Yunming Xiao, Sarit Markovich, Aleksandar Kuzmanovic
Having enabled numerous applications, blockchains have attracted not only much attention, in the past decade, but also huge amount of resources: talent, capital, energy, etc. Focusing on the mining side of the market, in this paper, we aim at understanding how to efficiently use the resources mining and staking pools attract. We start with developing predictions about factors that increase the efficient allocation of pools' resources. We then test our predictions based on a general model for optimal resource allocation that we develop, as well as data we collected on pools' actual resource allocations. We find that pools can increase resource efficiency by mining for more blockchains as well as by increasing the frequency of resource re-allocation. Further, we enroll to mining pools as a miner to understand and comment on how pools can encourage their miners to increase the efficiency of their allocation. While our empirical investigation mostly focuses on the BTC family, we show that our theory and results are general and applicable to the Ethereum family as well as other proof-of-work (PoW) and proof-of-stake (PoS) chains.
Michael Sober, Marten Sigwart, Philipp Frauenthaler, Christof Spanring · 6 authors
Abstract Today, several solutions for cross-blockchain asset transfers exist. However, these solutions are either tailored to specific assets or neglect finality guarantees that prevent assets from getting lost in transit. In this paper, we present a cross-blockchain asset transfer protocol that supports arbitrary assets, is adaptable to different means of cross-blockchain communication, and adheres to requirements such as finality. The ability to freely transfer assets between blockchains may increase transaction throughput and provide developers with more flexibility by allowing them to design digital assets that leverage the capacities and capabilities of multiple blockchains. We define the general requirements and specifications for a cross-blockchain asset transfer protocol and provide a proof-of-concept implementation for EVM-based blockchains. Further, we evaluate the protocol concerning costs, transfer duration, and security.
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.
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.
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.
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.
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.
Thomas Lavaur, Jérôme Lacan, Caroline Ponzoni Carvalho Chanel
The Internet of Things includes all connected objects from small embedded systems with low computational power and storage capacities to efficient ones, as well as moving objects like drones and autonomous vehicles. The concept of Internet of Everything expands upon this idea by adding people, data and processing. The adoption of such systems is exploding and becoming ever more significant, bringing with it questions related to the security and the privacy of these objects. A natural solution to data integrity, confidentiality and single point of failure vulnerability is the use of blockchains. Blockchains can be used as an immutable data layer for storing information, avoiding single point of failure vulnerability via decentralization and providing strong security and cryptographic tools for IoE. However, the adoption of blockchain technology in such heterogeneous systems containing light devices presents several challenges and practical issues that need to be overcome. Indeed, most of the solutions proposed to adapt blockchains to devices with low resources confront difficulty in maintaining decentralization or security. The most interesting are probably the Layer 2 solutions, which build offchain systems strongly connected to the blockchain. Among these, zk-rollup is a promising new generation of Layer 2/off-chain schemes that can remove the last obstacles to blockchain adoption in IoT, or more generally, in IoE. By increasing the scalability and enabling rule customization while preserving the same security as the Layer 1 blockchain, zk-rollups overcome restrictions on the use of blockchains for IoE. Despite their promises illustrated by recent systems proposed by startups and private companies, very few scientific publications explaining or applying this barely-known technology have been published, especially for non-financial systems. In this context, the objective of our paper is to fill this gap for IoE systems in two steps. We first propose a synthetic review of recent proposals to improve scalability including onchain (consensus, blockchain organization, …) and offchain (sidechain, rollups) solutions and we demonstrate that zk-rollups are the most promising ones. In a second step, we focus on IoE by describing several interesting features (scalability, dynamicity, data management, …) that are illustrated with various general IoE use cases.
Due ecosystem, it is common for new blockchains to fork or partially reuse the code of classic blockchains. For example, the popular Dogecoin, Litecoin, Binance BSC, and Polygon are all variants of Bitcoin/Ethereum. These “forked” blockchains thus could encounter similar vulnerabilities that are propagated from Bitcoin/Ethereum during forking or subsequently commit fetching. In this paper, we conduct a systematic study of detecting and investigating the propagated vulnerabilities in forked blockchain projects. To facilitate this study, we propose BlockScope, a novel tool that can effectively and efficiently detect multiple types of cloned vulnerabilities given an input of existing Bitcoin/Ethereum security patches. Specifically, BlockScope adopts similarity-based code match and designs a new way of calculating code similarity to cover all the syntax-wide variant (i.e., Type-1, Type-2, and Type-3) clones. Moreover, BlockScope automatically extracts and leverages the contexts of patch code to narrow down the search scope and locate only potentially relevant code for comparison. Our evaluation shows that BlockScope achieves good precision and high recall both at 91.8% (1.8 times higher recall than that in the state-of-the-art ReDeBug while with close precision). BlockScope allows us to discover 101 previously unknown vulnerabilities in 13 out of the 16 forked projects of Bitcoin and Ethereum, including 16 from Dogecoin, 6 from Litecoin, 1 from Binance BSC, and 4 from Optimism. We have reported all the vulnerabilities to their developers; 40 of them have been patched or accepted, 66 were acknowledged or under pending, and only 4 were rejected. We further investigate the propagation and patching processes of discovered vulnerabilities, and reveal three types of vulnerability propagation from source to forked projects, as well as the long delay (mostly over 200 days) for releasing patches in Bitcoin forks (vs. ∼100 days for Ethereum forks).
Accounting Information System (AIS), which is the foundation of any enterprise resource planning (ERP) system, is often built as centralized system. The technologies that allow the Internet-of-Value, which is built on five aspects that are network, algorithms, distributed ledger, transfers, and assets, are based on blockchain. Cryptography and consensus protocols boost the blockchain platform implementation, acting as a deterrent to cyber-attacks and hacks. Blockchain platforms foster innovation among supply chain participants, resulting in ecosystem development. Traditional business processes have been severely disrupted by blockchains since apps and transactions that previously required centralized structures or trusted third-parties to authenticate them may now function in a decentralized manner with the same level of assurance. Because a blockchain split in AIS may easily lead to double-spending attacks, reducing the likelihood of a split has become a very important and difficult research subject. Reduced block relay time between the nodes can minimize the block propagation time of all nodes, resulting in better Bitcoin performance. In this paper, three problems were addressed on transaction and block propagation mechanisms in order to reduce the likelihood of a split. A novel algorithm for blockchain is proposed to reduce the total propagation delay in AIS transactions. Numerical results reveal that, the proposed algorithm performs better and reduce the transaction delay in AIS as compared with existing methods.
Ertem Nusret Tas, David Tse, Fangyu Gai, Sreeram Kannan · 6 authors
Bitcoin is the most secure blockchain in the world, supported by the immense hash power of its Proof-of-Work miners. Proof-of-Stake chains are energy-efficient, have fast finality but face several security issues: susceptibility to non-slashable long-range safety attacks, low liveness resilience and difficulty to bootstrap from low token valuation. We show that these security issues are inherent in any PoS chain without an external trusted source, and propose a new protocol, Babylon, where an off-the-shelf PoS protocol checkpoints onto Bitcoin to resolve these issues. An impossibility result justifies the optimality of Babylon. A use case of Babylon is to reduce the stake withdrawal delay: our experimental results show that this delay can be reduced from weeks in existing PoS chains to less than 5 hours using Babylon, at a transaction cost of less than 10K USD per annum for posting the checkpoints onto Bitcoin.
Blockchain is a distributed ledger technology that has recently gained widespread popularity. Many industries have started to implement blockchain solutions for their application and services. Blockchain provides immutability, privacy, security, and transparency. There is no central authority to validate and verify the transactions, still, every transaction in the Blockchain is considered secure and verified. This is made possible by the use of a consensus algorithm which is a core part of any Blockchain network. Different consensus algorithms exist and the selection of appropriate consensus algorithms can affect the performance of the blockchain. This paper presents a pattern for one of the most commonly used blockchain consensus algorithms, which is the Proof of Stake (PoS) algorithm. This pattern describes its architecture, including its structure and dynamics.
Electric Vehicles (EVs), as well as the number of applications for their management, are rapidly increasing due to the fact that Internet of Vehicles (IoV) becomes more informative and industrialized. According to the literature, IoV requires decentralization towards the energy Demand Response (DR) management, with secure energy trading, efficient charging scheduling, and incentives for making the drivers to participate. Blockchain and Distributed Ledger Technologies (DLTs) can be used to enable a foundational environment to support DR management. However, and to the best of our knowledge, none of the existing research works discussed in the literature adopts a holistic approach to address them. As such there is a demand for exploring a unified blockchain-based framework for distributed DR management. Therefore, the aim of this work is focused on the blockchain adoption in IoV-assisted smart cities. More specifically, we propose a blockchain based approach, to be used for building a secure and user-centric DR management framework. Our proposition aims to address the DRP in IoV through charging scheduling based on the generation of EV driving profiles, and optimal Vehicle-to-Vehicle/Grid (V2V | V2G) energy trading.
Smart contracts provide the means to stipulate rules of interaction between mutually distrustful organizations. They encode contractual agreements on the basis of source code, which else need to be contractualized in natural language. While the mediation of contractual agreements via smart contracts is seamless in theory, it requires that the conditions of an interaction are accurately made available in the blockchain. Time is a prominent such condition. In the paper at hand, we empirically measure the consistency of a smart contract to yield equal results on the basis of the time of an interaction and its potentially inaccurate representation in the blockchain. We propose a novel metric called execution accuracy to measure this consistency. We specifically measure the execution accuracy of a time intervalconstrained smart contract that executes distinct logic within and without some constraint interval. We run experiments for the local Ganache and Quorum and the public Görli and Rinkeby Ethereum blockchains. Our experiments confirm our intuition that execution accuracy decreases near interval bounds. The novelty of our proposed metric resides in its capacity to quantify this decrease. We demonstrate how time constraints can be effectively stipulated on the basis of execution accuracy measurements.