In this paper 1 we discuss the security requirements for mediation, and present our approach towards satisfying them, with an emphasis on confidentiality and authenticity. Furthermore we outline the design of the basic security mechanisms for mediators. Our basic approach suitably combines the concepts of credentials, for authentic authorization with some kind of anonymity, and of asymmetric encryption, for confidentiality, and it can be extended to include additional mechanisms like digital

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... natures and fingerprints. Additionally it adopts the model of role based security policies because of its application orientation and of its potentials to integrate and unify various policies. lThis work was partially supported by the Ministerium fur Wissenschaft und Forschung des Landes Nordrhein-Westfalen within the joint project "Virtuelle Wissensfabrik" (The Virtual Knowledge Factory). S. Jajodia (ed.), Database Security XII