The blockchain technologic assets can potentially revolutionise the fintech and non-fintech world in term of operations speed, cost reduction, fee avoidance, transparency, immutability, intermediaries remotion and security.Nowadays, hundreds of different blockchains are on the market; however, the most relevant one is by far Ethereum.In the last few years, Ethereum has evolved under many aspects: becoming increasingly efficient, scalable and sustainable.Ethereum was the first network to introduce smart contracts, programs where currencies and assets can be transferred into and which use their code for automatically validating conditions, determining if an asset should go to one person or get back to the sender.Despite the destructive aspect of the current economical architecture, the world juridical framework has been in favour of new payment methods and financial entities. Laws and directives on digital payments has been adopted during these years, and, as a matter of facts, PSD2 is the most groundbreaking for Europe. With its compliance, banks have the obligation to introduce API for new actors, basically, third party providers of financial services; with the purpose of guaranteeing them a full access to customer's bank accounts for performing operations.Both opportunities arising from PSD2 and Ethereum state-of-the-art technologies can be combined to develop distributed blockchain-based application, finalised to transact electronically in a fast risk-less way. The distributed application implemented in the thesis work is an example of decentralized application built on top of Ethereum for performing transactions and transfer currency and assets. This project contains three different modern payment methods: an Ethereum payment, in Ether, the native cryptocurrency of the blockchain; a PSD2 payment, a pan-european instant payment in euro; and a tokens transfer, in points, programmed in a smart contract, following the ERC20-token Ethereum standard.The three kind of payments introduced are perfectly complementary with each other in the system, proving both intra and extra blockchain payments, crypto and non-crypto currency, and using money and tokens. The solution developed involves multiple transactions with different payment methods; furthermore, it is possible to interact with through a user-friendly front end.This thesis work concerns about understanding deeply the blockchain, specifically Ethereum; if this could be a next breakthrough technology and if non-strictly-financial applications can be built on its top. The present thesis work goals are to evaluate the development potential of smart contracts, analysing the system risk and vulnerabilities; to test the advantages on developing distributed applications and to compare costs, fees and speed of these modern methods with the current ones.
Introduction:. OPMEs have been singled out as items that increasingly compromise health care costs and are sometimes among the most expensive materials. Through supply chain management is known the cost containment, and because its unique features and because its homogeneous, decentralized and interconnected platform characteristics offered, Blockchain emerges as a natural solution for supply chain management. Objective: Develop a label based on the Blockchain Ethereum protocol for OPME. Methods: An antecedent search was performed in the databases: (LILACS, Medline, SciELO, Teses USP, Google and Google Scholar). For the development of the system, the methodology was used Design Thinking, which is divided into four phases: Discover, Define, Develop and Deliver. In the Discover phase, interviews were conducted and the Desk survey was produced; in the Define phase, the main functionalities of the system were determined; in the Developing phase, brainstorming sessions were held; and in the Deliver phase, the prototype and the final version of the service were produced. Results: From the Desk survey in the databases, articles for this research were found describing traceability services in supply chain management and articles reporting on Blockchain and Ethereum . No studies were found demonstrating its application. From the interviews and research Desk of the Discover phase, the functionalities and characteristics of the system were defined. The key is the need for an online service using Blockchain Ethereum technology to provide confidence to the relevant information in the OPME value chain. The prototype was developed and improved. The final system features all the functionality defined through Design Thinking Conclusion:. The label based on the Blockchain Ethereum protocol for OPME was designed.
One of the main issues in digital forensics is the management of evidences. From the time of evidence collection until the time of their exploitation in a legal court, evidences may be accessed by multiple parties involved in the investigation that take temporary their ownership. This process, called Chain of Custody (CoC), must ensure that evidences are not altered during the investigation, despite multiple entities owned them, in order to be admissible in a legal court. Currently digital evidences CoC is managed entirely manually with entities involved in the chain required to fill in documents accompanying the evidence. In this paper, we propose a Blockchain-based Chain of Custody (B-CoC) to dematerialize the CoC process guaranteeing auditable integrity of the collected evidences and traceability of owners. We developed a prototype of B-CoC based on Ethereum and we evaluated its performance.
Most languages are given an informal semantics until they are implemented, so the formal semantics comes later. Consequently, there are usually inconsistencies among the informal semantics, the implementation, and the formal semantics. IELE is an LLVM-like language for the blockchain that was specified formally and its implementation, a virtual machine, generated from the formal specification. Moreover, its design was based on problems observed formalizing the semantics of the Ethereum Virtual Machine (EVM) and from formally specifying and verifying EVM programs (also called “smart contracts”), so even the design decisions made for IELE are based on formal specifications. A compiler from Solidity, the predominant high-level language for smart contracts, to IELE has also been implemented, so Ethereum contracts can now also be executed on IELE. The virtual machine automatically generated from the semantics of IELE is shown to be competitive in terms of performance with the state of the art and hence can stand as the de facto implementation of the language in a production setting. Indeed, IOHK, a major blockchain company, is currently experimenting with the IELE VM in order to deploy it as its computational layer in a few months. This makes IELE the first practical language that is designed and implemented as a formal specification. It took only 10 man-months to develop IELE, which demonstrates that the programming language semantics field has reached a level of maturity that makes it appealing over the traditional, adhoc approach even for pragmatic reasons.
Florentin Guth, Valentin Wüstholz, Maria Christakis, Péter Müller
Smart contracts are programs that manage digital assets according to a certain protocol, expressing for instance the rules of an auction. Understanding the possible behaviors of a smart contract is difficult, which complicates development, auditing, and the post-mortem analysis of attacks. This paper presents the first specification mining technique for smart contracts. Our technique extracts the possible behaviors of smart contracts from contract executions recorded on a blockchain and expresses them as finite automata. A novel dependency analysis allows us to separate independent interactions with a contract. Our technique tunes the abstractions for the automata construction automatically based on configurable metrics, for instance, to maximize readability or precision. We implemented our technique for the Ethereum blockchain and evaluated its usability on several real-world contracts.
This Thesis focuses on the methodology implementation and potential impact of a Blockchain platformdesigned to be a new business model for vehicle insurance companies. This technology is a strong tool for industries’ disruption, here the platform is based on Ethereum and the focus is the Automotive Sector. Within this Industry, the proposal is to reformthe way in which vehicle insurance are calculated and marketed. Thus, by matching Blockchain with Internet of Things (IoT), the proposal is a system that measures and analyzes the way each driver behaves in traffic and thereafter automatically issues insurance contracts. In order to measure the impact of this work, some US traffic database were examined. These data relate red light violations, severe vehicle crashes and pedestrian crashes with driver’s characteristics. Among them, the target variable was the driver’s age, since it is a critical factor when regarding new technology adoption rate. Statistical analyzes showed that the proposed platform had a high impact potential for improving the driver behavior and so reducing infractions and traffic accidents. Not only benefits for society as a whole but consumers would be more satisfied paying a tailor made price for their vehicle insurance, and companies would have reduced operating costs and the possibility to take more precise risk investments by depending on each client’s driver behavior.
The historic rise of blockchain-based cryptocurrencies to over $327 billion in market capitalization has sparked significant research efforts studying their reliability, performance, and security. Bitcoin, the highest valued cryptocurrency, has received the most thorough scrutiny, with many studies analyzing its peer properties and network health. In contrast, the network layer for Ethereum, the second-largest cryptocurrency, has gone mostly ignored, even though it employs different algorithms for transaction propagation. \n\nIn this thesis, we perform timing analysis on transactions propagated through Ethereum networks to identify the origin nodes. We build a tool called TxSniper to verify our approach on Ethereum's main network. We find that we can identify the origin with a 70% probability; this method is not always effective due to presence of nodes running clients that use different implementations of transaction propagation.
최근에 ICO(Initial Coin Offering)가 활성화되면서 이더리움 네트워크에 트랜잭션 발생이 짧은 시간에 급증하였고, 그 결과 이더리움의 시간당 거래 처리량이 현저하게 떨어지는 현상이 나타났었다. 본 논문에서는 이러한 현상을 사설 블록체인 환경에서 서로 다른 복잡도를 가진 3가지의 스마트 컨트랙트로 실험하였다. 그 결과, 블록당 트랜잭션의 수가 감소하는 현상을 보이면서 수행속도가 크게 떨어지는 현상이 나타났다. 결과 분석 및 결론에서 성능 저하의 이유를 분석하고, 어떤 스마트 컨트랙트의 특징이 실험 결과에 어떻게 영향을 주었는지 설명한다.
Pietro Danzi, Anders E. Kalør, Čedomir Stefanović, Petar Popovski
The emerging blockchain protocols provide a decentralized architecture that is suitable of supporting Internet of Things (IoT) interactions. However, keeping a local copy of the blockchain ledger is infeasible for low-power and memory-constrained devices. For this reason, they are equipped with lightweight software implementations that only download the useful data structures, e.g. state of accounts, from the blockchain network, when they are updated. In this paper, we consider and analyze a novel scheme, implemented by the nodes of the blockchain network, which aggregates the blockchain data in periodic updates and further reduces the communication cost of the connected IoT devices. We show that the aggregation period should be selected based on the channel quality, the offered rate, and the statistics of updates of the useful data structures. The results, obtained for the Ethereum protocol, illustrate the benefits of the aggregation scheme in terms of a reduced duty cycle of the device, particularly for low signal-to-noise ratios, and the overall reduction of the amount of information transmitted in downlink (e.g., from the wireless base station to the IoT device). A potential application of the proposed scheme is to let the IoT device request more information than actually needed, hence increasing its privacy, while keeping the communication cost constant. In conclusion, our work is the first to provide rigorous guidelines for the design of lightweight blockchain protocols with wireless connectivity.
Arati Baliga, I Subhod, Pandurang Kamat, Siddhartha Chatterjee
Quorum is a permissioned blockchain platform built from the Ethereum codebase with adaptations to make it a permissioned consortium platform. It is one of the key contenders in the permissioned ledger space. Quorum supports confidentiality and privacy of smart contracts and transactions, and crash and Byzantine fault tolerant consensus algorithms. In this paper, we characterize the performance features of Quorum. We study the throughput and latency characteristics of Quorum with different workloads and consensus algorithms that it supports. Through a suite of micro-benchmarks, we explore how certain transaction and smart contract parameters can affect transaction latencies.
Constrained devices in IoT networks often require to outsource resource-heavy computations or data processing tasks. Currently, most of those jobs are done in the centralised cloud. However, with rapidly increasing number of devices and amount of produced data, edge computing represents a much more efficient solution decreasing the cost, the delay and improves users' privacy. To enable wide deployment of execution nodes at the edge, the requesting devices require a way to pay for submitted tasks. We present SPOC - a secure payment system for networks where nodes distrust each other. SPOC allows any node to execute tasks, includes result verification and enforce users' proper behaviour without 3rd parties, replication or costly proof of computations. We implement our system using Ethereum Smart Contracts and Intel SGX and present first evaluation proving its security and low usage cost.
Introduzione alla blockchain. Definizione di blockchain. Le infrastrutture dell'informazione. Le blockchain come infrastrutture dell'informazione. Bitcoin ed ethereum a confronto.
One of the most important components in a public blockchain like Bitcoin and Ethereum is the authenticated data structure that keeps track of all block data, transactions, and the world state (account balance, smart contract states, etc.) Thanks to authenticated data structures, lightweight nodes only need to store authentication information and can delegate queries to those nodes with a full replica of data and the authenticated data structure. The lightweight nodes can trust the query results after verifying against the authentication information. It is also critical to have enough nodes in the network that are equipped with the authenticated data structure to ensure scalability and availability, which is especially important for public blockchains. Therefore, every public blockchain highly encourages users to download the authenticated data structure as the first step.\n\nFetching all elements from the entire authenticated data structure is a novel query type that has not gathered attention in the past. We describe this new emerging query type in the three-party authenticated data structure (ADS). We improve the design and implementation of the authenticated data structure so that the new query type is well-supported. We specifically apply the improvements to the Ethereum blockchain network. With our proposed ADS system in Ethereum, we improve Ethereum state synchronization performance by 216 times.
Francesco Bortolussi, Zeger Hoogeboom, Frank W. Takes
Cryptocurrencies such as Bitcoin and Ethereum have recently gained a lot of popularity, not only as a digital form of currency but also as an investment vehicle. Online marketplaces and exchanges allow users across the world to convert between dozens of different cryptocurrencies and regular currencies such as euros or dollars. Due to the novelty of this concept, the volatility of these markets and the differences in maturity and usage of particular marketplaces, currency pairs may appear at multiple marketplaces but at different trading prices. This paper proposes a novel algorithmic approach to take advantage of these mispricings and capitalize upon the pricing differences that exist between exchanges and currency pairs. To do so, we model each combination of a currency and a market as one node in a graph. A directed link between two nodes indicates that a conversion between these two currency/market pairs is possible. The weight of the link relates to the exchange rate of executing this particular currency exchange. To leverage the mispricings, we seek for cycles in the graph such that upon multiplying the weights of the links in the cycle, a value greater than 1 is found and thus a profit can be made. Our goal is to do this efficiently, without exhaustively enumerating all possible cycles in the graph. Therefore, we convert our data and address the problem in terms of finding minimum weight triangles in graphs with integer weights, for which efficient algorithms can be utilized. We experiment with parameter settings (heuristics) related to the conversion of exchange rate data into integer weight values. We show that our approach improves upon a reasonable baseline algorithm in terms of computation time. Furthermore, using a real-world dataset, we demonstrate how the obtained minimal weight cycles indeed unveil a number of currency exchange cycles that result in a net profit.
The recent emergence of cryptocurrencies such as Bitcoin and Ethereum has posed possible alternatives to global payments as well as financial assets around the globe, making investors and financial regulators aware of the importance of modeling them correctly. The Lvy's stable distribution is one of the attractive distributions that well describes the fat tails and scaling phenomena in economic systems. In this paper, we show that the behaviors of price fluctuations in emerging cryptocurrency markets can be characterized by a non-Gaussian Lvy's stable distribution with ' 1:4 under certain conditions on time intervals ranging roughly from 30 min to 4 h. Our arguments are developed under quantitative valuation defined as a distance function using the Parseval's relation in addition to the theoretical background of the General Central Limit Theorem (GCLT). We also discuss the model-fitting for returns by employing the method based on likelihood ratios. Even though the cubic power-law model is a better fitting model than the Lvy's stable model in the tail part of returns, the Lvy's stable model outperforms the fit for the entire and wider range of returns. Our approach can be extended for further analysis of statistical properties and contribute to developing proper applications for financial modeling.
The paper presents Tendermint, a new protocol for ordering events in a distributed network under adversarial conditions. More commonly known as Byzantine Fault Tolerant (BFT) consensus or atomic broadcast, the problem has attracted significant attention in recent years due to the widespread success of blockchain-based digital currencies, such as Bitcoin and Ethereum, which successfully solved the problem in a public setting without a central authority. Tendermint modernizes classic academic work on the subject and simplifies the design of the BFT algorithm by relying on a peer-to-peer gossip protocol among nodes.
Kriptografski lanac blokova (eng. Blockchain) je distribuirana baza podataka koja održava rastuću listu transakcija te koristi kriptografiju kako bi osigurala integritet i neporecivost pohranjenih podataka. Jedna novija primjena lanca blokova je izgradnja sustava pametnih ugovora. Iako se svakodnevno pojavljuje mnoštvo distribuiranih aplikacija koje koriste pametne ugovore, nejasno je koja točno sigurnosna svojstva ti pametni ugovori pružaju krajnjim korisnicima. U sklopu ovog rada napravljen je pregled relevantnih ranjivosti na platformi Ethereum, također su primjerima ilustrirani napadi koji izrabljuju te ranjivosti. Konačno, u poglavlju 4 objašnjene su sigurnosne preporuke pomoću kojih se opisane ranjivosti mogu izbjeći.
Decentralized cryptocurrencies feature the use of blockchain to transfer values among peers on networks without central agency. Smart contracts are programs running on top of the blockchain consensus protocol to enable people make agreements while minimizing trusts. Millions of smart contracts have been deployed in various decentralized applications. The security vulnerabilities within those smart contracts pose significant threats to their applications. Indeed, many critical security vulnerabilities within smart contracts on Ethereum platform have caused huge financial losses to their users. In this work, we present ContractFuzzer, a novel fuzzer to test Ethereum smart contracts for security vulnerabilities. ContractFuzzer generates fuzzing inputs based on the ABI specifications of smart contracts, defines test oracles to detect security vulnerabilities, instruments the EVM to log smart contracts runtime behaviors, and analyzes these logs to report security vulnerabilities. Our fuzzing of 6991 smart contracts has flagged more than 459 vulnerabilities with high precision. In particular, our fuzzing tool successfully detects the vulnerability of the DAO contract that leads to USD 60 million loss and the vulnerabilities of Parity Wallet that have led to the loss of USD 30 million and the freezing of USD 150 million worth of Ether.
Blockchain platforms, such as Ethereum, allow a set of actors to maintain a ledger of transactions without relying on a central authority and to deploy scripts, called smart contracts, that are executed whenever certain transactions occur. These features can be used as basic building blocks for executing collaborative business processes between mutually untrusting parties. However, implementing business processes using the low-level primitives provided by blockchain platforms is cumbersome and error-prone. In contrast, established business process management systems, such as those based on the standard Business Process Model and Notation (BPMN), provide convenient abstractions for rapid development of process-oriented applications. This article demonstrates how to combine the advantages of a business process management system with those of a blockchain platform. The article introduces a blockchain-based BPMN execution engine, namely Caterpillar. Like any BPMN execution engine, Caterpillar supports the creation of instances of a process model and allows users to monitor the state of process instances and to execute tasks thereof. The specificity of Caterpillar is that the state of each process instance is maintained on the (Ethereum) blockchain and the workflow routing is performed by smart contracts generated by a BPMN-to-Solidity compiler. The Caterpillar compiler supports a large array of BPMN constructs, including subprocesses, multi-instances activities and event handlers. The paper describes the architecture of Caterpillar, and the interfaces it provides to support the monitoring of process instances, the allocation and execution of work items, and the execution of service tasks.
Blockchain platforms, such as Ethereum, allow a set of actors to maintain a\nledger of transactions without relying on a central authority and to deploy\nscripts, called smart contracts, that are executed whenever certain\ntransactions occur. These features can be used as basic building blocks for\nexecuting collaborative business processes between mutually untrusting parties.\nHowever, implementing business processes using the low-level primitives\nprovided by blockchain platforms is cumbersome and error-prone. In contrast,\nestablished business process management systems, such as those based on the\nstandard Business Process Model and Notation (BPMN), provide convenient\nabstractions for rapid development of process-oriented applications. This\narticle demonstrates how to combine the advantages of a business process\nmanagement system with those of a blockchain platform. The article introduces a\nblockchain-based BPMN execution engine, namely Caterpillar. Like any BPMN\nexecution engine, Caterpillar supports the creation of instances of a process\nmodel and allows users to monitor the state of process instances and to execute\ntasks thereof. The specificity of Caterpillar is that the state of each process\ninstance is maintained on the (Ethereum) blockchain and the workflow routing is\nperformed by smart contracts generated by a BPMN-to-Solidity compiler. The\nCaterpillar compiler supports a large array of BPMN constructs, including\nsubprocesses, multi-instances activities and event handlers. The paper\ndescribes the architecture of Caterpillar, and the interfaces it provides to\nsupport the monitoring of process instances, the allocation and execution of\nwork items, and the execution of service tasks.\n