Attacking Algorithms Against Continuous Queries in LBS and Anonymity Measurement

k-Anonymity is an important solution to protecting privacy of queries in LBS (location-based service). However, it is pointed out in literatures that k-anonymity cannot protect privacy of continuous queries effectively. A continuous query issuing model is proposed, which incorporates a query issuing interval model and a consecutive queries relationship model. Under this continuous query issuing model, two attacking algorithms are proposed for Clique Cloaking and Non-clique Cloaking respectively. Then this paper argues that the cardinality of anonymity-set is not a good anonymity measurement under such attack and an entropy-based anonymity measurement AD (anonymity degree) is proposed. Experimental results demonstrate that the attacking algorithms have high success rate in identifying query senders when the consecutive queries have strong relationship, and that AD is a better anonymity measurement than the cardinality of anonymity-set.