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2,085 results · page 65 of 87
Jiahui Zhang, Jingling Zhao, Xuyan Song, Yiping Liu · 5 authors
No abstract is available for this record.
Yizhong Liu, Jianwei Liu, Jiayuan Yin, Geng Li · 6 authors
No abstract is available for this record.
Palanivel Kuppusamy
Blockchain is an emerging technology that serves as an immutable ledger and publicly available infrastructure for building decentralized applications. Blockchain-based applications ensure transparency and trust between all parties involved in the interaction. Nowadays, educational organizations focus on online education and propose to create a system based on educational smart contracts in a public ledger. This public ledger shall be shared between major online and offline educational institutes around the world. From a software architecture perspective, blockchain enables new forms of distributed software architectures across a large network of untrusted participants. The objective of this chapter is to propose a blockchain architecture stack to smart education. The proposed architecture exploits the benefits of the blockchain and global ecosystem simplification to create a globally trusted higher education credit system.
Naoya Okanami, Ryuya Nakamura, Takashi Nishide
Sharding is an approach to designing a highly scalable blockchain. A sharded blockchain achieves parallelism by dividing consensus nodes (validators) into groups called shards and making them process different transactions in each shard. In this paper, we economically analyze users’ behavior on sharded blockchains and identify a phenomenon that users’ accounts and smart contracts eventually get concentrated in a few shards, making shard loads unfair. This phenomenon leads to bad user experiences, such as delays in transaction inclusions and increased transaction fees. To solve the above problem, we propose a load balancing ramework in sharded blockchains in which accounts and contracts are frequently reassigned into shards to reduce the difference of loads between shards. We formulate the contract reassignment as an optimization problem and present the algorithm to solve it. Further, we apply the framework to an existing sharding design (Ethereum 2.0) and modify the protocol to do load balancing. Finally, we simulate the protocol and observe smaller transaction delays and fees.
Sara Ghaemi, Hamzeh Khazaei, Petr Musı́lek
Due to the rapid increase in the total amount of data generated in the world, the need for more computational resources is also increasing dramatically. This trend results in huge data centers and massive server farms being built around the world, which have a negative impact on global carbon emissions. On the other hand, there are many underutilized personal computers around the world that can be used towards distributed computing. To better understand the capacity of personal computers, we have conducted a survey that aims to find their unused computational power. The results indicate that the typical CPU utilization of a personal computer is only 24.5% and, on average, a personal computer is only used 4.5 hours per day. This shows a significant computational potential that can be used towards distributed computing. In this paper, we introduce ChainFaaS with the motivation to use the computational capacity of personal computers as well as to improve developers' experience of internet-based computing services by reducing their costs, enabling transparency, and providing reliability. ChainFaaS is an open, public, blockchain-based serverless platform that takes advantage of personal computers' computational capacity to run serverless tasks. If a substantial number of personal computers were connected to this platform, some tasks could be offloaded from data centers. As a result, the need for building new data centers would be reduced with a positive impact on the environment. We have proposed the design of ChainFaaS, and then implemented and evaluated a prototype of this platform to show its feasibility.
Rahul Katarya, Aamir Mustafa
Blockchain is a publicly distributed ledger system that provides access to all records for everyone participating in the network. All the additions to the block are permanent and unchangeable. All major or minor changes are reported in a new block and cannot be reversed. Since the ledger is being distributed, there is no centralized authority. By eliminating the need for intermediaries, blockchain enables parties to trace transactions quickly and easily. The transactions occurring on a blockchain are transparent, reliable, authenticated and secured with the help of cryptography. The biggest advantage of the distributed ledger of blockchain is reduced operating costs. Blockchain is already being used by companies like IBM, Barclays, and Kodak etc. Blockchain can contain details of transactions for resources other than money such as land, automobiles, agricultural products etc. Any adjustment must be accepted by most people in the network, and this is achieved using Consensus algorithms. This paper discusses some of the core algorithms for consensus used in blockchain systems.
Prasad B. Honnavali, Ajaykumar S. Cholin, Athul Pai, Achuta D. Anekal · 5 authors
No abstract is available for this record.
İrshad Hussaın, Özlem Çakır
Blockchain, which is also called a distributed ledger technology (DLT), is an emerging and ever advancing technology having flourishing potential for nourishing and revolutionizing higher education. It stems in decentralization and distributed learning with characteristics of permanence of records, pursuit and transfer of knowledge, authority of institutions, and reliability of teaching and learning. These characteristics of blockchain attract educational institutions particularly the higher education institutions to adopt it. However, in spite of all potential and benefits of blockchain technology, the higher education stakeholders currently seem to be less aware of the social benefits and educational/instructional potential of blockchain technology. It can be addressed through proper advocacy and campaign. The complete chapter will demonstrate possibilities of blockchain technologies in higher education along with its issues and challenges.
Blaž Podgorelec, Muhamed Turkanović, Martina Šestak
No abstract is available for this record.
Felix Adler, Dennis Kitzmann, Marc Jansen
No abstract is available for this record.
Siwapol Jumnongsaksub
With smart contracts, a wide range of applications can be implemented on blockchains. Ethereum stores smart contract byte code with the smart contract ad-dress so, the Ethereum Virtual Machine (EVM) can read and execute transactions correctly. All executed transactions (both successful and failed transactions) are stored on the platform permanently. Failed transactions are thrown by the EVM due to runtime errors and result in monetary waste. The waste from these transactions add up to around 2 million Ethers or $634.2 million. In this thesis, we propose Evitar, a warning algorithm for reducing Ethereum smart contract runtime errors, which has two mechanisms. First, Evitar proposes that users send transactions with the maximum gas allowed to avoid Out of Gas errors. However, this results in an extremely high transaction fee when transactions fail. Second, Evitar analyzes transactions called to each method in smart contracts and marks a method as a method with a high failure rate if the number of failed transactions reaches Evitar’s threshold. This mechanism prevents users from sending and paying for transactions that are likely to fail. We run experiments to evaluate the performance of Evitar by replaying transactions in a private network. The results show that Evitar can reduce failed transactions up to 99.52% compared to sending under default behaviour in exchange for a reduction in successful transactions by 1.78%. The amount of gas used by Evitar is only one-tenth compared to sending under default behaviour. Sending transactions with the maximum gas in Evitar reduces Out of Gas errors by 99.25%. In addition, Evitar can save up to 15.04 GB (82.32%) of storage in the Geth default node and 50.09 GB (50.09%) in the Parity full archive node.
Nikita Singh, Manu Vardhan
Distributed ledger technology is the driving force behind the blockchain technology and is proving its usefulness in various types of transaction processing systems. Fast, secure, reliable and efficient transactions are the key features of the blockchain based applications. A suitable or optimal size of block used by an application is dependent on the number of transactions in each block. Block size optimization is an important issue for any blockchain based application as it directly affects the performance of the application as scalability bottlenecks could prevent higher throughput and cause congestion. A larger block size will require higher transmission time compared to the smaller block size. A smaller block is more efficient but building too small a block will require higher block composition time to clear all the transactions. Both performance factors are contradictory to each other. An efficient blockchain network requires a suitable block size that demands lesser transmission time and block composition time. This paper proposes meta-heuristic algorithm based techniques for finding the suitable block size. It uses meta-heuristic algorithms to find the optimal number of transaction in each block. These algorithms are multi-objective particle swarm optimization and strength Pareto evolutionary algorithm. Experimental results reveal that the suitable block size is 213 transactions per block. Since size of a transaction is taken as 1.2 Kb, hence the results show that an optimal block size is of 255 Kbytes when network bandwidth of miners varies from 250 kbps to 1200 kbps. This shall achieve lower block transmission time and block composition time.
Marco Zecchini, Andrea Bracciali, Ioannis Chatzigiannakis, Andrea Vitaletti
No abstract is available for this record.
Roman Mühlberger, Stefan Bachhofner, Eduardo Castelló Ferrer, Claudio Di Ciccio · 7 authors
Blockchain has evolved into a platform for decentralized applications, with beneficial properties like high integrity, transparency, and resilience against censorship and tampering. However, blockchains are closed-world systems which do not have access to external state. To overcome this limitation, oracles have been introduced in various forms and for different purposes. However so far common oracle best practices have not been dissected, classified, and studied in their fundamental aspects. In this paper, we address this gap by studying foundational blockchain oracle patterns in two foundational dimensions characterising the oracles: (i) the data flow direction, i.e., inbound and outbound data flow, from the viewpoint of the blockchain; and (ii) the initiator of the data flow, i.e., whether it is push or pull-based communication. We provide a structured description of the four patterns in detail, and discuss an implementation of these patterns based on use cases. On this basis we conduct a quantitative analysis, which results in the insight that the four different patterns are characterized by distinct performance and costs profiles.
Mohammad Tabrez Quasim, Mohammad Ayoub Khan, Fahad Algarni, Abdullah Alharthy · 5 authors
No abstract is available for this record.
Zhen Gao, Dongbin Zhang, Jiuzhi Zhang
No abstract is available for this record.
Mingxiao Du, Qijun Chen, Xiaofeng Ma
Blockchain technology is an emerging distributed ledger technology that has exploratory applications in many areas. The consensus algorithm, as the core module of the blockchain, has an important impact on the security, scalability, and efficiency of the blockchain network. The consensus algorithm is also a popular topic in current blockchain technology research. In existing consortium blockchains and public blockchains, the blockchain has low efficiency or poor fault tolerance because of the limitations of the consensus algorithm. To both ensure the fault tolerance of the blockchain and improve the scalability and throughput, in this paper, we propose a new type of consensus algorithm: mixed Byzantine fault tolerance (MBFT). MBFT uses sharding and layered technology. MBFT functionally partitions the nodes that participate in the consensus process and improves the scalability and efficiency without sacrificing security. MBFT also introduces a random node selection mechanism and a credit mechanism to improve security and fault tolerance. We analyze the security and experiment on transaction throughput in a real network environment. The results prove that MBFT has good security and scalability and high throughput.
I Inghirami
No abstract is available for this record.
Tariq Alsboui, Yongrui Qin, Richard Hill, Hussain Al-Aqrabi
No abstract is available for this record.
Víctor Pérez, Maximiliano Klemen, Pedro López-García, José F. Morales · 5 authors
No abstract is available for this record.
Thomas Genet, Thomas Jensen, Justine Sauvage
Ethereum is a decentralized blockchain technology equipped with so-called Smart Contracts. A contract is a program whose code is public, which can be triggered by any user, and whose actual execution is performed by miners participating in Ethereum. Miners execute the contract on the Ethereum Virtual Machine (EVM) and apply its effect by adding new blocks to the blockchain. A contract that takes too much time to be processed by the miners of the network may result into delays or a denial of service in the Ethereum system. To prevent this scenario, termination of Ethereum's Smart Contracts is ensured using a gas mechanism. Roughly, the EVM consumes gas to process each instruction of a contract and the gas provided to run a contract is limited. This technique could make termination of contracts easy to prove but the way the official definition of the EVM specifies gas usage makes the proof of this property non-trivial. EVM implementations and formal analysis techniques of EVM's Smart Contracts use termination of contracts as an assumption, so having a formal proof of termination of contracts is crucial. This paper presents a mechanized, formal, and general proof of termination of Smart Contracts based on a measure of EVM call stacks.
Kamran Mammadzada, Mubashar Iqbal, Fredrik Milani, Luciano García‐Bañuelos · 5 authors
No abstract is available for this record.
Yibin Xu, Yangyu Huang
The exponential growth of the blockchain size has become a major contributing factor that hinders the decentralisation of blockchain and its potential implementations in data-heavy applications. In this paper, we propose segment blockchain, an approach that segmentises blockchain and enables nodes to only store a copy of one blockchain segment. We use \emph{PoW} as a membership threshold to limit the number of nodes taken by an Adversary---the Adversary can only gain at most $n/2$ of nodes in a network of $n$ nodes when it has $50\%$ of the calculation power in the system (the Nakamoto blockchain security threshold). A segment blockchain system fails when an Adversary stores all copies of a segment, because the Adversary can then leave the system, causing a permanent loss of the segment. We theoretically prove that segment blockchain can sustain a $(AD/n)^m$ failure probability when the Adversary has no more than $AD$ number of nodes and every segment is stored by $m$ number of nodes. The storage requirement is mostly shrunken compared to the traditional design and therefore making the blockchain more suitable for data-heavy applications.
Ralph Ankele, Kai Nahrgang, Branka Stojanović, Atta Badii
No abstract is available for this record.