8,185 research outputs found

    Configuration Management of Distributed Systems over Unreliable and Hostile Networks

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    Economic incentives of large criminal profits and the threat of legal consequences have pushed criminals to continuously improve their malware, especially command and control channels. This thesis applied concepts from successful malware command and control to explore the survivability and resilience of benign configuration management systems. This work expands on existing stage models of malware life cycle to contribute a new model for identifying malware concepts applicable to benign configuration management. The Hidden Master architecture is a contribution to master-agent network communication. In the Hidden Master architecture, communication between master and agent is asynchronous and can operate trough intermediate nodes. This protects the master secret key, which gives full control of all computers participating in configuration management. Multiple improvements to idempotent configuration were proposed, including the definition of the minimal base resource dependency model, simplified resource revalidation and the use of imperative general purpose language for defining idempotent configuration. Following the constructive research approach, the improvements to configuration management were designed into two prototypes. This allowed validation in laboratory testing, in two case studies and in expert interviews. In laboratory testing, the Hidden Master prototype was more resilient than leading configuration management tools in high load and low memory conditions, and against packet loss and corruption. Only the research prototype was adaptable to a network without stable topology due to the asynchronous nature of the Hidden Master architecture. The main case study used the research prototype in a complex environment to deploy a multi-room, authenticated audiovisual system for a client of an organization deploying the configuration. The case studies indicated that imperative general purpose language can be used for idempotent configuration in real life, for defining new configurations in unexpected situations using the base resources, and abstracting those using standard language features; and that such a system seems easy to learn. Potential business benefits were identified and evaluated using individual semistructured expert interviews. Respondents agreed that the models and the Hidden Master architecture could reduce costs and risks, improve developer productivity and allow faster time-to-market. Protection of master secret keys and the reduced need for incident response were seen as key drivers for improved security. Low-cost geographic scaling and leveraging file serving capabilities of commodity servers were seen to improve scaling and resiliency. Respondents identified jurisdictional legal limitations to encryption and requirements for cloud operator auditing as factors potentially limiting the full use of some concepts

    Southern Adventist University Undergraduate Catalog 2023-2024

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    Southern Adventist University\u27s undergraduate catalog for the academic year 2023-2024.https://knowledge.e.southern.edu/undergrad_catalog/1123/thumbnail.jp

    A Trust Management Framework for Vehicular Ad Hoc Networks

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    The inception of Vehicular Ad Hoc Networks (VANETs) provides an opportunity for road users and public infrastructure to share information that improves the operation of roads and the driver experience. However, such systems can be vulnerable to malicious external entities and legitimate users. Trust management is used to address attacks from legitimate users in accordance with a user’s trust score. Trust models evaluate messages to assign rewards or punishments. This can be used to influence a driver’s future behaviour or, in extremis, block the driver. With receiver-side schemes, various methods are used to evaluate trust including, reputation computation, neighbour recommendations, and storing historical information. However, they incur overhead and add a delay when deciding whether to accept or reject messages. In this thesis, we propose a novel Tamper-Proof Device (TPD) based trust framework for managing trust of multiple drivers at the sender side vehicle that updates trust, stores, and protects information from malicious tampering. The TPD also regulates, rewards, and punishes each specific driver, as required. Furthermore, the trust score determines the classes of message that a driver can access. Dissemination of feedback is only required when there is an attack (conflicting information). A Road-Side Unit (RSU) rules on a dispute, using either the sum of products of trust and feedback or official vehicle data if available. These “untrue attacks” are resolved by an RSU using collaboration, and then providing a fixed amount of reward and punishment, as appropriate. Repeated attacks are addressed by incremental punishments and potentially driver access-blocking when conditions are met. The lack of sophistication in this fixed RSU assessment scheme is then addressed by a novel fuzzy logic-based RSU approach. This determines a fairer level of reward and punishment based on the severity of incident, driver past behaviour, and RSU confidence. The fuzzy RSU controller assesses judgements in such a way as to encourage drivers to improve their behaviour. Although any driver can lie in any situation, we believe that trustworthy drivers are more likely to remain so, and vice versa. We capture this behaviour in a Markov chain model for the sender and reporter driver behaviours where a driver’s truthfulness is influenced by their trust score and trust state. For each trust state, the driver’s likelihood of lying or honesty is set by a probability distribution which is different for each state. This framework is analysed in Veins using various classes of vehicles under different traffic conditions. Results confirm that the framework operates effectively in the presence of untrue and inconsistent attacks. The correct functioning is confirmed with the system appropriately classifying incidents when clarifier vehicles send truthful feedback. The framework is also evaluated against a centralized reputation scheme and the results demonstrate that it outperforms the reputation approach in terms of reduced communication overhead and shorter response time. Next, we perform a set of experiments to evaluate the performance of the fuzzy assessment in Veins. The fuzzy and fixed RSU assessment schemes are compared, and the results show that the fuzzy scheme provides better overall driver behaviour. The Markov chain driver behaviour model is also examined when changing the initial trust score of all drivers

    LIPIcs, Volume 251, ITCS 2023, Complete Volume

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    LIPIcs, Volume 251, ITCS 2023, Complete Volum

    Performance Anomalies in Concurrent Data Structure Microbenchmarks

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    Recent decades have witnessed a surge in the development of concurrent data structures with an increasing interest in data structures implementing concurrent sets (CSets). Microbenchmarking tools are frequently utilized to evaluate and compare the performance differences across concurrent data structures. The underlying structure and design of the microbenchmarks themselves can play a hidden but influential role in performance results. However, the impact of microbenchmark design has not been well investigated. In this work, we illustrate instances where concurrent data structure performance results reported by a microbenchmark can vary 10-100x depending on the microbenchmark implementation details. We investigate factors leading to performance variance across three popular microbenchmarks and outline cases in which flawed microbenchmark design can lead to an inversion of performance results between two concurrent data structure implementations. We further derive a set of recommendations for best practices in the design and usage of concurrent data structure microbenchmarks and explore advanced features in the Setbench microbenchmark

    The Viability of Domain Constrained Coalition Formation for Robotic Collectives

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    Applications, such as military and disaster response, can benefit from robotic collectives' ability to perform multiple cooperative tasks (e.g., surveillance, damage assessments) efficiently across a large spatial area. Coalition formation algorithms can potentially facilitate collective robots' assignment to appropriate task teams; however, most coalition formation algorithms were designed for smaller multiple robot systems (i.e., 2-50 robots). Collectives' scale and domain-relevant constraints (i.e., distribution, near real-time, minimal communication) make coalition formation more challenging. This manuscript identifies the challenges inherent to designing coalition formation algorithms for very large collectives (e.g., 1000 robots). A survey of multiple robot coalition formation algorithms finds that most are unable to transfer directly to collectives, due to the identified system differences; however, auctions and hedonic games may be the most transferable. A simulation-based evaluation of three auction and hedonic game algorithms, applied to homogeneous and heterogeneous collectives, demonstrates that there are collective compositions for which no existing algorithm is viable; however, the experimental results and literature survey suggest paths forward.Comment: 46 pages, 9 figures, Swarm Intelligence (under review

    Beam scanning by liquid-crystal biasing in a modified SIW structure

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    A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

    Engineering Systems of Anti-Repressors for Next-Generation Transcriptional Programming

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    The ability to control gene expression in more precise, complex, and robust ways is becoming increasingly relevant in biotechnology and medicine. Synthetic biology has sought to accomplish such higher-order gene regulation through the engineering of synthetic gene circuits, whereby a gene’s expression can be controlled via environmental, temporal, or cellular cues. A typical approach to gene regulation is through transcriptional control, using allosteric transcription factors (TFs). TFs are regulatory proteins that interact with operator DNA elements located in proximity to gene promoters to either compromise or activate transcription. For many TFs, including the ones discussed here, this interaction is modulated by binding to a small molecule ligand for which the TF evolved natural specificity and a related metabolism. This modulation can occur with two main phenotypes: a TF shows the repressor (X+) phenotype if its binding to the ligand causes it to dissociate from the DNA, allowing transcription, while a TF shows the anti-repressor (XA) phenotype if its binding to the ligand causes it to associate to the DNA, preventing transcription. While both functional phenotypes are vital components of regulatory gene networks, anti-repressors are quite rare in nature compared to repressors and thus must be engineered. We first developed a generalized workflow for engineering systems of anti-repressors from bacterial TFs in a family of transcription factors related to the ubiquitous lactose repressor (LacI), the LacI/GalR family. Using this workflow, which is based on a re-routing of the TF’s allosteric network, we engineered anti-repressors in the fructose repressor (anti-FruR – responsive to fructose-1,6-phosphate) and ribose repressor (anti-RbsR – responsive to D-ribose) scaffolds, to complement XA TFs engineered previously in the LacI scaffold (anti-LacI – responsive to IPTG). Engineered TFs were then conferred with alternate DNA binding. To demonstrate their utility in synthetic gene circuits, systems of engineered TFs were then deployed to construct transcriptional programs, achieving all of the NOT-oriented Boolean logical operations – NOT, NOR, NAND, and XNOR – in addition to BUFFER and AND. Notably, our gene circuits built using anti-repressors are far simpler in design and, therefore, exert decreased burden on the chassis cells compared to the state-of-the-art as anti-repressors represent compressed logical operations (gates). Further, we extended this workflow to engineer ligand specificity in addition to regulatory phenotype. Performing the engineering workflow with a fourth member of the LacI/GalR family, the galactose isorepressor (GalS – naturally responsive to D-fucose), we engineered IPTG-responsive repressor and anti-repressor GalS mutants in addition to a D-fucose responsive anti-GalS TF. These engineered TFs were then used to create BANDPASS and BANDSTOP biological signal processing filters, themselves compressed compared to the state-of-the-art, and open-loop control systems. These provided facile methods for dynamic turning ‘ON’ and ‘OFF’ of genes in continuous growth in real time. This presents a general advance in gene regulation, moving beyond simple inducible promoters. We then demonstrated the capabilities of our engineered TFs to function in combinatorial logic using a layered logic approach, which currently stands as the state-of-the art. Using our anti-repressors in layered logic had the advantage of reducing cellular metabolic burden, as we were able to create the fundamental NOT/NOR operations with fewer genetic parts. Additionally, we created more TFs to use in layered logic approaches to prevent cellular cross-talk and minimize the number of TFs necessary to create these gene circuits. Here we demonstrated the successful deployment of our XA-built NOR gate system to create the BUFFER, NOT, NOR, OR, AND, and NAND gates. The work presented here describes a workflow for engineering (i) allosteric phenotype, (ii) ligand selectivity, and (iii) DNA specificity in allosteric transcription factors. The products of the workflow themselves serve as vital tools for the construction of next-generation synthetic gene circuits and genetic regulatory devices. Further, from the products of the workflow presented here, certain design heuristics can be gleaned, which should better facilitate the design of allosteric TFs in the future, moving toward a semi-rational engineering approach. Additionally, the work presented here outlines a transcriptional programming structure and metrology which can be broadly adapted and scaled for future applications and expansion. Consequently, this thesis presents a means for advanced control of gene expression, with promise to have long-reaching implications in the future.Ph.D

    Development of DNA origami-based tools for cancer treatment

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    DNA has been used as material for the assembly of objects at different scales. Particularly, the introduction of DNA origami has been inspiring the design and construction of many different versions of DNA nanostructures for, especially, biomedical applications. DNA origami nanostructures are showing unique advantages, including structural homogeneity, addressability, biocompatibility, and capacity to carry pharmaceuticals or biomolecules, for the development of future cancer therapeutics. To fully unlock their potential, however, they need to be tailored based on physiological and pathological molecular environments which they interact with. In this thesis, we develop a few functionalized DNA origami nanostructures to investigate specific questions of cancer biology or to overcome challenges of cancer immunotherapy. In PAPER I, we compare the physical characteristics of a compact lattice-based rod and a wireframe-styled rod and revealed how they interact with cell spheroid tissue models (CSTMs). Our data indicate that the wireframe structure, which has a lower local material density in design, has higher local deformability than the lattice-based structure. We reveal that these physical differences play important roles in the interaction between DNA origami nanostructures and human cancer cells, showing that wireframe rods are more likely to stay on the cell membrane, rather than being internalized, and this facilitates their deeper penetration into CSTMs. These observations tell us that DNA origami design methods should be carefully considered in DNA origami-based drug delivery applications. In PAPER II, to explore the nanoscale clustering effect of death receptor 5 (DR5) on human breast cancer cells, we develop flat sheet-like DNA origami nanostructures and functionalize them with the tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)- mimicking peptides which can recognize and bind with DR5, in differently sized hexagonal patterns. Experiments of cancer cells and DNA origami incubation show that apoptosis can be precisely controlled when we vary the size of peptide patterns between the range of 6 nm to 26 nm. Interestingly, our data indicate that the interpeptide distance for effective apoptosis is sub-10 nm. Our findings highlight the potency of precise spatial patterning of ligands on apoptosis signaling. In PAPER III, to limit cytotoxicity of the sub-10 nm peptide pattern, which we have screened out in the work of PAPER II, only to tumors, we design a three-dimensional DNA origami nanostructure containing a 6 nm wide and 12 nm deep cavity and use it to hide but display the peptide pattern according to the acidity of the tissue microenvironment. Peptide display is achieved by the protonation-triggered formation of the DNA triplex, during which a singlestranded DNA extension from the complementary strand of a mini-scaffold DNA wraps back to the mini-scaffold duplex. By varying the AT percentage in the mini-scaffold DNA, we can control the triggering pH for the formation of the DNA triplex. We demonstrate the safety of the DNA origami under physiological pH (pH 7.4) for non-cancer cells and its cytotoxicity to cancer cells under the pH of solid tumors (pH 6.5). In PAPER IV, to mimic functions of T cell engagers but mitigate corresponding adverse effects mainly caused by “on-target, off-tumor” immune activation and cytokine release syndrome, we develop a wireframe DNA origami based-nanorobot: a double-layered barrellike origami with antibodies inside under its closed status. When the DNA nanorobot presents as its open configuration, internal antibodies get exposed, functioning to engage T cells with cancer cells and activate T cell immune killing. By spatiotemporally controlling the opening of the DNA nanorobot via signals from cancer cells, tumor microenvironment, or external stimulus, we aim to selectively redirect the cytotoxicity of T cells to solid cancers and substantially mitigate corresponding adverse effects of current T cell engagers-based cancer immunotherapy
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