Blockchain is a new technology for processing complex and disordered information with respect to business and other industrial applications. This work is aimed at studying the consensus algorithm of blockchain to improve the performance of blockchain. Despite their advantages, the proof of stake (POS) algorithm and the practical Byzantine fault tolerance (PBFT) algorithm have high latency, low throughput, and poor scalability. In this paper, a blockchain hybrid consensus algorithm which combines advantages of the POS and PBFT algorithms is proposed, and the algorithm is divided into two stages: sortition and witness. The proposed algorithm reduces the number of consensus nodes to a constant value by verifiable pseudorandom sortition and performs transaction witness between nodes. The algorithm is improved and optimized from three dimensions: throughput, latency, and scalability. The experimental results show that the improved hybrid consensus algorithm is significantly superior to the previous single algorithms for its excellent scalability, high throughput, and low latency.
An increasing number of industries rely on Internet-of-Things devices to track physical resources. Blockchain technology provides primitives to represent these resources as digital assets on a secure distributed ledger. Due to the proliferation of blockchain-based assets, there is an increasing need for a generic mechanism to trade assets between isolated platforms. To date, there is no such mechanism without reliance on a trusted third party. In this work, we address this shortcoming and present XChange. Unlike existing approaches for decentralized asset trading, we decouple trade management and the actual exchange of assets. XChange mediates trade of any digital asset between isolated blockchain platforms while limiting the fraud conducted by adversarial parties. We first describe a generic, five-phase trading protocol that establishes and executes trade between individuals. This protocol accounts full trade specifications on a separate blockchain. We then devise a lightweight system architecture, composed of all required components for a generic asset marketplace. We implement XChange and conduct real-world experimentation. We leverage an existing, lightweight blockchain, TrustChain, to account all orders and full trade specifications. By deploying XChange on multiple low-resource devices, we show that a full trade completes within half a second. To quantify the scalability of our mechanism, we conduct further experiments on our compute cluster. We conclude that the throughput of XChange, in terms of trades per second, scales linearly with the system load. Furthermore, we find that XChange exhibits superior throughput and order fulfil latency compared to related decentralized exchanges, BitShares and Waves.
Yibin Xu, Yangyu Huang, Jianhua Shao, George Theodorakopoulos
Blockchain Sharding is a blockchain performance enhancement approach. By splitting a blockchain into several parallel-run committees (shards), it helps increase transaction throughput, reduce resources required, and increase reward expectation for participants. Recently, several flexible sharding methods that can tolerate up to $n/2$ Byzantine nodes ($n/2$ security level) have been proposed. However, these methods suffer from two main drawbacks. First, in a non-sharding blockchain, nodes can have different weight (power or stake) to create a consensus. So an adversary needs to control half of the overall weight of the system in order for a piece of faulty information to be accepted into the blockchain ($p/2$ security level). In blockchain sharding, all nodes carry the same weight. Thus, it is only under the assumption that the honest participants are creating as many nodes as they can that a $n/2$ security level blockchain sharding reaches the $p/2$ security level. Secondly, when some nodes leave the system, other nodes need to be reassigned, frequently, from shard to shard in order to maintain the security level of the system. In this paper, we present Multichain MWPoW, a $p/2$ security level blockchain sharding architecture that does not require honest participants to create multiple nodes and requires less node reassignment when some nodes leave the system. It combines the Multiple Winners Proof of Work consensus protocol (MWPoW) with the flexibility of $n/2$ blockchain sharding. Our experiments show that Multichain MWPoW outperforms existing blockchain sharding approaches in terms of security, transaction throughput and flexibility.
Tobias Sund, Claes Lööf, Simin Nadjm‐Tehrani, Mikael Asplund
One of the major areas of interest for deployment of blockchains is in the supply chain sector where decentralisation combined with immutability is expected to enhance the transparency and robustness of transaction processing drastically. In this work we contribute to a feasibility study for permissioned blockchains in the context of a major international retail company. First, we characterise the types, relationships, and volumes of events that are created in the life cycle of a product from creation to ownership transfer. We use the created event model and the data from the company operations to identify the load that such an event processing system would have to manage. Then we create a prototype based on Quorum that deals with a significant subset of the events and expose the blockchain-based prototype to variations in load to identify the maximum throughput and average transaction processing time. This system can then form the basis of understanding the bottlenecks, configuration settings and platform choices needed in future potential deployment.
Eder J. Scheid, Daniel Lakic, Bruno Rodrigues, Burkhard Stiller
Due to the growing interest in the blockchain (BC), several applications are being developed, taking advantage of the benefits that such technology promises to deliver, such as removal of Trust Third Parties (TTP) to verify transactions and data immutability. However, these applications require certain aspects, such as high transaction throughput or data privacy, that early BC implementations (e.g., Bitcoin) did not provide. Thus, a myriad of novel BC implementations was developed, which introduced the issue of choosing the right implementation for a specific use-case. This paper presents a framework, called PleBeuS, to address this selection issue by allowing users to specify policies that rule the automatic selection of the BC that data will be stored. The selection process relies on a cost-aware approach and considers both public and private implementations and their technical characteristics. Moreover, PleBeuS communicates with a BC-agnostic interoperability API to enforce transactions. The evaluation of the PleBeuS prototype showed that it is possible to automatically select a BC-based on user policies, considering cost thresholds and technical details (e.g., BC throughput, deployment), and reduce manual interaction.
As the development of the national economy, SMEs(Small and Medium-sized Enterprises) have played an important role in most aspects of economic growth and commercial credit has become one essential factor in enterprises' development. Thus, developing one excellent credit evaluation system which reflects the credit level of SMEs well has become one hotspot in corresponding research field. This paper has explored one distributed credit evaluation system based on blockchain technology which has intelligent protocols and distributed features to provide credit records through unchangeable timestamps and distributed ledger and improve the defects in current centralized systems.
Amir Abbaszadeh Sori, Mehdi Golsorkhtabaramiri, Amir Masoud Rahmani
Over the last decade, cryptocurrencies have made a significant progress as Bitcoin. Nowadays, one of the challenges in the cryptocurrencies community is the high energy consumption of Bitcoin. Not only Bitcoin but also some other cryptocurrencies deal with this problem. This work-in-progress paper defines macro standardization for energy consumption of each transaction based on VISA and MasterCard energy consumption, IOTA energy consumption modeling, and measuring of IOTA current rate control mechanism (Proof-of-Work).
Ahmed Taha, Ahmed Zakaria, Dong‐Seong Kim, Neeraj Suri
Cloud computing offers a model where resources (storage, applications, etc.) are abstracted and provided “as-a- service” in a remotely accessible manner. Although there are numerous claimed benefits of the Cloud to ensure confidentiality, integrity, and availability of the stored data, the number of security breaches is still on the rise. The lack of security assurance and transparency prevented customers/enterprises from trusting the Cloud Service Providers (CSPs). Unless the customer’s security requirements are identified and documented by the CSPs, customers can not be assured that the CSPs will satisfy their requirements. Furthermore, the customer’s compensation upon a violation is a manual time intensive process. In this paper we address the aforementioned challenges by proposing a decentralized customer-based monitoring approach running over Ethereum blockchain. The proposed approach allows the customer(s) to validate the compliance of CSP(s) to the contracted services in the Service Level Agreements (SLAs) and “autonomsly” compensate customers in case of security breaches. At the same time, the proposed approach prevents customers from misreporting for financial gain. The approach builds upon the Ethereum blockchain infrastructure in order to securely store monitoring logs and incorporate SLAs as smart contracts. The compliance validation framework is implemented and its functionality is evaluated on Amazon EC2 and Ethereum Blockchain.
Distributed Ledger Technology (DLT) is an emerging technology to remove middlemen from an eco-system. However, many DLT/BC projects are very technologically oriented and fail to address the business case and the re-design of its eco-system. Therefore, many DLT/BC projects do fail. We propose a minimalistic decision tree to check whether a business case is suitable for implementation by DLT/BC technology and evaluate the tree in the healhtcare domain.
Flavio Corradini, Alessandro Marcelletti, Andrea Morichetta, Andrea Polini · 6 authors
The adoption of model-driven engineering methodologies contributes to reduce the complexity of developing distributed systems. A key point to master such complexity is the use of modelling languages, such as the BPMN standard. This permits to specify choreography diagrams describing, from a global point of view, the interactions that should occur among distributed components in order to reach given goals. Even though BPMN choreographies are promising to increase business possibilities, their concrete adoption has been challenging and faced complex hurdles. On the one hand, there is a lack of concrete support to the different phases of the choreography life-cycle, especially in relation to the choreography execution. Another obstacle consists in the lack of distributed infrastructures allowing the participants involved in the cooperation to trust each other, and in particular to get enough guarantees that all of them will behave as prescribed by the choreography model.
The limitation with smart contracts is that they cannot access external data which might be required to control the execution of business logic. Oracles can be used to provide external data to smart contracts. An oracle is an interface that delivers data from external data outside the blockchain to a smart contract to consume. Oracle can deliver different types of data depending on the industry and requirements. In this paper, we study and describe the widely used blockchain oracles. Then, we elaborate on his potential role, technical architecture, and design patterns. Finally, we discuss the human oracle and his key role in solving the truth problem by reaching a consensus about a certain inquiry and tasks.
Wim Laurier, Walter S. A. Schwaiger, Simon Polovina
Distributed ledger technology is by some believe to be the accounting system of the future, replacing the centuries-old double-entry accounting paradigm, as it has desirable characteristics such as tamper-resistance. However, it might suffer from technology lock-in as double-entry bookkeeping, due to its long-standing history, has offered the conceptual foundations for many laws, regulations and business practices. While some of these laws, regulations and practices might become obsolete as a result of distributed ledger technology, some might still prove to be valuable in a new technological context. While aiming at unlocking the potential of distributed ledger technology in an accounting context, we also want to preserve the wisdom of accounting craftsman. For this reason, it is the aim of this paper to offer a bi-directional mapping between traditional double-entry bookkeeping and innovative paradigms that have proven their value in decentralised systems, of which distributed ledger technology is an exponent. This paper offers such a mapping for the Resource-Event-Agent paradigm.
Consensus protocols are currently the bottlenecks that prevent blockchain systems from scaling. However, we argue that transaction execution is also important to the performance and security of blockchains. In other words, there are ample opportunities to speed up and further secure blockchains by reducing the cost of transaction execution. Our goal is to understand how much we can speed up blockchains by exploiting transaction concurrency available in blockchain workloads. To this end, we first analyze historical data of seven major public blockchains, namely Bitcoin, Bitcoin Cash, Litecoin, Dogecoin, Ethereum, Ethereum Classic, and Zilliqa. We consider two metrics for concurrency, namely the single-transaction conflict rate per block, and the group conflict rate per block. We find that there is more concurrency in UTXO-based blockchains than in account-based ones, although the amount of concurrency in the former is lower than expected. Another interesting finding is that some blockchains with larger blocks have more concurrency than blockchains with smaller blocks. Next, we propose an analytical model for estimating the transaction execution speed-up given an amount of concurrency. Using results from our empirical analysis, the model estimates that 6x speed-ups in Ethereum can be achieved if all available concurrency is exploited.
Elham Akbari, Wenbing Zhao, Shunkun Yang, Xiong Luo
It has been well recognized that traditional blockchains have limited throughput. It is intuitive to achieve higher throughput by increasing the block size and shortening the block interval. In this paper, we study the security implications on doing so, and define the boundary for acceptable block sizes and block intervals. We define the security of the blockchain in terms of the stale block rate in the network and carry out an empirical study using a blockchain simulator to find the optimal block parameters (i.e., size and interval). We show that it is possible to achieve sufficiently high throughput for a blockchain platform to be used for activities beyond cryptocurrency, such as state-level electronic voting.
Onno W. Purbo, Sriyanto Sriyanto, Suhendro Suhendro, RZ Abdul Aziz · 5 authors
In this paper, we report the benchmarking results of Hyperledger, a Distributed Ledger, which is the derivation Blockchain Technology. Method to evaluate Hyperledger in a limited infrastructure is developed. Themeasured infrastructure consists of 8 nodes with a load of up to 20000 transactions/second. Hyperledger consistently runs all evaluation, namely, for 20,000 transactions, the run time 74.30s, latency 73.40ms latency, and 257 tps. The benchmarking of Hyperledger shows better than a database system in a high workload scenario. We found that the maximum size data volume in one transaction on the Hyperledger network is around ten (10) times of MySQL. Also, the time spent on processing a single transaction in the blockchain network is 80-200 times faster than MySQL. This initial analysis can provide an overview for practitioners in making decisions about the adoption of blockchain technology in their IT systems.
Friedrich-Alexander-Universität Erlangen-Nürnberg, Lehrstuhl für Wirtschaftsinformatik, insb. im Dienstleistungsbereich, Nürnberg, Germany, Philipp Klinger, Freimut Bodendorf
Cross-organizational business processes involving multiple participants are choreographed, thus rely on mutual trust of collaborators or need to be coordinated by a central instance.Using Smart Contracts, business processes can be executed without a mutually trusted and centralized orchestrating authority.Former Blockchain-based execution framework proposals focus on orchestration diagrams as a basis for execution.Contrary, this work focuses on BPMN process collaboration diagrams as implementation basis and makes additional transformation steps obsolete.With the herein proposed framework for execution of cross-organizational process collaborations, another approach for the implementation and execution of interorganizational processes on a Blockchain is presented, including a voting mechanism for process deployment as well as a subscription service to facilitate process handovers between participants more efficiently.The framework is exemplified and evaluated with a use case from a large German industrial manufacturing company.
Blockchain and smart contract technologies were recently introduced. Due to their short histories, many issues have emerged but are not solved yet. In this article, we summarize the currently concentrated issues under developing with regards to smart contracts: vulnerability and cost optimization. We introduce other issues never considered but essential for successful commercialization of the smart contract technology. Also, we verify that the optimized code of smart contracts can significantly save transactions costs. Finally, we address that the cost-optimized design is affected by the platform type of blockchain systems. So, the vulnerability and cost analysis of smart contracts must consider the blockchain platform to be deployed.
A blockchain, such as Bitcoin, is an append-only, secure, transparent, distributed ledger. A fair blockchain is expected to have healthy metrics; high honest mining power, low processing latency, i.e., low wait times for transactions and stable price of consumption, i.e., the minimum transaction fee required to have a transaction processed. As Bitcoin matures, the influx of transactions increases and the block rewards become insignificant. We show that under these conditions, it becomes hard to maintain the health of the blockchain. In Bitcoin, under these mature operating conditions (MOC), the miners would find it challenging to cover their mining costs as there would be no more revenue from merely mining a block. It may cause miners not to continue mining, threatening the blockchain's security. Further, as we show in this paper using simulations, the cost of acting in favor of the health of the blockchain, under MOC, is very high in Bitcoin, causing all miners to process transactions greedily. It leads to stranded transactions, i.e., transactions offering low transaction fees, experiencing unreasonably high processing latency. To make matters worse, a compounding effect of these stranded transactions is the rising price of consumption. Such phenomena not only induce unfairness as experienced by the miners and the users but also deteriorate the health of the blockchain. We propose BitcoinF transaction processing protocol, a simple, yet highly effective modification to the existing Bitcoin protocol to fix these issues of unfairness. BitcoinF resolves these issues of unfairness while preserving the ability of the users to express urgency and have their transactions prioritized.
Smart contracts increasingly cause attention for its ability to widen blockchain's application scope. However, the security of contracts is vital to its wide deployment. In this article, we propose a multilevel smart contract modeling solution to analyze the security of contract. We improve the program logic rules for bytecode and apply the Hoare condition to create a Colored Petri Net (CPN) model. The model detection method provided by the CPN tools can show the full-state space and the wrong execution path, which help us analyze the security of the contract from several perspectives. The example shows that the counter-example path given by the contract model is accord with our expected results based on code analysis, proving the correctness of the solution. In addition, we design a highly automated modeling method, introducing custom call libraries and a path derivation algorithm based on backtracking, which improves the efficiency and pertinence of the dynamic simulation of CPN models.
Emanuel Ferreira Coutinho, Diogo Eliseu Paulo, Antonio Welligton Abreu, I. M.Bezerra Carla
Cloud Computing is a technology widely used in academia and industry, providing varied services on demand. Blockchain technology was developed initially for the creation of a crypto-currency and nowadays is being exploited for several other applications, such as health, agriculture, IoT and education. Some work initiatives are already taking place with the integration of these two technologies, either for research or for cloud service provision. This article aims to present a preliminary discussion on some aspects of integration between blockchain and cloud computing. Contributions of this paper include: (i) presentation of two integrated commercial cloud computing and blockchain environments; and (ii) some research opportunities on the use of both environments.
Practical Byzantine Fault Tolerance (PBFT) is a blockchain consensus mechanism that is widely used at present, but the confidence of blockchain node in PBFT cannot be guaranteed, and a large amount of communication resources will be consumed in the process of reaching consensus. The paper proposes a new consensus mechanism, namely the Dynamic Grouping Byzantine Fault Tolerance Mechanism (DGBFT) based on confidence. The principles of DGBFT are as follows: 1) By extending the node's attributes with the confidence, and designing a mechanism to evaluate the node's confidence, therefore, the confidence adjustment and grouping adjustment can be performed on the nodes in the system. By grouping the confidence nodes by the confidence group, the communication complexity is greatly reduced, and the malicious nodes can be effectively excluded. Finally, the experimental results show that the blockchain applying the improved mechanism can significantly improve the communication efficiency of the system and the overall confidence of the system.