Blockchain Papers

Dennis K. P. Ng, Paul Griffin

No abstract is available for this record.

Univerza v Mariboru, Fakulteta za elektrotehniko, računalništvo in informatiko, Maribor, Slovenija, Blaž Podgorelec, Muhamed Turkanović, Univerza v Mariboru, Fakulteta za elektrotehniko, računalništvo in informatiko, Maribor, Slovenija

Advanced Information Technology and Services: OTS 2018: Proceedings of the Twenty-Third Conference, 19th -20th of June, 2018. The papers in the proceedings of the 23rd Professional Conference on Advanced Information Technology and Services address the extremely topical challenges that we (IS/IT experts, software engineers, computer scientists, data scientists, software and solution architects, developers, IT managers, etc.) encounter in our daily work. The authors present innovative solutions and rich experience gained by conducting real-life projects: using blockchain technologies and platforms, establishing new ecosystems, business models and services contributing to digital transformation, introducing and implementing micro-service architectures, ensuring security, confidentiality and privacy, and related risk-management techniques, providing full virtualization and exploitation of infrastructure, updating and upgrading existing information systems, integrating machine learning algorithms and intelligent services and big data platforms, developing and using web components and technologies, applying agile approaches that enable the rapid and efficient development of both prototypes and production-oriented user-centric solutions via automated processes and continuous integration, delivery & deployment.

Stefano Bistarelli, Ivan Mercanti, Francesco Santini

In Bitcoin, the most common kind of transactions is in the form "Bob pays Alice", and it is based on the Pay to-Public Key Hash (P2PKH) script. P2PKH transactions are just one among many standard classes: a transaction is standard if it passes BitcoinCore's IsStandard() and IsStandardTx() tests. However, the creation of ad-hoc scripts to lock (and unlock) transactions allows for also generating non-standard transactions, which can be nevertheless broadcast and mined as well. In this work, we explore the Bitcoin block-chain with the purpose to analyse and classify standard and non-standard transactions, understanding how much the standard behaviour is respected.

Emanuel Palm, Olov Schelén, Ulf Bodin

Distributed ledger technologies, such as blockchain systems, have in recent years emerged as promising platforms for machine-to-machine commerce and other forms of multi-stakeholder applications. However, despite the potential demonstrated by projects such as Bitcoin, Ethereum, and Hyperledger Fabric, the disk space typically required to host a copy of a ledger may be prohibitively large for many categories of devices. In this paper, we introduce an approach for reducing ledger size in blockchain systems, based on arbitrary pruning predicate functions, allowing each network participant to independently select and remove any already applied transactions. We also show that if only pruning certain ledger transactions, the ability to derive an unmodified state data structure from the remaining transactions is maintained. The approach is validated through a supply chain use case utilizing a modified version of Hyperledger Fabric, in which ledger size is reduced by about 84.49% via selective transaction pruning.

Bogdan Florea

This paper describes the use of blockchain technology as a data provider in Internet of Things (IoT) applications. Blockchain is a novel technology, which has gained a lot of attention in the last years, mainly due to its use as a backbone for cryptocurrencies. The main purpose of blockchain technology is to provide anonymous transactions between participants, over a peer-to-peer network, using a decentralized distributed ledger. The goal of this novel approach is to eliminate any 3rdparty validation and replace the trust of a central authority for transaction validation with cryptographic proof. While most applications of the blockchain revolve around cryptocurrencies, the blockchain can be used in many other fields, such as finance, distributed data storage, health and medicine, automation, etc. By creating an open, decentralized network, the blockchain can be used to develop decentralized applications and enable data access and sharing on a much higher level than the common implementations of client-server architectures which are in use today. In this paper, we will present a proof of concept method for field devices to store and share data using a distributed ledger built on the IOTA tangle, as well as provide means of access to the data which can be used in IoT and decentralized applications.

Tim Weingaertner, Rahul Rao, Jasmin Ettlin, Patrick Suter · 5 authors

This research addresses the issue that in-depth programming knowhow is needed to read and write smart contracts. The goal was making the creation of smart contracts accessible to non-computer experts by the use of a graphical programming language (Blockly). We used modularization to capture the complexity of legal contracts and developed a mapping process to transform the graphical representation to the smart contract programming language Solidity. We applied our approach to legal purchase agreements and proved the practicality of our solution and explored its limitations. A prototype was built to show the feasibility of our approach. Our industry partner challenged the prototype by applying it to the contract creation process. We consider our work as the first step towards an application of smart contracts in the non-IT world and outside the today's expert shaped ecosystem of blockchain specialists. Several continuative research questions have been derived from our finding and are listed at the end of this paper.

Ravi Kiran Raman, Lav R. Varshney

Blockchain uses the idea of storing transaction data in the form of a distributed ledger wherein each node in the network stores a current copy of the sequence of transactions (ledger) in the form of a hash chain. Storing the entire ledger incurs a high storage cost that grows undesirably large for high transaction rates and large networks. In this work we use secret key sharing, private key encryption, and distributed storage to design a coding scheme such that each node stores only a part of each transaction thereby reducing storage cost to a fraction of the original. When further using dynamic zone allocation, we show the coding scheme can also improve the data integrity.

Pedro W. Abreu, Manuela Aparício, Carlos J. Costa

Blockchain technology is already being talked about as one of the megatrends for the next years. Researchers and organisations are starting to understand the potential benefits of this technology and are exploring how it can disrupt the world we live in with a diverse range of applications. But the truth is the ability to move blockchain from concept to adoption and production has been minimal yet. When it comes to auditing, blockchain solutions could have important benefits by reducing the workload of the auditors, helping in minimising fraud and optimising the existing processes but is also vital to have in mind other emerging technologies. Factom, Libra, and Verady are some examples of companies developing blockchain solutions that can be applied in the auditing environment, but much of the necessary development is still yet to be done.

Lin Chen, Lei Xu, Zhimin Gao, Yang Lü · 5 authors

Proof-of-work was originally proposed by Dwork and Naor in 1992 and has proved its powerfulness in Bitcoin as a decentralized mechanism for blockchain construction. Proof-of-work is the basis of most popular cryptocurrencies and smart contract systems, where participating miners are required to solve difficult mathematical problems to validate transactions. One of the major challenges that proof-of-work faces is the 51% attack, i.e., if an adversary controls more than half of the computation power, he/she can control the blockchain construction and determine which blocks will be included. This is not a major concern when the number of miners is large. However, for an early stage blockchain system with a limited number of users, it is relatively easy for an attacker to launch the 51% attack. To mitigate such risk, we propose a new hybrid blockchain construction scheme that uses the combination of proof-of-work and the stake, which is the number of coins produced by a miner, to determine whether this miner is allowed to construct a block. We prove that stakes play an important role in the hybrid scheme at the beginning, so that an attacker is not able to launch the 51% attack even if he/she controls the majority of the computational power. Meanwhile, the hybrid scheme will converge to pure proof-of-work after sufficiently many blocks are generated, and thus captures the desired properties of proof-of-work. Most importantly, such a convergence is "smooth" in the sense that neither changes in the rules nor parameters are introduced, and thus no hard/soft-forks will be triggered. We also demonstrate the effectiveness of the new scheme using simulations with different configurations, which can help a designer to select adequate parameters for a specific blockchain application.

이진수

No abstract is available for this record.

Rui Qin, Yong Yuan, Shuai Wang, Fei–Yue Wang

With the development of the blockchain technology, Bitcoin mining has become more and more popular. This paper aims to provide a three-level framework of the economic issues in Bitcoin mining research, from the levels of mining pools, individual miners and blockchain network. We also offer an overview of relevant research efforts in literature. Considering the uncertainty, diversity and complexity of the Bitcoin ecosystems, we propose a novel research framework based on the ACP theory, which can be used to explore the economic issues in the Bitcoin ecosystems. This paper aims to provide a preliminary investigation to the economic issues faced by participants in the Bitcoin ecosystems, and stimulate the attentions and interests of researchers in this field.

Lihao Nan, Dacheng Tao

Bitcoin is a decentralized transaction platform and the largest cryptocurrency system. Bitcoin represents a chain of blocks containing its entire legal transaction history, thereby providing convenience for tracking money. However, mixing services are used as an effective means to hide the identity of a transaction address by combining several transfers from different users. Detecting the original user of a Bitcoin address and the money flow is essential in some special circumstances such as anomaly detection. Recognizing Bitcoin mixing services and de-mixing user accounts have only rarely been studied. Here we demonstrate that Bitcoin transaction graphs possess community properties and that a mixing service can be regarded as a cluster outlier. Motivated by the success of graph embedding in social network analysis, we propose a feature-based method to identify mixing services, testing our method on the real Bitcoin ledger.

Dominik Röck, Erik Hofmann

Purpose The purpose of this paper is to develop a business theoretical foundation for distributed ledger technology (DLT) in supply chain management. This consists of describing the theoretical impact of DLT on transaction cost economics, agency theory and network theory from a SCM perspective. Design/methodology/approach We conduct five explorative case studies of five different DLT-based solutions that are implemented in current supply chains. The authors interrogate DLT providers as well as users. Based on the empirical data, the authors derive the impact on three major theories in the field of supply chain management. Findings The paper reveals the theoretical impact of DLT on the above-mentioned theories in the field of SCM. DLT-based solutions reduce the transaction costs and provides new options to coordinate market solutions better than implied before. Furthermore, in contrast to existing implications of network theory, DLT benefits from the size of the network as they reduce the chances for opportunistic behavior and provide more transparency. Research limitations/implications The paper is based on findings of early stage applications of DLT in supply chain management. Thus, theoretical impacts are expected to be added at an advanced stage. However, at this point of time the article builds a theoretical foundation for future research on DLT. Practical implications The identification of theoretical impacts helps to understand the practical value of DLT in supply chain management. Original/value This is one of the first papers to add a theoretical foundation to DLT research in supply chain management that is dominated by application-oriented contributions.

Kazım Rıfat Özyılmaz, Mehmet Ug̃ur Dog̃an, Arda Yurdakul

Today, Internet of Things (IoT) devices are the powerhouse of data generation with their ever-increasing numbers and widespread penetration. Similarly, artificial intelligence (AI) and machine learning (ML) solutions are getting integrated to all kinds of services, making products significantly more "smarter". The centerpiece of these technologies is "data". IoT device vendors should be able keep up with the increased throughput and come up with new business models. On the other hand, AI/ML solutions will produce better results if training data is diverse and plentiful. In this paper, we propose a blockchain-based, decentralized and trustless data marketplace where IoT device vendors and AI/ML solution providers may interact and collaborate. By facilitating a transparent data exchange platform, access to consented data will be democratized and the variety of services targeting end-users will increase. Proposed data marketplace is implemented as a smart contract on Ethereum blockchain and Swarm is used as the distributed storage platform.

Rodelio Arenas, Proceso Fernandez

Blockchain, the underlying technology that powers cryptocurrencies such as Bitcoin and Ethereum, is gaining so much attention from different industry stakeholders, governments and research communities. Its application is extending beyond cryptocurrencies and has been exploited in different domains such as finance, E-commerce, Internet of Things (IoT), healthcare, and governance. Some key attributes of the technology are decentralization, immutability, security and transparency. This paper aims to describe how permissioned Blockchain can be applied to a specific educational use case - decentralized verification of academic credentials. The proposed Blockchain-based solution, named `CredenceLedger', is a system that stores compact data proofs of digital academic credentials in Blockchain ledger that are easily verifiable for education stakeholders and interested third party organizations.

Huawei Zhao, Peidong Bai, Yün Peng, Ruzhi Xu

Healthcare is a big application scenario of blockchain, and blockchains used in healthcare are called health blockchain. In general, blockchain blocks are open and the transactions in them are public. If some privacy data are involved in these transactions, they will be leaked. Owing to healthcare system involving a great deal of privacy data, certain security mechanisms must be built to protect these privacy data in health blockchain. Furthermore, because the core of security mechanisms is the key management schemes, the appropriate key management schemes should be designed before blockchains can be used in healthcare system. Here, according to the features of health blockchain, the authors use a body sensor network to design a lightweight backup and efficient recovery scheme for keys of health blockchain. The authors’ analyses show that the scheme has high security and performance, and it can be used to protect privacy messages on health blockchain effectively and to promote the application of health blockchain.

Stephen DiRose, Mo Mansouri

One of the distinguishing features of blockchain-based Distributed Autonomous Organizations(DAO) is lack of a central authority. Changes to blockchain data is achieved through consensus amongst blockchain network participants, rather than through a central node's authoritative decision. Similarly, governance, i.e., changes to features and underlying source code, is achieved through a decentralized mechanism. As adoption of blockchain has increased, the need to evolve and adopt new features has grown. These changes highlight the mechanism by which the network, rather than a central node, makes decisions. One change in particular, proposed increases to the block size to address scalability limitations, has been particularly demonstrative of the governance mechanisms employed by disparate blockchains. For example, two digital currency projects, Bitcoin and Dash, employ significantly different governance mechanisms: the Dash Decentralized Governance By Blockchain (DGBB) process, and the Bitcoin Improvement Proposal (BIP) process, to decide what changes to make to their blockchains. Dash governance was able to decide to alter the block size in a matter of hours, while Bitcoin governance took several years to make the same decision. This paper evaluates the governance mechanisms of blockchain projects using the change in block size as an exemplar. Two prominent governance mechanisms are described, compared, and assessed based upon how effective they came to consensus and made the decision to change to support the disparate needs of stakeholders.

Jaewon Bae, Hyuk Lim

Bitcoin is a cryptocurrency based on blockchain technology that enables peer-to-peer transactions without a central authority. Bitcoin is known for resolving double-spending problems. When two or more miners generate a block that includes transaction information at nearly the same time, an accidental fork occurs. In this case, the longest chain of blocks is selected to avoid the double-spending problem. However, if there is an attacker node whose hash power is greater than half of the total hash power, that node can perform a double-spending attack, i.e., a 51% or majority attack. We propose a random mining group selection technique to reduce the probability of successful double-spending attacks. The analysis results demonstrate that if the number of groups is greater than or equal to two, the probability that the attacker will find the next block is less than 50%.

Iain Stewart, Dragos Ilie, Alexei Zamyatin, Sam M. Werner · 6 authors

Quantum computers are expected to have a dramatic impact on numerous fields due to their anticipated ability to solve classes of mathematical problems much more efficiently than their classical counterparts. This particularly applies to domains involving integer factorization and discrete logarithms, such as public key cryptography. In this paper, we consider the threats a quantum-capable adversary could impose on Bitcoin, which currently uses the Elliptic Curve Digital Signature Algorithm (ECDSA) to sign transactions. We then propose a simple but slow commit-delay-reveal protocol, which allows users to securely move their funds from old (non-quantum-resistant) outputs to those adhering to a quantum-resistant digital signature scheme. The transition protocol functions even if ECDSA has already been compromised. While our scheme requires modifications to the Bitcoin protocol, these can be implemented as a soft fork.

Thomas J. Gniadek, Peter A. Ball

No abstract is available for this record.

Peter Gaži, Aggelos Kiayias, Alexander Russell

We describe a general attack on proof-of-stake (PoS) blockchains without checkpointing. Our attack leverages transaction fees, the ability to treat transactions "out of context," and the standard longest chain rule to completely dominate a blockchain. The attack grows in power with the number of honest transactions and the stake held by the adversary, and can be launched by an adversary controlling any constant fraction of the stake. With the present statistical profile of blockchain protocols, the attack can be launched given a few years of prior blockchain operation; hence it is within the realm of feasibility for PoS protocols. Most importantly, it demonstrates how closely transaction fees and rewards are coupled with the security properties of PoS protocols. More broadly, our attack must be reflected and countered in any future PoS design that avoids checkpointing, as well as any effort to remove checkpointing from existing protocols. We describe several mechanisms for protecting against the attack that include context-sensitivity of transactions and chain density statistics.

Seong Seok Choi, Jin Wook Burm, Wonjin Sung, Ju Wook Jang · 5 authors

We implement a scheme to securely control IoT devices using smart contracts which resides on blockchain. Our implementation provides guaranteed authentication, nonrepudiation and integrity without any central administration. We illustrate how a smart contract works in conjunction with a blockchain to prevent any tempering from possible intruders. We implement ethereum nodes on Raspberry Pi using node.js and web3 library.

Nikos Fotiou, George C. Polyzos

With the Internet of Things (IoT), Things are expected to live in different “domains” and “contexts” during their lifetime. Information generated by and associated with Things should be manageable by multiple, diverse stakeholders accordingly. Moreover, the scope of the information related to Things can range from private and confidential to public and auditable. Identification, security, and interoperability in this vivid environment are expected to be challenging. In this paper we discuss how smart contracts and blockchain technologies create the potential for a viable solution. To this end, we present smart contract-based solutions that improve security and information management, we identify new opportunities and challenges, and we provide security recommendations and guidelines.

Ahsan Manzoor, Yining Hu, Madhusanka Liyanage, Parinya Ekparinya · 9 authors

Cash-less payment via a variety of credit, debit or prepaid cards is pervasive in our interconnected society, but not so ubiquitous in remote rural regions where network connectivity is intermittent. We proposed a cash-less payment scheme for remote villages based on blockchains that allow maintaining a record of verifiable transactions in a distributed manner. We overcome the limitations of intermittent network connectivity by solely relying on blockchain mining nodes in the village for transaction processing and verification. The bank joins as a peer and monitors node behaviors, rewards miners and processes currency exchanges whenever the connectivity is available. We take advantage of the Ethereum network to develop our solution and demonstrate the feasibility of the proposed system on off-the-shelf computing devices. We emulate a remote village scenario with intermittent network connectivity and show the robustness and reliability of the proposed system.