Secret Key Generation through OFDM Multipath Channel

We study the generation of secret keys based on the inherent randomness of wireless multipath channels. This study falls into the broad area of physical layer security. In this setting the objective is for a pair of users, Alice and Bob, to extract a secret key from a natually occurring source of randomness observed by two users. The central idea is that through a public discussion, Alice and Bob can de-noise their correlated observations to generate, with high probability, a commonly known string, which can serve as the key. An eavesdropper, named Eve, would use both her knowledge of the public message and any observation she has to guess the key. We show in our work how common randomness can be exploited from channel characteristics in terms of channel coefficients and we propose a functional design. We also compare our work with an existing secret key generation method based solely on received signal strength (RSSI).