Blockchain Papers

Quoc-Bao Nguyen, Anh-Quynh Nguyen, Van Hoa Nguyen, Thanh Nguyen-Le · 5 authors

No abstract is available for this record.

S.J. Wels

A major bottleneck of the state-of-the-art distributed ledgers is the limited transaction throughput. Existing ledgers lack scalability and are unable to process transactions at the speed of centralised systems. One technique used by Ethereum 2.0 to overcome these performance and scalability limitations is sharding. With sharding, the computational work is partitioned among multiple, smaller groups of validators referred to as shards. These shards operate in parallel to increase the overall transaction throughput while minimising the communication, computation and storage requirements per node. However, the interoperability between shards is yet very limited. It can take several minutes before a shard is allowed to process a cross-shard transaction while there is no guarantee that a cross-shard transaction will be processed at all. Without interoperability improvements, sharding will only benefit smart contract applications that run within a single shard. In this study we propose Guaranteed-TX, a guaranteed cross-shard transaction execution protocol for Ethereum 2.0. Guaranteed-TX allows shards to process cross-shard transactions before being finalised in the block it was created - a property called optimistic execution - which significantly improves cross-shard transaction latencies. In addition, it provides economic guarantees that all cross-shard transaction will eventually be processed. In order to achieve both Guaranteed-TX introduces a messaging layer which records the created and processed cross-shard transactions and is shared with every shard. The messaging layer is used to finalise consistent blocks and punish validators in a shard committee for not processing cross-shard transactions. Consequently, cross-shard transactions are either processed or slowly drain the stake of the validators within the addressed shard. Although we prove correctness of Guaranteed-TX and show that it achieves theoretical satisfying performance, the protocol is build upon assumptions which yet have to been proven. The first phase of the Ethereum 2.0 transition is set for launch on January 3, 2020. However, it may take several years before cross-shard communication will be facilitated. In the meantime, many specifications may change and empirical evidence may confirm or invalidate our assumptions. Our findings show that a guaranteed cross-shard transaction protocol is feasible and the insights of this study should be used for further protocol developments.

Anastasia Mavridou, Áron Lászka, Emmanouela Stachtiari, Abhishek Dubey

The adoption of blockchain based distributed ledgers is growing fast due to their ability to provide reliability, integrity, and auditability without trusted entities. One of the key capabilities of these emerging platforms is the ability to create self-enforcing smart contracts. However, the development of smart contracts has proven to be error-prone in practice, and as a result, contracts deployed on public platforms are often riddled with security vulnerabilities. This issue is exacerbated by the design of these platforms, which forbids updating contract code and rolling back malicious transactions. In light of this, it is crucial to ensure that a smart contract is secure before deploying it and trusting it with significant amounts of cryptocurrency. To this end, we introduce the VeriSolid framework for the formal verification of contracts that are specified using a transition-system based model with rigorous operational semantics. Our model-based approach allows developers to reason about and verify contract behavior at a high level of abstraction. VeriSolid allows the generation of Solidity code from the verified models, which enables the correct-by-design development of smart contracts.

Alex Norta, Patrick Dai, Neil Mahi, Jordan Earls

No abstract is available for this record.

Akash Madhusudan, Iraklis Symeonidis, Mustafa Mustafa, Ren Zhang · 5 authors

This paper presents an efficient solution for the booking and payments functionality of a car sharing system that allows individuals to share their personal, underused cars in a completely decentralized manner, annulling the need of an intermediary. Our solution, named SC2Share, leverages smart contracts and uses them to carry out secure and private car booking and payments. Our experiments on SC2Share on the Ethereum testnet guarantee high security and privacy to its users and confirm that our system is cost-efficient and ready for practical use.

Shangping Wang, Xixi Tang, Yaling Zhang, Juanjuan Chen

With the rapid development of electronic information technology, online transaction will gradually surpass traditional market transaction, among which online payment and asset delivery become the focus of attention. But in fact, due to the incomplete third-party payment mechanism and the intrusion risk of various charging Trojan, it is easy to cause a trust crisis. The existing centralized framework often leads to information asymmetry between the two parties. Therefore, how to realize the fairness of payment and the auditability of assets in the distributed system is a challenging problem. The emerging blockchain technology provides a new method with its openness, transparency and verifiability. Existing researches do not provide a complete shopping model for consumers, most of which focuses on payments or only on asset delivery. In this paper, we propose an auditable fair payment and physical asset delivery protocol based on smart contracts. Three types of smart contracts are designed to achieve reliable and fair payment among merchants, consumers and logistics companies. The traceability and auditability of blockchain provide an effective method to audit assets and data sharing in the whole transportation. In view of the phenomenon of goods being switched, the way of ”pre-verification” is added. In order to prevent the illegal elements to fake pickup code, induce consumers to conduct illegal operations, cause property loss, in our system the pickup codes are generated by consumers to reduce the risk of fraud. In addition, our plan designs a complete return process for the first time, providing better service experience and higher efficiency for consumers. Finally, all the contracts involved in the scheme are implemented and deployed on the ethereum test network. The results of security analysis and evaluation showed that our scheme was improved in cost, with high security and availability.

Klaus Grobys

A total of 1.1 million bitcoins were stolen in the 2013–2017 period. Noting that the average price for a Bitcoin in 2018 was $7572 the corresponding monetary equivalent of losses is $8.9 billion highlighting the societal impact of this criminal activity. Investigating the response of the uncertainty of Bitcoin returns when hacking incidents occur, the results of this study point toward two different responses. After experiencing a contemporaneous effect at day t=0, the volatility increases significantly again at day t+5. Hacking incidents that occur in the Bitcoin market also affect the uncertainty in the Ethereum market with a time delay of five days. Notably, neither Bitcoin nor Ethereum appear to exhibit asymmetric responses to negative innovations.

Sarah Azouvi, Mary Maller, Sarah Meiklejohn

No abstract is available for this record.

Michael Fröwis, Rainer Böhme

Efficient transfers to many recipients present a host of issues on Ethereum. First, accounts are identified by long and incompressible constants. Second, these constants have to be stored and communicated for each payment. Third, the standard interface for token transfers does not support lists of recipients, adding repeated communication to the overhead. Since Ethereum charges resource usage, even small optimizations translate to cost savings. Airdrops, a popular marketing tool used to boost coin uptake, present a relevant example for the value of optimizing bulk transfers. Therefore, we review technical solutions for airdrops of Ethereum-based tokens, discuss features and prerequisites, and compare the operational costs by simulating 35 scenarios. We find that cost savings of factor two are possible, but require specific provisions in the smart contract implementing the token system. Pull-based approaches, which use on-chain interaction with the recipients, promise moderate savings for the distributor while imposing a disproportional cost on each recipient. Total costs are broadly linear in the number of recipients independent of the technical approach. We publish the code of the simulation framework for reproducibility, to support future airdrop decisions, and to benchmark innovative bulk payment solutions.

Artem Shurov, Daniil Malevanniy, Oleg Iakushkin, Vladimir Korkhov

No abstract is available for this record.

Francesco Buccafurri, Gianluca Lax, Lorenzo Musarella, Antonia Russo

No abstract is available for this record.

Saketh Aleti, Bruce Mizrach

Abstract We study Bitcoin (BTC) trading at the Chicago Mercantile Exchange (CME) and four settlement spot exchanges that transact $146 million per day in the BTC/USD pair. Spot market median trade sizes are under $1,300 but exceed $18,000 on the CME. Bid‐ask spreads average 0.0298%. Trade sizes of over $1 million move markets by less than 1%. 2.5% of trades and 15.5% of cancellations on Coinbase take place within 50 ms. Bid‐ask spreads exceed 0.8% for only 226 s. Most executions trade‐through better quotes, with estimated losses of $36 million. The CME leads price discovery. BTC leads Ethereum price adjustment.

Shangping Wang, Xu Wang, Yaling Zhang

Now more and more data are being outsourced to cloud services. In order to ensure data security and privacy, data are usually stored on the cloud server in the form of ciphertext. When a user requests access to the encrypted data, an access key distributed by a third party is needed. However, if the third party is dishonest, the security of the system will be threatened. Faced with this problem, in this paper, we propose a new secure cloud storage framework with access control by using the Ethereum blockchain technology. Our new scheme is a combination of Ethereum blockchain and ciphertext-policy attribute-based encryption (CP-ABE). The proposed cloud storage framework is decentralized, that is, there is no trusted third party in the system. Our scheme has three main features. First, as the Ethereum blockchain technology is used, the data owner can store ciphertext of data through smart contracts in a blockchain network. Second, the data owner can set valid access periods for data usage so that the ciphertext can only be decrypted during valid access periods. Finally, as the creation and invocation of each smart contract can be stored in the blockchain, thus, the function of the trace is achieved. The analysis of the security and experiment shows that our scheme is feasible.

Yong Wang, Aiqing Zhang, Peiyun Zhang, Huaqun Wang

The sharing of electronic health records (EHRs) has great positive significance for research of disease and doctors' diagnosis. In recent years, cloud-based electronic medical record sharing scheme has brought a lot of conveniences, but the centralization of cloud exposes threats inevitably to data security and privacy preservation. Blockchain technology can be seen as a promising solution to address these problems on account of its unique propertis of decentration, anonymity, unforgeability and verifiability. In this paper, we propose a blockchain based secure and privacy-preserving EHR sharing protocol. Data requester can search desired keyword from data provider to find relevant EHRs on the EHR consortium blockchain and get the re-encryption ciphertext from cloud server after getting the data owner's authorization. The scheme mainly uses searchable encryption and conditional proxy re-encryption to realize data security, privacy preservation, and access control. Furthermore, proof of authorization is designed as the consensus mechanism for consortium blockchain to guarantee system's availability. Security analysis demonstrates that the proposed protocol can achieve security goals. Besides, we emulate the cryptographic primitives and implement the proposed scheme on Ethereum platform. Performance evaluation shows that the proposed scheme has high computational efficiency.

Ayushi Sharma, Shashwat Tiwari, Nitin Arora, S. C. Sharma

Blockchain is an emerging technology that can radically improve transactions security at banking, supply chain, and other transaction networks. It's estimated that Blockchain will generate $3.1 trillion in new business value by 2030. Essentially, it provides the basis for a dynamic distributed ledger that can be applied to save time when recording transactions between parties, remove costs associated with intermediaries, and reduce risks of fraud and tampering. This book explores the fundamentals and applications of Blockchain technology. Readers will learn about the decentralized peer-to-peer network, distributed ledger, and the trust model that defines Blockchain technology. They will also be introduced to the basic components of Blockchain (transaction, block, block header, and the chain), its operations (hashing, verification, validation, and consensus model), underlying algorithms, and essentials of trust (hard fork and soft fork). Private and public Blockchain networks similar to Bitcoin and Ethereum will be introduced, as will concepts of Smart Contracts, Proof of Work and Proof of Stack, and cryptocurrency including Facebook's Libra will be elucidated. Also, the book will address the relationship between Blockchain technology, Internet of Things (IoT), Artificial Intelligence (AI), Cybersecurity, Digital Transformation and Quantum Computing. Readers will understand the inner workings and applications of this disruptive technology and its potential impact on all aspects of the business world and society. A look at the future trends of Blockchain Technology will be presented in the book.

Madhusudan Singh, Shiho Kim

No abstract is available for this record.

И.И. Баринов, Vadim Arasev, Andreas Fackler, Vladimir Komendantskiy · 7 authors

In this paper we introduce POSDAO, a Proof of Stake (POS) algorithm implemented as a decentralized autonomous organization (DAO). It is designed to provide a decentralized, fair, and energy efficient consensus for public chains. The algorithm works as a set of smart contracts written in Solidity. POSDAO is implemented with a general purpose BFT consensus protocol such as Authority Round (AuRa) with a proposer node and probabilistic finality, or Honey Badger BFT (HBBFT), leaderless and with instant finality. Validators are incentivized to behave in the best interests of a network through a configurable reward structure. The algorithm provides a Sybil control mechanism for managing a set of validators, distributing rewards, and reporting and penalizing malicious validators. The authors provide a reference POSDAO implementation, xDai POSDAO, which uses xDai as a stable transactional coin and a representative ERC677 token (STAKE) as a staking token. The reference implementation functions on an Ethereum 1.0 sidechain and utilizes the AuRa consensus protocol. Assets are bridged between the Ethereum mainnet and the xDai POSDAO network using several instances of the POA TokenBridge.

Hongru Yu, Haiyang Sun, Danyi Wu, Tsung-Ting Kuo

Blockchain and smart contracts (i.e., computer code that can be run on blockchain) are increasingly popular for healthcare applications. However, only very few implementations exist because of the complexity of the technologies. Although there are tutorials and reviews to introduce blockchain and smart contracts, a pragmatic comparison of such platforms is needed. In this study, we addressed practical considerations while building a healthcare blockchain and smart contract system, by (1) comparing technical features of platforms, (2) selecting three platforms, (3) constructing blockchain networks, (4) testing the blockchains, and (5) summarizing the experience and time used for implementation by students. We evaluated Ethereum, Hyperledger Fabric, and MultiChain, and confirmed that the selection of a proper platform depends on the requirements of the application. The findings of our study can accelerate the process and reduce the risk of adopting blockchain technology in biomedical and healthcare domain.

Wei-Meng Lee

In Chapter 4 , you learned how to create your own private test Ethereum network using the Ethereum client – Geth. While Geth is not that difficult to use to set up an Ethereum blockchain, it still takes considerable effort to set one up. In addition, you also need to create accounts and perform mining in order to obtain Ethers so that you can use them to deploy Smart Contracts and for performing transactions.

Dianhui Mao, Fan Wang, Yalei Wang, Zhihao Hao

Smart contract applications based on Ethereum blockchain have been widely used in many fields. They are developed by professional developers using specialized programming languages like solidity. It requires high requirements on knowledge of the specialized field and the proficiency in contract programming. Thus, it is hard for normal users to design a usable smart contract based on their own demands. Most current studies about smart contracts focus on the security of coding while lack of friendly tools for users to design the specialized templates of contracts coding. This paper provides a visual and user-defined smart contract designing systems. It makes the development of domain-specific smart contracts simpler and visualization for contract users. The system implements the domain-specific features extraction about the crawled data sets of smart contract programs by TF-IDF and K-means++ clustering algorithm. Then, it achieves the automatic generation of unified basic function codes by Char-RNN (improved by LSTM) based on the domain-specific features. The system adopts Google Blockly and links the generated codes with UI controls. Finally, it provides a set of specialized templates of basic functions for users to design smart contracts by the friendly interface. It reduces the difficulty and costs of contract programming. The paper offers a case study to design contracts by users. The designed contracts were validated on the existing system to implement the food trading and traders' credit evaluation. The experimental results show that the designed smart contracts achieve good integration with the existing system and they can be deployed and compiled successfully.

Vinayak Singla, Indra Kumar Malav, Jaspreet Kaur, Sumit Kalra

In today's time, we use Leave Application System managed by some central authority. This can lead to corruption, misuse by a single authority or unnecessary time for approval. So, in this paper, we have developed smart contract architecture for Leave Management System using Solidity and Ethereum, which is a decentralized app architecture leveraged from Blockchain Technology. We also include smartphones as IoT devices by which any client can use this app. Due to the resource-constrained nature of these devices, the smart contract app is coupled with an alternative centralized architecture which is a classic client/server architecture with an underlying Blockchain backend.

Vasily Derbentsev, Natalia Datsenko, Olga Stepanenko, Vitaly Bezkorovainyi

This paper describes the construction of the short-term forecasting model of cryptocurrencies’ prices using machine learning approach. The modified model of Binary Auto Regressive Tree (BART) is adapted from the standard models of regression trees and the data of the time series. BART combines the classic algorithm classification and regression trees (C&RT) and autoregressive models ARIMA. Using the BART model, we made a short-term forecast (from 5 to 30 days) for the 3 most capitalized cryptocurrencies: Bitcoin, Ethereum and Ripple. We found that the proposed approach was more accurate than the ARIMA-ARFIMA models in forecasting cryptocurrencies time series both in the periods of slow rising (falling) and in the periods of transition dynamics (change of trend).

Ximeng Li, Zhiping Shi, Qianying Zhang, Guohui Wang · 6 authors

No abstract is available for this record.

Md. Shohel Rana, Charan Gudla, Andrew H. Sung

No abstract is available for this record.