Summary form only given. Peer-to-peer (P2P) networks are designed with an assumption that the nodes in a P2P network will cooperate each other. In the absence of any common goals shared by the nodes of a P2P network, external motivation to cooperate and be trustworthy is required. Digital reputations can be used to inject trust among the autonomous nodes of a network and motivate the nodes to contribute resources. We summarize a self-certification scheme for the identification of peers using digital certificates similar to SDSI certificates, techniques to mitigate the problem of 'a consortium of liars' and an elicitation-storage protocol for procuring and storing recommendations.