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Recently, candidate constructions were given for indistinguishability obfuscation by Garg, Gentry, Halevi, Raykova, Sahai, and Waters [FOCS'13]. The goal of general-purpose program obfuscation is to make an arbitrary computer program ``unintelligible'' while preserving its functionality. Since then, this new tool has been used to obtain many new applications. In this dissertation, we study the problem of protecting software against new and powerful adversary structures as well as optimize the efficiency of secure general-purpose obfuscation schemes.In the first part of this dissertation, we initiate the study of hosting services on an untrusted cloud. Specifically, we consider a scenario where a service provider has created a software service S and desires to outsource the execution of this service to an untrusted cloud. The software service contains secrets that the provider would like to keep hidden from the cloud. For example, the software might contain a secret database, and the service could allowusers to make queries to different slices of this database depending on the user's identity. Furthermore, we seek to protect knowledge of the software S to the maximum extent possible even if the cloud can collude with several corrupted users. We provide the first formalizations of security for this setting, and construction relying on indistinguishabilityobfuscation.The great interest in the utility of obfuscation leads to a natural and pressing goal: to improve the efficiency of general-purpose obfuscation. In the second part of this dissertation, we initiate the work to optimize the efficiency of secure general-purpose obfuscation schemes.We focus on the problem of optimizing the obfuscation of Boolean formulas and branchingprograms - this corresponds to optimizing the ``core obfuscator'' from the work of Garg \etal, and all subsequent works constructing general-purpose obfuscators. Our efficiency improvement is obtained by generalizing the class of branching programs that can be directly obfuscated. This generalization allows us to achieve a simple simulation of formulas by branching programs while avoiding the use of Barrington's theorem, on which all previous constructions relied. Furthermore, the ability to directly obfuscate general branching programs (without bootstrapping) allows us to efficiently apply our construction to naturalfunction classes that are not known to have polynomial-size formulas.

This study examines factors that influence communities to organize themselves to successfully govern common pool resources (CPR). Commons scholarship has long sought to identify the most important factors within CPR management schemes. There is a consensus that monitoring and sanctioning may be necessary factors that promote successful and sustained natural resource governance. Despite this growing consensus, less is known about the causal mechanisms of monitoring and sanctioning and the factors that influence its levels. More specifically, less is known regarding how monitoring and sanctioning is structured, how it is carried out, who is involved and in what capacity. Further research is needed to explore the challenges and factors that promote cooperation in the collective action process and self-governance of CPR management. Pure self-governance may not be a reality in most community-oriented efforts, as external factors might have some influence. Hence, it is crucial to also identify the roles that all actors involved play and how roles impact natural resource governance. This dissertation sheds light on these important issues by first focusing on how monitoring and sanctioning is structured and who is involved and in what capacity. The dissertation delves into the details of various challenges that are related and explores how communities overcome those challenges. Finally, the dissertation shifts focus from community action to the collaborative role that external actors play in determining goals, strategies, and outcomes in natural resource governance. A multiple case study method was adopted to address these issues. Van Panchayats, a traditional local institution that has been involved in natural resource governance for more than eight decades, were chosen for this study. They form one of the earliest examples of decentralized resource management through formal state community partnerships. These van panchayats operate in diverse partnerships with government agencies and non-government organizations. Twelve cases of van panchayats with diverse institutional configuration were identified and selected for dissertation research. The dissertation helps in understanding institutional factors, different sets of rules, and partnerships that affect collaborative natural resource governance. It highlights the importance of identifying diverse collaborative partnerships in which community-based institutions operate and how these might be helpful in explaining why some groups govern their resources more effectively than others. The results show that although government plays a key role in formulating rules, in practice both government and van panchayat formulated rules and actions are interdependent. Dissertation results highlight the biggest challenges to effective monitoring and sanctioning and factors that motivate communities to overcome these challenges.

Mesh networks is a class of wireless networks consisting of a set of backbone nodes and some client nodes. In this work, we look at the problems of routing, scheduling and power control in such networks, with the ultimate goal of increasing the throughput while satisfying all the traffic requirements. Increasing the throughput of the network implies the ability to send more data between as many source and destination nodes as possible, in shorter periods of time. To achieve this, we need intelligent scheduling schemes that take advantage of the spatial reuse that is possible. We outline two heuristic scheduling algorithms that look at various ways of ordering the links and choosing the ones that might reduce the schedule length, which is a measure of the throughput of the network. The simpler algorithm works at the candidate node level for each slot, while the more complex independent sets based algorithm works with individual links. Different options have been outlined for choosing the first and subsequent links of every slot in the schedule. This includes the interference score of the link, the magnitude of traffic requirement, the specific interfering links, etc. We also study in detail how the links in the network affect the schedule length. When certain links are scheduled, the spatial reuse factor is reduced to zero, implying that no other links can be active at the same time as these links. Hence it is of interest to us to study more about these "loner" links as they add to the schedule length. We characterize these links for topologies in square and circular areas. Using simple geometric arguments, we show that links of length 0.579k and 0.485d in a square area of side k and circular area of diameter d respectively, will always be loners. We also outline a method to analytically find the number of loner links in a given network. This number gives a lower bound on the schedule length. With the understanding gained from the study of scheduling heuristics, we present a routing algorithm that performs topology control by removing loner links. The traffic on these links is routed using other links in the network. Although this routing scheme does not perform well, it leads to a more intelligent joint routing and scheduling mechanism that succeeds in reducing schedule lengths. The joint mechanism does routing in parallel with 2 the scheduling, by calculating routes over links that fit completely into the current schedule. The power control mechanism for both these schemes is to use the minimum power level needed for communication.

Augmented reality provides its user with additional information not available through the natural real-world environment. This additional information displayed to the user potentially poses a risk of perceptual and cognitive load and vision-based difficulties. The presence of real-world objects together with virtual augmenting information requires the user to repeatedly switch eye focus between the two in order to extract information from both environments. Switching eye focus may result in additional time on user tasks and lower task accuracy. Thus, one of the goals of this research was to understand the impact of switching eye focus between real-world and virtual information on user task performance. Secondly, focus depth, which is an important parameter and a depth cue, may affect the user's view of the augmented world. If focus depth is not adjusted properly, it may result in vision-based difficulties and reduce speed, accuracy, and comfort while using an augmented reality display. Thus, the second goal of this thesis was to study the effect of focus depth on task performance in augmented reality systems. In augmented reality environments, real-world and virtual information are found at different distances from the user. To focus at different depths, the user's eye needs to accommodate and converge, which may strain the eye and degrade performance on tasks. However, no research in augmented reality has explored this issue. Hence, the third goal of this thesis was to determine if distance of virtual information from the user impacts task performance. To accomplish these goals, a 3x3x3 within subjects design was used. The experimental task for the study required the user to repeatedly switch eye focus between the virtual text and real-world text. A monocular see-through head- mounted display was used for this research. Results of this study revealed that switching between real-world and virtual information in augmented reality is extremely difficult when information is displayed at optical infinity. Virtual information displayed at optical infinity may be unsuitable for tasks of the nature used in this research. There was no impact of focus depth on user task performance and hence it is preliminarily recommended that manufacturers of head-mounted displays may only need to make fixed focus depth displays; this clearly merits additional intensive research. Further, user task performance was better when focus depth, virtual information, and real-world information were all at the same distance from the user as compared to conditions when they were mismatched. Based on this result we recommend presenting virtual information at the same distance as real-world information of interest.