The blockchain is the distributed ledger technology, and the unchangeability is the main feature. However, the scalability is hindered to satisfy the characteristic. Nowadays, there are more and more attempts to put many applications on block-chains, but there are problems in actual use, for example, the low number of processing transactions per second (tps). Since solving these problems can increase the performance of the blockchain and reduce the cost, to solve them is one of the most important issues in the blockchain; And it is called the scalability issue. In this paper, we analyze methods that various attempts to solve it into following categories: On-chain, Off-chain, Side-chain, Child-chain and Inter-chain. We will analyze how these methods in each category work, what their pros and cons are, and finally compare which scalability issue has been resolved and their own features.
Abstract Providing reliable and surreptitious communications is difficult in the presence of adaptive and resourceful state level censors. In this paper we introduce Tithonus, a framework that builds on the Bitcoin blockchain and network to provide censorship-resistant communication mechanisms. In contrast to previous approaches, we do not rely solely on the slow and expensive blockchain consensus mechanism but instead fully exploit Bitcoin’s peer-to-peer gossip protocol. We develop adaptive, fast and cost effective data communication solutions that camouflage client requests into inconspicuous Bitcoin transactions. We propose solutions to securely request and transfer content, with unobservability and censorship resistance, and free, pay-per-access and subscription based payment options. When compared to state-of-the-art Bitcoin writing solutions, Tithonus reduces the cost of transferring data to censored clients by 2 orders of magnitude and increases the goodput by 3 to 5 orders of magnitude. We show that Tithonus client initiated transactions are hard to detect, while server initiated transactions cannot be censored without creating split world problems to the Bit-coin blockchain.
Application of IoT (Internet of Things) is expanding rapidly as internet connects things in our homes and our personal devices and even our body, provides ease, entertainment and comfort to our daily lives. However, as everything personal is connected, security and privacy becomes a major challenge. Blockchain-based IoT can provide a completely trusted and transparent environment with its tamper-resistant data structure, timestamp, data encryption and distributed consensus. Since cryptocurrency is the first application of blockchains, most blockchain mechanisms like Ethereum provides token-based peer-to-peer payment system that allows payment using a custom currency which enables IoT devices to pay or receive token without a third-party inclusion. In this paper we proposed to apply blockchain mechanism to education/discipline of children at home by through token-based parental control in which parent can encourage good behaviors and discourage bad behaviors of children via tokens transferred via blockchain network. Current parental control is implemented in operating systems of smartphones that only prohibits the abuse of smartphone games or inappropriate web sites. However, this token-based parental control pay tokens to children with good behaviors that allow them to play or watch the proper contents as their rewards. Devices at home like television and computer are connected to the blockchain and accessible only when the user have a sufficient amount of tokens. Children are given incentives in term of token by their parents if they do their homework properly or help their parents. Besides that, smart contract feature in Ethereum allows application to be programmed in a blockchain enables monitoring the activities of children through blockchain. This paper introduces the design of the token-based parental control by using smart contract schemes of Ethereum blockchain with a simple smart home setup as a proof of concept.
Off-chain scaling techniques allow mutually distrustful parties to execute a contract locally among themselves instead of on the global blockchain. Parties involved in the transaction maintain a multi-signature fraud-proof off-chain replicated state machine, and only resort to on-chain consensus when absolutely necessary (e.g., when two parties disagree on a state). Off-chain scaling is the only way to support fully scale-out decentralized applications ("dApps") with better privacy and no compromise on the trust and decentralization guarantees. It is the inflection point for blockchain mass adoption, and will be the engine behind all scalable dApps. Celer Network is an Internet-scale, trust-free, and privacy-preserving platform where everyone can quickly build, operate, and use highly scalable dApps. It is not a standalone blockchain but a networked system running on top of existing and future blockchains. It provides unprecedented performance and flexibility through innovation in off-chain scaling techniques and incentive-aligned cryptoeconomics. Celer Network embraces a layered architecture with clean abstractions that enable rapid evolution of each individual component, including a generalized state channel and sidechain suite that supports fast and generic off-chain state transitions; a provably optimal value transfer routing mechanism that achieves an order of magnitude higher throughput compared to state-of-the-art solutions; a powerful development framework and runtime for off-chain applications; and a new cryptoeconomic model that provides network effect, stable liquidity, and high availability for the off-chain ecosystem.
With the rapid development of blockchain technology, blockchain becomes a good platform for execution of smart contracts. However, since smart contracts still have a low performance of transaction processing on blockchain. It can't satisfy real-time requirements in some situations. This paper proposes a parallel smart contract model on blockchain which has a better performance in transaction processing. The challenges with the proposed approach are the implementation of the parallel mode and the solution of synchronization problem of the proposed model. This paper uses multi-thread technology to implement the proposed model where transactions are executed in parallel. Then we propose a transaction splitting algorithm to resolve the synchronization problem. Finally, experimental analysis proves that this parallel model exactly makes a remarkable development of performance in transaction processing.
The Bitcoin protocol is a significant milestone in the history of money. However, its adoption is currently constrained by the transaction limits of the system. As the chief problem of blockchain technology, the scaling issue has attracted many valuable solutions both on-chain and off-chain. In this paper, our goal is to explore the notion of unspent transaction outputs (UTXOs) to propose an augmented Bitcoin protocol that can scale gracefully. Our proposal aims to increase the transaction throughput by partitioning the UTXO space and splitting the blockchain. In addition, a new type of Bitcoin node is introduced to preserve the capability to run validating nodes in low-bandwidth environments, despite the increased transaction throughput.
The success of blockchain as the underlying technology for cryptocurrencies has opened up possibilities for its use in other application domains as well. The main advantages of blockchain for its potential use in other domains are its inherent security mechanisms and immunity to different attacks. A blockchain relies on a consensus method for agreeing on any new data. Most of the consensus methods which are currently used for the blockchain of different cryptocurrencies require high computational power and thus are not apt for resource-constrained systems. In this article, we discuss and survey the various blockchain based consensus methods that are applicable to resource constrained IoT devices and networks. A typical IoT network consists of several devices which have limited computational and communications capabilities. Most often, these devices cannot perform intensive computations and are starved for bandwidth. Therefore, we discuss the possible measures that can be taken to reduce the computational power and convergence time for the underlying consensus methods. We also talk about some of the alternatives to the public blockchain like private blockchain and tangle, along with their potential adoption for IoT networks. Furthermore, we review the existing consensus methods that have been implemented and explore the possibility of utilizing them to realize a blockchain based IoT network. Some of the open research challenges are also put forward.
Despite growing adoption of cryptocurrencies, making fast payments at scale remains a challenge. Payment channel networks (PCNs) such as the Lightning Network have emerged as a viable scaling solution. However, completing payments on PCNs is challenging: payments must be routed on paths with sufficient funds. As payments flow over a single channel (link) in the same direction, the channel eventually becomes depleted and cannot support further payments in that direction; hence, naive routing schemes like shortest-path routing can deplete key payment channels and paralyze the system. Today's PCNs also route payments atomically, worsening the problem. In this paper, we present Spider, a routing solution that "packetizes" transactions and uses a multi-path transport protocol to achieve high-throughput routing in PCNs. Packetization allows Spider to complete even large transactions on low-capacity payment channels over time, while the multi-path congestion control protocol ensures balanced utilization of channels and fairness across flows. Extensive simulations comparing Spider with state-of-the-art approaches shows that Spider requires less than 25% of the funds to successfully route over 95% of transactions on balanced traffic demands, and offloads 4x more transactions onto the PCN on imbalanced demands.
Blockchain is based on a P2P network, supporting decentralized consensus of current cryptocurrencies. Since bitcoin and altcoins all utilize an underlying blockchain, they are therefore greatly affected by the performance of the P2P network. In bitcoin, the miners are engaged in a time-sensitive competition to solve a Proof-of-Work problem to extend the blockchain. This consequently raises a critical problem to minimize the time between the propagation of a winning block and the beginning of the next round of the competition. This paper proposes a method that selects a node's closest neighbors to make messages propagate in the whole network in time. The method measures the distance from a node to its neighbor using transmission latency; thus, the lower the latency, the closer the neighbor. Simulations showed a good rate of decrease in average propagation latency and maximum propagation latency, compared to the classic method. Furthermore, this paper not only proposes the principle of establishing connections based on latency, but also evaluates the influence of the number of simultaneously established connections.
A wide range of services and applications can be improved and/or solved by\nusing distributed ledger technology (DLT). These services and applications have\nwidely varying quality of service (QoS) requirements. However, most existing\nDLT systems do not distinguish different QoS requirements, resulting in\nsignificant performance issues such as poor scalability and high cost. In this\nwork, we present vDLT -- a service-oriented blockchain system with\nvirtualization and decoupled management/control and execution. In vDLT,\nservices and applications are classified into different classes according to\ntheir QoS requirements, including confirmation latency, throughput, cost,\nsecurity, privacy, etc. This is a paradigm shift from the existing\n"blockchain-oriented" DLT systems to next generation "service-oriented" DLT\nsystems. Different QoS requirements are fulfilled by advanced schemes inspired\nby the development of the traditional Internet, including classification,\nqueuing, virtualization, resource allocation and orchestration, and\nhierarchical architecture. In addition, management/control and execution of\nsmart contracts are decoupled to support QoS provisioning, improve\ndecentralization, and facilitate evolution in vDLT. With virtualization,\ndifferent virtual DLT systems with widely varying characteristics can be\ndynamically created and operated to accommodate different services and\napplications.\n
Background/Objectives: The blockchain has been applied to many fields. Users are concerned about its security. The primary goal of this study is supporting the security service to protect DDoS attack.Methods/Statistical analysis: To provide security service in the blockchain, the security model is suggested. This model can filter out illegitimate traffic and exchange information with other security switches to determine whether a connected node is a normal node or an abnormal node. Each procedure of the proposed model has been described. Also, two different attack types are used to show the operation process of suggested model.Findings: Cyberattacks attempting to impact technology services availability continue to increase. Thus, DDoS is one of the most common type of attacks can also cause the most disruption to internet services. But blockchain has the characteristics of decentralization and peer to peer. This makes it harder to disrupt than conventional distributed application. Nevertheless, DDoS attacks remain a persistent threat. Therefore, a security model is suggested which can effectively block and respond to DDoS attacks.Improvements/Applications: The suggested model makes it possible to protect the spam transaction attacks in blockchain network.
In this work, we propose using edge computing and caching to enhance wireless communications in terms of bandwidth and delay by leveraging concept of mobile 3C systems (communications, computing, and caching). First we argue that without leveraging concepts of edge computing and caching, the huge burden of data transmission and processing necessary for smart city applications and concept is going to exhaust the current wireless infrastructure. Then we demonstrate the need to merge edge computing with caching to enhance wireless communication needed for massive data collection in smart cities. To address the security concerns of using IoT in smart cities, we propose using a blockchain database to secure communication between the smart city and home devices and sensors. This will provide the scalability that is necessary for data transfer between the massive number of nodes in IoT that current security protocols do not provide.
Panayiotis Christodoulou, Klitos Christodoulou, Andreas S. Andreou
A prototypical smart contract (wrapped as a decentralized application) is presented for investigating the potential benefits for applying Blockchain for Logistics. The decentralized application proposed exposes the various design challenges that programmers are likely to face when realizing the implementation of the application. The proposed methodology utilises the implementation of a dedicated smart contract that was developed based on a special-purpose structure for satisfying the requirements of the usecase. The evaluation was based on the execution of each of the functions measuring the gas costs and execution time. The prototype design was deployed and evaluated on a real-world Blockchain framework and can be considered as a first solution to how the Blockchain technology can be utilized within Logistics to overcome any barriers that may exist between professionals. In this paper we present a real implementation of a smart contract for the Logistics industry. The proposed dApp provides a live example of how Blockchain can be utilized within Logistics as it enables users to send and track products.
Micael Ferreira, Sven Rodrigues, Catarina I. Reis, Marisa Maximiano
Bitcoin continues to get more and more attention from the media, mainly because of the volatility of its value and insignificantly associated with the technological innovation. This cryptocurrency is supported by an immutable database and is distributed throughout a network of thousands of nodes, known as Blockchain. One way to ensure that all the concepts behind the Blockchain technology and infrastructure are seized is to conduct the development of one of the most popular context applications for it: a wallet for well-known cryptocurrencies. Yet Another Bitcoin Wallet (YABW) is a hybrid application available for both Android and iOS, which was developed with the Ionic and Angular frameworks. This application communicates with Bitcoin Blockchain to send, receive and store bitcoins; provides a set of features focused on security and user experience, and is available on the Play Store and Apple Store. A rather relevant issue that is becoming a major subject of current research is the application of the Blockchain infrastructure to other contexts that are neither directly connected to cryptocurrencies, nor are finance related. The implementation of a proof-of-concept application proposes the use of a blockchain for a specific case study: the exchange of meal vouchers of an institution amongst students. This is achieved using the decentralized platform Ethereum, which allows us to create a Smart Contract using the Solidity programming language to create a token that follows the Ethereum Request for Comment (ERC), the ERC-20 standard and represents the meal vouchers. This second application uses the architecture defined for YABW, reusing major components and custom developing specific modules to enhance the required features. There is still a lot of research to be done on the non-financial applicability of the Blockchain infrastructure and technology, but for the moment, we have left further evidence that it is possible and is a relative straight-forward process to accomplish from the technological perspective.
The rise of popular cryptocurrencies like Bitcoin and Ethereum has increased the popularity of blockchain technology, the framework these cryptocurrencies are built upon. The security and access control that blockchain technology has provided for cryptocurrencies has peaked the curiosity of other industries, realizing its potential value and future outlook. In this paper, we analyze two types of blockchains, permission-ed and permission-less, and introduce a two-tier blockchain concept utilizing both types for secure data sharing. We provide background on the consensus algorithms used for each blockchain type, Proof-of-Work and Proof-of-Authority. Testing on both Mac OS and Ubuntu Linux-based system environments, preliminary results show that by increasing the number of miners in a Proof-of-Work consensus, there is a correlating increase in the total block count in a permission-less blockchain, where the rate of increase is dependent on the system environment. In the Proof-of-Authority permission-ed blockchain, the block count observed little to no change across both environments.
In this paper we use the blockchain technology to develop a peer to peer energy trade platform without a trusted third party. Our main contribution is a novel distributed double auction mechanism which allows any peer to act as an auctioneer and the blockchain mechanism ensures that a peer behaves lawfully while acting as an auctioneer. Using experimental evaluation we show that (1) the distributed auction converges quickly, (2) it minimizes energy loss due to long transmission, (3) computational overhead due to employing a blockchain is negligible, (4) it is efficient and (5) it can implement trade restrictions imposed by the energy distribution network.
Evolving networking scenarios include multi-administrative domain network services as drivers of novel business opportunities along with emerging operational challenges. As a potential approach to tackle upcoming requirements providing basic primitives to encompass analytics, automation, and distributed orchestration, we investigate blockchain-based decentralized applications (DApps) in the context of operational phases in support of multi-administrative domain networking. We present and discuss a generalized framework for multi-domain service orchestration using blockchain-based DApps and then showcase proof-of-concept prototype experiments based on best of breed open source components that demonstrate DApp functionalities as candidate enablers of multi-domain network services. We then analyze three use case scenarios pursued by ongoing work at standards development organizations, namely MEF, 3GPP, and ETSI NFV, discussing standardization opportunities around blockchain-based DApps.
Smart contracts and blockchain have the potential to change the current shape of cloud markets by enabling the development of completely decentralized cloud/fog solutions, which lower costs and enforce predictable results without requiring any intermediary. In this article, we survey three of these solutions, namely Golem, iExec, and SONM, compare them, and identify some of the problems they leave unsolved. Moreover, we consider existing standards for the development of interoperable decentralized cloud solutions that would allow such systems to compete with large providers and would prevent vendor lock-in. We believe that our study contributes to the evolution of cloud systems not only by pointing out incompatibilities among projects and possible solutions for research problems in the area, but also by reviewing the existing standards and suggesting new standardization opportunities.
Domain name systems and certificate authority systems may have security and trust problems in their implementation. This article summarizes how these systems work and what the implementation problems may be. There are blockchain-based decentralized solutions that claim to overcome those problems. We provide a brief explanation on how blockchain systems work, and their strengths are explained. DNS security challenges are given. Blockchain-based DNS solutions are classified and described in detail according to their services. The advantages and feasibility of these implementations are discussed. Last but not least, the possibility of the decentralized Internet is questioned.
With the fast development and expansion of the Internet of Things (IoT), billions of smart devices are being continuously connected, and smart homes, as a typical IoT application, are providing people with various convenient applications, but face security and privacy issues. The idea of Blockchain (BC) theory has brought about a potential solution to the IoT security problem. The emergence of blockchain technology has brought about a change of decentralized management, providing an effective solution for the protection of network security and privacy. On the other hand, the smart devices in IoT are always lightweight and have less energy and memory. This makes the application of blockchain difficult. Against this background, this paper proposes a blockchain model based on hypergraphs. The aims of this model are to reduce the storage consumption and to solve the additional security issues. In the model, we use the hyperedge as the organization of storage nodes and convert the entire networked data storage into part network storage. We discuss the design of the model and security strategy in detail, introducing some use cases in a smart home network and evaluating the storage performance of the model through simulation experiments and an evaluation of the network.
In order to prevent sensitive data tampering in the application of security monitoring, intelligent traffic, and other sensitive Internet of Things, the research on WMSN (wireless multimedia sensor networks) application system based on blockchain and IPFS (InterPlanetary File System) is of great significance. However, WMSN data are characterized by high dimensionality, large scale, and multiple types, so it is challenging to search WMSN data efficiently over blockchain system. This paper proposed a novel One Permutation with Rotation and cross-polytope locality-sensitive hashing (OPRCP) method of approximate nearest neighbor binary query for querying binary hybrid data in the form of WMSN multimedia data (containing two hybrid types of data, such as image-text and image-audio). Firstly, a binary hybrid data index was built with the method of locality-sensitive hashing (LSH) to retain content similarity among original data objects for performing accurate queries. Secondly, the approximate nearest neighbor search strategy was used in place of the nearest neighbor strategy, to reduce querying time. Finally, a binary hybrid data model was employed to cope with multiple types of data in WMSN and carry out collaborative search of binary hybrid data. The experimental results show that compared with other mainstream methods, the proposed OPRCP method is widely adaptive to massive high-dimensional data in multiple types and can improve the accuracy of query results. The OPRCP method exhibits good performance, effectively saves resources, and reduces query time for a variety of datasets. It is an effective solution to the binary hybrid search of approximate neighbors, and it is applicable to the WMSN data search based on smart contracts in WMSN blockchain systems.