<div><div>The blockchain offers a decentralized way to provide security guarantees for financial transactions. However, this ability comes with the cost of storing a large (distributed) blockchain state and introducing additional computation and communication overhead to all participants. All these drawbacks raise a challenging scalability problem, especially for resource-constrained blockchain clients. On the other hand, some scaling solutions typically require resource-constrained clients to rely on other nodes with higher computational and storage capabilities. However, such scaling solutions often expose the data of the clients to risks of compromise of the more powerful nodes they rely on (e.g., accidental, malicious through a break-in, insider misbehavior, or malware infestation). This potential for leakage raises a privacy concern for these constrained clients, in addition to other scaling-related concerns. This dissertation proposes several cryptographic constructions and system designs enabling resource-constrained devices to participate in the blockchain network securely and efficiently. </div><div><br></div><div>Our first proposal concerns the storage facet for which we propose two add-on privacy designs to address the scaling issue of storing a large blockchain state. </div><div>The first solution is an oblivious database framework, called T³, that allows resource-constrained clients to obliviously fetch blockchain data from potential malicious full clients. The second solution focuses on the problem of using and storing additional private-by-design blockchains (e.g., Monero or ZCash) to achieve privacy. We propose an add-on tumbler design, called AMR, that offers privacy directly to clients of non-private blockchains such as Ethereum without the cost of storing and using different blockchain states.</div><div><br></div><div>Our second proposal addresses the communication facet with focus on payment channels as a solution to address the communication overhead between the constrained clients and the blockchain network. A payment channel enables transactions between arbitrary pairs of constrained clients with a minimal communication overhead with the blockchain network. However, in popular blockchains like Ethereum and Bitcoin, the payment data of such channels are exposed to the public, which is undesirable for financial applications. Thus, to hide transaction data, one can use blockchains that are private by design like Monero. However, existing cryptographic primitives in Monero prevent the system from supporting any form of payment channels. Therefore, we present <i>Dual Linkable Spontaneous Anonymous Group Signature for Ad Hoc Groups (DLSAG),</i> a linkable ring signature scheme that enables, for the first time, off-chain scalability solutions in Monero. </div><div><br></div><div>To address the computation facet, we address the computation overhead of the gossip protocol used in all popular blockchain protocols. For this purpose, we propose a signature primitive called <i>Flexible Signature</i>. In a flexible signature scheme, the verification algorithm quantifies the validity of a signature based on the computational effort performed by the verifier. Thus, the resource-constrained devices can partially verify the signatures in the blockchain transactions before relaying transactions to other peers. This primitive allows the resource-constrained devices to prevent spam transactions from flooding the blockchain network with overhead that is consistent with their resource constraints. </div></div>

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Website scaling has been an issue since the inception of the web. The demand for user generated content and personalized web pages requires the use of a database for a storage engine. Unfortunately, scaling the database to handle large amounts of traffic is still a problem many companies face. One such company is iFixit, a provider of free, publicly-editable, online repair manuals. Like many websites, iFixit uses Memcached to decrease database load and improve response time. However, the caching strategy used is a very ad hoc one and therefore can be greatly improved. Most research regarding web application caching focuses on cache invalidation, the process of keeping cached content consistent with the permanent data store. Generational caching is a technique that involves including the object’s last modified date in the cache key. This ensures that cache keys change when- ever the object is modified, which effectively invalidates all relevant cache entries. Fine-grained caching is now very simple because the developer doesn’t need to explicitly delete all possible cache keys that might need to be invalidated when an object is modified. This is particularly useful for caching arbitrary fragments of HTML without increasing the complexity of cache invalidation. In this work, we describe the process of implementing a caching strategy based on generational caching concepts in iFixit’s website. Our implementation yielded a 20% improvement in page response time by caching fragments of HTML and results of database queries.

Students wishing to attend student events, as well as the event organisers, currentlyface several inconveniences at the sign-up occasion, due to prevailing solutions’ lack ofdeep consideration for efficiency. This report investigates how a web-based sign-up appli-cation for student events can be implemented to handle high server traffic, by developingand testing a solution that allows for a quick sign-up process, payment directly at the sign-up occasion and the gathering of relevant attendee information.By considering code optimization strategies and the change of database from SQLite toMongoDB, based on the prevailing literature on the topic, a test script together with hightraffic testing was utilised to measure the relative performance of each of these implemen-tations, relative to the initial web-application. Results show that all four aspects tested weresignificant in terms of improving the handling of high traffic. Based on this, the conclusiondrawn was that all four aspects: time optimization, space optimization, minification, and adocument-based database, should be considered when improving a web-application thatallows for handling of high traffic. This finding confirms the prevailing literature on thetopic, however, the implementation phase also raised suggestions for future and improvedresearch on the topic. / Studenter som önskar gå på studentevent, likväl som eventorganisatörerna, möts idagsläget av flertalet olägenheten vid anmälningstillfället, eftersom nuvarande lösningarsaknar djupare hänsyn till effektivitet. Denna rapport undersöker hur en web-baserad an-mälningsapplikation för studentevent kan implementeras för att hantera hög servertrafik,genom att utveckla och testa en lösning som tillåter en snabb anmälningsprocess, betalningdirekt vid anmälningstillfället och insamling av relevant deltagarinformation. Genom att tahänsyn till kodoptimeringsstrategier och byte av databas från SQLite till MongoDB, baseratpå tidigare literatur om området, så används ett testskript och ett test för hög servertrafikför att mäta den relativa prestandan av vardera implementation, relativt till den initialaimplementationen. Resultatet visar att alla fyra undersökta aspekterna var signifikanta föratt förbättra hanteringen av hög trafik. Baserat på detta drogs slutsatsen att alla fyra aspek-terna: “time optimation”, “space optimization”, “minification” och en dokumentbaseraddatabas, borde tas hänsyn till när man implementerar en webbapplikation som tillåter förhantering av hög trafik. Denna upptäckt bekräftar den tidigare litteraturen om områden,men, implementationsfasen lyfte även förslag för framtida och förbättrad forskning på området.

The Vocabulary Research Database (VRD) is a research tool comprised of a compilation of state-of-the art academic research in the field of vocabulary acquisition and pedagogy. The VRD has flexible search features that allow users to obtain higher granularity than is possible with other free databases and online search options currently available, making the results more relevant and manageable. These features include the ability to constrain results by date, author, publication, sub-topics, keywords, citation numbers, journal impact factors, and participant ages. It is anticipated that the ability to manipulate results, combined with relevant and current content, will provide language professionals with a valuable tool for accessing vocabulary-specific research, enabling them to better inform and improve their work.

Increasingly more users are accessing database systems for interactive and exploratory data retrieval. While performing searches on these systems, users are required to use broad queries to get their desired results. Broad queries often result in too many items forcing the user to spend unnecessary time sifting through these items to find the relevant results. This problem, of finding a desired data item within many items, is referred to as "information overload". Most users experience information overload when viewing these database query results. This thesis shows that users information overload can be reduced by clustering database query results. A hierarchical agglomerative clustering algorithm is used to cluster the query results. The reduction of users information overload is evaluated using Chakrabarti et al information overload cost model. Empirical results show that users are able to find more relevant information as well as experiencing a reduction in information overload.

Groups of agriculturalist/hunter-gatherers known as the Fremont inhabited the eastern Great Basin and Colorado Plateau from roughly A.D. 1-A.D. 1350 (Madsen 1989). Fremont groups used differing storage strategies through time and across space. Storage strategies included on-site and off-site storage facilities which were constructed above and/or below-ground. These forms of storage occurred at different frequencies and times throughout the Fremont's 1350 year time span. Researchers (Binford 1980, 1990; Keeley 1988; Soffer 1989; Testart 1982; Wills 1992; Young 1996) using examples from various parts of the world have noted a correlation between the degree of residential mobility and the use of storage. Lisa Young's (1996) model of storage and mobility posits that there is a direct correlation between the types of storage facilities a group uses and the level of mobility that they engage in. Generally, groups who use subterranean and/or off-site storage engage in a mobile or semi-sedentary settlement strategy and those who use on-site above-ground storage engage in a sedentary settlement strategy. This model was used to analyze mobility among the Fremont. To do so, a storage database was created which contained information on Fremont storage features such as type, location, date, and size. Analysis shows that there was a general trend of increasing sedentism through time for the Fremont, although this trend varies in degree through three general time periods and in three geographic areas. Further, the data was analyzed to determine whether there was significant spatial or temporal patterning of storage facilities. It was found that significant patterns do exist and are correlated in part with Fremont mobility.

The vocal performance database is a tool by which BYU vocal performance faculty and students may practice, assess, and review vocal performances, including practice juries, recitals, and end-of-semester juries. This document describes the process and results of designing, developing, implementing, and evaluating the vocal performance database. By using this tool, vocal performance professors are able to give faster, more quality feedback to students following the jury. Students are able to receive legible feedback from their professors in a timely manner.

Empirical research is inexact and error-prone leading researchers to agree that replication of experiments is a necessary step to validating empirical results. Unfortunately, replicating experiments requires substantial investments in manpower and time. These resource requirements can be reduced by incorporating component reuse when building tools for empirical experimentation. Bokeo is an initiative within the Sequoia Lab of the BYU Computer Science Department to develop a platform to assist in the empirical study of software engineering. The i3Persistence Framework is a component of Bokeo which enables researchers to easily build and rapidly deploy tools for empirical experiments by providing an easy-to-use database management service. We introduce the i3Persistence Framework of Bokeo to assist in the development of software to replicate experiments and conduct studies on data from open-source repositories.