Accompanied　with　accelerated　development　of　the　Internet　of　Things　(IoT)　and　smart　home　industry,　smart　access　control　systems,　e.g.　smart　locks,　are　getting　popular　in　recent　years.　In　this　paper,　we　propose　a　smart　access　control　system　that　allows　users　to　enter　buildings　via　mobile　phones.　Also,　a　protocol　is　designed　to　secure　communications　in　the　system.　In　addition,　some　investigation　results　regarding　security　and　usability　are　found:　(1)　most　people　pay　more　attention　to　security　in　the　access　control　system;　(2)　most　people　prefer　using　fingerprint　as　the　primary　unlocking　mechanism.　©　2016　EAI.