Follow blockchain research across journals, conferences, and preprint repositories.
2,350 results · page 81 of 98
Abdenaby Lamiri, Kamal Gueraoui, Gamal Zeggwagh
No abstract is available for this record.
Neville Grech, Michael Kong, Anton Jurisevic, Lexi Brent · 6 authors
Ethereum is a distributed blockchain platform, serving as an ecosystem for smart contracts: full-fledged inter-communicating programs that capture the transaction logic of an account. Unlike programs in mainstream languages, a gas limit restricts the execution of an Ethereum smart contract: execution proceeds as long as gas is available. Thus, gas is a valuable resource that can be manipulated by an attacker to provoke unwanted behavior in a victim's smart contract (e.g., wasting or blocking funds of said victim). Gas-focused vulnerabilities exploit undesired behavior when a contract (directly or through other interacting contracts) runs out of gas. Such vulnerabilities are among the hardest for programmers to protect against, as out-of-gas behavior may be uncommon in non-attack scenarios and reasoning about it is far from trivial. In this paper, we classify and identify gas-focused vulnerabilities, and present MadMax: a static program analysis technique to automatically detect gas-focused vulnerabilities with very high confidence. Our approach combines a control-flow-analysis-based decompiler and declarative program-structure queries. The combined analysis captures high-level domain-specific concepts (such as "dynamic data structure storage" and "safely resumable loops") and achieves high precision and scalability. MadMax analyzes the entirety of smart contracts in the Ethereum blockchain in just 10 hours (with decompilation timeouts in 8% of the cases) and flags contracts with a (highly volatile) monetary value of over $2.8B as vulnerable. Manual inspection of a sample of flagged contracts shows that 81% of the sampled warnings do indeed lead to vulnerabilities, which we report on in our experiment.
Zaynah Dargaye, Antonella Del Pozzo, Sara Tucci-Piergiovanni
The paper presents Pluralize a formal logical framework able to extend the execution of blockchain transactions to events coming from external oracles, like external time, sensor data, human-made declarations, etc. These events are by essence non-reliable, since transaction execution can be triggered by information whose veracity cannot be established by the blockchain. To overcome this problem, the language features a first-order logic and an authority algebra to allow formal reasoning and establish accountability of agents for blockchain-enabled transactions. We provide an accountability model that allows to formally prove the accountability of agents by a formal proof locally executable by each agent of the blockchain.
Sang‐Min Choi, Jiho Park, Quan Nguyen, André Cronje
We describe \emph{Fantom}, a framework for asynchronous distributed systems. \emph{Fantom} is based on the Lachesis Protocol~\cite{lachesis01}, which uses asynchronous event transmission for practical Byzantine fault tolerance (pBFT) to create a leaderless, scalable, asynchronous Directed Acyclic Graph (DAG). We further optimize the \emph{Lachesis Protocol} by introducing a permission-less network for dynamic participation. Root selection cost is further optimized by the introduction of an n-row flag table, as well as optimizing path selection by introducing domination relationships. We propose an alternative framework for distributed ledgers, based on asynchronous partially ordered sets with logical time ordering instead of blockchains. This paper builds upon the original proposed family of \emph{Lachesis-class} consensus protocols. We formalize our proofs into a model that can be applied to abstract asynchronous distributed system.
Bruno Andriamanalimanana, Chen-Fu Chiang, Jorge Novillo, Sam Sengupta · 5 authors
No abstract is available for this record.
Alan T. Sherman, Farid Javani, Haibin Zhang, Enis Golaszewski
We explore the origins of blockchain technologies to better understand the enduring needs they address. We identify the five key elements of a blockchain, show embodiments of these elements, and examine how these elements come together to yield important properties in selected systems. To facilitate comparing the many variations of blockchains, we also describe the four crucial roles of blockchain participants common to all blockchains. Our historical exploration highlights the 1979 work of David Chaum whose vault system embodies many of the elements of blockchains.
Libo Feng, Hui Zhang, Yong Chen, Liqi Lou
The permissioned blockchain system has recently become popular in a wide range of scenarios, such as artificial intelligence, financial applications and the Internet of things, due to its dominance in terms of distribution, decentralization, reliability and security. However, the Practical Byzantine Fault-Tolerant (PBFT) algorithm, which is currently adopted in such systems, sparks communication bottlenecks when the number of consensus nodes increases sharply, which seriously hinders large-scale applications. In this paper, we propose a scalable dynamic multi-agent hierarchical PBFT algorithm (SDMA-PBFT), which reduces the communication costs from O(n2) to O( n × k × log k n ). Specifically, SDMA-PBFT forms multiple autonomous systems at each agent node in which message multicasting can be efficiently carried out and the internal voting results can be effectively collected. Therefore, the design of these agent nodes facilitates the in-and-out operations of consensus nodes in the blockchain system. Simulation results show that our proposed algorithm substantially outperforms the PBFT algorithm in terms of latency. Hence, it can be applied to the permissioned blockchain system effectively and efficiently.
Lucianna Kiffer, Rajmohan Rajaraman, Abhi Shelat
The celebrated Nakamoto consensus protocol [16] ushered in several new consensus applications including cryptocurrencies. A few recent works [7, 17] have analyzed important properties of blockchains, including most significantly, consistency, which is a guarantee that all honest parties output the same sequence of blocks throughout the execution of the protocol. To establish consistency, the prior analysis of Pass, Seeman and Shelat [17] required a careful counting of certain combinatorial events that was difficult to apply to variations of Nakamoto. The work of Garay, Kiayas, and Leonardas [7] provides another method of analyzing the blockchain under the simplifying assumption that the network was synchronous. The contribution of this paper is the development of a simple Markov-chain based method for analyzing consistency properties of blockchain protocols. The method includes a formal way of stating strong concentration bounds as well as easy ways to concretely compute the bounds. We use our new method to answer a number of basic questions about consistency of blockchains: Our new analysis provides a tighter guarantee on the consistency property of Nakamoto's protocol, including for parameter regimes which [17] could not consider; We analyze a family of delaying attacks first presented in [17], and extend them to other protocols; We analyze how long a participant should wait before considering a high-value transaction "confirmed"; We analyze the consistency of CliqueChain, a variation of the Chainweb [14] system; We provide the first rigorous consistency analysis of GHOST [20] and also analyze a folklore "balancing"-attack. In each case, we use our framework to experimentally analyze the consensus bounds for various network delay parameters and adversarial computing percentages. We hope our techniques enable authors of future blockchain proposals to provide a more rigorous analysis of their schemes.
Shumo Chu, Sophia Wang
Decentralization, which has backed the hyper growth of many blockchains, comes at the cost of scalability. To understand this fundamental limitation, this paper proposes a quantitative measure of blockchain decentralization, and discusses its implications to various trust models and consensus algorithms. Further, we identify the major challenges in blockchain decentralization. Our key findings are that true decentralization is hard to achieve due to the skewed mining power and that a fully decentralized blockchain inherently limits scalability as it incurs a throughput upper bound and prevents scaling smart contract execution. To address these challenges, we outline three research directions to explore the trade-offs between decentralization and scalability.
Xiaolian Chen, Xiao Hu, Yang Li, Xue Gao · 5 authors
Energy Internet provides important support to power transmission and substation distribution links, security is particularly significant. However, access authentication centralized to the certification center has brought great pressure on computing and communications. In this paper, a distributed authentication scheme for the energy Internet is proposed based on the blockchain technology, which is decentralized and undeniable. A PBFT consensus mechanism is implemented with the Shamir threshold secret sharing mechanism. Experiments show that the scheme can effectively improve the concurrent access efficiency of Energy Internet terminals.
Peter Menegay, Jason Salyers, Griffin College
A secure communications infrastructure featuring email, chat, and a MIPR application was developed to a proof of concept level using a blockchain database to store the contents. The blockchain, which already provides a completely secure method of exchanging cryptocurrencies, can be extended to any transactional or communications paradigm. Email applications are described in which application-level standard protocols (e.g. SMTP, POP3, IMAP) were enhanced to optionally allow messages to be routed through a blockchain using familiar client applications such as MS Outlook or Thunderbird. Chat applications are discussed similarly, using the IRC protocol and a custom web-based protocol based on Socket. IO. A MIPR application is also featured where the ability of multiple parties to sign documents and release funds is illustrated. The integrity of the blockchain, inherent in its distributed nature, is discussed along with enhanced software to enable quick recovery from a breach.
Bo Wu, Qi Li, Ke Xu, Ruoyu Li · 5 authors
Internet of Things (IoT) has already been in the period of rapid development and widespread deployment, while it is still vulnerable to various malicious attacks. Security detection before system installation is not enough to ensure that IoT devices are always secure, because newly emerging vulnerabilities can still be exploited to launch attacks. To address this issue, retrospective detection is often required to trace the security status of IoT systems. Unfortunately, existing centralized detection mechanisms cannot easily provide a comprehensive security analysis. In particular, consumers cannot automatically receive security notification whenever a new vulnerability is uncovered. In this paper, we propose a novel blockchain-powered incentive platform, called SmartRetro, that can incentivize and attract more distributed detectors to participate in retrospective vulnerability detection and contribute their detection results. Leveraging smart contracts, consumers in SmartRetro receive automatic security feedback about their installed IoT systems. We perform the security and theoretical analysis to demonstrate that SmartRetro achieves our desirable security goals.We further implement SmartRetro prototype on Ethereum to evaluate its performance. Our experimental results show SmartRetro is technically feasible and economically beneficial.
Bruno Andriamanalimanana, Chen-Fu Chiang, Jorge Novillo, Sam Sengupta · 5 authors
A central problem with distributed ledger technologies involves the latency that must be incurred in processing and verifying transactions to be accepted as permanent records in the ledger. In many applications, high latency is simply not a tolerable aspect of the governance of the ledger. To help reduce latency, we first propose a theoretical pulsed injection protocol then apply innovative inventory theory onto the unverified transactions in the system. To utilize a probabilistic model for the pulsed injection of transactions, we calibrate the optimum pulsed transaction injection batch size to ensure equilibrium and optimal performance of the system.
Kai Zheng, Ying Liu, Chuanyu Dai, Yanli Duan · 5 authors
Now blockchain network is used in many areas such as healthcare, energy trading and so on. However, the research about how to evaluate the performance of the blockchain network is insufficient. In some papers, the performance of blockchain is analyzed by running real blockchain applications. However, the devices and services cost is a burden. In this paper, we aim to use continuous-time Markov chain (CTMC) models to simulate the time response of PBFT (Practical Byzantine Fault Tolerance)-based healthcare blockchain network. Some influencing factors such as replica nodes delay and primary node delay will be analyzed. The simulation results also contribute to the optimization design of blockchain network.
Konrad Wrona, Michał Jarosz
Distributed ledgers and blockchains have been heralded as a new and universally applicable architecture for management of trust. In this article we investigate what are the possible advantages of using distributed ledger technology within the North Atlantic Treaty Organization (NATO) operations and what are possible use cases for such use. We also analyze different types of distributed ledgers proposed in the literature in respect to their applicability in context of federated military operations. Finally, we describe in more detail a specific use case, related to use of blockchain as new approach to implementing trusted binding mechanism for detached labels as stipulated in the NATO Standardization Agreement (STANAG) 4778, which is now undergoing a ratification process within NATO.
Bruno Andriamanalimanana, Chen-Fu Chiang, Jorge Novillo, Sam Sengupta · 5 authors
A central problem with distributed ledger technologies involves the latency that must be incurred in processing and verifying transactions to be accepted as permanent records in the ledger. In many applications, high latency is simply not a tolerable aspect of the governance of the ledger. To help reduce latency, we offer a distributed ledger architecture, Tango, that mimics the Iota-tangle design as articulated by Popov [1] in his seminal paper. A main idea is the introduction of a semi-synchronous transaction entry protocol layer. We model periodic pulsed injections into the evaluation layer from the entry layer.
Parinya Ekparinya, Vincent Gramoli, Guillaume Jourjon
Recent theoretical attacks conjectured the vulnerabilities of mainstream blockchains through simulations or assumption violations. Unfortunately, previous results typically omit both the nature of the network under which the blockchain code runs and whether blockchains are private, consortium or public. In this paper, we study the public Ethereum blockchain as well as a consortium and private blockchains and quantify the feasibility of man-in-the-middle and double spending attacks against them. To this end, we list important properties of the Ethereum public blockchain topology, we deploy VMs with constrained CPU quantum to mimic the top-10 mining pools of Ethereum and we attack them, by first partitionning the network through BGP hijacking or ARP spooling before issuing a Balance Attack to steal coins. Our results demonstrate that attacking Ethereum is remarkably devastating in a consortium or private context as the adversary can multiply her digital assets by 200, 000× in 10 hours through BGP hijacking whereas it would be almost impossible in a public context.
Dylan Yaga, Peter Mell, Nik Roby, Karen Scarfone
Blockchains are tamper evident and tamper resistant digital ledgers implemented in a distributed fashion (i.e., without a central repository) and usually without a central authority (i.e., a bank, company, or government). At their basic level, they enable a community of users to record transactions in a shared ledger within that community, such that under normal operation of the blockchain network no transaction can be changed once published. This document provides a high-level technical overview of blockchain technology. The purpose is to help readers understand how blockchain technology works.
Giulia Fanti, Leonid Kogan, Sewoong Oh, Kathleen Ruan · 6 authors
Proof-of-stake (PoS) is a promising approach for designing efficient blockchains, where block proposers are randomly chosen with probability proportional to their stake. A primary concern with PoS systems is the "rich getting richer" phenomenon, whereby wealthier nodes are more likely to get elected, and hence reap the block reward, making them even wealthier. In this paper, we introduce the notion of equitability, which quantifies how much a proposer can amplify her stake compared to her initial investment. Even with everyone following protocol (i.e., honest behavior), we show that existing methods of allocating block rewards lead to poor equitability, as does initializing systems with small stake pools and/or large rewards relative to the stake pool. We identify a \emph{geometric} reward function, which we prove is maximally equitable over all choices of reward functions under honest behavior and bound the deviation for strategic actions; the proofs involve the study of optimization problems and stochastic dominances of Polya urn processes, and are of independent mathematical interest. These results allow us to provide a systematic framework to choose the parameters of a practical incentive system for PoS cryptocurrencies.
Jonah Brown-Cohen, Arvind Narayanan, Alexandros Psomas, S. Matthew Weinberg
The security of most existing cryptocurrencies is based on a concept called Proof-of-Work, in which users must solve a computationally hard cryptopuzzle to authorize transactions (`one unit of computation, one vote'). This leads to enormous expenditure on hardware and electricity in order to collect the rewards associated with transaction authorization. Proof-of-Stake is an alternative concept that instead selects users to authorize transactions proportional to their wealth (`one coin, one vote'). Some aspects of the two paradigms are the same. For instance, obtaining voting power in Proof-of-Stake has a monetary cost just as in Proof-of-Work: a coin cannot be freely duplicated any more easily than a unit of computation. However some aspects are fundamentally different. In particular, exactly because Proof-of-Stake is wasteless, there is no inherent resource cost to deviating (commonly referred to as the `Nothing-at-Stake' problem). In contrast to prior work, we focus on incentive-driven deviations (any participant will deviate if doing so yields higher revenue) instead of adversarial corruption (an adversary may take over a significant fraction of the network, but the remaining players follow the protocol). The main results of this paper are several formal barriers to designing incentive-compatible proof-of-stake cryptocurrencies (that don't apply to proof-of-work).
Rohit Mital, Jack de La Beaujardiere, Rohan Mital, Marge Cole · 5 authors
With the thrust towards multi-sensor satellite architectures for earth and space exploration, such as constellations and swarms, new technologies are required to enable the transition to this future capability. One of the areas of interest is establishing secure, efficient and prioritized data and command communication pathways among ground and space-based sources for such systems. This paper presents early research results on the potential role, capabilities and value of blockchain usage within constellation and swarm satellite architectures. It demonstrates the use of blockchain's smart contract and distributed ledger capabilities for secure and prioritized multi-sensor satellite collaborative data exchanges, as well as the logging and tracking of command and control events. Adapting and utilizing this emerging technology will aid in addressing technology gaps expected from future constellation flight architectures, such as managing collective computational operations (correlation), dynamic and autonomous observation planning, time-critical events, and provenance tied to ground and space-based autonomous operations and control recordkeeping. In this scenario blockchain is applied in encrypted command transmittal to multiple, yet specific, entities enabling acknowledgement transmittals, performance scalability, and automatic event-based triggering.
Parwat Singh Anjana, Sweta Kumari, Sathya Peri, Sachin Rathor · 5 authors
Blockchain platforms such as Ethereum and several others execute complex transactions in blocks through user-defined scripts known as smart contracts. Normally, a block of the chain consists of multiple transactions of smart contracts which are added by a miner. To append a correct block into the blockchain, miners execute these transactions of smart contracts sequentially. Later the validators serially re-execute the smart contract transactions of the block. If the validators agree with the final state of the block as recorded by the miner, then the block is said to be validated. It is then added to the blockchain using a consensus protocol. In Ethereum and other blockchains that support cryptocurrencies, a miner gets an incentive every time such a valid block successfully added to the blockchain. In most of the current day blockchains the miners and validators execute the smart contract transactions serially. In the current era of multi-core processors, by employing the serial execution of the transactions, the miners and validators fail to utilize the cores properly and as a result, have poor throughput. By adding concurrency to smart contracts execution, we can achieve better efficiency and higher throughput. In this paper, we develop an efficient framework to execute the smart contract transactions concurrently using optimistic Software Transactional Memory systems (STMs). Miners execute smart contract transactions concurrently using multi-threading to generate the final state of blockchain. STM is used to take care of synchronization issues among the transactions and ensure atomicity. Now when the validators also execute the transactions (as a part of validation) concurrently using multi-threading, then the validators may get a different final state depending on the order of execution of conflicting transactions. To avoid this, the miners also generate a block graph of the transactions during the concurrent execution and store it in the block. This graph captures the conflict relations among the transactions and is generated concurrently as the transactions are executed by different threads. The miner proposes a block which consists of set of transactions, block graph, hash of the previous block, and final state of each shared data-objects. Later, the validators re-execute the same smart contract transactions concurrently and deterministically with the help of block graph given by the miner to verify the final state. If the validation is successful then proposed block appended into the blockchain and miner gets incentive otherwise discard the proposed block. We execute the smart contract transactions concurrently using Basic Time stamp Ordering (BTO) and Multi-Version Time stamp Ordering (MVTO) protocols as optimistic STMs. BTO and MVTO miner achieves 3.6x and 3.7x average speedups over serial miner respectively. Along with, BTO and MVTO validator outperform average 40.8x and 47.1x than serial validator respectively.
Parwat Singh Anjana, Sweta Kumari, Sathya Peri, Sachin Rathor · 5 authors
It is commonly believed that blockchain is a revolutionary technology for doing business on the Internet. Blockchain is a decentralized, distributed database or ledger of records. It ensures that the records are tamper-proof but publicly readable. Blockchain platforms such as Ethereum [3] and several others execute complex transactions in blocks through user-defined scripts known as smart contracts. Normally, a block of the chain consists of multiple transactions of smart contracts which are added by a miner. To append a correct block into the blockchain, miners execute these transactions of smart contracts sequentially. Later the validators serially re-execute the smart contract transactions of the block. If the validators agree with final state of the blocks as recorded by the miner, then the block is said to be valid and added to the blockchain using a consensus protocol.
Zhenzhen Jiao, Rui Tian, Dezhong Shang, Hui Ding
Blockchain has received great attention in recent years and motivated innovations in different scenarios. However, many vital issues which affect its performance are still open. For example, it is widely convinced that high level of security and scalability and full decentralization are still impossible to achieve simultaneously. In this paper, we propose Bicomp, a bilayer scalable Nakamoto consensus protocol, which is an approach based on high security and pure decentralized Nakamoto consensus, and with a significant improvement on scalability. In Bicomp, two kinds of blocks are generated, i.e., microblocks for concurrent transaction packaging in network, and macroblocks for leadership competition and chain formation. A leader is elected at beginning of each round by using a macroblock header from proof-of-work. An elected leader then receives and packages multiple microblocks mined by different nodes into one macroblock during its tenure, which results in a bilayer block structure. Such design limits a leader's power and encourages as many nodes as possible to participate in the process of packaging transactions, which promotes the sharding nature of the system. Furthermore, several mechanisms are carefully designed to reduce transaction overlapping and further limit a leader's power, among which a novel transaction diversity based metric is proposed as the second level criteria besides the longest-chain-first principle on selecting a legitimate chain when fork happens. Security issues and potential attacks to Bicomp are extensively discussed and experiments for evaluation are performed. From the experimental results based on 50 nodes all over the world, Bicomp achieves significant improvement on scalability than that of Bitcoin and Ethereum, while the security and decentralization merits are still preserved.