Physical-Layer-Enhanced Wireless Secret Key Exchange

We address the problem of efficiently establishing a shared secret key over an open wireless channel in the presence of an active (jamming) adversary. A commonly employed technique in practice for key sharing is the cryptographic ellipticcurve Diffie-Hellman (DH) protocol; however, its communication cost in a jammed environment is very high. Hence, we employ novel physical-layer techniques to enhance the performance of the DH protocol in a wireless setting. Specifically, we propose a protocol that exploits the randomness inherent to the wireless environment by testing rapidly for time-frequency bands where success can be obtained, essentially probing for those bands that are favorable to the communicating parties and unfavorable to the adversary. The proposed protocol is significantly more energy and time efficient than the standard DH approach, and addresses a number of deficiencies of previous protocols that also attempt to break the circular dependency that arises when bootstrapping secure wireless communications.