A method for defensing against multi-source Sybil attacks in VANET

Sybil attack can counterfeit traffic scenario by sending false messages with multiple identities, which often causes traffic jams and even leads to vehicular accidents in vehicular ad hoc network (VANET). It is very difficult to be defended and detected, especially when it is launched by some conspired attackers using their legitimate identities. In this paper, we propose an event based reputation system (EBRS), in which dynamic reputation and trusted value for each event are employed to suppress the spread of false messages. EBRS can detect Sybil attack with fabricated identities and stolen identities in the process of communication, it also defends against the conspired Sybil attack since each event has a unique reputation value and trusted value. Meanwhile, we keep the vehicle identity in privacy. Simulation results show that EBRS is able to defend and detect multi-source Sybil attacks with high performances.