The secure transmission of messages via computer networks is, in many scenarios, considered to be a solved problem. However, a related problem, being almost as crucial, has been widely ignored: To whom to entrust information? We argue that confidentiality modeling is a question of trust. Therefore, the article at hand addresses this problem based on a reputation system. We consider a Peer-to-Peer network whose participants decide on whether or not to make information available to other nodes based on the author's trust relationships. Documents are only forwarded to another node if, according to the sender's local view, the recipient is considered to be sufficiently trustworthy. In contrast to most existing reputation systems, trust relationships are considered only with respect to a specific domain. Privacy is preserved by limiting the revelation of trust relationships.