Applications of the Blockchain using cryptography

PhD ThesisWe have witnessed the rise of cryptocurrencies in the past eight years. Bitcoin and Ethereum are the world’s most successful cryptocurrencies with market capitalisations of $37bn and$21bn respectively in June 2017. The innovation behind these cryptocurrencies is the blockchain which is an immutable and censorship resistant public ledger. Bitcoin introduced the blockchain to trade a single asset (i.e. bitcoins), whereas Ethereum adopted the blockchain to store and execute expressive smart contracts. In this thesis, we consider cryptographic protocols that bootstrap trust from the blockchain. This includes secure end-to-end communication between two pseudonymous users, payment protocols, payment networks and decentralised internet voting. The first three applications rely on Bitcoin, whereas the final e-voting application is realised using Ethereum. First, it is important to highlight that Bitcoin was designed to protect the anonymity (or pseudonymity) for financial transactions. Nakamoto proposed that financial privacy is achievable by storing each party’s pseudonym (and not their real-world identity) in a transaction. We highlight that this approach for privacy has led to real-world authentication issues as merchants are failing to re-authenticate customers in post-transaction correspondence. To alleviate these issues, we propose an end-to-end secure communication protocol for Bitcoin users that does not require any trusted third party or public-key infrastructure. Instead, our protocol leverages the Blockchain as an additional layer of authentication. Furthermore, this insight led to the discovery of two attacks in BIP70: Payment Protocol which is a community-accepted standard used by more than 100,000 merchants. Our attacks were acknowledged by the leading payment processors including Coinbase, BitPay and Bitt. As well, we have proposed a revised Payment Protocol that prevents both attacks. Second, Bitcoin as deployed today does not scale. Scalability research has focused on two directions: 1) redesigning the Blockchain protocol, and 2) facilitating ‘off-chain transactions’ and only consulting the Blockchain if an adjudicator is required. We focus on the latter and provide an overview of Bitcoin payment networks. These consist of two components: payment channels to facilitate off-chain transactions between two parties, and the capability to fairly exchange bitcoins across multiple channels. We compare Duplex Micropayment Channels and Lightning Channels, before discussing Hashed Time Locked Contracts which viii enable Bitcoin-based payment networks. Furthermore, we highlight challenges in routing and path-finding that need to be overcome before payment networks are practically feasible. Finally, we study the feasibility of executing cryptographic protocols on Ethereum. We provide the first implementation of a decentralised and self-tallying internet voting protocol with maximum voter privacy as a smart contract. The Open Vote Network is suitable for boardroom elections and is written as a smart contract for Ethereum. Unlike previously proposed Blockchain e-voting protocols, this is the first implementation that does not rely on any trusted authority to compute the tally or to protect the voter’s privacy. Instead, the Open Vote Network is a self-tallying protocol, and each voter is in control of the privacy of their own vote such that it can only be breached by a full collusion involving all other voters. The execution of the protocol is enforced using the consensus mechanism that also secures the Ethereum blockchain. We tested the implementation on Ethereum’s official test network to demonstrate its feasibility. Also, we provide a financial and computational breakdown of its execution cost

Web-Based Management and Lending System

Cílem této práce je analýza a implementace webového systému pro správu a půjčování zařízení, které uživatelům zprostředkuje přehled dat v systému a historii transakcí zařízení. Výsledná aplikace byla implementována v PHP s využitím Nette Frameworku, MySQL a AJAXu. V první polovině této práce je probrána analýza existujících platforem, popis jednotlivých fází implementace a seznam využitých návrhových vzorů. Druhá polovina pojednává o testování, využitých komponentách a jejich opodstatnění, a nakonec sumarizuje využitelnost implementovaného systému. Výsledkem této práce je implementace systému pro správu a půjčování zařízení, který uživatelům umožňuje vést efektivní evidenci půjčování položek.The aim of this thesis is to analyze and implement a web-based equipment checkout system, which provides an organized outlook on system data and equipment transactions history. The final application was implemented as a server-side application using Nette Framework under PHP, MySQL and AJAX. The first half of this thesis investigates existing solutions, describes the implementation phases and looks at design patterns present in the code. The second half of the paper examines the testing, mentions all used add-on components and their purpose, and finally assesses the usability of the implemented system. The result of this paper is an implemented equipment checkout system giving its users an effective way to manage item lending.

Censorship by Proxy: The First Amendment, Internet Intermediaries, and the Problem of the Weakest Link

The rise of the Internet has changed the First Amendment drama, for governments confront technical and political obstacles to sanctioning either speakers or listeners in cyberspace. Faced with these challenges, regulators have fallen back on alternatives, predicated on the fact that, in contrast to the usual free expression scenario, the Internet is not dyadic. The Internet\u27s resistance to direct regulation of speakers and listeners rests on a complex chain of connections, and emerging regulatory mechanisms have begun to focus on the weak links in that chain. Rather than attacking speakers or listeners directly, governments have sought to enlist private actors within the chain as proxy censors to control the flow of information. Some commentators have celebrated such indirect methods of governmental control as salutary responses to threatening cyberanarchy. This Article takes a more jaundiced view of these developments: I begin by mapping the ubiquity of efforts to enlist Internet intermediaries as proxy censors. I emphasize the dangers to free expression that are likely to arise from attempts to target weak links in the chain of Internet communications and cast doubt on the claim that mar-ket mechanisms can be relied upon to dispel them. I then proceed to explore the doctrinal resources that can meet those dangers. The gambit of enlisting the private sector to establish a system to control ex-pression is not new in the United States. I argue that the First Amendment doctrines developed in response to the last such focused effort, during the McCarthy era, provide a series of useful starting points for a First Amendment doctrine to protect the weak links of the Internet

Characteristics of Web-based textual communications

Ankara : The Department of Computer Engineering and the Graduate School of Engineering and Science of Bilkent University 2012.Thesis (Ph. D.) -- Bilkent University, 2012.Includes bibliographical references.In this thesis, we analyze different aspects of Web-based textual communications and argue that all such communications share some common properties. In order to provide practical evidence for the validity of this argument, we focus on two common properties by examining these properties on various types of Web-based textual communications data. These properties are: All Web-based communications contain features attributable to their author and reciever; and all Web-based communications exhibit similar heavy tailed distributional properties. In order to provide practical proof for the validity of our claims, we provide three practical, real life research problems and exploit the proposed common properties of Web-based textual communications to find practical solutions to these problems. In this work, we first provide a feature-based result caching framework for real life search engines. To this end, we mined attributes from user queries in order to classify queries and estimate a quality metric for giving admission and eviction decisions for the query result cache. Second, we analyzed messages of an online chat server in order to predict user and mesage attributes. Our results show that several user- and message-based attributes can be predicted with significant occuracy using both chat message- and writing-style based features of the chat users. Third, we provide a parallel framework for in-memory construction of term partitioned inverted indexes. In this work, in order to minimize the total communication time between processors, we provide a bucketing scheme that is based on term-based distributional properties of Web page contents.Küçükyılmaz, TayfunPh.D

Facebook and Interpersonal Privacy: Why the Third Party Doctrine Should Not Apply

Do communications over social networking sites such as Facebook merit Fourth Amendment protection? The Supreme Court has not directly answered this question and lower courts are not in agreement. The hurdle is the Third Party Doctrine, which states that a person does not have a reasonable expectation of privacy in any communication voluntarily disclosed to a person or entity. All Internet communications are stored on third party servers or Internet service providers, and thus would seemingly lose Fourth Amendment protection. Numerous scholars have weighed in on the issue—analyzing the nature of the communication or the entity to which the information is disclosed—in an effort to show that these communications continue to merit Fourth Amendment protection. These scholars, however, have largely ignored the overall effect of communications over social networking sites such as Facebook. This Article steps outside traditional Fourth Amendment scholarship and relies on the concept of interpersonal privacy rights as a way to protect communications over social networking platforms. Because social scientists have recognized that these relationships share the same qualitative structure and can be just as “real” as their face-to-face counterparts, this Article makes the argument that the concept of interpersonal privacy should apply to social networking relationships over the Internet. This analysis provides a new way to apply the reasonable expectation of privacy test under the Fourth Amendment—one that avoids the common pitfalls associated with the Third Party Doctrine

Computer Law Institute

Materials from the Computer Law Institute held by UK/CLE in May 1999

Advances in Data Mining Knowledge Discovery and Applications

Advances in Data Mining Knowledge Discovery and Applications aims to help data miners, researchers, scholars, and PhD students who wish to apply data mining techniques. The primary contribution of this book is highlighting frontier fields and implementations of the knowledge discovery and data mining. It seems to be same things are repeated again. But in general, same approach and techniques may help us in different fields and expertise areas. This book presents knowledge discovery and data mining applications in two different sections. As known that, data mining covers areas of statistics, machine learning, data management and databases, pattern recognition, artificial intelligence, and other areas. In this book, most of the areas are covered with different data mining applications. The eighteen chapters have been classified in two parts: Knowledge Discovery and Data Mining Applications