The incumbent sharding schemes usually assign the nodes to different committees randomly to meet the demands of security and efficiency at the same time. For example, Elastico protocol obtains a random value by letting the node perform proof of work, and then uses this value for sharding. However, the strategy of random sharding ignores the objective differences between nodes, causing performance gaps between different committees in blockchain. This creates a bottleneck in the transaction throughput of the blockchain. In the paper, we propose a node rating based sharding scheme for blockchain system called NRSS. The key idea of NRSS is to evaluate nodes in the network by both the speeds and results of transactions verification before, and then assign them into different committees by balancing the score to reduce the performance gap between committees and increase the speed of transaction process. We implement NRSS in a local blockchain system, and the experiment results show that NRSS can increase the sharding effect of a blockchain, with an average throughput increase of 32.2% in the simulation environment where the node performance difference is up to 75%, depending on the number of nodes in the committee that are preset in the blockchain.
Asynchronous rumor spreading, or epidemic algorithms, are a class of data dissemination protocols that have been used throughout the years for a large variety of distributed applications. The emergence of large-scale, public blockchains, such as Bitcoin and Ethereum, has reinvigorated research interest in these protocols as they are employed to disseminate pending transactions and confirmed blocks in their peer-to-peer (P2P) networks. Efficient, timely and fault-tolerant information dissemination is vital for blockchain networks as it affects issues ranging from security to block finality. Recent works have analyzed the structural properties of blockchain network overlay graphs. Their findings show that they have inherent similarities to those of social networks, such as power-law degree distributions, small diameters and star-like communities. In this work, we present an experimental analysis of the vanilla asynchronous push & pull rumor spreading protocol that is employed by public blockchains. This protocol, although robust and scalable, can be substantially improved. We demonstrate this by analyzing the effect that multiple parameters have on the protocol's performance, such as using memory to avoid contacting the same neighbor twice in a row, varying the stopping criteria of nodes to decide when to stop spreading the rumor, employing more sophisticated neighbor selection policies instead of the standard uniform random choice and others. Prior works have focused on either providing theoretical upper bounds on the number of rounds needed to spread the rumor to all nodes, or, propose improvements by adjusting isolated parameters. To our knowledge, our work is the first to study how multiple parameters affect the protocol's behavior both in isolation and combination and under a wide range of values. Moreover, prior theoretical works have studied rumor spreading only on bidirectional social topologies. Our study examines the behavior of the protocol in multiple topology classes. These include bidirectional, directed, and also a special type of social topologies, called signed topologies, which resemble more closely the topologies of blockchain P2P networks. Our work is the first to indicate and deal with how chains of communities that are sparsely connected to the core of the network can hamper the rumor's spreading. Thus, we complement prior theoretical work to shed light on how the protocol behaves in practical, real-world, large scale distributed systems. Finally, through our detailed analysis, we demonstrate how a few simple additions to the protocol deliver a percentage decrease of the time required to inform all nodes by a maximum of 99.69% and an average of 86.04%.
Blockchain, the concept from Bitcoin created by Satoshi Nakamoto, has the potential to decentralise traditionally centralised systems. Blockchain is a distributed ledger for recording information, stored by many nodes without a central organization through distributed systems and cryptography. The consensus algorithm is a protocol that guarantees the consistency of all data in a blockchain system. It is a key for building a blockchain system and an important part that affects the performance of the blockchain system. In this paper, we firstly compare the usage scenarios of different consensus algorithms, their advantages and disadvantages. After that, we present a new consensus algorithm in permissioned blockchain based on consistent hashing. For blockchain system construction, we propose a new design of the hash ring. The pseudo-randomness of the hash operation is used to ensure the randomness of the electoral leadership node in the blockchain system. It avoids the security risk of the fixed leadership node model. Our algorithm is applicable to blockchain systems containing Byzantine nodes and has a high throughput, low delay and many other advantages. Its communication complexity is O(n), significantly better than that of the practical Byzantine fault tolerance algorithm whose communication complexity is O(n2).
This paper proposes a decentralized solution for web hosting based on interplanetary file system (IPFS) and Ethereum blockchain. Particularly, we use Ethereum smart contracts to manage the IPFS network and the web hosting service. IPFS platform is used to store data and to host websites. All storage miner nodes on the IPFS network offer the pinning service to ensure that source codes of the websites and users' data are retained long-term. Moreover, these nodes also enable the interplanetary name space (IPNS) service for creating and updating mutable links to IPFS contents. TXT record is also used in the domain name system (DNS) to map domain names to IPNS addresses for hosted websites. For privacy-preserving data storage, websites need to be deployed an encryption algorithm. The proposed model that combines between the IPFS and blockchain networks to form a platform providing the decentralized web hosting service. Experiment illustrates building and hosting a web application on the IPFS network. Experimental results show that, compared to the traditional web hosting model, the hosted web application on the proposed platform ensures the confidentiality, integrity, and availability.
With the development of blockchain, more and more blockchain types emerge: public blockchain, consortium blockchain and private blockchain. Because of the node trust in some consortium blockchain and private blockchain, a no byzantine fault tolerance algorithm KRaft(Kademlia-Raft) algorithm with high throughput and high scalability is proposed. KRaft consensus algorithm is a Raft-like consensus algorithm that preserves the logic of part of Raft consensus algorithm. It optimized leader election and consensus process of the Raft consensus algorithm through the established K-Bucket node relationships in the Kademlia protocol, improved leader election speed and throughput. Firstly, the KRaft algorithm uses the K-bucket established by Kademlia protocol to achieve stable and efficient leader election process for the candidate node split vote problem and the low voting efficiency caused by the increase of the Follower node in the Raft algorithm. Secondly, aiming at the low efficiency and load imbalance of the leader single-node log replication in the Raft algorithm consensus process, a parallel log replication scheme with multiple candidate nodes for balancing the leader node load is proposed to improve the throughput and the scalability of the algorithm. Finally, as a Raft-like consensus algorithm, KRaft consensus algorithm satisfied the safety and liveness requirements of Raft consensus algorithm. KRaft consensus algorithm and Raft consensus algorithm were evaluated with local cluster simulation. The experimental results show that the KRaft consensus algorithm has a 41% improvement in transaction throughput and has a 67% improvement in the leader election speed.
The massive spread of harmful content on the internet is hard to filter. Meanwhile, blacklist content filtering cannot keep up with the rapid growth of content creations. As a result, an extra protection layer is required to provide a safe internet for children. However, implementing a network or application firewall requires an expert's knowledge and complicated maintenance. In this paper, we proposed a framework to automate internet protection by using whitelist packet filtering. We use the blockchain smart contract as the secure collaboration media to determine the filtering rules. Meanwhile, the SDN controller automates the packet filtering by installing the determined forwarding rules into the network switches. We evaluate the whitelist packet filtering by using Mininet for the network emulation and Ethereum Rinkeby networks for the smart contract implementation. The result shows that the proposed whitelist system can filter the packet without incurring significant latency. It supports fast content update with a maximum speed of ≈ 1200 valid contents per-minute by using a three-votes verification system.
Distributed consensus mechanisms have been widely researched and made popular with a number of blockchain-based token applications, such as Bitcoin, and Ethereum. Although these general-purpose platforms have matured for scale and security, they are designed for human incentive and continue to require currency reward and contract functions that are not requisite in machine communications. Redes Chain is a custom designed blockchain, built to support fully decentralized self-organization in wireless networks-without a cryptocurrency or contract dependency.
Since Bitcoin was first introduced i n 2008, many types of cryptocurrencies have been proposed based on blockchain. However, the performance of permissionless blockchains restricts the widespread of cryptocurrency. Recently, Libra was proposed by Facebook based on a permissioned blockchain, i.e. the Libra blockchain. The vision of Libra is to become a global currency supporting financial a pplications, but it is doubted whether the performance of the Libra blockchain is able to support frequent micropayment scenarios. In this paper, we propose a methodology to evaluate the performance of blockchain platforms and conducted an experimental study on the Libra blockchain. The results show that the Libra blockchain can only process about one thousand transactions per second at most, and the performance drops significantly a s t he number of validators increases. Although it outperforms permissionless blockchain platforms, the performance of the Libra blockchain is still unsatisfactory compared to other permissioned blockchains like Hyperledger Fabric and needs to make effective improvements in order to support global micropayment in the future.
An ideal distributed storage solution must have the ability to provide redundant, reliable, shared and secure access to user data without compromising the ability to scale and descend while maintaining performance. VAULT is an attempt to avert the negatives of the cloud in a local environment using a decentralized methodology. VAULT makes use of individual idle storage space on a network of peer-to-peer nodes which is then provided to an end user to store files in the pooled space. VAULT implements redundancy by the use of Reed-Solomon codes and maps file fragment locations using a blockchain as a distributed ledger. Fragment distribution is optimized using a machine learning approach where node characteristics are used to determine the reliability of each node. The aggregation of above features makes VAULT an ideal solution for corporate environments where consumer hardware and infrastructure is already allocated.
Blockchain is a distributed ledger, characterized by immutability, anonymity and auditability without requiring trust third party. To provide data exchanges to form such ledger, blockchain network enables the dissemination of transactions and blocks to reach the consensus, which mainly consists of attachment strategy and communication strategy. Currently, it is implemented with peer-to-peer overlay network, which, however, suffers from the intrinsic problem of mismatching between traffic flows and underlying network topology. To solve this problem, we employ information-centric networking (ICN) approach to design a decentralized information-centric blockchain network (DIBN), where categories are named to enable the traffic to be decentralized and an any-to-all category dissemination structure (CDS) is established among all the blockchain nodes (BNs) for each category. For the CDS, one BN can efficiently send data to all other BNs aligning the traffic with the underlying network, which overcomes the problem of mismatch. The performance analysis shows that the proposed DIBN can greatly reduce the average path length for data dissemination in blockchain.
Sana Sabah Sabry, Nada Mahdi Kaittan, Israa Majeed
As the Bitcoin keeps increasing in value compared to other cryptocurrencies, more attention has been given to Blockchain Technology (BT) which is the infrastructure behind the Bitcoin, especially on its role in addressing the problems of the classical centralized system. As a digital currency, Bitcoin is dependent on the decentralized cryptographic tools and peer-to-peer system. The digital currency implements a distributed ledger using Blockchain when verifying any type of transaction. In this paper, the aim is to describe how digital currency networks such as Bitcoin provides a “trust-less” platform for users to embark on money transfers without necessarily depending on any central trusted establishments such as payment services or financial institutions. Furthermore, this work comprehensively overviewed the basic principle that underly BT, such as transaction, consensus algorithms, and hashing. This study also provided a novel classification for blockchain types according to their system architecture and consensus strategy. For each type, our contribution was provided with an example which clearly describes the blockchain features and the transaction steps. Our classification intended to help researchers understand and choose the blockchain for their application. The paper ends with the discussion of the differences between each type
Abdulla Chaer, Khaled Salah, Cláudio Lima, Partha Pratim Ray · 5 authors
5G is a revolutionary technology in mobile telecommunications that promises to be 20x faster than today's 4G technology. The novel characteristics of 5G can be exploited to support new business models and services that require seamless interactions among multiple parties that may include mobile operators, enterprises, telecom providers, government regulators, and infrastructure providers. Meanwhile, blockchain technology has evolved as an enabling, disruptive, and transformational technology that has started to be adopted across many industry vertical domains. Blockchain has been increasingly used to register, authenticate and validate assets and transactions, govern interactions, record data and manage the identification among multiple parties, in a trusted, decentralized, and secure manner. In this paper, we discuss and highlight how blockchain can be leveraged for 5G networks. First, an overview of blockchain capabilities as well as smart contracts, decentralized storage and trusted oracles are presented. Second, potential opportunities in which blockchain features are used to enable 5G services are outlined. Third, examples of system integration architecture and sequence flow diagrams to illustrate how blockchain along with other supporting decentralized technologies can support and facilitate such opportunities are discussed. Finally, key challenges and open research problems are identified and discussed.
Amr M. Khalifa, Ayman M. Bahaa-Eldin, Mohamed Sobh
Blockchain as a distributed data structure or ledger is perceived to provide solutions in manifold areas beyond their prominent form of digital currency; they also showed several challenges. As enhancements to the existing blockchain systems are being proposed and developed, alternative underlying data structures were driven to solve some of the challenges facing them whilst maintaining their key ideas. We start by explaining the key concepts of the blockchain as implemented in Bitcoin and Ethereum. From there, we explain the challenges and survey on the alternative data structures along with their consensus mechanisms. We find a generalization in using hash pointers in the alternative data structures and unfold the current research and implementation directions for solutions to the challenges.
Hamid Raza Malik, Ahsan Manzoor, Mika Ylianttila, Madhusanka Liyanage
Smart grids lay the foundation for future communities. Smart homes, smart buildings, smart streets, and smart offices are built when intelligent devices piles on intelligent devices. To reach the maximum capacity, they all must be supported by an intelligent power supply. For optimal and real-time electricity consumption, monitoring and trading, blockchain posses several potential benefits in its application to electricity infrastructure. To analyze the performance of the blockchain-based smart grid, this paper presents a virtual smart grid. A smart grid equipped with smart contracts, capable of executing virtual activities is evaluated and possible strengths and weaknesses are discussed. The paper draws a performance analysis of the blockchain-based smart grid by using the Ethereum and Hyperledger Fabric-based implementations.
The continually rising demand for wireless services and applications in the era of Internet of things (IoT) and artificial intelligence (AI) presents a significant number of unprecedented challenges to existing network structures. To meet the rapid growth need of mobile data services, blockchain radio access network (B-RAN) has emerged as a decentralized, trustworthy radio access paradigm spurred by blockchain technologies. However, many characteristics of B-RAN remain unclear and hard to characterize. In this study, we develop an analytical framework to model B-RAN and provide some basic fundamental analysis. Starting from block generation, we establish a queuing model based on a time-homogeneous Markov chain. From the queuing model, we evaluate the performance of B-RAN with respect to latency and security considerations. By connecting latency and security, we uncover a more comprehensive picture of the achievable performance of B-RAN. Further, we present experimental results via an innovative prototype and validate the proposed model.
Current blockchain systems face the problems of poor scalability, low performance, and high cost. To address the previous bottlenecks, we plan to employ the DAG-based structure as the primary method and propose a concrete model, called 3D-DAG, to improve the scalability. The model consists of two layers: mainchain and sidechain, which separately severs for maintaining the pivot sequence and improving the parallelism. Our expecting results should significantly improve the performance and scalability without compromising the security.
Felix Kohlbrenner, Pezhman Nasirifard, Christian Löbel, Hans‐Arno Jacobsen
Self-driving cars rely on several services to operate, some of which require financial interactions, such as paying for parking spaces or paying for battery charging in the case of the electric vehicles. Providing these services demands the cooperation of several parties and organizations that do not necessarily trust each other. Over the past few years, several blockchain-based services have been introduced to enable users with a safe and secure medium for conducting business in a trustless environment. In this work, we propose a blockchain-based solution to enable vehicles to consume and pay for services.
Chen Chen, Cong Wang, Tie Qiu, Ning Lv · 5 authors
Vehicular named data networking (VNDN) has recently emerged as a novel paradigm to facilitate content-centric data sharing for Internet of Vehicles. However, an information holder can spread fake data to clients for malicious purposes, which may affect the driving decision of the recipient, or even worse, cause traffic congestion and accidents. In this article, we build a data-sharing system that consists of a double-layer blockchain. The nodes at the bottom layer request for service by announcing their requirements in the NDN paradigm. For the upper layer, the nodes submit their demands and supplies to the nearest roadside unit for further matching. We model the balance between the demand and supply as a matching game. To encourage nodes to provide positive services, a reputation management mechanism that combines negative and positive transaction records is proposed. Simulation results verify the validity of our system, and the data-sharing mechanism fosters a secure information interaction in the VNDN.
Yinqiu Liu, Kun Wang, Kai Qian, Miao Du · 5 authors
With the widespread applications of the Internet of Things (IoT), e.g., smart city, business, healthcare, etc., the security of data and devices becomes a major concern. Although blockchain can effectively enhance the network security and achieve fault tolerance, the huge resource consumption and limited performance of data processing restrict its deployments in IoT scenarios. Observing the heterogeneity and resource constraints, we intend to make blockchain accommodate both wimpy and brawny IoT devices. In this article, we present Tornado, a high-performance blockchain system based on space-structured ledger and corresponding algorithms, to enable blockchain in IoT. Specifically, we first design a space-structured chain architecture with novel data structures for promoting the network scalability. To address the huge heterogeneity of IoT, a novel consensus mechanism named collaborative-proof of work is developed. Moreover, we propose the space-structured greedy heaviest-observed subtree (S2GHOST) protocol for improving the resource efficiency of IoT devices. Additionally, a dynamic weight assignment mechanism in S2GHOST contributes to reflect the trustworthiness of data and devices. Extensive experiments demonstrate that Tornado can achieve a maximum throughput of 3464.76 transactions per second. The optimizations of propagation latency and resource efficiency are 68.14% and 30.56%, respectively.
Jae-Yun Kim, Jun-Mo Lee, Yeon-Jae Koo, Sang-Hyeon Park · 5 authors
As ethereum blockchain has become popular, the number of users and transactions has skyrocketed, causing an explosive increase of its data size. As a result, ordinary clients using PCs or smartphones cannot easily bootstrap as a full node, but rely on other full nodes such as the miners to run or verify transactions. This may affect the security of ethereum, so light bootstrapping techniques such as fast sync has been proposed to download only parts of full data, yet the space overhead is still too high. One of the biggest space overhead that cannot easily be reduced is caused by saving the state of all accounts in the block's state trie. Fortunately, we found that more than 90% of accounts are inactive and old transactions are hard to be manipulated. Based on these observations, this paper propose a novel optimization technique called ethanos that can reduce bootstrapping cost by sweeping inactive accounts periodically and by not downloading old transactions. If an inactive account becomes active, ethanos restore its state by running a restoration transaction. Also, ethanos gives incentives for archive nodes to maintain the old transactions for possible re-verification. We implemented ethanos by instrumenting the go-ethereum (geth) client and evaluated with the real 113 million transactions from 14 million accounts between 7M-th and 8M-th blocks in ethereum. Our experimental result shows that ethanos can reduce the size of the account state by half, which, if combined with removing old transactions, may reduce the storage size for bootstrapping to around 1GB. This would be reasonable enough for ordinary clients to bootstrap on their personal devices.