Blockchain Papers

Marcel Thum

No abstract is available for this record.

Önder Gürcan, Alejandro Ranchal Pedrosa, Sara Tucci-Piergiovanni

Bitcoin-like blockchains do not envisage any specific mechanism to avoid unfairness for the users. Hence, unfair situations, like impossibility of cancellation of transactions explicitly or having unconfirmed transactions, reduce the satisfaction of users dramatically, and, as a result, they may leave the system entirely. Such a consequence would impact significantly the security and the sustainability of the blockchain. Based on this observation, in this paper, we focus on explicit cancellation of transactions to improve the fairness for users. We propose a novel scheme with which it is possible to cancel a transaction, whether it is confirmed in a block or not, under certain conditions. We show that the proposed scheme is superior to the existing workarounds and is implementable for Bitcoin-like blockchains. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Éric Ghysels, Giang Nguyen

We examine price discovery and liquidity provision in the secondary market for bitcoin—an asset with a high level of speculative trading. Based on BTC-e’s full limit order book over the 2013–2014 period, we find that order informativeness increases with order aggressiveness within the first 10 tiers, but that this pattern reverses in outer tiers. In a high volatility environment, aggressive orders seem to be more attractive to informed agents, but market liquidity migrates outward in response to the information asymmetry. We also find support to the Markovian learning assumption often made in theoretical models of limit order markets.

Kartik Hegadekatti

No abstract is available for this record.

Jonathan Taylor Heinecke

Distributed ledger technologies (DLTs) are currently dominating the field of distributed systems research and development. The Ethereum blockchain is emerging as a popular DLT platform for developing software and applications. Several challenges in Ethereum software development are the complex nature of working with DLTs, the lack of tools for developing on this DLT, and poor documentation of concepts for DLT developers. In this thesis, we provide building blocks that reduce the complexity of DLT operations and lower the barrier to entry into DLT development. We do this by providing a Node.js library, Ethereum-Easy, that simplifies operations on Ethereum. We implement this library into a sample application called Rock, Paper, Scissors (RPS) and built a continuous delivery, continuous integration pipeline for deploying Ethereum code (Jenk-Thereum). This thesis aims to make development on DLTs easier, quicker, and less expensive.

Liudmila Zavolokina, Pascal Mehrwald, Isabell M. Welpe, Helmut Krcmar

No abstract is available for this record.

Hans-Georg Fill, Felix Haerer

Blockchains permit to store information in a tamper-resistant and irrevocable manner by reverting to distributed computing and cryptographic technologies. The primary purpose is to keep track of the ownership of tangible and intangible assets. In the paper at hand we apply these concepts and technologies to the domain of knowledge management. Based on the explication of knowledge in the form of enterprise models this permits the application of so-called knowledge proofs for a. enabling the transparent monitoring of knowledge evolution, b. tracking the provenance, ownership, and relationships of knowledge in an organization, c. establishing delegation schemes for knowledge management, and d. ensuring the existence of patterns in models via zero-knowledge proofs. To validate the technical feasibility of the approach a first technical implementation is described and applied to a fictitious use case.

Gaby G. Dagher, Praneeth Babu Marella, Matea Milojkovic, Jordan Mohler

Voting is a fundamental part of democratic systems; it gives individuals in a community the faculty to voice their opinion. In recent years, voter turnout has diminished while concerns regarding integrity, security, and accessibility of current voting systems have escalated. E-voting was introduced to address those concerns; however, it is not cost-effective and still requires full supervision by a central authority. The blockchain is an emerging, decentralized, and distributed technology that promises to enhance different aspects of many industries. Expanding e-voting into blockchain technology could be the solution to alleviate the present concerns in e-voting. In this paper, we propose a blockchain-based voting system, named BroncoVote, that preserves voter privacy and increases accessibility, while keeping the voting system transparent, secure, and cost-effective. BroncoVote implements a university-scaled voting framework that utilizes Ethereum’s blockchain and smart contracts to achieve voter administration and auditable voting records. In addition, BroncoVote utilizes a few cryptographic techniques, including homomorphic encryption, to promote voter privacy. Our implementation was deployed on Ethereum’s Testnet to demonstrate usability, scalability, and efficiency.

Tommy Koens, Erik Poll

No abstract is available for this record.

Benito Arruuada, Luis Garicano

By allowing networks to split, decentralized blockchain platforms protect members against hold up, but hinder coordination, given that adaptation decisions are ultimately decentralized. The current solutions to improve coordination, based on “premining” cryptocoins, taxing members and incentivizing developers, are insufficient. For blockchain to fulfill its promise and out-compete centralized firms, it needs to develop new forms of “soft” decentralized governance (anarchic, aristocratic, democratic, and autocratic) that allow networks to avoid bad equilibria.

Riccardo Longo

Cryptography is used to protect data and communications.
\nThe basic tools are cryptographic primitives, whose security and efficiency are widely studied.
\nBut in real-life applications these primitives are not used individually, but combined inside complex protocols.
\nThe aim of this thesis is to analyse various cryptographic protocols and assess their security in a formal way.
\nIn chapter 1 the concept of formal proofs of security is introduced and the main categorisation of attack scenarios and types of adversary are presented, and the protocols analysed in the thesis are briefly introduced with some motivation. 
\nIn chapter 2 are presented the security assumptions used in the proofs of the following chapters, distinguishing between the hardness of algebraic problems and the strength of cryptographic primitives.
\nOnce that the bases are given, the first protocols are analysed in chapter 3, where two Attribute Based Encryption schemes are proven secure.
\nFirst context and motivation are introduced, presenting settings of cloud encryption, alongside the tools used to build ABE schemes.
\nThen the first scheme, that introduces multiple authorities in order to improve privacy, is explained in detail and proven secure.
\nFinally the second scheme is presented as a variation of the first one, with the aim of improving the efficiency performing a round of collaboration between the authorities.
\n
\nThe next protocol analysed is a tokenization algorithm for the protection of credit cards.
\nIn chapter 4 the advantages of tokenization and the regulations required by the banking industry are presented, and a practical algorithm is proposed, and proven secure and compliant with the standard. 
\nIn chapter 5 the focus is on the BIX Protocol, that builds a chain of certificates in order to decentralize the role of certificate authorities.
\nFirst the protocol and the structure of the certificates are introduced, then two attack scenarios are presented and the protocol is proven secure in these settings.
\nFinally a viable attack vector is analysed, and a mitigation approach is discussed.
\nIn chapter 6 is presented an original approach on building a public ledger with end-to-end encryption and a one-time-access property, that make it suitable to store sensitive data. 
\nIts security is studied in a variety of attack scenarios, giving proofs based on standard algebraic assumptions. 
\nThe last protocol presented in chapter 7 uses a proof-of-stake system to maintain the consistency of subchains built on top of the Bitcoin blockchain, using only standard Bitcoin transactions.
\nParticular emphasis is given to the analysis of the refund policies employed, proving that the naive approach is always ineffective whereas the chosen policy discourages attackers whose stake falls below a threshold, that may be adjusted varying the protocol parameters.

Kristian Lauslahti, Juri Mattila, Taneli Hukkinen, Timo Seppälä

Platform businesses are born global, with instant access to global markets. Thanks to the algorithmic, self-executing and self-enforcing computer programmes known as smart contracts, platform businesses now also have instant access to global capital markets from birth. However, the legal status of these smart-contract-enabled funding mechanisms and smart contracts in general is not well defined. In this article, we analyse how well the formation mechanisms of the general principles of Finnish contract law can be applied to the technological framework of smart contracts. We find that depending on the case, smart contracts can create legally binding rights and obligations to their parties. We also observe that contracts have not been formerly perceived as technical boundary resources in the sense that platform ecosystems could foster broader network effects by opening their application contracting interfaces to third parties.

Tiffany L. Minks

No abstract is available for this record.

Yinan Pei, Kazumasa Oida

No abstract is available for this record.

Haya R. Hasan, Khaled Salah

With the widespread of E-commerce, the need of a trusted system to ensure the delivery of traded items is crucial. Current proof of delivery (PoD) systems lacks transparency, traceability, and credibility. These systems are mostly centralized and rely on trusted third parties (TTPs) to complete the delivery between sellers and buyers. TTPs can be costly, a single point of failure, and subject to hacking, privacy evasion, and compromise. The blockchain is an immutable, trusted, and decentralized ledger with logs and events that can be used for transparency, traceability, and tracking. In this paper, we present a solution and a general framework using the popular permissionless Ethereum blockchain to create a trusted, decentralized PoD system that ensures accountability, auditability, and integrity. The solution uses Ethereum smart contracts to prove the delivery of a shipped item between a seller and a buyer irrespective of the number of intermediate transporters needed. In our proposed solution, all participating entities are incentivized to act honestly by using a double deposit collateral. Automated payment in ether is an integral part of a solution to ensure that every entity gets its intended share of ether upon successful delivery. An arbitration mechanism is also incorporated if a dispute arises during the shipping process. In this paper, we show how we implemented, verified, and tested the proper functionality of our PoD solution. We also provide security analysis and give estimates of the cost consumption in ether gas. We made the full code of the Ethereum smart contracts publicly available at Github.

Md. Mehedi Hassan Onik, Mahdi H. Miraz, Chul‐Soo Kim

Application of Information Technology (IT) in the domain of Human Resource Management (HRM) systems is a sine qua non for any organization for successfully adopting and implementing Fourth Industrial Revolution (Industry 4.0). However, these systems are required to ensure non-biased, efficient, transparent and secure environment. Blockchain, a technology based on distributed digital ledgers, can help facilitate the process of successfully effectuating these specifications. A detailed literature review has been conducted to identify the current status of usage of Information Technology in the domain of Human Resource Management and how Blockchain can help achieve a smart, cost-effective, efficient, transparent and secure factory management system. A Blockchain based Recruitment Management System (BcRMS) as well as Blockchain based Human Resource Management System (BcHRMS) algorithm have been proposed. From the analysis of the results obtained through the case study, it is evident that the proposed system holds definite advantages compared to the existing recruitment systems. Future research directions have also been identified and advocated.

Ryan Amsden, Denis Schweizer

No abstract is available for this record.

Jia Kan, Lingyi Zou, Bella Liu, Xin Huang

In recent years, with the rapid development and popularization of BitCoin, the research of blockchain technology has also shown growth. It has gradually become a new generation of distributed, non-centralized and trust-based technology solution. However, the blockchain operation is expensive and transaction is delayed. Take BitCoin as an example. On the one hand, a block is produced every ten minute. On the other hand, once the new block is generated, it takes a certain time to propagate world wide. The slow speed of propagation determines that BitCoin can not use too small block interval time. Ethereum also faces similar problems, so the concept of uncle block was introduced to reduce blockchain forks. This paper introduces a new tree structure based broadcast propagation routing model, providing a novel method to organize network nodes and message propagation mechanism. In oder to avoid the single node failure problem, the tree cluster routing is proposed. The research shows that the tree based routing can accelerate broadcast convergence time and reduce redundant traffic.

Mohammad Hossein Manshaei, Murtuza Jadliwala, Anindya Maiti, Mahdi Fooladgar

Low transaction throughput and poor scalability are significant issues in public blockchain consensus protocols such as Bitcoins. Recent research efforts in this direction have proposed shard-based consensus protocols where the key idea is to split the transactions among multiple committees (or shards), which then process these shards or set of transactions in parallel. Such a parallel processing of disjoint sets of transactions or shards by multiple committees significantly improves the overall scalability and transaction throughout of the system. However, one significant research gap is a lack of understanding of the strategic behavior of rational processors within committees in such shard-based consensus protocols. Such an understanding is critical for designing appropriate incentives that will foster cooperation within committees and prevent free-riding. In this paper, we address this research gap by analyzing the behavior of processors using a game-theoretic model, where each processor aims at maximizing its reward at a minimum cost of participating in the protocol. We first analyze the Nash equilibria in an N-player static game model of the sharding protocol. We show that depending on the reward sharing approach employed, processors can potentially increase their payoff by unilaterally behaving in a defective fashion, thus resulting in a social dilemma. In order to overcome this social dilemma, we propose a novel incentive-compatible reward sharing mechanism to promote cooperation among processors. Our numerical results show that achieving a majority of cooperating processors (required to ensure a healthy state of the blockchain network) is easier to achieve with the proposed incentive-compatible reward sharing mechanism than with other reward sharing mechanisms.

Thach Ngoc Nguyen, Christian Servín, Владик Крейнович

Nowadays, most financial transactions are based on a centralized system, when all the transaction records are stored in a central location. This centralization makes the financial system vulnerable to cyber-attacks. A natural way to make the financial system more robust and less vulnerable is to switch to decentralized currencies. Such a transition will also make financial system more transparent. Historically first currency of this type -- bitcoin -- use a large amount of electric energy to mine new coins and is, thus, not scalable to the level of financial system as a whole. A more realistic and less energy-consuming scheme is provided by proof-of-stake currencies, where the right to mint a new coin is assigned to a randomly selected user, with probability depending of the user's stake (e.g., his/her number of coins). What probabilities should we choose? In this paper, we find the probability selection that provides the optimal result -- optimal in the sense that it is the least inductive to cheating.

Nikos Fotiou, Vasilios A. Siris, George C. Polyzos

Despite technological advances, most smart objects in the Internet of Things (IoT) cannot be accessed using technologies designed and developed for interacting with powerful Internet servers. IoT use cases involve devices that not only have limited resources, but also they are not always connected to the Internet and are physically exposed to tampering. In this paper, we describe the design, development, and evaluation of a smart contract-based solution that allows end-users to securely interact with smart devices. Our approach enables access control, Thing authentication, and payments in a fully decentralized setting, taking at the same time into consideration the limitations and constraints imposed by both blockchain technologies and the IoT paradigm. Our prototype implementation is based on existing technologies, i.e., Ethereum smart contracts, which makes it realistic and fundamentally secure.

José Carlos Severino Cardoso

O Blockchain é uma tecnologia emergente recentemente generalizada para muitas áreas de atividade. O seu modo de operação descentralizado enquadra-se perfeitamente em vários cenários onde o principal desafio reside na melhoria da comunicação máquina-máquina e na possibilidade de realizar transferências seguras com serviços de valor acrescentado. As redes IoT são uma das áreas possíveis de aplicação da tecnologia Blockchain, uma vez que, para poder satisfazer os requisitos da indústria, a arquitetura atual das redes IoT tem limitações, que podem ser superadas através da melhoria das comunicações entre dispositivos e do acesso a formas evoluídas de agregação e consumo dos dados recolhidos. Este trabalho procura avaliar a combinação desses dois paradigmas - IoT e Blockchain -, procurando entender como o IoT pode beneficiar das funcionalidades que o Blockchain oferece: um sistema de armazenamento mais económico, descentralização e verdadeira redundância, confiança sem autoridade central - privacidade - e segurança reforçada. Por outro lado, o Blockchain como infraestrutura financeira para o IoT é também um aspeto fundamental desse trabalho. Na prova de conceito construída, este cenário é implementado, pois os dados de um sensor podem ser transacionados com uma entidade que os solicite. São igualmente realizadas análises estatísticas e de desempenho relativamente à arquitetura implementada, sendo também apontados alguns pontos de melhoria para alavancar o uso do sistema em situações reais.

Usman Chohan

No abstract is available for this record.

Bingsheng Zhang, Roman Oliynykov, Hamed Balogun

A treasury system is a community-controlled and decentralized collaborative decision-making mechanism for sustainable funding of blockchain development and maintenance. During each treasury period, project proposals are submitted, discussed, and voted for; top-ranked projects are funded from the treasury. The Dash governance system is a real-world example of such kind of systems. In this work, we, for the first time, provide a rigorous study of the treasury system. We modelled, designed, and implemented a provably secure treasury system that is compatible with most existing blockchain infrastructures, such as Bitcoin, Ethereum, etc. More specifically, the proposed treasury system supports liquid democracy/delegative voting for better collaborative intelligence. Namely, the stake holders can either vote directly on the proposed projects or delegate their votes to experts. Its core component is a distributed universally composable secure end-to-end verifiable voting protocol. The integrity of the treasury voting decisions is guaranteed even when all the voting committee members are corrupted. To further improve efficiency, we proposed the world's first honest verifier zero-knowledge proof for unit vector encryption with logarithmic size communication. This partial result may be of independent interest to other cryptographic protocols. A pilot system is implemented in Scala over the Scorex 2.0 framework, and its benchmark results indicate that the proposed system can support tens of thousands of treasury participants with high efficiency.