Advances in communication and electronics have enabled the development of low cost low power, multi functional sensor nodes that can be used in many different applications like environmental monitoring, military sensing, healthcare etc. TinySec is a link layer security architecture suitable for nodes where resource limitations severe. In this paper we are proposing an energy efficient security provisioning scheme for TinySec. The existing TinySec protocol for wireless sensor network is static in nature which adds an additional overhead with increasing latency, energy consumption and decreases the lifetime of the sensor network. To minimize the security cost the proposed scheme adapts the security strength to the sensitivity of the data there by bringing the benefits in resource provisioning as opposed to static configuration which are existing in literature.