Reliable distributed information : agreement and structure

The world is inherently distributed and concurrent. The more complicated systems become, the more likely they are to fail or partially fail. This work presents several results with Byzantine Agreement and some results of using coding in solving distributed and concurrent problems. We explore adding weights to processes to model a priori knowledge of process reliability. Then, some results of what can be done when performing repeated agreement. A result between combinatorial geometry and approximate Byzantine agreement is also provided. Coding is often used in communication, but here we provide examples of the usage of coding to minimize broadcast information and to solve a concurrent problem. The first use of coding is to notice the redundant information in distributed protocols and how to use a code to reduce the amount of information needed to be transmitted. The second is a method of using coding to provide a buffer of memory in a concurrent system that can be updated such that readers see the update as atomic.Electrical and Computer Engineerin

Secure Network Provenance

This paper introduces secure network provenance (SNP), a novel technique that enables networked systems to explain to their operators why they are in a certain state – e.g., why a suspicious routing table entry is present on a certain router, or where a given cache entry originated. SNP provides network forensics capabilities by permitting operators to track down faulty or misbehaving nodes, and to assess the damage such nodes may have caused to the rest of the system. SNP is designed for adversarial settings and is robust to manipulation; its tamper-evident properties ensure that operators can detect when compromised nodes lie or falsely implicate correct nodes. We also present the design of SNooPy, a general-purpose SNP system. To demonstrate that SNooPy is practical, we apply it to three example applications: the Quagga BGP daemon, a declarative implementation of Chord, and Hadoop MapReduce. Our results indicate that SNooPy can efficiently explain state in an adversarial setting, that it can be applied with minimal effort, and that its costs are low enough to be practical

The Bitcoin Backbone Protocol: Analysis and Applications

Bitcoin is the first and most popular decentralized cryptocurrency to date. In this work, we extract and analyze the core of the Bitcoin protocol, which we term the Bitcoin backbone, and prove two of its fundamental properties which we call common prefix and chain quality in the static setting where the number of players remains fixed. Our proofs hinge on appropriate and novel assumptions on the hashing power of the adversary relative to network synchronicity; we show our results to be tight under high synchronization. Next, we propose and analyze applications that can be built on top of the backbone protocol, specifically focusing on Byzantine agreement (BA) and on the notion of a public transaction ledger. Regarding BA, we observe that Nakamoto\u27s suggestion falls short of solving it, and present a simple alternative which works assuming that the adversary\u27s hashing power is bounded by 1/3. The public transaction ledger captures the essence of Bitcoin\u27s operation as a cryptocurrency, in the sense that it guarantees the liveness and persistence of committed transactions. Based on this notion we describe and analyze the Bitcoin system as well as a more elaborate BA protocol, proving them secure assuming high network synchronicity and that the adversary\u27s hashing power is strictly less than 1/2, while the adversarial bound needed for security decreases as the network desynchronizes. Finally, we show that our analysis of the Bitcoin backbone protocol for synchronous networks extends with relative ease to the recently considered partially synchronous model, where there is an upper bound in the delay of messages that is unknown to the honest parties

LIPIcs, Volume 251, ITCS 2023, Complete Volume

LIPIcs, Volume 251, ITCS 2023, Complete Volum

Between freedom and givenness: (a study of the hermeneutical consequences of the concept of canon for the authority of scripture)

The aim of this thesis is to arrive at an understanding of the authority of scripture that is able to accommodate both a faith perspective and the fruits of the historical-critical approach to the New Testament. Put differently, the aim of this thesis is the pursuit of a specifically christian, faith-promoting, reading of the New Testament whilst still enjoying the benefit, in an as uncompromised a form as possible, of the historical- critical approach. In a sense it may be said that this task, given that the roots of both the historical-critical approach and modern Western culture are deeply imbedded in Rationalism, is equivalent to the basic hermeneutical question of whether it is possible to interpret scripture relevantly from within a cultural web of meaning that does not readily accommodate that embodied in the New Testament. In section one of this dissertation we present a characteristic depiction, based on the historical-critical theory of literature, of the authority of the New Testament. This is followed by a brief assessment that makes explicit why the historical- critical approach is not conducive to the adoption of a faith perspective on these writings. In section two, still and inevitably based on critical foundations, we adopt a perspective that is more sympathetic to faith and that seeks to discover in the concerns evidenced in the canonical process, when traditions about Jesus gradually took on more complex and stable forms, culminating in the canon of the New Testament, guidelines in helping us to deal with the problem with which this study is concerned . In the specific example of the rather ordinary concerns underlying the unusual history of the pericope de adultera (John 7:53-8:11), examined against the background of the interests underlying the canonical process, it becomes clear that christians from the very beginning faced a dilemma not unlike that with which the historical-critical approach confronts us. They had to interpret afresh, and faithfully, the traditions in order to meet the demands of situations that had never been foreseen by earlier tradents. In this respect, therefore, the history of the pericope de adultera presents us with an ongoing struggle to hold in tension the demands of new contexts with the imperative of strict continuity with Jesus. In section three, on the basis of the foundation of the authority of scripture in strict continuity with Jesus combined with the contextual reinterpretation of the tradition, the social sciences are employed. Using the social sciences, it is discovered that the two contradictory approaches that we wish to reconcile form part of two different models for interpreting reality. It is on this basis, and made possible by the common culture underlying these opposing models and by the common contact with an unspecified common core of concrete reality, that a solution is proposed in terms of a complex 'fusion of horizons', promoted by a 'precipitative environment'. In the conclusion our solution is decisively aligned with the concerns evidenced in the canonical proces

Histories of Medieval European Literatures: New Patterns of Representation and Explanation

Interfaces: A Journal of Medieval European Literatures is invested in bringing together the linguistic, literary, and historical expertise to take a European approach to medieval literature. The journal aims to establish a forum both for articles which move across literatures (plural) and also, more ambitiously, to foster reflections on a more elusive, but no longer entirely absent, object, European medieval literature (singular).In line with the journal’s scope and vision to promote integrated approaches to European medieval literatures, we begin by facing head-on the multiple challenges of devising new types of narratives about medieval textual cultures. We have invited papers which take a wider regional perspective and move across medieval Europe as well as papers which bring an explicitly European perspective to more specific topics (with a tighter thematic, chronological, geographic, or linguistic focus)

On videogames:representing narrative in an interactive medium

This thesis investigates the function of narrative in videogames, challenging views that games do not—and should not—have anything to do with narrative. It tests videogames against literary narrative theories and examines ways in which videogames have evolved beyond other narratives and narrative theories. The narrative vs. ludology debate among videogame scholars has, at its core, the question of whether narrative is possible in videogames. Ludologists, who prioritize videogames as games, argue that narrative is incompatible with play, both interrupting and interfering with it. My research suggests that videogames often render narrative and play symbiotic, even inseparable, as the act of playing reveals and produces videogame narrative. Other objections to videogame narrative include the argument that videogame narrative is less sophisticated than narrative forms in other media. My thesis demonstrates that some videogames contain narrative every bit as complex as those in literature and film, holding up to rigorous testing by complex narratological theories. It further shows that changes in videogame technology and design have brought about evolutions in narrative that are the result of playing rather than being at odds with it. As narrative has evolved in videogames beyond its manifestations in older media, narrative theories developed to account for older media prove to be inadequate to explicate videogame narratives. The introduction and first chapter of the thesis delineate these issues, theories, and debates. The remaining chapters probe how videogame narrative unfolds in specific areas, such as identity and identification, the navigation of narrative space, narrative agency and authority, consumer ethics, and concepts of death and genre. Finally, the thesis considers the endings of videogames and how death is presented and represented in this medium. My conclusion summarises my own work and suggests possibilities for future studies of videogame narratives