  In this paper, we consider a multi-agent resilient consensus problem, where
some of the nodes may behave maliciously. The approach is to equip all nodes
with a scheme to detect neighboring nodes when they behave in an abnormal
fashion. To this end, the nodes exchange not only their own states but also
information regarding their neighbor nodes. Such two-hop communication has long
been studied in fault-tolerant algorithms in computer science. We propose two
distributed schemes for detection of malicious nodes and resilient consensus
with different requirements on resources for communication and the structures
of the networks. In particular, the detection schemes become effective under
certain connectivity properties in the network so that the non-malicious nodes
can share enough information about their neighbors. It is shown that the
requirements are however less stringent than those for conventional algorithms.
A numerical example is presented to demonstrate the performance of the proposed
methods in wireless sensor networks.
