Abstract Decentralized storage of data is one of the typical applications in the blockchain network. However, most of the existing works neglected the storage balancing problem in the blockchain network, which has an immediate impact on the availability and stability of the network. Therefore, this paper proposes a storage balancing problem for non-local data storage in the blockchain network and proves that the problem is non-deterministic polynomial (NP)-hard. The criterion of the storage balance is established by a balanced coefficient in the proposed scheme. A heuristic matching algorithm (HMA), a genetic algorithm (GA) and a tabu search algorithm (TSA) are customized to solve the problem of imbalanced storage formalized in this paper. Compared with our previous algorithm fast matching algorithm (FMA), experimental results demonstrate that HMA achieves better performance in terms of accuracy, computation overhead and storage overhead. Specifically, the computation overhead of HMA is lower than that of FMA by 84.45% on average, whereas the storage overhead of HMA is lower than that of FMA by 32.26% on average. By using the initial solution of HMA, TSA achieves the highest accuracy among GA, TSA and moth-flame optimization (MFO). Meanwhile, by using the initial solution of FMA, TSA achieves the highest accuracy among GA, TSA and MFO.
This paper proposes a decentralized framework for the orchestration of Cloud Services using heterogeneous resources residing in the homes of private individuals or small-scale clusters. The framework makes use of Ethereum Smart Contracts to provide a decentralized mechanism for discovering the different interfaces exposed by Cloud Components. The paper introduces a novel concept of Component Administration Networks, which are peer-to-peer networks that monitor and ensure the availability of the software components. The concept applied for the Orchestration process to ensure that the deployment of an Application continues in the presence of Orchestrator component failure. Checkpoints are used to address the continuity of the Management components, in general, and of the Orchestrator, in particular. In our proposal, checkpoint metadata is stored in a Smart Contract to assess the execution time of a Service to reimburse the participants that ensure its execution.
Digital finance encompasses digital information feedback on credit credibility and electronic transactions based on digital currencies.In recent years, driven by blockchain technology and cloud computing, digital finance has boomed in developed countries, giving rise to new issues and potential risks.With the transformation of digital finance from 'crypto' to 'cloud', a new trend is emerging.Digital finance driven by cloud computing, whether on public clouds or on-chain clouds, offers a plethora of opportunities, but the migration to native digital finance systems based on cloud infrastructure would be fraught with risk.Cloud computing, with its convenience, flexibility, security and scalability, continues to become a mainstream technology in retail finance.Multi-modal federated machine learning and federated cloud transactions can potentially construct a decentralized market with permissioned access while achieving snapshot privacy.Blockchain will continue its widespread adoption in developer-centric financial backends as technology matures, with larger public chains evolving to handle benchmark trading volumes.On miniambilest, native public and enterprise banks, decentralized exchanges, NFT-backed loans and on-chain credit scores will rise, creating liquidity for illiquid assets and granting borrowing access to previously excluded participants.The rising popularity of cryptocurrencies may, on the contrary, accelerate KYC, AML and the adoption of CBDCs.Security issues in cloud computing may cause significant financial losses, as there have been cases in the past where public cloud services have suffered data breaches.In some cases, thousands of GB of customer financial and transaction data have leaked online and caused significant reputational damage, emphasizing the importance of choosing a reliable cloud service vendor [2].Observations made during web scraping consisting of an analysis of exchange user cases showed that data breaches have exposed customer account information, previous transactions, and even 3D model photos of the vault and keys used to hide hardware wallets in a bank deposit facility.Furthermore, the archive and backup of large-scale retail finance databases in the public cloud may incur long data retrieval delay of over 100ms.The lost backup can also put the entire institution at risk if the vendor service becomes bankrupt, or if a natural disaster damages their facilities.Despite the rapid year-on-year growth of this new financial market, currently, only limited assets, such as the Bitcoin reward for blockchain mining, can be traded on-chain.
Blockchain is a technology for storing an immutable history of transactions in a decentralized platform by using cryptographic principles. Many industries have become interested in adopting blockchain within their IT systems. However, the accessibility, privacy, performance, and scalability aspects of different blockchain-based platforms are still legitimate concerns when designing an enterprise solution. Permissioned blockchain frameworks facilitate a way to immutably store confidential records. Numerous research studies have been carried out on the opportunities, challenges, application areas, and performance analysis of different public and permissioned blockchain-based platforms. However, the implication of blockchain in recent private enterprise solution requires detailed comparative analysis. This paper conducts a performance and scalability analysis of popular private blockchain platforms, including Ethereum (private deployment), Quorum, Corda, and Hyperledger Fabric. Each of these platforms is assessed by varying the workloads (no. of transactions and nodes) and determining the performance evaluation metrics such as throughput and network latency.
Andrea Lisi, Andrea De Salve, Paolo Mori, Laura Ricci
Recommender Systems are very popular tools within the online community, suggesting to their users a big variety of items like products, videos, music and locations to visit. Moreover, users actively populate these systems sending and reading opinions under the form of reviews, and potentially obtaining a reward for their activities. However, such systems typically rely on a central authority that acts as a trusted party having total control over the system. Decentralized Recommender Systems have been proposed to solve such issue distributing the control and responsibility on the hands of their users, but leading to risks in case of disputes or misbehaviour. Based on a general architecture of a Decentralized Recommender System, in this paper we identify the potential unfair exchanges that may rise during the activity between two users, and we propose a solution based on the concept of atomic swaps inherited from the blockchain technology. Finally, we provide an attack model to show that the proposed solution creates fair processes.
Pooled mining is the de facto mining pattern in public, PoW (Proof of Work) based blockchain systems like Bitcoin and Ethereum. Mining pool aggregates discrete miners’ computation power to improve probability of getting the right block, and stabilize miners’ rewards. Miners reach consensus among pools, and maintain the whole blockchain network's stability. Due to architecture constrains across underlying transmission mechanism, computation power differences among nodes, and consensus algorithms, mining pools are facing increasing performance challenges, which lead to wastes of computing resources and loss of miners’ rewards. Based on analysis of mining pool architecture, this paper proposed a numerical model MENM (Miner Efficiency Numerical Model) to measure miner's computing efficiency, and a performance tuning mechanism DDCT (Dynamic Difficulty Calculation and Tuning) to dynamically adjust individual miner's difficulty in a pool based on MENM value, to improve mining pool's efficiency. The proposed tuning mechanism is also tested against a small experimental PoW mining pool to validate its effect.
Blockchain is a distributed, append-only digital ledger (database). The technology has caught much attention since the emergence of cryptocurrency, and there is an increasing number of blockchain applications in a wide variety of businesses. The concept, however, is still novel to many members of the simulation and operations research community. In this tutorial, we introduce the blockchain technology and review its frontier operations-and-data-related research. There are exciting opportunities for researchers in simulation, system analysis, and data science.
In recent years, blockchain is experiencing a rapid development and has the huge potential of revolutionizing the information platform in the deposit application field. In this paper, a blockchain based credible e-bidding system (BCES) is presented to address operational compliance, multi-party coordination, and cybersecurity problem in the process of distribution, verification and backtracking of bidding data files. BCES is comprised of basic configuration management, contract business deployment, data service processing, system service support, data visualization. Through detailed design of a set of blockchain integration and transformation mechanism for bidding business, different stakeholders are connected together with the help of the alliance blockchain, forming a flat trust management model. The experiments demonstrate that the average TPS of BCES is stable at around 2600-2800, and the response time of the blockchain deposit platform is within the acceptable time range of 3s, and the error rate is very low. Currently, BCES has been deployed and applied in China Telecom Corporation and has achieved remarkable results.
Nowadays, as student e-portfolio systems increase in popularity, the large storage space and convenient retrieval of e-portfolio system provide a more efficient way for heavy file management, while the security concerns about personal information and privacy of students arise. The traditional student e-portfolio system adopts a centralized system which caused some problems such as an organization that has full control over the information that could tamper with the database, the insecurity of student e-portfolio. However, blockchain application has mushroomed, providing opportunities for solving the shortcomings proposed above. In this paper, we combine with the fabric blockchain technology to implement student e-portfolio system for permanently recording student growth information, which uses smart contract to realize the registration and authentication of student identity, the portfolio recording and management, the publication of learning evaluation. Finally, we analyze the system compared with traditional system, and the comparative result indicates that the proposed system can not only effectively manage student information, but also protect privacy.
Blockchain is a promising new technology, generating widespread interest, and receiving considerable attention in the research community, such as academia and industry. This interest started with the success of Bitcoin but took speed with the promise of smart contracts and a vast number of applications. While there is a broad interest in developing blockchain systems for specific use cases, there is a lack of tools to perform their evaluation and implementation decisions may hamper fast progress. This report provides the review of security and performance of public and private blockchain framework, where each of which is represented by the two well-known papers, the first is titled “On the Security and Performance of Proof of Work Blockchains” and the second paper is titled “BLOCKBENCH: A Framework for Analyzing Private Blockchains”. The first paper introduces a novel quantitative framework to analyze the security and performance implications of various consensus and network parameters of PoW blockchains. The framework allows for capture existing PoW-based deployments as well as PoW blockchain variants that are instantiated with different parameters, and to objectively compare the tradeoffs between their performance and security provisions. In the second paper, the authors describe BlockBench, the first evaluation framework for analyzing private blockchains. BlockBench measures overall and componentwise performance in terms of throughput, latency, scalability, and fault-tolerance. Next, BlockBench is used to conduct a comprehensive evaluation of three major private blockchains: Ethereum, Parity, and Hyperledger Fabric. Furthermore, there are gaps in performance among the three systems which are attributed to the design choices at different layers of the blockchain’s software stack.
Lukas König, Yuliia Korobeinikova, Simon Tjoa, Peter Kieseberg
Since the introduction of Bitcoin, the term “blockchain” has attracted many start-ups and companies over the years, especially in the financial sector. However, technology is evolving faster than standardization frameworks. This left the industry in the position of having to use this emerging technology, without being backed by any international standards organization regarding for neither the technology itself, nor for a blockchain specific information security framework. In times of the General Data Protection Regulation and growing international trade conflicts, protecting information is more relevant than ever. Standardization of blockchains is an appeal to raise the development of information technologies to the next level. Therefore, this paper shall provide an overview of standardization organization’s publications about blockchains/distributed ledger technologies, a set of comparison criteria for future work and a comparison of the existing standards work itself. With that information, aligning to existing standardization efforts becomes easier, and might even present the possibility to create frameworks where there are none at the moment.
Beyond an emerging popular web applications runtime supported in almost all commodity browsers, WebAssembly (WASM) is further regarded to be the next-generation execution environment for blockchain-based applications. Indeed, many popular blockchain platforms such as EOSIO and NEAR have adopted WASM-based execution engines. Most recently, WASM has been favored by Ethereum, the largest smart contract platform, to replace the state-of-the-art EVM. However, whether and how well current WASM outperforms EVM on blockchain clients is still unknown. This article conducts the first measurement study to understand the performance on WASM VMs and EVM for executing smart contracts for blockchain-based applications. To our surprise, the current WASM VM does not provide expected satisfactory performance. The overhead introduced by WASM is really non-trivial. Our results shed the light on challenges when deploying WASM in practice, and provide insightful implications for improvement space.
The Distributed Ledger Technology (DLT) is a peer-to-peer model of sharing data among collaborating parties in a decentralized manner. An example of DLT is a blockchain where data form blocks in an append-only chain. Software architecture description usually comprises multiple views. The paper concentrates on the Deployment view of the DLT solution within the 1+5 architectural views model. The authors have proposed Unified Modeling Language (UML) extensibility mechanisms to describe the needed additional semantic notation to model deployment details. The paper covers both the network and node levels. The proposed stereotypes and tagged values have enriched UML Deployment diagram. We have gathered those modeling elements in dedicated UML Profile for Distributed Ledger Deployment. We have applied the profile to model Deployment view of a renewable energy management system that uses R3 Corda framework. The system records information about inbound and outbound energy to/from renewable energy grid.
Off-chain payment channel is a significant technology to improve transaction performance of blockchain by enabling two blockchain nodes to conduct micro-payments at high frequency without committing all of the transactions on the blockchain, ensuring the “instant finality” of transactions, reducing transaction costs and improving the scalability of the blockchain. Among different types of blockchains, the transaction performance of consortium blockchain is better than that of public blockchain, thus the application of state channel technology in consortium blockchain will further improve the transaction throughput. However, as far as we know, there seems to be seldom existing work in this aspect. A critical challenge is that the existing work applies the state channel technology only in the public blockchain system, and there are many differences between the consortium and public blockchain system in terms of architecture, application scenarios and privacy, etc., leading to certain technical thresholds for migration of the state channel technology. In this paper, we address this challenge by designing CBOP, an off-chain payment service that can interact with the consortium blockchain infrastructure of the Hyperledger Fabric. CBOP can carry out on-chain or off-chain transactions according to the demand of both parties, and provide strong security to protect against malicious attacks. It implements these benefits through two novel designs, dynamic partitioning algorithm for transactions and trusted security guarantee for off-chain payments. Experimental results show that CBOP can provide 300 % more transaction throughput than original design.
Currently, all blockchain-based applications conduct two primary operations, i.e., writing data on blockchain networks and reading these data from the networks. These tasks require users to have considerable knowledge in blockchain technology, and they become even more challenging if users want to utilize different blockchain platforms to write and read data. So far, we have not had a uniform mechanism to perform write and read operations on various blockchain platforms. In addition, writing a huge amount of data on blockchain networks is a time-consuming task and requires considerable transaction fees. To address these issues, we present in the paper a data mapping language named BML. BML allows developers to uniformly define mappings for data transformation from traditional data storage mechanisms into blockchain networks. Conversely, this language also assists users in reading transformed data. Currently, BML accepts five input data sources, including XML, JSON, XLSX, SQL (relational database), NoSQL, and supports two output platforms, including Hyperledger Sawtooth and Ethereum.
Evaluating Blockchain performance is not an easy task. It is difficult to compare different systems, since the evaluation is often incomprehensible and conducted in different environments with distinct workloads. Only a handful of prior tools were proposed, e.g., BLOCKBENCH and HFBench. Unfortunately, these tools have several limitations. We first identify these limitations. Second, motivated by our observations, we then present a benchmarking tool, Boston Blockchain Benchmarking (BBB). BBB is configurable, extensible, and easy-touse. In particular, BBB can be used to test Blockchain from a networking perspective, a feature that we have not observed in prior tools. Similar to BLOCKBENCH, we focus on the private Blockchain. Concretely, we integrate our tool with Mininet, and provide a simple mechanism to test how network properties (e.g., latency, bandwidth, package loss rate) affect the performance of the chosen Blockchain. We present our preliminary result of evaluating Ethereum. We stress that the architecture of BBB is general, and could be extended to other Blockchain systems. BBB is extremely lightweight and can be used on your laptop to test a small network. Such a feature allows quick evaluation of the Blockchain and speeds up innovation and development.
Saeideh G. Motlagh, Jelena Mišić, Vojislav B. Mišić
Compact block protocol aims to reduce bandwidth usage and, possibly, latency in the Bitcoin network. In this work, we present an analytical model to evaluate the impact of churning nodes on the Bitcoin network when the compact block protocol is used. We use a Continuous Time Markov Chain to model wake-up and sleeping behavior of each node in the network. We also calculate synchronization time, including transaction deficit recovery, when a node rejoins the network. When a node is absent from the network, it misses blocks mined during its absence but also some of the transactions which may be omitted from the subsequent compact blocks. Our results indicate that synchronization time takes more than a minute when node is away from the network for several hours. Moreover, the majority of synchronization time is spent on block verification and transaction deficit recovery.
Blockchain technology has gained wide acceptance in recent years. Smart contracts facilitate the application of the blockchain technology. Smart contracts are programs running distributed environments and are thus error prone. Smart contracts often lack precise specifications and are written in high-level programming languages such as Solidity. In this paper, we present an approach to formally model and analyze smart contracts using predicate transitions nets. We use the blind auction smart contract to demonstrate our approach, which reveals some problematic implementation of some smart contract functions. We have applied predicate transition nets in modeling and analyzing all 11 smart contracts in Azure blockchain workbench. Although we cannot tell whether there is any problem in these smart contracts based on their informal descriptions and Solidity programs without designer input. Our experience has shown the applicability and suitability of predicate transition nets. We believe that our approach can help smart contract designers to detect and prevent early design problems in the current practice of using informal textual descriptions of smart contracts.
The storage structure on the data block of the current blockchain systems is still a linked list. This traditional structure is one-way and is not efficient for query operation. In view of this, we proposed a novel searching structure based on a height balanced Binary Search Tree (BST). The data structure we proposed not only retains the characteristics of the traditional ledgers but also adds the function of quick query. Through the new data structure, we can quickly find the starting position of the search and start searching for all transaction records within a specified range of time from this position. We also made an analysis and comparisons in the final.
Nowadays audit profession is faced with an excessive evolution of the information and communication technology (ICT). The effects of ICT on auditing are dual. On the one hand, auditing is faced with the digitalization of companies’ business operations, and on the other, auditors must be able to adapt their methodologies to these changes in order to be able to audit implemented ICT in the companies’ business operations. One of the latest ICT innovations includes the application of blockchain technology (BCT) in different business operations of a company, which represents the object of auditing. In order to audit BCT, auditors must apply appropriate audit procedures, whereas analytical procedures (APs) represent the most useful one. The subjects of this paper are external and internal auditors, and their application of APs for auditing implemented BCT in the companies’ business operations, in Croatia. Therefore, the main objective of this paper is to investigate the differences in the APs’ application and its usefulness for auditing BCT, as an emerging ICT, between external and internal auditors. To investigate the main objective of the paper, desk research and survey research were conducted. Overall results indicated that external and internal auditors in Croatia are aware that auditing BCT requires the application of advanced APs, for what they need to possess excellent knowledge about APs and BCT. Obtained results showed that auditors in Croatia possess below-average knowledge about APs and BCT. Therefore, the necessity for specialized education of external and internal auditors is inevitable. Regarding the investigation of differences in the readiness to audit BCT between external and internal auditors in Croatia, the results confirmed that external auditors are more ready to audit BCT than internal auditors. Finally, research results confirmed that the application of advanced APs in audit engagements will increase the efficiency and effectiveness of companies’ business operations supported by the BCT.