Andrew Cullen, Pietro Ferraro, Christopher King, Robert Shorten
Recently, Directed Acyclic Graph (DAG) based Distributed Ledgers have been proposed for various applications in the smart mobility domain [1]. While many application studies have been described in the literature, an open problem in the DLT community concerns the lack of mathematical models describing their behaviour, and their validation. Building on a previous work in [1], we present, in this paper, a fluid based approximation for the IOTA Foundation's DAG-based DLT that incorporates varying transaction delays. This extension, namely the inclusion of varying delays, is important for feedback control applications (such as transactive control [2]). Extensive simulations are presented to illustrate the efficacy of our approach.
Summary Proof of stake (PoS) protocols rely on voting mechanisms to reach consensus on the current state. If an enhanced majority of staking nodes, also called validators , agree on a proposed block, then this block is appended to the blockchain. Yet these protocols remain vulnerable to faults caused by validators who abstain either accidentally or maliciously. To protect against such faults while retaining the PoS selection and reward allocation schemes, we study weighted voting in validator committees. We formalize the block creation process and introduce validators' voting profiles which we update by a multiplicative weights algorithm relative to validators' voting behavior and aggregate blockchain rewards. Using this framework, we leverage weighted majority voting rules that optimize collective decision making to show, both numerically and analytically, that the consensus mechanism is more robust if validators' votes are appropriately scaled. We raise potential issues and limitations of weighted voting in trustless, decentralized networks and relate our results to the design of current PoS protocols.
In this paper, we design and implement the first-ever decentralized replicated relational database with blockchain properties that we term blockchain relational database. We highlight several similarities between features provided by blockchain platforms and a replicated relational database, although they are conceptually different, primarily in their trust model. Motivated by this, we leverage the rich features, decades of research and optimization, and available tooling in relational databases to build a blockchain relational database. We consider a permissioned blockchain model of known, but mutually distrustful organizations each operating their own database instance that are replicas of one another. The replicas execute transactions independently and engage in decentralized consensus to determine the commit order for transactions. We design two approaches, the first where the commit order for transactions is agreed upon prior to executing them, and the second where transactions are executed without prior knowledge of the commit order while the ordering happens in parallel. We leverage serializable snapshot isolation (SSI) to guarantee that the replicas across nodes remain consistent and respect the ordering determined by consensus, and devise a new variant of SSI based on block height for the latter approach. We implement our system on PostgreSQL and present detailed performance experiments analyzing both approaches.
Sandi Rahmadika, Diena Rauda Ramdania, Maisevli Harika
Blockchain technology holds great promise to rewire the current financial system which relies on the third party. Every transaction is recorded in a secure and transparent for the parties in the blockchain network. Blockchain technology in the energy sector becomes an interesting topic among researchers at this moment. The use of blockchain allows producers and consumers to trade energy transactions through smart grids because of a decentralized energy trading system. The trading activities without a third party involved would reduce the cost of a transaction thus it brings to a new level of quality of service in the trading system. In this paper, we propose an architectural model for decentralized energy trading system among the neighbors that allows the producer who has the surplus energy to conduct a trading activity with his/her neighbors. The transactions manage by the miners in the same blockchain network. Moreover, we analyze the security issues from various attacks and presenting the performance of the selected attack that might occur in the model.
Fazeel Ahmed Khan, Adamu Abubakar Ibrahim, Marwan Mahmoud, Mahmoud Ahmad Al‐Khasawneh · 5 authors
The emergence of Blockchain have revolutionize the decentralization in distributed architecture. The advances in the consensus mechanism techniques and the development of different variants of consensus algorithms gives a huge impact on its progress. These technologies allow to have a distributed peer-to-peer network in which each external entity can be able to interact with other entities without any trusted intermediary in a verifiable manner. The existing consensus algorithms are mostly concerned with public blockchain having focused on public ledgers in general. The consortium blockchain is least focused as compared with other variants of blockchain (public and private) showing the need to address this vacuum. In this paper, we proposed a consensus algorithm named Rift for consortium blockchain which works on the principle of trust mechanism for achieving consensus in a blockchain. The consensus is achieved by distributed nodes in a consortium blockchain which were controlled by consortium members to decentralize the arbitration by voting and trust metrics. In this paper, we elaborate the comprehensive idea of Rift and discuss the working model for this algorithm. We also perform simulation on the proposed algorithm and determine the performance variables to evaluate the effectiveness of Rift. The evaluated results show the improvement in the performance which is the objective requirement for the evaluation.
In recent decades, Information Technology has contributed fundamentally to the development of financial markets, reforming the way in which financial institutions interact with each other. However, the established practices and norms of this sector may face an all-out overhaul as remarkable innovations such as Blockchain are maturing. The essence of Blockchain is that it is a public, shared and carefully designed record that allows mutually unknown individuals and institutions to share data in a reliable ledger and carry out all kinds of transactions. This ground-breaking technology is developed from cryptography and peer-to-peer network technologies. It is nearly immune to the majority of today's digital threats. Besides financial institutions, Blockchain based solutions have made it into other industries such as real estate, health care, the media as well as Government bodies. This paper will explain how Blockchain works, what it really is, types, its applications and threats and will offer a few ideas for prospective expansion of this technology.
With the ever growing Internet of Things (IoT) market, ledger systems are facing new challenges to efficiently store and secure enormous customer records collected by the IoT devices. The authenticity, availability, and integrity of these records are critically important for both business providers and customers. In this paper, we describe DLedger, a lightweight and resilient distributed ledger system. Instead of a single chain of blocks, DLedger builds the ledger over a directed acyclic graph (DAG), so that its operations can tolerate network partition and intermittent connectivity. Instead of compute-intensive Proof-of-Work (PoW), DLedger utilizes Proof-of-Authentication (PoA), whose light-weight operations are IoT-friendly, to achieve consensus. Furthermore, DLedger is built upon a data-centric network called Named Data Networking (NDN), which facilitates the peer-to-peer data dissemination in heterogeneous IoT networks.
In Bitcoin, to independently verify whether new transactions are correct or not, a type of a node called "Full Node" has to hold the whole of historical transactions. The transactions are stored in ledger called "Blockchain. " Blockchain is an append-only data structure. Thus, to operate Full Nodes, the required storage capacity would grow too large for resource-constrained devices. Due to the limitation, the existing lightweight node scheme is that a node relies on other Full Nodes. In this thesis, to reduce storage capacity with keeping the independence of each node, we propose a storage load balancing scheme "KARAKASA" using Distributed Hash Table (DHT). In KARAKASA, nodes distributedly keep the whole blockchain among DHT networked nodes. We evaluated KARAKASA from the view of storage capacity and independence. As a result, a node in a cluster does not need to trust other nodes. We concluded that nodes in a DHT cluster can behave like Full Nodes without holding the whole blockchain.
Following the recent increase in smart factories and smart cities and the fourth industrial revolution, the number of IoT devices has been increasing and accordingly, the security of IoT devices has also become an important issue. However, due to reasons such as the low performance of IoT devices, the currently existing security solutions can be hardly applied and even if safe firmware is supplied, security problems may arise due to attacks such as man-in-the-middle attacks and roll-back attacks. To resolve such problems, we propose a new firmware management architecture using blockchains and IPFS (The InterPlanetary File System). Using IPFS can ensure the integrity of the firmware. However, IoT device version management and IPFS URL integrity cannot be guaranteed. Therefore, IoT devices are enabled to be provided with firmware information and updated through blockchian networks to ensure the integrity of the IPFS URL, and an IoT devices management function is provided. The proposed system enables safe firmware distribution and update, and IoT devices' security level is expected to be higher. Through the proposed system, safe firmware distribution and update will become possible and IoT device security levels are expected to be enhanced.
Maximiliano Geier, Claudio J. Tessone, Marco Vanotti, Silvio Vilerino · 6 authors
Large-scale distributed systems are becoming more widespread and, at the same time, their sizes grow day by day. In this type of systems, the adoption of blockchains is gaining particular traction for data storage in a secure and distributed manner. Nevertheless, design and testing of new protocols and features face the challenge of determining whether the proposed modifications would actually improve the system as expected. In the case of existing cryptocurrency systems, building an evaluation platform poses additional difficulties due to the resource-consuming nature of the associated processes. In this paper, we propose a novel methodology that relies on container-based network emulation to create scalable local testbeds in which Proof-of-Work-based blockchain systems can be evaluated. Using one of the mainstream Ethereum clients, we replaced the mining algorithm with a simulation model built upon the statistical characteristics of the mining process and instrumented the client to capture relevant network events. These events are used to create an offline reconstruction of the global view of the blockchain and all forking events, and to completely characterize the working conditions under arbitrary setups. Based on the versatility and scalability of our platform, we are able to test several network scenarios of increasing size in which we analyze the incidence of the target time in the generation of contradictory views of the blockchain (i.e. forks). We show that even using a limited testbed constituted by just commodity hardware, it is possible to use our platform to study the dynamics of blockchain-based systems up to hundreds of nodes.
Blockchains were designed to solve the problem of double-spending in cryptocurrencies, and the success of the Bitcoin design has generated vastly more interest than previous proposals for digital currencies. Blockchains are being used in other areas as well, but the design choices that made blockchains effective for cryptocurrencies often do not fit well with other applications. In this paper we review the properties of distributed ledger technology (DLT) for use in typical data management applications and show how two recently developed distributed ledger ideas can be used to retain valuable aspects of blockchain while simplifying design and adding new but often necessary capabilities to permissioned distributed ledger applications. In particular, we are interested in the ability to delete or modify blocks, and the ability to provide a timestamping mechanism to provide a highly accurate time for applications that are time order dependent.
Alberto Sonnino, Shehar Bano, Mustafa Al-Bassam, George Danezis
We present a family of replay attacks against sharded distributed ledgers,\nthat target cross-shard consensus protocols, such as the recently proposed\nChainspace and Omniledger. They allow an attacker, with network access only, to\ndouble-spend or lock resources with minimal efforts. The attacker can act\nindependently without colluding with any nodes, and succeed even if all nodes\nare honest; most of the attacks can also exhibit themselves as faults under\nperiods of asynchrony. These attacks are effective against both shard-led and\nclient-led cross-shard consensus approaches. Finally, we present Byzcuit - a\nnew cross-shard consensus protocol that is immune to those attacks. We\nimplement a prototype of Byzcuit and evaluate it on a real cloud-based testbed,\nshowing that our defenses impact performance minimally, and overall performance\nsurpasses previous works.\n
Same story for Ethereum as well as overall crypto opened with gaps today and some covered it already (Litecoin for example). After price opened with a $31 gap upwards, price consolidated in blue area and started making a steady drop towards the opening l
Scalability of distributed ledgers is a key adoption factor. As an alternative to blockchain-based protocols, directed acyclic graph (DAG) protocols are proposed with the intention to allow a higher volume of transactions to be processed. However, there is still limited understanding of the behaviour and security considerations of DAG-based systems. We present an asynchronous, continuous time, and multi-agent simulation framework for DAG-based cryptocurrencies. We model honest and semi-honest actors in the system to analyse the behaviour of one specific cryptocurrency, IOTA. Our simulations show that the agents that have low latency and a high connection degree have a higher probability of having their transactions accepted in the network with honest and semi-honest strategies. Last, the simulator is built with extensibility in mind. We are in the process of implementing SPECTRE as well as including malicious agents.
Offline electronic cash is a new and well-acknowledged type of e-cash scheme that can release the bank from participating in every spending protocol. However, it is still an unsolved problem to design a secure and efficient fair offline e-cash scheme. Considering this problem, in this paper, we have proposed a fair offline electronic cash scheme with multiple banks in pairing-based instantiation. We adopt Groth–Sahai non-interactive zero-knowledge proof technology in our scheme, to design non-interactive e-cash transactions. Additionally, inspired by Water’s group signature, our solution supports not only multiple users, but also users with accounts in different banks. Moreover, our scheme has efficient double-spending checking and a fair control mechanism. We have formally defined the security properties of the scheme in a standard model, and provided the detailed security proofs of the security properties concerning chosen ciphertext attack (CCA) anonymity, unforgeability and traceability. Analysis and comparison show that our scheme has advantages both in security and in efficiency.
Oksana Lukmanova, Elena Volkova, Anton Zabolotnyi, Aleksandr V. Gorelik
The paper presents the needs to improve the controlling systems in public utilities. One example was the use of blockchain technology in the work of the management company that supports the buildings. The method of such technology in the public utilities management system ensures the transparency of mutual obligations and information security between the consumer and the service provider. This leads to the embodiment in reality of the basic principles of effective relationships: the balance of interests of market participants and the openness of interaction.
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
Anh Le-Tuan, Darshan Hingu, Manfred Hauswirth, Danh Le-Phuoc
RDF stores provide a simple abstraction for publishing and querying data, that is becoming a norm in data sharing practice. They also empower the decentralised architecture of data publishing for the Web or IoT-driven systems. Such architecture shares a lot in common with blockchain infrastructure and technologies. Therefore, there are emerging interests in marrying RDF stores and blockchain to realise desirable but speculative benefits of blockchain-powered data sharing. This paper presents the first RDF store with blockchain that enables lightweight edge devices to control of the data sharing processes (personal, IoT data). Our novel approach on the deep integration of the storage design for RDF store enables the ability to enforce controlling measures on access methods and auditing policies over data elements via smart contracts before they fetched from the sources to the consumers. Our experiments show that the prototype system delivers an effective performance for a processing load of 1 billion triples on a small network of lightweight nodes which costs less than a commodity PC.
In the Bitcoin network, the current block interval time of 10 minutes and the maximum block size of 1MB leads to a low transaction throughput compared to visa and other payment methods. Decreasing the block interval time or increasing the block size may increase the probability of inconsistency, leading to frequent blockchain fork in the Bitcoin network. This work attempts to decrease the block interval and increase the block size without hampering the network with excessive forking. It investigates the peer selection technique of the Bitcoin network for improving its performance. Instead of random peer selection as per the current Bitcoin protocol, it studies the effect of improved peer selection using link information on the performance of the Bitcoin network using a real-time testbed created with Bitcoind [4] client. An efficient peer-to-peer network formed by choosing the optimum peers helps to alleviate the frequency of forking even with a low block interval time and high block size. Geographical location based peer selection [1] and low-latency based peer selection [2] provides a better network formation, but their effect on mean propagation delay, transaction throughput, and stale block rate has not been studied. This work explored various techniques for selecting peers to form the peer-to-peer network. All Pair Shortest Path based and network partition using community detection are explored with a view of optimizing the network globally. A local view of optimizing the network formation considering the particular node is also investigated. This work then proposes to choose peers based on a linear combination of both latency and bandwidth since bandwidth also plays an important role when block size increases. The proposed algorithm generates a score for all the peers received either by DNS seed or by peer discovery mechanism and chooses the top scored peers. Simulation results based on the Bitcoin Simulator [3] show a reduction of about 60-70% in mean propagation delay, 30-35% in stale block rate and an increment of 20-25% in transaction throughput over the original Bitcoin protocol even with a small block interval time of 30 second and high block size of 2MB. The state-of-art BCBPT [2] algorithm is also implemented for the comparison. In addition to this, the practical operation of the proposed approach in the actual Bitcoin network is also discussed. The expected overhead incurred in applying the algorithm in the network is also stated along with the possibility of overhead reduction by the appropriate parameter adjustments.