The permissioned blockchain system has recently become popular in a wide range of scenarios, such as artificial intelligence, financial applications and the Internet of things, due to its dominance in terms of distribution, decentralization, reliability and security. However, the Practical Byzantine Fault-Tolerant (PBFT) algorithm, which is currently adopted in such systems, sparks communication bottlenecks when the number of consensus nodes increases sharply, which seriously hinders large-scale applications. In this paper, we propose a scalable dynamic multi-agent hierarchical PBFT algorithm (SDMA-PBFT), which reduces the communication costs from O(n2) to O( n × k × log k n ). Specifically, SDMA-PBFT forms multiple autonomous systems at each agent node in which message multicasting can be efficiently carried out and the internal voting results can be effectively collected. Therefore, the design of these agent nodes facilitates the in-and-out operations of consensus nodes in the blockchain system. Simulation results show that our proposed algorithm substantially outperforms the PBFT algorithm in terms of latency. Hence, it can be applied to the permissioned blockchain system effectively and efficiently.
Growing consumer awareness as well as manufacturers' internal quality\nrequirements lead to novel demands on supply chain traceability. Existing\ncentralized solutions suffer from isolated data storage and lacking trust when\nmultiple parties are involved. Decentralized blockchain-based approaches\nattempt to overcome these shortcomings by creating digital representations of\nphysical goods to facilitate tracking across multiple entities. However, they\ncurrently do not capture the transformation of goods in manufacturing\nprocesses. Therefore, the relation between ingredients and product is lost,\nlimiting the ability to trace a product's provenance. We propose a\nblockchain-based supply chain traceability system using smart contracts. In\nsuch contracts, manufacturers define the composition of products in the form of\nrecipes. Each ingredient of the recipe is a non-fungible token that corresponds\nto a batch of physical goods. When the recipe is applied, its ingredients are\nconsumed and a new token is produced. This mechanism preserves the traceability\nof product transformations. The system is implemented for the Ethereum Virtual\nMachine and is applicable to any blockchain configuration that supports it. Our\nevaluation reveals that the gas costs scale linearly with the number of\nproducts considered in the system. This leads to the conclusion that the\nsolution can handle complex use cases.\n
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Blockchain Technology Applications and Security
Innovative Microfluidic and Catalytic Techniques Innovation
Oblivious linear-function evaluation (OLE) is a secure two-party protocol allowing a receiver to learn any linear combination of a pair of field elements held by a sender. OLE serves as a common building block for secure computation of arithmetic circuits, analogously to the role of oblivious transfer (OT) for boolean circuits. A useful extension of OLE is vector OLE (VOLE), allowing the receiver to learn any linear combination of two vectors held by the sender. In several applications of OLE, one can replace a large number of instances of OLE by a smaller number of instances of VOLE. This motivates the goal of amortizing the cost of generating long instances of VOLE. We suggest a new approach for fast generation of pseudo-random instances of VOLE via a deterministic local expansion of a pair of short correlated seeds and no interaction. This provides the first example of compressing a non-trivial and cryptographically useful correlation with good concrete efficiency. Our VOLE generators can be used to enhance the efficiency of a host of cryptographic applications. These include secure arithmetic computation and non-interactive zero-knowledge proofs with reusable preprocessing. Our VOLE generators are based on a novel combination of function secret sharing (FSS) for multi-point functions and linear codes in which decoding is intractable. Their security can be based on variants of the learning parity with noise (LPN) assumption over large fields that resist known attacks. We provide several constructions that offer tradeoffs between different efficiency measures and the underlying intractability assumptions.
We introduce FairSwap -- an efficient protocol for fair exchange of digital goods using smart contracts. A fair exchange protocol allows a sender S to sell a digital commodity x for a fixed price p to a receiver R. The protocol is said to be secure if R only pays if he receives the correct x. Our solution guarantees fairness by relying on smart contracts executed over decentralized cryptocurrencies, where the contract takes the role of an external judge that completes the exchange in case of disagreement. While in the past there have been several proposals for building fair exchange protocols over cryptocurrencies, our solution has two distinctive features that makes it particular attractive when users deal with large commodities. These advantages are: (1) minimizing the cost for running the smart contract on the blockchain, and (2) avoiding expensive cryptographic tools such as zero-knowledge proofs. In addition to our new protocols, we provide formal security definitions for smart contract based fair exchange, and prove security of our construction. Finally, we illustrate several applications of our basic protocol and evaluate practicality of our approach via a prototype implementation for fairly selling large files over the cryptocurrency Ethereum.
Blockchain technology and ‘smart contracts’ are widely debated in many industries, but especially among legal professionals and academics. Some practical legal questions can be answered relatively quickly or have to be postponed by ‘we do not know’ or ‘it depends’. More interesting than those considerations, however, is whether the emergence of smart contracts based on blockchain technology as a technological materialisation of connected contracts raises issues for the conceptualisation of transnational contract law and what a new conceptualisation, taking into account these issues, could look like. To this end, this contribution tries to acknowledge or incorporate existing work in the area of technology and law such as ontologies, legal reasoning and simple markup languages, but then goes beyond that and tries to explore a sociolegal concept of smart contracts that incorporates the sociological concept of networks by Latour and the system-theoretical approaches of Luhmann with the descriptions of ‘connected contracts’ by Teubner, ultimately incorporating them into the aforementioned ‘ technological materialisation’ of the network structure of law generally and connected contracts specifically. This then can serve as an important methodological tool for the future, to research and describe ‘smart contracts’ at a higher level of abstraction. INTRODUCTION Certain contractual agents, also called ‘smart contracts’, running on blockchain technology have gained increasing importance due to promising increased automation and assurance for digital contracting, aiming to bridge law and soft ware code. Thus, this contribution investigates these phenomena, recognising that these developments are potentially game-changing for commerce and further digitalisation of contract law. To this end, ‘smart contracts’ and the systems they are running on are analysed with regard to developments of ‘connected contracts’ and a network(ed) understanding of contract law already developed for newer contractual and company law constructs such as just-in-time production. In order not to limit the examination to ‘traditional’ manufacturing networks but to re-investigate the phenomenon of networks in law more generally, this is complemented by taking account of socio-legal descriptions of networks and law, as well as providing a brief account of current or past alternative approaches to bridge law and technology that are relevant for context and understanding.
Blockchain technology shows significant results and huge potential for serving as an interweaving fabric that goes through every industry and market, allowing decentralized and secure value exchange, thus connecting our civilization like never before. The standard approach for asset value predictions is based on market analysis with an LSTM neural network. Blockchain technologies, however, give us access to vast amounts of public data, such as the executed transactions and the account balance distribution. We explore whether analyzing this data with modern Deep Leaning techniques results in higher accuracies than the standard approach. During a series of experiments on the Ethereum blockchain, we achieved $4$ times error reduction with blockchain data than an LSTM approach with trade volume data. By utilizing blockchain account distribution histograms, spatial dataset modeling, and a Convolutional architecture, the error was reduced further by 26\%. The proposed methodologies are implemented in an open source cryptocurrency prediction framework, allowing them to be used in other analysis contexts.
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.
Stefan Dziembowski, Sebastian Faust, Kristina Hostáková
One of the fundamental challenges that hinder further adaption of decentralized cryptocurrencies is scalability. Because current cryptocurrencies require that all transactions are processed and stored on a distributed ledger -- the so-called blockchain -- transaction throughput is inherently limited. An important proposal to significantly improve scalability are off-chain protocols, where the massive amount of transactions is executed without requiring the costly interaction with the blockchain. Examples of off-chain protocols include payment channels and networks, which are currently deployed by popular cryptocurrencies such as Bitcoin and Ethereum. A further extension of payment networks envisioned for cryptocurrencies are so-called state channel networks. In contrast to payment networks that only support off-chain payments between users, state channel networks allow execution of arbitrary complex smart contracts. The main contribution of this work is to give the first full specification for general state channel networks. Moreover, we provide formal security definitions and prove the security of our construction against powerful adversaries. An additional benefit of our construction is the use of channel virtualization, which further reduces latency and costs in complex channel networks.
Christian Badertscher, Peter Gaži, Aggelos Kiayias, Alexander Russell · 5 authors
We present a novel Proof-of-Stake (PoS) protocol, Ouroboros Genesis, that enables parties to safely join (or rejoin) the protocol execution using only the genesis block information. Prior to our work, PoS protocols either required parties to obtain a trusted "checkpoint" block upon joining and, furthermore, to be frequently online or required an accurate estimate of the number of online parties to be hardcoded into the protocol logic. This ability of new parties to "bootstrap from genesis" was a hallmark property of the Bitcoin blockchain and was considered an important advantage of PoW-based blockchains over PoS-based blockchains since it facilitates robust operation in a setting with dynamic availability, i.e., the natural setting---without external trusted objects such as checkpoint blocks---where parties come and go arbitrarily, may join at any moment, or remain offline for prolonged periods of time. We prove the security of Ouroboros Genesis against a fully adaptive adversary controlling less than half of the total stake in a partially synchronous network with unknown message delay and unknown, varying levels of party availability. Our security proof is in the Universally Composable setting assuming the most natural abstraction of a hash function, known as the strict Global Random Oracle (ACM-CCS 2014); this highlights an important advantage of PoS blockchains over their PoW counterparts in terms of composability with respect to the hash function formalisation: rather than a strict GRO, PoW-based protocol security requires a "local" random oracle. Finally, proving the security of our construction against an adaptive adversary requires a novel martingale technique that may be of independent interest in the analysis of blockchain protocols.
The celebrated Nakamoto consensus protocol [16] ushered in several new consensus applications including cryptocurrencies. A few recent works [7, 17] have analyzed important properties of blockchains, including most significantly, consistency, which is a guarantee that all honest parties output the same sequence of blocks throughout the execution of the protocol. To establish consistency, the prior analysis of Pass, Seeman and Shelat [17] required a careful counting of certain combinatorial events that was difficult to apply to variations of Nakamoto. The work of Garay, Kiayas, and Leonardas [7] provides another method of analyzing the blockchain under the simplifying assumption that the network was synchronous. The contribution of this paper is the development of a simple Markov-chain based method for analyzing consistency properties of blockchain protocols. The method includes a formal way of stating strong concentration bounds as well as easy ways to concretely compute the bounds. We use our new method to answer a number of basic questions about consistency of blockchains: Our new analysis provides a tighter guarantee on the consistency property of Nakamoto's protocol, including for parameter regimes which [17] could not consider; We analyze a family of delaying attacks first presented in [17], and extend them to other protocols; We analyze how long a participant should wait before considering a high-value transaction "confirmed"; We analyze the consistency of CliqueChain, a variation of the Chainweb [14] system; We provide the first rigorous consistency analysis of GHOST [20] and also analyze a folklore "balancing"-attack. In each case, we use our framework to experimentally analyze the consensus bounds for various network delay parameters and adversarial computing percentages. We hope our techniques enable authors of future blockchain proposals to provide a more rigorous analysis of their schemes.
Smart contracts can be defined as computer codes which are run digitally by computer programs to utilise the negotiation, formation, and performance of an automated and irreversible agreement between the contracting parties. Smart contracts are distinguished from other forms of contracts in terms of the way they are concluded which is through Blockchain Technology. In contrast to conventional contracts established through speech, written words or actions, smart contracts are algorithmic and self-executing agreements. In this article, smart contracts will be discussed from the perspective of their general rules and features and the Iraqi law. This study analyses the formation mechanisms of the general principles in Iraqi law governing the contracts and how these mechanisms can be applied to the new technological framework of smart contracts. In addition, integrating smart contracts into the current legal provisions in Iraq is examined.
A major limitation of open P2P networks is the lack of strong identities. This allows any agent to attack the system by creating multiple false personas, thereby disrupting the overlay network's connectivity and sabotaging its operation. In this paper, we explore practical ways to defend P2P networks from such attacks. To do so, we employ a game theoretic approach to the management of each peer's list of known nodes and to the overlay construction mechanisms that utilize this list. We consider the interaction between defender and attacker agents as a zero-sum game. We show that the cost of attacks can be driven up substantially if the defender utilizes available information about peers it chooses to connect to, such as their IP address. In addition to theoretical analysis of the underlying game, we apply our approach to the Bitcoin P2P network and derive effective strategies that guarantee a high safety level against attacks.
The device-to-device (D2D) communication is one of the promising technologies of the future Internet of Things (IoT), but its security-related issues remain challenging. The block-chain is considered to be a secure and reliable distributed ledger, so we can treat the device user equipment (D-UE) request for the reusing resources of cellular user equipment (C-UE) as a transaction and put it into a transaction pool, then package the record into the block-chain. In this paper, we study the D2D communication resource allocation scheme based on sparse code multiple access (SCMA). Firstly, the system's interference model and block-chain-based transaction flow are analyzed. Then we propose the optimization problem so that C-UE can get the maximum revenue by sharing its resources to D-UE. This problem is NP-hard, so we propose a heuristic algorithm based on semi-definite relaxation (SDR) programming to solve it. Finally, the performance of the proposed algorithm is verified by simulation of different system parameters.
The Semantic Web, an extension of the current web, provides a common framework that makes data machine understandable and also allows data to be shared and reused across various applications. Resource Description Framework (RDF), a graph-based data model for describing things (entities), facilitates data integration. Due to the explosion of the amount of RDF data, developing tools to support processing and answering of complex queries over the integrated data has become challenging. To overcome this challenge in query processing in semantic data integration frameworks, we provide a view layer inserted between the heterogeneous data sources and user interface layer while ensuring only authorized users are allowed access to the information. The view layer must provide a support in terms of access, integration, querying, management of data sources in a multi-user environment.
The world industry is on a threshold of a new development cycle which is characterized by emergence of breakthrough technologies: distributed ledger technology, drone-type devices, 3D printing, virtual reality, Internet of things, augmented reality etc. Due to these technologies fundamental changes will take place in the majority of economic branches. The automotive industry is not an exception. This industry plays one of the key roles in economy in a great number of countries and changes occurring in it lead not only to creation of new products, technical processes but these changes also entail improvement of the industrial base which has been already created. The Republic of Belarus considers an automotive industry as one of key industries for its economy and its efficiency has a high dependency factor pertaining to speed of innovation emergence and implementation that is strategically important aspect of increase in competitiveness both on current sales markets and on potential ones. The paper pays a special attention to two main trends arising in the course of forming a new industrialization: increase in environmentally-friendly fuel systems and digital transformation. Problems of world ecology have exerted a considerable impact on developments in the field of alternative energy sources. Speed of development and promotion of electric vehicles considerably exceed “breakthrough” innovation developments of the past. However a great number of factors can have a significant effect on the future of electric vehicles and two of them are thoroughly considered in the paper: cost of energy (batteries) and price of oil (at the price of about 20 USD for barrel the development rate will considerably decrease). Besides the matter of environmental friendliness the paper pays attention to services of digital transformation. The world has already presented examples pertaining to usage of remote control for dump trucks, telematics etc. Such an approach makes it possible for organizations to optimize substantially an expenditure budget and doing so we increase resource use efficiency. The paper also contains a review of innovations in the automotive industry of the Republic of Belarus: BelGee electric cars, Belkommunmash electrobuses, developments of large industrial equipment.
This paper presents a solution to the exchange of services within an agent society. We explore an open delivery chain scenario in which autonomous drones offer and sub- contract delivery services to each other. Such agents are able to self-organize according to a chain of responsibility pattern. In such a heterogeneous agent society, it is crucial to define an approach that will guarantee accountability, responsibility, and ultimately trust in the execution of the service. The presented solution is based on smart contracts using a blockchain style of a distributed ledger.
Blockchain technology is an inchoate technology whose current popularity is peaking. Some of the most pervasive blockchain technology use cases exist for supply chains. Sustainable, and especially green, supply chains can benefit from blockchain technology, but there are also caveats. The sustainability and environmental management research and academic literature is only starting to investigate this emergent field. This paper seeks to help advance the discussion and motivate additional practice and research related to green supply chains and blockchain technology. This viewpoint paper provides insight into some of the main dimensions of blockchain technology, an overview of the use cases and issues, and some general research areas for further investigation.
Blockchain technology adds records to a list using cryptographic links. Therefore, the security of blockchain smart contracts is among the most popular contemporary research topics. To improve the theorem-proving technology in this field, we are developing an extensible hybrid verification tool chain, denoted as FSPVM-E, for Ethereum smart contract verification. This hybrid system extends the proof assistants in Coq, a formal proof-management system. Combining symbolic execution with higher-order theorem-proving, it solves consistency, automation, and reusability problems by standard theorem-proving approaches. This article completes the FSPVM-E by developing its proof engine. FSPVM-E is an extensible definitional interpreter based on our previous work FEther, which is totally developed in the Coq proof assistant. It supports almost all semantics of the Solidity programing language, and simultaneously executes multiple types of symbols. FEther also contains a set of automatic strategies that execute and verify the smart contracts in Coq with a high level of automation. The functional correctness of FEther was verified in Coq. In standard tutorials, the execution efficiency of FEther far exceeded that of the interpreters developed in Coq.