关键词:  社交网络, 基于位置的服务, 数据隐私, 位置隐私保护, 协同定位隐私攻击 

Abstract:  Information with location tags and friends labels shared by users in location-based mobile social networks，can reveal not only the user’s location but also the friend’s location，and thus lead to the location privacy loss problem based on the colocation information attack． In order to prevent the colocation privacy attack，a location privacy protection method was proposed． A relation strength calculation algorithm based on the online interaction between users and friends was designed，a mapping and quantitative method for the location privacy protection requirement was put forward，and an algorithm based on colocation information concealment and time adjustment called CCTA was explored． Experimental results on the twitter data set indicate that the proposed method has better performance and could be suitable for colocation privacy protection． 

Key words: social networks, location based services, data privacy, location privacy protection, colocation privacy attack