Abstract
Publish/subscribe is an effective paradigm for event dissemination over wide-area systems. However, there is tension between the convenience of open information delivery, and the need to protect data from unauthorised access. Publish/subscribe security models tend to focus on protecting the client API, or encrypting events and managing disclosure through key distribution. However, some application environments require more stringent, fine-grained controls governing precisely the data disclosed and transmitted given particular circumstances. In this paper, we present Interaction Control, a policy model that overlays context-aware, point-to point (hop-level) controls onto a publish/subscribe network. The approach is unique as it allows granular control over i) the construction of the dissemination network, and ii) the information flows within the network. Interaction Control was designed considering legal obligations, to enable those responsible for information to transmit data on a need-to-know basis. Security policies set the bounds for communication, enforced only where necessary at specific points of the publish/subscribe process, to provide control while retaining the efficiency benefits of the paradigm. We present implementation details and results showing that any security overheads must be considered with respect to the overall network load.