We describe relay attacks on Bluetooth authentication protocol. The aim of these attacks is impersonation. The attacker does not need to guess or obtain a common secret known to both victims in order to set up these attacks, merely to relay the information it receives from one victim to the other during the authentication protocol run. Bluetooth authentication protocol allows such a relay if the victims do not hear each other. Such a setting is highly probable. We analyze the attacks for several scenarios and propose practical solutions. Moreover, we simulate attacks to make sure about their feasibility. These simulations show that current Bluetooth specifications do not have defensive mechanisms for relay attacks. However, relay attacks create a significant partial delay during the connection that might be useful for detection.
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