: Security has become the corner stone of research in wireless sensor networks (WSNs). Due to the unique operational environment of WSNs, where the communication medium is open to eavesdroppers, the threats manifest in new forms necessitating the safeguarding of communication. Consequently, key management protocols have become paramount in mitigating the damage caused. Numerous group-key protocols have been proposed in an effort to secure both inter and intra network communication. However, the group-key protocols in literature neither address the issue of the size of a group nor its geographic boundaries. Therefore, in applications like watchdogbased reputation monitoring systems, malicious users are encouraged to pollute the reputation values by bad-mouthing benign nodes and false-praising other collaborating malicious nodes. On the otherhand, though pairwise-key protocols can overcome the above drawback of group-key protocols, they are highly restrictive and impose substantial stora...