In　order　to　study　deeply　key　management　methods　for　node　mobility　scenarios　in　wireless　sensor　networks　and　overcome　security　shortcomings　of　current　key　management　schemes　that　ignore　the　security　of　rejoining　mobile　nodes,　composite　security　mechanisms　based　on　the　elliptic　curve　digital　signature　algorithm　are　proposed　to　help　nodes　in　the　mobility　scenarios　authenticate　their　identities.　Meanwhile,　this　scheme　can　solve　some　security　flaws　in　other　key　management　schemes,　such　as　nodes　are　susceptible　to　DoS(denial　of　service)　attacks　and　keys　are　liable　to　be　inferred.　Using　160bit　ECC(elliptic　curve　cryptosystems),　this　scheme　has　been　implemented　in　Crossbow＇s　IRIS　nodes　with　the　XMTS300CB　sensor　boards,　in　which　nodes　in　the　mobility　scenarios　can　join　the　network　securely　by　establishing　shared　pair　wise　keys　and　local　broadcast　keys　with　new　neighbors.　Security　and　performance　analysis　show　that　this　scheme　can　effectively　prevent　main　attacks　on　wireless　sensor　networks.　Furthermore,　its　computation,　communication　and　storage　overhead　are　low.