A New Grid-Based Cloaking Algorithm for Privacy Protection in Location-Based Services

A New Grid-Based Cloaking Algorithm for Privacy Protection in Location-Based Services

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A New Grid-Based Cloaking Algorithm for Privacy Protection in Location- Based Services Jungho Um, Hyeongil Kim, Youngho Choi and Jaewoo Chang Dept. of Computer Engineering, Chonbuk National Univ., Chonju, Chonbuk 561-756, South Korea {jhum,hikim,yhchoi}@dblab.chonbuk.ac.kr, jwchang@chonbuk.ac.kr Abstract In Location-Based Services (LBSs), users send location-based queries to LBS servers along with their exact locations, but the location information of the users can be misused by adversaries. For this, a mechanism to deal with the users’ privacy protection is required. In this paper, we propose a new cloaking algorithm for privacy protection in LBSs. Our cloaking algorithm can support both k-anonymity and l-diversity. That is, it first creates a minimum cloaking region by finding l buildings (l-diversity) and then finds k users (k-anonymity). To generate the minimum cloaking region efficiently, we make use of a grid structure for storing buildings and users as well as a pruning technique for reducing unnecessary computation. Finally, we show from our performance analysis that our cloaking algorithm outperforms the existing grid- based cloaking algorithm, in terms of the size of cloaking regions, their creation time and query processing time based on them. 1. Introduction In Location-Based Services (LBSs), one of the most important resources is location information, being popular nowadays [1]. A LBS system consists of two main components: i) clients as mobile equipments, like PDA or cellular phones, to request queries and ii) database server to process users’ queries. To support LBSs, such as searching nearest POIs (Point Of Interests) and getting weather information, a mobile user should be equipped with GPS (Geographical Positioning System) to know its location. For this, a mobile user has to send a request (query) with its location to the database server through a wireless network protocol like WiFi. Since the request contains the user's exact location, the location information of the users can be misused by adversaries. Using this information, an adversary can track a user’s personal habit like the place where he/she visits regularly. In the real world, users become victims of stalking due to the unauthorized access of personal information [2]. There existed a little research on cloaking algorithms to protect the privacy in LBS system. We can define a cloaking algorithm in such a way that, for a given user's request, the algorithm generates as small regions to satisfy k-anonymity as possible. In k-anonymity , the generated cloaking region contains a user to request the query along with k-1 other users. However, a cloaking algorithm with k-anonymity has one problem. If the cloaking region is generated for a single building, the behavior of the user can be disclosed easily to adversaries. To protect the privacy, a cloaking algorithm must support not only k- anonymity but also l-diversity . Here, l-diversity means that the cloaking algorithm widens a cloaking region to
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This note was uploaded on 10/19/2009 for the course CNT 5517 taught by Professor Helal during the Fall '09 term at University of Florida.

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A New Grid-Based Cloaking Algorithm for Privacy Protection in Location-Based Services

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