In Wireless sensor networks (WSNs), key management is the core issue of any security approaches. The main challenge in WSNs key management is how to distribute and manage secret keys within WSN nodes. Several schemes are proposed for this purpose. Another challenge which was not tackled by most of the proposed schemes is the behavior of network in case of nodes capturing, since once any node is captured by an adversary, all the information stored in its memory could be compromised. In this paper we propose a key management scheme for hierarchical WSNs. In addition; we propose a mechanism concerning adding of new sensor nodes, and keys revocation and re-keying processes to overcome nodes
capturing crisis. Then we will evaluate the secrecy of our scheme by analyzing the security properties of our proposed scheme with other previous proposed schemes.