As wireless sensor networks are growing, the need for effective security mechanisms is doing so. In this paper, we propose Energy-Efficient Key Management Protocol, a cryptographic key management protocol, which is based on the location based group key scheme. The protocol supports the revocation of the compromised nodes and the energy-efficient rekeying. The design of the protocol is motivated by the observation that a unicast-based rekeying is not suitable for meeting the security requirements of periodic rekeying in wireless sensor networks. Our protocol supports the broadcast-based rekeying for low-energy key management and high resilience. For increasing complexity of encryption key, we use dynamic composition key scheme. Our protocol provides group management protocols for secure group communication. We analyze the energy efficiency of our protocol comparing with other key management protocols and simulate our protocol and other protocols in a network simulator.