The Research Of Loaction Privacy-preserving Methods Based On Anchor Technology In LBS

Location based service(LBS)not only brings a lot of convenience to people's life,but also leads to location privacy leakage.There are many researches on location privacy preserving,including the protecting technologies based on false location,which have been widely studied,its core idea is to submit several fake locations accompanied with a user's actual location or submit one fake location instead of a user's actual location to LBS server for places of interest(PoIs).As a kind of fake-location technology,anchor technique is widely used to replace a user's actual location and sent to the LBS server as a querying tag,it is an effective method for protecting location privacy,but the several defects exist,which need to be improved:(1)a user is staying in a sensitive area and he may select an anchor point which is still located in sensitive areas,that brings the user's privacy leakage owing to semantic association;(2)the existing anchor technologies are all used for snapshot query of a static user,not does not applicable to continuous query of a dynamic user;(3)in the road network environment,PoIs query results are calculated based on Euclidean distance with an anchor,which are not accurate,it is lack of research on anchor technology in road network environment;(4)anonymity of the location leads to the unnecessary results in the query procedure,the PoI query result may include text,pictures and videos,that lead to large amount of data communication.This dissertation is supported by the National Natural Science Foundation "Research on Privacy Protection Technology for Internet of Things Based on Location Based Service"(61472097),and the Doctoral Program of Higher Education Research Fund "The Research on Location Privacy Preserving in LBS"(20132304110017).The research contents are as follows:(1).A Research of LBS Location Privacy Preserving Based on Sensitive Diversity Anchor.Before getting location-based query service,constructing a cloaking region or picking an anchor which is still in a sensitive area is vulnerable to lead location privacy exposure.An algorithm of selecting anchor is proposed based on sensitive location diversity.By defining sensitive locations and filtering different ones according to users' visiting number and peak time,locations with similar features are chosen to form a diversity zone,and its centroid is taken as the anchor' location which raises user' location diversity.Based on the anchor,a query algorithm for PoIs is proposed referring to SpaceTwist,and query results canbe deduced without providing any user's actual location.The defect in SpaceTwist,which PoIs are found around the anchor,is modified,it improves querying accuracy.The experiments show that users' location privacy is protected well when he is staying at a sensitive place,and the method has good working performances.(2).A Location Privacy Preserving Method in LBS Based on Continuous Anchors.In view of unapplicable of static anchor in continuous query,we propose a novel location privacy preserving method based on Voronoi graph partition for dynamic user.We present users' travel direction prediction as a precondition,a cooperative anonymous method is proposed without constructing cloaking regions which may lead efficiency decline in continuous query.And then,a query algorithm is proposed without providing any user's actual location,replaced by continuous anchors sequence,to LBS provider.This algorithm can work out precise results according to candidate set returned by LBS provider.(3).Location Privacy Preserving Method Based on Anchor in Road Networks.Location privacy preserving and query service quality is a pair of contradiction in location based service.Based on the characteristics of intersection vertices will be reached by users,a query algorithm is proposed firstly,which picks intersections of the road network gradually to form an anchor sequence to query for places of interest,the users in different roads of the same intersection vertice achieve k anonymity by sharing the same anchor,the query algorithm can not only achieve location privacy preservation but also increase query accuracy.And then,based on the idea of injecting fake queries and constructing query anonymity group,a trajectory privacy preservation algorithm is proposed,which is used to resist continuous query correlation attack and movement model inference attack.(4).A Privacy Preserving Method with Low Communication Cost in LBS.Achieving KNN query with blurry location brings higher communication cost,based on hierarchical index quadtree structure of PoIs,a querying method with cloaking region is proposed for location privacy preserving.The method takes the distribution of PoIs into consideration,and assures the query taget stronger,so that the communication cost is decreasing as the returned useless PoIs is fewer compared with traditional cloaking region query.