Mobile　health　(mHealth)　has　emerged　as　a　new　patient　centric　model　which　allows　real-time　collection　of　patient　data　via　wearable　sensors,　aggregation　and　encryption　of　these　data　at　mobile　devices,　and　then　uploading　the　encrypted　data　to　the　cloud　for　storage　and　access　by　healthcare　staff　and　researchers.　However,　efficient　and　scalable　sharing　of　encrypted　data　has　been　a　very　challenging　problem.　In　this　paper,　we　propose　a　Lightweight　Sharable　and　Traceable　(LiST)　secure　mobile　health　system　in　which　patient　data　are　encrypted　end-to-end　from　a　patient＇s　mobile　device　to　data　users.　LiST　enables　efficient　keyword　search　and　fine-grained　access　control　of　encrypted　data,　supports　tracing　of　traitors　who　sell　their　search　and　access　privileges　for　monetary　gain,　and　allows　on-demand　user　revocation.　LiST　is　lightweight　in　the　sense　that　it　offloads　most　of　the　heavy　cryptographic　computations　to　the　cloud　while　only　lightweight　operations　are　performed　at　the　end　user　devices.　We　formally　define　the　security　of　LiST　and　prove　that　it　is　secure　without　random　oracle.　We　also　conduct　extensive　experiments　to　access　the　system＇s　performance.　©　2004-2012　IEEE.