Bitcoin was proposed as an alternative to a centralized trust-based financial system in 2008 which uses distributed ledger called blockchain as the underlying technology. Bitcoin uses a peer-to-peer network without a third trusted party but still maintained trust in the network. The consensus mechanisms do the task of trust-building by executing certain algorithms to bring consensus to the peer nodes of the network. The consensus mechanism used in bitcoin is Proof of Work which involves a massive computation of hashes to validate a block and add it to the blockchain. As the applicability of blockchain increased, the computation-heavy consensus mechanisms were not suitable for real-time transactions. And so, there is a need for a new efficient and high throughput consensus mechanism. This paper proposes a new consensus mechanism using a scope index to mine a new block. This consensus mechanism deals with forking conditions, and the presence of malicious nodes in the network is also studied and compared with other consensus mechanisms.
Proof of stake consensus algorithm (PoS) has the advantage of not requiring arithmetic power, however, the higher the stake, the more likely the node will get the right to account. As a result, the accounting nodes are highly deterministic and the rich get richer, once the node with the highest equity fails to account for the block properly. The rest of the nodes have to compete again for accounting rights, and the probability of system stagnation will increase sharply. To address these two shortcomings, a consensus algorithm based on dynamic delegation of proof of importance (DPoI) is proposed.The algorithm introduces an importance assessment scheme that calculates the importance ivlaue (iValue) of nodes in each round based on nodes aValue, iTrade, Ltime and Credit.Finally, the Fibonacci series is used to divide nodes with similar iValue into a group, and the group draws on the DPoS voting strategy ranking to act as alternative nodes, thus forming a disaster recovery scheme to effectively avoid system stagnation, which effectively enhances the security and stability of the blockchain system. The experimental results show that the speed of DPoI block out is about 6 times faster than PoI, which significantly improves the block out speed.
Christian Cachin, Jovana Mićić, Nathalie Steinhauer, Luca Zanolini
Leader-based protocols for consensus, i.e., atomic broadcast, allow some processes to unilaterally affect the final order of transactions. This has become a problem for blockchain networks and decentralized finance because it facilitates front-running and other attacks. To address this, order fairness for payload messages has been introduced recently as a new safety property for atomic broadcast complementing traditional agreement and liveness. We relate order fairness to the standard validity notions for consensus protocols and highlight some limitations with the existing formalization. Based on this, we introduce a new differential order fairness property that fixes these issues. We also present the quick order-fair atomic broadcast protocol that guarantees payload message delivery in a differentially fair order and is much more efficient than existing order-fair consensus protocols. It works for asynchronous and for eventually synchronous networks with optimal resilience, tolerating corruptions of up to one third of the processes. Previous solutions required there to be less than one fourth of faults. Furthermore, our protocol incurs only quadratic cost, in terms of amortized message complexity per delivered payload.
А. В. Богданов, Vladimir Korkhov, Nadezhda Shchegoleva, Vasilii M. Khvatov · 8 authors
Potential benefits of implementation of distributed ledger technology are widely discussedamong different business actors and governmental structures. Within the last decade, with growingpopularity of blockchain-based payment systems and cryptocurrencies, these discussions considerablysharpened. Therefore, an extensive body of research has emerged on this soil. The goal of this study isto attempt to make a comparative analysis of several existing blockchain-based distributed ledgerplatforms. Besides that, authors overview the most commonly used consensus algorithms and designapproaches, as for any blockchain product, consensus algorithm is a crucial part which determines theperformance of the overall system. Choosing the right algorithm would ensure high reliability andthroughput, while the wrong choice could cause fatal malfunctions for the application. A suitablealgorithm usually should be chosen according to the task in consideration, e.g. Nakamoto-styleprotocols could be considered better for public networks, while multiround voting protocols are moresuitable for private and secure systems. The highest attention is paid to consensus algorithms based onthe solution of the Byzantine Fault Tolerance problem (BFT).
Kaja Schmidt, Alexander Mühle, Andreas Grüner, Christoph Meinel
The current Self-Sovereign Identity (SSI) ecosystem is rapidly changing and ill-defined. Manifold actors, projects, and initiatives produce different SSI solutions, frameworks, protocols, and distributed ledgers. Even though some patterns exist among SSI ecosystem members, no elaborate systematization has been made. This paper conducts a systematic gray literature review to structure the SSI ecosystem. Specifically, we derive a four-dimensional taxonomy that portrays members of the SSI ecosystem. Then, we classify the ecosystem members into eight archetypes. The goals are to allow researchers to describe SSI ecosystem members, help new and existing members locate themselves within the SSI ecosystem, and provide an overview of members’ functionalities. We find that SSI ecosystem members either govern the SSI ecosystem and/or networks, implement SSI offerings, or support governing and/or implementing members. The study suggests that, as the SSI ecosystem grows, the number of governing members will grow slower than the number of implementing and supporting members.
Abstract We analyze the protocol of the bitcoin blockchain by using the PRISM probabilistic model checker. In particular, we (i) extend PRISM with the ledger data type , (ii) model the behavior of the key participants in the protocol—the miners —and (iii) describe the whole protocol as a parallel composition of processes. The probabilistic analysis of the model highlights how forks happen and how they depend on specific parameters of the protocol, such as the difficulty of the cryptopuzzle and the network communication delays. Our results confirm that considering transactions in blocks at depth larger than 5 as confirmed is reasonable because the majority of miners have consistent blockchains up‐to that depth with probability of almost 1. We also study the behavior of networks with churn miners, which may leave the network and rejoin afterwards, and with different topologies.
Seyed Hossein Haeri, Peter Thompson, Neil Davies, Peter Van Roy · 6 authors
This paper directly addresses a critical issue that affects the development of many complex distributed software systems: how to establish quickly, cheaply and reliably whether they will deliver their intended performance before expending significant time, effort and money on detailed design and implementation. We describe ΔQSD, a novel metrics-based and quality-centric paradigm that uses formalised outcome diagrams to explore the performance consequences of design decisions, as a performance blueprint of the system. The ΔQSD paradigm is both effective and generic: it allows values from various sources to be combined in a rigorous way, so that approximate results can be obtained quickly and subsequently refined. ΔQSD has been successfully used by Predictable Network Solutions for consultancy on large-scale applications in a number of industries, including telecommunications, avionics, and space and defence, resulting in cumulative savings of $Bs. The paper outlines the ΔQSD paradigm, describes its formal underpinnings, and illustrates its use via a topical real-world example taken from the blockchain/cryptocurrency domain, where application of this approach enabled an advanced distributed proof-of-stake system to meet challenging throughput targets.
In this paper, we present a plugin for visualising vote based consensus\nmechanisms primarily aimed to help engineers understand and debug blockchain\nand distributed ledger protocols. Both tools are built as Grafana plugins and\nmake no assumptions on the data storage implementation. The plugins can be\nconfigured via Grafana plugin configuration interface to fit the specifics of\nthe protocol implementation.\n
Dec 2, 2021·2021 IEEE 2nd International Conference on Technology, Engineering, Management for Societal impact using Marketing, Entrepreneurship and Talent (TEMSMET)
Offline digital payment systems are currently limited in their scope. Extending them using new technologies like blockchain can expand the offline payment landscape and create new directions for payment systems. This paper proposes XipCOIN as a construction of such a system, based on the Ethereum blockchain. It exploits the recently defined Layer 2 Rollups model of significantly increasing performance and creating desirable transaction characteristics by moving the transactions off the primary Layer 1 blockchain. XipCOIN builds on the approach, established in previous studies by Dmitrienko et al. and Takahashi et al., of using a Trusted Execution Environment to validate the transaction offline by the payee with the payer trusting the payee signature on the confirmation.
Blockchain has attracted wide attention in both industry and academia due to its decentralized and anti-tamper characteristics. To query the blockchain data, all the transactions in the blockchain must be iterated one by one, which is quite inefficient. Existing solutions improve the query efficiency by exporting transactions to external databases, and yet they incur the incompleteness and incorrectness of query results. To avoid above weaknesses, we propose an efficient query method based on the internal blockchain database and apply it to the construction engineering management to solve the problems of information management. In our design, we construct a dual-index based on the B+ tree and the key-value pair through smart contracts, and it supports multiple query operations, such as range query and file-type query. We implement the designed method by simulating the blockchain testbed and the experimental results demonstrate the efficiency of our design.
Blockchain has been prospering for the last decade. Despite the tremendous success of block chain, it is still vulnerable due to the complexity of distributed execution environment. Malicious attacks that exploit these vulnerabilities can lead to serious losses. Common Knowledge Base (CKB) is a public permissionless blockchain and the base layer of N ervos Network, which is gaining popularity in recent years. It adopts a novel con-sensus protocol to overcome two shortcomings of Bitcoin: the low transaction processing throughput and the vulnerability to selfish mining attacks. Considering the high-security requirements in CKB application scenarios, it is essential to provide formalization and verification of the safety and security properties of the CKB blockchain. In this paper, we provide a formal model of CKB consensus protocol in the theorem prover Coq. Fundamental components of the protocol are implemented, including the block structure, the two-step transaction confirmation mechanism, and the peer-to-peer asynchronous network. We also use Coq to establish the quiescent consistency property of the consensus protocol, which is a kind of eventual consensus that all the participants agree on the same ledger when there are no inflight messages.
Blockchain as a potentially disruptive technology can advance many different fields, e.g., cryptocurrencies, supply chains, and the industrial Internet of Things. The next-generation blockchain ecosystem is expected to consist of various homogeneous and heterogeneous distributed ledgers. These ledger systems will inevitably require a certain level of proper cooperation of multiple blockchains to enrich advanced functionalities and enhance interoperable capabilities for future applications. The interoperability among blockchains will revolutionize current blockchain design principles, like the emergence of the Internet. However, the development of cross-blockchain applications involves much complexity regarding the variety of underlying cross-blockchain communication. With that regard, we propose an efficient, interoperable blockchain architecture, InterTrust, to support interoperability and trustworthiness among arbitrary blockchain systems (including homogeneous and heterogeneous blockchains). It consists of an atomic cross-chain communication protocol, which can be considered an agnostic protocol to integrate existing blockchain systems smoothly. InterTrust is powered by two innovative techniques: threshold signature scheme and trusted hardware. The threshold signature scheme guarantees consistency and verifiability in the target blockchain systems, and the trusted hardware guarantees trusted services among distinct blockchain systems. Combining these two techniques provides an efficient cross-chain communication protocol to facilitate atomic swaps and interoperable operations between different blockchain systems. Our interoperable architecture is robust to support arbitrary blockchain systems. We also present the security analysis on the scenarios of integrating our protocol into Byzantine fault tolerance based blockchain systems.
Due to the high interest in the past few years, blockchain technology benefited from a fast increase in adoption rate as well as fast evolution. One of the crucial points in the blockchain space, the consensus mechanism, generally still suffers from lack of development, thus decreasing the adoption of the technology in big scale projects and daily use. Older-established consensus algorithms, such as Proof of Work (PoW) and Proof of Stake (PoS), suffer from various flaws, ranging from the high costs of maintaining a node in the network and generating new blocks, to the risk of being affected by a series of attacks, as well potential of network monopoly by various entities. This paper proposes a model of a democratically-governed consensus algorithm that is focused on a fair distribution of assets, with a fast and secure way of validating and distributing the blocks, while being impervious to a sizeable range of attacks.
David Last, Michael Atighetchi, Partha Pal, Ryan Toner
The US military is focused on transitioning its warf-ighting philosophy towards the Multi-Domain Command and Control (MDC2) concept, which integrates lands, sea, air, space, and cyberspace forces into a unified planning and execution structure. This structure depends on reliable exchange of plans and intelligence reports, which is hindered by the development of adversary capabilities in the areas of radio jamming and other communications-denying technologies. The battlefield of the future will consist of dispersed units with intermittent, constrained communications who nevertheless need to maintain a consistent view of shared plans and information. We are developing a proof-of-concept prototype MDC2 system to explore the requirements and limitations of a solution in this space. There are many distributed database solutions that could be used for this prototype; upon investigation, we believe that Distributed Ledger Technologies (DLT) are an ideal fit for the particular constraints of this use case. We have selected Hyperledger Fabric as the particular DLT implementation on which we are building this prototype. As part of this research, we are developing a Hyperledger-based prototype as well as a baseline implementation that reflects how the DoD handles this process today. We will use both of these systems in a series of experiments that evaluate how well they perform in the areas of database consistency, constrained tactical networks, and conditional authorities, and we will measure their performance using a suite of metrics that will allow us to compare the DLT-based prototype with the baseline system. This paper outlines the challenges we will address through this research; the completed research will encompass our solutions to these challenges.
We consider a hierarchical structure of a permissioned blockchain with three types of participant: providers, collectors, and governors. Providers forward transactions to collectors; collectors upload received transactions to governors after verifying and labeling them; and governors validate a portion of the labeled transactions they receive, pack valid transactions into a block, and append the block to the ledger. This model has various fields of application including data collection from the Internet-of-Things and second-hand markets. Our main contribution is to propose a reputation-based protocol to help governors evaluate the reliability of collectors. Specifically, given a transaction, each governor runs a softmax-based function to calculate a probability for each collector that sent and labeled this transaction. The probabilities, calculated using collectors’ reputations as inputs, represent the likelihood of the lead governor selecting the labeled transaction from collectors to consider for further validation. After the lead governor verifies a transaction, all collectors’ reputations are updated in line with the agreement of their labeling and the validity of the transaction as found by the lead governor. We show, both theoretically and empirically, that our protocol can significantly reduce governors’ verification workloads while maintaining firm liveness and high incentives.
Byzantine consensus and blockchain : Models unification and new protocols Les applications distribuées utilisent des protocoles de consensus afin de maintenir un état consistent sur plusieurs machines dans un réseau. L'avènement récent de bitcoin et des algorithmes basés sur la blockchain a suscité un regain d'intérêt pour ces protocoles, notamment en ce qui concerne leur capacité à passer à l'échelle et à tolérer les participants malicieux. Cependant, cette attention a été source de confusion, submergeant un sujet déjà vaste et complexe avec des assertions imprécises et une terminologie variable. Dans cette thèse, nous proposons une unification des fondamentaux de la blockchain, grâce à un formalisme capturant un large éventail de modèles communs pour les protocoles de consensus. Nous utilisons ce formalisme pour décrire les spécifications de divers protocoles de consensus d'intérêt pour la blockchain. Nous recadrons et précisons les théorèmes qui décrivent les conditions dans lesquelles un protocole est possible ou non. Nous utilisons également notre formalisme pour décrire le modèle de plusieurs blockchains de référence malgré leurs différences fondamentales, et nous pouvons également évaluer et comparer finement leurs caractéristiques de performance. Ensuite, nous faisons une proposition pour une blockchain, StakeCube. La sécurité de StakeCube est basée sur le modèle de preuve d'enjeu (Proof-of-Stake), et sa capacité de passage à l'échelle repose sur un principe du partitionnement (sharding), qui est mis en œuvre par une table de hachage distribuée. Nous avons également implémenté une version restreinte de StakeCube et évalué ses performances, validant ainsi sa propriété de passage à l'échelle. Notamment, comme StakeCube troque la preuve de travail (Proof-of-Work) contre la preuve d'enjeu sans sacrifier le passage à l'échelle, ce protocole est particulièrement bien adapté aux applications IoT. Pour mieux démontrer cet aspect, nous avons implémenté une application IoT de marché d'énergie dans StakeCube et avons pu tester avec succès sa viabilité.
Joachim Neu, Srivatsan Sridhar, Lei Yang, David Tse · 5 authors
Spamming attacks are a serious concern for consensus protocols, as witnessed by recent outages of a major blockchain, Solana. They cause congestion and excessive message delays in a real network due to its bandwidth constraints. In contrast, longest chain (LC), an important family of consensus protocols, has previously only been proven secure assuming an idealized network model in which all messages are delivered within bounded delay. This model-reality mismatch is further aggravated for Proof-of-Stake (PoS) LC where the adversary can spam the network with equivocating blocks. Hence, we extend the network model to capture bandwidth constraints, under which nodes now need to choose carefully which blocks to spend their limited download budget on. To illustrate this point, we show that 'download along the longest header chain', a natural download rule for Proof-of-Work (PoW) LC, is insecure for PoS LC. We propose a simple rule 'download towards the freshest block', formalize two common heuristics 'not downloading equivocations' and 'blocklisting', and prove in a unified framework that PoS LC with any one of these download rules is secure in bandwidth-constrained networks. In experiments, we validate our claims and showcase the behavior of these download rules under attack. By composing multiple instances of a PoS LC protocol with a suitable download rule in parallel, we obtain a PoS consensus protocol that achieves a constant fraction of the network's throughput limit even under worst-case adversarial strategies.
Joachim Neu, Srivatsan Sridhar, Lei Yang, David Tse · 5 authors
Satoshi Nakamoto's Proof-of-Work (PoW) longest chain (LC) protocol was a breakthrough for Internet-scale open-participation consensus. Many Proof-of-Stake (PoS) variants of Nakamoto's protocol such as Ouroboros or Snow White aim to preserve the advantages of LC by mimicking PoW LC closely, while mitigating downsides of PoW by using PoS for Sybil resistance. Previous works have proven these PoS LC protocols secure assuming all network messages are delivered within a bounded delay. However, this assumption is not compatible with PoS when considering bandwidth constraints in the underlying communication network. This is because PoS enables the adversary to reuse block production opportunities and spam the network with equivocating blocks, which is impossible in PoW. The bandwidth constraint necessitates that nodes choose carefully which blocks to spend their limited download budget on. We show that 'download along the longest header chain', a natural download rule for PoW LC, emulated by PoS variants, is insecure for PoS LC. Instead, we propose 'download towards the freshest block' and prove that PoS LC with this download rule is secure in bandwidth constrained networks. Our result can be viewed as a first step towards the co-design of consensus and network layer protocols.
SATHISHKUMAR RANGANATHAN, Muralindran Mariappan, M. Karthigayan
Swarm robotics is an evolving realm that aims to achieve a common goal in coordinated way. But the current communication and control mechanism between the robots is not secure, efficient, capable, and it is more centralized. Blockchain, a decentralized, transparent, and immutable P2P communication technology, is the right fit to pair with swarm robotics. This paper discusses the current challenges in paring blockchain with swarm robotics and the applied methodology for the amalgamation of these futuristic technologies.
The Nervos CKB (Common Knowledge Base) is a public permissionless blockchain designed for the Nervos ecosystem. The CKB consensus protocol is the key protocol of the Nervos CKB, which improves the limit of the consensus’s performance for Bitcoin. In this paper, we developed the formal model of the CKB consensus protocol using timed automata. Based on the model, we formally verified various important properties of the Nervos CKB to provide a sufficient trustworthiness assurance. Especially, the security of the Nervos CKB against the selfish mining attacks to the protocol was investigated.
Eder J. Scheid, Pascal Kiechl, Muriel Figueredo Franco, Bruno Rodrigues · 6 authors
Over the past years, Blockchain (BC) interoperability became a crucial topic of research due to the fast development of new BC platforms for many use-cases, from supply-chain to voting. The need for interoperability can be attributed to the development of such platforms that did not follow any standard, leading to the creation of BC islands that do not exchange data, which hinders innovation. Hence, several BC interoperability solutions were proposed to tackle such problems. One of them is Bifröst, a Notary scheme-based BC interoperability Application Programming Interface (API) that allows the transparent interaction by users or legacy applications with several BCs. An initial prototype of Bifröst was developed, proving its feasibility; however, it did not provide native data encryption or an interaction standard. Thus, this paper presents the design and implementation of an encryption scheme for Bifröst and a JSON format proposal to interact with Bifröst, which also contributes to the state-of-the-art. Evaluations on the encryption scheme show an increase of the data size after the encryption but a constant performance overhead, and discussions on the standard prove that it can be applied to other Notary-based BC interoperability APIs due to its flexibility.
Marco Crosara, Luca Olivieri, Fausto Spoto, Fabio Tagliaferro
Blockchain replicates the execution of transactions in a decentralized network of machines, supporting trust since each machine, by itself, cannot violate the rules for the transactions. Many applications of blockchains are related to the exchange of tokens, ie. valuable units that can be native, such as bitcoin and ether, or implemented in software, through smart contracts. Standards ensure token interoperability among decentralized applications of a certain platform, but they are general enough to be used in other contexts as well. A trend in blockchain is to implement such standards from a platform to another one, easing the design challenges with trusted and widely-used specifications. Exploiting the target language semantic can result in technological advantages with more efficient contracts. This paper presents a re-engineering of OpenZeppelin’s implementation of the ERC-20 standard for fungible tokens on Takamaka, a subset of Java for programming smart contracts in the Hotmoka blockchain. It starts with a literal translation from Solidity to Takamaka, but then describes a novel implementation for making snapshots of tokens, based on tree maps, that is possible in Java, but not in Solidity, and shows that it is much more efficient than the literal translation in Java from Solidity, within the Java Virtual Machine.