During　data　sharing　process　across　people,　users　do　not　want　the　information　that　contains　privacy　to　be　shared　with　everyone　else;　some　people　may　only　want　to　share　it　with　someone　they　are　familiar　with.　To　solve　this　issue　of　privacy　preservation　in　data-sharing　applications,　we　propose　a　novel　user-centric　method.　Our　main　contributions　include　the　followings.　(1)　Users　can　select　key　words　or　characters　for　their　own　privacy　information,　which　is　a　user-centric　way　to　protect　privacy.　(2)　During　the　process　of　data　sharing,　data　substitution　can　be　used　to　ensure　privacy　preservation　as　well　as　high　successful　rate　of　data　sharing.　(3)　Our　method　can　be　used　in　different　data-sharing　applications　in　a　flexible　way.　Simulation　results　show　that　our　method　can　achieve　our　privacy　preservation　goal.　©　2010　Springer-Verlag.