Central Bank Digital Currency (CBDC) is gaining popularity due to its potential benefit. However, experiments to explore the Distributed Ledger Technology (DLT) based CBDC is mostly done in the wholesale area, not in the retail area which has more impact on the public. This paper proposes a CBDC design where the digital currency or token that is distributed in the wholesale DLT network, can be widely accessed by the public through accounts provided by commercial banks. The proposed design maintains reliability as well as user-friendliness and scalability. This paper describes the architecture, infrastructure, and business process of the proposed design.
As the core of a blockchain system, the consensus mechanism not only helps to maintain the consistency of nodes' data but also gets involved in issuance of tokens and prevention of attacks. Since the first blockchain system was born in 2009, it has been continuously improved with the development of the blockchain technology and evolved into multiple new branches. Starting with the basic introduction of the consensus and the classic Byzantine Generals Problem in distributed computing area, this chapter proposes a thorough classification of current consensus protocols in blockchain system, enumerates the characteristics of mainstream protocols (proof-of-work (PoW), proof-of-stake (PoS), delegated PoS (DPoS), practical Byzantine fault tolerance (PBFT), etc.) and analyzes the strengths and weaknesses of them. Then we compare the performances of them from the number of nodes to the degree of scalability and other aspects. In the end, we introduce the incentive mechanism in the design of a consensus and summarize the future directions of developing more practical consensus schemes.
The millions of people in the world will be using billions of devices in the future Internet and they all are controlled by a centralized or decentralized system. The Industrial Internet of Things (IIoT) provides an era of huge information sharing, storage and processing. The limitations with IIoT are security and reliability of data. Blockchain technology has emerged as the key player to provide the solution to data reliability and security. The data sharing between IIoT-based distributed centres will be enormous in the upcoming internet future and will be the bottleneck for most of the industries implementing IIoT. In this paper, we focus on the relationship between blockchain-IIoT integration challenges and optimal solutions for the improvement of IIoT services using IoT boards comparison.
Blockchains have seen a recent rise in popularity as a generic solution for trustless distributed applications across a wide range of industries. However, blockchain protocols have faced scalability issues in applications involving a growing number of participants. In this paper we instantiate and evaluate StakeCube, a proposal for a scalable shard-based distributed ledger. We further detail and tune a byzantine agreement algorithm suited for StakeCube's sharding structure, and we experimentally study and asses its performance, especially regarding scalability. We were successfully able to run StakeCube with up to 5000 participants, confirming up to 1100 bytes/s of transaction, with a confirmation time starting at 200 seconds. Finally, we use StakeCube in a large scale energy marketplace application, and show that a node running on a Raspberry Pi Zero is able to handle the load without issues.
Koushik Bhargav Muthe, Khushboo Sharma, Karthik Epperla Nagendra Sri
The market value of the Gaming industry was said to be over 138 Billion USD in 2019. Competitive Gaming or eSports was already included in the Asian Games 2020, and the Olympic committee is considering including eSports into Olympics 2024. The online gaming segment amounts up to 7 quintillion bytes of internet traffic every month. Most of this data is controlled by centralized gatekeepers like cloud agencies and game creators. This is causing many issues ranging from privacy concerns to latency. The game makers have complete rights over the game to arbitrarily change the rules, set prices for the assets, and control over game servers. Even the reward mechanisms in most of the games, including eSports, are controlled by the game producers, and these rewards have no real-world value. The motivation behind this research is to create a decentralized computation and token management infrastructure for game networks. This paper focuses on using Ethereum Blockchain, IPFS and ERC - Ethereum Request for Comment 1155 architecture to build a gaming-oriented public decentralized network.
Staking is an essential component in Proof-of-Stake (PoS) based blockchain systems. While a host of PoS blockchains have staking schemes in place, the implementations of those mechanisms are highly customized to meet the needs of specific blockchains and vary in terms of the offered functionalities. In this paper, we present EMS, an extensible and modular staking architecture for PoS systems. EMS specifies a generic and modular staking implementation framework by applying a novel bucket-based data structure across different system components. In particular, EMS is able to accommodate a variety of design requirements for staking in PoS systems by manipulating the optional fields in the bucket-based data structure, thereby providing great flexibility and extensibility. Our instantiation of EMS on the IoTeX blockchain further demonstrates its viability and effectiveness in practice.
Many Blockchain-as-a-Service (BaaS) providers have emerged with the growing interest in BaaS among enterprises. However, current BaaS providers can pose a potential security threat in the context of a centralized service provider and for clients that depend on the provider. In this study, we first consider the problem of auditing BaaS and develop an Enforcer architecture for trustworthy BaaS.
Abstract Background Blockchain technology has gained a great public interest due to the appearance of cryptocurrencies, a digital asset used for exchanging funds. Although blockchain calculations offer the benefits of security and reduced costs, blockchain is still strongly criticised for its lack of usefulness and resource-heavy consumption. Objectives The aim of this research is to provide different insights into blockchain technology and to propose NP-complete problems as a suitable alternative to the current consensus algorithm. Methods/approach This research discusses the current state of proposed alternatives, projects such as distributed volunteering for scientific purposes and different consensus algorithms within cryptocurrencies but focusing on incorporating NP-complete problems as a secondary, more useful option. Results Using the properties of NP-complete problems, it is possible to solve various problems in different areas, such as science, biology, medicine and finance, but also to improve business processes, optimize markets, payments and supply chains while decreasing environmental costs. Conclusions This paper shows that the alternative mechanisms are being developed and used to substitute an existing Blockchain algorithm with a more efficient one. It also suggests further investigation in this area because the alternatives greatly improve blockchain’s usability and efficiency.
Sangwon Hong, Yoongdoo Noh, Jeyoung Hwang, Chanik Park
Business is innovating with the advent of blockchain that tokenizes digital assets. To expand the blockchain's potential, Ethereum, a representative permissionless blockchain platform, supports the fungible token (FT) standard ERC-20 and the nonfungible token (NFT) standard ERC-721. Hyperledger Fabric (Fabric), a representative permissioned blockchain platform, proposed FabToken to support tokens in version 2.0.0 alpha. But FabToken contains only FTs, not NFTs. Given the market share in the enterprise blockchains, Fabric needs to support NFTs as soon as possible. This paper presents a unique digital asset management system called FabAsset so that Fabric can run decentralized applications that require NFTs. This paper describes the design of FabAsset, consisting of chaincode and SDK (Software Development Kit), and the prototype of a decentralized signature service leveraging FabAsset to validate its usefulness.
Blockchain is essentially a distributed ledger shared by all nodes in the system. All nodes in blockchain are equal, and each node holds all transactions and blocks in the network. As the network continues to expand, the data rises linearly. Participates are about to face the problem of storage limitation. Blockchain is hard to scale.This paper introduces ICIStrategy, a multi-node collaborative storage strategy based on intra-cluster integrity. In ICIStrategy, we divide all participates into several clusters. Each cluster requires holding all data of the network, whereas a node within the cluster does not need to maintain data integrity. It aims to solve the storage pressure by reducing the amount data that each participate need to store and reduce communication overhead by collaboratively storing and verifying blocks through in-cluster nodes. Moreover, the ICIStrategy could greatly save the overhead of bootstrapping. We show the mode of operation in our strategy. We further analysis the performance of ICIStrategy and conduct simulation experiments. The results of several comparative experiments show that our strategy just needs 25% of storage space needed by Rapidchain, which indeed solve the problem of storage limitation and improve the blockchain performance.
Over the last years, research activities on blockchain technologies have fairly increased. Firstly introduced with Bitcoin, some projects have since emerged to create or improve blockchain features like privacy while others propose to overcome technical limitations such as scalability and energy consumption. New proposals are often evaluated with ad hoc tools and experimental environments. Reproducibility and comparison of these new contributions with the state of the art of the blockchain technologies are therefore complicated. To the best of our knowledge, only a few tools partially address the design of a generic benchmarking of blockchain technologies (e.g., load generation). In this paper, we introduce BCTMark, a generic framework for benchmarking blockchain technologies on an emulated network in a reproducible way. To illustrate the portability of experiments using BCTMark, we have conducted some experiments on two different testbeds: a cluster of Dell PowerEdge R630 servers (Grid'5000) and one of Raspberry Pi 3+. Experiments have been conducted on three different blockchain systems (Ethereum Clique/Ethash and Hyperledger Fabric) to measure their CPU consumption and energy footprint for different numbers of clients.
Blockchain technology enables the trustless sharing of distributed ledgers among peers. Despite having valuable properties like decentralisation, and immutability of transactions, it incurs a high performance overhead as compared with traditional databases thus discouraging its further adoption. Even the usage of different transaction processors within the same Blockchain platform, namely Hyperledger Sawtooth, may result in different performance, for the same use case and the same transaction type. This paper proposes a methodology for evaluating the performance of two different transaction processors deployed in the Hyperledger Sawtooth platform. We evaluated experimentally the methodology and present the results of the experimental evaluation which may be useful to blockchain practitioners for future solution designs.
In the Bitcoin system, transaction history of an address can be useful in many scenarios, such as the balance calculation and behavior analysis. However, it is non-trivial for a common user who runs a light node to fetch historical transactions, since it only stores headers without any transaction details. It usually has to request a full node who stores the complete data. Validation of these query results is critical and mainly involves two aspects: correctness and completeness. The former can be implemented via Merkle branch easily, while the latter is quite difficult in the Bitcoin protocol. To enable the completeness validation, a strawman design is proposed, which simply includes the BF (Bloom filter) in the headers. However, since the size of BF is about KB, light nodes in the strawman will suffer from the incremental storage burden. What's worse, an integrated block must be transmitted when BF cannot work, resulting in large network overhead. In this paper, we propose LVQ, the first lightweight verifiable query approach that reduces the storage requirement and network overhead at the same time. To be specific, by only storing the hash of BF in headers, LVQ keeps data stored by light nodes being little. Besides, LVQ introduces a novel BMT (BF integrated Merkle Tree) structure for lightweight query, which can eliminate the communication costs of query results by merging the multiple successive BFs. Furthermore, when BF cannot work, a lightweight proof by SMT (Sorted Merkle Tree) is exploited to further reduce the network overhead. The security analysis confirms LVQ's ability to enable both correctness and completeness validation. In addition, the experimental results demonstrate its lightweight.
We establish the optimal security threshold for the Bitcoin protocol in terms of adversarial hashing power, honest hashing power, and network delays. Specifically, we prove that the protocol is secure if [ra < 1/Δ0 + 1/rh,,] where rh is the expected number of honest proof-of-work successes in unit time, ra is the expected number of adversarial successes, and no message is delayed by more than Δ0 time units. In this regime, the protocol guarantees consistency and liveness with exponentially decaying failure probabilities. Outside this region, the simple private chain attack prevents consensus. Our analysis immediately applies to any Nakamoto-style proof-of-work protocol; in the full version of this paper we also present the adaptations needed to apply it in the proof-of-stake setting, establishing a similar threshold there.
Most storage systems adopt distributed architecture to reach high reliability. In these distributed systems, a well-balanced data distribution can improve storage reliability. However, existing schemes rely on dealers to distribute data, bring back the risk of single-point failure again. In this paper, we propose a blockchain-based storage system with financial incentives for load-balancing. Nodes in the system are rational and compete for data to earn a reward. The only source of storage rewards is from users' payment for leasing storage. To reach load-balancing, we design a new incentive scheme, which contains an income function to reward the nodes who own proper data and punish the nodes who own excessive data. In the system, each node continuously generates a proof of storage. We present a chain structure using the proofs to detect node failures and record data distribution. The state of distribution could be taken as input to the income function for reward allocation. We decouple the role of nodes from miners to reduce their workload, making the system more compatible. Our simulation experiments show efficient performance in the data distribution. The system can always recover to a balanced status as the blockchain grows up.
The Blockchain is a new technology developed on the basis of Bitcoin system. In fact, the developing blockchain technology has been going beyond the single application scope of cryptocurrency, and becoming one of a core support to solve financial, economic and even social problems on Internet. Based on the Bitcoin system, this paper first analyzes the basic issues of implementing distributed storage, consensus negotiation and cryptographic security in the blockchain. On this basis, several representative blockchain technologies are analyzed, including Smart-contracts, Super-ledger and Stable-currency system. Finally, the trend of his applications are prospected.
Superlight clients enable the verification of proof-of-work-based blockchains by checking only a small representative number of block headers instead of all the block headers as done in simplified payment verification (SPV). Such clients can be embedded within other blockchains by implementing them as smart contracts, allowing for cross-chain verification. One such interesting instance is the consumption of Bitcoin data within Ethereum by implementing a Bitcoin superlight client in Solidity. While such theoretical constructions have demonstrated security and efficiency in theory, no practical implementation exists. In this work, we put forth the first practical Solidity implementation of a superlight client which implements the NIPoPoW superblocks protocol. Contrary to previous work, our Solidity smart contract achieves sufficient gas-efficiency to allow a proof and counter-proof to fit within the gas limit of a block, making it practical. We provide extensive experimental measurements for gas consumption. The optimizations that enable gas-efficiency heavily leverage a novel technique which we term hash-and-resubmit, which almost completely eliminates persistent storage requirements, the most expensive operation of smart contracts in terms of gas. Instead, the contract asks contesters to resubmit data and checks their veracity by hashing it. Other optimizations include off-chain manipulation of proofs in order to remove expensive look-up structures, and the usage of an optimistic schema. We show that such techniques can be used to bring down gas costs significantly and may be of independent interest. Lastly, our implementation allows us to calculate concrete cryptoeconomic parameters for the superblocks NIPoPoWs protocol and in particular to make recommendations about the monetary value of the collateral parameters. We provide such parameter recommendations over a variety of liveness settings.
In this demo, we present SEBDB, a novel blockchain database that integrates immutability and transparency properties of blockchain with modeling and query ability of relational database. In summary, SEBDB has the following advantages: First, it adopts the linked structure and full replication of data among multiple participants to guarantee immutability and transparency. Second, it introduces the relational model to blockchain without introducing extra overhead, based on which relational queries are supported. SEBDB supports SQL-like language as the general interface to support convenient application development, in which intrinsic operations are re-defined and re-implemented to suit for blockchain platform. Third, it supports rich verifiable queries based on the proposed authenticated index, thin clients can participate in the system regardless of limitations of storage, network, and computing resources. We demonstrate the usability and scalability of SEBDB using a donation system.
João Paulo de Brito Gonçalves, Roberta Lima Gomes, Rodolfo da Silva Villaça, Esteban Municio · 5 authors
Service Level Agreements (SLAs) are used to establish a contract, an agreement between two parties, which can be between two operators, or between a customer and an operator. The SLAs methods are a key aspect between consumers and providers, which can continuously monitor the Quality of Service (QoS) attributes and enforce its reliability, but the SLA also needs an entity to manage it. Smarts contracts are programs that are executed in a blockchain and ensure integrity and reliability to data stored in the distributed structure. This work proposes a solution using smarts contracts and blockchains in order to simplify the process of SLA validation.
Xiangjun Zhang, Weiguo Wu, Shiyuan Yang, Xiong Wang
Driven by advanced 5G cellular systems, mobile edge computing (MEC) has emerged as a promising technology that can meet the energy efficiency and latency requirements of IoT applications. Edge service migration in the MEC environment plays an important role in ensuring user service quality and enhancing terminal computing capabilities. Application services on the edge side should be migrated from different edge servers to edge nodes closer to users, so that services follow users and ensure high-quality services. In addition, during the migration process, edge services face security challenges in an edge network environment without centralized management. To tackle this challenge, this paper innovatively proposes a blockchain-based security edge service migration framework, Falcon, which uses mobile agents different from VM and container as edge service carriers, making migration more flexible. Furthermore, we considered the dependencies between agents and designed a service migration algorithm to maximize the migration benefits and obtain better service quality. In order to ensure the migration of edge services in a safe and reliable environment, Falcon maintains an immutable alliance chain among multiple edge clouds. Finally, the experimental results show that “Falcon” has lower energy consumption and higher service quality.