An ad-hoc network of wireless nodes is a temporarily formed network, created, operated and managed by the nodes themselves. It is also often termed an infrastructure-less, self-organized, or spontaneous network. Nodes assist each other by passing data and control packets from one node to another, often beyond the wireless range of the original sender. The execution and survival of an ad-hoc network is solely dependent upon the cooperative and trusting nature of its nodes. However, this naive dependency on intermediate nodes makes the ad-hoc network vulnerable to passive and active attacks by malicious nodes. A number of protocols have been developed to secure ad-hoc networks using cryptographic schemes, but all rely on the presence of an omnipresent, and often omniscient, trust authority. As this paper describes, dependence on a central trust authority is an impractical requirement for ad-hoc networks. We present a model for trust-based communication in ad-hoc networks that also demonstrates that a central trust authority is a superfluous requirement. The model introduces the notion of belief and provides a dynamic measure of reliability and trustworthiness in an ad hoc network.