Trusted content-based publish/subscribe trees

Publish/Subscribe systems hold strong assumptions of the expected behaviour of clients and routers, as it is assumed they all abide by the matching and routing protocols. Assumptions of implicit trust between the components of the publish/subscribe infrastructure are acceptable where the underlying event distribution service is under the control of a single or multiple co-operating administrative entities and contracts between clients and these authorities exist, however there are application contexts where these presumptions do not hold. In such environments, such as ad hoc networks, there is the possibility of selfish and malicious behaviour that can lead to disruption of the routing and matching algorithms. The most commonly researched approach to security in publish/subscribe systems is role-based access control (RBAC). RBAC is suitable for ensuring confidentiality, but due to the assumption of strong identities associated with well defined roles and the absence of monitoring systems to allow for adaptable policies in response to the changing behaviour of clients, it is not appropriate for environments where: identities can not be assigned to roles in the absence of a trusted administrative entity; long-lived identities of entities do not exist; and where the threat model consists of highly adaptable malicious and selfish entities. Motivated by recent work in the application of trust and reputation to Peer-to-Peer networks, where past behaviour is used to generate trust opinions that inform future transactions, we propose an approach where the publish/subscribe infrastructure is constructed and re-configured with respect to the trust preferences of clients and routers. In this thesis, we show how Publish/Subscribe trees (PSTs) can be constructed with respect to the trust preferences of publishers and subscribers, and the overhead costs of event dissemination. Using social welfare theory, it is shown that individual trust preferences over clients and routers, which are informed by a variety of trust sources, can be aggregated to give a social preference over the set of feasible PSTs. By combining this and the existing work on PST overheads, the Maximum Trust PST with Overhead Budget problem is defined and is shown to be in NP-complete. An exhaustive search algorithm is proposed that is shown to be suitable only for very small problem sizes. To improve scalability, a faster tabu search algorithm is presented, which is shown to scale to larger problem instances and gives good approximations of the optimal solutions. The research contributions of this work are: the use of social welfare theory to provide a mechanism to establish the trustworthiness of PSTs; the finding that individual trust is not interpersonal comparable as is considered to be the case in much of the trust literature; the Maximum Trust PST with Overhead Budget problem; and algorithms to solve this problem

The fans united will always be connected: building a practical DTN in a football stadium

Football stadia present a difficult environment for the deployment of digital services, due to their architectural design and the capacity problems from the numbers of fans. We present preliminary results from deploying an Android app building an ad hoc network amongst the attendees at matches at Brighton and Hove Albion's AMEX stadium, so as to share the available capacity and supply digital services to season ticket holders. We describe the protocol, how we engaged our users in service design so that the app was attractive to use and the problems we encountered in using Android

The state of peer-to-peer network simulators

Networking research often relies on simulation in order to test and evaluate new ideas. An important requirement of this process is that results must be reproducible so that other researchers can replicate, validate and extend existing work. We look at the landscape of simulators for research in peer-to-peer (P2P) networks by conducting a survey of a combined total of over 280 papers from before and after 2007 (the year of the last survey in this area), and comment on the large quantity of research using bespoke, closed-source simulators. We propose a set of criteria that P2P simulators should meet, and poll the P2P research community for their agreement. We aim to drive the community towards performing their experiments on simulators that allow for others to validate their results

Finding trusted publish/subscribe trees

Publish/Subscribe systems assume that clients and brokers abide by the matching and forwarding protocols. Such an assumption implies implicit trust between all components of the system and has led to security issues being largely ignored. As publish/subscribe is increasingly used in applications where implicit trust can not be assumed, an approach is required to mitigate misbehaviour. We propose the construction and reconfiguration of the event forwarding topology, the publish/subscribe tree (PST), with respect to the trust requirements of the clients. The principal contribution of this paper is a trust metric for PSTs, which aggregates each client’s trust evaluation of a PST to give a socially acceptable trust evaluation and allows for the ordering of PSTs. Additionally, we define the PST trust maximisation problem with overhead budget, which is solved by the PST that maximises trust within an overhead budget for a given advertisement. A tabu search based algorithm for this problem is presented and is shown to scale to large problem instances and give good approximations of the optimal solutions

A Survey of Peer-to-Peer Network Simulators

As scientists, our research must be tested and evaluated in order for it to be shown to be valid. Part of this process includes providing reproducible results so that peers are able to confirm any findings. The techniques used to achieve this include analytical solutions, simulators and experiments with the actual system, however in the area of Peer-to-Peer (P2P) computing, this gives rise to a number of challenges. In this paper, we focus on P2P simulators by surveying a number of P2P simulators with respect to important criteria when simulating a P2P system. Simulators are compared, usage experiences are given and limitations are discussed. The survey shows that while there are a plethora of simulators, there are many issues such as poor scalability, little or no documentation, steep learning curves, and system limitations that makes using these simulators a convoluted process

building a practical DTN

fans united will always be connected

Towards Yet Another Peer-to-Peer Simulator

There are a number of P2P overlay simulators developed by various research groups for use by the P2P academic community, however many still opt to use their own custom-built simulator. Having surveyed the area of Peer-to-Peer simulators in previous work, we believe that this is due to the simulators lacking key functionality such as mechanisms to gather statistical data from simulation runs. The use of custom built simulators gives rise to a number of problems that include an increase in the difficulty to reproduce and validate results and comparison of similar simulated systems and their associated results. In this paper, we discuss the current situation with respect to simulation usage in P2P research and our work towards creating a new simulator that will meet the requirements of P2P researchers. It is our hope that this paper will give rise to further discussion and knowledge sharing among those of the P2P and simulation research communities, so that a simulator that meets the needs of the P2P community can be developed

Towards Yet Another Peer-to-Peer Simulator

There are a number of P2P overlay simulators developed by various research groups for use by the P2P academic community, however many still opt to use their own custom-built simulator. Having surveyed the area of Peer-to-Peer simulators in previous work, we believe that this is due to the simulators lacking key functionality such as mechanisms to gather statistical data from simulation runs. The use of custom built simulators gives rise to a number of problems that include an increase in the difficulty to reproduce and validate results and comparison of similar simulated systems and their associated results. In this paper, we discuss the current situation with respect to simulation usage in P2P research and our work towards creating a new simulator that will meet the requirements of P2P researchers. It is our hope that this paper will give rise to further discussion and knowledge sharing among those of the P2P and simulation research communities, so that a simulator that meets the needs of the P2P community can be developed