Guangsheng Yu, Xu Wang, Kan Yu, Wei Ni · 6 authors
The Blockchain technology, featured with its decentralized tamper-resistance based on a Peer-to-Peer network, has been widely applied in financial applications, and even further been extended to industrial applications. However, the weak scalability of traditional Blockchain technology severely affects the wide adoption due to the well-known trillema of decentralization-security-scalability in Blockchains. In regards to this issue, a number of solutions have been proposed, targeting to boost the scalability while preserving the decentralization and security. They range from modifying the on-chain data structure and consensus algorithms to adding the off-chain technologies. Therein, one of the most practical methods to achieve horizontal scalability along with the increasing network size is sharding, by partitioning network into multiple shards so that the overhead of duplicating communication, storage, and computation in each full node can be avoided. This paper presents a survey focusing on sharding in Blockchains in a systematic and comprehensive way. We provide detailed comparison and quantitative evaluation of major sharding mechanisms, along with our insights analyzing the features and restrictions of the existing solutions. We also provide theoretical upper-bound of the throughput for each considered sharding mechanism. The remaining challenges and future research directions are also reviewed.
Blockchain (e.g., Bitcoin and Ethereum) has drawn much attention and has been widely-deployed in recent years. However, blockchain scalability is emerging as a challenging issue. This paper outlines the existing solutions to blockchain scalability, which can be classified into two categories: first layer and second layer solutions. First layer solutions propose modifications to the blockchain (i.e., changing the blockchain structure, such as block size) while second layer solutions propose mechanisms that are implemented outside of the blockchain. In particular, we focus on sharding as a promising first layer solution to the scalability issue; the basic idea behind sharding is to divide the blockchain network into multiple committees, each processing a separate set of transactions. More specifically, (a) we propose a taxonomy based on committee formation and intra-committee consensus; and (b) we compare the main existing sharding-based blockchain protocols. We also present a performance-based comparative analysis (i.e., throughput and latency), of the advantages, and disadvantages in existing scalability solutions.
In the IoT (Internet of Things) environment, smart homes, smart grids, and telematics constantly generate data with complex attributes. These data have low heterogeneity and poor interoperability, which brings difficulties to data management and value mining. The promising combination of blockchain and the Internet of things as BCoT (blockchain of things) can solve these problems. This paper introduces an innovative method DCOMB (dual combination Bloom filter) to firstly convert the computational power of bitcoin mining into the computational power of query. Furthermore, this article uses the DCOMB method to build blockchain-based IoT data query model. DCOMB can implement queries only through mining hash calculation. This model combines the data stream of the IoT with the timestamp of the blockchain, improving the interoperability of data and the versatility of the IoT database system. The experiment results show that the random reading performance of DCOMB query is higher than that of COMB (combination Bloom filter), and the error rate of DCOMB is lower. Meanwhile, both DCOMB and COMB query performance are better than MySQL (My Structured Query Language).
Turki Ali Alghamdi, Ishtiaq Ali, Nadeem Javaid, Muhammad Shafiq
The Internet of Things (IoT) industry is growing very fast to transform factories, homes, farms and practically everything else to make them efficient and intelligent. IoT is applied in different resilient scenarios and applications. IoT faces lots of challenges due to lack of computational power, battery and storage resources. Fortunately, the rise of blockchain technology facilitates IoT in many security solutions. Using blockchain, communication between IoT and emerging computing technologies is made efficient. In this work, we propose a secure service provisioning scheme with a fair payment system for Lightweight Clients (LCs) based on blockchain. Furthermore, an incentive mechanism based on reputation is proposed. We use consortium blockchain with the Proof of Authority (PoA) consensus mechanism. Furthermore, we use Smart Contracts (SCs) to validate the services provided by the Service Providers (SPs) to the LCs, transfer cryptocurrency to the SPs and maintain the reputation of the SPs. Moreover, the Keccak256 hashing algorithm is used for converting the data of arbitrary size to the hash of fixed size. AES128 encryption technique is used to encrypt service codes before sending to the LCs. The simulation results show that the LCs receive validated services from the SPs at an affordable cost. The results also depict that the participation rate of SPs is increased because of the incentive mechanism.
Muhammad Anas Imtiaz, David Starobinski, Ari Trachtenberg
Orphan transactions are those whose parental income-sources are missing at the time that they are processed. These transactions are not propagated to other nodes until all of their missing parents are received, and they thus end up languishing in a local buffer until evicted or their parents are found. Although there has been little work in the literature on characterizing the nature and impact of such orphans, it is intuitive that they may affect throughput on the Bitcoin network. This work thus seeks to methodically research such effects through a measurement campaign of orphan transactions on live Bitcoin nodes. Our data show that, surprisingly, orphan transactions tend to have fewer parents on average than non-orphan transactions. Moreover, the salient features of their missing parents are a lower fee and larger size than their non-orphan counterparts, resulting in a lower transaction fee per byte. Finally, we note that the network overhead incurred by these orphan transactions can be significant, exceeding 17% when using the default orphan memory pool size (100 transactions). However, this overhead can be made negligible, without significant computational or memory demands, if the pool size is merely increased to 1000 transactions.
While the large-scale Internet of Things (IoT) makes many new applications feasible, like Smart Cities, IoT also brings new concerns on data reliability, security, and privacy. The rapid evolution in blockchain technologies, which relied on a decentralized, immutable and distributed ledger system for transaction data auditing, provides a prospective solution to address the issues in IoT. The blockchain and smart contract enabled security mechanism for IoT applications have attracted increasing interests from both academia and industry. However, integrating cryptocurrency-oriented blockchain technologies into IoT systems meets tremendous challenges on scalability, storage capacity, security, and privacy. Particularly, the performance of blockchain networks significantly relies on the performance of consensus mechanisms, e.g., in terms of data confidentiality, transaction throughput, and network scalability. In this chapter, given an in-depth review of state-of-the-art blockchain networks, the key matrix of designing consensus mechanism for IoT networks are identified in terms of throughput, scalability, and security. To demonstrate a case study on designing scalable, lightweight blockchain protocols for IoT systems, a Microchain framework is introduced and a proof-of-concept prototype is implemented in a physical network environment. The experimental results verify the feasibility of integrating the Microchain into IoT systems.
Edge computing is a promising approach for provisioning distributed cloud services to Internet of Things (IoT) systems. Many recent studies propose that edge nodes use blockchain for the decentralized management and access control of IoT data. However, due to the massive volume of data and related transactions, edge servers will eventually run out of space to store the full chain. We introduce scalable and lightweight architecture called LiTiChain, a blockchain of blocks with finite lifetime. In LiTiChain, outdated transactions and blocks, that is, the blocks whose lifetimes are expired, can be safely removed from the chain. Two graphs are merged into the structure of LiTiChain: 1) a tree representing the order of expiry of lifetimes and 2) a linear graph representing the order of block creation. We show that this construction not only ensures the connectivity of the chain after block deletions but also helps to maintain the block height of shortened chain. LiTiChain also supports transactions whose lifetime is unknown at the time of creation. It is possible that some expired blocks need to be retained in the chain, in case they are needed to validate remaining blocks, which incurs additional storage costs. A detailed analysis of such overhead in storage costs is presented for stochastic and worst case scenarios. Extensive simulation is performed on actual and synthetic IoT data so as to gain insights on the storage costs under various lifetime distributions. It is demonstrated that LiTiChain provides a simple yet effective solution to scalability problems in storing blockchains for the IoT ecosystems.
Improving transaction throughput is an important challenge for Bitcoin. However, shortening the block generation interval or increasing the block size to improve throughput makes it sharing blocks within the network slower and increases the number of orphan blocks. Consequently, the security of the blockchain is sacrificed. To mitigate this, it is necessary to reduce the block propagation delay. Because of the contribution of new Bitcoin protocols and evolution of the Internet, the block propagation delay in the Bitcoin network has been shortened in recent years. In this study, we measure the block propagation delay on the Bitcoin network using a simulator, and investigate the effect of compact block relay---an up-to-date Bitcoin protocol---and Internet improvements from 2015 to 2019. The experimental results reveal that the block propagation delay is reduced by 64.5% for the 50th percentile and 63.7% for the 90th percentile due to Internet improvements, and by 90.1% for the 90th percentile and by 87.6% for the 90th percentile due to compact block relay.
Improving transaction throughput is an important challenge for Bitcoin. However, shortening the block generation interval or increasing the block size to improve throughput makes it sharing blocks within the network slower and increases the number of orphan blocks. Consequently, the security of the blockchain is sacrificed. To mitigate this, it is necessary to reduce the block propagation delay. Because of the contribution of new Bitcoin protocols and the improvements of the Internet, the block propagation delay in the Bitcoin network has been shortened in recent years. In this study, we identify impacts of compact block relay---an up-to-date Bitcoin protocol---and Internet improvement on the block propagation delay and fork rate in the Bitcoin network from 2015 to 2019. Existing measurement studies could not identify them but our simulation enables it. The experimental results reveal that compact block relay contributes to shortening the block propagation delay more than Internet improvements. The block propagation delay is reduced by 64.5% for the 50th percentile and 63.7% for the 90th percentile due to Internet improvements, and by 90.1% for the 50th percentile and by 87.6% for the 90th percentile due to compact block relay.
Open access
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Blockchain Technology Applications and Security
Caching and Content Delivery
Advanced Steganography and Watermarking Techniques
Muqaddas Naz, Fahad Ahmed Al-Zahrani, Rabiya Khalid, Nadeem Javaid · 7 authors
In a research community, data sharing is an essential step to gain maximum knowledge from the prior work. Existing data sharing platforms depend on trusted third party (TTP). Due to the involvement of TTP, such systems lack trust, transparency, security, and immutability. To overcome these issues, this paper proposed a blockchain-based secure data sharing platform by leveraging the benefits of interplanetary file system (IPFS). A meta data is uploaded to IPFS server by owner and then divided into n secret shares. The proposed scheme achieves security and access control by executing the access roles written in smart contract by owner. Users are first authenticated through RSA signatures and then submit the requested amount as a price of digital content. After the successful delivery of data, the user is encouraged to register the reviews about data. These reviews are validated through Watson analyzer to filter out the fake reviews. The customers registering valid reviews are given incentives. In this way, maximum reviews are submitted against every file. In this scenario, decentralized storage, Ethereum blockchain, encryption, and incentive mechanism are combined. To implement the proposed scenario, smart contracts are written in solidity and deployed on local Ethereum test network. The proposed scheme achieves transparency, security, access control, authenticity of owner, and quality of data. In simulation results, an analysis is performed on gas consumption and actual cost required in terms of USD, so that a good price estimate can be done while deploying the implemented scenario in real set-up. Moreover, computational time for different encryption schemes are plotted to represent the performance of implemented scheme, which is shamir secret sharing (SSS). Results show that SSS shows the least computational time as compared to advanced encryption standard (AES) 128 and 256.
With the rapid development of Internet, security and privacy of the Domain Name System (DNS) are becoming increasingly important. Thanks to its decentralized structure and immutability, blockchain technology has the potential to address relevant security and privacy challenges in the DNS. In this paper, we survey the blockchain-based DNS for different architectures. We envision our study to motivate more studies on the DNS based on the blockchain.
Based on a practical park planning project, this paper analyzes the requirements of cleaning management, puts forward a blockchain based scheme of smart park cleaning. It proposes the service model of cleaning blockchain, and designs the system framework, DAPP modules, smart contracts and process flow of the cleaning blockchain system. The approach is also applicable for the application of blockchain technology in smart park public services, housekeeping, device maintenance and other fields.
Jaehong Ahn, Mingyu Park, Hyungsik Shin, Jeongyeup Paek
E-commerce has become a crucial part of our life allowing us to buy products, request services, and transfer money easily with a press of a button. As such, establishing immutable trust and reputation of entities that are resilient to manipulation by the malicious are critical in today’s online systems. In this work, we propose a model for calculating trust and reputation using the values stored on blockchain ledger. The model is applied to blockchain-based online payment systems which have a characteristic of immutability by preventing data manipulation. The model normalizes user evaluations based on each user’s personal evaluation criteria that changes over time. In addition, the model derives reputation of, and trust between, users by applying psychological factors. We evaluate our model using not only simulated transaction data but also on real Bitcoin transaction-based dataset to show that our model is able to derive stable values from immutable transactions on blockchain-based online payment systems. Our model has been built into a live commercial blockchain service platform, and new application developments are underway.
The proliferation of unreliable and biased information is a significant\nproblem on the Internet. To assess the credibility of the information retrieved\nfrom news websites and other sources, users often resort to social platforms\nlooking for confirmation with trustworthy parties. However, users may be faced\nwith considerable obstacles posed by the platform provider, who can prevent\naccess to certain content. This paper presents DClaims, a system that provides\na censorship-resistant distributed service for the exchange of information over\nthe Internet using web annotations. DClaims' fully decentralized architecture\nrelies on Inter-Planetary File System (IPFS) and Ethereum blockchain, both of\nwhich offer desirable censorship resistant properties. DClaims is implemented\nas a web annotations browser extension which allows for the classification of\nnews articles, on news websites. From our evaluation of the system, we conclude\nthat a large scale implementation of the system is practical and economically\nviable.\n
Vero Estrada-Galiñanes, Racin Nygaard, Viktor Trón, Rodrigo Q. Saramago · 6 authors
Blockchain is the driving force behind a myriad of decentralized applications (dapps) that promise to transform the Internet. The next generation Internet, or web3, introduces a "universal state layer" to store data in p2p networks. Swarm, a native layer of the Ethereum web3 stack, aims at providing redundant storage for dapp code, data, as well as, blockchain and state data. Based on a diploma verification dapp use case, we share insights on the role of redundancy strategies in designing a reliable storage layer. Our proof-of-concept improves Swarm's resilience to failures by balancing repairs and storage, with a slightly added latency.
We study the use of Blockchain in an Internet of Things (IoT) environment where microservices are provided by sensors. Blockchain assures secure and trustworthy transactions, yet it causes high load caused by block creation on the numerous IoT nodes. To mitigate the load, sensor nodes are clustered and block creation is restricted to IoT cluster managers in the distributed Blockchain ledger. The concept is exemplified by a use case describing a neighborhood of smart homes that are equipped with environmental sensors such as dust, temperature, and precipitation sensors. We provide an implementation of the Blockchain IoT system comprising two consensus algorithms, Proof of Work (PoW) and Proof of Stake (PoS). By means of simulations conducted in Mininet, we derive first results which reveal that -- depending on the sensor polling period -- the service response time can be reduced by clustering. Further, clustering reduces PoW conflicts to about 30% due to creating fewer blocks.
The Domain Name System (DNS) is one of the most fundamental infrastructures of the Internet. However, due to its design philosophy and implementation architecture, the current DNS still suffers from the centralization problem and the data authenticity problem. In this paper, we analyze these two problems and propose a blockchain-based naming system called blockDNS to solve them simultaneously. In blockDNS, domain names can be applied and transferred freely in a decentralized way. Moreover, a lightweight verification mechanism is also proposed coupled with blockDNS. The verification mechanism allows website clients to verify the authenticity of resolution results with few overheads. Simulation results show that, compared to the Simplified Payment Verification method, blockDNS can cut down the overheads for data authenticity verification from 4.955KBytes to 380Bytes. Moreover, we also present an implementation case of blockDNS, which is compatible with the current naming system and can be deployed incrementally.
Blockchain has grown beyond cryptocurrency. It has found a sweet spot in applications that required increased trust and transparency among multi-party transactions. This paper describes our experience in the design, implementation and architecture of blockchain-based trade finance application. The implementation is based on permissioned blockchain Hyperledger Fabric. Recently, the number of projects embarked on blockchain application have grown significantly over the year. However, the current level of understanding of blockchain application is insufficient and the architectural aspects of the system has remained largely unexplored. This paper attempts to solve this problem. It applies the concept of software connectors as a medium to explore fundamental building blocks of software interaction and how they are composed into a more complex interaction.
Due to the vast, increasing number of devices connected to the internet, their high connectivity, diversity, heterogeneity, and the fact that these devices are incapable of carrying a strong security protocols, a number of security and privacy challenges arise. Thus, the IoT- BlockChain brings a lot of benefits, yet still several challenging issues of security, storage and privacy are being faced. Therefore, this present research work proposes a new architecture with an objective to provide robust security with unlimited storage capability that can be adapted to the IoT resources constraints by introducing the new component Security and Storing Manager (SSM) added to the BlockChain. The concept behind the SSM mechanism is based on both encrypting the main data which will be stored in the locked blocks scattered on the internet and storing only the hash of these data in the BlockChain. Through this process, the SSM achieves a role like burial of the data in an unknown place with an unknown name. Also, the access to the BlockChain is restricted by using the smart contract in the new proposed architecture which allows the BlockChain to manage the data access policy. We evaluated the performance of the proposed architecture using various performance measures. The results of our evaluation show that performance is improved by reducing the size of the BlockChain and achieving the security goals. Consequently, SSM paves the way to make our BlockChain smart.