Blockchain Papers

Gloria Yang Yu, Jinyuan Zhang

No abstract is available for this record.

Damiano Azzolini, Fabrizio Riguzzi, Evelina Lamma, Elena Bellodi · 5 authors

Bitcoin is one of the first decentralized, peer to peer, payment systems based on the so-called Proof-of-Work (PoW). PoW is an algorithm that requires the computation of a hard function in order to gain access to a resource but, at the same time, the correctness of the computed result should be easily checked. The use of a PoW removes the necessity of a centralized third party and so the consistency of the network may be altered directly by the involved users. Peers, to solve the PoW more efficiently, usually organize themselves into mining pools, to increase the overall computational power: this situation, unfortunately, leads to a network centralization. In this paper we consider two typical scenarios of a Bitcoin network and we model them by probabilistic logic programming (PLP): the centralization of the hashing power by large pools and the “double spending attack”. In the first one, we verify the effectiveness of a protocol that attempts to discourage the formation of large pools. In the second one, we compute the probability of success of an attacker. Both scenarios are modeled using the PLP package cplint.

Andrew L. Detzel, Hong Liu, Jack Strauss, Guofu Zhou · 5 authors

No abstract is available for this record.

Alexander Dickerson

No abstract is available for this record.

Jens Röwekamp

The scandal around Facebook and Cambridge Analytica in 2017 showed drastically that new concepts to share andstore information need to be developed in order to minimize the huge potential for abuse resulting from centralized information stored at trusted third parties. This thesis analysed to what degree current document exchange systems (e.g. Dropbox) comply with the information security services confidentiality, integrity, privacy, anonymity, authenticity of authors, non-repudiation, and accountability; with the result that all analysed systems lack support for privacy and anonymity. Mainly due to their centralized design, missing (meta)data encryption, and regulations of jurisdictions in which they operate. Based on that analysis a decentralized concept for document sharing in a peer-to-peer fashion utilising client-side encryption, the separation of data and metadata, metadata masking through Tor hidden services, and distributed ledger technology for directory service provision, was developed. The concept was proven through prototype implementation of a document exchange software called docShare and its information security services were compared with former analysed exchange technologies. The analysis showed that docShare has a better information security service provision but is still leaking identity information in form of IPad dresses when interacting with the distributed ledger Ethereum. Mainly because Ethereum doesn’t support traffic anonymization through Tor.

Weiqi Dai, Jun Deng, Qinyuan Wang, Changze Cui · 6 authors

Due to the increasing total value of the digital currency, the security of encryption wallet is becoming more and more important. The hardware-based wallet is safe, but it is inconvenient because users need to carry an additional physical device, the software-based wallet is convenient, but the safety cannot be guaranteed. All these wallets need to synchronize the blockchain, while most current mobile devices do not have the capability to store all blocks. To solve these problems, mobile devices can use simplified payment verification (SPV). Nevertheless, in existing methods, there is no good way to protect the verification process of the transaction. In this paper, we design a secure blockchain lightweight wallet based on Trustzone to protect SPV. It is more portable compared with the hardware wallet, and safer than the software wallet. Through the isolation, it can also protect the private key and the wallet's address from being stolen by the attackers no matter whether the Rich OS is malicious or not. Meanwhile, it can protect the verification process by verifying transactions in the secure execution environment (SEE), and keep the local block headers unreadable directly from the Rich OS through encryption. We deploy it on the RASPBERRY PI 3 MODEL B development board. The result of the experiment shows that it has little impact on the system.

Danushka Jayasinghe, Sheila Cobourne, Konstantinos Markantonakis, Raja Naeem Akram · 5 authors

No abstract is available for this record.

Claus Pahl, Nabil El Ioini, Sven Helmer

No abstract is available for this record.

Mahawuya Kabuye

No abstract is available for this record.

André Luis Leite F. Sales, Flávio Fernandes Fontes, Silvio Yasui

Even though "militancy" is frequently used in scientifi c literature and in the daily life of parties and social movements, there are few defi nitions of the term. Our goal is to convert the idea of militancy into a research problem. A Brazilian scientifi c literature review shows that the term is used either as an adjective, either as a noun. We conceptualize militancy as a methodology to produce collective action aiming to intervene, or to interfere, in current social norms. This methodology focuses on organizations such as parties and unions, characterized by strict discipline that aims to produce docility, commitment, and obeisance. Then, we show how New Social Movements (NSM) have created unconventional tactics and organizations, offering an alternative to the militant methodology. Organizing teams using horizontal arrangements, operating with decentralized and autonomous networks, recognizing the diversity of its participants, NSM are occupying the streets and reinventing the repertoires of collective action and protest. We suggest the use of the word "activism" to describe this methodology. By distinguishing militancy from activism we wish to re(frame) some problems in the Brazilian scene of political engagement and protest.

Zvika Brakerski, Nico Döttling

No abstract is available for this record.

Craig Calcaterra, Wulf A. Kaal, Gopinath Sivalingam

No abstract is available for this record.

Венелин Терзиев, Stefcho Bankov, Мarin Georgiev

In its jurisprudence the Court of Justice of the European Union (CJEU) has changed its approach towards the purely internal situation rule applicable in the context of the market freedoms. From the 1990s onwards the Court has showed a greater leniency in accepting that certain cases fall within the scope of Union law, as compared to in the years before. This has been done in various ways, depending on the specific fundamental freedom at stake in the case, but always resulted in a relaxing of the fulfilment of the test used for determining whether a case falls within the scope of a market freedom - the linking factor test. More specifically, the Court seems to be accepting that hypothetical future scenarios are sufficient to bring a case within the scope of EU law even though the underlying facts of the case do not satisfy the test, or even to rule in cases which clearly do not fulfil some of the conditions of the test. The overall change of approach towards the purely internal rule can also be seen in an issue of jurisdiction, and not scope, which is still however relevant. This is the fact that the Court has begun issuing preliminary reference rulings in purely internal cases whereby the question referred is in reality hypothetical. It will be claimed that the CJEU does so without requiring sufficient proof by the domestic court that an EU law interpretation is required.

Anna Marchuk

Introduction.The objective reason for the existence of an institution of local budgets is an increase in the efficiency of the provision of public services guaranteed by the state due to the proximity of such services to the immediate consumer. This process is based on the principle of subsidiarity, requires a sufficient level of financial security of local budgets and demonstrates the basic idea of the concept of fiscal decentralization. The decentralization reform is systematic and involves structural changes in various spheres of public life. The object of research of this article is the impact of changes in tax and budget laws aimed at decentralization on structure and dynamics of income and expenditures of local budgets. Purpose.The purpose of the article is to identify trends, priorities and unresolved issues in financing local budget expenditures, compare dynamics of expenditures with dynamics and structural changes in local budget revenues. Results. In the course of the research, the expenditures and revenues of local budgets of Ternopil region during 2004-2017 were analysed, comparison with trends in Ukraine was made. It has been established that due to slowed down economic growth and a systematic decrease in the share of own revenues in recent years, the amount of funding for institutions and activities in the social and cultural sphere has been reduced and the transfer of important functions to the local level was not accompanied by the transfer of sufficient amount of financial resources. Conclusions.The strategic goal of decentralization is to ensure the availability and proper quality of public services for all categories of the population. The decentralized budget system should function on the basis of a coordinated, unified national cooperation policy for many independent institutions, each of which has a legislatively defined sphere of autonomy. Since tax revenues form the main volume of own revenues of local budgets, the issue of improving the efficiency of tax administration comes to the forefront in the context of decentralization changes. Therefore, on the way to ensuring the increase of tax revenues, the strategic goal of local authorities should be to promote economic development of regions.

Jérémy Charlier, Radu State, Jean Hilger

Background: Past few months have seen the rise of blockchain and cryptocurrencies. In this context, the Ethereum platform, an open-source blockchain-based platform using Ether cryptocurrency, has been designed to use smart contracts programs. These are self-executing blockchain contracts. Due to their high volume of transactions, analyzing their behavior is very challenging. We address this challenge in our paper. Methods: We develop for this purpose an innovative approach based on the non-negative tensor decomposition Paratuck2 combined with long short-term memory. The objective is to assess if predictive analysis can forecast smart contracts activities over time. Three statistical tests are performed on the predictive analytics, the mean absolute percentage error, the mean directional accuracy and the Jaccard distance. Results: Among dozens of GB of transactions, the Paratuck2 tensor decomposition allows asymmetric modeling of the smart contracts. Furthermore, it highlights time dependent latent groups. The latent activities are modeled by the long short term memory network for predictive analytics. The highly accurate predictions underline the accuracy of the method and show that blockchain activities are not pure randomness. Conclusion: Herein, we are able to detect the most active contracts, and predict their behavior. In the context of future regulations, our approach opens new perspective for monitoring blockchain activities.

Jesús Fernández‐Villaverde

Abstract This article reviews what cryptocurrencies are, and it frames them within the context of historical monetary experiences and contemporary monetary economics. The article argues that, as pure fiduciary private money, cryptocurrencies are a bubble without a fundamental value and they will not provide, in general, optimal amounts of money or deliver price stability. Nevertheless, cryptocurrencies can play a role in improving the current means of payments and in disciplining central banks into providing better government‐run fiduciary monies.

Jesús Fernández‐Villaverde

Advocates of cryptocurrencies such as Bitcoin believe that having currency competition will help achieve the economic objective of price stability. This Issue Brief summarizes research that explores whether competition among privately issued fiat currencies can actually produce price stability. The research finds that in most cases, a system of private monies does not deliver price stability. And even when it does, it always is subject to self-fulfilling inflationary episodes, and it supplies a suboptimal amount of money. Although there is no economic reason to curb the use of cryptocurrencies at the moment, it is important to review key regulatory issues that policymakers need to consider now, before the use of cryptocurrencies becomes even more widespread.

Engin Iyidogan

No abstract is available for this record.

Yanqi Zhao, Yannan Li, Qilin Mu, Bo Yang · 5 authors

The cyber physical system (CPS) has gained considerable success in large-scale distributed integration environment. In such systems, the sensor devices collect data which would be disseminated via reliable manner to all interested co-operant entities from the physical world. However, highly unreliable environment of CPS, for example, a number of limitations of existing network middle wares, makes secure and reliable data distribution services a challenge issue. In this paper, we propose a new architecture called secure pub-sub (SPS) without middle ware, i.e., blockchain-based fair payment with reputation. In SPS, publishers publish a topic on the blockchain and subscribers specify an interest message by making a deposit to subscribing the topic. Then, if the interest message matches the topic, the publisher transmits the encrypted content of the topic to the blockchain such that the subscribers can decrypt the ciphertext to obtain the content, and mark the publisher as its reputation. Finally, the publisher receives the payment from the subscriber. The new proposal provides confidentiality and reliability of data, anonymity of subscribers and payment fairness between the publishers and subscribers. Different from the traditional pub-sub services, no trusted third party is involved in our system due to employing blockchain technique. The security of the proposed SPS is analyzed as well. The implementation of the protocol on Ethereum of smart contract demonstrates the validity of SPS.

Sergey Avdoshin, Vladimir A. Lazarenko

Bitcoin is the most popular cryptocurrency on the planet. It relies on strong cryptography and peer-to-peer network. Bitcoin is gaining more and more popularity in criminal society. That is why Bitcoin is often used as money laundering tool or payment method for illegal products and services. In this paper we explore various methods for Bitcoin users deanonimization, which is an important task in anti-money laundering process and cybercrime investigation.

Stefano Colucci

No abstract is available for this record.

Sandi Rahmadika, Kyung-Hyune Rhee

The personal health information (PHI) is an activity among the health-care providers and the patients in terms of managing the data which is sensitive to the parties. The PHI data have been maintained by multiple health-care providers, thus resulting in separated data. Moreover, the PHI data are stored in the provider’s database, hence the patients have no authority to manage their own information. Therefore, in this article, we propose a conceptual model for managing the PHI data which is derived from several health-care providers by relying on the blockchain technology in the peer-to-peer overlay network. In addition, we elaborate the security analysis that might be occurring in the proposed model. By leveraging on our model, it allows the patients and the providers to collect effectively the PHI data onto a single view as well guarantee of data integrity. The blockchain offers an immutable of the data record without having to trust a third party. The experimental results show that the proposed approach is promising to be developed due to the high success rate in terms of data dissemination.

Gilbert Fridgen, Sven Radszuwill, Nils Urbach, Lena Utz

Bringing Blockchain technology and business process management together, we follow the Design Science Research approach and design, implement, and evaluate a Blockchain prototype for cross-organizational workflow management together with a German bank. For the use case of a documentary letter of credit we describe the status quo of the process, identify areas of improvement, implement a Blockchain solution, and compare both workflows. The prototype illustrates that the process, as of today paper-based and with high manual effort, can be significantly improved. Our research reveals that a tamper-proof process history for improved auditability, automation of manual process steps and the decentralized nature of the system can be major advantages of a Blockchain solution for cross-organizational workflow management. Further, our research provides insights how Blockchain technology can be used for business process management in general.

Yunru Zhang, Debiao He, Kim‐Kwang Raymond Choo

Internet of Things (IoT) and cloud computing are increasingly integrated, in the sense that data collected from IoT devices (generally with limited computational and storage resources) are being sent to the cloud for processing, etc., in order to inform decision making and facilitate other operational and business activities. However, the cloud may not be a fully trusted entity, like leaking user data or compromising user privacy. Thus, we propose a privacy‐preserving and user‐controlled data sharing architecture with fine‐grained access control, based on the blockchain model and attribute‐based cryptosystem. Also, the consensus algorithm in our system is the Byzantine fault tolerance mechanism, rather than Proof of Work.