Secure mediation with mobile code

Abstract. A mediator helps a client of a distributed information sys-tem to acquire data without contacting each datasource. We show how mobile code can be used to ensure condentiality of data in a secure mediation system. We analyze what advantages mobile code has over mobile data for secure mediation. We present a Java implementation of a system that mediates SQL queries. Security risks for the client and the mobile code are delineated; oending the integrity of its own data is identied as a special type of attack of mobile code in a mediation system. We name appropriate countermeasures and describe the amount of trust needed in our system. As an extension, we consider security in a hierarchy of mediators. Finally, we combine mobile code with mobile agent technology.