Computing and Informatics

The need of trust is growing in several contexts as e-commerce, virtual communities, distributed on-line services and many others as an essential precautionary component for users during interactions with strangers, either other people or virtual agents. Generally trust metrics endorse the principle ``the higher the trust, the more legitimate that user will be''; a consequence is that getting trusted must require some effort, otherwise all participants would easily achieve high trustworthiness. In this work we study how a user can achieve and preserve a good trust and what costs it requires over time; we also investigate some heuristics that allow reducing the complexity in exploring the rank-effort space especially for large networks.