Blockchain Papers

Trent McConaghy

No abstract is available for this record.

Daniel Hellwig, Arnd Huchzermeier

No abstract is available for this record.

Bingbing Xiao, Chenguang Jin, Zheng Li, Bingnan Zhu · 6 authors

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.

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.

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.

Eduardo Castelló Ferrer, Ernesto Jiménez, José Luis López-Presa, Javier Martín-Rueda

Interest in multirobot systems is rising rapidly both in academia and in industry. The use of multiple robots working in a coordinated way, rather than a single robot, has several advantages in a diverse range of applications. However, few studies have focused on operations in which robots can behave maliciously and alter the outcome of the collective mission. In this article, we present a set of Byzantine Follow The Leader (BFTL) problems, in which a subset of robots in the system shows unintended or inconsistent behavior (i.e., Byzantine robots). In the BFTL problems,leadersdiscover routes from their starting positions to specific destinations and guide thefollowers, whileByzantinerobots try to hinder the leaders and mislead the followers. In this research, blockchain technology is used as a communication tool within multirobot systems, forleadersto broadcast directions to the whole group. We propose algorithms to tackle the BFTL problems, prove their correctness, and validate them in simulated experiments of realistic scenarios. Results show that the proposed algorithms mitigate the impact of Byzantine robots in multirobot systems conducting a BFTL mission. Our analysis provides minimum and maximum boundary calculations for important metrics including number of robots reaching their destination, number of steps taken, and weight requirements of the chain used during the mission. Our results provide a path toward the deployment of byzantine-resistant real-world multirobot systems.

Rathin Chandra Shit, Mrinal Goswami

With the advent of the multi-sensor satellite system architecture, earth and space exploration such as swarms and constellations are feasible. This transition requires novel technologies to achieve future capabilities. In this context, the establishment of prioritized, secure, and efficient command and data communication is essential for space and ground systems. The use of blockchain assures a secure automated network infrastructure. The blockchain has the potential for usage in swarm satellite architectures and constellations. This paper presents the use of blockchain in multi-sensor satellite architecture with its distributed ledger and smart contract capabilities to provide prioritized and secure collaborative satellite systems. The paper further discusses the use of blockchain technology in securing tracking and logging of control events and commands in satellite architecture. The use of blockchain technology addresses the issues of constellation flight architecture, management of computational operation, autonomous observation, time-critical event planning of ground and space autonomous operation of satellite systems.

Søren F. Mortensen

The financial markets industry has for a long time experimented with blockchain technology and developed many use cases which the market participants over many years have tested the technology against. While there have been many projects, the broader adoption of blockchain has yet to materialise in financial markets. Other industries, notably supply chain, have successfully rolled out global blockchain networks and are seeing the benefits of this technology at a larger scale. The failure of many projects has been down to a set of common factors, for example, the lack of a solid business case or the effort required to align consortium partners to a common goal with a new network. The emergence of digital assets and central bank digital currencies (CBDCs) could be seen to be the catalysts for blockchain on a wider scale in financial markets. They have the potential to disrupt financial markets and especially post-trade as we know it today. Almost 80 per cent of central banks are experimenting with CBDC, and it is just a matter of time before this goes mainstream. Established financial institutions must adapt to this in order to face the threat from new market entrants, and the ecosystems that are being created or face disintermediation.

Aggelos Kiayias, Ηλίας Κουτσουπιάς, Aikaterini-Panagiota Stouka

Proof-of-Stake (PoS) blockchain systems, especially those that allow stakeholders to organize themselves in “stake-pools”, have emerged as a compelling paradigm for the deployment of large scale distributed ledgers. A stake-pool operates a node that engages in the PoS protocol and potentially represents a large number of smaller stakeholders. While such pooled PoS operation is attractive from various angles, it also exhibits a significant shortcoming that, so far and to the best of our knowledge, has not been sufficiently understood or investigated. Pooled PoS operation, to be effective and not lead to sub-optimal dictatorial or cartel-like configurations, should enable the stakeholders to revoke and re-delegate their stake in a way that is aligned with their incentives. However, given that stake-pool operators are exactly those entities who determine what transactions are to be recorded in the ledger, they are quite likely to form a cartel and censor any transaction they want, such as those that attempt to adjust the current stake-pool lineup. In this way, a power grab takes place, where the stake-pool cartel perpetuates its control over the PoS system. We first model and observe formally the emergence of the above problem in pooled PoS systems. Then, we describe an anti-censorship mechanism that takes advantage of the underlying cryptographic functions of the ledger and the nature of peer-to-peer networks to diffuse information without suppression. Specifically, the mechanism exploits digital signatures which can endorse messages that are censored and bind them to delegation transactions, as well as the ability of the underlying ledger to produce unpredictable randomness which can be used to randomly “audit” the suitability of a stake-pool by forcibly expiring it. Upon such expiration, members can evaluate their membership taking into account what information is available, including information potentially not recorded in the ledger but diffused in the peer-to-peer network. We provide a thorough game-theoretic analysis of this mechanism discovering various types of Nash equilibria which demonstrate that the “revolution”, i.e., the strategic decision of pool members to withdraw support from a censoring cartel as well as the pool operators to step down, can be incentivized, under suitable and plausible conditions in the utility functions of the involved participants.

Guillermo Angeris, Akshay Agrawal, Alex Evans, Tarun Chitra · 5 authors

The rise of Ethereum and other blockchains that support smart contracts has led to the creation of decentralized exchanges (DEXs), such as Uniswap, Balancer, Curve, mStable, and SushiSwap, which enable agents to trade cryptocurrencies without trusting a centralized authority. While traditional exchanges use order books to match and execute trades, DEXs are typically organized as constant function market makers (CFMMs). CFMMs accept and reject proposed trades based on the evaluation of a function that depends on the proposed trade and the current reserves of the DEX. For trades that involve only two assets, CFMMs are easy to understand, via two functions that give the quantity of one asset that must be tendered to receive a given quantity of the other, and vice versa. When more than two assets are being exchanged, it is harder to understand the landscape of possible trades. We observe that various problems of choosing a multi-asset trade can be formulated as convex optimization problems, and can therefore be reliably and efficiently solved.

Artem Barger, Yacov Manevich, Hagar Meir, Yoav Tock

Hyperledger Fabric is an enterprise grade permissioned distributed ledger platform that offers modularity for a broad set of industry use cases. One modular component is a pluggable ordering service that establishes consensus on the order of transactions and batches them into blocks. However, as of the time of this writing, there is no production grade Byzantine Fault-Tolerant (BFT) ordering service for Fabric, with the latest version (v2.3) supporting only Crash Fault-Tolerance (CFT).In this work we describe the design and implementation of a BFT ordering service for Fabric, employing a new BFT consensus library. The new library, based on the BFT-SMART protocol and written in Go, is tailored to the blockchain use-case, yet is general enough to cater to a wide variety of other uses. The BFT library's design and integration into Fabric address crucial aspects that were left unsolved in all prior work, making them unfit for production use. We evaluate the new BFT ordering service by comparing it with the currently supported Raft-based CFT ordering service in Hyperledger Fabric.

Vijay A. Kanade

The research proposal discloses a novel drone-based ad-hoc network that leverages acoustic information for power plant surveillance and utilizes a secure blockchain model for protecting the integrity of drone communication over the network. The paper presents a vision for the drone-based networks, wherein drones are employed for monitoring the complex power plant machinery. The drones record acoustic information generated by the power plants and detect anomalies or deviations in machine behavior based on collected acoustic data. The drones are linked to distributed network of computing devices in possession with the plant stakeholders, wherein each computing device maintains a chain of data blocks. The chain of data blocks represents one or more transactions associated with power plants, wherein transactions are related to high risk auditory data set accessed by the drones in an event of anomaly or machine failure. The computing devices add at least one data block to the chain of data blocks in response to valid transaction data, wherein the transaction data is validated by the computing devices owned by power plant personnel.

Jayapriya Jayabalan, N. Jeyanthi

In a Blockchain network multiple nodes across the network verify each transaction and preserve them without having a centralized authority. Verification and insertion of transactions are achieved through distributed cryptographic mechanism called consensus protocol. Consensus protocol involves the application of reputable concepts like Distributed Computing (P2P Networks), Cryptography and consensus algorithms. Traditional motivation for application of Consensus Protocols is to warrant reliability in the distributed systems. The basic assumption behind this protocol is, a `value' must have been proposed by some truthful node in the distributed system. Distributed consensus is attained once all the nodes present in the system agrees and approves the same value. At any given time, all nodes have a sequence of block of transactions, they have already reached consensus on. Also each node has a set of outstanding transactions it has heard about from other nodes. This consensus is achieved via various algorithms which serve as the backbone for Blockchain architecture. Once the transactions are verified, they will be included in the existing chain. The main advantage of such systems is the fact that they are immutable, transparent and distributed. Though stated simple, reaching consensus may be difficult due to various reasons such as crash of active node, presence of malicious nodes, faults in the network, latency (no global time) and not all pairs may be connected. A consensus algorithm ensures that the one and only version of truth gets added into the network, in addition to keeping malevolent people from tampering the network. It also makes sure that the system is fully decentralized. If everyone in the network is strictly honest, there is no need of consensus, however the probability of such existence is very less. Hence, we are undeniably in need of virtuous consensus algorithms for a strong, immortal Blockchain network. The process of selection and enactment of the suitable and right consensus protocol is the key for efficacious Blockchain network. This paper describes about distributed consensus and various algorithms which may be applied for implementation of a Blockchain network.

Xiao Shu, Bo Ding, Jie Luo, Xiang Fu · 6 authors

No abstract is available for this record.

Фариза Тебуева, Sergey Ryabtsev, Igor Struchkov

The active introduction of robotics swarm systems into life brings the issues of their information security up to date. Known security approaches often do not take into account the peculiarities of the implementation of swarm systems, such as collective design-making, and only consider the presence of Byzantine robots with a strategy of behavior consisting in voting against a majority when a consensus is reached. The aim of this work is to increase the security of the collective design-making process in a swarm robotics system from the imposition of false and ineffective alternatives by Byzantine robots with a random behavior strategy. It is proposed to use an approach based on the use of a distributed ledger and analysis of deviations in the process of collective design-making, which will allow identifying and isolating harmful effects. The solution to the problem of detecting Byzantine robots is based on the application of the criterion of the degree of confidence of a robot in choosing an alternative when a consensus is reached by the swarm system and is based on the assumption that the distribution of the degree of confidence of a Byzantine robot due to ignoring the parameters of the external environment and voting for random alternatives is significantly different from the behavior an ordinary robot. The elements of novelty of the presented solution include the use of the degree of confidence criterion to ensure the safety of collective design-making and the ability to take into account various strategies of behavior of Byzantine robots. The use of the presented solution makes it possible to increase the efficiency of reaching consensus by a swarm robotics system in the presence of Byzantine robots. The simulation for a swarm of 20 robots, including 5 Byzantine ones with random behavior, showed an increase in the probability of correctly reaching a consensus by 12.5%. The practical significance of the presented solutions lies in the possibility of ensuring the stability of reaching consensus by a swarm robotics system in the presence of robots with harmful behavior.

Florian Jacob, Carolin Beer, Norbert Henze, Hannes Hartenstein

Matrix is a new kind of decentralized, topic-based publish-subscribe middleware for communication and data storage that is getting particularly popular as a basis for secure instant messaging. By comparison with traditional decentralized communication systems, Matrix replaces pure message passing with a replicated data structure. This data structure, which we extract and call the Matrix Event Graph (MEG), depicts the causal history of messages. We show that this MEG represents an interesting and important replicated data type for decentralized applications that are based on causal histories of publish-subscribe events: First, we prove that the MEG is a Conflict-Free Replicated Data Type for causal histories and, thus, provides Strong Eventual Consistency (SEC). With SEC being among the best known achievable trade-offs in the scope of the well-known CAP theorem, the MEG provides a powerful consistency guarantee while being available during network partition. Second, we discuss the implications of byzantine attackers on the data type's properties. We note that the MEG, as it does not strive for consensus or strong consistency, can cope with n > f environments with n participants, of which f are byzantine. Furthermore, we analyze scalability: Using Markov chains, we study the number of forward extremities of the MEG over time and observe an almost optimal evolution. We conjecture that this property is inherent to the underlying spatially inhomogeneous random walk. With the properties shown, a MEG represents a promising element in the set of data structures for decentralized applications, but with distinct trade-offs compared to traditional blockchains and distributed ledger technologies.

Irvin Steve Cardenas, John Brian May, Jonghoon Kim

No abstract is available for this record.

Ümit Cali, Murat Kuzlu, Manisa Pipattanasomporn, James Kempf · 5 authors

No abstract is available for this record.

Vitor N. Coelho, Rodolfo Pereira Araújo, Haroldo Gambini Santos, Wang Yong Qiang · 5 authors

Mixed-integer mathematical programming has been widely used to model and solve challenging optimization problems. One interesting feature of this technique is the ability to prove the optimality of the achieved solution, for many practical scenarios where a linear programming model can be devised. This paper explores its use to model very strong Byzantine adversaries, in the context of distributed consensus systems. In particular, we apply the proposed technique to find challenging adversarial conditions on a state-of-the-art blockchain consensus: the Neo dBFT. Neo Blockchain has been using the dBFT algorithm since its foundation, but, due to the complexity of the algorithm, it is challenging to devise definitive algebraic proofs that guarantee safety/liveness of the system (and adjust for every change proposed by the community). Core developers have to manually devise and explore possible adversarial attacks scenarios as an exhaustive task. The proposed multi-objective model is intended to assist the search of possible faulty scenario, which includes three objective functions that can be combined as a maximization problem for testing one-block finality or a minimization problem for ensuring liveness. Automated graphics help developers to visually observe attack conditions and to quickly find a solution. This paper proposes an exact adversarial model that explores current limits for practical blockchain consensus applications such as dBFT, with ideas that can also be extended to other decentralized ledger technologies.

Gökay Saldamlı, Ardalan Razavi, Lo’ai Tawalbeh

Current swarm robotics systems are not utilized as frequently in surveillance missions due to the limitations of the existing distributed systems' designs. The main limitation of swarm robotics is the absence of a framework for robots to be self-governing, secure, and scalable. As of today, a swarm of robots is not able to communicate and perform tasks in transparent and autonomous ways. Many believe blockchain is the imminent future of distributed autonomous systems. A blockchain is a system of computers that stores and distributes data among all participants. Every single participant is a validator and protector of the data in the blockchain system. The data cannot be modified since all participants are storing and watching the exact same records. In this study, we will focus on blockchain applications in swarm robotics using Ethereum smart contracts because blockchain can make a swarm globally connected and secure. A decentralized application (DApp) is used to deploy surveillance missions. After mission deployment, the swarm uses blockchain to communicate and make decisions on appropriate tasks within Ethereum private networks. We conclude that, although blockchain enables a swarm to be globally connected and secure, there are performance limitations that can become a critical issue.

Kosuke Toda, Naomi Kuze, Toshimitsu Ushio

It is an important decision-making problem for a miner in the blockchain networks if he/she participates in the mining so that he/she earns a reward by creating a new block earlier than other miners. We formulate this decision-making problem as a noncooperative game, because the probability of creating a block depends not only on one's own available computational resources, but also those of other miners. Through theoretical and numerical analyses, we show a hysteresis phenomenon of Nash equilibria depending on the reward and a jump phenomenon of miner decisions by a slight change in reward. We also show that the reward for which miners decide not to participate in the mining becomes smaller as the number of miners increases.

Samar Al-Saqqa, Sufyan Almajali

<p class="0abstract">One of the new promising technologies for the future is blockchain. It has become one of the popular techniques for various transactions and applications in many different areas such as economy, business, and government. Blockchain technology started with cryptocurrency and bitcoin applications for a safe and transparent environment. Blockchain is a hybrid technology that incorporates various technologies and tools such as mathematics, peer-peer networking, cryptography algorithms, and consensus algorithms. This survey highlights the latest studies in blockchain and consensus algorithms. The study covers the most recent blockchain applications in various domains and sectors. Furthermore, the study gives an insight into the latest adoption of the blockchain in the real world.</p>

Leemon C. Baird, Atul Luykx

Atomic broadcast protocols are increasingly used to build distributed ledgers. The most robust protocols achieve byzantine fault tolerance (BFT) and operate in asynchronous networks. Recent proposals such as HoneyBadgerBFT (ACM CCS `16) and BEAT (ACM CCS `18) achieve optimal communication complexity, growing linearly as a function of the number of nodes present. Although asymptotically optimal, their practical performance precludes their use in demanding applications. Further performance improvements to HoneyBadgerBFT and BEAT are not obvious as they run two separate sub-protocols for broadcast and voting, each of which has already been optimized. We describe how hashgraph - an asynchronous BFT atomic broadcast protocol (ABFT) - departs in structure from prior work by not using communication to vote, only to broadcast transactions. We perform an extensive empirical study to understand how hashgraph's structure affects performance. We observe that hashgraph can improve latency by an order of magnitude over HoneyBadgerBFT and BEAT, while keeping throughput constant with the same number of nodes; similarly, throughput can increase by up to an order of magnitude while maintaining latency. Furthermore, we test hashgraph's capability for high performance, and conclude that it can achieve sufficiently high throughput and low latency to support demanding practical applications.