A Randomized Space-Time Transmission Scheme for Secret-Key Agreement

In contrast to the pessimistic view on perfect secrecy, studies on information-theoretic secrecy have shown that perfect secrecy may be possible in practice. A typical example is the Wyner’s wire-tap channel concept. However, existing approaches mostly depend on unrealistic noise or error-rate assumptions. We propose a more practical way in this paper which uses advanced space-time transmissions for enhanced information-theoretical secrecy. Based on the fundamental limits of MIMO blind channel identification, space-time transmissions with proper randomization can effectively prevent the adversary from channel estimation while allowing reliable transmission between the authorized parties. The high error rate suffered by the adversary enhances secret channel capacity. This paper points out a new and practical approach for secret-key agreement which achieves perfect secrecy based on the physical-layer signal processing techniques.