Key agreement over wireless fading channels with an active attacker

The problem of establishing a key over a wireless fading channel in the presence of an active attacker is considered. A key agreement protocol that combines the existing source model approach and channel model approach is adopted. First, the attacker's optimal attack strategy for this protocol is characterized. Then, the rate of the key that can be generated under this attack strategy is quantified. It is shown that, unlike the corresponding situation in wireline communications, it is possible to establish a key in the presence of an active attacker in wireless fading channels.