10,597 research outputs found

    Countermeasures for the majority attack in blockchain distributed systems

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    La tecnología Blockchain es considerada como uno de los paradigmas informáticos más importantes posterior al Internet; en función a sus características únicas que la hacen ideal para registrar, verificar y administrar información de diferentes transacciones. A pesar de esto, Blockchain se enfrenta a diferentes problemas de seguridad, siendo el ataque del 51% o ataque mayoritario uno de los más importantes. Este consiste en que uno o más mineros tomen el control de al menos el 51% del Hash extraído o del cómputo en una red; de modo que un minero puede manipular y modificar arbitrariamente la información registrada en esta tecnología. Este trabajo se enfocó en diseñar e implementar estrategias de detección y mitigación de ataques mayoritarios (51% de ataque) en un sistema distribuido Blockchain, a partir de la caracterización del comportamiento de los mineros. Para lograr esto, se analizó y evaluó el Hash Rate / Share de los mineros de Bitcoin y Crypto Ethereum, seguido del diseño e implementación de un protocolo de consenso para controlar el poder de cómputo de los mineros. Posteriormente, se realizó la exploración y evaluación de modelos de Machine Learning para detectar software malicioso de tipo Cryptojacking.DoctoradoDoctor en Ingeniería de Sistemas y Computació

    A Decision Support System for Economic Viability and Environmental Impact Assessment of Vertical Farms

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    Vertical farming (VF) is the practice of growing crops or animals using the vertical dimension via multi-tier racks or vertically inclined surfaces. In this thesis, I focus on the emerging industry of plant-specific VF. Vertical plant farming (VPF) is a promising and relatively novel practice that can be conducted in buildings with environmental control and artificial lighting. However, the nascent sector has experienced challenges in economic viability, standardisation, and environmental sustainability. Practitioners and academics call for a comprehensive financial analysis of VPF, but efforts are stifled by a lack of valid and available data. A review of economic estimation and horticultural software identifies a need for a decision support system (DSS) that facilitates risk-empowered business planning for vertical farmers. This thesis proposes an open-source DSS framework to evaluate business sustainability through financial risk and environmental impact assessments. Data from the literature, alongside lessons learned from industry practitioners, would be centralised in the proposed DSS using imprecise data techniques. These techniques have been applied in engineering but are seldom used in financial forecasting. This could benefit complex sectors which only have scarce data to predict business viability. To begin the execution of the DSS framework, VPF practitioners were interviewed using a mixed-methods approach. Learnings from over 19 shuttered and operational VPF projects provide insights into the barriers inhibiting scalability and identifying risks to form a risk taxonomy. Labour was the most commonly reported top challenge. Therefore, research was conducted to explore lean principles to improve productivity. A probabilistic model representing a spectrum of variables and their associated uncertainty was built according to the DSS framework to evaluate the financial risk for VF projects. This enabled flexible computation without precise production or financial data to improve economic estimation accuracy. The model assessed two VPF cases (one in the UK and another in Japan), demonstrating the first risk and uncertainty quantification of VPF business models in the literature. The results highlighted measures to improve economic viability and the viability of the UK and Japan case. The environmental impact assessment model was developed, allowing VPF operators to evaluate their carbon footprint compared to traditional agriculture using life-cycle assessment. I explore strategies for net-zero carbon production through sensitivity analysis. Renewable energies, especially solar, geothermal, and tidal power, show promise for reducing the carbon emissions of indoor VPF. Results show that renewably-powered VPF can reduce carbon emissions compared to field-based agriculture when considering the land-use change. The drivers for DSS adoption have been researched, showing a pathway of compliance and design thinking to overcome the ‘problem of implementation’ and enable commercialisation. Further work is suggested to standardise VF equipment, collect benchmarking data, and characterise risks. This work will reduce risk and uncertainty and accelerate the sector’s emergence

    Post-Millennial Queer Sensibility: Collaborative Authorship as Disidentification in Queer Intertextual Commodities

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    This dissertation is examining LGBTQ+ audiences and creatives collaborating in the creation of new media texts like web shows, podcasts, and video games. The study focuses on three main objects or media texts: Carmilla (web series), Welcome to Night Vale (podcast), and Undertale (video game). These texts are transmedia objects or intertextual commodities. I argue that by using queer gestures of collaborative authorship that reaches out to the audience for canonical contribution create an emerging queer production culture that disidentifies with capitalism even as it negotiates capitalistic structures. The post-millennial queer sensibility is a constellation of aesthetics, self-representation, alternative financing, and interactivity that prioritizes community, trust, and authenticity using new technologies for co-creation. Within my study, there are four key tactics or queer gestures being explored: remediation, radical ambiguity and multi-forms as queer aesthetics, audience self-representation, alternative financing like micropatronage & licensed fan-made merchandise, and interactivity as performance. The goal of this project is to better understand the changing conceptions of authorship/ownership, canon/fanon (official text/fan created extensions), and community/capitalism in queer subcultures as an indicator of the potential change in more mainstream cultural attitudes. The project takes into consideration a variety of intersecting identities including gender, race, class, and of course sexual orientation in its analysis. By examining the legal discourse around collaborative authorship, the real-life production practices, and audience-creator interactions and attitudes, this study provides insight into how media creatives work with audiences to co-create self-representative media, the motivations, and rewards for creative, audiences, and owners. This study aims to contribute towards a fuller understanding of queer production cultures and audience reception of these media texts, of which there is relatively little academic information. Specifically, the study mines for insights into the changing attitudes towards authorship, ownership, and collaboration within queer indie media projects, especially as these objects are relying on the self-representation of both audiences and creatives in the formation of the text

    Investigating and mitigating the role of neutralisation techniques on information security policies violation in healthcare organisations

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    Healthcare organisations today rely heavily on Electronic Medical Records systems (EMRs), which have become highly crucial IT assets that require significant security efforts to safeguard patients’ information. Individuals who have legitimate access to an organisation’s assets to perform their day-to-day duties but intentionally or unintentionally violate information security policies can jeopardise their organisation’s information security efforts and cause significant legal and financial losses. In the information security (InfoSec) literature, several studies emphasised the necessity to understand why employees behave in ways that contradict information security requirements but have offered widely different solutions. In an effort to respond to this situation, this thesis addressed the gap in the information security academic research by providing a deep understanding of the problem of medical practitioners’ behavioural justifications to violate information security policies and then determining proper solutions to reduce this undesirable behaviour. Neutralisation theory was used as the theoretical basis for the research. This thesis adopted a mixed-method research approach that comprises four consecutive phases, and each phase represents a research study that was conducted in light of the results from the preceding phase. The first phase of the thesis started by investigating the relationship between medical practitioners’ neutralisation techniques and their intention to violate information security policies that protect a patient’s privacy. A quantitative study was conducted to extend the work of Siponen and Vance [1] through a study of the Saudi Arabia healthcare industry. The data was collected via an online questionnaire from 66 Medical Interns (MIs) working in four academic hospitals. The study found that six neutralisation techniques—(1) appeal to higher loyalties, (2) defence of necessity, (3) the metaphor of ledger, (4) denial of responsibility, (5) denial of injury, and (6) condemnation of condemners—significantly contribute to the justifications of the MIs in hypothetically violating information security policies. The second phase of this research used a series of semi-structured interviews with IT security professionals in one of the largest academic hospitals in Saudi Arabia to explore the environmental factors that motivated the medical practitioners to evoke various neutralisation techniques. The results revealed that social, organisational, and emotional factors all stimulated the behavioural justifications to breach information security policies. During these interviews, it became clear that the IT department needed to ensure that security policies fit the daily tasks of the medical practitioners by providing alternative solutions to ensure the effectiveness of those policies. Based on these interviews, the objective of the following two phases was to improve the effectiveness of InfoSec policies against the use of behavioural justification by engaging the end users in the modification of existing policies via a collaborative writing process. Those two phases were conducted in the UK and Saudi Arabia to determine whether the collaborative writing process could produce a more effective security policy that balanced the security requirements with daily business needs, thus leading to a reduction in the use of neutralisation techniques to violate security policies. The overall result confirmed that the involvement of the end users via a collaborative writing process positively improved the effectiveness of the security policy to mitigate the individual behavioural justifications, showing that the process is a promising one to enhance security compliance
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