prevention procedure in network sharing and bootstrapping nodal with the structure of SBK and improved version - proposed an improved version to speed up the bootstrapping procedure. Improved version retains all the nice features of SBK. SBK and Improved version are truly in situ schemes for bootstrapping keys in sensor networks that place no special requirement on regular sensors.-prevention procedure in network sharing and bootstrapping nodal with the structure of SBK and improved version - proposed an improved version to speed up the bootstrapping procedure.　Improved version retains all the nice features of SBK. SBK and Improved version are truly in situ schemes for bootstrapping keys in sensor networks that place no special requirement on regular sensors.