The blockchain technology introduced in Satoshi Nakamoto's paper "Bitcoin: A Peer-to-Peer Electronic Cash System" bring a realistic distributed way of transaction to this world. The alternative blockchain Ethereum improved some demerits of Bitcoin. However, the major problem still exists - hash-based proof-of-work requires heavy computing power and hurts the scalability. In this paper, we propose a lightweight blockchain called ZeroCalo. It constructs thousands of miner nodes into DHT (Distributed Hash Table) structure. Efficient message broadcast and key lookup are developed. With them, a consensus-based proof-of-work algorithm for distributed ledger is fulfilled. The evaluation shows that a transaction requires O(logN) of time and O(N) of bandwidth consumption. ZeroCalo consumes very little energy while providing good TPS. This property makes it possible to be deployed on IOT device network or low-end hosts in cloud environment.
Vyacheslav Davydov, Alexander Gazaryan, Yash Madhwal, Yury Yanovich
The paper describes the transfer of exchange investment mechanisms to the cryptocurrency and tokenized assets market. We propose an architecture of a new token standard, which allows dividing different assets into a commodity. The implementation of the prototype on the Ethereum platform is provided. An example of the token application on the banking system is presented.
Smart contracts are appealing because they are self-executing business agreements between parties with the predefined and immutable obligations and rights. However, as with all software, smart contracts may contain vulnerabilities because of design flaws, which may be exploited by one of the parties to defraud the others. In this paper, we demonstrate a systematic approach to building secure design models for smart contracts using formal methods. To build the secure models, we first model the behaviors of participating parties as state machines, and then, we model the predefined obligations and rights of contracts, which specify the interactions among state machines for achieving the business goal. After that, we illustrate executable secure model design patterns in TLA+ (Temporal Logic of Actions) to against well-known smart contract vulnerabilities in terms of state machines and obligations and rights at the design level. These vulnerabilities are found in Ethereum contracts, including Call to the unknown, Gasless send, Reentrancy, Lost in the transfer, and Unpredictable state. The resultant TLA+ specifications are called secure models. We illustrate our approach to detect the vulnerabilities using a real-estate contract example at the design level.
The proliferation of unreliable and biased information is a significant\nproblem on the Internet. To assess the credibility of the information retrieved\nfrom news websites and other sources, users often resort to social platforms\nlooking for confirmation with trustworthy parties. However, users may be faced\nwith considerable obstacles posed by the platform provider, who can prevent\naccess to certain content. This paper presents DClaims, a system that provides\na censorship-resistant distributed service for the exchange of information over\nthe Internet using web annotations. DClaims' fully decentralized architecture\nrelies on Inter-Planetary File System (IPFS) and Ethereum blockchain, both of\nwhich offer desirable censorship resistant properties. DClaims is implemented\nas a web annotations browser extension which allows for the classification of\nnews articles, on news websites. From our evaluation of the system, we conclude\nthat a large scale implementation of the system is practical and economically\nviable.\n
Vero Estrada-Galiñanes, Racin Nygaard, Viktor Trón, Rodrigo Q. Saramago · 6 authors
Blockchain is the driving force behind a myriad of decentralized applications (dapps) that promise to transform the Internet. The next generation Internet, or web3, introduces a "universal state layer" to store data in p2p networks. Swarm, a native layer of the Ethereum web3 stack, aims at providing redundant storage for dapp code, data, as well as, blockchain and state data. Based on a diploma verification dapp use case, we share insights on the role of redundancy strategies in designing a reliable storage layer. Our proof-of-concept improves Swarm's resilience to failures by balancing repairs and storage, with a slightly added latency.
Charlie Hou, Mingxun Zhou, Yan Ji, Phil Daian · 7 authors
Incentive mechanisms are central to the functionality of permissionless blockchains: they incentivize participants to run and secure the underlying consensus protocol. Designing incentive-compatible incentive mechanisms is notoriously challenging, however. As a result, most public blockchains today use incentive mechanisms whose security properties are poorly understood and largely untested. In this work, we propose SquirRL, a framework for using deep reinforcement learning to analyze attacks on blockchain incentive mechanisms. We demonstrate SquirRL's power by first recovering known attacks: (1) the optimal selfish mining attack in Bitcoin [52], and (2) the Nash equilibrium in block withholding attacks [16]. We also use SquirRL to obtain several novel empirical results. First, we discover a counterintuitive flaw in the widely used rushing adversary model when applied to multi-agent Markov games with incomplete information. Second, we demonstrate that the optimal selfish mining strategy identified in [52] is actually not a Nash equilibrium in the multi-agent selfish mining setting. In fact, our results suggest (but do not prove) that when more than two competing agents engage in selfish mining, there is no profitable Nash equilibrium. This is consistent with the lack of observed selfish mining in the wild. Third, we find a novel attack on a simplified version of Ethereum's finalization mechanism, Casper the Friendly Finality Gadget (FFG) that allows a strategic agent to amplify her rewards by up to 30%. Notably, [10] show that honest voting is a Nash equilibrium in Casper FFG: our attack shows that when Casper FFG is composed with selfish mining, this is no longer the case. Altogether, our experiments demonstrate SquirRL's flexibility and promise as a framework for studying attack settings that have thus far eluded theoretical and empirical understanding.
Summary As the value of data has received considerable attention, data trading shows broad market prospects. The existing data trading methods, including private trades and centralized trades, have high risks regarding transaction security and data protection. To solve this problem, we propose a decentralized trading solution for open fair data trading by deploying the smart contract on the blockchain network. The data for sale are encrypted and stored on the distributed storage platform but not directly on the blockchain network. Because the trading content is the decryption key of the data, the proposed new method can alleviate the storage pressure of the blockchain by reducing the transaction cost. We conduct a security analysis which shows that our scheme achieves secure, practical, open, and fair trading. We implement our trading contract with solidity and test it on the Ethereum's test network, and extensive experiments demonstrate desirable feasibility of our proposal.
Asynchronous rumor spreading, or epidemic algorithms, are a class of data dissemination protocols that have been used throughout the years for a large variety of distributed applications. The emergence of large-scale, public blockchains, such as Bitcoin and Ethereum, has reinvigorated research interest in these protocols as they are employed to disseminate pending transactions and confirmed blocks in their peer-to-peer (P2P) networks. Efficient, timely and fault-tolerant information dissemination is vital for blockchain networks as it affects issues ranging from security to block finality. Recent works have analyzed the structural properties of blockchain network overlay graphs. Their findings show that they have inherent similarities to those of social networks, such as power-law degree distributions, small diameters and star-like communities. In this work, we present an experimental analysis of the vanilla asynchronous push & pull rumor spreading protocol that is employed by public blockchains. This protocol, although robust and scalable, can be substantially improved. We demonstrate this by analyzing the effect that multiple parameters have on the protocol's performance, such as using memory to avoid contacting the same neighbor twice in a row, varying the stopping criteria of nodes to decide when to stop spreading the rumor, employing more sophisticated neighbor selection policies instead of the standard uniform random choice and others. Prior works have focused on either providing theoretical upper bounds on the number of rounds needed to spread the rumor to all nodes, or, propose improvements by adjusting isolated parameters. To our knowledge, our work is the first to study how multiple parameters affect the protocol's behavior both in isolation and combination and under a wide range of values. Moreover, prior theoretical works have studied rumor spreading only on bidirectional social topologies. Our study examines the behavior of the protocol in multiple topology classes. These include bidirectional, directed, and also a special type of social topologies, called signed topologies, which resemble more closely the topologies of blockchain P2P networks. Our work is the first to indicate and deal with how chains of communities that are sparsely connected to the core of the network can hamper the rumor's spreading. Thus, we complement prior theoretical work to shed light on how the protocol behaves in practical, real-world, large scale distributed systems. Finally, through our detailed analysis, we demonstrate how a few simple additions to the protocol deliver a percentage decrease of the time required to inform all nodes by a maximum of 99.69% and an average of 86.04%.
The integration of Internet of Things (IoT) and cloud services with edge technologies has enabled the development of many new types of edge services, which leverage blockchain features for cross-organizational, traceable and verifiable records. However, developing such edge services with blockchain features requires not only knowledge about complex blockchain technologies but also how blockchain technologies coexist with edge computing service models and architectures and deployments. In the context of edge service development, coupling edge systems, software models for edge services and blockchain technologies is complex. Thus, a strong collaboration and knowledge sharing for edge systems and blockchain technologies will help addressing many concerns of the developer. However, there is a lack of frameworks for sharing knowledge about blockchain software artefacts and deployments for edge services. In this paper, we present various types of information linking blockchain performance with service deployments at different levels. We represent and associate benchmarked performance information of blockchain operation and blockchain infrastructural services with common edge service interactions and resource deployments. Based on that, we develop a service offering blockchain knowledge to the developer seeking relevant blockchain operation information for their development decisions. We will present a prototype of our framework with benchmarked information obtained from experiments with Ethereum and Hyperledger.
The access efficiency of traceability information has always been one of the main challenges faced by blockchain tracking schemes. At present, the tracking scheme based on blockchain mainly uses the open source Ethereum to realize the record of data flows and the query about transaction information. It causes the consumption of consensus resource high and the transaction query slow, which makes it difficult to meet the need of data tracking. To solve the above problems, this paper proposes a blockchain data provenance scheme based on grouping consensus and B-M tree. Firstly, a grouping consensus mechanism is constructed based on PBFT mechanism to improve the speed of transaction confirmation and complete the fast record of flow information. Then, a B-M transaction tree is designed based on AVL tree and Merkle tree to achieve the efficient query of traceability information under the ensuring that the transaction information can't be tampered. Finally, the correctness, security and simulation results show that the scheme has certain advantages over the traditional blockchain traceability scheme in record and query.
Blockchain was originally developed to support decentralized cryptocurrency applications within a single network. However, the proliferation of blockchain technology has led to the need of supporting transactions across multiple networks requiring interoperability. Thus far, minimal analysis has been dedicated to the interoperability scenario and in particular the prevention of double-spending attacks across interoperable blockchain networks. In this paper, we propose the use of neutral observers to monitor transactions that span multiple blockchains and design a protocol that obviates the double-spending problem across interoperable blockchain networks. We show that the observers, can detect double spending, while remaining honest to the protocol as it is more profitable to them than colluding due to our proposed disincentivization scheme. Leveraging Ethereum's smart-contract functionality, we simulate our proposed disincentivization scheme and show its cost-effectiveness.
Blockchain is decentralized architecture, where data are stored in the form of blocks for processing. The data has to be transferred from one person to another with safety and security and updated with smart contract in the blockchain. But there are some challenges such as data spoofing, integrity, authentication of the data. In the health sector the privacy of the patients' data has to be maintained. The proposed system, “Insurance Management in Healthcare Sector” uses blockchain combined with identity management to access the identity of a person when authorized by the person. After verifying the details, the insured amount will be transferred to the policy holder or the hospital with the help of matching smart contracts in the blockchain of the Ethereum platform. As a result, the insurance claim can reach the policy holder who has initiated the claim process with proof of work. The other use cases such as health care industries, social media networks are also discussed and the analysis of how the blockchain can be used in various fields.
In the current copyright law and technology environment, two prominent problems must be considered when enforcing and executing copyrights: (i) the difficulty of proving authorship/ownership of a copyright; and (ii) the difficulty of conducting copyright transactions. The invention of blockchain technology has made it possible to solve these two issues. First, the use of blockchain technology with the InterPlanetary File System (IPFS) is an excellent mechanism for copyright authentication and document preservation. This mechanism allows authors (copyright owners) to prove authorship of their works and copyrights ownership. However, this mechanism for copyright authentication and document preservation may not be applicable in the future primarily because the computer software currently used may be upgraded in the following years. Second, the combination of Ethereum Blockchain and smart contracts can reduce transaction costs and enhance the efficiency of copyright assignments and licensing transactions. However, many legal problems regarding smart contracts have yet to be addressed. These problems include identifying the contracting parties in the anonymous blockchain network, dealing with scenarios where both contracting parties want to amend the implemented smart contracts, explaining code-based smart contracts and setting up an internal dispute resolution mechanism. Unlike the traditional transmission control protocol/Internet protocol network, where any activity is traceable, users on blockchain technology remain anonymous and their activities on the blockchain are hardly traceable. Although the blockchain itself is unlikely to become a hotbed of copyright infringement, the combination of the Ethereum Blockchain, the IPFS and smart contracts may make the entire process a hotbed of copyright infringement. Therefore, this situation poses considerable worries regarding copyright infringement on the blockchain. When the decentralized and anonymized blockchain and peripheral technologies mature, they will have considerable influence on copyright protection. This problem must be addressed by the copyright legal system in the current wave of blockchain technology implementation.
Growing interest in educational data mining (EDM) and learning analytics (LA) to leverage big data and to benefit education and the science of learning has made data ownership an important focus point for institutions and students. While EDM and LA can provide important information that help enhance the quality of teaching and learning, it has become critical to ensure data privacy and student agency over data. In this paper, we introduce Kratos: an immutable and publicly verifiable data management system that enables EDM and LA, while maintaining data privacy and empowering students with a user interface for data governance and participation in school processes. The system aims to achieve data interoperability, which facilitates EDM and LA as incentives to educational stakeholders (policy makers, educators, developers of education technologies, etc.), while prioritizing student agency over their data. Our system gives students and schools an immutable log along with comprehensive access to data that is otherwise scattered across systems and vendors. The underlying set of rules of the system are defined in a set of smart contracts, codified from existing non-virtual agreements [1] between schools and education technology (edutech) vendors. We propose the smart contracts to be deployed on a public blockchain (like Ethereum or Bitcoin), for notarizing and time-stamping various interactions which users of Kratos may have with data. Third parties requesting access to school data have a unique virtual token assigned to them on the blockchain which helps keep track of data modifications, access and use.
Internet of Things (IoT) gained a great focus in recent years due to its importance in humans' everyday life. IoT applications appear in several domains for human welfare. The need for a powerful and scalable security framework is the main focus for the current research. Blockchain (BC) is a distributed write-only ledger that eliminates the need for third parity to secure and verify transactions between peers. Though BC is considered the most powerful technique for securing transactions between IoT devices, these devices, unfortunately, cannot act as peers in BC because of its limited processing and storage. In this work, Blockchain is utilized in deploying a security framework for IoT monitoring applications. The proposed framework comprises clients (who query IoT devices), device gateways, and an administrator. IoT devices access BC through gateways. These gateways are assumed to be resource-rich and can perform mining tasks. To that end, Ethereum Blockchain is utilized in addition to Ethereum Smart contracts for enforcing a set of rules defined by the system administrator.
Blockchain is a distributed ledger system composed of P2P network proposed as an electronic cash system which can transfer money without a trusted third party. Blockchain has high tamper resistance by the structure which cannot modify a transaction by everyone including the creator of it. However, it also becomes a problem that Blockchain system cannot modify fraudulent transaction already approved. This problem means once an illegal transaction occurs, the damage expands. It is necessary to detect the transaction by the anomaly detection and modify it before approval in order to suppress the damage. However, existing anomaly detection methods of Blockchain need the processing for all the past transactions in Blockchain. The execution time exceeds the approval interval of the major Blockchain system (Ethereum). In this paper, we propose an anomaly detection method using a fixed size user-centric subgraph which is extracted from whole graph made from all the transactions, to prevent the increase of the execution time. Furthermore, to accelerate the anomaly detections, we propose the subgraph structure which is suitable for GPU processing so that all of the subgraph making, the feature extraction, and the anomaly detection are performed in GPU. When the number of transactions is 300 million, our proposed method archives 195 times faster than the existing GPU-based method and the execution time is shorter than the approval interval of the Ethereum. In terms of accuracy, the true positive rate is significantly higher than the existing method in the case of small scale transactions because the local anomaly can be detected by the subgraph with locality. And the rate in the case of large scale and the false positive rate are close to the existing method.
Blockchain technology is more and more popular for its advantage of decentralization, transparency, and nonmodifiable. In an electronic voting system, voting can be fair and secure by blockchain technology without a trusted third party. In this paper, we propose an economical and efficient electronic voting system based on the Ethereum Smart Contract that can also protect voters' privacy. The privacy of voters and votes can be protected by blind signature and homomorphic encryption. More importantly, the encryption algorithm is implemented in the Trusted Execution Environment (TEE), which can effectively reduce the complex operations in the contract and make the cost of Gas as low as possible. In addition, we also evaluated the system's implementation cost and designed a proposal to better protect voters' privacy for board-scale elections.
This paper proposes a decentralized solution for web hosting based on interplanetary file system (IPFS) and Ethereum blockchain. Particularly, we use Ethereum smart contracts to manage the IPFS network and the web hosting service. IPFS platform is used to store data and to host websites. All storage miner nodes on the IPFS network offer the pinning service to ensure that source codes of the websites and users' data are retained long-term. Moreover, these nodes also enable the interplanetary name space (IPNS) service for creating and updating mutable links to IPFS contents. TXT record is also used in the domain name system (DNS) to map domain names to IPNS addresses for hosted websites. For privacy-preserving data storage, websites need to be deployed an encryption algorithm. The proposed model that combines between the IPFS and blockchain networks to form a platform providing the decentralized web hosting service. Experiment illustrates building and hosting a web application on the IPFS network. Experimental results show that, compared to the traditional web hosting model, the hosted web application on the proposed platform ensures the confidentiality, integrity, and availability.
Weirong Sun, Xinhua Zhu, Tong Zhou, Yan Su · 5 authors
In view of the current situation of counterfeit liquor in the liquor industry, this paper develops a liquor anti-counterfeiting traceability system based on Ethereum and RFID in combination with blockchain and Internet of Things technologies. The system uses RFID readers to automatically upload information in the liquor supply chain, and stores the hash value of the information in the blockchain to ensure that the information cannot be tampered and traceable. The smart contract can open different query permissions according to different users. Through this system, the trust of the community in the enterprise can be improved, and at the same time, it is conducive to promoting the modernization process and healthy development of the liquor industry.
Solidity is an object-oriented and high-level language for writing smart contracts that are used to execute, verify and enforce credible transactions on permissionless blockchains. In the last few years, analysis of smart contracts has raised considerable interest and numerous techniques have been proposed to check the presence of vulnerabilities in them. Current techniques lack traceability in source code and have widely differing work flows. There is no single unifying framework for analysis, instrumentation, optimisation and code generation of Solidity contracts at the source code level. In this paper, we present SIF, a comprehensive framework for Solidity contract analysis, query, instrumentation, and code generation. SIF provides support for Solidity contract developers and testers to build source level techniques for analysis, understanding, diagnostics, optimisations and code generation. We show feasibility and applicability of the framework by building practical tools on top of it and running them on 1838 real smart contracts deployed on the Ethereum network.