On secret key generation through multipath for wireless networks

The complexity of cryptographic key management and the wireless medium salient features motivated a number of works that generate secret keys. Simply put, two nodes can estimate their wireless channel and derive common information to generate a key that other nodes cannot obtain. A gamut of methods, each drawing this information in a different manner, has been proposed. In this landscape, this paper contributes a few findings. First, we propose a method that renders channel impulse response magnitude samples roughly uniform, thus facilitating their quantization and agreement on the derived secret keys. We provide a characterization of the probability of successful agreement for this method, which could be useful for other related methods. Moreover, we consider the cost of the key agreement and we propose a trade-off to increase the probability of success while increasing local processing. With an appropriate configuration, a significant reduction in protocol rounds, and thus communication overhead, for key agreement can be achieved. Through simulations, we validate our approximation of the probability of success and demonstrate the reduced communication overhead.