Programmable Metasurface-Empowered Secure Multi-Party Communication with Threshold Cryptography

The expansion of high-speed wireless networks and increasing reliance on connectivity necessitate advanced security beyond traditional software encryption. Programmable metasurface-assisted secret sharing cryptography offers the opportunity of joint software- and physical-layer encryption but requires all secret fragments for decryption, which compromises system robustness and secure communication continuity in adversarial scenarios. To address these challenges, we introduce a secure multiparty communication architecture integrating threshold secret sharing with dynamic beam manipulation. At the software layer, the secret is divided into shares using a threshold cryptography scheme, with the decryption threshold adjusting dynamically to security needs, allowing reconstruction only with authorized subsets of participants. Simultaneously, the metasurface disperses cryptographic shares spatially via beamforming and spectral control, ensuring intercepted channels provide only non-decryptable fragments. The system enables secret reconstruction without needing all fragments, and decryption occurs when the number of available shares meets a pre-defined threshold. This fault-tolerant design ensures operational continuity even with partial share loss, enhancing communication reliability and system resilience in adversarial conditions. Experiments demonstrate the system's superior adaptability, capacity, and fault tolerance. By combining cryptographic protocols with real-time electromagnetic control, this research advances the development of next-generation secure wireless networks, facilitating robust multiparty communications even in hostile environments.