Privacy-Preserving Filtering and Covering in Content-Based Publish Subscribe Systems

Content-Based Publish-Subscribe (CBPS) is an asynchronou s messaging paradigm that supports a highly dynamic and many-to-many communication pattern ba sed on the content of the messages themselves. In general, a CBPS system has three distinct par ties -Content Publishers, Content Brokers , andSubscribersworking in a highly decoupled fashion. The ability to seaml essly scale on demand has made CBPS systems the choice of distributing messages/documents produced byContent Publishersto many SubscribersthroughContent Brokers . Most of the current systems assume that Content Brokers are trusted for the confidentiality of the data published by Content Publishersand the privacy of the subscriptions, which specify their interests, made by Subscribers . However, with the increased use of technologies, such as service oriented architectures and c lou omputing, essentially outsourcing the broker functionality to third-party providers, one can no l onger assume the trust relationship to hold. The problem of providing privacy/confidentiality in CBPS syste ms is challenging, since the solution to the problem should allowContent Brokersto make routing decisions based on the content without revea ling the content to them. The problem may appear unsolvable since it involves conflicting goals, but in this paper, we propose a novel approach to preserve the privacy of the subscriptions made by Subscribers and confidentiality of the data published by Content Publishersusing cryptographic techniques when third-partyContent Brokersare utilized to make routing decisions based on the content. We analyze the security of our approach to show that it is indeed sound and pr ovide experimental results to show that it is practical.