This document proposes a protocol for trilateral authentication in ad-hoc networks using multicast conventions. It introduces a central authority that manages key authentication and certification to increase security and reliability. Nodes are grouped into clusters, each with a cluster head. For similar clusters, authentication uses time asymmetry based on TESLA. For cross-cluster traffic, it uses secret information asymmetry where the source sends packets to cluster heads, which relay to members. Evaluation shows the central authority uses less memory than previous methods and the protocol has higher efficiency.