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93,175 results · page 3603 of 3,883
Aggelos Kiayias, Thomas Zacharias, Bingsheng Zhang
No abstract is available for this record.
Yuval Ishai, Mor Weiss, Guang Yang
A Probabilistically Checkable Proof (PCP) allows a randomized verifier, with oracle access to a purported proof, to probabilistically verify an input statement of the form âx â L â by querying only few bits of the proof. A zero-knowledge PCP (ZKPCP) is a PCP with the additional guarantee that the view of any verifier querying a bounded number of proof bits can be efficiently simulated given the input x alone, where the simulated and actual views are statistically close. Originating from the first ZKPCP construction of Kilian et al. (STOC â97), all previous constructions relied on locking schemes, an unconditionally secure oracle-based commitment primitive. The use of locking schemes makes the verifier inherently adaptive, namely, it needs to make at least two rounds of queries to the proof. Motivated by the goal of constructing non-adaptively verifiable ZKPCPs, we suggest a new technique for compiling standard PCPs into ZKPCPs. Our approach is based on leakage-resilient circuits, which are circuits that withstand certain âside-channel â attacks, in the sense that these attacks reveal nothing about the (properly encoded) input, other than the output. We observe that the verifierâs oracle queries constitute a side-channel attack on the wire-values of the circuit
Xiaoju Liu
The corresponding technologies for sharing information and 3Dinteraction by Web3 D were described briefly.An efficient scene management scheme for real-time visualization of a large-scale underground scene was proposed to meet its demands for webpage visualization.Firstly,the raw data from the underground scene were preprocessed in lightweight,and a shell structure-aware scene analysis algorithm was employed for constructing a scene management structure.Then,some strategies were put forward according to the characteristics of the underground scene data,and those are a SOI-ExteriorShell strategy based on Sector Of Interest(SOI)management for outdoor scenes and a Portal-InteriorShell strategy supporting progressive loading for indoor ones.With the switch between indoor and outdoor scenes,the method dynamically chooses the corresponding strategy and makes it possible to roam in the large-scale underground scene online.From the final experiment,it concludes that the proposed method efficiently culls unnecessary scenes in a greatly large extent and is capable of meeting the requirements for real-time visualization of the large-scale underground scene over Internet.As the webpage has an advantage of cross-platform,the system supports users to roamand control the large-scale underground scene under cross-platform.
Alex Biryukov, Daniel Dinu, Dmitry Khovratovich
Memory-hard functions are becoming an important tool in the design of password hashing schemes, cryptocur-rencies, and more generic proof-of-work primitives that are x86-oriented and can not be computed on dedicated hardware more efficiently. We develop a simple and cryptographically secure approach to the design of such functions and show how to exploit the architecture of modern CPUs and memory chips to make faster and more secure schemes compared to existing alternatives such as scrypt. We also propose cryptographic criteria for the components, that prevent cost reductions using time-memory tradeoffs and side-channel leaks. The concrete proof-of-work instantiation, which we call Argon2, can fill GBytes of RAM within a second, is resilient to various tradeoffs, and is suitable for a wide range of applications, which aim to bind a computation to a certain architecture. Concerning potential DoS attacks, our scheme is lightweight enough to offset the bottleneck from the CPU to the memory bus thus leaving sufficient computing power for other tasks. We also propose parameters for which our scheme is botnet resistant. As an application, we suggest a cryptocurrency design with fast and memory-hard proof-of-work, which allows memoryless verification. 1
Ramesh Subramanian, Theo Chino
This paper focuses on the evolution of cryptocurrencies. It traces the history of early cryptography, the âcypherpunkâ movement, and how the work of some cyber libertarians and cryptographers enabled the emergence of popular cryptocurrencies. The paper then focuses on Bitcoin. It delves into the technology behind the Bitcoin architecture and shows how exactly this technology works. The paper then does an analysis of security and regulatory considerations that affect the growth of Bitcoin-based businesses. The paper concludes with some suggestions for future work in the area.
Syed Taha Ali
No abstract is available for this record.
Nicolas T. Courtois, Pinar Emirdag, Zhouyixing Wang
In this paper we study the question of centralisation in bitcoin digital currency. In theory bitcoin has been designed to be a totally decentralized distributed system. Satoshi Nakamoto has very clearly postulated that each node should be collecting recent transactions and trying to create new blocks (Satoshi08). In bitcoin transactions are aggregated in block in order to authenticate them and form an official ledger and history of bitcoin transactions. In practice as soon as expensive ASIC bitcoin miners have replaced general-purpose hardware, production of bitcoins and the validation of transactions has concentrated in the hands of a smaller group of people. Then at some moment in early 2012 an important decision was taken: the Stratum protocol was designed (Palatinus12) which took a deliberate decision to move the power of selecting which transactions are included in blocks from miners to pool managers. The growing difficulty of mining and large standard deviation in this process (Rosenfeld13; CourtoisBahack14) made that majority of miners naturally shifted to pooled mining. At this moment bitcoin ceased being a decentralized democratic system. In this paper we survey the question of a 51% attacks and show that there is a large variety of plausible attack scenarios. In particular we study one particularly subversive attack scenario which depends on non-trivial internal details of the bitcoin hashing process. How does it compare with the current mining practices? We have study the Stratum protocol in four popular real-life mining configurations. Our analysis shows that pools could very easily cheat the majority of people. However the most subversive versions of the attack are NOT facilitated and could potentially be detected.
Yoad Lewenberg, Yonatan Sompolinsky, Aviv Zohar
No abstract is available for this record.
Filipe Drebes Scarinci
Os mais diversos sistemas monetĂĄrios foram experimentados pela socidade atĂ© chegarmos no modelo atual e hĂĄ poucos indĂcios de que este deva ser o Ășltimo e definitivo. Existe uma insatisfação com o sistema vigente e com o grande poder que as autoridades monetĂĄrias adquiriram nos Ășltimos anos. Novos modelos vĂȘm surgindo nas mais diversas ĂĄreas, e uma das alternativas que se desenha para o arranjo financeiro Ă© o Bitcoin, um sistema monetĂĄrio completamente descentralizado, que se utiliza da tecnologia pessoa-a-pessoa para transformar o modo como os indivĂduos se relacionam. O trabalho se propĂ”e a analisar a origem, as caracterĂsticas, o funcionamento e as inovaçÔes trazidas pelo sistema Bitcoin, comparando a criptomoeda Ă s outras moedas tradicionais estudadas na literatura econĂŽmica. Em especial, trata de analisar a factibilidade do Bitcoin enquanto moeda.
Yunyoung Hur, Seongmin Jeon, Byungjoon Yoo
Ever since its creation by the presumed pseudonymous Satoshi Nakamoto, Bitcoin has garnered significant attention as an innovative online payment system. The purpose of this paper is to discover the degree to which the participation of a Bitcoin user is dependent on the speculative opportunities in the Bitcoin market and, accordingly, to test Bitcoinâs competence against traditional currency. Using a panel data set from one of the largest Bitcoin traders in Asia, we find that $1 increase in arbitrage between market prices is associated with 0.1 more log-ins of users. However, the paper also suggests that such a speculative nature might not be strong enough to dominate user behaviors entirely. The findings report that the actual reason for Bitcoinâs incompetence as a form of currency against the conventional tools of trade may be attributable to its low level of network effects.
Gaby G. Dagher, Benedikt BĂŒnz, Joseph Bonneau, Jeremy Clark · 5 authors
Bitcoin exchanges function like banks, securely holding their cus-tomers â bitcoins on their behalf. Several exchanges have suffered catastrophic losses with customers permanently losing their sav-ings. A proof of solvency demonstrates that the exchange controls sufficient reserves to settle each customerâs account. We introduce Provisions, a privacy-preserving proof of solvency whereby an ex-change does not have to disclose its Bitcoin addresses; total hold-ings or liabilities; or any information about its customers. We also propose an extension which prevents exchanges from colluding to cover for each otherâs losses. We have implemented Provisions and it offers practical computation times and proof sizes even for a large Bitcoin exchange with millions of customers.
Ignacio MĂĄs, David Lee Kuo Chuen
No abstract is available for this record.
Tetsuya Saito
No abstract is available for this record.
Benedikt C. Eikmanns, Philipp Sandner
Despite a high volatility and the recent fall in price, more and more merchants and consumers adopt Bitcoin. The virtual currency might be standing at its critical point to reach the early majority of adopters. This paper examines whether an application called ChangeTip has the potential to catalyze the breakthrough of Bitcoin. We assume a strong linkage between the diffusion of ChangeTip and Bitcoin so that we can directly deduce the impact of this application on Bitcoin. Results from a conducted online survey of 210 potential early adopters indicate that the diffusion of ChangeTip has the potential to advance the diffusion of Bitcoin to mainstream markets. We found that performance expectancy is the key driver for the intention to recommend ChangeTip. Also, effort expectancy, social influence and facilitating conditions are important factors for recommending ChangeTip. Concerning the intention to use ChangeTip in the future, performance expectancy and social influence are the main drivers. Furthermore, facilitating conditions are important for using ChangeTip. In addition, an analysis of the non-user of Bitcoin and ChangeTip was conducted. Theoretical and practical implications of these results are discussed.
Gianluca Miscione, Donncha Kavanagh
No abstract is available for this record.
Rafail Ostrovsky, Alessandra Scafuro, Muthuramakrishnan Venkitasubramanian
No abstract is available for this record.
Thomas GroĂ
No abstract is available for this record.
Ruslana Bilyk
The paper studies issues of strengthening the financial basis of regional development as a component of economic security policy and one of the most important areas of administrative decentralization in Ukraine. Main problems of regional development financing identified, ineffectiveness of inter-budget relations proved and the obstacles for accumulation of financial resources of local communities determined. It has been shown that main consequence of regional financial âweaknessâ was the inability to concentrate resources for prior investment projects and activities of regional development. The measures for strengthening of the financial security of regions in the context of regional policy objectives and according to the announced decentralization and fiscal reforms in regions offered. It is proved that for strengthening the financial base of support for regional development and ensuring self-sufficiency of territorial communities, in terms of the objectives of the new regional policy, it is necessary: to gradually expand the list of instruments used by local authorities to increase the amount of cool tools; disseminate program-target method of compilation and execution of local budgets with the aim of increasing transparency and efficiency of use of budgetary funds; to organize intergovernmental relations, to increase the share of targeted funding, to ensure the formation of horizontal intergovernmental relations; to provide for the expansion of the revenue base of local budgets, transfer of shares separate national taxes, the search for extra-budgetary financial resources.
Liam Morris
Cash in the real world allows for parties to exchange currency without the need to go through some sort of central authority. One person, Alice, can simply hand cash over to another person, Bob. In this transaction the only two people that have knowledge of this exchange are Alice and Bob. Until recently there was no electronic equivalent to this exchange. In 1982 David Chaum proposed a system of anonymous electronic cash based on blind signatures, and in 1990 founded DigiCash as an electronic cash company. There were a few banks that implemented electronic cash systems, but these banks and DigiCash ultimately went bankrupt in 1997 and 1998 despite the enthusiasm surrounding anonymous electronic cash. Between 1998 and 2008 there were no successful implementations of electronic cash that offer a decentralized, anonymous, and untraceable system.\nIn 2008 a paper was published by Satoshi Nakamoto on the cryptocurrency known as Bitcoin. A cryptocurrency is a form of electronic cash backed by mathematical and cryptographic constructs, unlike traditional currency which was historically backed by gold or silver. Cryptocurrencies have seen rising popularity in recent years due to their decentralized, distributed, peer-to-peer protocols. Part of this rising popularity is also attributable to the supposed anonymity of these protocols; however, due to the public transaction history required for these protocols and the fact that transactions are pseudonymous and not purely anonymous, this supposed anonymity does not exist. While the systems may achieve the goal of decentralized currency it does not achieve the goal of untraceability. In this thesis we analyze the technical implementations of Bitcoin and other cryptocurrencies to determine the level of anonymity provided by these protocols. We also analyze proposed improvements for their feasibility.
J.A. Bergstra
Six assertions concerning the status of Bitcoin are formulated and defended: (i) Bitcoin is not and will not become a currency-like informational commodity, (ii) currency-like informational commodities that arenât currencies must be frauds, (ii) specific BTC amounts may become monetized and thus may be turned into financial assets, (iii) currently no BTC amounts are monetized in any currency area and therefore none are financial assets, (iv) by means of burocratic steps only some BTC volumes can be turned in to an informational currency within a given currency area, modified client software is not required for that step, (v) if a specific amount of BTC qualifies as currency, it also qualifies as money, (vi) moneyness of Bitcoin, or rather of a specific occurrence of an amount of BTC, should be questioned only after one has agreed positively on its status as a financial asset, and negatively on its status as an amount of currency. Factions in the Bitcoin promoting movement are viewed from a perspective of organizational multi-threading. Different factions of the Bitcoin movement may wish to see status issues about Bitcoin settled in different ways. Overall consistency in these matters should not be expected from the union of factions in the Bitcoin movement.
Daniel Folkinshteyn, Mark M. Lennon, Tim Reilly
No abstract is available for this record.
Pasquale Forte, Diego Romano, Giovanni Schmid
After more than six years from the launch of Bitcoin, it has become ev-ident that the decentralized transaction ledger functionality implemented through the blockchain technology can be used not only for cryptocur-rencies, but to register, confirm and transfer any kind of contract and property. In this work we analyze the most relevant functionalities and known issues of this technology, with the intent of pointing out the pos-sible behaviours that are not as efficient as they should when thinking with a broader outlook. Our analysis would be the starting point for the introduction of a new approach to blockchain creation and management, which will be the subject of a forthcoming paper. 1
Nirupama Devi Bhaskar, Lam Pak Nian, David Lee Kuo Chuen
No abstract is available for this record.
Hanna HaĆaburda, MiklĂłs SĂĄrvĂĄry
No abstract is available for this record.