abstract: In desert riparian ecosystems, rivers provide free water but access to that water diminishes with distance producing a steep gradient in the relative importance of water for growth and reproduction of riparian animals and hence, their biodiversity. Previous work suggests that water limited riparian predators eat more prey to meet their water demand where free water is not available. Here I explore the effect of water limitation on prey selection and per capita interaction strengths between a predatory spider ( Hogna antelucana) and two prey species occupying different trophic levels using a controlled field experiment conducted in the riparian forest of the San Pedro River, Cochise County, AZ. Lab measurements of water and energy content revealed that intermediate predators (smaller spiders in the genus Pardosa) had 100-fold higher energy: water ratios than an alternate prey species more basal in the food web (crickets in the genus Gryllus). Given this observation, I hypothesized that water-stressed predatory wolf spiders would select more water-laden crickets but switch to more energy rich Pardosa when water stress was experimentally eliminated. Additionally, I hypothesized that switching by quenched Hogna to Pardosa would reduce predation by Pardosa on Gryllus leading to increased abundance of the basal resource. Finally, I hypothesized that water mediated switching and release of basal prey would be stronger when male Hogna was the apex predator, because female Hogna have higher energetic costs of reproduction and hence, stronger energy limitation. Experimental water additions caused both sexes of Hogna to consume significantly higher numbers of Pardosa but this difference (between water and no-water treatments) did not vary significantly between male and female Hogna treatments. Similarly, strong negative interaction strengths between Hogna and Pardosa led to release of the basal prey species and positive interaction strengths of Hogna on Gryllus. Again strong positive, indirect effects of Hogna on Gryllus did not depend on the sex of the Hogna predator. However, water mediated indirect effects of Hogna (either sex) on Gryllus were the strongest for male Gryllus. These results suggest that water and energy co-dominate foraging decisions by predators and that in managing water-energy balance; predators can modify interaction pathways, sex-ratios of prey populations and trophic dynamics. / Dissertation/Thesis / Masters Thesis Biology 2015

Background: String searching within a large corpus of data is a critical component of digital forensic (DF) analysis techniques such as file carving. The continuing increase in capacity of consumer storage devices requires similar improvements to the performance of string searching techniques employed by DF tools used to analyse forensic data. As string searching is a trivially-parallelisable problem, general purpose graphic processing unit (GPGPU) approaches are a natural fit. Currently, only some of the research in employing GPGPU programming has been transferred to the field of DF, of which, a closed-source GPGPU framework was used— Complete Unified Device Architecture (CUDA). Findings from these earlier studies have found that local storage devices from which forensic data are read present an insurmountable performance bottleneck. Aim: This research hypothesises that modern storage devices no longer present a performance bottleneck to the currently used processing techniques of the field, and proposes that an open-standards GPGPU framework solution – Open Computing Language (OpenCL) – would be better suited to accelerate file carving with wider compatibility across an array of modern GPGPU hardware. This research further hypothesises that a modern multi-string searching algorithm may be better adapted to fulfil the requirements of DF investigation. Methods: This research presents a review of existing research and tools used to perform file carving and acknowledges related work within the field. To test the hypothesis, parallel file carving software was created using C# and OpenCL, employing both a traditional string searching algorithm and a modern multi-string searching algorithm to conduct an analysis of forensic data. A set of case studies that demonstrate and evaluate potential benefits of adopting various methods in conducting string searching on forensic data are given. This research concludes with a final case study which evaluates the performance to perform file carving with the best-proposed string searching solution and compares the result with an existing file carving tool— Foremost. Results: The results demonstrated from the research establish that utilising the parallelised OpenCL and Parallel Failureless Aho-Corasick (PFAC) algorithm solution demonstrates significantly greater processing improvements from the use of a single, and multiple, GPUs on modern hardware. In comparison to CPU approaches, GPGPU processing models were observed to minimised the amount of time required to search for greater amounts of patterns. Results also showed that employing PFAC also delivers significant performance increases over the BM algorithm. The method employed to read data from storage devices was also seen to have a significant effect on the time required to perform string searching and file carving. Conclusions: Empirical testing shows that the proposed string searching method is believed to be more efficient than the widely-adopted Boyer-Moore algorithms when applied to string searching and performing file carving. The developed OpenCL GPGPU processing framework was found to be more efficient than CPU counterparts when searching for greater amounts of patterns within data. This research also refutes claims that file carving is solely limited by the performance of the storage device, and presents compelling evidence that performance is bound by the combination of the performance of the storage device and processing technique employed.

Devido Ãs crescentes ameaÃas inerentes aos sistemas de informaÃÃo, o uso de mecanismos de autenticaÃÃo e autorizaÃÃo baseados em identificador de usuÃrio e senha nÃo à mais suficiente para garantir a seguranÃa das informaÃÃes. Este trabalho propÃe um novo modelo de autenticaÃÃo e autorizaÃÃo para controle de acesso de aplicaÃÃes distribuÃdas, baseado em resumos criptogrÃficos e certificados de atributos. Os resumos criptogrÃficos sÃo utilizados no processo de autenticaÃÃo da aplicaÃÃo, enquanto os certificados de atributos especificam privilÃgios e outras informaÃÃes de autorizaÃÃo associadas ao seu proprietÃrio. Os certificados de atributos sÃo gerenciados pela infra-estrutura de gerenciamento de privilÃgios (IGP). A arquitetura e o funcionamento do modelo bem como os processos de geraÃÃo do certificado de atributos, autenticaÃÃo e autorizaÃÃo da aplicaÃÃo sÃo descritos. O modelo proposto foi especificado em Redes de Petri Coloridas e validado por meio de simulaÃÃes. / Due to increasing threats inherent to the information systems, the use of authentication and authorization mechanisms based in login and password does not enough to assure the information security. This work proposes a new model of authentication and authorization for distributed applications, based in hash and attributes certificates. Hash is used in the application authentication process, while certificates of attributes specify privileges and other authorization information. Its use is managed by the privilege management infrastructure (PMI). In this work, we describe the architecture and the functioning of the model, as well the processes of the attributes certificates generation, authentication and authorization of the application. The proposed model was specified in Coloured Petri Nets and validated by simulation.

The Internet traffic is constantly increasing following the emergence of new network applications like social networks, peer-to-peer, IP phone or IP television. In addition, these new applications request better path availability and path quality. Indeed the efficiency of these applications is strongly related to the quality of the underlying network. In that context network operators make use of traffic engineering techniques in order to improve the quality of the routes inside their network, but also to reduce the network cost of increased traffic handling with a better utilization of existing resources. This PhD thesis covers several topics of Traffic Engineering and Fast Restoration in IP/MPLS networks. Our first contribution is related to the definition of a well-engineered network. In the literature mathematical formulation of Traffic Engineering (TE) requirements are very diverse. We have thus performed a comparative study of many objective functions, in order to differentiate them and choose in a rational way the one that best reflects Traffic Engineering goals. We have also designed a method approaching optimal TE, whereby we divide the traffic matrix in N sub-matrices and route them independently, based on the derivatives of the objective function. The second topic addressed in this work concerns link weight optimizers (LWOs). Link weight optimization is the traffic engineering {it "standard"} technique in networks running link state routing protocols (which are widely used in transit networks). These link weight optimizers suffer from several limitations due to the BGP (Border Gateway Protocol) Hot-Potato rule, which is basically not considered by such optimizers. Therefore we have proposed a BGP-aware link weight optimization method that takes problematic Hot-Potato effects into account, and even turns them into an advantage. We have also studied how LWOs behave in big networks which have to use BGP route reflectors. Finally we have studied whether forwarding loops can appear or not when traffic is split among multiple equivalent egress routers, an optional BGP feature that we did use in our Hot-Potato aware LWO. Our last contribution concerns network resilience. We have proposed a solution for a rapid recovery from a link or node failure in an MPLS network. Our solution allows a decentralized deployment combined with a minimal bandwidth usage while requiring only reduced amount of information to flood in the network. This method is the first that makes possible a decentralized deployment combined with an optimal resource consumption. To easily simulate and test the methods proposed in this work, we have also contributed to the development of TOTEM - a TOolbox for Traffic Engineering Methods.