Luciano Baresi, Giovanni Quattrocchi, Damian A. Tamburri, Luca Terracciano
The deployment and management of Blockchain applications require non-trivial efforts given the unique characteristics of their infrastructure (i.e., immutability) and the complexity of the software systems being executed. The operation of Blockchain applications is still based on ad-hoc solutions that are error-prone, difficult to maintain and evolve, and do not manage their interactions with other infrastructures (e.g., a Cloud backend). This paper proposes KATENA, a framework for the deployment and management of Blockchain applications. In particular, it focuses on applications that are compatible with Ethereum, a popular general-purpose Blockchain technology. KATENA provides i) a metamodel for defining Blockchain applications, ii) a set of processes to automate the deployment and management of defined models, and iii) an implementation of the approach based on TOSCA, a standard language for Infrastructure-as-Code, and xOpera, a TOSCA-compatible orchestrator. To evaluate the approach, we applied KATENA to model and deploy three real-world Blockchain applications, and showed that our solution reduces the amount of code required for their operations up to $82.7\%$.
The increasing number of security breaches in centralized systems provides the necessity to introduce decentralization in more fields. The Blockchain is a widely utilized decentralization technology that is implemented in various industries. Therefore, this technology can be used to protect sensitive services, such as those associated with the configuration changing of information systems. This article proposes a new protocol operating as a decentralization layer over any configuration scheme. It uses smart contracts—programs existing on the Blockchain—to keep track of configuration proposals and authorize new configurations. The configuration change can be proposed at any time. However, only once it is authorized by appropriate parties can it be introduced to the system. The new protocol provides an additional security layer, ensuring that every action is accounted for and authenticated. Furthermore, it enforces that administrators authorize every change. The protocol was designed to be flexible and easily adaptable to scenarios that did not use distributed ledger technology before. It uses the HTTP protocol with the JSON standard for protocol messages to allow easier adoption and transparency. The features of the proposed protocol were analyzed from a security point of view as well as from the financial perspective related to costs of using Blockchain technology. Security analysis shows that the protocol is resilient to the most common security risks that haunt state-of-the-art IT systems. Additionally, the authors proved that this solution could be implemented in both private and public Blockchains. A reference implementation was shared in a public repository. The proposed protocol was also compared with the most similar state-of-the-art work in the academic research highlighting the key differences and improvements.
Byzantine Fault-Tolerant (BFT) protocols are classical algorithms that offer a faster and more energy-efficient consensus mechanism compared to Proof-of-Work (PoW), which is typically used by cryptocurrencies such as Bitcoin. Synchronous BFT systems are hard to implement and vulnerable to attacks that aim to disrupt the synchrony of the system. Practical BFT (PBFT), which is a partially synchronous protocol, is a high-performance consensus algorithm that provides strong safety in the presence of a bounded number of faulty participants. Hotstuff is one such partially synchronous BFT State Machine Replication (SMR) protocol that aims to address the aforementioned issues. PBFT is becoming a popular choice for blockchain consensus, especially in permissioned systems (e.g. Ripple, Stellar, etc). However, it is not well understood how Hotstuff, and PBFT consensus in general, behave under varying conditions that are commonly found in blockchain networks. In this paper, we present a theoretical model for the Hotstuff consensus mechanism which accurately predicts blockchain-related metrics such as the transaction throughput and expected confirmation time using important networking parameters such as the number of replicas, link latency, and packet loss. Furthermore, we validate our model through extensive simulations carried out using OMNeT++. Our results show that Hotstuff performance degrades drastically when the number of replicas increases. We observe that with a maximum number of tolerable faulty nodes, when the number of validators is increased to 127, throughput tends to zero. As well, packet loss ratio and transaction processing time are two other factors that significantly affect the performance of Hotstuff.
Subhasish Goswami, Syed Muhammad Danish, Kaiwen Zhang
Blockchain smart contracts can only operate on data available on-chain, and face a major challenge of not being able to communicate with the world outside their own network. Blockchain oracles solve this problem by bridging the gap between on-chain and off-chain data. Chainlink is one of the most widely used decentralized oracle network with competing independent data providers with distinct characteristics in terms of price, performance, security, trust, etc. As a Chainlink service purchaser with unique a service level agreement (SLA) proposal for each job, a random selection of oracles to execute a certain job can result in sub-optimal solution, that could be alleviated by another oracle data provider. Therefore, in this work, we propose a middleware design to select the best data providers available in Chainlink oracle network based on individual job's service requirements. We model the oracle selection problem as a decision optimization problem and prove it to be NP-hard. We also propose two heuristic algorithms to approximate a solution to the modelled problem. We experimentally evaluate and compare the proposed design, and conclude that the proposed middleware architecture efficiently selects the oracles in terms of performance parameters.
Zuqiang Ke, Jongho Seol, Abhilash Kancharla, Nohpill Park
Since the invention of Bitcoin in 2008, there has been a surge in the number of blockchain networks with a variety of heterogeneous designs and functionalities. With the increasing number of blockchain applications and users, it becomes necessary to allow interoperability across isomorphic/heterogeneous blockchains, and further the interoperability is highly demanded in NFT (Non-Fungible Token)-to-NFT trading. This paper proposes a communication model across the blockchains, and an M/Cox/1 queueing model-based model. The cross chain model considers two distinct types of the communication such as atomic swaps and inter-ledger asset transfer. There are two types of communication controls in consideration, namely, Hashed TimeLock Contract (HTLC) for crossing isomorphic chains and Interledger Asset Transfer Protocol (IATP) for crossing heterogeneous chains. In the proposed performance model, a Poisson arrival process is assumed at a rate of λ, and two service rates are assumed to be exponentially distributed at a rate of µ1(asset swap / transfer Pre - Commit and verify) and µ2(transfer commit/rollback), respectively. Lastly, the selection ratio of a communication protocols between IATP and HTLC is assumed to be at a rate of$p$and ($1 -p$), respectively. Extensive numerical simulations are performed to study the impact of communication request arrival rates, communication service rate, communication traffic rates and proportion of the communication protocols on$L$(number of transactions in the system) and W(average waiting time in the system of transaction). This paper will establish a sound theoretical foundation to identify the interrelation and impacts between various design variables on the performance, and ultimately will reveal an optimal solution to a high performance design of cross chain across isomorphic /heterogeneous chains.
There is a natural tendency for many public blockchain systems to undergo forks. When they are resolved, they result in a chain reorganization (reorg) where the transactions from the side fork are discarded. This causes delays since clients are required to wait for more confirmations before processing transactions. In order to improve security, speed, and efficiency of any blockchain network, it is desirable to reduce the probability of forking as much as possible. For this purpose, it is necessary to have a thorough understanding of the behavior of blockchain systems in order to optimize parameters in accordance with this goal [1], [2]. This study proposes a new fork model that incorporates parameters not previously considered, such as network delay and validation degree. We have conducted several experiments to verify the validity of our proposed method, using the BlockSim simulator on the Ethereum network and EIP-1559. According to the results of this study, decreasing the validation degree and increasing the miners' marginal cost (as in EIP-1559) reduces the likelihood of a fork occurring by around 10 percent. Additionally, the experimental results validate the precision of our method in predicting the probability of forking.
Milan Todorović, Luka Matijević, Dušan Ramljak, Tatjana Davidović · 7 authors
Blockchains (BCs) are distributed database systems, popular for their innovative, unsupervised maintenance process. They use a so-called consensus protocol to prevent inference by any third party of absolute trust. Security, privacy, consistency, and energy consumption have been identified as the main issues involved in BC maintenance. According to the recent literature, some of these issues can be formulated as combinatorial optimization (CO) problems, and this fact motivated us to consider incorporating CO approaches into a BC. In this paper, we propose the new combinatorial optimization consensus protocol (COCP) based on the proof-of-useful-work (PoUW) concept that assumes solving instances of real-life CO problems. Due to the complexity of the underlying CO problems, we have developed various types of heuristic methods, which are utilized in the COCP. Most of these methods are problem-dependent stochastic heuristic or metaheuristic methods. As is the case with the majority of consensus protocols, PoUW exhibits the property of asymmetry. It is difficult to find a solution for the considered CO problem; however, once a solution is found, its verification is straightforward. We present here a BC framework combining the two above-mentioned fields of research: BC and CO. This framework consists of improvements aiming towards developing the COCP of the PoUW type. The main advantage of this consensus protocol is the efficient utilization of computing resources (by exploring them for finding solutions of real-life CO problem instances), and the provision of a broad range of incentives for the various BC participants. We enumerate the potential benefits of the COCP with respect to its practical impacts and savings in power consumption, describing in detail an illustrative example based on part of the real-life BC network. In addition, we identify several challenges that should be resolved in order to implement a useful, secure, and efficient PoUW consensus protocol.
Abstract Conditional payments allow the transfer of money only when pre-defined rules hold. Example uses could include welfare payments, employee expenses, insurance payouts, or tied donations. Normally, conditions are checked manually in reimbursement or pre-approval/audit processes, either at accounts before funds are distributed, or using account records after distribution. Blockchain’s capabilities for smart contract and digital assets can be used to implement next-generation conditional payments, on a decentralized ledger. We conducted a project with an industry partner where we conceptualized, implemented, and evaluated a novel programmable money concept using blockchain. In the system, programmed policies are not attached to accounts, but instead to money itself. Policies here specify the conditions when money may be spent, and can be automatically checked by the money as it is spent. Policies can also define auxiliary actions to be taken as part of payment transactions, including side-payments. Policies can be dynamically added to and removed from money as it flows through an economy. These policies could be budget rules for tied funds, but could also enable new forms of “values-based money” that respect ethical or other rules which relate to societal values or social norms. We report on some of our experiences and insights regarding blockchain architecture, software engineering with blockchain, and blockchain-based programmable money. We also identify opportunities and open research questions in these areas.
Sharding technique is viewed as the most promising solution to improving blockchain scalability. However, to implement a sharded blockchain, developers have to address two major challenges. The first challenge is that the ratio of cross-shard transactions (TXs) across blockchain shards is very high. This issue significantly degrades the throughput of a blockchain. The second challenge is that the workloads across blockchain shards are largely imbalanced. If workloads are imbalanced, some shards have to handle an overwhelming number of TXs and become congested very possibly. Facing these two challenges, a dilemma is that it is difficult to guarantee a low cross-shard TX ratio and maintain the workload balance across all shards, simultaneously. We believe that a fine-grained account-allocation strategy can address this dilemma. To this end, we first formulate the tradeoff between such two metrics as a network-partition problem. We then solve this problem using a community-aware account partition algorithm. Furthermore, we also propose a sharding protocol, named Transformers, to apply the proposed algorithm into the sharded blockchain system. Finally, trace-driven evaluation results demonstrate that the proposed protocol outperforms other baselines in terms of throughput, latency, cross-shard TX ratio, and the queue size of transaction pool.
Eder J. Scheid, Muriel Figueredo Franco, Fabian Kuffer, Niels Kubler · 6 authors
Network Functions Virtualization (NFV) has been a key part of evolving communication systems in the last few years. However, the life-cycle management of Virtual Network Functions (VNF) is still a not trivial task. Blockchains (BC), due to their decentralization and immutability characteristics, together with the automation provided by Smart Contracts (SC), can be employed to enable such automated and trustworthy VNF management.Thus, this paper proposes VeNiCE to automate the deployment and life-cycle management of VNFs using events emitted on SCs. VeNiCE provides automation and auditability by relying on a BC to provide a decentralized approach for VNF management, which performs management actions, such as VNF deployment and deletion, and based on events and communicates with an SC to provide immutable logging of the VNF life-cycle. VeNiCE provides (i) a frontend for user interaction, (ii) a backend implementing the communication with the NFV framework, and (iii) an SC that emits events, stores VNF allocations, and authenticates users. A prototype of VeNiCE was developed and deployed in the Ethereum BC using OpenStack Tacker as an NFV platform. Experiments were conducted in a real-world deployment of such a prototype to analyze the economic costs of using SCs and the time required to process requests by each component of VeNiCE and the BC. Those results obtained show VeNiCE’s feasibility, highlight its benefits achieved with the automation and provide insights on reducing costs by exploring additional BC platforms and different deployment types, which introduce centralization and management concerns.
Research and applications in Machine Learning are limited by computational resources, while 1% of the world's electricity goes into calculating 34 billion billion SHA-256 hashes per second, four orders of magnitude more than the 200 petaflop power of the world's most powerful supercomputer. The work presented here describes how a simple soft fork on Bitcoin can adapt these incomparable resources to a global distributed computer. By creating an infrastructure and ledger fully compatible with blockchain technology, the hashes can be replaced with stochastic optimizations such as Deep Net training, inverse problems such as GANs, and arbitrary NP computations.
Blockchain technology is a unique distributed ledger technology that has been widely used in various areas. With the increase in data on the blockchain and the append-only nature of the blockchain, the traditional blockchain’s full replica storage technique leads to blockchain storage scalability problem. Existing methods prioritize minimizing the storage strain on blockchain nodes while ignoring the availability of data, resulting in a lengthy average response time for users to access the blockchain. To address the shortcomings, this paper proposes an Information-Centric Networking-based blockchain storage architecture. The architecture uses the enhanced resolution system for community division to build blockchain node partitions and store blockchain ledgers in the underlying network. It introduces virtual chain for rapid blockchain indexing and adopts a collaborative block replica deletion algorithm across neighboring partitions, including replica number decision based on blockchain access decay characteristics and replica deletion based on resource relationship. Finally, we compare and analyze the proposed blockchain storage architecture with BC-store and KASARASA, and the results demonstrate that this architecture has significantly lower average access time than others. The replica data volume of this method is reduced by 57.2% compared to the full replica policy, but the access time is only 5.2% slower when compared to the full replica policy, which substantially increases the replica storage utilization.
Non-Fungible Tokens (NFTs) do hold the promise of providing Web3 with the opportunity for self-sovereignty of users' physical assets. However, existing NFT marketplaces lack a generic design that allows the value of assets to flow efficiently. In this paper, we propose a generic NFT architecture for Web3. The architecture supports the rapid development of the upper application environment and automated value mapping of the underlying physical asset environment. To connect these two environments, a generic connecter has been designed to provide flexible storage for mapping data management, and to support universal cross-chain transactions. With these features, the values of heterogeneous physical assets can coexist in a unified Web3 world, and rich value transfer services can be developed on demand. This paper discusses the background of the proposed architecture, the open problems and our initial solution, as well as our design principles and advantages, and finally validates this novel NFT architecture.
Sharding is the widely used approach to the trilemma of simultaneously achieving decentralization, security, and scalability in traditional blockchain systems. However, existing schemes generally involve problems such as uneven shard arithmetic power and insecure cross-shard transaction processing. In this study, we used the Practical Byzantine Fault Tolerance (PBFT) as the intra-shard consensus and, here, we propose a new sharding consensus mechanism. Firstly, we combined a jump consistent hash algorithm with signature Anchorhash to minimize the mapping of the node assignment. Then, we improved the process of the cross-shard transaction and used the activity of nodes participating in intra-shard transactions as the criterion for the shard reconfiguration, which ensured the security of the blockchain system. Meanwhile, we analyzed the motivation mechanism from two perspectives. Finally, through theoretical analysis and related experiments, we not only verified that the algorithm can ensure the security of the entire system, but also further clarified the necessary conditions to ensure the effectiveness of the shards and the system on the original basis.
Abstract In recent decades, the world has witnessed cloud computing as an essential technology that changes the traditional application Development and Operation (DevOps) lifecycle. However, current cloud software DevOps and Service Level Agreement (SLA) management often face challenges of 1) selecting the best fitting service providers, customizing services and planning capacities for large-scale distributed applications; 2) guaranteeing high-quality and trustworthy SLAs among multiple service providers; 3) enhancing the interoperability of cloud services across different providers; and 4) designing effective incentive models among stakeholders. This paper proposes a novel framework called Auction and Witness Enhanced trustworthy SLA for Open, decentralized service MarkEtplaces (AWESOME) to build a trustworthy cloud marketplace and address the above challenges. The proposed framework contains four subsystems: a customizable graphical user interface, an auction-based service selection model, a witness committee management mechanism, and a smart contract factory orchestration. We developed a prototype AWESOME decentralized application (DApp) based on the Ethereum blockchain. Extensive experiments are designed to evaluate the latency and cost of our model. The experimental results demonstrate that our model is economical and feasible.
In blockchain, the consensus algorithm is a core component that governs the trust among the participants in the blockchain activities. However, the exiting consensus algorithms suffer from performance bottleneck such as low throughput, high delay, unstable performance, sustainability issues and vulnerability to targeted attacks. In this paper, we propose a new consortium blockchain consensus algorithm, referred to as Weighted Byzantine Fault Tolerance (WBFT) consensus algorithm that improves system throughput and consensus delay. We introduce a dynamic weighting mechanism for consensus nodes, which enhances the security of blockchain system by weakening the influence of malicious nodes and reduces the probability of malicious behavior. We validate the performance of WBFT experimentally and compare it against Practical Byzantine Fault Tolerance (PBFT) and Reputation-Based Byzantine Fault-Tolerance (RBFT) based approaches. The results show that WBFT substantially outperforms PBFT and RBFT in terms of system throughput, consensus delay and security.
Threats towards information systems have continued to increase and become more sophisticated, making security approaches a necessity for all types of organizations to ensure their protection. To implement an appropriate computer security policy, it is necessary to efficiently exploit the data that has become a valuable asset for these security systems, provided it is well used, controlled and monitored.In this paper, we focus on developing a decentralized solution based on Blockchain technology and IPFS (InterPlanetary File System) that can maintain and ensure the integrity of log files and sensitive information. The obtained results are promising, we obtained a distributed ledger of all log file transactions in a chronological sequence, which was shared among all Ethereum participants, allowing us to verify the log files' integrity, validity, and auditability throughout their life cycle.
Wattana Viriyasitavat, Li Da Xu, Gaurav Dhiman, Zhuming Bi
Blockchain technology (BCT) has brought a paradigm shift to Business Process Management (BPM). BCT provides a trusted decentralized infrastructure to secure data and process executions using distributed ledgers and smart contract to manage complex business processes. Numerous efforts have been made to exploit BCT in supporting dynamic and trusted collaborations of business processes. This paper aims to understand recent BCT development for its BPM applications and identify the limitations and challenges for further development via a systematic literature review (SLR). It is found that numerous works have reported using BCT as technical solutions to fulfill some traditional BPM functions. This paper is distinguished from existing works, especially several relevant surveys in the sense that (1) the impact of using BCT in BPM is thoroughly explored to identify new constraints and challenges explicitly brought by blockchains; (2) the requirements for Business Process Compliance (BPC) are firstly analyzed in detail. Note that BPC is to assure the adherence of business processes to pre-defined policies, standards, specifications, regulations, and laws when business processes are executed. To fill the gaps of BCT applications in these two aspects, Blockchain-as-a-Service (BCaaS) is adopted in business process architecture, and the trends of BCT developments are identified accordingly.
Limited scalability and transaction costs are, among others, some of the critical issues that hamper a wider adoption of distributed ledger technologies (DLT). That is particularly true for the Ethereum blockchain, which, so far, has been the ecosystem with the highest adoption rate. Quite a few solutions, especially on the Ethereum side of things, have been attempted in the last few years. Most of them adopt the approach to offload transactions from the blockchain mainnet, a.k.a. Level 1 (L1), to a separate network. Such systems are collectively known as Level 2 (L2) systems. While mitigating the scalability issue, the adoption of L2 introduces additional drawbacks: users have to trust that the L2 system has correctly performed transactions or, conversely, high computational power is required to prove transactions correctness. In addition, significant technical knowledge is needed to set up and manage such an L2 system. To tackle such limitations, we propose 1DLT: a novel system that enables rapid and trustless deployment of an Ethereum Virtual Machine based blockchain that overcomes those drawbacks.
Nana Kwadwo Akrasi‐Mensah, Eric Tutu Tchao, Axel Sikora, Andrew Selasi Agbemenu · 8 authors
Since the inception of blockchain-based cryptocurrencies, researchers have been fascinated with the idea of integrating blockchain technology into other fields, such as health and manufacturing. Despite the benefits of blockchain, which include immutability, transparency, and traceability, certain issues that limit its integration with IIoT still linger. One of these prominent problems is the storage inefficiency of the blockchain. Due to the append-only nature of the blockchain, the growth of the blockchain ledger inevitably leads to high storage requirements for blockchain peers. This poses a challenge for its integration with the IIoT, where high volumes of data are generated at a relatively faster rate than in applications such as financial systems. Therefore, there is a need for blockchain architectures that deal effectively with the rapid growth of the blockchain ledger. This paper discusses the problem of storage inefficiency in existing blockchain systems, how this affects their scalability, and the challenges that this poses to their integration with IIoT. This paper explores existing solutions for improving the storage efficiency of blockchain–IIoT systems, classifying these proposed solutions according to their approaches and providing insight into their effectiveness through a detailed comparative analysis and examination of their long-term sustainability. Potential directions for future research on the enhancement of storage efficiency in blockchain–IIoT systems are also discussed.
In this paper, an efficient data structure for storage, management, and security in blockchain systems is presented. This efficient structure is based on the AVL (Adelson-Velsky and Landis) tree and make an extension for the purpose of management and security. We first present a new storage structure for efficient data search based on the AVL tree. Next we expand this data structure and apply to the management and security of the blockchain ledger. The way of management for distributed account/data is divided into two operations, namely splitting and merging. This paper also makes a discussion about the significance of these two operations. We show a detailed description and make mathematical analysis with proof for the performance of all mechanisms proposed in this paper. In addition, a mechanism of dual authentication is also proposed and to provide a better tamper-proof.
In blockchain (BC) systems, smart contracts (SCs) often use a transaction-driven execution model. However, real-world financial applications are complex, and often driven by events instead. This paper presents an intelligent event-driven framework to automatically trigger SC execution by collecting event information, and classifying these events, and analyzing various relationship among these events, and use a service-model for SCs to register interested events so that when the concerned event happened, they can be automatically triggered. This paper uses oracle machines (OMs) to collect event information, EEG (Event Evolution Graph) to analyze relationship among events. This paper then uses multi-layer perceptron model to evaluate the design. This paper proposes a new method to solve the scalability and performance challenges in the SC ecosystem, which shows that the event-driven execution model would be more intelligent.
Energy consumption of consensus mechanisms used in permissionless distributed ledger, such as Bitcoin and Ethereum, has become a popular research topic. Computation and storage operations combined with proof of work (PoW) to prevent attacks requires a lot of energy consumption. Due to the permissionless nature of blockchain, it is difficult to measure the energy consumed by each node. Therefore, estimation methods provide approximations such as lower and upper bounds on energy consumption. A recent work in this direction has shown that PoW is the most energy consuming consensus. In this context, there is a timely requirement to find solutions to optimize the energy consumption. Our proposal aims at building a typical consensus in distributed ledger with an asynchronous protocol to reduce wasted computations involved in the proof of work. For this purpose, we rely on a similarity search index to prevent double-spending attacks and reduce the difficulty mining involved in the PoW, by exploring how it influences the number of required iterations needed to solve the PoW.