Footprint: Detecting Sybil Attacks in Urban Vehicular Networks

Abstract:    

In urban vehicular networks, where privacy, especially the location privacy of  

anonymous vehicles is highly concerned, anonymous verification of vehicles is 

indispensable. Consequently, an attacker who succeeds in forging multiple 

hostile identifies can easily launch a Sybil attack, gaining a disproportionately 

large influence. In this paper, we propose a novel Sybil attack detection 

mechanism, Footprint, using the trajectories of vehicles for identification while 

still preserving their location privacy. More specifically, when a vehicle 

approaches a road-side unit (RSU), it actively demands an authorized message 

from the RSU as the proof of the appearance time at this RSU. We design a 

location-hidden authorized message generation   scheme for two objectives: 

first, RSU signatures on messages are signer ambiguous so that the RSU 

location information is concealed from the resulted authorized message; 

second, two  authorized messages signed by the same RSU within the same 

given period of time (temporarily linkable) are recognizable so that they can 

be used for identification. With the temporal limitation on the likability of two 

authorized messages, authorized messages used for long-term identification 

are prohibited. With this scheme, vehicles can generate a location-hidden 

trajectory for location-privacy-preserved identification by collecting a 

consecutive series of authorized   messages. Utilizing social relationship among 

trajectories according to the similarity definition of two trajectories, Footprint 

can recognize and therefore dismiss “communities” of Sybil trajectories. 

Rigorous security analysis and extensive trace-driven simulations demonstrate 

the efficacy of Footprint.

The design of a Sybil attack detection scheme in urban vehicular networks should achieve three goals:


1. Location privacy preservation: a particular vehicle would not like to 

expose  its location information to other vehicles and RSUs as well since such 

information can be confidential. The detection scheme should prevent the 

location information of vehicles from being leaked.

2. Online detection: when a Sybil attack is launched, the detection scheme 

should react before the attack has terminated. Otherwise, the attacker could 

already achieve its purpose.

3. Independent detection: the essence of Sybil attack happening is that the 

decision is made based on group negotiations. To eliminate the possibility that 

a Sybil attack is launched against the detection itself, the detection should be 

conducted independently by the verifier without collaboration with others.