Dumitrel Loghin, Gang Chen, Tien Tuan Anh Dinh, Beng Chin Ooi · 5 authors
Motivated by the massive energy usage of blockchain, on the one hand, and by significant performance improvements in low-power, wimpy systems, on the other hand, we perform an in-depth time-energy analysis of blockchain systems on low-power nodes in comparison to high-performance nodes. We use three low-power systems to represent a wide range of the performance-power spectrum, while covering both x86/64 and ARM architectures. We show that low-end wimpy nodes are struggling to run full-fledged blockchains mainly due to their small and low-bandwidth memory. On the other hand, wimpy systems with balanced performance-to-power ratio achieve reasonable performance while saving significant amounts of energy. For example, Jetson TX2 nodes achieve around 80% and 30% of the throughput of Parity and Hyperledger, respectively, while using 18x and 23x less energy compared to traditional brawny servers with Intel Xeon CPU.
BACKGROUND: Nowadays, a number of mechanisms and tools are being used by health care organizations and physicians to electronically exchange the personal health information of patients. The main objectives of different methods of health information exchange (HIE) are to reduce health care costs, minimize medical errors, and improve the coordination of interorganizational information exchange across health care entities. The main challenges associated with the common HIE systems are privacy concerns, security risks, low visibility of system transparency, and lack of patient control. Blockchain technology is likely to disrupt the current information exchange models utilized in the health care industry. OBJECTIVE: Little is known about patients' perceptions and attitudes toward the implementation of blockchain-enabled HIE networks, and it is still not clear if patients (as one of the main HIE stakeholders) are likely to opt in to the applications of this technology in HIE initiatives. Thus, this study aimed at exploring the core value of blockchain technology in the health care industry from health care consumers' views. METHODS: To recognize the potential applications of blockchain technology in health care practices, we designed 16 information exchange scenarios for controlled Web-based experiments. Overall, 2013 respondents participated in 16 Web-based experiments. Each experiment described an information exchange condition characterized by 4 exchange mechanisms (ie, direct, lookup, patient-centered, and blockchain), 2 types of health information (ie, sensitive vs nonsensitive), and 2 types of privacy policy (weak vs strong). RESULTS: The findings show that there are significant differences in patients' perceptions of various exchange mechanisms with regard to patient privacy concern, trust in competency and integrity, opt-in intention, and willingness to share information. Interestingly, participants hold a favorable attitude toward the implementation of blockchain-based exchange mechanisms for privacy protection, coordination, and information exchange purposes. This study proposed the potentials and limitations of a blockchain-based attempt in the HIE context. CONCLUSIONS: The results of this research should be of interest to both academics and practitioners. The findings propose potential limitations of a blockchain-based HIE that should be addressed by health care organizations to exchange personal health information in a secure and private manner. This study can contribute to the research in the blockchain area and enrich the literature on the use of blockchain in HIE efforts. Practitioners can also identify how to leverage the benefit of blockchain to promote HIE initiatives nationwide.
About a decade ago the fundamental operating principle of the Blockchain was introduced. It took several years before the technology gained widespread recognition in industry and academic communities outside of the computer science sphere. Since then many academic communities have taken up the topic, but so far no well-defined research agenda has emerged: research topics are scattered and rigorous approaches are scarce. More often than not, use cases implemented by industry apply a trial and error approach and there exists a dearth of theory-based academic papers on the topic following robust methodologies. Being a nascent research topic, case studies on Blockchain applications are a suitable approach to systematically transfer industry experience into research agendas which benefit both theory development and testing as well as design science research. In this paper I offer guidelines and suggestions on how to design and structure Blockchain case studies to create value for academia and the industry. More specifically, I describe Blockchain characteristics and challenges, present existing Blockchain case studies, and discuss various types of case study research and how they can be useful for industry and academic research. I conclude with a framework and a checklist for Blockchain case study research.
Abstract This article investigates the twofold impact that blockchain technologies and smart contracts have on dispute resolution. On the one hand, these technologies enable private parties to devise arbitral systems that are self-enforcing and, therefore, largely bypass the recognition and enforcement procedures through which State courts traditionally exert a certain control over arbitration. This phenomenon may in the future allow arbitration to become entirely self-sufficient, thus leading to the marginalization of State courts. On the other hand, however, such a marginalization has not taken place yet; to the contrary, the recent blockchain-related phenomenon of initial coin offerings has given rise to some prominent court cases. These cases raise particularly interesting jurisdictional questions, especially in light of the difficulty of reconciling the decentralized nature of the blockchain with the territorial approach whereby jurisdiction is typically allocated among national courts.
In this paper we propose and analyze a community-driven platform for flexibility provision based on a distributed ledger. We introduce and analyze the platform for the use case of a self-organized decentralized virtual power plant consisting of a local community of individual prosumers with photovoltaic-storages located on a low voltage feeder. Like a virtual power plant, it aggregates small-scale assets and is able to provide ancillary services in the form of active power provision to the electrical power system. However, the decentralized virtual power plant provides a direct flexibility market access of the distributed assets without the need for a third party. Thus, balancing group managers or system operators can directly interact with the distributed assets in an aggregated way without the need for an aggregator. The solution approach uses a heuristic algorithm for the coordination combined with a distributed ledger and democratic consensus within the community. We propose the concept in detail, describe the prototypical implementation based on a consortium Ethereum blockchain and discuss results of the proof-of-concept. Our numerous test runs with up to 20 participants showed that the coordinated flexibility provision, energy sharing and according financial settlement works in practice, but would need an upgrade concerning the smart-meter hardware for an implementation in the field. We analyze the impact of the coordination interval on the community self-sufficiency and determine that one minute intervals are enough to reach 96% of the optimum. We evaluate the storage and communication effort and conclude with suggestions for future improvements and other possible applications of the decentralized platform like aggregated flexibility coordination between balancing group managers and system operators.
Afiya Ayman, Shanto Roy, Mohammad Amin Alipour, Áron Lászka
Blockchain-based platforms are emerging as a transformative technology that can provide reliability, integrity, and auditability without trusted entities. One of the key features of these platforms is the trustworthy decentralized execution of general-purpose computation in the form of smart contracts, which are envisioned to have a wide range of applications. As a result, a rapidly growing and active community of smart-contract developers has emerged in recent years. A number of research efforts have investigated the technological challenges that these developers face, introducing a variety of tools, languages, and frameworks for smart-contract development, focusing on security. However, relatively little is known about the community itself, about the developers, and about the issues that they face and discuss. To address this gap, we study smart-contract developers and their discussions on two social media sites, Stack Exchange and Medium. We provide insight into the trends and key topics of these discussions, into the developers' interest in various security issues and security tools, and into the developers' technological background.
The wide deployment of tokens for digital assets on top of Ethereum implies the need for powerful trading platforms. Vickrey auctions have been known to determine the real market price of items as bidders are motivated to submit their own monetary valuations without leaking their information to the competitors. Recent constructions have utilized various cryptographic protocols such as ZKP and MPC, however, these approaches either are partially privacy-preserving or require complex computations with several rounds. In this paper, we overcome these limits by presenting Trustee as a Vickrey auction on Ethereum which fully preserves bids' privacy at relatively much lower fees. Trustee consists of three components: a front-end smart contract deployed on Ethereum, an Intel SGX enclave, and a relay to redirect messages between them. Initially, the enclave generates an Ethereum account and ECDH key-pair. Subsequently, the relay publishes the account's address and ECDH public key on the smart contract. As a prerequisite, bidders are encouraged to verify the authenticity and security of Trustee by using the SGX remote attestation service. To participate in the auction, bidders utilize the ECDH public key to encrypt their bids and submit them to the smart contract. Once the bidding interval is closed, the relay retrieves the encrypted bids and feeds them to the enclave that autonomously generates a signed transaction indicating the auction winner. Finally, the relay submits the transaction to the smart contract which verifies the transaction's authenticity and the parameters' consistency before accepting the claimed auction winner. As part of our contributions, we have made a prototype for Trustee available on Github for the community to review and inspect it. Additionally, we analyze the security features of Trustee and report on the transactions' gas cost incurred on Trustee smart contract.
Yifan Yang, Daniel Cooper, John Collomosse, Constantin C. Drăgan · 10 authors
We present a novel blockchain based service for proving the provenance of online digital identity, exposed as an assistive tool to help non-expert users make better decisions about whom to trust online. Our service harnesses the digital personhood (DP); the longitudinal and multi-modal signals created through users' lifelong digital interactions, as a basis for evidencing the provenance of identity. We describe how users may exchange trust evidence derived from their DP, in a granular and privacy-preserving manner, with other users in order to demonstrate coherence and longevity in their behaviour online. This is enabled through a novel secure infrastructure combining hybrid on- and off-chain storage combined with deep learning for DP analytics and visualization. We show how our tools enable users to make more effective decisions on whether to trust unknown third parties online, and also to spot behavioural deviations in their own social media footprints indicative of account hijacking.
Marten Sigwart, Michael Borkowski, Marco Peise, Stefan Schulte · 5 authors
As more and more applications and services depend on data collected and provided by Internet of Things (IoT) devices, it is of importance that such data can be trusted. Data provenance solutions together with blockchain technology are one way to make data more trustworthy. However, current solutions do not address the heterogeneous nature of IoT applications and their data. In this work, we identify functional and non-functional requirements for a generic IoT data provenance framework, and conceptualise the framework as a layered architecture. Using a proof-of-concept implementation based on Ethereum smart contracts, data provenance can be realised for a wide range of IoT use cases. Benefits of a generic framework include simplified adoption and a more rapid implementation of data provenance for the IoT.
Tin Leelavimolsilp, Long Tran-Thanh, Sebastian Stein, Viet Hung Nguyen
Proof-of-Work blockchain, despite its numerous benefits, is still not an entirely secure technology due to the existence of Selfish Mining (SM) strategies that can disrupt the system and its mining economy. While the effect of SM has been studied mostly in a two-miners scenario, it has not been investigated in a more practical context where there are multiple malicious miners individually performing SM. To fill this gap, we carry out an empirical study that separately accounts for different numbers of SM miners (who always perform SM) and strategic miners (who choose either SM or Nakamoto's mining protocol depending on which maximises their individual mining reward). Our result shows that SM is generally more effective as the number of SM miners increases, however its effectiveness does not vary in the presence of a large number of strategic miners. Under specific mining power distributions, we also demonstrate that multiple miners can perform SM and simultaneously gain higher mining rewards than they should. Surprisingly, we also show that the more strategic miners there are, the more robust the systems become. Since blockchain miners should naturally be seen as self-interested strategic miners, our findings encourage blockchain system developers and engineers to attract as many miners as possible to prevent SM and similar behaviour.
Bin Cao, Yixin Li, Lei Zhang, Long Zhang · 7 authors
Blockchain has been regarded as a promising technology for Internet of Things (IoT), since it provides significant solutions for decentralized network which can address trust and security concerns, high maintenance cost problem, etc. The decentralization provided by blockchain can be largely attributed to the use of consensus mechanism, which enables peer-to-peer trading in a distributed manner without the involvement of any third party. This article starts from introducing the basic concept of blockchain and illustrating why consensus mechanism plays an indispensable role in a blockchain enabled IoT system. Then, we discuss the main ideas of two famous consensus mechanisms including Proof of Work (PoW) and Proof of Stake (PoS), and list their limitations in IoT. Next, two mainstream Direct Acyclic Graph (DAG) based consensus mechanisms, i.e., the Tangle and Hashgraph, are reviewed to show why DAG consensus is more suitable for IoT system than PoW and PoS. Potential issues and challenges of DAG based consensus mechanism to be addressed in the future are discussed in the last.
Matteo Romiti, Aljosha Judmayer, Alexei Zamyatin, Bernhard Haslhofer
Miners play a key role in cryptocurrencies such as Bitcoin: they invest substantial computational resources in processing transactions and minting new currency units. It is well known that an attacker controlling more than half of the network's mining power could manipulate the state of the system at will. While the influence of large mining pools appears evenly split, the actual distribution of mining power within these pools and their economic relationships with other actors remain undisclosed. To this end, we conduct the first in-depth analysis of mining reward distribution within three of the four largest Bitcoin mining pools and examine their cross-pool economic relationships. Our results suggest that individual miners are simultaneously operating across all three pools and that in each analyzed pool a small number of actors (<= 20) receives over 50% of all BTC payouts. While the extent of an operator's control over the resources of a mining pool remains an open debate, our findings are in line with previous research, pointing out centralization tendencies in large mining pools and cryptocurrencies in general.
In this paper, we investigate people’s perception of datafication and surveillance in Amsterdam Smart City. Based on a series of focus groups, we show how people understand new forms of hypervisbility, what strategies they use to navigate these experiences, and what the limitations of these strategies are. We show how people tried to discern between public and private sector actors, to differentiate who they trusted by building on the existing social contract. People also trusted the objectivity of data in relation to prior experiences of social contexts and discrimination. Lastly, we show how the experiences of some of the inhabitants in our study who were most vulnerable to hypervisibility highlight the limits to strategies based on the neutrality of data. By asking about perceived surveillance rather than emphasising actual practices of surveilling, we show differentiated contexts and strategies, providing empirical grounds to question the dominant technical framing of smart cities.
Bitcoin futures were launched by the Chicago Board of Options Exchange and the Chicago Mercantile Exchange group on December 18th, 2017. This study stands as a first attempt to explore the reactions of Bitcoin spot market to the launch of futures contracts. Using an event-study methodology and an adjusted asset pricing model, we show that Futures trading drove up the price of Bitcoin immediately after the announcement day. This reaction started to decrease noticeably following the launch of the futures contracts. Such outcome seems in line with the trading behavior that typically accompanies the launch of futures markets for an asset.
Bitcoin is a Cryptocurrency which is evolving in digital world and gaining a larger market related to digital currency and stands on all the user expectation of decentralize mechanism of system by providing proof of work in peer-to-peer network with the help of Blockchain. In this paper I have done a literature review on Blockchain technology and its application in Bitcoin.
Open access
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
Blockchain-based platforms are emerging as a transformative technology that\ncan provide reliability, integrity, and auditability without trusted entities.\nOne of the key features of these platforms is the trustworthy decentralized\nexecution of general-purpose computation in the form of smart contracts, which\nare envisioned to have a wide range of applications. As a result, a rapidly\ngrowing and active community of smart-contract developers has emerged in recent\nyears. A number of research efforts have investigated the technological\nchallenges that these developers face, introducing a variety of tools,\nlanguages, and frameworks for smart-contract development, focusing on security.\nHowever, relatively little is known about the community itself, about the\ndevelopers, and about the issues that they face and discuss. To address this\ngap, we study smart-contract developers and their discussions on two social\nmedia sites, Stack Exchange and Medium. We provide insight into the trends and\nkey topics of these discussions, into the developers' interest in various\nsecurity issues and security tools, and into the developers' technological\nbackground.\n
Wireless Virtualization (WiVi) is emerging as a new paradigm to provide high speed communications and meet Quality-of-Service (QoS) requirements of users while reducing the deployment cost of wireless infrastructure for future wireless networks. In WiVi, Wireless Infrastructure Providers (WIPs) sublease their RF channels through slicing to Mobile Virtual Network Operators (MVNOs) based on their Service Level Agreements (SLAs) and the MVNOs independently provide wireless services to their end users. This paper investigates the wireless network virtualization by leveraging both Blockchain technology and machine learning to optimally allocate wireless resources. To eliminate double spending (aka over-committing) of WIPs' wireless resources such as RF channels, Blockchain - a distributed ledger - technology is used where a reputation is used to penalize WIPs with past double spending habit. The proposed reputation based approach helps to minimize extra delay caused by double spending attempts and Blockchain operations. To optimally predict the QoS requirements of MVNOs for their users, linear regression - a machine learning approach - is used that helps to minimize the latency introduced due to (multiple wrong) negotiations for SLAs. The performance evaluation of the proposed approach is carried out by using numerical results obtained from simulations. Results have shown that the joint Blockchain and machine learning based approach outperforms the other approaches.
Afiya Ayman, Amna Aziz, Mohammad Amin Alipour, Áron Lászka
Blockchain based platforms are emerging as a transformative technology that can provide reliability, integrity, and auditability without trusted entities. One of the key features of these platforms is the trustworthy decentralized execution of general-purpose computation in the form of smart contracts, which are envisioned to have a wide range of applications from finance to the Internet of Things. As a result, a rapidly growing and active community of smart contract developers has emerged in recent years. A number of research efforts have investigated the technological challenges that smart contract developers face. However, very little is known about the community itself, about the developers, and about the issues that they discuss and care about. To address this gap, we study the online community of smart contract developers on Stack Overflow. We provide insight into the topics that they discuss, their technological and demographic background, and their awareness of security issues and tools. Our results show that the community of smart contract developers is very active and growing rapidly, in comparison with the general user population. However, a large fraction of smart contract related questions remain unanswered, which can pose a real threat to the viability of a sustainable community and may indicate gaps in community knowledge. Further, we observe very limited discussion of security related topics, which is concerning since smart contracts in practice are plagued by security issues.
Daniel Traian Pele, Miruna Mazurencu-Marinescu-Pele
Abstract In this paper the authors investigate the statistical properties of some cryptocurrencies by using three layers of analysis: alpha-stable distributions, Metcalfe’s law and the bubble behaviour through the LPPL modelling. The results show, in the medium to long-run, the validity of Metcalfe's law (the value of a network is proportional to the square of the number of connected users of the system) for the evaluation of cryptocurrencies; however, in the short-run, the validity of Metcalfe’s law for Bitcoin is questionable. According to the bidirectional causality between the price and the network size, the expected price increase is a driver for more investors to join the Bitcoin network, which may lead in the end to a super-exponential price growth, possibly due to a herding behaviour of investors. The authors then used LPPL models to capture the behaviour of cryptocurrencies exchange rates during an endogenous bubble and to predict the most probable time of the regime switching. The main conclusion of this paper is that Metcalfe’s law may be valid in the long-run, however in the short-run, on various data regimes, its validity is highly debatable.
In the present paper, an extension of the Bitcoin (BTC) structure is introduced, with a proprietary and unique DLCC (Digital Learning Chain Structure) blockchain, through which an automated bursary payment system could be constituted, which has, until this day, never been implemented at universities. Thus, an alternative is offered to achieve a bursary payment system, operating in a fully automatic, periodically repeating manner, never requiring supervision. In the DLCC blockchain, specifically, in the Smart Contract, the terms of contract are kept, concerning the bursaries, terms agreed by both parties (students and universities alike). A great advantage of the DLCC system is that it is able to extract the required grades from the electronic grade book, thus supervising the students' progress throughout the semesters. Upon reaching the end of each semester, if the student qualifies, meeting the requirements, the system will transfer the required quantity of cryptocurrency from the university's account automatically to the student's account.
Philipp Frauenthaler, Michael Borkowski, Stefan Schulte
The suitability of a particular blockchain for a given use case depends mainly on the blockchain's functional and non-functional properties. Such properties may vary over time, and thus, a selected blockchain may become unsuitable for a given use case. This uncertainty may hinder the widespread adoption of blockchain technologies in general. To mitigate the impact of volatile blockchain properties, we propose a framework that monitors several blockchains, allows the user to define functional and non-functional requirements, determines the most appropriate blockchain, and enables the switchover to that chain at runtime. Our evaluation using a reference implementation shows that switching to another blockchain can save cost and enable users to benefit from better performance and a higher level of trust.
Most cryptoassets natively function as bearer instruments. Whoever controls the private key for a given cryptoasset wallet generally controls the assets held by that wallet. In a civil or criminal action or as part of a governmental investigation, parties may be ordered to disclose their private keys or to transfer cryptoassets controlled by those private keys. However, people forget things and lose things, including extremely important things. Parties may lose private keys, and thereby lose control of their assets; parties acting in bad faith, or due to ideological motivation, may claim that “lost” or “forgotten” private keys prevent them from complying with disclosure or turnover orders. Determining whether claims of lost or forgotten private keys are genuine or are bad faith attempts to protect assets will be a challenge for courts, forcing them to confront complex, technology-specific evidence and requiring that they determine whether that loss is bona fide or tactical “self-created impossibility.” Courts may likewise find that traditional contempt sanctions are insufficient to compel a motivated contemnor to comply with disclosure or turnover orders. To avoid expensive, time-consuming evidentiary hearings on contempt, parties and courts should consider ex ante measures, including standing orders and injunctive relief that would require disclosure of and prevent the loss of private keys once financial condition becomes relevant to any claim or defense in litigation. Legislators could create novel contempt sanctions that leverage the unique features of cryptoassets to lien sufficiently identifiable cryptoassets at issue. New laws could create registries listing identifiable cryptoassets subject to turnover orders (similar to state UCC registries), use the infrastructure and legal obligations imposed upon regulated intermediaries by the Bank Secrecy Act and Office of Foreign Asset Controls, or modify existing state law writs to direct stateregulated financial intermediaries to seize those identifiable cryptoassets pending further court order. Although these new sanctions would destroy the fungibility of the cryptoassets at issue and reduce their commercial value, they would also create new, efficient incentives. The lien against identifiable cryptoassets would have no impact on parties who actually lose their private key but would facilitate recovery of cryptoassets taken without authorization in a hack or theft. Finally, the threat of a lien that would adversely impact the value of the specific implicated cryptoassets would reduce the incentive for a bad faith contemnor to defy a turnover order and instead encourage compliance.