A Mobility-Pattern-Based Multi Level Cache Approach For Location Privacy Protection

In recent years,with the rapid development of mobile positioning technology and wireless communication technology,LBS applications widely spread.With LBS,a user can easily acquire interested location-related information anytime.However,in order to obtain the accurate and convenient service,all location-based services require users to send location information as accurately as possible to the LBS provider,which makes the user's location privacy information exposed at the server of service provider.And,these data may be maliciously used.Many methods have been proposed to protect user's location privacy,but in the traditional LBSs model,users need to repeatedly send their location information to the provider's servers or an intermediate Anonymizing Server(AS)for service,which has a lot of problems,such as the low reutilization ratio of the information,the un-trusted service providers and the excessive reliance on AS.The latest cache method gives a new idea,but it does not take users' mobile behavior into account.Noting the issues above,this paper presents a new multi-level location privacy protection method,which combines the users' mobility pattern with cache and uses distributed neighbor users' collaboration to get information and protect location privacy.The main purpose that we design this system is to enhance the protection while maximizing the cache hit ratio and decreasing the communication and storage costs.The contributions of this paper are shown as follows.We designed a distributed multi level cache location privacy protection method,RuleCache,which does not rely on trusted third party.It achieves protection on three levels:the local host,the neighbors' collaboration and the LBS server.According to the inherent characteristics of user mobility pattern,we design a middleware called cacheware to control the contents of the terminal cache which become standardized for the first time.It optimizes the cache storage and improves the cache efficiency.What's more,these middleware makes it possible that user can take interested information from their neighbor users through collaboration.When the user has to send a request to the untrusted server,we propose a Cloaking Region Generating Algorithm(CRGA)to protect user's privacy and try to update the cached data which consider the effects of background knowledge and data timeliness.Finally,we conduct some security analysis of the proposed method,and a comparative simulation is carried out with a variety of methods.The results show that our RuleCache has better performance than other methods in terms of the communication cost,storage cost as well as cache hit ratio.