Smart contracts" are decentralized agreements built in computer code and stored on a blockchain.Proponents imagine a future where commerce takes place exclusively using smart contracts, avoiding the high costs of contract drafting, judicial intervention, opportunistic behavior, and the inherent ambiguities of written language.These decentralized code-only contracts are part of a decades-long quest to eliminate supposed inefficiencies in traditional written agreements.Electronic data interchange (EDI), a contracting technology from the 1970s, was designed with the same goal and garnered similar fanfare.Commentators at the time imagined a revolution in the way firms transacted and a full shift away from anything resembling a paper contract.Ultimately EDI failed to achieve these goals-it empowered, rather than circumvented, human decisionmakers along with their "inefficient" way of forming agreements.In doing so, EDI successfully reduced some transaction costs while preserving efficient forms of contractual flexibility.Smart contracts are indeed more technologically sophisticated than EDI.Smart contract scripting languages offer a broader range of operations and greater scalability.Smart contracts are capable of seamlessly integrating with the operational and financial systems at the core of modern firms, whereas EDI transactions occurred in very early digital environments that required human intermediaries.
The blockchain technology started as the innovation that powered the cryptocurrency Bitcoin. But in recent years, leaders in finance, banking, and many more companies has given this new innovation more attention than ever before. They seek a new technology to replace their system which are often inefficient and costly to operate. However, one of the reasons why it not possible to use a blockchain right away is because of the poor performance. Public blockchains, where anyone can participate, can only process a couple of transaction per second and is therefore far from usable in the world of finance. Permissioned blockchains is another type of blockchain where only a restricted set of users have the rights to decide what will be recorded in the blockchain. This allows permissioned blockchains to have a number of advantages over public blockchains. Most notably is the ability to split the network into segments where only a subset of nodes needs to validate transactions to aparticular application, allowing the use of parallel computing and better scaling. Moreover, the validating nodes can be trusted, allowing the use of consensus algorithm which offer much more through put. In this paper, we compare public blockchain with permissioned blockchain and address the notable trade-offs: decentralization, scalability and security, in the different blockchain networks. Furthermore, we examine the potential of using a permissioned blockchain to replace the old systems used in financial institutes and banks by launching a Hyperledger Fabric network and run stress tests. It is apparent that with less decentralization, the performance and scalability of Hyperledger Fabric network is improved and it is feasible that permissioned blockchain can be used in finance.
Bruno Rodrigues, Thomas Bocek, Andri Lareida, David Hausheer · 6 authors
Abstract The rapid growth in the number of insecure portable and stationary devices and the exponential increase of traffic volume makes Distributed Denial-of-Service (DDoS) attacks a top security threat to services provisioning. Existing defense mechanisms lack resources and flexibility to cope with attacks by themselves, and by utilizing other’s companies resources, the burden of the mitigation can be shared. Emerging technologies such as blockchain and smart contracts allows for the sharing of attack information in a fully distributed and automated fashion. In this paper, the design of a novel architecture is proposed by combining these technologies introducing new opportunities for flexible and efficient DDoS mitigation solutions across multiple domains. Main advantages are the deployment of an already existing public and distributed infrastructure to advertise white or blacklisted IP addresses, and the usage of such infrastructure as an additional security mechanism to existing DDoS defense systems, without the need to build specialized registries or other distribution mechanisms, which enables the enforcement of rules across multiple domains.
In this paper, we explore remarkable similarities between multi-transactional behaviors of smart contracts in cryptocurrencies such as Ethereum and classical problems of shared-memory concurrency. We examine two real-world examples from the Ethereum blockchain and analyzing how they are vulnerable to bugs that are closely reminiscent to those that often occur in traditional concurrent programs. We then elaborate on the relation between observable contract behaviors and well-studied concurrency topics, such as atomicity, interference, synchronization, and resource ownership. The described contracts-as-concurrent-objects analogy provides deeper understanding of potential threats for smart contracts, indicate better engineering practices, and enable applications of existing state-of-the-art formal verification techniques.
Daniele Magazzeni, Peter McBurney, William L. Nash
Smart contracts might encode legal contracts written in natural language to represent the contracting parties' shared understandings and intentions. The issues and research challenges involved in the validation and verification of smart contracts, particularly those running over blockchains and distributed ledgers, are explored.
Smart contracts are computer programs that can be consistently executed by a network of mutually distrusting nodes, without the arbitration of a trusted authority. Because of their resilience to tampering, smart contracts are appealing in many scenarios, especially in those which require transfers of money to respect certain agreed rules (like in financial services and in games). Over the last few years many platforms for smart contracts have been proposed, and some of them have been actually implemented and used. We study how the notion of smart contract is interpreted in some of these platforms. Focussing on the two most widespread ones, Bitcoin and Ethereum, we quantify the usage of smart contracts in relation to their application domain. We also analyse the most common programming patterns in Ethereum, where the source code of smart contracts is available.
The DPM 2019 and CBT 2019 proceedings present the two ESORICS workshops on data privacy management and cryptocurrencies and blockchain technology. The papers are organized in parts on smart contracts and applications; and payment systems, privacy and mining; privacy preserving data analysis; etc.
Stefan Dziembowski, Lisa Eckey, Sebastian Faust, Daniel Malinowski
Payment channels emerged recently as an efficient method for performing cheap micropayments in cryptocurrencies. In contrast to traditional on-chain transactions, payment channels have the advantage that they allow for nearly unlimited number of transactions between parties without involving the blockchain. In this work, we introduce Perun, an off-chain channel system that offers a new method for connecting channels that is more efficient than the existing technique of ``routing transactions'' over multiple channels. To this end, Perun introduces a technique called ``virtual payment channels'' that avoids involvement of the intermediary for each individual payment. In this paper we formally model and prove security of this technique in the case of one intermediary, who can be viewed as a ``payment hub'' that has direct channels with several parties. Our scheme works over any cryptocurrency that provides Turing-complete smart contracts. As a proof of concept, we implemented Perun's smart contracts in Ethereum.
Open access
2 source records
Blockchain Technology Applications and Security
Cryptography and Data Security
Advanced Steganography and Watermarking Techniques
Ethereum represents the second generation of blockchain technology by providing\nan open and global computing platform which allows the exchange of cryptocurrency\n(Ether) and the development of self-verifying smart contract applications.\nSmart contracts present a foundation for possessing digital assets and a variety of\ndecentralized applications within the blockchain area. Ethereum and smart contracts\nare public, distributed and immutable, as such, they are prone to vulnerabilities\nsourcing from simple coding mistakes of developers.\n\nMotivated by the security breaches and recurring financial losses in smart contracts,\nwe aim to advance the field of security in smart contract programming.\nThe main objective is to aid smart contract developers by providing a taxonomy of\nall known security issues and by inspecting the security code analysis tools used\nto identify those vulnerabilities. Based on previous research as well as attacks on\nEthereum smart contracts, we propose an updated taxonomy which categorizes\nall known vulnerabilities within their architectural and severity level. Our second\nproposed taxonomy is a novel categorization of security tools on Ethereum.\n\nFurthermore, we conduct the investigation of security code analysis tools on\nEthereum by assessing their effectiveness and accuracy. In particular, we analyze\nfour security tools, namely, Oyente, Securify, Remix, and SmartCheck. The results\nindicate that there are overall inconsistencies between the tools on different security\nproperties. SmartCheck outperformed the other tools in terms of effectiveness,\nwhereas Oyente performed the best in terms of accuracy. Furthermore, based on\nthe limitations we identified, we propose future improvements within the user interfaces,\ninterpretation of results, and additional vulnerability checks.
The gas mechanism in Ethereum charges the execution of every operation to ensure that smart contracts running in EVM (Ethereum Virtual Machine) will be eventually terminated. Failing to properly set the gas costs of EVM operations allows attackers to launch DoS attacks on Ethereum. Although Ethereum recently adjusted the gas costs of EVM operations to defend against known DoS attacks, it remains unknown whether the new setting is proper and how to configure it to defend against unknown DoS attacks. In this paper, we make the first step to address this challenging issue by first proposing an emulation-based framework to automatically measure the resource consumptions of EVM operations. The results reveal that Ethereum's new setting is still not proper. Moreover, we obtain an insight that there may always exist exploitable under-priced operations if the cost is fixed. Hence, we propose a novel gas cost mechanism, which dynamically adjusts the costs of EVM operations according to the number of executions, to thwart DoS attacks. This method punishes the operations that are executed much more frequently than before and lead to high gas costs. To make our solution flexible and secure and avoid frequent update of Ethereum client, we design a special smart contract that collaborates with the updated EVM for dynamic parameter adjustment. Experimental results demonstrate that our method can effectively thwart both known and unknown DoS attacks with flexible parameter settings. Moreover, our method only introduces negligible additional gas consumption for benign users.
Ponzi schemes are financial frauds which lure users under the promise of high\nprofits. Actually, users are repaid only with the investments of new users\njoining the scheme: consequently, a Ponzi scheme implodes soon after users stop\njoining it. Originated in the offline world 150 years ago, Ponzi schemes have\nsince then migrated to the digital world, approaching first the Web, and more\nrecently hanging over cryptocurrencies like Bitcoin. Smart contract platforms\nlike Ethereum have provided a new opportunity for scammers, who have now the\npossibility of creating "trustworthy" frauds that still make users lose money,\nbut at least are guaranteed to execute "correctly". We present a comprehensive\nsurvey of Ponzi schemes on Ethereum, analysing their behaviour and their impact\nfrom various viewpoints.\n
Jan 1, 2017·AJIS. Australasian journal of information systems/AJIS. Australian journal of information systems/Australian journal of information systems
The fourth industrial revolution, which will alter the globe, is commonly referred to as Blockchain technology. Blockchain technology provides a decentralized, distributed, and central authority-free environment. Since Bitcoin launched Blockchain, research has been continuing on non-financial use cases to extend their applicability. Healthcare is an industry with a significant influence on the Blockchain. Healthcare has penetrated the enthusiasm for the changing nature of Blockchain technology. Blockchain is frequently viewed as the most necessary and optimal healthcare technology to handle sophisticated and complex security and interoperability concerns. More significantly, the “value” and trust-based system’s smart contract mechanism can offer automatic action and reaction. Healthcare, on the other hand, is a complex system. In this paper, we introduce the blockchain and its properties, as well as the significance of the blockchain in healthcare. It also provides blockchain administration, adjudication of claims, interoperability, and application. While in several situations, we observed blockchain technology, the use of blockchain in health care was highly addressed in this paper and the reason why blockchain should be utilized. We introduce the advantages of blockchain as well. Furthermore, we examined the difficulties and prospects for the future and how they may be implemented in more healthcare industries. The paper also discusses the current level of Blockchain application development for healthcare and its limits and topics for further research. This paper aims to demonstrate how Blockchain technologies may be utilized in healthcare and what problems this technology may face in the future and what the Blockchain’s prospects are.
Open access
10 source records
Blockchain Technology Applications and Security
IoT and Edge/Fog Computing
Artificial Intelligence in Healthcare and Education
Blockchain technology enables distributed, encrypted and secure logging of digital transactions. It is the underlying technology of Bitcoin and other cryptocurrencies. Blockchain is expected to revolutionize computing in several areas, particularly where centralization was unnatural and privacy was important. In the paper, we present research on where and how this technology could be useful in the construction industry. The work is based on the study of literature on open issues that exist in construction process management. These are than matched to the capabilities of blockchain. We are motivated by the fact that construction projects involve a dynamic grouping of several companies. We study the degree to which the relationships among them are hierarchical or peer-to-peer and note that particularly in information intensive phases, centralization of information management was necessary because of technology. When using un-constraining technology, communication patterns among participants show a peer-to-peer nature of the relationships. In such environment, blockchain can provide a trustworthy infrastructure for information management during all building life-cycle stages. Even if building information modelling (BIM) is used, which assumes a centralized building information model, there is a role for blockchain to manage information on who did what and when and thus provide a basis for any legal arguments that might occur. On the construction site blockchain can improve the reliability and trustworthiness of construction logbooks, works performed and material quantities recorded. In the facility maintenance phase, blockchain's main potential is the secure storage of sensor data which are sensitive to privacy. We conclude that blockchain provides solutions to many current problems in construction information management. However, it is more likely that it will be built into generic IT infrastructure on top of which construction applications are built, rather than used directly by authors of construction related software. It has a potential to make construction processes less centralized which opens needs for research in that direction.
The dissemination of patients' medical records results in diverse risks to patients' privacy as malicious activities on these records cause severe damage to the reputation, finances, and so on of all parties related directly or indirectly to the data. Current methods to effectively manage and protect medical records have been proved to be insufficient. In this paper, we propose MeDShare, a system that addresses the issue of medical data sharing among medical big data custodians in a trust-less environment. The system is blockchain-based and provides data provenance, auditing, and control for shared medical data in cloud repositories among big data entities. MeDShare monitors entities that access data for malicious use from a data custodian system. In MeDShare, data transitions and sharing from one entity to the other, along with all actions performed on the MeDShare system, are recorded in a tamper-proof manner. The design employs smart contracts and an access control mechanism to effectively track the behavior of the data and revoke access to offending entities on detection of violation of permissions on data. The performance of MeDShare is comparable to current cutting edge solutions to data sharing among cloud service providers. By implementing MeDShare, cloud service providers and other data guardians will be able to achieve data provenance and auditing while sharing medical data with entities such as research and medical institutions with minimal risk to data privacy.
Blockchain technology provides decentralized consensus and potentially enlarges the contracting space through smart contracts. Meanwhile, generating decentralized consensus entails distributing information that necessarily alters the informational environment. We analyze how decentralization relates to consensus quality and how the quintessential features of blockchain remold the landscape of competition. Smart contracts can mitigate informational asymmetry and improve welfare and consumer surplus through enhanced entry and competition, yet distributing information during consensus generation may encourage greater collusion. In general, blockchains sustain market equilibria with a wider range of economic outcomes. We further discuss the implications for antitrust policies targeted at blockchain applications. Received May 31, 2017; editorial decision May 29, 2018 by Editor Itay Goldstein.
This paper discusses the game theory behind self-contained smart contract provably fair casinos, how they can be gamed by attackers with a large amount of money and computing power, as well as what are the necessary conditions to assure the system cannot be taken advantage of under various configurations.
Johnny Dilley, Andrew Poelstra, Jonathan Wilkins, Marta Piekarska · 6 authors
Bitcoin, the first peer-to-peer electronic cash system, opened the door to permissionless, private, and trustless transactions. Attempts to repurpose Bitcoin's underlying blockchain technology have run up against fundamental limitations to privacy, faithful execution, and transaction finality. We introduce \emph{Strong Federations}: publicly verifiable, Byzantine-robust transaction networks that facilitate movement of any asset between disparate markets, without requiring third-party trust. \emph{Strong Federations} enable commercial privacy, with support for transactions where asset types and amounts are opaque, while remaining publicly verifiable. As in Bitcoin, execution fidelity is cryptographically enforced; however, \emph{Strong Federations} significantly lower capital requirements for market participants by reducing transaction latency and improving interoperability. To show how this innovative solution can be applied today, we describe \emph{\liquid}: the first implementation of \emph{Strong Federations} deployed in a Financial Market.
Pablo Lamela Seijas, Simon Thompson, Darryl McAdams
We give an overview of the scripting languages used in existing cryptocurrencies, and in particular we review in some detail the scripting languages of Bitcoin, Nxt and Ethereum, in the context of a high-level overview of Distributed Ledger Technology and cryptocurrencies. We survey different approaches, and give an overview of critiques of existing languages. We also cover technologies that might be used to underpin extensions and innovations in scripting and contracts, including technologies for verification, such as zero knowledge proofs, proof-carrying code and static analysis, as well as approaches to making systems more efficient, e.g. Merkelized Abstract Syntax Trees.
Christopher D. Clack, Vikram A. Bakshi, Lee Braine
Smart Contract Templates support legally-enforceable smart contracts, using operational parameters to connect legal agreements to standardised code. In this paper, we explore the design landscape of potential formats for storage and transmission of smart legal agreements. We identify essential requirements and describe a number of key design options, from which we envisage future development of standardised formats for defining and manipulating smart legal agreements. This provides a preliminary step towards supporting industry adoption of legally-enforceable smart contracts.