The rise of popular cryptocurrencies like Bitcoin and Ethereum has increased the popularity of blockchain technology, the framework these cryptocurrencies are built upon. The security and access control that blockchain technology has provided for cryptocurrencies has peaked the curiosity of other industries, realizing its potential value and future outlook. In this paper, we analyze two types of blockchains, permission-ed and permission-less, and introduce a two-tier blockchain concept utilizing both types for secure data sharing. We provide background on the consensus algorithms used for each blockchain type, Proof-of-Work and Proof-of-Authority. Testing on both Mac OS and Ubuntu Linux-based system environments, preliminary results show that by increasing the number of miners in a Proof-of-Work consensus, there is a correlating increase in the total block count in a permission-less blockchain, where the rate of increase is dependent on the system environment. In the Proof-of-Authority permission-ed blockchain, the block count observed little to no change across both environments.
Local energy markets could play a very important role in future electric power systems, allowing small electricity producers/consumers to trade within a small geographical area. In this context, an important challenge to allow the proper operation of a local energy market is to devise efficient and economic computational platforms in charge of data storage, data communication, and any other relevant computational requirements. Fortunately, the recent developments in blockchain-based mechanisms open up promising approaches that can support the effective management of local energy markets. In fact, blockchain technology allows, in particular, to carry out decentralised payments without involving a third party in charge of keeping track of the trades performed, which can potentially simplify and enhance the management of a local energy market significantly. Motivated by this, this paper will study the use of the blockchainbased Ethereum platform as the computational support for a local energy market. Specifically, this paper addresses the scalability of this platform in terms of number of participants in the local energy market, and in terms of trading frequency. With this purpose, computer simulations are carried out for a market that consists of day-ahead trading and real-time trading. The day-ahead mechanism trades energy quantities in such a way that flexible demand can be shifted to balance inflexible supply, and the real-time mechanism trades energy in such a way that flexible loads cover deviations from the day-ahead settlement. The results illustrate that the Ethereum platform is sufficiently scalable, allowing to manage a local energy market with a large number of participants and a high trading frequency.
Marko Hölbl, Aida Kamišalić, Muhamed Turkanović, Marko Kompara · 6 authors
Blockchain technology enables the creation of a decentralized and distributed environment in which transactions and data are not controlled by a central authority. Simultaneously transactions are secure, ubiquitous and trustworthy due to the used cryptographic principles. In this paper, we present a global decentralized blockchain-based platform and ecosystem called EduCTX. The platform enables managing, assigning and presenting credentials for individuals and educational institutions as well as other potential stakeholders such as companies, institutions and organizations. Further it enables the development of own digital services, which offers organizations the opportunity to automate the evaluation of individuals' skills and knowledge. The EduCTX platform is implemented on the blockchain platform Ethereum on a consortium-based network of Ethereum run nodes. The platform enables a globally efficient, simplified and ubiquitous environment to avoid language and administrative barriers.
Pilar Grau Carles, Diego Jaureguizar Arellano, Carlos Jaureguizar Francés
In this paper we examine the characteristics of the daily price series of 16 different cryptocurrencies between July 2017 and February 2018. The methodologies used for the analysis are the so-called Minimum Spanning Tree (MST) and hierarchical analysis by dendrogram, both obtained Pearson correlations between daily returns. This methodology visualizes the market relationships between the assets analyzed, identifying a high correlation between price movements for all the currencies. In addition, it has been possible to identify Ethereum’s position as a benchmark currency in the cryptocurrency market, rather than Bitcoin, as one might expect, due to its popularity and trading volume.
Alin Bogdan Popa, Ioan Mihail Stan, Răzvan Rughiniş
Blockchain is one of the most important technological trends today since it has a wide spectrum of use cases (financial industry applications, supply-chain tracking, MedTech EHR management, energy grid etc.) and it offers a wide range of implementations. However, the main goal of the Blockchain remains the transfer of value-bearing assets between an owner of a resource and a client. Due to CPU intensive consensus algorithms, transaction prioritization based on potential earnings, the validation process and so on, Blockchain implementations are not able to support real-time services and, also, to enable a varied cloud computing service catalog on top of the existing infrastructure. Our solution is addressing this drawback by developing a system supporting late payments through our innovative concept called latent-transactions. We also provide the instruments through which we make viable off-chain agreements, between the parties involved in a transaction. Therefore, one can benefit from a service, prior to actual payment. In addition, we offer a service enlargement mechanism by providing a catalog where any member of Blockchain can subscribe and from where one can sell services in a real-time manner with adaptive pricing, based on the context (demand, activity at runtime etc.).
Miguel Tavares, André Guerreiro, Carlos Coutinho, Filipe Veiga · 5 authors
Businesses and organizations have for long been trying to tackle the most prominent issues regarding identity management and systems. Traditionally, the proof of trust concerning the identification of a citizen, a customer or a participant in any business or transaction consisted always in a physical evidence (e.g., a signature, fingerprint, photo or other) whose value would rely on a trusted third-party such as a notary or attorney that confirmed the veracity of that physical evidence. More recent approaches include novel types of evidence such as digital certificates, but still these have no value unless they are issued and signed by a trusted centralized third-party that confirms the authenticity of the certificate. These are then often used by businesses to identify and trace their parties and stakeholders, in a process known as "Know Your Customer" (KYC). This process is often slow and requires costly human intervention. This paper presents WalliD, a decentralized approach of a secure protocol to handle customer identification using Blockchain. The paper then shows a proof of concept workflow implementation of this protocol developed using an Ethereum Wallet.
Cryptocurrency mining is an important process that ensures the reliability of cryptocurrency system. A significant computing power is used in cryptocurrency mining. One of the most important tasks in cryptocurrency mining is to ensure the maximum performance of used computing capacities. In this paper we review the existing Ethereum mining algorithm and search for possibilities for speeding up the mining by applying a new asynchronous mining algorithm.
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
This paper tackles the shortcomings of the traditional centralized stock exchange systems, such as high transaction fees, centralized governance susceptible to attacks and lack of openness regarding the market actions and algorithms, by proposing an innovative architecture using blockchain to develop a decentralized stock exchange and an open continuous market. The proposed blockchain based solution solves the drawbacks of the centralized stock exchange architecture by ensuring the integrity and security of the owner's assets and orders, self-enforcing smart agreements between parties as well as achieving democratic and reliable decisions regarding the execution and settlement of the orders through consensus algorithms. The proposed architecture uses smart contracts to enforce the validation of the owner's rights and the correct execution and settlement of the orders, thus eliminating the need of a central authority that ensures the correctness of the stock exchange process. The solution was validated by implementing a prototype in Ethereum for a subset of rules for the Bucharest Stock Exchange. The experimental results show that the decentralized solution can offer lower transaction fees by replacing the commissions owed to brokers and central authorities with mining fees that are used to compensate the miners for their honest work in keeping the integrity of the system.
Amjad Aldweesh, Maher Alharby, Ellis Solaiman, Aad van Moorsel
A defining feature of the Ethereum blockchain is its ability to execute smart contracts, providing a Turing complete programming model for distributed applications in non-trusted environments. The successful operation of the Ethereum blockchain depends on whether the miners' incentives (in the form of fees) to execute contracts is proportional to the miners' cost (in terms of energy usage, and thus CPU usage). In general, if the received fee is not proportional to the computational cost, miners would prefer some tasks over others, thus potentially adversely affecting the continuing dependable operation of the blockchain. In this paper we design a benchmark to compare smart contract execution time with the award a miner would receive, to determine if incentives align. We present the design of the benchmarking approach and provide initial results for the Python Ethereum client running on a Mac. The results indicate that for functions in Ethereum's most popular contracts the difference of reward per CPU second can be up to a factor of almost 50. In addition, contract creation, which is done once for each new contract, can be up to 6 times more lucrative than the regular execution of contract functions. Potentially, these discrepancies result in misaligned incentives that impact the dependable operation of the blockchain.
Shalini Shukla, A.N. Thasmiya, Donthi Shashank, H. R. Mamatha
Voting is an important part of the administration of a country. Votes are still being carried out by physically going to voting booths. This process doesn't guarantee security and cases of tampering has been observed. This paper aims at removing these issues in the voting process by making it online and using the technology, Blockchain. Blockchain uses encryption and hashing to make every vote secure. In this case, one vote is considered as a transaction. A peer to peer network is created to create a private blockchain that share this distributed ledger having voting transaction. The application is designed in such a way so that the intricacies of the underlying architecture is hidden from the user. Each voter is uniquely identified by Government approved Aadhar number. The application makes use of this number to make sure that each voter gets only one chance to vote. When the vote gets submitted as a transaction then all the peers get synch up. Since each peer is associated with a public and private key the votes are encrypted and hashed and added to the blockchain to increase security and form a chain of blocks. Votes cannot be tracked back to the voter. In this paper, a peer to peer network is created having minimum three peers. Since voting is made online, it is expected that this paper will increase the voter turnouts. The scalability of the blockchain application depends on the secondary memory limit of the peer.
The notion of smart contracts in distributed ledger systems have been hailed as a safe way of enforcing contracts between participating parties. However, unlike legal contracts, which talk about ideal behaviour and consequences of not adhering to such behaviour, smart contracts are by their very nature executable code, giving explicit instructions on how to achieve compliance. Executable specification languages, particularly Turing complete ones, are notoriously known for the difficulty of ensuring correctness, and recent incidents which led to huge financial losses due to bugs in smart contracts, have highlighted this issue. In this paper we show how standard techniques from runtime verification can be used in the domain of smart contracts, including a novel stake-based instrumentation technique which ensures that the violating party provides insurance for correct behaviour. The techniques we describe have been partially implemented in a proof-of-concept tool ContractLarva, which we discuss in this paper.
Block Chain (BC), the technology behind the Bitcoin crypto-currency system. Blockchain helps Build Trusted, Powerful and Transparent Process with the potential to disrupt Intermediaries, Third parties & Expensive processes. Proof-of-Work (PoW), Proof of Stake (PoS), Proof of Authority (PoA), consensus algorithm plays a vital role in ensuring BC security by maintaining a digital ledger of transactions, which is considered to be incorruptible. Firstly, we explore top crypto currencies after that we will explore blockchain and mining concept. In further we will be exploring Ethereum blockchain solidity programming more and make DAPPs on Ethereum blockchain network.
Blockchain is a decentralized technology. It has extensive power to solve business problems. Cryptography secures the records in a blockchain transaction and each transaction is tied to previous transactions or records. Blockchain transactions are validated by algorithms on the nodes. A single entity cannot create a transaction. Finally, blockchains provide transparency, giving each participant the ability to monitor the transactions at any time. Smart contract make secure transaction which helps to avoid third party disruption. Ethereum is a decentralized platform that runs smart contracts. This enables developers to create markets move funds in accordance with instructions given long in the past. The main features of blockchain are Decentralization, Immutability Faster dealings, Transaction and validation happens in seconds etc..
John Collomosse, Tu Bui, Alan Brown, John Sheridan · 9 authors
We present ARCHANGEL; a decentralised platform for ensuring the long-term integrity of digital documents stored within public archives. Document integrity is fundamental to public trust in archives. Yet currently that trust is built upon institutional reputation --- trust at face value in a centralised authority, like a national government archive or University. ARCHANGEL proposes a shift to a technological underscoring of that trust, using distributed ledger technology (DLT) to cryptographically guarantee the provenance, immutability and so the integrity of archived documents. We describe the ARCHANGEL architecture, and report on a prototype of that architecture build over the Ethereum infrastructure. We report early evaluation and feedback of ARCHANGEL from stakeholders in the research data archives space.
Smart contracts are a new paradigm that emerged with the rise of the blockchain technology. They allow untrusting parties to arrange agreements. These agreements are encoded as a programming language code and deployed on a blockchain platform, where all participants execute them and maintain their state. Smart contracts are promising since they are automated and decentralized, thus limiting the involvement of third trusted parties, and can contain monetary transfers. Due to these features, many people believe that smart contracts will revolutionize the way we think of distributed applications, information sharing, financial services, and infrastructures. To release the potential of smart contracts, it is necessary to connect the contracts with the outside world, such that they can understand and use information from other infrastructures. For instance, smart contracts would greatly benefit when they have access to web content. However, there are many challenges associated with realizing such a system, and despite the existence of many proposals, no solution is secure, provides easily-parsable data, introduces small overheads, and is easy to deploy. In this paper we propose PDFS, a practical system for data feeds that combines the advantages of the previous schemes and introduces new functionalities. PDFS extends content providers by including new features for data transparency and consistency validations. This combination provides multiple benefits like content which is easy to parse and efficient authenticity verification without breaking natural trust chains. PDFS keeps content providers auditable, mitigates their malicious activities (like data modification or censorship), and allows them to create a new business model. We show how PDFS is integrated with existing web services, report on a PDFS implementation and present results from conducted case studies and experiments.
Smart contracts, as a promising and powerful application on the Ethereum blockchain, have been growing rapidly in the past few years. Since they are highly vulnerable to different forms of attacks, their security becomes a top priority. However, existing security auditing techniques are either limited in fnding vulnerabilities (rely on pre-defned bug paterns) or very expensive (rely on program analysis), thus are insufcient for Ethereum.
Purpose The purpose of this paper is to employ the case of Organization for Economic Cooperation and Development (OECD) data repositories to examine the potential of blockchain technology in the context of addressing basic contemporary societal concerns, such as transparency, accountability and trust in the policymaking process. Current approaches to sharing data employ standardized metadata, in which the provider of the service is assumed to be a trusted party. However, derived data, analytic processes or links from policies, are in many cases not shared in the same form, thus breaking the provenance trace and making the repetition of analysis conducted in the past difficult. Similarly, it becomes tricky to test whether certain conditions justifying policies implemented still apply. A higher level of reuse would require a decentralized approach to sharing both data and analytic scripts and software. This could be supported by a combination of blockchain and decentralized file system technology. Design/methodology/approach The findings presented in this paper have been derived from an analysis of a case study, i.e., analytics using data made available by the OECD. The set of data the OECD provides is vast and is used broadly. The argument is structured as follows. First, current issues and topics shaping the debate on blockchain are outlined. Then, a redefinition of the main artifacts on which some simple or convoluted analytic results are based is revised for some concrete purposes. The requirements on provenance, trust and repeatability are discussed with regards to the architecture proposed, and a proof of concept using smart contracts is used for reasoning on relevant scenarios. Findings A combination of decentralized file systems and an open blockchain such as Ethereum supporting smart contracts can ascertain that the set of artifacts used for the analytics is shared. This enables the sequence underlying the successive stages of research and/or policymaking to be preserved. This suggests that, in turn, and ex post , it becomes possible to test whether evidence supporting certain findings and/or policy decisions still hold. Moreover, unlike traditional databases, blockchain technology makes it possible that immutable records can be stored. This means that the artifacts can be used for further exploitation or repetition of results. In practical terms, the use of blockchain technology creates the opportunity to enhance the evidence-based approach to policy design and policy recommendations that the OECD fosters. That is, it might enable the stakeholders not only to use the data available in the OECD repositories but also to assess corrections to a given policy strategy or modify its scope. Research limitations/implications Blockchains and related technologies are still maturing, and several questions related to their use and potential remain underexplored. Several issues require particular consideration in future research, including anonymity, scalability and stability of the data repository. This research took as example OECD data repositories, precisely to make the point that more research and more dialogue between the research and policymaking community is needed to embrace the challenges and opportunities blockchain technology generates. Several questions that this research prompts have not been addressed. For instance, the question of how the sharing economy concept for the specifics of the case could be employed in the context of blockchain has not been dealt with. Practical implications The practical implications of the research presented here can be summarized in two ways. On the one hand, by suggesting how a combination of decentralized file systems and an open blockchain, such as Ethereum supporting smart contracts, can ascertain that artifacts are shared, this paper paves the way toward a discussion on how to make this approach and solution reality. The approach and architecture proposed in this paper would provide a way to increase the scope of the reuse of statistical data and results and thus would improve the effectiveness of decision making as well as the transparency of the evidence supporting policy. Social implications Decentralizing analytic artifacts will add to existing open data practices an additional layer of benefits for different actors, including but not limited to policymakers, journalists, analysts and/or researchers without the need to establish centrally managed institutions. Moreover, due to the degree of decentralization and absence of a single-entry point, the vulnerability of data repositories to cyberthreats might be reduced. Simultaneously, by ensuring that artifacts derived from data based in those distributed depositories are made immutable therein, full reproducibility of conclusions concerning the data is possible. In the field of data-driven policymaking processes, it might allow policymakers to devise more accurate ways of addressing pressing issues and challenges. Originality/value This paper offers the first blueprint of a form of sharing that complements open data practices with the decentralized approach of blockchain and decentralized file systems. The case of OECD data repositories is used to highlight that while data storing is important, the real added value of blockchain technology rests in the possible change on how we use the data and data sets in the repositories. It would eventually enable a more transparent and actionable approach to linking policy up with the supporting evidence. From a different angle, throughout the paper the case is made that rather than simply data, artifacts from conducted analyses should be made persistent in a blockchain. What is at stake is the full reproducibility of conclusions based on a given set of data, coupled with the possibility of ex post testing the validity of the assumptions and evidence underlying those conclusions.
Cryptocurrency is a well-developed blockchain technology application that is currently a heated topic throughout the world. The public availability of transaction histories offers an opportunity to analyze and compare different cryptocurrencies. In this paper, we present a dynamic network analysis of three representative blockchain-based cryptocurrencies: Bitcoin, Ethereum, and Namecoin. By analyzing the accumulated network growth, we find that, unlike most other networks, these cryptocurrency networks do not always densify over time, and they are changing all the time with relatively low node and edge repetition ratios. Therefore, we then construct separate networks on a monthly basis, trace the changes of typical network characteristics (including degree distribution, degree assortativity, clustering coefficient, and the largest connected component) over time, and compare the three. We find that the degree distribution of these monthly transaction networks cannot be well fitted by the famous power-law distribution, at the same time, different currency still has different network properties, e.g., both Bitcoin and Ethereum networks are heavy-tailed with disassortative mixing, however, only the former can be treated as a small world. These network properties reflect the evolutionary characteristics and competitive power of these three cryptocurrencies and provide a foundation for future research.
David M. Maslove, Jacob Klein, M. Kathryn Brohman, Patrick Martin
<sec> <title>BACKGROUND</title> Blockchain technology is emerging as an innovative tool in data and software security. </sec> <sec> <title>OBJECTIVE</title> This study aims to explore the role of blockchain in supporting clinical trials data management and develop a proof-of-concept implementation of a patient-facing and researcher-facing system. </sec> <sec> <title>METHODS</title> Blockchain-based Smart Contracts were built using the Ethereum platform. </sec> <sec> <title>RESULTS</title> We described BlockTrial, a system that uses a Web-based interface to allow users to run trials-related Smart Contracts on an Ethereum network. Functions allow patients to grant researchers access to their data and allow researchers to submit queries for data that are stored off chain. As a type of distributed ledger, the system generates a durable and transparent log of these and other transactions. BlockTrial could be used to increase the trustworthiness of data collected during clinical research with benefits to researchers, regulators, and drug companies alike. In addition, the system could empower patients to become more active and fully informed partners in research. </sec> <sec> <title>CONCLUSIONS</title> Blockchain technology presents an opportunity to address some of the common threats to the integrity of data collected in clinical trials and ensure that the analysis of these data comply with prespecified plans. Further technical work is needed to add additional functions. Policies must be developed to determine the optimal models for participation in the system by its various stakeholders. </sec>
Open access
Blockchain Technology Applications and Security
Ethics in Clinical Research
Artificial Intelligence in Healthcare and Education
This thesis focuses on aspects related to the functioning of the gossip\nnetworks underlying three relatively popular cryptocurrencies: Ethereum, Nano\nand IOTA.\n We look at topics such as automatic discovery of peers when a new node joins\nthe network, bandwidth usage of a node, message passing protocols and storage\nschemas and optimizations for the shared ledger. We believe this is a topic\nthat is often overlooked in works about blockchains and cryptocurrencies.\nVulnerabilities and inefficiencies attain a higher significance than ones in a\nregular open source project because of the rather direct financial implications\nof these projects. Barring Bitcoin, a network that has been around for nearly\n10 years, no other project has substantial documentation for its operational\ndetails other than scattered and sparse pages in the source code repositories.\nAlmost all of the content described here has been extracted by studying the\nsource code of the reference implementations of these projects.\n We evaluate the use of Invertible Bloom Lookup Tables and the Graphene\nprotocol to decrease block propagation times and bandwidth usage of certain\nmessages. We perform realistic simulations that show significant improvements.\nWe provide a complete implementation of Graphene in Geth, Ethereum's main node\nsoftware and test this implementation against the main Ethereum blockchain.\n We also crawled the chosen cryptocurrency networks for publicly visible nodes\nand provide an Autonomous System-level breakdown of these nodes with the end\ngoal of estimating the ease of performing attacks such as BGP hijacks and their\nimpact.\n Code written for implementing Graphene in Geth, performing various\nsimulations and for other miscellaneous tasks has been uploaded to Github at\nhttps://github.com/sunfinite/masters-thesis.\n