Matthias Grundmann, Marc Leinweber, Hannes Hartenstein
We explore challenges of and present a concept for a decentralized payment service which is based on trusted execution environments. The system guarantees that users can always cash out their funds without depending on the cooperation of other network members, hence minimizing the trust required in other network members. We present an overview of the system, motivate key components for a secure architecture and provide a communication protocol. We prove that the payment service users can cash out their funds at any time without any dependence on other network members.
Among different concepts associated with the term blockchain, smart contracts have been a prominent one, especially popularized by the Ethereum platform. In this study, we unpack this concept within the framework of Transaction Cost Economics (TCE). This institutional economics theory emphasizes the role of distinctive (private and public) contract law regimes in shaping firm boundaries. We propose that widespread adoption of the smart contract concept creates a new option in public contracting, which may give rise to a smart-contract-augmented contract law regime. We discuss tradeoffs involved in the attractiveness of the smart contract concept for firms and the resulting potential for change in firm boundaries. Based on our new conceptualization, we discuss potential roles the three branches of government – judicial, executive, and legislative – in enabling and using this new contract law regime. We conclude the paper by pointing out limitations of the TCE perspective and suggesting future research directions.
V. Lakshman Narayana, Arepalli Peda Gopi, Kosaraju Chaitanya
Blockchain is using in every aspect now because of its distributed ledger which is immutable. It provides the information to the users directly without any third party involvement. It mediates the transactions directly between the interacting parties securely. It also eliminates the friction and also the cost of current intermediaries. It is now using in healthcare system to provide the interoperability, security, decentralization and other. EMR is presently using in healthcare which has some issues. The issues in healthcare are patient cannot access the data of his/her own health information. So by this healthcare has issues like interoperability and delay in communication and some other. These issues can be solved by using the Blockchain in healthcare. By this Blockchain provide security by giving the patients to access their own data rather than provider.
Marcela Tuler de Oliveira, Lúcio Henrik A. Reis, Ricardo C. Carrano, Flávio Luiz Seixas · 10 authors
Electronic medical records (EMRs) are highly sensitive information shared among peers to keep up-to-date patient history. Providing security, privacy, and availability to these sensitive data is a challenge because, typically, after data publication the patient loses control over them. In this paper, we propose a blockchain-based approach to secure EMR for healthcare applications, where access control is patient-centric. Our proposal keeps encrypted EMRs in the blockchain, and the patient shares the decryption key only with healthcare professionals in which he/she trusts. Blockchain allows untrusted node, in a distributed peer-to-peer network to correctly and verifiably interact with each other, without any reliable intermediary. We investigate the scalability of our approach through simulations. Results show that it scales well since increasing the number of nodes in the network implies a linear increase in the size of the stored chain. Results also reveal that the time for inserting a new EMR in the blockchain remains low even when the number of nodes in the network increases.
Following Bitcoin's Nakamoto Consensus protocol (NC), hundreds of cryptocurrencies utilize proofs of work (PoW) to maintain their ledgers. However, research shows that NC fails to achieve perfect chain quality, allowing malicious miners to alter the public ledger in order to launch several attacks, i.e., selfish mining, double-spending and feather-forking. Some later designs, represented by Ethereum, Bitcoin-NG, DECOR+, Byzcoin and Publish or Perish, aim to solve the problem by raising the chain quality; other designs, represented by Fruitchains, DECOR+ and Subchains, claim to successfully defend against the attacks in the absence of perfect chain quality. As their effectiveness remains self-claimed, the community is divided on whether a secure PoW protocol is possible. In order to resolve this ambiguity and to lay down the foundation of a common body of knowledge, this paper introduces a multi-metric evaluation framework to quantitatively analyze PoW protocols' chain quality and attack resistance. Subsequently we use this framework to evaluate the security of these improved designs through Markov decision processes. We conclude that to date, no PoW protocol achieves ideal chain quality or is resistant against all three attacks. We attribute existing PoW protocols' imperfect chain quality to their unrealistic security assumptions, and their unsatisfactory attack resistance to a dilemma between "rewarding the bad" and "punishing the good". Moreover, our analysis reveals various new protocol-specific attack strategies. Based on our analysis, we propose future directions toward more secure PoW protocols and indicate several common pitfalls in PoW security analyses.
Beltrán Borja Fiz Pontiveros, Mathis Steichen, Radu State
In this work, we consider the graph of confirmed transactions in bitcoin. Understanding this graph is essential to discern the different economic activities conducted by the pseudonymous actors. In addition to traditional graph analysis methods, new metrics need to be engineered specifically for the bitcoin transaction graph. Hence, we propose a new centrality measure named mint centrality. The measure uses the inherent tree structure of transactions in bitcoin and their relation to the corresponding set of coinbase transactions, and can be evaluated with linear complexity. We present preliminary results of the mint centrality on the first 200,000 blocks of the public bitcoin blockchain.
With the rapid development of the internet of things (IoT), traditional industries are setting off a massive wave of digitization. In the era of the Internet of Everything, millions of devices and links in IoT pose more significant challenges to data management. Most existing solutions employ centralized systems to control IoT devices, which brings about the privacy and security issues in IoT data management. Recently, blockchain has attracted much attention in the field of IoT due to its decentralization, traceability, and non-tamperability. However, it is non-trivial to apply the current blockchain techniques to IoT due to the lack of scalability and high resource costs. Different blockchain platforms have their particular advantages in the scenario of IoT data management. In this paper, we propose a cross-chain framework to integrate multiple blockchains for efficient and secure IoT data management. Our solution builds an interactive decentralized access model which employs a consortium blockchain as the control station. Other blockchain platforms customized for specific IoT scenarios run as the backbone of all IoT devices. It is equivalent to opening the off-chain channels on the consortium blockchain. Our model merges transactions in these channels for confirmation based on the notary mechanism. Finally, we implement a prototype of the proposed model based on hyperledge Fabric and IOTA Tangle. We evaluate the performance of our method through extensive experiments. The results demonstrate the effectiveness and efficiency of our framework.
Blockchain technology has a potential to address many of the food safety challenges facing the world today. Some of the most promising blockchain applications developed to data have been in the food supply chains.
Abstract If fiscal decentralization promotes growth, why do some regions decentralize more than others? This article identifies the growing divergence of fiscal centralization among Chinese cities and explains it in a public finance framework. It argues that fiscal decentralization and its economy‐liberalizing effect entail significant short‐term fiscal risk. The more a locality relies on uncompetitive business ownership for fiscal revenue, the less likely fiscal decentralization is to occur. This article compiles a dataset of 20 provincial capitals between 1999 and 2016 to test for the connection between a city's tax base and its fiscal centralization level. It then pairs two “most similar” cities to trace how fiscal security concerns drove their fiscal and economic policies apart. This article adds a micro‐level perspective to the literature on fiscal federalism. By pointing out the fiscal constraints confronting local governments, it offers a new angle to understand the different growth paths of Chinese cities.
Robert Norvill, Beltran Fiz, Radu State, Andréa Cullen
Ethereum smart contracts have become common enough to warrant the need for standards to ensure ease of use. The most well known standard was created for the emerging token ecosystem and the exchanges serving it: the ERC20 standard. In this work we use the function selectors present in Ethereum smart contract bytecode to define contract purpose. Contracts are clustered according to the selectors they have. A Reverse look-up from selectors to function names is used to label clusters. We use the function names in clusters to suggest candidates for ERC standardisation.
Many chatbots have been developed that provide a multitude of services through a wide range of methods. A chatbot is a brand-new conversational agent in the highspeed changing technology world. With the advance of Artificial Intelligence and machine learning, chatbots are becoming more and more popular. A chatbot is the extension of human interface mediums such as the phone and social platforms. Similarly, Cryptocurrency is a new extension of digital or virtual currency designed to work as a medium of exchange. In the current digital exchanging world, investors and interested parties are eager to know more information about, and the capabilites of, this new type of currency. One of the potential paths to retrieve the info automatically and quickly is through a chatbot. We explored the open source python library, Chatterbot, to apply Itchat API (a WeChat interface) with the aim of building a robot chatting application, I&C Chat, on the topic of cryptocurrency. First, we collected question and answer pairs datasets from Quora websites. Furthermore, we also created API calls to query the real time quote for the top 25 cryptocurrencies. Then we used the collected data to train our chatbot and implemented a logic adapter to receive the price quote of cryptocurrencies based on the incoming question. The Itchat API method will return the best matched answer to the asking party automatically. The response time of different questions has been investigated. The results imply that this application is quite useful, feasible and beneficial to the digital currency world.
Michał Król, Alberto Sonnino, Mustafa Al-Bassam, Argyrios G. Tasiopoulos · 6 authors
As cryptographic tokens and altcoins are increasingly being built to serve as utility tokens, the notion of useful work consensus protocols is becoming ever more important. With useful work consensus protocols, users get rewards after they have carried out some specific tasks useful for the network. While in some cases the proof of some utility or service can be provided, the majority of tasks are impossible to verify reliably. To deal with such cases, we design “Proof-of-Prestige” (PoP)—a reward system that can run directly on Proof-of-Stake (PoS) blockchains or as a smart contract on top of Proof-of-Work (PoW) blockchains. PoP introduces “prestige,” which is a volatile resource that, in contrast to coins, regenerates over time. Prestige can be gained by performing useful work, spent when benefiting from services, and directly translates to users minting power. Our scheme allows us to reliably reward decentralized workers while keeping the system free for the end-users. PoP is resistant against Sybil and collusion attacks and can be used with a vast range of unverifiable tasks. We build a simulator to assess the cryptoeconomic behavior of the system and deploy a full prototype of a content dissemination platform rewarding its participants. We implement the blockchain component on both Ethereum (PoW) and Cosmos (PoS), provide a mobile application, and connect it with our scheme with a negligible memory footprint. Finally, we adapt a fair exchange protocol allowing us to atomically exchange files for rewards also in scenarios where not all the parties have Internet connectivity. Our evaluation shows that even for large Ethereum traces, PoP introduces sub-millisecond computational overhead for miners in Cosmos and less than 0.013$ smart contract invocation cost for users in Ethereum.
Sina Rafati Niya, Eryk Schiller, Ile Cepilov, Fabio Maddaloni · 8 authors
Proof-of-Work (PoW) in Blockchains (BC), which is a widely used consensus algorithm, suffers from high power consumption of miners and low transaction rates. This work demonstrates a Proof-of-Stake (PoS)-based BC called Bazo, which is specially designed and adapted for Internet of Things (IoT) data streams. Bazo displays enhanced performance in terms of energy consumption and transactions processing in comparison to PoW-based BC. To further improve performance of Bazo, sharding and transaction aggregation methods are employed. Moreover, IoT-BC adaptation helpers of a modular and layered architecture are provided to allow wireless devices to submit data into the BC. The designed architecture can support multiple hardware and software platforms as well as network technologies.
Thomas Kerber, Aggelos Kiayias, Markulf Kohlweiss, Vassilis Zikas
We present Ouroboros Crypsinous, the first formally analyzed privacy-preserving proof-of-stake blockchain protocol. To model its security we give a thorough treatment of private ledgers in the (G)UC setting that might be of independent interest. To prove our protocol secure against adaptive attacks, we introduce a new coin evolution technique relying on SNARKs and key-private forward secure encryption. The latter primitive-and the associated construction-can be of independent interest. We stress that existing approaches to private blockchain, such as the proof-of-work-based Zerocash are analyzed only against static corruptions.
Sidechains have long been heralded as the key enabler of blockchain scalability and interoperability. However, no modeling of the concept or a provably secure construction has so far been attempted. We provide the first formal definition of what a sidechain system is and how assets can be moved between sidechains securely. We put forth a security definition that augments the known transaction ledger properties of liveness and safety to hold across multiple ledgers and enhance them with a new “firewall” security property which safeguards each blockchain from its sidechains, limiting the impact of an otherwise catastrophic sidechain failure. We then provide a sidechain construction that is suitable for proof-of-stake (PoS) sidechain systems. As an exemplary concrete instantiation we present our construction for an epoch- based PoS system consistent with Ouroboros (Crypto 2017), the PoS blockchain protocol used in Cardano which is one of the largest pure PoS systems by market capitalisation, and we also comment how the construction can be adapted for other protocols such as Ouroboros Praos (Eurocrypt 2018), Ouroboros Genesis (CCS 2018), Snow White and Algorand. An important feature of our construction is merged-staking that prevents “goldfinger” attacks against a sidechain that is only carrying a small amount of stake. An important technique for pegging chains that we use in our construction is cross-chain certification which is facilitated by a novel cryptographic primitive we introduce called ad-hoc threshold multisignatures (ATMS) which may be of independent interest. We show how ATMS can be securely instantiated by regular and aggregate digital signatures as well as succinct arguments of knowledge such as STARKs and bulletproofs with varying degrees of storage efficiency.
This paper describes Slither, a static analysis framework designed to provide rich information about Ethereum smart contracts. It works by converting Solidity smart contracts into an intermediate representation called SlithIR. SlithIR uses Static Single Assignment (SSA) form and a reduced instruction set to ease implementation of analyses while preserving semantic information that would be lost in transforming Solidity to bytecode. Slither allows for the application of commonly used program analysis techniques like dataflow and taint tracking. Our framework has four main use cases: (1) automated detection of vulnerabilities, (2) automated detection of code optimization opportunities, (3) improvement of the user's understanding of the contracts, and (4) assistance with code review. In this paper, we present an overview of Slither, detail the design of its intermediate representation, and evaluate its capabilities on real-world contracts. We show that Slither's bug detection is fast, accurate, and outperforms other static analysis tools at finding issues in Ethereum smart contracts in terms of speed, robustness, and balance of detection and false positives. We compared tools using a large dataset of smart contracts and manually reviewed results for 1000 of the most used contracts.
Juan Plazuelo Pascual, Carlos Tardon Rubio, Juan Toro Cebada, Angel Hernando Veciana
This document analyzes price discovery in cryptocurrency markets by comparing centralized and decentralized exchanges, as well as spot and futures markets. The study focuses first on Ethereum (ETH) and then applies a similar approach to Bitcoin (BTC). Chapter 1 outlines the theoretical framework, emphasizing the structural differences between centralized exchanges and decentralized finance mechanisms, especially Automated Market Makers (AMMs). It also explains how to construct an order book from a liquidity pool in a decentralized setting for comparison with centralized exchanges. Chapter 2 describes the methodological tools used: Hasbrouck's Information Share, Gonzalo and Granger's Permanent-Transitory decomposition, and the Hayashi-Yoshida estimator. These are applied to explore lead-lag dynamics, cointegration, and price discovery across market types. Chapter 3 presents the empirical analysis. For ETH, it compares price dynamics on Binance and Uniswap v2 over a one-year period, focusing on five key events in 2024. For BTC, it analyzes the relationship between spot and futures prices on the CME. The study estimates lead-lag effects and cointegration in both cases. Results show that centralized markets typically lead in ETH price discovery. In futures markets, while they tend to lead overall, high-volatility periods produce mixed outcomes. The findings have key implications for traders and institutions regarding liquidity, arbitrage, and market efficiency. Various metrics are used to benchmark the performance of modified AMMs and to understand the interaction between decentralized and centralized structures.
Building trustless cross-blockchain trading protocols is challenging. Centralized exchanges thus remain the preferred route to execute transfers across blockchains. However, these services require trust and therefore undermine the very nature of the blockchains on which they operate. To overcome this, several decentralized exchanges have recently emerged which offer support for atomic cross-chain swaps (ACCS). ACCS enable the trustless exchange of cryptocurrencies across blockchains, and are the only known mechanism to do so. However, ACCS suffer significant limitations; they are slow, inefficient and costly, meaning that they are rarely used in practice. We present XCLAIM: the first generic framework for achieving trustless and efficient cross-chain exchanges using cryptocurrency-backed assets (CbAs). XCLAIM offers protocols for issuing, transferring, swapping and redeeming CbAs securely in a non-interactive manner on existing blockchains. We instantiate XCLAIM between Bitcoin and Ethereum and evaluate our implementation; it costs less than USD 0.50 to issue an arbitrary amount of Bitcoin-backed tokens on Ethereum. We show XCLAIM is not only faster, but also significantly cheaper than atomic cross-chain swaps. Finally, XCLAIM is compatible with the majority of existing blockchains without modification, and enables several novel cryptocurrency applications, such as cross-chain payment channels and efficient multi-party swaps.
Ningyu He, Lei Wu, Haoyu Wang, Yao Guo · 5 authors
In this paper, we present the first large-scale and systematic study to characterize the code reuse practice in the Ethereum smart contract ecosystem. We first performed a detailed similarity comparison study on a dataset of 10 million contracts we had harvested, and then we further conducted a qualitative analysis to characterize the diversity of the ecosystem, understand the correlation between code reuse and vulnerabilities, and detect the plagiarist DApps. Our analysis revealed that over 96% of the contracts had duplicates, while a large number of them were similar, which suggests that the ecosystem is highly homogeneous. Our results also suggested that roughly 9.7% of the similar contract pairs have exactly the same vulnerabilities, which we assume were introduced by code clones. In addition, we identified 41 DApps clusters, involving 73 plagiarized DApps which had caused huge financial loss to the original creators, accounting for 1/3 of the original market volume.
In Ethereum blockchain, the user needs to set a Gas price to get a transaction processed and approved by Miners. To have the transaction executed, the Gas price has to be greater than or equal to the lowest Ethereum transaction fees. This paper presents a set of data sampled every 15 seconds, from December 1st, 2018 to December 15, 2018, coming from different blockchain web APIs. The aim of the paper is to investigate whether and to what extent different variables-such as the number of pending transactions, the value of the USD/Ether pair, average electricity prices around the world, and the number of miners-influence the Ethereum transaction fees. This study is relevant from an economic perspective because more and more companies in different economic fields are adopting Ethereum blockchain. From historical data analysis, we found that only some of these variables do have an influence. For example, the number of pending transactions and the number of miners have a major influence on Ethereum transaction fees when compared to the other variables.
Several IoT applications are tightly dependent on the locations of the devices. However, localization algorithms can be easily compromised by injecting false locations. In this paper, we propose a Blockchain-based secure localization algorithm for the Internet of Things (IoT). The algorithm uses a public ledger (Blockchain) that contains nodes position and the list of their neighbor nodes. This ledger is shared among the IoT devices. Once an IoT device is localized its new position and the list of neighbor nodes are added to the Blockchain. This shared localization data will be used later by other IoT devices for their localization process. To avoid the attack where a malicious node sends a fake position, the correctness of the claimed position are verified before adding it to the Blockchain. Moreover, data exchanged between nodes (IoT devices) are signed to guarantee their authenticity and integrity. The integration of these security mechanisms into the localization process permits to exclude false data and therefore reduces the localization error. The simulation results show that adding the proposed security mechanism improves the localization accuracy of the algorithm when running in the presence of malicious nodes.
Oscar Delgado-Mohatar, Julián Fiérrez, Rubén Tolosana, Rubén Vera-Rodríguez
We explore practical tradeoffs in blockchain-based biometric template storage. We first discuss opportunities and challenges in the integration of blockchain and biometrics, with emphasis in biometric template storage and protection, a key problem in biometrics still largely unsolved. Blockchain technologies provide excellent architectures and practical tools for securing and managing the sensitive and private data stored in biometric templates, but at a cost. We explore experimentally the key tradeoffs involved in that integration, namely: latency, processing time, economic cost, and biometric performance. We experimentally study those factors by implementing a smart contract on Ethereum for biometric template storage, whose cost-performance is evaluated by varying the complexity of state-of-the-art schemes for face and handwritten signature biometrics. We report our experiments using popular benchmarks in biometrics research, including deep learning approaches and databases captured in the wild. As a result, we experimentally show that straightforward schemes for data storage in blockchain (i.e., direct and hash-based) may be prohibitive for biometric template storage using state-of-the-art biometric methods. A good cost-performance tradeoff is shown by using a blockchain approach based on Merkle trees.
WebGL is a browser feature that enables JavaScript-based control of the graphics processing unit (GPU) to render interactive 3D and 2D graphics, without the use of plug-ins. Exploiting WebGL for attacks will affect billions of users since browsers serve as the main interaction mechanism with the world wide web. This paper explores the potential threats derived from the recent move by browsers from WebGL 1.0 to the more powerful WebGL 2.0. We focus on two possible abuses of this feature: distributed password cracking and distributed cryptocurrency mining. Our evaluation of the attacks also includes the practical aspects of successful attacks, such as stealthiness and user-experience. Considering the danger of WebGL abuse, as observed in the experiments, we designed and evaluated a proactive defense. We implemented a Chrome extension that proved itself effective in detecting and blocking WebGL. We demonstrate in our experiments the major improvements of WebGL 2.0 over WebGL 1.0 both in performance and in convenience. Furthermore, our results show that it is possible to use WebGL 2.0 in distributed attacks under real-world conditions. Although WebGL 2.0 shows similar hash rates as CPU-based techniques, WebGL 2.0 proved to be significantly harder to detect and has a lesser effect on user experience.
Bitcoin is a popular cryptocurrency that records all transactions in an allotted append-handiest public ledger referred to as a blockchain. The security of Bitcoin heavily relies on the motivation-suitable proof-of-work (PoW) founded dispensed consensus protocol, which is run with the aid of the community nodes known as miners. Because of its inception, blockchain technological know-how has proven promising application possibilities. The spectrum of blockchain functions stages from financial, healthcare, automobile, hazard administration, internet of matters (IoT) to public and social offerings. Several reports focal point on utilizing the blockchain information structure in various applications. These vulnerabilities result in the execution of different security threats to the ordinary functionality of Bitcoin. We then examine the feasibility and robustness of the brand new safety solutions. Moreover, we discuss the current anonymity concerns in Bitcoin and the privatenessrelated threats to Bitcoin customers together with the evaluation of the comprehensive privacy-keeping solutions.