Research On Authentication Protocols Based On Mix-zones Space In VANETs

VANETs(Vehicular ad hoc networks)can provide location-based services for vehicles,realize cooperative communication among vehicles and relieve traffic pressure,but the real-time status information of users needs to be continuously exposed due to the communication feature of the net.Therefore,the location privacy of vehicles may be attacked by the rivals.Based on the previous research of the Mix-Zones programs,this thesis analyzes VANETs from the its overall deployment and finds that the identity and location privacy of vehicle members in VANETs face two kinds of attacks: illegal member's attack from outside VANETs and legitimate member's attacks from within VANETs.In view of the above problems,this thesis takes the secure communication in VANETs as the research object,analyzes the topology structure of VANETs and the communication characteristics among vehicles.And two authentication protocols based on vehicle identity are designed using knowledge signature and group signature technology,respectively,which are used to resist the above two types of attacks.In order to guarantee the privacy of vehicle users,a thorough study is made from the theoretical analysis to the simulation.The main work of this thesis is as follows:Firstly,VANETs is a distributed self-organizing network with fast changing topologies.It is particularly important to provide fast and timely access services for vehicles.Therefore,a fast authentication protocol for vehicle identity in VANETs is designed by using the knowledge signature technology based on double discrete logarithm in this thesis.When vehicles enter the VANETs,they need to request access to the roadside auxiliary units by proving that they known system key through the knowledge-based signature algorithms.Only through the authentication of the vehicle,can the VANETs access service be realized.As a result,snooping and attacks on members of VANETs are resisted by illegal adversaries from outside VANETs.The simulation results show that this scheme can protect the identity and location privacy of vehicle users,and it is also faster than other schemes in the speed of network authentication.Secondly,Since vehicle users traveling in VANETs need to continuously expose their location information,they are vulnerable to adversary attacks from inside the VANETs.For this problem,a vehicle identity based authentication protocol is designed in this thesis by using group signature theory.During the initialization phase of the protocol,the system generates public / private key pairs and parameters,and distributes the public key and shared system parameters to the vehicles by using roadside units,the group private key is kept by the group manager in the VANETs system;Any legitimate group members can use their assigned group public key with the system parameters to signature and complete anonymous communications represent the group;in the event of a dispute,the only thing to do of VANETs management agencies is that to open the signature of the vehicles with group private key.The protocol uses a simple group signature technology,which has the traits that the public key and signature length don't depend on the number of the group members.By testing the speed of message passing and authentication between vehicles,it is found that this protocol can reduce the storage burden and computation cost of vehicle in the process of identity authentication.