Blockchain Scalability Research Articles

블록체인 기법의 확장가능성을 위한 병행 수행 제어 기법에 대한 연구

블록체인 기법의 확장가능성을 위한 병행 수행 제어 기법에 대한 연구

A Many-Objective Optimization Model of Industrial Internet of Things Based on Private Blockchain

The Industrial Internet of Things (IIoT) has developed rapidly in recent years. Private blockchains with decentralization, flexible rules, and good privacy protection can be applied in the IIoT to process the massive data and tackle the security problem. However, the scalability of blockchain places a restriction on IIoT. Accordingly, this article proposes an improved algorithm based on Two_Arch2 to improve the scalability and decentralization while reducing the latency and cost of the blockchain. By integrating the private blockchain theory to IIoT and simultaneously considering the above four objectives, a many-objective blockchain-enabled IIoT model is constructed. Then an improved Two_Arch2 algorithm is utilized to solve the model. Experimental results show that the improved algorithm can effectively optimize four indicators of the model.

Scalable and redactable blockchain with update and anonymity

Internet-of-Things (IoT) envisions communications between heterogeneous devices and utilization of the associated data for smart decision making. Blockchain bridges the gap between widely-distributed IoT devices and the need for a universal trust-layer. When applying blockchain for IoT, some concerns can arise. Among them, scalability is a crucial factor because it decides whether blockchain can keep empowering IoT in the long term. According to a recent survey by Ali et al., some newly launched blockchains are suffering from powerful attacks (e.g. 51% attack) when the computing pool is small, and the number of participated nodes is inadequate (USENIX 2016). To ensure the scalability of initially-deployed blockchains, a proper countermeasure is important to be devised. Ateniese et al. proposed the notion of the redactable blockchain (EuroS&P 2017) which allows block history to be rewritten by using chameleon hash. However, the distribution and management of trapdoor key is crucial for the scalability of chameleon hash as well as redactable blockchain. To deal with the above problems, we propose two cryptographic schemes as the new theoretic tools for blockchain redaction: time updatable chameleon hash (TUCH) and linkable-and-redactable ring signature (LRRS). The use of TUCH and LRRS schemes enables redaction to take place scalably and anonymously where the spontaneous ring is generated for redaction, which costs little expenditures to rewrite a block content. Specifically, the redaction will be processed without assigning and splitting trapdoor key among multiple users in a complex way, and achieve transaction anonymity for users. What is more, we briefly instantiate how to build a redactable blockchain with update and anonymity (SRB) with our proposed TUCH and LRRS. While security analysis confirms that our proposals are theoretically secure, the experimental results show that our proposals are efficient for implementation purposes.

Internet of Things Based Blockchain for Temperature Monitoring and Counterfeit Pharmaceutical Prevention.

The top priority of today’s healthcare system is delivering medicine directly from the manufacturer to end-user. The pharmaceutical supply chain involves some level of commingling of a collection of stakeholders such as distributors, manufacturers, wholesalers, and customers. The biggest challenge associated with this supply chain is temperature monitoring as well as counterfeit drug prevention. Many drugs and vaccines remain viable within a specific range of temperatures. If exposed beyond this temperature range, the medicine no longer works as intended. In this paper, an Internet of Things (IoT) sensor-based blockchain framework is proposed that tracks and traces drugs as they pass slowly through the entire supply chain. On the one hand, these new technologies of blockchain and IoT sensors play an essential role in supply chain management. On the other hand, they also pose new challenges of security for resource-constrained IoT devices and blockchain scalability issues to handle this IoT sensor-based information. In this paper, our primary focus is on improving classic blockchain systems to make it suitable for IoT based supply chain management, and as a secondary focus, applying these new promising technologies to enable a viable smart healthcare ecosystem through a drug supply chain.

Privacy-Utility Tradeoffs in Routing Cryptocurrency over Payment Channel Networks

As the adoption of cryptocurrencies grows to unprecedented levels, the scalability of blockchain technologies has become increasingly important. A major open question is whether cryptocurrencies are fundamentally able to support as much traffic as traditional, centralized solutions. One prominent approach for improving the scalability of blockchains is payment channel networks (PCNs) [1]. Instead of committing every transaction to the blockchain, a separate overlay network (called a PCN) is maintained. Each node represents a user, and each edge (or payment channel) represents pre-allocated funds that can be efficiently transacted between the two endpoints under a mutual agreement. Users can transact with each other by relaying payments over a sequence of channels.

A Highly Parallelized PIM-Based Accelerator for Transaction-Based Blockchain in IoT Environment

Blockchain has gained a lot of attention from both academia and industry. However, traditional standard blockchains, such as Bitcoin and Ethereum, suffer from low throughput, high computation overhead, and large transaction fee, which is not suitable for Internet of Things (IoT) transactions. Recently, transaction-based approaches, such as Tangle structure which is based on a directed acyclic graph (DAG), have emerged to solve blockchain scalability issues for IoT environment. In transaction-based blockchain, for a transaction, namely, a node, to be attached to the Tangle, it needs to verify two other transactions. However, with the Tangle expanding, this attaching process consumes huge computational resources and energy, which severely limits the performance of the transaction-based blockchain. In this article, we present Re-Tangle, a highly parallelized processing-in-memory (PIM)-based accelerator for transaction-based blockchain. Re-Tangle is composed of a random walking module, a transaction validation module, and a PoW module, to improve the Tangle system performance. These modules transfer Tangle functions, such as fast exponentiation and modular, into ReRAM-based logic analog computation units. In the random walking module, Re-Tangle maintains an exponentiation table to reduce its design complexity and improve its computation efficiency. In the transaction validation module, Re-Tangle further proposes a highly parallel modular unit to accelerate the validation of different tags in a transaction. In the PoW module, we decompose the Curl hash function into basic logic OR, AND, SHIFT, and XOR operations, and map these logic operations to ReRAM crossbars in parallel to accelerate the working process. The experimental results show that Re-Tangle distinguishes itself from other architectures with significant performance improvement and energy saving. The throughput of Re-Tangle is about $22.4\times $ and $2.38\times $ higher compared with CPU and GPU, respectively, and the energy consumption of Re-Tangle is $83.5\times $ and $5.77\times $ less for equal workload.

Solutions to Scalability of Blockchain: A Survey

Blockchain-based decentralized cryptocurrencies have drawn much attention and been widely-deployed in recent years. Bitcoin, the first application of blockchain, achieves great success and promotes more development in this field. However, Bitcoin encounters performance problems of low throughput and high transaction latency. Other cryptocurrencies based on proof-of-work also inherit the flaws, leading to more concerns about the scalability of blockchain. This paper attempts to cover the existing scaling solutions for blockchain and classify them by level. In addition, we make comparisons between different methods and list some potential directions for solving the scalability problem of blockchain.

Scaling Blockchains: A Comprehensive Survey

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.

A Novel Methodology-Based Joint Hypergeometric Distribution to Analyze the Security of Sharded Blockchains

Cryptocurrencies (e.g., Bitcoin and Ethereum), which promise to become the future of money transactions, are mainly implemented with blockchain technology. However, blockchain suffers from scalability issues. Sharding is the leading solution for blockchain scalability. Sharding splits the blockchain network into sub-chains called shards/committees. Each shard processes a sub-set of transactions, rather than the entire network processing all transactions. This raises security issues for sharding-based blockchain protocols. In this paper, we propose a novel methodology to analyze the security of these protocols (e.g., OmniLedger and RapidChain). In particular, this methodology estimates the failure probability of one sharding round taking into consideration the failure probabilities of all shards. To illustrate the effectiveness of the estimated failure probability, we conduct a numerical analysis of our methodology based on a huge number of trials. Finally, we compute confidence intervals to accurately estimate the failure probability and compare our methodology with existing approaches.

Exploring blockchain for the energy transition: Opportunities and challenges based on a case study in Japan

Under pressures to reach net zero emissions by 2050, there is an ongoing transition of energy decarbonization, decentralization and digitalization. Physical and information flows in energy systems are increasingly complex and distributed, leaving centralized structures inefficient. Blockchain technology is suggested as part of the next step in this transition. Blockchain has potential to facilitate distributed, peer-to-peer trading with reduced transaction costs, increased security via cryptography, and prosumer choice. However, there are as of yet multiple challenges to the expansion of blockchain in the energy sector. This paper argues that analysis of these challenges requires a multi-angled approach incorporating technological, economic, social, environmental, and institutional dimensions. First, each dimension is explored, substantiated based on a blockchain-based energy system case in Japan. Concrete challenges of scaling this case toward 2050 and potential opportunities in overcoming these challenges are discussed, leveraging extensive literature review. Finally, an overview of strategic indications is suggested. The findings of this paper present initial indications on challenges and opportunities to overcome them based on a multi-dimensional overview. It is suggested that the factors identified across the dimensions are interrelated. This would in turn call for coherent innovation management and multi-stakeholder innovation ecosystems. Living Labs and regulatory sandboxes are prospective foundations to support such ecosystems, and enable informed decision-making among both private and public sector actors. At large, it is suggested that a holistic and pragmatic approach can benefit the application and scalability of blockchain in the energy transition.

LSB: A Lightweight Scalable Blockchain for IoT security and anonymity

In recent years, Blockchain has attracted tremendous attention due to its salient features including auditability, immutability, security, and anonymity. Resulting from these salient features, blockchain has been applied in multiple non-monetary applications including the Internet of Things (IoT). However, blockchain is computationally expensive, has limited scalability and incurs significant bandwidth overheads and delays which are not suited for most IoT applications. In this paper, we propose a Lightweight Scalable blockchain (LSB) that is optimized for IoT requirements while also providing end-to-end security. Our blockchain instantiation achieves decentralization by forming an overlay network where high resource devices jointly manage the blockchain. The overlay is organized as distinct clusters to reduce overheads and the cluster heads are responsible for managing the public blockchain. We propose a Distributed Time-based Consensus algorithm (DTC) which reduces the mining processing overhead and delay. Distributed trust approach is employed by the cluster heads to progressively reduce the processing overhead for verifying new blocks. LSB incorporates a Distributed Throughput Management (DTM) algorithm which ensures that the blockchain throughput does not significantly deviate from the cumulative transaction load in the network. We explore our approach in a smart home setting as a representative example for broader IoT applications. Qualitative arguments demonstrate that our approach is resilient to several security attacks. Extensive simulations show that packet overhead and delay are decreased and blockchain scalability is increased compared to relevant baselines.

Evaluating Methods for the Identification of Off-Chain Transactions in the Lightning Network

Payment channels and off-chain transactions are used to address blockchain scalability. Those mechanisms rely on the blockchain proper, as the resolution mechanism. They allow for high transaction throughput due to the pure peer-to-peer nature of the transaction exchange that happens directly between the peers, without the involvement of the blockchain transactions. The transactions are not mediated through the blockchain but happen off-chain. The transactions in such overlay networks are not included in the blockchain, they nevertheless leave some data traces in a public ledger. We have used the Bitcoin mainnet and testnet blockchains together with the Lightning network node to explore what can be inferred from the underlying blockchain in the context of Lightning transactions, channel setup, and channel teardown. The main purpose of this study is to identify what methods, transaction signatures, and data can be used to understand the non-visible publicly off-chain transactions. We have proposed heuristics for identifying the setup and teardown transactions, quantified and analyzed the effectiveness of our proposed methods. Using the data from the Bitcoin blockchain, as well as the data from the Lightning network to link related information we have found when parsing the blockchain, we generate network graph representations showing the relationships between the Lightning network channels identified on the blockchain. This study is significant from the personal data and privacy perspectives, as well as from forensics. We have established that at least 75% of all P2WSH transactions are Lightning transactions, and some of the channels can be deduced from the blockchain analysis. The synthesized results demonstrate that our methods are viable for identifying a subset of transactions and that only partial topology of the payment channels can be obtained from the data left in the blockchain.

UBaaS: A unified blockchain as a service platform

Blockchain is an innovative distributed ledger technology which has attracted a wide range of interests for building the next generation of applications to address lack-of-trust issues in business. Blockchain as a service (BaaS) is a promising solution to improve the productivity of blockchain application development. However, existing BaaS deployment solutions are mostly vendor-locked: they are either bound to a cloud provider or a blockchain platform. In addition to deployment, design and implementation of blockchain-based applications is a hard task requiring deep expertise. Therefore, this paper presents a unified blockchain as a service platform (uBaaS) to support both design and deployment of blockchain-based applications. The services in uBaaS include deployment as a service, design pattern as a service and auxiliary services. In uBaaS, deployment as a service is platform agnostic, which can avoid lock-in to specific cloud platforms, while design pattern as a service applies design patterns for data management and smart contract design to address the scalability and security issues of blockchain. The proposed solutions are evaluated using a real-world quality tracing use case in terms of feasibility and scalability.

Trust-Based Shard Distribution Scheme for Fault-Tolerant Shard Blockchain Networks

Blockchains guarantee data integrity through consensus of distributed ledgers based on multiple validation nodes called miners. For this reason, any blockchain system can be critically disabled by a malicious attack from a majority of the nodes (e.g., 51% attack). These attacks are more likely to succeed as the number of nodes required for consensus is smaller. Recently, as blockchains are becoming too large (making them difficult to store, send, receive, and manage), sharding is being considered as a technology to help improve the transaction throughput and scalability of blockchains. Sharding distributes block validators to disjoint sets to process transactions in parallel. Therefore, the number of validators of each shard group is smaller, which makes shard-based blockchains more vulnerable to 51% attacks than blockchains that do not use sharding. To solve this problem, this paper proposes a trust-based shard distribution (TBSD) scheme that assigns potential malicious nodes in the network to different shards, preventing malicious nodes from gaining a dominating influence on the consensus of a single shard. TBSD uses a trust-based shard distribution scheme to prevent malicious miners from gathering in on one shard by integration of a trust management system and genetic algorithm (GA). First, the trust of all nodes is computed based on the previous consensus result. Then, a GA is used to compute the shard distribution set to prevent collusion of malicious miners. The performance evaluation shows that the proposed TBSD scheme results in a shard distribution with a higher level of fairness than existing schemes, which provides an improved level of protection against malicious attacks.

Basing Diversified Services of Complex IIoT Applications on Scalable Block Graph Platform

In complex Industrial Internet of Things (IIoT) application systems, there may exist a variety of functional sub-systems which provide divergent services to the users and the relationship among these services could be strong, which is evidently very common in practice. As one such IoT application, the smart city is designed to use intelligent services in an environment where transport, environment, energy, living, governance, and civic components are integrated to operate the city in a smart and efficient manner. Surprisingly, however, the current state-of-the-art on blockchain does not show the progress on diversified services of the complex IIoT applications. This paper tends to fill the gap and presents a scalable block graph platform and consensus protocol for the complex IIoT applications by adopting the limited resources of IIoT devices. The platform and consensus protocol are generic in the sense that they can support any practical service. The directed acyclic graph represents a significant exhibition in improving the scalability of blockchains and supports our proposed consensus protocol in substance; moreover, the detailed syntax of the block graph is defined. The consensus protocol is showed to be secure against disloyal voting, sybil attack, and 51% attack. The real use case of smart city demonstrates the effectiveness of the proposal.

Hubs, Rebalancing and Service Providers in the Lightning Network

Payment channel networks are the most developed proposal to address the well-known issue of blockchain scalability. Currently, the Lightning Network (LN) is the mainstream and most used payment channel network. In a previous work we introduced CLoTH, a payment channel network simulator we developed to analyze capabilities and limitations of such networks. In this work, using CLoTH, we present results of three groups of simulations on a recent snapshot of the LN, aimed to shed a light on the following aspects. Firstly, we investigated how hubs influence the LN performance. Then, we analyzed the effectiveness of two different channel rebalancing approaches, an active and a passive one. Eventually, we studied performance of the LN when a few service-providers nodes receive payments from the other network nodes, which is a typical use case of payment channel networks. We found that the LN is resilient to the removal of hubs, that our passive rebalancing approach reduces of about one fourth the payments failures due to channel unbalancing, and that in the service-providers scenario a consistent part of payments fails because channels directing to the service providers become unbalanced. Our work contributes to prove the strengthen of the Lightning Network when removing hubs and its weakness in the service-provider scenario. In addition, the passive rebalancing approach proposed in this work is a good candidate for the implementation in the Lightning Network protocol to mitigate channel unbalancing.

Zero-Knowledge Proof-of-Identity: Sybil-Resistant, Anonymous Authentication on Permissionless Blockchains and Incentive Compatible, Strictly Dominant Cryptocurrencies

Zero-Knowledge Proof-of-Identity from trusted public certificates (e.g., national identity cards and/or ePassports; eSIM) is introduced here to permissionless blockchains in order to remove the inefficiencies of Sybil-resistant mechanisms such as Proof-of-Work (i.e., high energy and environmental costs) and Proof-of-Stake (i.e., capital hoarding and lower transaction volume). The proposed solution effectively limits the number of mining nodes a single individual would be able to run while keeping membership open to everyone, circumventing the impossibility of full decentralization and the blockchain scalability trilemma when instantiated on a blockchain with a consensus protocol based on the cryptographic random selection of nodes. Resistance to collusion is also considered. Solving one of the most pressing problems in blockchains, a zk-PoI cryptocurrency is proved to have the following advantageous properties: - an incentive-compatible protocol for the issuing of cryptocurrency rewards based on a unique Nash equilibrium - strict domination of mining over all other PoW/PoS cryptocurrencies, thus the zk-PoI cryptocurrency becoming the preferred choice by miners is proved to be a Nash equilibrium and the Evolutionarily Stable Strategy - PoW/PoS cryptocurrencies are condemned to pay the Price of Crypto-Anarchy, redeemed by the optimal efficiency of zk-PoI as it implements the social optimum - the circulation of a zk-PoI cryptocurrency Pareto dominates other PoW/PoS cryptocurrencies - the network effects arising from the social networks inherent to national identity cards and ePassports dominate PoW/PoS cryptocurrencies - the lower costs of its infrastructure imply the existence of a unique equilibrium where it dominates other forms of payment

The CLoTH Simulator for HTLC Payment Networks with Introductory Lightning Network Performance Results

The Lightning Network (LN) is one of the most promising off-chain scaling solutions for Bitcoin, as it enables off-chain payments which are not subject to the well-known blockchain scalability limit. In this work, we introduce CLoTH, a simulator for HTLC payment networks (of which LN is the best working example). It simulates input-defined payments on an input-defined HTLC network and produces performance measures in terms of payment-related statistics (such as time to complete payments and probability of payment failure). CLoTH helps to predict issues and obstacles that might emerge in the development stages of an HTLC payment network and to estimate the effects of an optimisation action before deploying it. We conducted simulations on a recent snapshot of the HTLC payment network of LN. These simulations allowed us to identify network and payments configurations for which a payment is more likely to fail than to succeed. We proposed viable solutions to avoid such configurations.

Quantum-secured blockchain

Blockchain is a distributed database which is cryptographically protected against malicious modifications. While promising for a wide range of applications, current blockchain platforms rely on digital signatures, which are vulnerable to attacks by means of quantum computers. The same, albeit to a lesser extent, applies to cryptographic hash functions that are used in preparing new blocks, so parties with access to quantum computation would have unfair advantage in procuring mining rewards. Here we propose a possible solution to the quantum era blockchain challenge and report an experimental realization of a quantum-safe blockchain platform that utilizes quantum key distribution across an urban fiber network for information-theoretically secure authentication. These results address important questions about realizability and scalability of quantum-safe blockchains for commercial and governmental applications.

Is Blockchain Ready to Revolutionize Online Advertising?

The 200-billion-dollar per annum online advertising ecosystem has become infested with thousands of intermediaries exploiting user data and advertising budgets. All key stakeholders in the value-chain are infected: advertisers with fraud, publishers with their diminishing share of advertising budgets, and users with their right to privacy. Blockchain presents a possible solution to addressing the critical issues in the online advertising supply chain. The question remains whether blockchain scalability, energy-efficiency, and token volatility issues can be solved in the coming years to the extent that online advertising could widely leverage trustlessness and the benefits gained from blockchain technology. This paper aims to review the current progress and to open a discussion to address the issues. We present new requirements for blockchain-based online advertising solutions. We have also analyzed the available solutions against the requirements and recommend directions for future research and solution development. Evidence from our research points out that blockchain is not yet ready to be widely implemented in online advertising. More research is needed, and new proof-of-concepts need to be developed before blockchain technology can be considered a trusted alternative for the current online advertising marketplace based on open real-time bidding.