Protecting Users’ Privacy In Continuous Query Location Based Service

In recent years, location based services(LBS) have become extremely popular with the wide spread use of smart mobile devices. LBS are widely recognized as important because of the services it provide to make life comfortable. Although LBS promise safety and convenience, they threaten the privacy and security of their users. The threat results from the disclosure of users’ location for service which unfortunately are abused by service providers. Current privacy protection algorithms focus on spatial cloaking based on k-anonymity to protect users’ privacy. However, these algorithms are vulnerable to attack when subjected to continuous query and road network environment. In this dissertation,four novel algorithms that protect privacy in a continuous query location based services in two dimensional Euclidean space set-up and road network environment are presented.The first algorithm is a Direction Speed Dynamic Cloaking Algorithm(DSDCA)for privacy preservation of clients in continuous query LBS in Euclidean space, that optimizes the balance between continuous privacy preservation, quality of service and system performance. The DSDCA considers users with similar direction, similar speed, and travelling with the same transport mode for cloaking. Experimental evaluation shows that the DSDCA effectively protected privacy of mobile clients. It also enhance quality of service, attain an excellent performance measure, and exhibit a good success rate during the entire period of continuously querying LBS.The second is a Query Privacy Preserving Algorithm for continuous query road network services that protects the privacy of a client whose home address is known to a malicious service provider. It employs an offline trajectory clustering algorithm to obtain a forecast of traffic and users group characteristics on road network to enhance cloaking.Experimental evaluation shows this algorithm is efficient for privacy protection of mobile clients. It also exhibits an excellent quality of service in a very good performance time,and attain a good success rate within the entire period of continuously querying road network services.The third is an Absolute Privacy Preserving Algorithm which protects clients’ absolute privacy(query privacy, location privacy and semantic location privacy) for continuous query road network services. An offine trajectory clustering algorithm and semantic location graph was employed to aid the selection of cloaked users that will effectively protect the absolute privacy of a client. Experimental evaluation shows this algorithm is efficient for absolute privacy protection with an excellent anonymization success rate in a very good query processing time for the entire period of continuously querying road network services.The forth is a Road Network Service Provider(RSP) Friendly Privacy Preserving Algorithm, which offers privacy protection and satisfaction to clients querying continuous road network services whiles protecting the RSP from dummy attacks. Realistic dummies are generated according to the regular moving trend of users on road network at different locations and different times employing a trajectory clustering algorithm. To protect the RSP from dummy attack, a privacy preserving verification protocol is developed to check the activities of clients in a privacy preserving manner. Experimental evaluation shows this algorithm is efficient for privacy protection, satisfies clients at all times in an excellent time and at a reasonable cost when continuously querying road network services.In effect, all four algorithms protect the privacy of users during the entire period of continuous query location based services.