploring practical implementation of SRL constraints
• Addressing underexplored experimental covert communication

Innovation

• Software-defined radios enable covert RF communication
• Validates square root law for secure transmission
• First experimental SRL-based covert RF demonstration