Physical Layer Security via Secret Sharing over Time Modulated Arrays

This work presents a novel physical-layer secure communication protocol that guarantees arbitrarily low probability of eavesdropping success by a passive adversary leveraging beamforming geometry and time-modulated arrays. This is achieved by integrating the mechanism of additive secret sharing, a primitive tool in cryptography, with a Time-Modulated Array deployed at the transmitter antenna array. In this approach, the secret message 𝑚 is split into 𝒏 shares (𝐬𝟏,…,𝐬𝐧), such that recovering the message requires the interception of every share. The protocol transmits each share 𝒔𝒊 across a distinct time slot, employing the TMA to synthesize a unique beam-pattern for each transmission. Specifically, we design a set of dynamic beam-patterns with minimally overlapping sidelobes, ensuring that no stationary adversary located outside the main lobe can consistently recover the complete set of shares. Theoretical and measurement results using a 16-element TMA demonstrate that for 𝒏=𝟒 shares, the protocol enforces a Bit Error Rate >𝟎.𝟏.