In mobile ad hoc network (MANET) where security is a crucial issue, trust plays an important factor that could improve the number of successful data transmission process. The higher the numbers of nodes that trust each other in the network means higher successful communication process rate could be expected. To determine trust, there are several criteria need to be considered. These criteria can be used to represent each node's trust properties in the trust evaluation process prior to initiating certain packet forwarding task. By introducing a good trust calculation model, we can establish secure route between source and destination without any intruders or malicious nodes. The aim of this book is to emphasis on the use of trust concept to enhance the security by calculating proportion based trust in a global manner. It helps in computing the trust in neighbors and selecting the most secure route from the available ones for the data transfer. In the proposed model, trust is not calculated for any particular situation instead, it is computed based on a summary of behavior of the node for a specific amount of period.