Bitcoin draws the highest degree of attention among cryptocurrencies, while coin mining is one of the most important fashion of profiting in the Bitcoin ecosystem. This paper constructs fresh coin circulation networks by tracking the fresh coin transfer routes with transaction referencing in Bitcoin blockchain. This paper proposes a heuristic algorithm to identifying coin miners by comparing coin circulation networks from different mining pools and thereby inferring the common profit distribution schemes of Bitcoin mining pools. Furthermore, this paper characterizes the increasing trend of Bitcoin miner numbers during recent years.
Pingcheng Ruan, Tien Tuan Anh Dinh, Dumitrel Loghin, Meihui Zhang · 7 authors
Blockchain has come a long way: a system that was initially proposed specifically for cryptocurrencies is now being adapted and adopted as a general-purpose transactional system. As blockchain evolves into another data management system, the natural question is how it compares against distributed database systems. Existing works on this comparison focus on high-level properties, such as security and throughput. They stop short of showing how the underlying design choices contribute to the overall differences. Our work fills this important gap and provides a principled framework for analyzing the emerging trend of blockchain-database fusion. We perform a twin study of blockchains and distributed database systems as two types of transactional systems. We propose a taxonomy that illustrates the dichotomy across four dimensions, namely replication, concurrency, storage, and sharding. Within each dimension, we discuss how the design choices are driven by two goals: security for blockchains, and performance for distributed databases. To expose the impact of different design choices on the overall performance, we conduct an in-depth performance analysis of two blockchains, namely Quorum and Hyperledger Fabric, and two distributed databases, namely TiDB, and etcd. Lastly, we propose a framework for back-of-the-envelope performance forecast of blockchain-database hybrids.
Thousands of cryptocurrencies have been issued and publicly exchanged since Bitcoin was invented in 2008. The total cryptocurrency market value exceeds 300 billion US dollars as of 2019. This paper analyzes the prices, volumes, blockchain transactions, coin difficulties and public opinion popularities of 3607 actively exchanged cryptocurrencies. We aim to reveal and explain the homogeneity, i.e., the strong correlation of market performance, and the heterogeneity, i.e., the imbalance of popularities and sophistications, of the cryptocurrencies.
Ramiro Daniel Camino, Christof Ferreira Torres, Mathis Baden, Radu State
Ethereum smart contracts have recently drawn a considerable amount of attention from the media, the financial industry and academia. With the increase in popularity, malicious users found new opportunities to profit by deceiving newcomers. Consequently, attackers started luring other attackers into contracts that seem to have exploitable flaws, but that actually contain a complex hidden trap that in the end benefits the contract creator. In the blockchain community, these contracts are known as honeypots. A recent study presented a tool called HONEYBADGER that uses symbolic execution to detect honeypots by analyzing contract bytecode. In this paper, we present a data science detection approach based foremost on the contract transaction behavior. We create a partition of all the possible cases of fund movements between the contract creator, the contract, the transaction sender and other participants. To this end, we add transaction aggregated features, such as the number of transactions and the corresponding mean value and other contract features, for example compilation information and source code length. We find that all aforementioned categories of features contain useful information for the detection of honeypots. Moreover, our approach allows us to detect new, previously undetected honeypots of already known techniques. We furthermore employ our method to test the detection of unknown honeypot techniques by sequentially removing one technique from the training set. We show that our method is capable of discovering the removed honeypot techniques. Finally, we discovered two new techniques that were previously not known.
Mohammad Javad Amiri, Divyakant Agrawal, Amr El Abbadi
Scalability is one of the main roadblocks to business adoption of blockchain systems. Despite recent intensive research on using sharding techniques to enhance the scalability of blockchain systems, existing solutions do not efficiently address cross-shard transactions. In this paper, we introduce SharPer, a permissioned blockchain system that improves scalability by clustering (partitioning) the nodes and assigning different data shards to different clusters where each data shard is replicated on the nodes of a cluster. SharPer supports both intra-shard and cross-shard transactions and processes intra-shard transactions of different clusters as well as cross-shard transactions with non-overlapping clusters simultaneously. In SharPer, the blockchain ledger is formed as a directed acyclic graph where each cluster maintains only a view of the ledger. SharPer also incorporates a flattened protocol to establish consensus among clusters on the order of cross-shard transactions. The experimental results reveal the efficiency of SharPer in terms of performance and scalability especially in workloads with a low percentage of cross-shard transactions.
Zambia has been using output-based approaches for over two decades to finance whole or part of the public health system. Between 1996 and 2006, performance-based contracting (PBC) was implemented countrywide with the Central Board of Health (CBoH) as the provider of health services. This study reviews the association between PBC and equity of access to maternal health services in Zambia between 1996 and 2006. A comprehensive document review was undertaken to evaluate the implementation process, followed by a trend analysis of health expenditure at district level, and a segmented regression analysis of data on antenatal care (ANC) and deliveries at health facilities that was obtained from five demographic and health survey datasets (1992, 1996, 2002, 2007 and 2014). The results show that PBC was anchored by high-level political support, an overarching policy and legal framework, and collective planning and implementation with all key stakeholders. Decentralization of health service provision was also an enabling factor. ANC coverage increased in both the lower and upper wealth quintiles during the PBC era, followed by a declining trend after the PBC era in both quintiles. Further, the percentage of women delivering at health facilities increased during the PBC era, particularly in rural areas and among the poor. The positive trend continued after the PBC era with similar patterns in both lower and upper wealth quintiles. Despite these gains, per capita health expenditure at district level declined during the PBC era, with the situation worsening after the PBC era. The study concludes that a nationwide PBC approach can contribute to improved equity of access to maternal health services and that PBC is a cost-efficient and sustainable policy reform. The study calls for policymakers to comprehensively evaluate the impact of health system reforms before terminating them.
Tien Tuan Anh Dinh, Anwitaman Datta, Beng Chin Ooi
Research in blockchain systems has mainly focused on improving security and bridging the performance gaps between blockchains and databases. Despite many promising results, we observe a worrying trend that the blockchain landscape is fragmented in which many systems exist in silos. Apart from a handful of general-purpose blockchains, such as Ethereum or Hyperledger Fabric, there are hundreds of others designed for specific applications and typically do not talk to each other. In this paper, we describe our vision of interoperable blockchains. We argue that supporting interaction among different blockchains requires overcoming challenges that go beyond data standardization. The underlying problem is to allow smart contracts running in different blockchains to communicate. We discuss three open problems: access control, general cross-chain transactions, and cross-chain communication. We describe partial solutions to some of these problems in the literature. Finally, we propose a novel design to overcome these challenges.
In this paper, we propose coded Merkle tree (CMT), a novel hash accumulator that offers a constant-cost protection against data availability attacks in blockchains, even if the majority of the network nodes are malicious. A CMT is constructed using a family of sparse erasure codes on each layer, and is recovered by iteratively applying a peeling-decoding technique that enables a compact proof for data availability attack on any layer. Our algorithm enables any node to verify the full availability of any data block generated by the system by just downloading a $Θ(1)$ byte block hash commitment and randomly sampling $Θ(\log b)$ bytes, where $b$ is the size of the data block. With the help of only one connected honest node in the system, our method also allows any node to verify any tampering of the coded Merkle tree by just downloading $Θ(\log b)$ bytes. We provide a modular library for CMT in Rust and Python and demonstrate its efficacy inside the Parity Bitcoin client.
Cryptocurrencies have been around since 2009 when the programmer Satoshi Nakamoto launched the technology behind Bitcoin. There are now several different cryptocurrencies and they are likely to be ...
Online social networks (OSNs) are becoming more and more prevalent in people's life, but they face the problem of privacy leakage due to the centralized data management mechanism. The emergence of distributed OSNs (DOSNs) can solve this privacy issue, yet they bring inefficiencies in providing the main functionalities, such as access control and data availability. In this article, in view of the above-mentioned challenges encountered in OSNs and DOSNs, we exploit the emerging blockchain technique to design a new DOSN framework that integrates the advantages of both traditional centralized OSNs and DOSNs. By combining smart contracts, we use the blockchain as a trusted server to provide central control services. Meanwhile, we separate the storage services so that users have complete control over their data. In the experiment, we use real-world data sets to verify the effectiveness of the proposed framework.
We design and implement Publication Chain (PubChain), a decentralized open-access publication platform built on decentralized and distributed technologies of blockchain and IPFS peer-to-peer file sharing systems. The existing publication platforms have some severe drawbacks. First, instead of promoting widespread knowledge sharing, access to publications on the platforms owned by publishers is often on a fee basis. This drawback of pay wall prevents researchers from "standing on the shoulders of giants". Moreover, the peer review process on most all existing publication platforms (including both open-access and publisher platforms) is prone to be ineffective, since there is no proper incentive to reviewers for performing high-qualified reviews. PubChain is an alternative platform to the existing publication venues aiming to address their drawbacks. No central third-party owns the contents (i.e., papers and reviews) of PubChain. Exploiting blockchain technology, we devise an elaborate incentive scheme on PubChain to incentivize key stakeholders (i.e., authors, readers and reviewers) to participate publication activities on PubChain in a substantive manner by earning credits and rewards through self-motivated interactions. We have performed simulations to investigate the robustness of our proposed incentive scheme against fraudulent publications and reviews. We also have implemented a prototype of PubChain to demonstrate its key concepts.
With the wide-spread use of blockchain technology, Byzantine fault-tolerant (BFT) protocols are explored as a means to achieve consensus on which transactions should be processed next. BFT protocols are not a one-size-fits-all solution: they should be chosen according to the blockchain's use case, which can range from supply chain management to decentralised storage, requiring specialisation e.g. regarding throughput, latency, or level of decentralisation. Previously, consensus protocols were usually hardcoded into the blockchain infrastructure and could not be exchanged, therefore inhibiting flexible use of an otherwise generic blockchain infrastructure. Hyperledger Fabric claims to provide modular consensus and support for crash-fault and Byzantine fault tolerant protocols. However, integrating a BFT protocol has shown that Fabric's architecture is currently not well-suited for this fault model as it requires substantial changes and thereby breaks Fabric's modularity. This also has to be repeated for each integrated BFT protocol. In this paper, we present Bloxy, a blockchain-aware trusted proxy running on the replica that encapsulates all BFT client functionality. Bloxy enables transparent access to generic BFT frameworks and preserves Fabric's modularity even for the Byzantine fault model. It runs inside a trusted execution environment based on Intel's Software Guard Extensions. Bloxy offers blockchain-specific communication mechanisms as well as short-term block storage to handle crashes or disconnects to ensure that all nodes receive block updates. We implemented two Bloxy-based ordering services based on PBFT and the hybrid BFT protocol Hybster. Our evaluation shows that our approach increases throughput by up to 71% compared to directly integrated BFT protocols.
Aiming at the centralization problem of the traditional medical device traceability system. This paper proposes a medical device traceability system based on blockchain technology. By integrating the traditional tracing system with the blockchain technology, based on the decentralization and non-tamperability of the blockchain, the alliance chain and the smart contract construction system are adopted. Manufacturers, distributors, hospitals and consumers in the system can access product information and trace the entire circulation process of the product through RFID. In addition, consumers do not need to register an account number, but directly through the RFID query products related to the main information, such as the shelf life, production enterprises, production time, product price, etc. This system solves the problem that the traditional system is vulnerable to network attack due to centralization, which can improve the robustness of the system, enhance the reliability of data and realizes the traceability of the production, sales and use of medical devices. Therefore, it ensures that the source of medical devices can be traced, the flow can be tracked, the information can be inquired and the responsibility can be investigated to ensure the public consumption safety.
Yao Sun, Lei Zhang, Gang Feng, Bowen Yang · 6 authors
Blockchain has shown a great potential for Internet of Things (IoT) systems to establish trust and consensus mechanisms with no involvement of any third party. It has been not clear how the low complexity devices and the wireless communications among them can pose constraints on the blockchain enabled IoT systems. In this paper, we establish a fundamental analysis model to underpin the blockchain enabled IoT system. By considering spatio-temporal domain Poisson distribution, i.e., node geographical distribution and transaction arrival rate in time domain are both modeled as Poisson point process (PPP), we first derive the distribution of signal-to-interference-plus-noise ratio (SINR), blockchain transaction successful rate as well as overall throughput. Then, based on the analytical model, we design an optimal full function node deployment for blockchain system to achieve the maximum transaction throughput with the minimum full function node density. Numerical results validate the accuracy of our theoretical analysis and evaluate the relationship between blockchain full function node deployment and the density of IoT nodes.
Erasmus Mundus Joint International Doctoral Fellow in Law, Science and Technology, European Union, O.I. Konashevych
The use of blockchain technology, in particular, data insertion (anchoring, hashing) in the blockchain as a way of signing documents or imparting legal properties to facts is researched. A comparative analysis of the known methods of using electronic digital signature with the method of inserting data into the blockchain is carried out. The following issues were addressed. What is the data insertion in the blockchain and what properties do the data acquire? What is the difference between insertion, anchoring, and hashing on the blockchain? What is the difference between blockchain hashing and a digital signature on a document? Will the document be legally binding if it is anchored in the blockchain? What conditions must be met to give legal force for the document? How can anchoring be used to sign contracts, certify evidence that has legal value, denote time stamps, confirm authorship and copyrights, as well as transfer them, issue, and transfer power of attorney and delegate other rights, issue and transfer bearer instruments?
Stefano Loss, Nélio Cacho, João Marcos do Valle, Frederico Lopes
Currently, blockchain has been widely used to store decentralised and secure transactions involving cryptocurrency (for instance, Bitcoin solution). On the other hand, smart city applications are concerned about how data and services can be safely stored and shared. In this regard, this article investigates the use of blockchain and pinpoints a set of essential requirements to meet the needs of blockchain for the context of smart cities. Base on that, we propose a platform, named Orthus, to support the use of blockchain in smart city initiatives. We have demonstrated how to use the proposed platform in the context of the Natal Smart City Initiative, in Brazil, to handle land registration. Finally, we compare this platform with other implementations that use blockchain in different domains.
The need for beef supply chain traceability system is vital due to increase in counterfeiting and use of excessive preservatives and hazardous chemicals. To overcome these problems, it is needed a system which provides the option for the consumer to verify the origin of all input materials for food product based on one step forward and one step backward in supply chain mechanism. Blockchain technology is used as the solution to this problem. This paper aims to identify the requirement and designing the traceability system that could capture all relevant data. The design of beef supply chain traceability system will be described as a business process flow with BPMN (Business Process Model and Notation), in which BPMN will be described the stakeholders involved with the task and needs of the designed system. Based on requirement analysis, this system composed of 4 stakeholders, namely the farmer, feedlot, industry, and retailer. The result showed that the blockchain can create a transparent and efficient supply chain through sharing data between the stakeholders.
Threat intelligence sharing is posited as an important aid to help counter cybersecurity attacks and a number of threat intelligence sharing communities exist. There is a general consensus that many challenges remain to be overcome to achieve fully effective sharing, including concerns about privacy, negative publicity, policy/legal issues and expense of sharing, amongst others. One recent trend undertaken to address this is the use of decentralized blockchain based sharing architectures. However while these platforms can help increase sharing effectiveness they do not fully address all of the above challenges. In particular, issues around trust are not satisfactorily solved by current approaches. In this paper, we describe a novel trust enhancement framework -TITAN- for decentralized sharing based on the use of P2P reputation systems to address open trust issues. Our design uses blockchain and Trusted Execution Environment technologies to ensure security, integrity and privacy in the operation of the threat intelligence sharing reputation system.
Abstract The long cocoa supply chain in Indonesia makes cocoa difficult to trace, data in several countries in Indonesia related to national cocoa data. National cocoa production data is needed in creating policies that are right on target, so these things need to be done. The development of industry 4.0 makes the creation of blockchain technology that can overcome these problems. To create a blockchain system for the cocoa supply chain needs a requirement analysis for the time of making the application. The purpose of this research is to identify the needs and know the interactions that occur in the blockchain chain system in the cocoa supply chain. The method used is requirement analysis, use case diagram, and sequence diagram. The results of this study are two inputs: the structure of the cocoa supply chain and activities that occur in the cocoa supply chain, four stakeholders: farmers, collectors, agroindustry, and exporters, one output: the blockchain system from the cocoa supply chain. Interactions that occur in the system is log in to the system, add the activity, execution phase, ordering phase, and validation phase.
Delivery service via ridesharing is a promising service to share travel costs and improve vehicle occupancy. Existing ridesharing systems require participating vehicles to periodically report individual private information (e.g., identity and location) to a central controller, which is a potential central point of failure, resulting in possible data leakage or tampering in case of controller break down or under attack. In this paper, we propose a Blockchain secured ridesharing delivery system, where the immutability and distributed architecture of the Blockchain can effectively prevent data tampering. However, such tamper-resistance property comes at the cost of a long confirmation delay caused by the consensus process. A Hash-oriented Practical Byzantine Fault Tolerance (PBFT) based consensus algorithm is proposed to improve the Blockchain efficiency and reduce the transaction confirmation delay from 10 minutes to 15 seconds. The Hash-oriented PBFT effectively avoids the double-spending attack and Sybil attack. Security analysis and simulation results demonstrate that the proposed Blockchain secured ridesharing delivery system offers strong security guarantees and satisfies the quality of delivery service in terms of confirmation delay and transaction throughput.
The economic and civic development of local communities is based, first of all, on the local public finance system, which must meet certain conditions so that the management of the territorial administrative units and the functioning of the local authorities meet the standards of a quasi-society. This paper is topical as the issue of local public finances is at the center of the current political debate as all the member states of the Council of Europe are confronted with the issue of harmonizing two diverging trends, namely: controlling and reducing spending and giving as much as possible large autonomies of local communities. The main objective of the paper is to identify solutions to ensure a more balanced allocation of financial resources between different levels of administrative organization, taking into account the budgetary regulation that is imposed at all levels of public administration. The data processing provided by the Ministry of Public Finance and the Court of Accounts highlighted the degree of dependence of local budgets of communes, cities, municipalities and counties on the consolidated general budget in the context of a decentralized process that is desirable to be as efficient as possible.
The goal is to study the assessment of the doctors working in the PAS regarding the readiness of the PAS institutions ofUkraineto implement the project mechanism: "The transition to paying for contracts with the National Health Service of Ukraine" within the further development of decentralized organizational transformations of the administrative system of the PAS ofUkraine. Materials and methods. 53 doctors (PAS staff ofUkraine) were interviewed by a specially designed questionnaire. Statistical processing of the obtained results is carried out using generally accepted statistical methods. Results. The comprehensive assessments of the readiness of PAS institutions inUkraine to implement the project mechanism: "Going to pay for contracts with the National Health Service of Ukraine", taking into account the basic principles of further reorganization transformations of structural management, based on the implementation of the model of the project of the regional pathoanatomical center (SRC). Conclusions. The results of the study showed that, according to surveyed doctors, the current system of PAS of Ukraine within the framework of the implementation of the mechanism of decentralized organizational reform by 2020 will be ready only by 67.5% for the implementation of the project mechanism, similar results are associated with existing problems in the field of financing of PAS establishments in Ukraine and the urgent need to develop new investment mechanisms aimed at realizing the search for the necessary financing of the project's economic and resource support.
Abstract Although the logistics management has been improving, the information management is still stagnant. The renewal mechanism of logistics information is the basic requirement of logistics system, but it is more important to solve the trust problem of logistics information. It is good for improving the logistics management to design a verifiable information management mechanism which can help relevant participants establish trust relationships. This paper analyzes the development status of block chain technology, then a decentralized and self-verifiable system management program model is designed. Finally, the application is implemented based on the intelligent contract design of Ethereum block chain.