Follow blockchain research across journals, conferences, and preprint repositories.
2,350 results · page 43 of 98
Jayamine Alupotha, Xavier Boyen, Matthew McKague
No abstract is available for this record.
Dongfang Zhao
No abstract is available for this record.
Zheng Xu, Rui Jiang, Peng Zhang, Tun Lu · 5 authors
No abstract is available for this record.
Juzheng Huang, Qiang Tang, Chunhua Su, Na Ruan
No abstract is available for this record.
Lara Mauri, Stelvio Cimato, Ernesto Damiani
No abstract is available for this record.
Nicholas Stifter, Aljosha Judmayer, Philipp Schindler, Edgar Weippl
No abstract is available for this record.
Badr Bellaj, Aafaf Ouaddah, E. Bertin, Noël Crespi · 5 authors
No abstract is available for this record.
Hui Wang, Wenan Tan, Jiakai Wu, Pan Liu
No abstract is available for this record.
Георги Искров
This article discusses a security analysis provided by blockchain technology. The importance of distributed ledger when communicating in equitable distributed networks. This situation can be expressed in the abstract from the point of view of a group of generals from the Byzantine army, stationed at a camp with their troops around an enemy fortress. By communicating only through communications, the generals must agree on a common battle plan. However, one or more of them can be traitors who will try to confuse others. Mathematically, the algorithm is proven to ensure that loyal generals reach an agreement. The byzantine generals' problem is analysed, Byzantine fault tolerance (BFT) and Byzantine agreement problem. Mathematically, the theorem of reaching consensus with M number of compromised nodes is demonstrated while maintaining an acceptable level of Byzantine fault tolerance (BFT).The results of the article can be used practically when constructing a blockchain for exchange of messages in VANET, also in the MQTT data transfer protocol in IoT.
Yuxuan Zuo, Yang Miao, Zhenping Qiang, Fei Dai · 8 authors
No abstract is available for this record.
Bismark Tei Asare, Laurent Nana, Quist-Aphetsi Kester
The classical blockchain developed for the Bitcoin cryptocurrency has evolved since its introduction more than a decade ago. Blockchain exists in different forms for different purposes and operational contexts. There has been a significant growth in the business use cases of blockchain which is based on the unique attributes of the distributed ledger technology. Blockchain provides peer-to-peer distribution of data in a traceable and decentralized architecture that attains data authentication using consensus protocols. Blockchain as a distributed ledger is the fusion of cryptography, peer-to-peer networking technology, distributed system technology, and consensus mechanism to assure information security and digital asset management. Consensus mechanisms are applied to the distributed ledger that operates in a peer-to-peer network where message transmission between peers is validated and stored across all active peers. Reaching an agreement to validate message transmission and maintaining the correctness of the state of data in a network for critical wireless sensor networks have become a necessary requirement for networks that span several subsystems covering a large operational area. Due to the resource constrained nature of the active actors of wireless sensor networks, any cryptographic solution to be adopted must be lightweight and efficient as well. This paper proposes a blockchain-based decentralized mechanism for authentication of node data for storage onto a distributed ledger. The coloured Petri net was used to model and simulate by detailing the critical attributes of the workings of the system that is based on cyber-physical IoT architecture.
Giuseppe Vitto, Alex Biryukov
No abstract is available for this record.
Jianong Li, Xiaodan Tang
No abstract is available for this record.
Ankit Gangwal, Rahul Valluri, Mauro Conti
No abstract is available for this record.
Ayelet Lotem, Sarah Azouvi, Patrick McCorry, Aviv Zohar
Many prominent smart-contract applications such as payment channels, auctions, and voting systems often involve a mechanism in which some party must respond to a challenge or appeal some action within a fixed time limit. This pattern of challenge-response mechanisms poses great risks if during periods of high transaction volume, the network becomes congested. In this case fee market competition can prevent the inclusion of the response in blocks, causing great harm. As a result, responders are allowed long periods to submit their response and overpay in fees. To overcome these problems and improve challenge-response protocols, we suggest a secure mechanism that detects congestion in blocks and adjusts the deadline of the response accordingly. The responder is thus guaranteed a deadline extension should congestion arise. We lay theoretical foundations for congestion signals in blockchains and then proceed to analyze and discuss possible attacks on the mechanism and evaluate its robustness. Our results show that in Ethereum, using short response deadlines as low as 3 hours, the protocol has >99% defense rate from attacks even by miners with up to 33% of the computational power. Using shorter deadlines such as one hour is also possible with a similar defense rate for attackers with up to 27% of the power.
Oded Naor, Idit Keidar
Money transfer is an abstraction that realizes the core of cryptocurrencies. It has been shown that, contrary to common belief, money transfer in the presence of Byzantine faults can be implemented in asynchronous networks and does not require consensus. Nonetheless, existing implementations of money transfer still require a quadratic message complexity per payment, making attempts to scale hard. In common blockchains, such as Bitcoin and Ethereum, this cost is mitigated by payment channels implemented as a second layer on top of the blockchain allowing to make many off-chain payments between two users who share a channel. Such channels require only on-chain transactions for channel opening and closing, while the intermediate payments are done off-chain with constant message complexity. But payment channels in-use today require synchrony; therefore, they are inadequate for asynchronous money transfer systems. In this paper, we provide a series of possibility and impossibility results for payment channels in asynchronous money transfer systems. We first prove a quadratic lower bound on the message complexity of on-chain transfers. Then, we explore two types of payment channels, unidirectional and bidirectional. We define them as shared memory abstractions and prove that in certain cases they can be implemented as a second layer on top of an asynchronous money transfer system whereas in other cases it is impossible.
Gennady Shvachych, Boris Moroz, Андрій Матвійчук, Hanna Sashchuk · 6 authors
No abstract is available for this record.
Sahar Mohajerani, Wolfgang Ahrendt, Martin Fabian
Smart contracts are programs that are stored on a blockchain ledger with code immutable after deployment. Thus, verifying the correct behavior of smart contracts before deployment is vital. This paper demonstrates how a security vulnerability verification in a casino smart contract can be transformed to non-blocking verification. To this end, the contract is first modeled as interacting extended finite state machines (EFSM), with one EFSM for each function. Modeling the security vulnerability as a condition in the EFSM system, non-blocking verification reveals the system to be blocking. Investigating the counterexample produced by the verification shows that a transfer that is refused by its receiver may block the casino so that all remaining funds are forever locked into the contract, thus revealing a severe vulnerability. It is then demonstrated how the same technique can show the absence of this vulnerability, by verifying that the EFSM model of an improved casino contract is indeed non-blocking.
Peifang Ni, Jing Xu
No abstract is available for this record.
Lin Zhang, Brian Lee, Yuansong Qiao
Blockchain is a type of distributed ledger. It is a chain of blocks. Each block contains a series of transactions. Each transaction is for a value transfer or a smart contract execution. The main purpose of the blockchain system is to achieve consensus on transaction sequence without a controller. The transaction processing capability of the blockchain is influenced by the propagation time of a block in the network -- the shorter the block propagation time, the better the transaction processing capability of the blockchain system, and the easier that system can reach consensus. Ethereum is the second-generation blockchain. It supports Turing complete smart contracts. Although many factors will affect the performance of the Ethereum system, the planned future work of the project is to optimise the transaction/block broadcasting process in the Ethereum peer-to-peer network.
Léonard Lys, Maria Potop-Butucaru
Blockchain oracles are systems that connect blockchains with the outside world by interfacing with external data providers. They provide decentralized applications with the external information needed for smart contract execution. In this paper, we focus on decentralized price oracles, which are distributed systems that provide exchange rates of digital assets to smart contracts. They are the cornerstone of the safety of some decentralized finance applications such as stable coins or lending protocols. They consist of a network of nodes called oracles that gather information from off-chain sources such as an exchange market's API and feed it to smart contracts. Among the desired properties of a price oracle system are low latency, availability, and low operating cost. Moreover, they should overcome constraints such as having diverse data sources which is known as the freeloading problem or Byzantine failures. In this paper, we define the distributed price oracle problem and present PoWacle, the first asynchronous decentralized oracle protocol that copes with Byzantine behavior.
Silvia Crafà, Cosimo Laneve
Liquidity is a liveness property of programs managing resources that pinpoints those programs not freezing any resource forever. We consider a simple stateful language whose resources are assets (digital currencies, non fungible tokens, etc.). Then we define a type system that tracks in a symbolic way the input-output behaviour of functions with respect to assets. These types and their composition, which define types of computations, allow us to design two algorithms for liquidity that have different precisions and costs. We also demonstrate the correctness of the algorithms.
Juan A. Garay, Aggelos Kiayias, Yu Shen
No abstract is available for this record.
Wenpin Tang, David D. Yao
We propose and study a new class of polynomial voting rules for a general decentralized decision/consensus system, and more specifically for the proof-of-stake protocol. The main idea, inspired by the Penrose square-root law and the more recent quadratic voting rule, is to differentiate a voter’s voting power and the voter’s share (fraction of the total in the system). We show that, whereas voter shares form a martingale process that converges to a Dirichlet distribution, their voting powers follow a supermartingale process that decays to zero over time. This prevents any voter from controlling the voting process and, thus, enhances security. For both limiting results, we also provide explicit rates of convergence. When the initial total volume of votes (or stakes) is large, we show a phase transition in share stability (or the lack thereof), corresponding to the voter’s initial share relative to the total. We also study the scenario in which trading (of votes/stakes) among the voters is allowed and quantify the level of risk sensitivity (or risk aversion) in three categories, corresponding to the voter’s utility being a supermartingale, a submartingale, and a martingale. For each category, we identify the voter’s best strategy in terms of participation and trading. Funding: W. Tang gratefully acknowledges financial support through the National Science Foundation [Grants DMS-2113779 and DMS-2206038] and through a start-up grant at Columbia University. D. D. Yao’s work is part of a Columbia–City University/Hong Kong collaborative project that is supported by InnoHK Initiative, the Government of Hong Kong Special Administrative Region, and the Laboratory for AI-Powered Financial Technologies.