Artificial societies -distributed systems of autonomous agents -are becoming increasingly important in e-commerce. Agents base their decisions on trust and reputation in ways analogous to human societies. Many different definitions for trust and reputation have been proposed that incorporate many sources of information; however, system designs have tended to focus much of their attention on direct interactions. Furthermore, trust updating schemes for direct interactions have tended to uncouple

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... pdates for positive and negative feedback. Consequently, behaviour in which cycles of positive feedback followed by a single negative feedback results in untrustworthy agents remaining undetected. This con-man style of behaviour is formally described and desirable characteristics of con-resistant trust schemes proposed. A conresistant scheme is proposed and compared with FIRE, Regret and Yu and Singh's model [Yu and Singh, 2000]. Simulation experiments demonstrate the utility of the con-resistant scheme.