Performance/Security Tradeoffs for Content-Based Routing Supported by Bloom

Abstract. Content-based routing is widely used in large-scale distribu-ted systems as it provides a loosely-coupled yet expressive form of com-munication: consumers of information register their interests by the means of subscriptions, which are subsequently used to determine the set of re-cipients of every message published in the system. A major challenge of content-based routing is security. Although some techniques have been proposed to perform matching of encrypted subscriptions against en-crypted messages, their computational cost is very high. To speed up that process, it was recently proposed to embed Bloom filters in both subscriptions and messages to reduce the space of subscriptions that need to be tested. In this article, we provide a comprehensive analy-sis of the information leaked by Bloom filters when implementing such a “prefiltering ” strategy. The main result is that although there is a funda-mental trade-off between prefiltering efficiency and information leakage, it is practically possible to obtain good prefiltering while securing the scheme against leakages with some simple randomization techniques.