  In this paper, we present two practical ARQ-Based security schemes for Wi-Fi
and RFID networks. Our proposed schemes enhance the confidentiality and
authenticity functions of these networks, respectively. Both schemes build on
the same idea; by exploiting the statistical independence between the multipath
fading experienced by the legitimate nodes and potential adversaries, secret
keys are established and then are continuously updated. The continuous key
update property of both schemes makes them capable of defending against all of
the passive eavesdropping attacks and most of the currently-known active
attacks against either Wi-Fi or RFID networks. However, each scheme is tailored
to best suit the requirements of its respective paradigm. In Wi-Fi networks, we
overlay, rather than completely replace, the current Wi-Fi security protocols.
Thus, our Wi-Fi scheme can be readily implemented via only minor modifications
over the IEEE 802.11 standards. On the other hand, the proposed RFID scheme
introduces the first provably secure low cost RFID authentication protocol. The
proposed schemes impose a throughput-security tradeoff that is shown, through
our analytical and experimental results, to be practically acceptable.
