Content-based publish/subscribe has gained high popularity for large-scale dissemination of dynamic information in the form of events from publishers to subscribers in a decoupled fashion. Yet, it is highly challenging to achieve scalability without sacrificing the expressiveness of subscriptions (user queries) in such systems, especially in a peer-to-peer (P2P) environment where subscribers and publishers are also responsible for forwarding events by forming an overlay network. Moreover, the support for non-functional requirements such as quality of service (e.g., end-to-end delay, bandwidth etc.) and security (e.g., authentication, confidentiality etc.) instigate many open research questions. The main advantage of publish/subscribe - its inherent decoupling - turns to be a major obstacle in the fulfillment of non-functional requirements with conventional methods.

Therefore, the goal of this thesis is to develop methods and algorithms that i) enable scalable dissemination of events, ii) support different quality of service aspects, and iii) provide basic security mechanisms, in a P2P content-based publish/subscribe system. In particular, the following contributions are made in this thesis.

As a first contribution, we propose a distributed algorithm to disseminate events in a publish/subscribe system respecting the subscriber-defined QoS constraints in terms of delay requirements and available bandwidth. In addition, the second contribution focuses on minimizing the overall resource usage, i.e., bandwidth consumption and processing load on peers (publishers and subscribers), in a publish/subscribe system. This contribution develops an efficient and scalable method to reduce the rate of events that peers receive and forward though lacking subscription (i.e., false positives) by means of subscription clustering, using the techniques from spectral graph theory.

The first two contributions target overlay-level methods to provide efficient dissemination of events and quality of service. The third contribution, however, proposes underlay-aware methods that explicitly take into account the properties of the underlying physical network and its topology, to construct an efficient publish/subscribe routing overlay with low relative delay penalty and low stress on the physical links. Finally, as our last contribution, we present novel methods to provide authentication of publishers and subscribers as well as confidentiality and integrity of events using the techniques from pairing-based cryptography. Additionally, an algorithm is developed to preserve the weak subscription confidentiality in the presence of interest clustering of subscribers.