Hierarchical wireless sensor networks (WSNs) have been shown to improve system performance, reduce messages redundancy, and economize energy. However, due to the characteristics of WSN, such as restricted resources and operation in a hostile environment, WSNs are subjected to numerous threats and are vulnerable to attacks. In this paper, we present a rekey-boosted security protocol in LEACH (RBS-LEACH) to enhance network security and survivability. Compared to other LEACH security solutions, the salient advantage of this work is that a unique rekey mechanism, which can efficiently protect the network against attacks of eavesdropping or captured nodes compromise, is adopted to address challenging security issues of runtime WSN. Even if the adversaries crack WSN keys, the entire network still remains safe under the timely protection of the rekey mechanism.