I. Introduction
In wireless sensor networks, the research on routing protocols is very important. But now most of routing protocols take network lifetime and energy consumption into account, none of which has been designed with security as a goal [1]. So we should pay more attention to routing security in the future. However, the resources of nodes are so limited that traditional safe routing algorithms can't be applied to WSNs directly. And routing security and networks lifetime are seemed to be incompatible. Because clustering algorithms of routing protocols can save energy, prolong the lifetime of the network and are more suitable for the large-scale deployment of the network. Therefore, the clustering algorithms are the research hotspots.