Karabulut, Yücel2004-12-062004-12-062002-09-262002-11-11http://hdl.handle.net/2003/256010.17877/DE290R-7868The thesis is concerned with solutions to challenges associated with secure mediation between strangers in cyberspace. In mediated information system clients and information sources are brought together by mediators. The mediation paradigm needs powerful and expressive security mechanisms considering the dynamics and conflicting interests of mediation participiants. The thesis presents a security framework for mediation with an emphasis on confidentiality and authenticity. It is argued for basing the enforcement of confidentiality and authenticity on certified characterizing properties, such as personal authorization attributes, rather than on identification. In the security framework specification and enforcement of permissions are based on the public-key infrastructures which allow the binding of characterizing properties to public keys.enUniversität Dortmundsecure mediationaccess controlPKIauthorizationcredentialpersonal authorizationdata privacyauthentic authorizationquery processingsecure information system004doctoral thesis