Scenario Analysis of Key Entropy Loss from Improper Quantization Decision in Wireless Physical-Layer Security

In wireless physical-layer security, it is usually suggested in literature that eavesdroppers need to locate themselves near legitimate transmitters or receivers if they want to steal some secret key information. By means of scenario analysis, this paper shows that if the eavesdropper knows the channel statistics better than the legitimate stations, e.g., know the K-factor estimates of Rician fading channel, they can exploit these knowledges to derive some secret key information. We define a concept called “improper quantization decision loss $\left(I_{I D L}\right)$” as the entropy loss in the generated key that can be obtained by the eavesdropper. We show step-by-step how the eavesdropper can obtain such information. We also propose a mathematical expression and numerical value of $I_{I D L}$ based on empirical values of channel parameters available in literature. If the legitimate parties are aware of this approximated $I_{I D L}$, they will be able to design suitable privacy amplification scheme for preventing key information loss.