Effects of Passive Negative Correlation Attack on Sensors Utilizing Physical Key Extraction in Indoor Wireless Body Area Networks

Due to the unique properties of wireless body area networks (WBANs), a strategically positioned eavesdropper can achieve a channel with negative correlation. This article demonstrates that negative correlation can be exploited and poses a significant threat for sensors utilizing key extraction techniques that rely on the physical layer and make use of channel-state information. In particular, we show that a commonly used method to improve key agreement between legitimate parties, such as moving average, boosts the confidence of the negatively correlated attacker by 23%. We also show that the quantizer parameters need to be selected carefully to avoid information leak. Interestingly, our results indicate that such an attacker can be located much farther from the legitimate party and can gain more information as compared to an adversary that is located closer but does not experience negative correlation.