C. Kouzinopoulos, Konstantinos M. Giannoutakis, Konstantinos Votis, Dimitrios Tzovaras · 10 authors
The H2020 European research project Safe-Guarding Home IoT Environments with Personalised Real-time Risk Control (GHOST) aims to develop a cyber-security layer on IoT smart home installations. The proposed system analyses packet-level data flows for building patterns of communications between IoT devices and external entities. To ensure non-repudiation, integrity and authentication of the data captured, they are stored in a Blockchain, a distributed ledger network, as digitally-signed transactions. Since the data can potentially include sensitive user information, it is imperative to promote trust by informing users about the operating principles of the network as well as to request the acceptance of a consent form by them. This paper presents the design and implementation of a Forms of Consent application, a Distributed Application that interacts with a set of Smart Contracts deployed on a private Ethereum network. The application is being developed as part of the GHOST project.
Sara Rouhani, Luke Butterworth, Adam D. Simmons, Darryl G. Humphery · 5 authors
The set of distributed ledger architectures known as blockchain is best known for cryptocurrency applications such as Bitcoin and Ethereum. These permissionless block chains are showing the potential to be disruptive to the financial services industry. Their broader adoption is likely to be limited by the maximum block size, the cost of the Proof of Work consensus mechanism, and the increasing size of any given chain overwhelming most of the participating nodes. These factors have led to many cryptocurrency blockchains to become centralized in the nodes with enough computing power and storage to be a dominant miner and validator. Permissioned chains operate in trusted environments and can, therefore, avoid the computationally expensive consensus mechanisms. Permissioned chains are still susceptible to asset storage demands and non-standard user interfaces that will impede their adoption. This paper describes an approach to addressing these limitations: permissioned blockchain that uses off-chain storage of the data assets and this is accessed through a standard browser and mobile app. The implementation in the Hyperledger framework is described as is an example use of patient-centered health data management.
DAO attack showed that formal verification of smart contracts is an important issue that should be addressed to prevent irreversible consequences due to design faults activation in Blockchain applications. This paper proposes a modeling method of an Ethereum application based on smart contracts, with the aim of applying a formal method, namely Model-Checking, to verify that the application implementation complies with its specification, formalized by a set of temporal logic propositions. NuSMV tool has been chosen to support this first approach. The proposed model template is shaped by three layers capturing respectively the behavior of Ethereum blockchain, the smart contracts themselves and the execution framework. The approach is illustrated by a case study coming from energy market field.
Mathis Steichen, Beltran Fiz, Robert Norvill, Wazen M. Shbair · 5 authors
Large files cannot be efficiently stored on blockchains. On one hand side, the blockchain becomes bloated with data that has to be propagated within the blockchain network. On the other hand, since the blockchain is replicated on many nodes, a lot of storage space is required without serving an immediate purpose, especially if the node operator does not need to view every file that is stored on the blockchain. It furthermore leads to an increase in the price of operating blockchain nodes because more data needs to be processed, transferred and stored. IPFS is a file sharing system that can be leveraged to more efficiently store and share large files. It relies on cryptographic hashes that can easily be stored on a blockchain. Nonetheless, IPFS does not permit users to share files with selected parties. This is necessary, if sensitive or personal data needs to be shared. Therefore, this paper presents a modified version of the InterPlanetary Filesystem (IPFS) that leverages Ethereum smart contracts to provide access controlled file sharing. The smart contract is used to maintain the access control list, while the modified IPFS software enforces it. For this, it interacts with the smart contract whenever a file is uploaded, downloaded or transferred. Using an experimental setup, the impact of the access controlled IPFS is analyzed and discussed.
The rise of fraudulent cases seems to be a nuisance to an organization as they're an investment of money. Various resources also gives the impression to be on someone else, who has false claims. The verification process of these organizations are long and tedious process where the organization would have lost its time and resource on. Blockchain technology was introduced fairly recently in literature, which is the underlying technology behind the very popular cryptocurrency Bitcoin. The blockchain is a decentralized approach, it is secured by design network which was to overcome double spending problem by a central server. The concept of servers is eradicated in this architecture, where the data is distributed across geographically on separate ledgers. Blockchain applications have diversified as MIT Media Labs introduced Blockcerts for certification of academic records. Ethereum is platform for developing these decentralized applications using Blockchain ledgers. Ethereum uses a concept called Merkle trees which is the concept used for verification through hashing. As per the working in the literature; this application would make verification of academic documents simple and quick with the usage of Blockchain clients such as Ethereum and an IPFS hash. In this paper we propose a system that provides a solution that addresses the above mentioned issues.
Çalışmada gün geçtikçe popülerliği ve buna bağlı olarak toplam piyasa değerleri ve işlem hacimleri artan, çok sayıda ve çok çeşitli piyasalarda işlem gören kripto paraların fiyatlarının birbiri üzerindeki etkisi araştırılmıştır. Çalışmada, Bitcoin, Ethereum, Ripple, Bitcoin Cash, Cardano, Litecoin, NEM, NEO, Stellar ve IOTA kripto paralarının seçiminde toplam piyasa değerleri dikkate alınmıştır ve en yüksek toplam piyasa değerine sahip 10 kripto para analize dahil edilmiştir. 15 Aralık 2017 ve 17 Ocak 2018 tarihleri arasında çalışmaya konu olan kripto paraların günlük fiyat hareketleri arasındaki ilişkiyi incelemek için serilere Johansen Eşbütünleşme Testi ve Granger Nedensellik Testi uygulanmıştır. Çalışmanın sonucunda, Cardano’nun NEO’nun Granger nedeni olduğu, Bitcoin’in Bitcoin Cash’in Granger nedeni olduğu, Litecoin’in Bitcoin Cash’in Granger nedeni olduğu, NEM’in Bitcoin Cash’in Granger nedeni olduğu, Ripple’ın Bitcoin’in Granger nedeni olduğu, NEO ve Ethereum’un birbirinin Granger nedeni olduğu, NEO ve Litecoin’in birbirinin Granger nedeni olduğu ve NEM’in Stellar’ın Granger nedeni olduğu tespit edilerek, bu değişkenlerin fiyat hareketlerinin kısa dönemde birbirini etkilediği ortaya konmuştur.
The Enterprise Ethereum Client Specification by the Enterprise Ethereum Alliance defines the requirements which Ethereum Clients offering private smart contract capabilities should comply with. This specification though ground breaking, misses some important blockchain requirements and does not fully consider the requirements of Ethereum Clients offering Private Sidechain capabilities. This paper presents the case for Private Sidechains and defines requirements to be complied with to deliver this technology. The capabilities of three blockchain clients have been analysed based on the requirements: Quorum, Parity, and Hyperledger Fabric. Quorum and Hyperledger Fabric operate as private consortium blockchains where as Parity delivers private transaction capabilities on top of Ethereum MainNet. These differing approaches has led to different strengths and weaknesses which has resulted in each client not complying with one or more key requirement. In particular, none of the reviewed blockchain clients support the ability to determine bootstrap information to establish on-demand blockchains and none of the clients support secure management and pinning from Ethereum MainNet. This paper presents Ethereum Private Sidechains and a range of technologies which allow it to deliver on complex sidechain requirements. Ethereum Registration Authorities are presented, which allow entities which have not previously interacted to securely obtain information to bootstrap a sidechain, and a Management and Pinning strategy is described which allows the state of a sidechain to be securely pinned to Ethereum MainNet without compromising privacy.
Bitcoin and Ethereum are novel mechanisms for decentralizing the concept of money and computation. Extending decentralization to the human identity concept, we can think of using blockchain for creating a list of verified human identities with a one-person-one-ID property. UniqueID is a Decentralized Autonomous Organization(DAO) for maintaining human identities such that every physical human entity can have no more that one account. One part of this identity is simply the user's claim on one of his unique, permanent, and measurable characteristics -biometrics. Blockchain has proved its integrity as a platform for storing and performing computations on such claims. The biggest challenge here is to ensure that the user has submitted his own valid biometric data. Human verifiers can check if there is any inconsistency in other users' data, by peer-to-peer checks. For preventing bad behavior and centralization in the verification process, UniqueID benefits from novel governance mechanisms to choose verifiers and punish unjust ones. Also, there are incentives for honest verifiers and users by newly generated tokens. We show how the users' privacy can be preserved by using state-of-the-art cryptographic techniques, and so they can use their identity without any concerns for votings, financial and banking purposes, social media accounts, reputation systems etc.
Jun 18, 2018·Andrew Burnie, 2018. Exploring the Interconnectedness of Cryptocurrencies using Correlation Networks. In Cryptocurrency Research Conference 2018 (Anglia Ruskin University, 2018). Anglia Ruskin University, Cambridge, UK
Correlation networks were used to detect characteristics which, although fixed over time, have an important influence on the evolution of prices over time. Potentially important features were identified using the websites and whitepapers of cryptocurrencies with the largest userbases. These were assessed using two datasets to enhance robustness: one with fourteen cryptocurrencies beginning from 9 November 2017, and a subset with nine cryptocurrencies starting 9 September 2016, both ending 6 March 2018. Separately analysing the subset of cryptocurrencies raised the number of data points from 115 to 537, and improved robustness to changes in relationships over time. Excluding USD Tether, the results showed a positive association between different cryptocurrencies that was statistically significant. Robust, strong positive associations were observed for six cryptocurrencies where one was a fork of the other; Bitcoin / Bitcoin Cash was an exception. There was evidence for the existence of a group of cryptocurrencies particularly associated with Cardano, and a separate group correlated with Ethereum. The data was not consistent with a token's functionality or creation mechanism being the dominant determinants of the evolution of prices over time but did suggest that factors other than speculation contributed to the price.
Correlation networks were used to detect characteristics which, although\nfixed over time, have an important influence on the evolution of prices over\ntime. Potentially important features were identified using the websites and\nwhitepapers of cryptocurrencies with the largest userbases. These were assessed\nusing two datasets to enhance robustness: one with fourteen cryptocurrencies\nbeginning from 9 November 2017, and a subset with nine cryptocurrencies\nstarting 9 September 2016, both ending 6 March 2018. Separately analysing the\nsubset of cryptocurrencies raised the number of data points from 115 to 537,\nand improved robustness to changes in relationships over time. Excluding USD\nTether, the results showed a positive association between different\ncryptocurrencies that was statistically significant. Robust, strong positive\nassociations were observed for six cryptocurrencies where one was a fork of the\nother; Bitcoin / Bitcoin Cash was an exception. There was evidence for the\nexistence of a group of cryptocurrencies particularly associated with Cardano,\nand a separate group correlated with Ethereum. The data was not consistent with\na token's functionality or creation mechanism being the dominant determinants\nof the evolution of prices over time but did suggest that factors other than\nspeculation contributed to the price.\n
Message digest algorithms are one of the underlying building blocks of\nblockchain platforms such as Ethereum. This paper analyses situations in which\nthe message digest collision resistance property can be exploited by attackers.\nTwo mitigations for possible attacks are described: longer message digest sizes\nmake attacks more difficult; and, including timeliness properties limits the\namount of time an attacker has to determine a hash collision.\n
By comparing cryptocurrencies with other existing payment methods, including banknotes and bank cards, it is clear that the use of Bitcoin and its competitors (Ethereum, \dots) is almost insignificant in world trade. We may also note that these cryptocurrencies have become tools of speculation, which is the antithesis of their primary purpose. Based essentially on the security of electronic signatures, the Ecash introduced here will put the users back to the center of the game and exclude miners and their enormous waste of power energy. Thus, the purpose of this paper is to show that even a piece of paper can be recycled into a secure Ecash, while remaining environmentally friendly. Hence, we create here a cryptocurrency that would use a slight modification of the current banknotes to set up anonymous electronic transactions. By trading with banknotes, we mechanically transfer ownership of the paper money from one owner to another, hence, in this scheme, we introduce the notion of ownership transfer. It implies that at each transaction the elements allowing to authenticate the Ecash does not change, while the ownership certificate will change since the Ecash is transfer towards someone else.
We analyze the economic incentives generated by the proof-of-stake mechanism discussed in the Ethereum Casper upgrade proposal. Compared with proof-of-work, proof-of-stake has a different cost structure for attackers. In Budish (2018), three equations characterize the limits of Bitcoin, which has a proof-of-work mechanism. We investigate their counterparts and evaluate the risk of double-spending attack and sabotage attack. We argue that PoS is safer than PoW agaisnt double-spending attack because of the tractability of attackers, which implies a large "stock" cost for the attacker. Compared to a PoW system whose mining equipments are repurposable, PoS is also safer against a sabotage attack.
Petar Tsankov, Andrei Dan, Dana Drachsler Cohen, Arthur Gervais · 6 authors
Permissionless blockchains allow the execution of arbitrary programs (called smart contracts), enabling mutually untrusted entities to interact without relying on trusted third parties. Despite their potential, repeated security concerns have shaken the trust in handling billions of USD by smart contracts. To address this problem, we present Securify, a security analyzer for Ethereum smart contracts that is scalable, fully automated, and able to prove contract behaviors as safe/unsafe with respect to a given property. Securify's analysis consists of two steps. First, it symbolically analyzes the contract's dependency graph to extract precise semantic information from the code. Then, it checks compliance and violation patterns that capture sufficient conditions for proving if a property holds or not. To enable extensibility, all patterns are specified in a designated domain-specific language. Securify is publicly released, it has analyzed >18K contracts submitted by its users, and is regularly used to conduct security audits by experts. We present an extensive evaluation of Securify over real-world Ethereum smart contracts and demonstrate that it can effectively prove the correctness of smart contracts and discover critical violations.
Son dönemlerde dünyada olduğu gibi ülkemizde de popülaritesi giderek artan ve başta Bitcoin, Ethereum gibi kripto paraları içinde barındıran kripto para piyasası gerek uluslararası gerekse ulusal yazının ilgisini çekmektedir. Küresel değişimin ağırlıklı olarak finansal bağlamının son halkalarından biri olan bu piyasaya adaptasyon ve gelişim için hem işletmelerin hem de ulusların vizyon sahibi olarak gerekli adımları atmaları gerekmektedir. Bu durum karşısında bir toplumda; bilgi, farkındalık ve kullanım oranlarının ölçülmesi gereken en temel yapı taşları vatandaş ve işletmeler olacaktır. Bu bağlamda yapılmış olan araştırmanın iki temel aşaması bulunmaktadır. İlk aşamada ulaşılmak istenen amaç; Türk toplumunun kripto para piyasası hakkındaki farkındalık ve tutumunu ölçmek iken; ikinci aşamadaki amaç ise Türkiye’deki kripto para kullanan işletmelerin motivasyonlarını incelemektir. Bu temel amaçlar doğrultusunda ilgi sırasıyla 154 kişi ile anket ve 10 işletme ile çevrimiçi mülakat yapılmıştır. Elde edilen bulgular neticesinde tartışma ve sonuç kısmında birey-işletme-toplum üçlü skalasında çeşitli çıkarımlarda ve önerilerde bulunulmuştur
Blockchains have become an integral part of many distributed applications, providing a new platform for interaction between system components. Blockchains are perhaps most known for their use in crypto-currency systems, such as Bitcoin and Ethereum, where pseudo-anonymous parties engage in transactions without a trusted third party. Blockchain systems often struggle to meet performance demands of real-word applications, rendering them inappropriate for performance sensitive applications.\nThere is also concerns regarding the immense amount of electrical energy required to securely run existing public blockchain systems. Bitcoin alone consumes more than small countries. Private systems have higher throughput and avoid excessive energy consumption, but have closed membership and do not scale to the same extent.\n\nBoth public and private blockchains rely on some form of membership mechanism providing peers with a view of other participants. Existing systems often employ partial view protocols due to their natural scalability. However, recent work have shown that full view protocols are feasible in practice, and can scale to thousands of participants. With full membership, applications can send messages directly to their destination without any intermediate hops.\n\nThis thesis presents FireChain, which combines a Byzantine fault-tolerant gossip service and full membership, with a proposal for blockchain systems that does not consume excessive energy. We evaluate FireChain's performance through experiments on PlanetLab, and show that it scales beyond hundreds of members.
The commodity industry, the transaction lifecycle of commodities, its value chain and supply chain are complex systems with many parties involved. Ownership of cargoes are determined by who is holding the physical paper, the Bill of Lading. The participants in the industry require constant verification between parties, and this resultsin cumbersome paper-heavy back-office operations which are exposed to human errors. \nThe entire commodity transaction life-cycle involves the value chain and supply chain, and it creates a complicated and long chain involving several intermediaries, each taking a piece of the pie and adds to transaction costs for producers. The roles of intermediaries in the commodity industry can be financing trades, facilitating trade, managing risk, on-site inspection and verification of cargoes, shipping, and logistics.\nBlockchain technology is the technology underlying bitcoins and most of the cryptocurrencies in existence. Bitcoin enabled people to transfer money, peer-to-peer without an intermediary to establish trust and facilitate transactions. Bitcoin has paved the way for further use-cases of the technology, which has a much broader use-case spectrum than just being the underlying technology of cryptocurrencies.\nBlockchain is a decentralized, distributed ledger, where transactions are stored in blocks and secured with cryptography. It allows anyone to execute trade without an intermediary to establish trust between parties. It allows for one single source of the truth between counterparties through enhancing transparency, visibility and availability of transactions data and information.\nBlockchains can be fully transparent, but a blockchain can also allow for privacy. There are different types of blockchain, public/private/hybrid, and each of these types serves its purpose a little bit differently. In a private or hybrid blockchain, information that is sensitive to a certain trade remains private by only allowing the counterparties of that trade transparency into the transactions of that certain trade.\nThe blockchain technology enhances cyber security through decentralization and cryptography. Digital tokens can replace the Bill of Lading to track ownership of cargoes. Smart contracts that self-execute triggered upon a set of predetermined conditions are among the features of blockchain technology. The convenience of blockchain technology, is that anyone at any time can build its own decentralized application on top of already existing blockchain platforms like Ethereum, Hyperledger and others. These factors create for a unique opportunity to digitalize the commodity industry, gaining security, efficiency and opening up possibilities for new trade models in trade finance.
Energy conservation measurements in buildings are more and more popular as they benefit from an intelligent contractual framework called Energy Performance Contracts (EPC), where energy savings are measured as the difference between a predictive baseline model and the actual consumption. While modern predictive models make use of large amounts of data from external sources and increasingly complex algorithms, these two aspects make their use difficult in practice because they need mutual understanding and transparency, requiring the involvement of a third-party for auditing. In this sense, we designed and developed a prototype that overcomes these issues by storing the predictive models and the data in an immutable blockchained data structure using the Ethereum framework. To the best of our knowledge, this is the first working prototype using the blockchain technology applied to EPCs. This paper presents and discusses the technical solutions and best-practice guidelines adopted in this prototype.
Mohammad Ahmad, Abdullah Al-Saleh, Fahad A. Al Masoud
Cryptocurrency subject attracted so many people for the last eight years around the globe. Satoshi’s Nakamoto’s, the founder of the bitcoin cryptocurrency behind this revolutionary change in digital money market. Bitcoin cryptocurrency uses “Power of Work” or simply PoW system as its mining algorithm. But in January of 2016, Ethereum cryptocurrency has launched which adopted a new system called “Power of Stake” or simply PoS that is used in Ethereum as its mining algorithm. This paper explores and compares PoW and PoS systems that is used widely today in cryptocurrencies digital money, concluding the pros and cons for each system with enabling to decide which one is more suitable and stable in digital money market.
Distributed ledger technologies, such as blockchain systems, have in recent years emerged as promising platforms for machine-to-machine commerce and other forms of multi-stakeholder applications. However, despite the potential demonstrated by projects such as Bitcoin, Ethereum, and Hyperledger Fabric, the disk space typically required to host a copy of a ledger may be prohibitively large for many categories of devices. In this paper, we introduce an approach for reducing ledger size in blockchain systems, based on arbitrary pruning predicate functions, allowing each network participant to independently select and remove any already applied transactions. We also show that if only pruning certain ledger transactions, the ability to derive an unmodified state data structure from the remaining transactions is maintained. The approach is validated through a supply chain use case utilizing a modified version of Hyperledger Fabric, in which ledger size is reduced by about 84.49% via selective transaction pruning.
Kazım Rıfat Özyılmaz, Mehmet Ug̃ur Dog̃an, Arda Yurdakul
Today, Internet of Things (IoT) devices are the powerhouse of data generation with their ever-increasing numbers and widespread penetration. Similarly, artificial intelligence (AI) and machine learning (ML) solutions are getting integrated to all kinds of services, making products significantly more "smarter". The centerpiece of these technologies is "data". IoT device vendors should be able keep up with the increased throughput and come up with new business models. On the other hand, AI/ML solutions will produce better results if training data is diverse and plentiful. In this paper, we propose a blockchain-based, decentralized and trustless data marketplace where IoT device vendors and AI/ML solution providers may interact and collaborate. By facilitating a transparent data exchange platform, access to consented data will be democratized and the variety of services targeting end-users will increase. Proposed data marketplace is implemented as a smart contract on Ethereum blockchain and Swarm is used as the distributed storage platform.
Cash-less payment via a variety of credit, debit or prepaid cards is pervasive in our interconnected society, but not so ubiquitous in remote rural regions where network connectivity is intermittent. We proposed a cash-less payment scheme for remote villages based on blockchains that allow maintaining a record of verifiable transactions in a distributed manner. We overcome the limitations of intermittent network connectivity by solely relying on blockchain mining nodes in the village for transaction processing and verification. The bank joins as a peer and monitors node behaviors, rewards miners and processes currency exchanges whenever the connectivity is available. We take advantage of the Ethereum network to develop our solution and demonstrate the feasibility of the proposed system on off-the-shelf computing devices. We emulate a remote village scenario with intermittent network connectivity and show the robustness and reliability of the proposed system.
Abstract Blockchain educational technology has created assessment and management tools for learner credentials that are permanent, transparent and sustainable while giving users direct access. Personal encrypted credentials enable users to shape lifelong learning pathways and personalizes education according to individual values and needs. They allow for the permanent documentation of both formal and informal learning based on transversal competencies, adjustable across the economic sector and responsive to situational needs. Badging was the initial response to online credentialing. Mozilla’s open digital badges have become the unofficial global standard and the specifications remain free. They may be viewed in e-portfolios and social networks. Yet, if issuers cease hosting badges, they become invalid even when authentic. Some experiments with blockchain technology remedy this situation by creating a permanent, secure and sustainable infrastructure for learning records. The MIT Media Lab has produced the bitcoin based Blockcerts; whereas the Knowledge Institute, Open University, UK has developed Ethereum’s Smart Contracts to document Microcredentials (Badges). Both are Open Source products. Most EU nations are experimenting with educational blockchain. The technology creates an infrastructure to document, store and manage credentials and provides learners with a sustainable record of achievements they can control. It also benefits universities by reducing administrative costs and bureaucracy.
Distributed applications based on the Ethereum blockchain have a great advantage in the analysis of the history of group work and the contribution factor to a group project of each group member. In these applications, multiple users share resources and their histories together in a robust way thanks to the characteristics of the blockchain that is practically impossible to be forged or modified. However, there has not yet been developed a scheme for providing a systematic management scheme of a group of users or authentication of the members of the group to allow the members to use shared resources through various access rights.