Physical Layer Security via Secret Sharing Over Time Modulated Arrays

This work presents a novel secure communication protocol that leverages beamforming geometry and time-modulated arrays (TMAs) to guarantee arbitrarily low probability of successful eavesdropping by a passive adversary. This is achieved by implementing additive secret sharing, a cryptographic scheme, over a TMA deployed at the transmitter. In this approach, the message m is split into n shares (S₁,…, Sn), such that recovering the message requires interception of every share. These shares are then transmitted over separate time slots, each using a distinct TMA-synthesized beam pattern. Theoretical and measurement results using a 16-element TMA demonstrate that for n=4 shares, the protocol enforces a Bit Error Rate (BER) > 0.1 for any eavesdropper, even assuming 10 dB higher overall channel gain at the adversary compared with the intended receiver. Unlike existing physical-layer security (PLS) mechanisms, the proposed protocol is energy efficient, computationally lightweight, and agnostic to channel conditions and adversary’s location.