Master of Science / Department of Computing and Information Sciences / John Hatcliff / With the increase in development of safety and security critical systems, it is important to have more sophisticated methods for engineering such systems. It can be difficult to understand and verify critical properties of these systems because of their ever growing size and complexity. Even a small error in a complex system may result in casualty or significant monetary loss. Consequently, there is a rise in the demand for scalable and accurate techniques to enable faster development and verification of high assurance systems. This thesis focuses on discovering dependencies between various parts of a system and leveraging that knowledge to infer information flow properties and to verify security policies specified for the system. The primary contribution of this thesis is a technique to build dependence graphs for languages which feature abstraction and refinement. Inter-procedural slicing and inter-procedural chopping are the techniques used to analyze the properties of the system statically. The approach outlined in this thesis provides a domain-specific language to query the information flow properties and to specify security policies for a critical system. The spec- ified policies can then be verified using existing static analysis techniques. All the above contributions are integrated with a development environment used to develop the critical system. The resulting software development tool helps programmers develop, infer, and verify safety and security systems in a single unified environment.

Doctor of Philosophy / Department of Computing Science / David Gustafson / The web is no longer composed of static resources. Technology and demand have driven the web towards a complex, dynamic model that tailors content toward specific client fingerprints. Servers now commonly modify responses based on the browser, operating system, or location of the connecting client. While this information may be used for legitimate purposes, malicious adversaries can also use this information to deliver misinformation or tailored exploits. Currently, there are no tools that allow a user to detect when a response contains tailored content. Developing an easily configurable multiplexing system solved the problem of detecting tailored web content. In this solution, a custom proxy receives the initial request from a client, duplicating and modifying it in many ways to change the browser, operating system, and location-based client fingerprint. All of the requests with various client fingerprints are simultaneously sent to the server. As the responses are received back at the proxy, they are aggregated and analyzed against the original response. The results of the analysis are then sent to the user along with the original response. This process allowed the proxy to detect tailored content that was previously undetectable through casual browsing. Theoretical and empirical analysis was performed to ensure the multiplexing proxy detected tailored content at an acceptable false alarm rate. Additionally, the tool was analyzed for its ability to provide utility to open source analysts, cyber analysts, and reverse engineers. The results showed that the proxy is an essential, scalable tool that provides capabilities that were not previously available.

Master of Science / Department of Computing and Information Sciences / Doina Caragea / Over the last decade, the Internet has become an involving medium and user-generated content is continuously growing. Recommender systems that exploit user feedback are widely used in e-commerce and quite necessary for business enhancement. To make use of such user feedback, we propose a new content/collaborative hybrid approach, which is built on top of the recently released hetrec2011-movielens-2k dataset and is an extension of a previously proposed approach, called Weighted Tag Recommender (WTR). The WTR approach makes use of tag information available in hetrec2011-movielens-2k, but it does not use explicit ratings. As opposed to WTR, our modified approach can make use of ratings to capture collaborative filtering and either user-tags, available in the hetrec2011-movielens-2k, or movie keywords retrieved from IMDB, to capture movie content information. We call the two versions of our approach Weighted Tag Rating Recommender (WTRR) and Weighted Keyword Rating Recommender (WKRR), respectively. Movie keywords (which are not user specific) allow us to use all ratings available in hetrec2011-movielens-2k, as WKKR associates the content information from movies with the users, based on their ratings. On the other hand, tags provide more specific information for a user, but limit the usage of the data to the user-movie pairs that have tags (significantly smaller number compared with all pairs that have ratings). Both our keyword and tag representations of users can help alleviate the noise and semantic ambiguity problems inherent in information contributed by users of social networks. Experiments using the WTRR approach on a subset of the dataset (which contains both ratings and tags) show that it slightly outperforms the WKRR approach. However, WKRR can be applied to the whole hetrec2011-movielens-2k dataset and results show that the information from keywords can help build a movie recommender system competitive with other neighborhood based approaches and even with more sophisticated state-of-the-art approaches.

Master of Science / Department of Computing and Information Sciences / Daniel Andresen / The aim of this project is to develop an Android application for managing and organizing daily activities. Mobile application development is a growing trend in computer industry. Lot of desktop applications is [i.e. are] now becoming available as mobile applications with increasing demand in market. Android is one of the most popular platforms in mobile technology and gives lot of space for creative development as it is open source. There are various discussion forums and official Android development support websites that encourages mobile and tablet application development. The Quick Organizer application provides three main features for managing and organizing everyday tasks. 1. Calendar with smooth navigation buttons and flexible layout to view all calendar events. This calendar synchronizes with Google calendar and calendar application in Android device and allows user to create events in all the user calendar accounts. 2. Notes management for creating new note, viewing all notes for current month and search notes for the user account that synchronizes with the Ever Notes application. 3. Tasks management to create daily to-do lists with deadline for every task. The user can see all the tasks created with clear demarcation between complete and incomplete tasks with help of strike-out tasks when completed.

Master of Science / Department of Computing and Information Sciences / Daniel A. Andresen / Recently, the world has been trending toward the use of Smartphone. Today, almost each and every individual is using Smartphone for various purposes benefited by the availability of large number of applications. The memory on the SD (Secure Digital) memory card is going to be a constraint for the usage of the Smartphone for the user. Memory is used for storing large amounts of data, which include various files and important document. Besides having many applications to fill the free space, we hardly have an application that manages the free memory according to the user’s choice. In order to manage the free space on the SD card, we need an application to be developed. All the important files stored on the Android device cannot be retrieved if we lose the Android device. Targeting the problem of handling the memory issues, we developed an application that can be used to provide the security to the important documents and also store unnecessary files on the distributed file servers and retrieve them back on request.

Doctor of Philosophy / Department of Computing and Information Sciences / Scott A. DeLoach / There is a growing demand for more effective integration of humans and computing systems, specifically in multiagent and multirobot systems. There are two aspects to consider in human integration: (1) the ability to control an arbitrary number of robots (particularly heterogeneous robots) and (2) integrating humans as peers in computing systems instead of being just users or supervisors. With traditional supervisory control of multirobot systems, the number of robots that a human can manage effectively is between four and six [17]. A limitation of traditional supervisory control is that the human must interact individually with each robot, which limits the upper-bound on the number of robots that a human can control effectively. In this work, I define the concept of "organizational control" together with an autonomous mechanism that can perform task allocation and other low-level housekeeping duties, which significantly reduces the need for the human to interact with individual robots. Humans are very versatile and robust in the types of tasks they can accomplish. However, failures in computing systems are common and thus redundancies are included to mitigate the chance of failure. When all redundancies have failed, system failure will occur and the computing system will be unable to accomplish its tasks. One way to further reduce the chance of a system failure is to integrate humans as peer "agents" in the computing system. As part of the system, humans can be assigned tasks that would have been impossible to complete due to failures.

Combinatorial optimisation problems (COPs) pervade human society: scheduling, design, layout, distribution, timetabling, resource allocation and project management all feature problems where the solution is some combination of elements, the overall value of which needs to be either maximised or minimised (i.e., optimised), typically subject to a number of constraints. Thus, techniques to efficiently solve such problems are an important area of research. A popular group of optimisation algorithms are the metaheuristics, approaches that specify how to search the space of solutions in a problem independent way so that high quality solutions are likely to result in a reasonable amount of computational time. Although metaheuristic algorithms are specified in a problem independent manner, they must be tailored to suit each particular problem to which they are applied. This thesis investigates a number of aspects of the application of the relatively new Ant Colony Optimisation (ACO) metaheuristic to different COPs.The standard ACO metaheuristic is a constructive algorithm loosely based on the foraging behaviour of ant colonies, which are able to find the shortest path to a food source by indirect communication through pheromones. ACO’s artificial pheromone represents a model of the solution components that its artificial ants use to construct solutions. Developing an appropriate pheromone representation is a key aspect of the application of ACO to a problem. An examination of existing ACO applications and the constructive approach more generally reveals how the metaheuristic can be applied more systematically across a range of COPs. The two main issues addressed in this thesis are biases inherent in the constructive process and the systematic selection of pheromone representations.The systematisation of ACO should lead to more consistently high performance of the algorithm across different problems. Additionally, it supports the creation of a generalised ACO system, capable of adapting itself to suit many different combinatorial problems without the need for manual intervention.

The IP Multimedia Subsystem (IMS) is the technology that will merge the Internet (packet switching) with the cellular world (circuit switching). It will make Internet technologies, such as the web, email, instant messaging, presence, and videoconferencing available nearly everywhere. Presence is one of the basic services that is likely to become omnipresent in IMS. It is the service that allows a user to be informed about the reachability, availability, and willingness of communication of another user. Push to talk over Cellular (PoC) is another service in IMS that is intended to provide rapid communications for business and consumer customers of mobile networks. In order to become a truly successful mass-market service for the consumer segment, the only realistic alternative is a standardized Push-to-talk solution providing full interoperability between terminals and operators. Instant Messaging (IM) is the service that allows an IMS user to send some content to another user in near real-time. This service works under IETF’s Message Session Relay protocol (MSRP) to overcome the congestion control problem. We believe the efficiency of these services along with the mobility management in IMS session establishment has not been sufficiently investigated.In this research work, we identify the key issues to improve the existing protocols in IMS for better system behaviour. The work is centred on the three services of IMS: (1) Presence Service, (2) Push-to-Talk over cellular and, (3) Instant Messaging and over the issue of (4) IMS session set up. The existing session establishment scenario of IP Multimedia Subsystem (IMS) suffers from triangular routing for a certain period of time when an end IMS user or terminal is mobile. In this thesis, the performance of three possible session establishment scenarios in a mobile environment is compared by using an analytical model. The model is developed based on the expressions of cost functions, which represents system delay and overhead involved in sessions’ establishment. The other problem areas in optimizing presence service, dimensioning a PoC service and analysing service rates of IM relay extensions in IMS are identified. A presence server becomes overloaded when massive number of IMS terminals joins a network to request presence facility. Performance models are developed in this research to mitigate such load during heavy traffic for the presence service. Queuing analyses for different cases are provided while instant messaging chunks go through two consecutive relay nodes. The specific factors such as blocking probability, stability conditions, optimized subscription lifetime etc. in IMS environment parameters have been investigated. We have also elaborated models to dimension a PoC service for service providers with regards to controlling PoC session access, optimal PoC session timer, path optimization and number of allowable simultaneous PoC sessions for given network grade of service.In a nutshell, the contribution of this dissertation are: (a) a proposed robust scheduler to improve performance of the IMS presence service, (b) several derived models to dimension IMS Push-to-talk over cellular service, (c) a new mechanism to reduce cost for the IMS session set ups in mobile environment and (d) evaluation of message blocking and stability in IMS Instant Messaging (IM) service by applying queuing theories. All of these analyses have resulted in recommendations for the performance enhancements with optimal resource utilization in IMS framework.

One of the activities of most successful intruders of a computer system is to modify data on the victim,either to hide his/her presence and to destroy the evidence of the break-in, or to subvert the system completely and make it accessible for further abuse without triggering alarms.File integrity checking is one common method to mitigate the effects of successful intrusions by detecting the changes an intruder makes to files on a computer system. Historically file integrity checking has been implemented using tools that operate locally on a single system, which imposes quite some restrictions regardingmaintenance and scalability. Recent improvements for large scale environments have introduced trusted central servers which provide secure fingerprint storage and logging facilities, but such centralism presents some new shortcomings.This thesis describes an alternative, decentralised approach where peer-to-peer mechanisms are used to provide fingerprint storage for file integrity checking with more flexibility and scalability than offered by currently available systems. A research implementation has been developed to verify the approach as viable and practical, and experimental results obtained with that prototype are discussed.

The primary objective of this research is to use the benefits offered by computerized three dimensional graphics and apply those to the field of human computer interaction. Focussing primarily on the interactive content of the 3D world, this research describes a range of innovative new interface elements demonstrating specific new 3Dinterfaces/components designed to provide a new interactive 3D method for handling a range of particular common real-world tasks (ranging from simple value setting tasks up to larger scale systems for browsing structured sets of hierarchical data). These systems incorporate new design concepts such as active 3D interfaces that present their data to the user rather than statically waiting for the user to interact with them (these systems prove particularly useful in the presentation of large sets of data). Overall this set of components introduces a range of new interface styles that prove very effective in many mainstream real world tasks.In addition to the development of these systems, this project demonstrates a new high level 3D interface development tool designed to simplify the challenge of constructing interactive 3D user interfaces and in doing so make 3D interface development available to a wider developer base. By constructing the components mentioned above in a structured generic form, this combination of a new development tool and a range of re-usable components provide a strong development platform, from which more complex interactive 3D interfaces can be constructed.In essence the core idea that underlies this research is making the construction of interactive and functional 3D interfaces simpler to undertake (by developing effective re-usable components to handle mainstream tasks) while at the same time generating resulting 3D interfaces that are more effective and more capable of providing users with an enjoyable and functional 3D working environment.