Blockchain Papers

Gaby G. Dagher, Jordan Mohler, Matea Milojkovic, Praneeth Babu Marella

No abstract is available for this record.

Ivica Nikolić, Aashish Kolluri, Ilya Sergey, Prateek Saxena · 5 authors

Smart contracts---stateful executable objects hosted on blockchains like Ethereum---carry billions of dollars worth of coins and cannot be updated once deployed. We present a new systematic characterization of a class of trace vulnerabilities, which result from analyzing multiple invocations of a contract over its lifetime. We focus attention on three example properties of such trace vulnerabilities: finding contracts that either lock funds indefinitely, leak them carelessly to arbitrary users, or can be killed by anyone. We implemented MAIAN, the first tool for precisely specifying and reasoning about trace properties, which employs inter-procedural symbolic analysis and concrete validator for exhibiting real exploits. Our analysis of nearly one million contracts flags 34,200 (2,365 distinct) contracts vulnerable, in 10 seconds per contract. On a subset of3,759 contracts which we sampled for concrete validation and manual analysis, we reproduce real exploits at a true positive rate of 89%, yielding exploits for3,686 contracts. Our tool finds exploits for the infamous Parity bug that indirectly locked 200 million dollars worth in Ether, which previous analyses failed to capture.

Brice Tonnellier

No abstract is available for this record.

Patrick G. Sylim, Fang Liu, Alvin Marcelo, Paul Fontelo

<sec> <title>BACKGROUND</title> Drug counterfeiting is a global problem with significant risks to consumers and the general public. In the Philippines, 30% of inspected drug stores in 2003 were found with substandard/spurious/falsely-labeled/falsified/counterfeit drugs. The economic burden on the population drug expenditures and on governments is high. The Philippine Food and Drug Administration (FDA) encourages the public to check the certificates of product registration and report any instances of counterfeiting. The National Police of Philippines responds to such reports through a special task force. However, no literature on its impact on the distribution of such drugs were found. Blockchain technology is a cryptographic ledger that is allegedly immutable through repeated sequential hashing and fault-tolerant through a consensus algorithm. This project will develop and test a pharmacosurveillance blockchain system that will support information sharing along the official drug distribution network. </sec> <sec> <title>OBJECTIVE</title> This study aims to develop a pharmacosurveillance blockchain system and test its functions in a simulated network. </sec> <sec> <title>METHODS</title> We are developing a Distributed Application (DApp) that will run on smart contracts, employing Swarm as the Distributed File System (DFS). Two instances will be developed: one for Ethereum and another for Hyperledger Fabric. The proof-of-work (PoW) consensus algorithm of Ethereum will be modified into a delegated proof-of-stake (DPoS) or practical Byzantine fault tolerance (PBFT) consensus algorithm as it is scalable and fits the drug supply chain environment. The system will adopt the GS1 pedigree standard and will satisfy the data points in the data standardization guidelines from the US FDA. Simulations will use the following 5 nodes: for FDA, manufacturer, wholesaler, retailer, and the consumer portal. </sec> <sec> <title>RESULTS</title> Development is underway. The design of the system will place FDA in a supervisory data verification role, with each pedigree type–specific data source serving a primary data verification role. The supply chain process will be initiated by the manufacturer, with recursive verification for every transaction. It will allow consumers to scan a code printed on the receipt of their purchases to review the drug distribution history. </sec> <sec> <title>CONCLUSIONS</title> Development and testing will be conducted in a simulated network, and thus, results may differ from actual practice. The project being proposed is disruptive; once tested, the team intends to engage the Philippine FDA to discuss implementation plans and formulate policies to facilitate adoption and sustainability. </sec> <sec> <title>REGISTERED REPORT IDENTIFIER</title> RR1-10.2196/10163 </sec>

Gerald Spindler

Die Digitalisierung erfasst alle Lebens- und Rechtsbereiche, auch das Gesellschaftsrecht. Der Beitrag befasst sich mit den Einflüssen der Digitalisierung auf die verschiedenen Formen der Kommunikation im Gesellschaftsrecht, sei es der virtuellen Gesellschafterversammlung oder des Einsatzes digitaler Medien in den Organen, aber auch gegenüber potentiellen Investoren. Dabei werden die jeweiligen rechtlichen Rahmenbedingungen auch jenseits des Gesellschaftsrechts beleuchtet, etwa medien- oder datenschutzrechtliche Fragen. Die Digitalisierung wirkt sich aber auch auf die Haftung der Organe aus, indem mehr verfügbare Daten und verbesserte Algorithmen dazu führen, dass die Organe die verbesserten Informationen zur Entscheidungsfindung nutzen müssen. Umgekehrt ist IT-Sicherheit heute „Chefsache“ geworden, da durch die Digitalisierung der Wertschöpfungsprozesse Unternehmen bei Ausfall ihrer IT-Systeme in ihrer Existenz bedroht werden können. Ferner ermöglicht die neue Technologie der Blockchain die eindeutige Nachvollziehung von Transaktionen, damit auch von Abstimmungen, bis hin zum Einsatz in der Rechnungslegung. Besondere Fragen werfen neue Investitionsformen unter Einsatz der Blockchain-Technologie auf, etwa die DAO Ethereum. Abschließend wird ein Blick auf die Formen der engen vertraglichen Kooperation bei Industrie 4.0 geworfen.

Tshilidzi Marwala, Bo Xing

It is undeniable that artificial intelligence (AI) and blockchain concepts are spreading at a phenomenal rate. Both technologies have distinct degree of technological complexity and multi-dimensional business implications. However, a common misunderstanding about blockchain concept, in particular, is that blockchain is decentralized and is not controlled by anyone. But the underlying development of a blockchain system is still attributed to a cluster of core developers. Take smart contract as an example, it is essentially a collection of codes (or functions) and data (or states) that are programmed and deployed on a blockchain (say, Ethereum) by different human programmers. It is thus, unfortunately, less likely to be free of loopholes and flaws. In this article, through a brief overview about how artificial intelligence could be used to deliver bug-free smart contract so as to achieve the goal of blockchain 2.0, we to emphasize that the blockchain implementation can be assisted or enhanced via various AI techniques. The alliance of AI and blockchain is expected to create numerous possibilities.

Yuanyu Zhang, Shoji Kasahara, Yulong Shen, Xiaohong Jiang · 5 authors

This paper investigates a critical access control issue in the Internet of Things (IoT). In particular, we propose a smart contract-based framework, which consists of multiple access control contracts (ACCs), one judge contract (JC), and one register contract (RC), to achieve distributed and trustworthy access control for IoT systems. Each ACC provides one access control method for a subject-object pair, and implements both static access right validation based on predefined policies and dynamic access right validation by checking the behavior of the subject. The JC implements a misbehavior-judging method to facilitate the dynamic validation of the ACCs by receiving misbehavior reports from the ACCs, judging the misbehavior and returning the corresponding penalty. The RC registers the information of the access control and misbehavior-judging methods as well as their smart contracts, and also provides functions (e.g., register, update, and delete) to manage these methods. To demonstrate the application of the framework, we provide a case study in an IoT system with one desktop computer, one laptop and two Raspberry Pi single-board computers, where the ACCs, JC, and RC are implemented based on the Ethereum smart contract platform to achieve the access control.

Ke Wang

The thesis addresses the advantages that data visualization and semantics can bring to blockchain decentralized applications. It provides a visual tool for browsing and debugging on events over Ethereum blockchain and proposes a method to integrate Ethereum smart contract with semantics. By implementing this method, users are able to conduct knowledge reasoning, tracing and querying with the help of semantic-reinforced visualization by building up a semantic resource layer upon the basic Ethereum blockchain infrastructure. Such proof-of-concept method is examined on a case study of network function virtualization, and the utilization of semantic-reinforced visualization is verified in practical scenarios.

Victor Miranda Palacios

No abstract is available for this record.

Roberto Tonelli, G. A. Pierro, Marco Ortu, Giuseppe Destefanis

Smart contracts (SC) are software programs that reside and run over a blockchain. The code can be written in different languages with the common purpose of implementing various kinds of transactions onto the hosting blockchain. They are ruled by the blockchain infrastructure with the intent to automatically implement the typical conditions of traditional contracts. Programs must satisfy context-dependent constraints which are quite different from traditional software code. In particular, since the bytecode is uploaded in the hosting blockchain, the size, computational resources, interaction between different parts of the program are all limited. This is true even if the specific programming languages implement more or less the same constructs as that of traditional languages: there is not the same freedom as in normal software development. The working hypothesis used in this article is that Smart Contract specific constraints should be captured by specific software metrics (that may differ from traditional software metrics). We tested this hypothesis on 85K Smart Contracts written in Solidity and uploaded on the Ethereum blockchain. We analyzed Smart Contracts from two repositories "Etherscan" and "Smart Corpus" and we computed the statistics of a set of software metrics related to Smart Contracts and compared them to the metrics extracted from more traditional software projects. Our results show that generally, Smart Contract metrics have more restricted ranges than the corresponding metrics in traditional software systems. Some of the stylized facts, like power law in the tail of the distribution of some metrics, are only approximate but the lines of code follow a log-normal distribution which reminds us of the same behaviour already found in traditional software systems.

Haikel Magrahi, Nouha Omrane, Olivier Senot, Rakia Jaziri

Blockchains, such as Bitcoin and Ethereum and their respective P2P networks have seen significant adoption in many sectors in the past few years. All these technologies that use the Blockchain pattern show that it is possible to rebuild any transactional system with better performance without relying on any trusted parties to manage transactions between peers. This insight has lead many companies to invest millions to understand the technology and to find a way to migrate from centralized to decentralized solutions. These solutions need to store large amounts of data in a secure and confidential way. Many distributed storage systems now exist using Blockchain technology (Cloud, FileSystems, etc.). But none of the tools proposed are able to manage the document life cycle nor archive documents based on regulatory compliance. In this paper, we describe our protocol named NFB (Notarizing Files over the Blockchain). This protocol ensures the communication between two systems: a permissive Blockchain and a secured centralized archiving Document Management System. The method described is used to allow users to archive, control, analyze and validate their transactions in a system that offers confidentiality, security and distribution features.

Pascal Urien

This paper introduces some trust issues for blockchain transactions. Such transactions rely on ECDSA signature based on 32 bytes secret keys. Because these keys can be stolen or hacked, we suggest to prevent these risks by using javacard secure elements. We detailed the interface of a Crypto Currency Smart Card (CCSC) designed over a JC3.04 standard platform. We details two use cases. First deals with deployment of the CCSC application in low cost low power object powered by an open hardware (arduino) platform, and integrates sensor data in ethereum transactions. Second proposes the deployment in the cloud of CCSC javacards plugged to RACS servers, in order to enable the remote and safe use of ECDSA signature.

Joost de Kruijff, Hans Weigand

Smart contracts gain rapid exposure since the inception of blockchain<br/>technology. Today's smart contracts are coded in non-mainstream<br/>procedural programming languages (e.g. Solidity for Ethereum),<br/>which lifts the requirement to draft enterprise ready smart contract to<br/>both a legal professional and a programmer instead of only the former.<br/>In search for a smart contract language that reduces the threshold to<br/>draft one, this conceptual paper elaborates how business logic can be<br/>converted to executable code for commitment-based smart contracts.<br/>Hereby, a contract is viewed as a set of reciprocal commitments. The<br/>smart contract ensures the automated execution of all or most of these<br/>commitments. In order to leverage its event processing capabilities,<br/>Reaction RuleML has been used to appropriately represent the<br/>elements and working of passive and active rules within a<br/>commitment based smart.

Ence Zhou, Hua Song, Bingfeng Pi, Jun Sun · 7 authors

Currently, Bitcoin and Ethereum are the two most popular cryptocurrency systems, especially Ethereum. It permits complex financial transactions or rules through scripts, which is called smart contracts. Since Ethereum smart contracts hold millions of dollars, their execution correctness is crucial against attacks which aim at stealing the assets. In this paper, we proposed a security assurance method for smart contract source code to find potential security risks. It contains two main functions, the first is syntax topological analysis of smart contract invocation relationship, to help developers to understand their code structure clearly; the second is logic risk (which may lead to vulnerabilities) detection and location, and label results on topology diagram. For developers' convenience, we have built a static analysis tool called SASC to generate topology diagram of invocation relationship and to find potential logic risks. We have made an evaluation on 2,952 smart contracts, experiment results proved that our method is intuitive and effective.

Andreas Unterweger, Fabian Knirsch, Christoph Leixnering, Dominik Engel

Real-world smart contracts which preserve the privacy of both, their users and their data, have barely been proposed theoretically, let alone been implemented practically. In this paper, we are the first to implement a privacy-preserving protocol from the energy domain as a smart contract in Ethereum. We elaborate on and present our implementation as well as our practical findings, including more or less subtle traps and pitfalls. Despite major optimizations to our implementation, we find that while it is currently possible, it is not feasible to implement a privacy-preserving protocol of modest complexity in the Ethereum blockchain due to the high cost of operation and the lack of privacy by design.

Andra Anoaica, Hugo Levard

One of the most popular platform based on blockchain technology is Ethereum. Internal activity on this public blockchain is analyzed both from a quantitative and qualitative point of view. In a first part, it is shown that the creation of the Ethereum Alliance consortium has been a game changer in the use of the technology. In a second part, the network robustness against attacks is investigated from a graph point of view, as well as the distribution of internal activity among users. Addresses of great influence were identified, and allowed to formulate conjectures on the current usage of this technology.

Beltrán Borja Fiz Pontiveros, Robert Norvill, Radu State

In this work we propose a compression method for smart contracts deployed in the Ethereum blockchain. By taking advantage of the repetition of sections of bytecode among multiple smart contracts previously deployed in the Ethereum blockchain we propose a new pseudo opcode that acts as a pointer that will allow smart contracts to reuse previously deployed code. We show that our proposed algorithm achieves space savings of up to 75% in a dataset of deployed Ethereum smart contracts bytecode, on par with other state of the art compression algorithms while remaining compatible with other methods currently in use for space reduction.

Yining Hu, Ahsan Manzoor, Parinya Ekparinya, Madhusanka Liyanage · 8 authors

Digital banking as an essential service can be hard to access in remote, rural regions where the network connectivity is unavailable or intermittent. The payment operators like Visa and Mastercard often face difficulties reaching these remote, rural areas. Although micro-banking has been made possible by short message service or unstructured supplementary service data messages in some places, their security flaws and session-based nature prevent them from wider adoption. Global-level cryptocurrencies enable low-cost, secure, and pervasive money transferring among distributed peers, but are still limited in their ability to reach people in remote communities. We propose a blockchain-based digital payment scheme that can deliver reliable services on top of unreliable networks in remote regions. We focus on a scenario where a community-run base station provides reliable local network connectivity while intermittently connects to the broader Internet. We take advantage of the distributed verification guarantees of the Blockchain technology for financial transaction verification and leverage smart contracts for secure service management. In the proposed system, payment operators deploy multiple proxy nodes that are intermittently connected to the remote communities where the local blockchain networks, such as Ethereum are composed of miners, vendors, and regular users. Through probabilistic modeling, we devise design parameters for the blockchain network to realize robust operation over the top of the unreliable network. Furthermore, we show that the transaction processing time will not be significantly impacted due to the network unreliability through extensive emulations on a private Ethereum network. Finally, we demonstrate the practical feasibility of the proposed system by developing Near Field Communication (NFC)-enabled payment gateways on Raspberry-Pis, a mobile wallet application and mining nodes on off-the-shelf computers.

Dominik Harz, Magnus Boman

Permission-less blockchains can realise trustless trust, albeit at the cost of limiting the complexity of computation tasks. To explain the implications for scalability, we have implemented a trust model for smart contracts, described as agents in an open multi-agent system. Agent intentions are not necessarily known and autonomous agents have to be able to make decisions under risk. The ramifications of these general conditions for scalability are analysed for Ethereum and then generalised to other current and future platforms.

Sarah Azouvi, Patrick McCorry, Sarah Meiklejohn

Consensus protocols inherently rely on the notion of leader election, in which one or a subset of participants are temporarily elected to authorize and announce the network's latest state. While leader election is a well studied problem, the rise of distributed ledgers (i.e., blockchains) has led to a new perspective on how to perform large-scale leader elections via solving a computationally difficult puzzle (i.e., proof of work). In this paper, we present Caucus, a large-scale leader election protocol with minimal coordination costs that does not require the computational cost of proof-of-work. We evaluate Caucus in terms of its security, using a new model for blockchain-focused leader election, before testing an implementation of Caucus on an Ethereum private network. Our experiments highlight that one variant of Caucus costs only $0.10 per leader election if deployed on Ethereum.

Shelly Grossman, Ittai Abraham, Guy Golan-Gueta, Yan Michalevsky · 7 authors

Callbacks are essential in many programming environments, but drastically\ncomplicate program understanding and reasoning because they allow to mutate\nobject's local states by external objects in unexpected fashions, thus breaking\nmodularity. The famous DAO bug in the cryptocurrency framework Ethereum,\nemployed callbacks to steal $150M. We define the notion of Effectively Callback\nFree (ECF) objects in order to allow callbacks without preventing modular\nreasoning.\n An object is ECF in a given execution trace if there exists an equivalent\nexecution trace without callbacks to this object. An object is ECF if it is ECF\nin every possible execution trace. We study the decidability of dynamically\nchecking ECF in a given execution trace and statically checking if an object is\nECF. We also show that dynamically checking ECF in Ethereum is feasible and can\nbe done online. By running the history of all execution traces in Ethereum, we\nwere able to verify that virtually all existing contracts, excluding the DAO or\ncontracts with similar known vulnerabilities, are ECF. Finally, we show that\nECF, whether it is verified dynamically or statically, enables modular\nreasoning about objects with encapsulated state.\n

Aditya Asgaonkar, Pranav Palande, Ramprasad Joshi

The increasing popularity of Bitcoin, Ethereum and other cryptocurrencies has led to a rising interest in its underlying blockchain technology. Blockchains serve as distributed ledgers, and are fundamentally different from traditional distributed databases. In view of this large scale adoption of blockchain technology, it is of interest to analyze the performance of the underlying mechanisms in peer-to-peer blockchain networks.

Claudia Pop, Tudor Cioara, Claudia Antal, Ionuț Anghel · 6 authors

In this paper, we investigate the use of decentralized blockchain mechanisms for delivering transparent, secure, reliable, and timely energy flexibility, under the form of adaptation of energy demand profiles of Distributed Energy Prosumers, to all the stakeholders involved in the flexibility markets (Distribution System Operators primarily, retailers, aggregators, etc.). In our approach, a blockchain based distributed ledger stores in a tamper proof manner the energy prosumption information collected from Internet of Things smart metering devices, while self-enforcing smart contracts programmatically define the expected energy flexibility at the level of each prosumer, the associated rewards or penalties, and the rules for balancing the energy demand with the energy production at grid level. Consensus based validation will be used for demand response programs validation and to activate the appropriate financial settlement for the flexibility providers. The approach was validated using a prototype implemented in an Ethereum platform using energy consumption and production traces of several buildings from literature data sets. The results show that our blockchain based distributed demand side management can be used for matching energy demand and production at smart grid level, the demand response signal being followed with high accuracy, while the amount of energy flexibility needed for convergence is reduced.

Yhlas Sovbetov

This paper examines factors that influence prices of most common five cryptocurrencies such Bitcoin, Ethereum, Dash, Litecoin, and Monero over 2010-2018 using weekly data. The study employs ARDL technique and documents several findings. First, cryptomarket-related factors such as market beta, trading volume, and volatility appear to be significant determinant for all five cryptocurrencies both in short- and long-run. Second, attractiveness of cryptocurrencies also matters in terms of their price determination, but only in long-run. This indicates that formation (recognition) of the attractiveness of cryptocurrencies are subjected to time factor. In other words, it travels slowly within the market. Third, SP500 index seems to have weak positive long-run impact on Bitcoin, Ethereum, and Litcoin, while its sign turns to negative losing significance in short-run, except Bitcoin that generates an estimate of -0.20 at 10% significance level. Lastly, error-correction models for Bitcoin, Etherem, Dash, Litcoin, and Monero show that cointegrated series cannot drift too far apart, and converge to a long-run equilibrium at a speed of 23.68%, 12.76%, 10.20%, 22.91%, and 14.27% respectively.