A decade long thrive of cryptocurrency has shown its potential as a source of alternative-finance and the security and the robustness of the underpinning blockchain technology. However, most cryptocurrencies fail to show inimitability and their meanings in the real world. As a result, they usually start off as favourites but quickly become the outcasts of the digital asset market. The blockchain society attempts to anchor the value of cryp-tocurrency with real values by employing smart contracts and link it with computation resources and the digital-productivity that have value and demands in the real world. But their attempts have some undesirable effects due to a limited number of practical applications. This limitation is caused by the dilemma between high performance and decentralisation (universal join-ability). The emerging of blockchain sharding models, however, has offered a possible solution to address this dilemma. In this paper, we explore a financial model for blockchain sharding that will build an active link between the value of cryptocurrency and computation resources as well as the market and labour behaviours. Our model can adjust the price of resources and the compensation for maintaining a system based on those behaviours. We anchor the value of cryptocurrency by the amount of computation resources participated in and give the cryptocurrency a meaning as the exchange between computation resources globally. Finally, we present a working example which, through financial regularities, regulates the behaviour of anonymous participants, also incents/discourages participation dynamically.
Bitcoin-NG is among the first blockchain protocols to approach the \emph{near-optimal} throughput by decoupling blockchain operation into two planes: leader election and transaction serialization. Its decoupling idea has inspired a new generation of high-performance blockchain protocols. However, the existing incentive analysis of Bitcoin-NG has several limitations. First, the impact of network capacity is ignored. Second, an integrated incentive analysis that jointly considers both key blocks and microblocks is still missing. In this paper, we aim to address these two limitations. First, we propose a new incentive analysis that takes the network capacity into account, showing that Bitcoin-NG can still maintain incentive compatibility against the microblock mining attack even under limited network capacity. Second, we leverage a Markov decision process (MDP) to jointly analyze the incentive of both key blocks and microblocks, showing that the selfish mining revenue of Bitcoin-NG is a little higher than that in Bitcoin only when the selfish miner controls more than 35\% of the mining power. We hope that our in-depth incentive analysis for Bitcoin-NG can shed some light on the mechanism design and incentive analysis of next-generation blockchain protocols.
The interoperability across multiple blockchains would play a critical role in future blockchain-based data management paradigm. Existing techniques either work only for two blockchains or requires a centralized component to govern the cross-blockchain transaction execution, neither of which would meet the scalability requirement. This paper proposes a new distributed commit protocol, namely \textit{cross-blockchain transaction} (CBT), for conducting transactions across an arbitrary number of blockchains without any centralized component. The key idea of CBT is to extend the two-phase commit protocol with a heartbeat mechanism to ensure the liveness of CBT without introducing additional nodes or blockchains. We have implemented CBT and compared it to the state-of-the-art protocols, demonstrating CBT's low overhead (3.6\% between two blockchains, less than $1\%$ among 32 or more blockchains) and high scalability (linear scalability on up to 64-blockchain transactions). In addition, we developed a graphic user interface for users to virtually monitor the status of the cross-blockchain transactions.
In the blockchain, the consensus mechanism plays a key role in maintaining the security and legitimation of contents recorded in the blocks. Various blockchain consensus mechanisms have been proposed. However, there is no technical analysis and comparison as a guideline to determine which type of consensus mechanism should be adopted in a specific scenario/application. To this end, this work investigates three mainstream consensus mechanisms in the blockchain, namely, Proof of Work (PoW), Proof of Stake (PoS), and Direct Acyclic Graph (DAG), and identifies their performances in terms of the average time to generate a new block, the confirmation delay, the Transaction Per Second (TPS) and the confirmation failure probability. The results show that the consensus process is affected by both network resource (computation power/coin age, buffer size) and network load conditions. In addition, it shows that PoW and PoS are more sensitive to the change of network resource while DAG is more sensitive to network load conditions.
To overcome the fast-changing block withholding attacks among multiple mining pools composed of miners in the blockchain system, this paper proposes a mining pool computing power allocation (MPPA) algorithm, which significantly improves the revenues of mining pools with block withholding attacks. MPPA first establishes the revenue optimization model of mining pools, which includes current adequate total computing power, the revenues of honest mining, and the revenues of block withholding attacks. Then MPPA calculates the revenue gain generated by block withholding attacks on other mining pools. To adjust the fixed computing power in each iteration, we have the mining pool computing power allocation algorithm with a fixed change of computing power (MPPA_F). To adjust the optimal recovery and attack computing power, we have the mining pool computing power allocation algorithm with an optimal change of computing power (MPPA_O). The simulation results demonstrate that MPPA_F and MPPA_O can find the optimized solutions of power computing allocation for each mining pool and outperform the state-of-arts such as WSFS, ALLC, and ALLD.
Blockchain technology has been used in many fields such as data management, cloud computing and Internet of Things with the features of decentralization, transparency and immutability. In order to study the performance of a blockchain system with a light-load traffic, we establish a discrete-time non-exhaustive vacation queue with batch service and gated service. In this model, we regard transaction initiation, mining processing and block verification as arrival, vacation and service period, respectively. By using an embedded Markov chain method and a regeneration cycle approach, we derive the average response time of transactions. Experiment results with analysis and simulation show that the average response time of transactions is impacted by the arrival rate of transactions. Finally, we study the Nash equilibrium behavior and the socially optimal behavior of transactions, and present a pricing policy for transactions to maximize the social profit.
Shuai Wang, Xiaojun Tu, Hongfeng Chai, Quan Sun · 7 authors
As a new FinTech innovation regulation tool, regulatory sandbox effectively balances financial innovation and risk, so it is adopted by many regulatory authorities around the world. However, until now, regulatory sandbox is still at the stage of manually submitting data, and artificial intelligence has not been applied to it. Hence, in this paper, we propose the framework of Parallel FinTech Regulatory Sandbox based on the ACP approach (Artificial systems + Computational experiments + Parallel execution). Then, we talk about how to combine the emerging blockchain technology with intelligent regulatory sandbox, thus solving problems such as poor data flow and regulation sluggish. This paper is aimed at providing helpful guidance and reference for the development of FinTech regulatory sandbox.
Nowadays, as lightweight mobile clients become more powerful and widely used, more and more information is stored on lightweight mobile clients, user sensitive data privacy protection has become an urgent concern and prob... | Find, read and cite all the research you need on Tech Science Press
Blockchain technology has recently obtained widespread attention. And it is being regarded as potentially even more disruptive than the Internet, whose usage includes large areas of applications ranging from crypto currency, financial services, reputation system, Internet of Things, sharing economy to public and social services. The existing works of blockchain primarily are focused on key components and potential applications. However, in the existing blockchain systems, the waiting time of transactions is too long. Furthermore, it may produce serious consequences because many important transactions are not handled timely. To solve the problem, in the paper, the blockchain Queuing model with non-preemptive limited-priority is established, which considers the different transactions having different priority when being mined. There are two classes of transactions in the model, one is high-priority transaction with pay or with prior interest, the other is low-priority transaction without pay or without prior interest. And high-priority transactions can be mined preferentially when mining process is not occupied. If low-priority transaction is being mined, the arriving high-priority transaction will wait for the mining accomplishment. Through the analysis of the model, we compute average waiting time, average staying time and average length of queue. From simulation of the model, we find that transactions with pay or with prior interest and increase service rate of mining are effective for reducing waiting time. Besides, the two factors mutually reinforce to shorten waiting time. Finally, we conclude this paper and point out the direction of future research.
With the considerable exploration of blockchain in various industrial fields, the storage architectures of mainstream consortium blockchains exhibit significant performance limitations, which can't meet the requirements of efficient data access with massive data storage in enterprise-level business scenarios. In this paper, we creatively divided the underlying data of the consortium blockchain into two categories: continuous data and state data and proposed a new storage architecture to store and operate these two types of data efficiently. For continuous data, we designed a specialized index-based storage engine. For state data, we proposed a multi-level cache mechanism with a secure and integrated data persistence policy. In addition, a pluggable Client/Server mode is employed to achieve flexible distributed extension. A series of experiments are conducted to show the effectiveness of our architecture. Compared with mainstream consortium blockchain storage architecture based on LevelDB, the average time-consuming decreases 81.85%/82.47% for reading/writing continuous data and 22.21%/48.99% for reading/writing state data. Compared with the storage architecture based on distributed database TiKV, the time-consuming decreases more significantly. This storage architecture has been integrated into the enterprise-level consortium blockchain platform Hyperchain, which has supported the efficient running of dozens of large-scale commercial blockchain projects with massive data.
Distributed energy trading has become an essential part of the energy trading market and provides a useful supplement to traditional centralized energy trading, but there are still problems such as opaque trading information and asymmetric user data. The blockchain technology has the advantages of traceability, trade openness, and data transparency, which is naturally suitable for distributed energy transactions. The electricity information data transmission represented by distributed energy transaction has the characteristics of real-time, which has a high-efficiency requirement on the selected blockchain technology. The consensus algorithm is the core of blockchain technology and affects the efficiency of the blockchain system. The efficiency of the existing consensus algorithms for energy transaction-oriented blockchain still needs to be improved. In this paper, a consensus resource slicing model(CRSM) is designed to meet the requirements of consensus efficiency in energy trading scenarios. Specifically, CRSM divides consensus nodes into different consensus domains for concurrent consensus, and the storage domain only stores block information without consensus. By building an experimental platform, the efficiency of CRSM was verified, the communication pressure of the blockchain system was reduced, and the consensus speed was effectively improved.
With the development of blockchain technology, participants need to have huge storage volumes to deal with the growing blockchain ledger size over time. This requirement leads to the conditional participation and verification of participants, thus weakening the decentralization of a blockchain system. Several compression schemes have been proposed to mitigate this storage problem by compressing a blockchain ledger based on redundancy, modular functions, and hash functions. However, these schemes have the limitation of accumulating the compression results to validate the retained blocks. The accumulation gradually reduces the storage volume for the blockchain ledger within the storage volume of nodes with limited resources, thus reducing the verification capability of the nodes. In this paper, a selective compression scheme using a checkpoint-chain is proposed to prevent the accumulation of compression results. The checkpoint-chain is a second blockchain that stores the checkpoints compressing existing blocks through a block Merkle tree. An update process is also proposed to prevent the accumulation of checkpoints by combining them. As numerous blocks can be verified with only a few updated checkpoints, blockchain nodes with limited resources can reduce the storage volume for the blockchain ledger and achieve high verification capabilities. Finally, compared with the existing compression schemes, the proposed scheme can achieve an average reduction in the storage overhead and an average increase in the verification capability of 76.02% and 13.90%, respectively. Moreover, the corresponding performance improvements are 86.14% and 15.44% when the update process is performed, respectively.
Blockchain or Distributed Ledger Technology (DLT) introduces a new computing paradigm that is viewed by experts as a disruptive and revolutionary technology. While bitcoin is the most well-known successful application of blockchain technology, many other applications and sectors could successfully utilize the power of blockchain. The potential applications of blockchain beyond finance and banking encouraged many organizations to integrate and adopt blockchain into existing or new software systems. Integrating and using any new computing paradigm is expected to affect the best practice and design principles of building software systems. Emerging blockchain-based applications require careful attention to many functional and nonfunctional requirements. One common practice in software engineering to handle potential pitfalls in software systems is using design patterns. Design patterns have been long used in software development to optimize the quality of software being developed. This research aims to determine the level of adoption of design patterns blockchain applications and their usefulness by analyzing the quality of the source code. This is achieved in a two-step process. Firstly, the quality of publicly available blockchain-based applications developed with design patterns is compared with applications without design patterns. In the next step, two versions of a blockchain-based application for cheque clearance are developed, with and without design patterns, and their quality and vulnerability to attacks are compared.
Blockchain's popularity has seen a historic rise over the last decade. However, existing blockchain systems have a major issue with scalability, which has become one of the main obstacles in technology's adoption in mainstream. There have been several attempts to address this limitation by identifying Blockchain's scalability/performance bottlenecks (e.g. those mainly related to consensus algorithms), and thus proposed different solutions (e.g., new consensus protocols) to address such limitations. Other works applied sharding to tackle the issue. All solutions however have mainly focused on Cryptocurrency applications, and thus addressing the scalability of blockchain systems for general applications remains a concern. This work proposes a scalable blockchain protocol for general applications (i.e., not restricted to Cryptocurrencies). To improve the two major factors affecting transaction scalability, namely throughput and latency, we needed to modify both the blockchain structure as well as the block generation process. ZyConChain, the proposed Blockchain system, introduces three types of blocks that form three separate chains: parentBlock, sideBlock and state block. These blocks are generated based on different consensus algorithms, as each algorithm has specific properties that make it suitable for each type of block. To improve the overall performance, ZyConChain generates sideBlocks (that carry transactions) at a high rate and keep them in a pool. To generate parentBlock, miners, instead of packing transactions into a block as they do in conventional blockchains, pack sideBlocks into a parentBlock. SideBlocks are generated based on an adapted Zyzzyva consensus protocol, with O(\log n) complexity. This has reduced the final consensus complexity per transaction, in comparison to previous work. To enable the protocol to scale out with the increase in the number of nodes, ZyConChain applied sharding technique. Parallel state chains have also been introduced to address cross-shard transactions.
Due to the rapid increase in the total amount of data generated in the world, the need for more computational resources is also increasing dramatically. This trend results in huge data centers and massive server farms being built around the world, which have a negative impact on global carbon emissions. On the other hand, there are many underutilized personal computers around the world that can be used towards distributed computing. To better understand the capacity of personal computers, we have conducted a survey that aims to find their unused computational power. The results indicate that the typical CPU utilization of a personal computer is only 24.5% and, on average, a personal computer is only used 4.5 hours per day. This shows a significant computational potential that can be used towards distributed computing. In this paper, we introduce ChainFaaS with the motivation to use the computational capacity of personal computers as well as to improve developers' experience of internet-based computing services by reducing their costs, enabling transparency, and providing reliability. ChainFaaS is an open, public, blockchain-based serverless platform that takes advantage of personal computers' computational capacity to run serverless tasks. If a substantial number of personal computers were connected to this platform, some tasks could be offloaded from data centers. As a result, the need for building new data centers would be reduced with a positive impact on the environment. We have proposed the design of ChainFaaS, and then implemented and evaluated a prototype of this platform to show its feasibility.
Blockchain is a publicly distributed ledger system that provides access to all records for everyone participating in the network. All the additions to the block are permanent and unchangeable. All major or minor changes are reported in a new block and cannot be reversed. Since the ledger is being distributed, there is no centralized authority. By eliminating the need for intermediaries, blockchain enables parties to trace transactions quickly and easily. The transactions occurring on a blockchain are transparent, reliable, authenticated and secured with the help of cryptography. The biggest advantage of the distributed ledger of blockchain is reduced operating costs. Blockchain is already being used by companies like IBM, Barclays, and Kodak etc. Blockchain can contain details of transactions for resources other than money such as land, automobiles, agricultural products etc. Any adjustment must be accepted by most people in the network, and this is achieved using Consensus algorithms. This paper discusses some of the core algorithms for consensus used in blockchain systems.
With smart contracts, a wide range of applications can be implemented on blockchains. Ethereum stores smart contract byte code with the smart contract ad-dress so, the Ethereum Virtual Machine (EVM) can read and execute transactions correctly. All executed transactions (both successful and failed transactions) are stored on the platform permanently. Failed transactions are thrown by the EVM due to runtime errors and result in monetary waste. The waste from these transactions add up to around 2 million Ethers or $634.2 million. In this thesis, we propose Evitar, a warning algorithm for reducing Ethereum smart contract runtime errors, which has two mechanisms. First, Evitar proposes that users send transactions with the maximum gas allowed to avoid Out of Gas errors. However, this results in an extremely high transaction fee when transactions fail. Second, Evitar analyzes transactions called to each method in smart contracts and marks a method as a method with a high failure rate if the number of failed transactions reaches Evitar’s threshold. This mechanism prevents users from sending and paying for transactions that are likely to fail. We run experiments to evaluate the performance of Evitar by replaying transactions in a private network. The results show that Evitar can reduce failed transactions up to 99.52% compared to sending under default behaviour in exchange for a reduction in successful transactions by 1.78%. The amount of gas used by Evitar is only one-tenth compared to sending under default behaviour. Sending transactions with the maximum gas in Evitar reduces Out of Gas errors by 99.25%. In addition, Evitar can save up to 15.04 GB (82.32%) of storage in the Geth default node and 50.09 GB (50.09%) in the Parity full archive node.
Distributed ledger technology is the driving force behind the blockchain technology and is proving its usefulness in various types of transaction processing systems. Fast, secure, reliable and efficient transactions are the key features of the blockchain based applications. A suitable or optimal size of block used by an application is dependent on the number of transactions in each block. Block size optimization is an important issue for any blockchain based application as it directly affects the performance of the application as scalability bottlenecks could prevent higher throughput and cause congestion. A larger block size will require higher transmission time compared to the smaller block size. A smaller block is more efficient but building too small a block will require higher block composition time to clear all the transactions. Both performance factors are contradictory to each other. An efficient blockchain network requires a suitable block size that demands lesser transmission time and block composition time. This paper proposes meta-heuristic algorithm based techniques for finding the suitable block size. It uses meta-heuristic algorithms to find the optimal number of transaction in each block. These algorithms are multi-objective particle swarm optimization and strength Pareto evolutionary algorithm. Experimental results reveal that the suitable block size is 213 transactions per block. Since size of a transaction is taken as 1.2 Kb, hence the results show that an optimal block size is of 255 Kbytes when network bandwidth of miners varies from 250 kbps to 1200 kbps. This shall achieve lower block transmission time and block composition time.
Roman Mühlberger, Stefan Bachhofner, Eduardo Castelló Ferrer, Claudio Di Ciccio · 7 authors
Blockchain has evolved into a platform for decentralized applications, with beneficial properties like high integrity, transparency, and resilience against censorship and tampering. However, blockchains are closed-world systems which do not have access to external state. To overcome this limitation, oracles have been introduced in various forms and for different purposes. However so far common oracle best practices have not been dissected, classified, and studied in their fundamental aspects. In this paper, we address this gap by studying foundational blockchain oracle patterns in two foundational dimensions characterising the oracles: (i) the data flow direction, i.e., inbound and outbound data flow, from the viewpoint of the blockchain; and (ii) the initiator of the data flow, i.e., whether it is push or pull-based communication. We provide a structured description of the four patterns in detail, and discuss an implementation of these patterns based on use cases. On this basis we conduct a quantitative analysis, which results in the insight that the four different patterns are characterized by distinct performance and costs profiles.
Blockchain technology is an emerging distributed ledger technology that has exploratory applications in many areas. The consensus algorithm, as the core module of the blockchain, has an important impact on the security, scalability, and efficiency of the blockchain network. The consensus algorithm is also a popular topic in current blockchain technology research. In existing consortium blockchains and public blockchains, the blockchain has low efficiency or poor fault tolerance because of the limitations of the consensus algorithm. To both ensure the fault tolerance of the blockchain and improve the scalability and throughput, in this paper, we propose a new type of consensus algorithm: mixed Byzantine fault tolerance (MBFT). MBFT uses sharding and layered technology. MBFT functionally partitions the nodes that participate in the consensus process and improves the scalability and efficiency without sacrificing security. MBFT also introduces a random node selection mechanism and a credit mechanism to improve security and fault tolerance. We analyze the security and experiment on transaction throughput in a real network environment. The results prove that MBFT has good security and scalability and high throughput.