Interconnecting cyber-physical systems in networks leads to the creation of cyber-physical system-of-systems. In a cyber-physical system-of-systems (CPSoS), systems communicate by exchanging and sharing data and information, which this chapter also refers to as interoperability of information. To ensure reliable and secure interoperability of information between distributed cyber-physical systems, using blockchain technology or distributed ledging technology for distributed entities is an interesting option. Such a blockchain must, at a minimum, be fault tolerant and enable the entities involved to reach consensus on the information transactions that are to be performed. Once consensus about transactions between cyber-physicals is reached, it must be possible for these to record consistently the used data in a distributed ledger that provides a permanent shared overview of completed information transactions. The development of the new technology we call blockchain creates a new and as yet unfathomable reality of interconnected autonomous and self-organising cyber-physical systems that have the ability to make decisions about or for us as human beings.
Antonio Fernández Anta, Chryssis Georgiou, Nicolas Nicolaou
The various applications using Distributed Ledger Technologies (DLT) or blockchains, have led to the introduction of a new `marketplace' where multiple types of digital assets may be exchanged. As each blockchain is designed to support specific types of assets and transactions, and no blockchain will prevail, the need to perform interblockchain transactions is already pressing. In this work we examine the fundamental problem of interoperable and interconnected blockchains. In particular, we begin by introducing the Multi-Distributed Ledger Objects (MDLO), which is the result of aggregating multiple Distributed Ledger Objects -- DLO (a DLO is a formalization of the blockchain) and that supports append and get operations of records (e.g., transactions) in them from multiple clients concurrently. Next, we define the AtomicAppends problem, which emerges when the exchange of digital assets between multiple clients may involve appending records in more than one DLO. Specifically, AtomicAppend requires that either all records will be appended on the involved DLOs or none. We examine the solvability of this problem assuming rational and risk-averse clients that may fail by crashing, and under different client utility and append models, timing models, and client failure scenarios. We show that for some cases the existence of an intermediary is necessary for the problem solution. We propose the implementation of such intermediary over a specialized blockchain, we term Smart DLO (SDLO), and we show how this can be used to solve the AtomicAppends problem even in an asynchronous, client competitive environment, where all the clients may crash.
Blockchain has been widely adopted in the last few years even though it is in its infancy. The first well-known application built on blockchain technology was Bitcoin, which is a decentralized and distributed ledger to record crypto-currency transactions. All of the transactions in Bitcoin are anonymously transferred and validated by participants in the network. Bitcoin protocol and its operations are so reliable that technologists have been inspired to enhance blockchain technologies and deploy it outside of the crypto-currency world. The demand for private and non-crypto-currency solutions have surged among consortiums because of the security and fault tolerant features of blockchain. To introduce blockchain concepts, we survey the three most popular blockchain architectures: Bitcoin, Ethereum, and Hyperledger Fabric. We then build Gradubique, a blockchain network built on top of Hyperledger Fabric. Gradubique allows instructors from any school to post exam and course grades to the Gradubique network. Employers and graduate schools can extract transcripts from Gradubique. Security is guaranteed by the blockchain technology. Standardization and translation of transcripts can be built into the network, and the distributed nature of the network can make it virtually cost-free.
Leonardo da Costa, André Neto, Billy Pinheiro, Weverton Cordeiro · 6 authors
Summary In blockchain, full nodes (FNs) are peers that store and verify entire chains of transactions. In contrast, light clients (LCs) are those with limited resources, and for this reason, they request only block headers from FNs for transaction verification—using protocols like Simple Payment Verification (SPV). In an approach to prevent FN tampering on transaction verification (byzantine fault), LCs request block headers from multiple FNs and compare received responses. One problem with this approach is that an LC must connect to each FN and perform the same cryptographic operations with each one repeatedly, which leads to client‐side complexity and slower response. We propose an alternate approach to tackle this issue, in which LCs can encrypt a request for block headers only once, and send that request to a predetermined set of FNs to access, process, and reply back in a single response. Our approach, called Distributed Lightweight Client Protocol (DLCP), enables LCs to verify with little effort if FNs have agreed on a response. From an experimental evaluation, we observed that DLCP provided lower latency and reduced computing and communication overhead in comparison with the existing conventional approach.
In this paper, we use the credit mechanism of E-commerce platform to evaluate the transaction subject as user reviews, and evaluate the credit degree of the blockchain nodes based on the consensus algorithm of the consortium blockchain as node reviews, then associate the node credit score consisting of user and node reviews with the transaction cost to substitute the incentive effect of the block reward for ledger maintenance. According to the score-pricing strategy we will introduce later, this incentive method can ameliorate the problem of too concentrated bookkeeping permissions and improve the initiative of the accounting node.
Beverley A. MacKenzie, Robert Ian Ferguson, Xavier Bellekens
In a few short years the Internet of Things has become an intrinsic part of everyday life, with connected devices included in products created for homes, cars and even medical equipment. But its rapid growth has created several security problems, with respect to the transmission and storage of vast amounts of customers data, across an insecure heterogeneous collection of networks. The Internet of Things is therefore creating a unique set of risk and problems that will affect most households. From breaches in confidentiality, which could allow users to be snooped on, through to failures in integrity, which could lead to consumer data being compromised; devices are presenting many security challenges to which consumers are ill equipped to protect themselves from. Moreover, when this is coupled with the heterogeneous nature of the industry, and the interoperable and scalability problems it becomes apparent that the Internet of Things has created an increased attack surface from which security vulnerabilities may be easily exploited. However, it has been conjectured that blockchain may provide a solution to the Internet of Things security and scalability problems. Because of blockchain's immutability, integrity and scalability, it is possible that its architecture could be used for the storage and transfer of Internet of Things data. Within this paper a cross section of blockchain consensus protocols have been assessed against a requirement framework, to establish each consensus protocols strengths and weaknesses with respect to their potential implementation in an Internet of Things blockchain environment.
It is difficult these days to avoid hearing about blockchain. Despite the significant potential of blockchain, it is also difficult to find a consistent description of what it really is. This article looks at the basics of blockchain: the individual components, how those components fit together, and what changes might be made to solve some of the problems with blockchain technology.
Chun‐Wei Chen, Jianwei Su, Tung-Wei Kuo, Kung Chen
In this paper, we focus on the design of consensus algorithms for permission-based blockchains, i.e., private blockchains. In most consensus algorithms, blocks are proposed by a specific role called “leader”. In this paper, we introduce a new role called “witness” to supervise the leader. The presence of the witness facilitates the design of the consensus algorithm. We propose a witness-based consensus algorithm that guarantees safety and liveness. We implemented this consensus algorithm on Go Ethereum. The experimental result shows that in a blockchain where four nodes participate in the consensus process, we can achieve a throughput of 1000 transactions per second (TPS). Even if these four nodes are located on different continents, and one of them is faulty, we can still achieve a throughput of 300 TPS. Finally, we find that during the experiment, a significant portion of time is spent on activities other than the consensus task. The result suggests that to further increase the throughput of a private blockchain, the consensus task and non-consensus activities should be considered jointly.
Blockchain is an emerging decentralized infrastructure and distributed computing paradigm. Blockchain has been widely used in many industries including finance, energy, and cloud computing. Consortium blockchain is known as the permissioned blockchain, in which each user needs to be authorized. Distributed consensus is the core issue of consortium blockchain technology. In order to solve the disadvantages of using Proof of Work (POW) algorithm in consortium blockchain, such as computing resources waste, long block confirmation delay and low throughput, we designed and implemented a high performance blockchain consensus algorithm based on message passing technology called HPBC. HPBC algorithm can work well in asynchronous networks with Byzantine nodes. Results from theoretical analysis and performance evaluation show that HPBC algorithm provides safe and reliable distributed consensus services in consortium blockchain with low overhead. Finally, we summarized HPBC algorithm and briefly explore its further research directions.
Some recent trends in distributed intelligent systems rely extensively on agent-based approaches. The so-called Multi-Agent Systems (MAS) are taking over the management of sensitive data on behalf of their producers and users (e.g., medical records, financial investment, energy market). Therefore, trusted interactions are needed more than ever, while accountability and transparency among the agents seem crucial characteristics to be achieved. To do so, recent trends advocate the use of blockchain technologies (BCT) in MAS. The blockchain is a distributed ledger technology that can execute programmable transaction logic, and provides a shared, immutable, and transparent append-only register of all the actions happening in the network. Although a few theoretical approaches have already been proposed, the quest for such a system consolidating BCT and MAS to guarantee privacy, scalability, transparency, and efficiency continues. This paper presents a reconciling system including BCT within the dynamics of a MAS. Such a system aims at (i) building a solid ground for trusted interactions and (ii) enabling more characterizing feature-based and trustworthy ways of computing agent reputation. The system has been tested in four scenarios with different configurations (regular executions and involving down-agents or malicious behaviors). Finally, the paper summarizes and discusses the experience gained, argues about the strategic choice of binding MAS and BCT, and presents some future challenges.
IOTA is a novel cryptocurrency that uses distributed ledger technology based on directed acyclic graph data structure. Security of cryptocurrencies ought to be scrutinized in order to acquire esteemed security, attain trust, and accomplish indelible adoption. Although IOTA proffer resilient security controls, IOTA security is not yet well explored. Among all the propounded IOTA vulnerabilities that have been identified, we pragmatically exploit replay attack against IOTA. We further analyze the attack to perceive its impact. Attack methodology and proof of concept for the replay attack is presented. Our proposed exploitation methodology is based upon address reuse, while IOTA in default mode does not reuse addresses. Distrust, and privation of balance can be some of the severe impacts of this vulnerability.
Blockchain technology and its applications have played an important role to overcome challenges in numerous areas of the life. However, most current blockchain projects have concentrated on financial model by using existing platforms such as Bitcoin or Ethereum to generate tokens without the development of the technological features. Unfortunately, the decentralization has several challenges which cannot be adopted by our current political, economic and social systems. The fundamental technical problem of current blockchain algorithm is that `performance inefficiency' could not be solved, in comparison with the central server system. In addition, the client software cannot establish conventions for making decisions about the future direction of the cryptocurrency. Furthermore, users' completed anonymity and the absence of a responsible person are also open problems of decentralization. To this end, this paper proposes an alternative method, dubbed RCANE which is semi-centralized network of parallel blockchain and APoS (Authorized Proof of Stake), whose purpose is to solve the above challenges of current blockchain and comply with our preconceived perspectives of the current political, social, and economic systems to build up an ecosystem for economy, society and politics. Several experiments are conducted to show the executability of RCANE Project.
Eranga Bandara, Wee Keong Ng, Kasun De Zoysa, Owen Noel Newton Fernando · 7 authors
Blockchain is a peer-to-peer distributed storage that stores chronological series of transactions in a tamper-resistant manner. Blockchain became popular in various industries due to its decentralized trust ecosystem. When integrating blockchain with big data, one encounters many challenges. Current public blockchain does not support high transaction throughput; it does not scale in terms of big data storage and management; it does not provide keyword-based search and retrieval; and so on. As a result, it is hard to incorporate existing blockchain systems for big data applications. In this research, we propose a new blockchain storage "Mystiko" that is built over the Apache Cassandra distributed database to incorporate big data. Mystiko supports high transaction throughput, high scalability, high availability and full text search features. With Mystiko, we make big data more secure, structured and meaningful, and allows further data analytics on big data to be more easily performed.
The Practical Byzantine Fault Tolerance algorithm (PBFT)has been highly applied in consortium blockchain systems, however, this kind of consensus algorithm can hardly identify and remove faulty nodes in time, and also vulnerable to many attacks against the primary node of PBFT. The equality of consortium members' discourse rights is inapplicable to some real scenarios where dominating members are likely to have a larger discourse rights in the voting process. To address these problems, this paper presents Reputation-based Byzantine Fault Tolerance (RBFT)algorithm that incorporates a reputation model to evaluate the operations of each node in the consensus process. The faulty nodes will get lower discourse rights in the voting process if any malicious behavior is detected, with their reputation decreased. Furthermore, this paper presents an innovative reputation-based primary change scheme. The node with higher reputation obtains greater opportunities to be a primary to generate new valid blocks, which reduces the security risk of the primary. The experimental results demonstrate that RBFT gains better performance and ensures system security and reliability. Compared with PBFT, it increases the average throughput by 15% and reduces delay by 10%, and the faulty node rate of the system can continue to decrease over time.
Blockchain technologies are rapidly gaining attention in the multi-agent systems (MAS) community to face critical issues such as trust, secured communications, and data consistency. In particular, the notion of smart contract can be exploited to deploy trustworthy computations automatically executed by the network in a consistent way. MAS coordination - modelling and engineering of agents interaction in a MAS - thus represents an appealing application field for smart contracts, potentially enabling fully-decentralised, trustworthy coordination. Along this line, we focus on the Ethereum blockchain technology, map it onto LINDA tuple-based coordination model, and discuss two proof-of-concept implementations of LINDA on Ethereum. We hence demonstrate conceptual and technical feasibility of blockchain-based coordination in MAS, while emphasising issues of applying the blockchain beyond accountability and identity management.
Wai Yan Maung Maung Thin, Naipeng Dong, Guangdong Bai, Jin Dong
Blockchain technology relies on consensus algorithms to resolve conflicts in Byzantine environments. New blockchain algorithms are rapidly designed and implemented without a properly conducted formal analysis and verification. In this paper, we conducted a study on Tendermint which is a proof-of-stake consensus algorithm. We verified that the consensus protocol is deadlock-free and is able to reach consensus when at least 2/3 of the network is in agreement. We also proved that a minority set of nodes that compose more than 1/3 of the network is enough to censor the majority of the network and prevent the network from reaching consensus and conclude that the algorithm has some shortcomings on availability.
Distributed Ledger Technology is getting famous day by day. Not only investors, financial organizations and technical personnel are interested in this technology, but also government and nearly every other organization are showing interest in this evolving technology. This technology deals with the settlement of transactions without the need of any third party. But it also requires that different nodes distributed all over the world should have the same state of the data to prevent faulty transactions for which there is a need of consensus algorithms. Many algorithms have already been developed and implemented. This paper discusses some of the algorithms that are widely accepted or talked about and also compares them in terms of centralization, energy consumption, transaction rate etc.
The fundamental problem in digital record-keeping is establishing consensus on an update to a ledger, e.g., a payment. Consensus must be achieved in the presence of faults-situations in which some computers are offline or fail to function appropriately. Traditional centralized record-keeping systems rely on trust in a single entity to achieve consensus. Blockchains decentralize record-keeping, dispensing with the need for trust in a single entity, but some instead build a consensus based on the wasteful expenditure of computational resources (proof-of-work). An ideal method of consensus would be tolerant to faults, avoid the waste of computational resources, and be capable of implementing all individually rational transfers of value among agents. We prove a Blockchain Trilemma: any method of consensus, be it centralized or decentralized, must give up (i) fault-tolerance, (ii) resource-efficiency, or (iii) full transferability.
Many blockchain consensus protocols have been proposed recently to scale the throughput of a blockchain with available bandwidth. However, these protocols are becoming increasingly complex, making it more and more difficult to produce proofs of their security guarantees. We propose a novel permissionless blockchain protocol OHIE which explicitly aims for simplicity. OHIE composes as many parallel instances of Bitcoin's original (and simple) backbone protocol as needed to achieve excellent throughput. We formally prove the safety and liveness properties of OHIE. We demonstrate its performance with a prototype implementation and large-scale experiments with up to 50,000 nodes. In our experiments, OHIE achieves linear scaling with available bandwidth, providing about 4-10 Mbps transaction throughput (under 8-20 Mbps per-node available bandwidth configurations) and at least about 20x better decentralization over prior works.
Aggregate Computing is a promising paradigm for coordinating large numbers of possibly situated devices, typical of scenarios related to the Internet of Things, smart cities, drone coordination, and mass urban events. Currently, little work has been devoted to study and improve security in aggregate programs, and existing works focus solely on application-level countermeasures. Those security systems work under the assumption that the underlying computational model is respected; however, so-called Byzantine behaviour violates such assumption. In this paper, we discuss how Byzantine behaviours can hinder an aggregate program, and exploit application-level protection for creating bigger disruption. We discuss how the blockchain technology can mitigate these attacks by enforcing behaviours consistent with the expected operational semantics, with no impact on the application logic.
Eberhard Hechler, Martin Oberhofer, Thomas Schaeck
Most people believe that the paper from 2008 by Satoshi Nakamoto, a pseudonym used by a yet unknown author, introduced the concept of blockchain. However, the key idea is actually 17 years older. The first mentioning of key blockchain concepts goes back to 1991 when Stuart Haber and Scott Stornetta described the concept of a cryptographically secured chain of blocks for the first time.
Hans‐Arno Jacobsen, Mohammad Sadoghi, Mohammad Hossein Tabatabaei, Roman Vitenberg · 5 authors
Known for powering cryptocurrencies such as Bitcoin and Ethereum, blockchain is seen as a disruptive technology capable of revolutionizing a wide variety of domains, ranging from finance to governance, by offering superior security, reliability, and transparency founded upon a decentralized and democratic computational model. In this tutorial, we first present the original Bitcoin design, along with Ethereum and Hyperledger, and reflect on their design choices through the academic lens. We further provide an overview of potential applications and associated research challenges, as well as a survey of ongoing research directions related to byzantine fault-tolerance consensus protocols. We highlight the new opportunities blockchain creates for building the next generation of secure middleware platforms and explore the possible interplay between AI and blockchains, or more specifically, how blockchain technology can enable the notion of "decentralized intelligence." We conclude with a walkthrough demonstrating the process of developing a decentralized application using a popular Smart Contract language (Solidity) over the Ethereum platform