Location And Trajectory Privacy Protection Methods Based On Anonymity Techique

The deployment of global positioning systems(GPS)provides basic guarantees for location based services(LBSs).Driven by communication technology,location services have achieved a transformation from passive to active,from single to diverse,from content-oriented to application-oriented.Users employ mobile terminals to send their geographic locations and request diversified location service applications.However,untrusted location service providers(LSPs)may divulge the private information of users for their own selfish benefit.The malicious attackers analyze and mine user behaviors and habits,endangering users' physical or property security.Therefore,how to protect location and trajectory privacy has become a challenging issue.This thesis has investigated the effectiveness and practicality of single location privacy protection strategy in LBS,the efficiency of anonymity processing,and the privacy protection of trajectories in data distribution,completed the following innovative work:(1)In terms of privacy protection effectiveness,this thesis proposes a k-chameleon cloaking mechanisms(KCCM)to protect the location privacy of users.Combining k-anonymity technology with bionics,this mechanism imitates the process of chameleon discoloration to provide users with more secure location services.Concretely,this mechanism executes constructing learning region algorithm(CLRA)to determine user's surrounding environment.Next,learning adaption k value(LAKV)algorithm is utilized to confirm optimized k value.Users may be accompanied by geographic semantic information in actual scenarios,judgement geographic semantic algorithm(JGSA)is executed to judge whether there are similar k-1 locations with geographic semantics around user.If it exists,these locations are employed for anonymous protection.If not,the generating dummy locations algorithm(GDLA)generates k-1 locations with uniform distribution for protection.The security analysis theoretically proves that the mechanism can resist the attack of attackers,and the simulation experiment also proves that the mechanism achieves good anonymous protection effect.(2)In terms of anonymity processing efficiency,this thesis presents location privacy protection strategy based on Alt-Geohash coding(LPPS-AGC).This strategy first implements location generalization algorithm(LGA)to generalize the latitude and longitude of user into interval region,then,according to the proposed Alt-Geohash coding algorithm(AGCA)and reverse retrieval algorithm(RRA)to retrieve locations the same as candidate anonymous locations set.Moreover,this strategy provides users with personalized k-anonymous privacy protection services.In this way,this strategy not only considers the altitude of location,but also speeds up the retrieval of the database and reduces time overhead.Simulation results show that this strategy is more efficient than other methods.(3)In terms of privacy protection of trajectory data publishing,this thesis considers the abrupt change of location caused by the change of vehicle in user's trajectory.As user's movement is affected by traffic conditions and weather,the vehicle is often changed and some change points appear in the location,resulting in distribution of trajectory.Aiming at this problem,an anonymous trajectory protection method based on the change points(ATPM-CP)is proposed.The method firstly detects the change point,simplifies the whole trajectory,and then protects the trajectory anonymously.By detecting change points to protect the trajectory anonymously,the generated trajectory is more in line with the user's movement rules,and it is difficult to distinguish it from the real trajectory.The law of identifying the real trajectory by the attacker is reduced,which better protects the user's trajectory privacy and protects the user's rights and interests.The simulation reveals show that the method is effective in various evaluation indexes.