Sijie Huang, He Huang, Guoju Gao, Yu-E Sun · 6 authors
Blockchain came to prominence as the distributed ledger underneath Bitcoin, which protects the transaction histories in a fully-connected, peer-to-peer network. The blockchain mining process requires high computing power to solve a Proof-of-Work (PoW) puzzle, which is hard to implement on users’ mobile devices. So these miners may leverage the edge/cloud service providers (ESPs/CSP) to calculate the PoW puzzle. The existing edge-assisted blockchain networks assumed that all ESPs have a uniform propagation delay, which is unrealistic. In this article, we consider a more practical scene where ESPs locate in diverse positions of the blockchain network, which causes different propagation delays when supporting the computation of the PoW puzzle. Additionally, these ESPs connect to a remote CSP for resource scheduling when the computing tasks exceed their maximum capacity. The blockchain mining process generally involves complicated competition and games among CSP, ESPs, and miners. Each service provider focuses on how to determine his resource price so that he can maximize his utility. According to the set resource price, each miner concentrates on scheduling his resource requests for each ESP to maximize individual personal utility, which depends on ESPs’ resource price and propagation delays. We first model such a resource pricing and scheduling problem as a three-stage multi-leader multi-follower Stackelberg game and aim at finding the Stackelberg equilibrium. Then, we analyze the subgame optimization problem in each stage and propose an iterative algorithm based on backward induction to achieve the Nash equilibrium of the Stackelberg game. Finally, extensive simulations are conducted to verify the significant performance of the proposed solution.
With the introduction of smart contacts, Ethereum has become one of the most popular blockchain networks. In the wake of its popularity, an increasing number of Ethereum-based software have been developed. However, the carbon emissions resulting from these software has been pointed out as a global issue. It is necessary to reduce the energy consumed by these software to reduce carbon emissions. Recently, most studies have focused on smart contracts and proposed energy-efficient methods for the development of carbon friendly Ethereum networks. However, in addition to smart contracts, the energy used by client software in Ethereum networks should also be reviewed. This is because the client software performs all functions occurring in the Ethereum network, including smart contracts. Therefore, energy bugs that waste energy in Ethereum client software should be investigated and solved. The first task to enable this is to build an energy bug benchmark of Ethereum client software. This study introduces ECench, an energy bug benchmark of Ethereum client software. ECench includes 507 energy buggy commits from 7 series of client software that are officially operated in the Ethereum network. We carefully collected and manually reviewed them for cleaner commits. A key strength of our benchmark is that it provides eight energy wastage categories, which can serve as a cornerstone for researchers to identify energy waste codes. ECench can provide a valuable starting point for studies on energy reduction and carbon reduction in Ethereum.
How to achieve secure content distribution and accountability in information-centric networking (ICN) is a crucial problem. Subscribers need to verify whether the data came from a reliable source, rather than from a spoofing adversary. Public key cryptography was introduced to achieve a method of authentication that binds the data packet to its owner. In existing prototypes, PKIs, identity-based signatures (IBSs) and recommendation networks are the common schemes used to ensure the authenticity and availability of public keys. However, CA-based PKIs and KGC-based IBSs have been proven to be weak when it comes to resisting security attacks, with recommendation networks being too complex to deploy. In this respect, we designed a novel distributed authentication model as a secure scheme to support public key cryptography. Our model establishes a decentralized public key infrastructure by combining the smart contracts of blockchain and optimized zero-knowledge proof-verifiable presentations by utilizing the DID project, which realizes the management of public key certificates through blockchain and ensures the authenticity and availability of public keys in decentralized infrastructure. Our scheme fundamentally solves the issues of security and feasibility in existing schemes and provides a more scalable solution with respect to authenticating data sources. An experiment demonstrated that our proposal is 20% faster than the original zero knowledge proof scheme in registration.
Open access
Caching and Content Delivery
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
Self-sovereign identity (SSI) has gained a large amount of interest. It enables physical entities to retain ownership and control of their digital identities, which naturally forms a conceptual decentralized architecture. With the support of the distributed ledger technology (DLT), it is possible to implement this conceptual decentralized architecture in practice and further bring technical advantages such as privacy protection, security enhancement, high availability. However, developing such a relatively new identity model has high costs and risks with uncertainty. To facilitate the use of the DLT-based SSI in practice, we formulate Self-Sovereign Identity as a Service (SSIaaS), a concept that enables a system, especially a system cluster, to readily adopt SSI as its identity model for identification, authentication, and authorization. We propose a practical architecture by elaborating the service concept, SSI, and DLT to implement SSIaaS platforms and SSI services. Besides, we present an architecture for constructing and customizing SSI services with a set of architectural patterns and provide corresponding evaluations. Furthermore, we demonstrate the feasibility of our proposed architecture in practice with Selfid, an SSIaaS platform based on our proposed architecture.
Off-chain storage is utilized to reduce on-chain storage costs, and further enhance the scalability of blockchain technology. For such mechanisms, transaction data of large size is stored in external centralized databases or distributed peer-to-peer storage, instead of blockchain nodes themselves. However, in emerging blockchain application areas, such as healthcare and the Internet of Things (IoT), off-chain data should be located close to the users with the right privileges, yet it is currently challenging to locate data close to such users and limit data transfers accordingly. To meet these challenges, we design a user-centric in-network caching mechanism for off-chain storage (UCINC) with information-centric networking (ICN) approach to regulate the data caching to the off-chain storage in the network where users are located. With UCINC, data is cached at off-chain storage based on location attributes, retrieved through the interest/data ICN paradigm, and users’ access privileges are determined based on their attributes including locations. We furthermore conduct simulation experiments to confirm that the proposed UCINC achieves higher download performance and traffic efficiency, compared with the existing off-chain storage mechanisms.
In recent years, decentralized global ID systems have attracted significant attention. The concept of self-sovereign identity was established to realize a decentralized global ID, which is achieved by verifiable credentials and decentralized identifiers. However, there is a problem in using such decentralized global IDs for various remote services from the viewpoint of flexibility. In this paper, we propose a system which can give an "attribute" to global IDs dynamically by using only the basic function of a blockchain (i.e., using cryptocurrency transfer only). The main idea of our scheme is that an "attribute token" is assigned to global IDs or removed from global IDs using the token transmission function in a blockchain. Thus, we can set the credibility level and decentralization level of global IDs adaptively, and thus, we manage global IDs securely and flexibly. Furthermore, we conduct feasibility experiments with the proposed system and realize an attribute token assignment in Bitcoin and Ethereum cryptocurrencies. This result shows that our system can use almost all blockchain systems having a token transmission function.
Payment channel (PC) greatly improves blockchain scalability by allowing an unlimited number of off-chain transactions instead of committing every transaction to the blockchain. However, one PC just confines to two nodes. Thus, for a node, like Cafe, who frequently receives money from multiple nodes, massive PCs need to be created, which leads to massively and repeatedly information addition of channels to the blockchain and costs much fees. In this paper, we introduce a multi-node payment channel (MPC) method to solve the problem above. MPC suits the scenario that one node frequently receives money from multiple nodes, such as Cafe, shop, etc. Compared to PC, MPC can contain nearly unlimited number of nodes, thus avoiding repetitive channel information addition to the blockchain and meanwhile reducing the fee. MPC supports the same transaction logic of PC and cooperates well with existing PC. The security, economy and efficiency of MPC are proved. We implement MPC’s smart contract in Ethereum and experimental results show that MPC outperforms the existing PC.
In this work, we propose – "CartelChain" – for the secure communication of blockchains (BCs) and achieving opti-mal throughput. With the advancement of BC technology, many industries are adopting it to maintain a secure, immutable, and decentralized system. Industries such as IoT, supply chain, and finance apply BC technology to maintain a decentralized database and automate different activities using smart contracts. However, storing data of different scenarios from the Industrial Internet of Things (IIoT) in separate BCs (multi-chains) leads to isolated data islands. This results in difficulty for these multi-chains to interact with one another efficiently and credibly. For the seamless operation of industries, it is of significant importance to achieve interoperability among different BCs. Toward achieving this, we propose a solution that utilizes smart contracts for enabling data exchange among various BCs. Further, for secure and reliable communication, we use encryption and an access control mechanism that makes the same more credible and reduces the latency compared with multi-chains sharing the data sequentially. Through experimental results, we demonstrate that the proposed method can utilize the resources more efficiently and reduce CPU as well energy usage by 8% and 6%, respectively. Apart from this, the throughput of the proposed method is 900 tps at 200 requests.
Kun Zhou, Chunping Wang, Xiaoqing Wang, Hongbing Cheng
Till the end of September 2021, the size of Bitcoin blockchain has reached 366.9GB and continues to increase at an average annual growth rate of 17.6%. The high requirement for storage space prevents new nodes from joining the network, which seriously hinders the development of blockchain technology. In this paper, in order to explore the data characteristics of Bitcoin’s block, we performed statistical experiment on the current 680,000 blocks. The analysis results showed that in nearly 95% of blocks, the number of spent transaction output(STXO) accounts for more than 67% of the total transaction output. Inspired by this, we proposed a hybrid storage scheme to reduce the size of blocks by deleting the transaction data with the STXO ratio over 67% firstly and compressing some fixed-length fields in those transactions. And then, the newly generated block files were deposited to the InterPlanetary File System(IPFS) private network to improve the scalability of Bitcoin network. The experiment results and analysis showed that our scheme achieved a compression ratio of 96.9% and could effectively help the Bitcoin full nodes save 330GB of storage space with guaranteeing the normal operation of Bitcoin network.
Lam Duc Nguyen, Arne Bröring, Massimo Pizzol, Petar Popovski
In recent years, industrial manufacturing has undergone massive technological changes that embrace digitalization and automation towards the vision of intelligent manufacturing plants. With the aim of maximizing efficiency and profitability in production, an important goal is to enable flexible manufacturing, both, for the customer (desiring more individualized products) and for the manufacturer (to adjust to market demands). Manufacturing-as-a-service can support this through manufacturing plants that are used by different tenants who utilize the machines in the plant, which are offered by different providers. To enable such pay-per-use business models, Distributed Ledger Technology (DLT) is a viable option to establish decentralized trust and traceability. Thus, in this paper, we study potential DLT technologies for efficient and intelligent integration of DLT-based solutions in manufacturing environments. We propose a general framework to adapt DLT in manufacturing, and then we introduce the use case of shared manufacturing, which we utilize to study the communication and computation efficiency of selected DLTs in resource-constrained wireless IoT networks.
Weizhao Tang, Lucianna Kiffer, Giulia Fanti, Ari Juels
Most permissionless blockchain networks run on peer-to-peer (P2P) networks, which offer flexibility and decentralization at the expense of performance (e.g., network latency). Historically, this tradeoff has not been a bottleneck for most blockchains. However, an emerging host of blockchain-based applications (e.g., decentralized finance) are increasingly sensitive to latency; users who can reduce their network latency relative to other users can accrue (sometimes significant) financial gains. In this work, we initiate the study of strategic latency reduction in blockchain P2P networks. We first define two classes of latency that are of interest in blockchain applications. We then show empirically that a strategic agent who controls only their local peering decisions can manipulate both types of latency, achieving 60\% of the global latency gains provided by the centralized, paid service bloXroute, or, in targeted scenarios, comparable gains. Finally, we show that our results are not due to the poor design of existing P2P networks. Under a simple network model, we theoretically prove that an adversary can always manipulate the P2P network's latency to their advantage, provided the network experiences sufficient peer churn and transaction activity.
Blockchain networks are already extensively used in various applications because of their increased security. The unique characteristics of blockchain technology, such as decentralized, peer-to-peer, and invariable distributed ledger qualities, make it appealing to researchers, academics, and industry. The consensus protocol is a fundamental part of blockchain technology. PoW (Proof of Work) or fixed-validator consensus protocols comprise most of the existing consensus mechanisms. However, the tremendous computational effort required for PoW leads to excessive energy and computing resource usage. On the other hand, Fixed-validator protocols validate new blocks by a fixed, static set of validators, allowing attackers to execute multiple attacks against these validators. In this article, we proposed a novel consensus protocol base on the Proof of Activity protocol and game theory. Our consensus protocol is efficient in energy consumption and can deal with selfish mining and majority-attack.
Many systems have recently begun to examine blockchain qualities in order to create cooperation enforcement methods. This paper provides a complete and extensive evaluation of work on multi-hop MANETs with blockchain-based trust control between nodes. We contextualize the snag of security in MANETs resulting from the lack of trust between the participating nodes. We present the blockchain concepts and discuss the limitation of the current blockchain in MANETs. We review the promising proposed ideas in the state-of-the-art based on research papers. Finally, we discuss and summarize strategies and challenges for further research.
Web archives store born-digital documents, which are usually collected from the Internet by crawlers and stored in the Web Archive (WARC) format. The trustworthiness and integrity of web archives is still an open challenge, especially in the news portal domain, which face additional challenges of censorship even in democratic societies. The aim of this paper is to present a light-weight, blockchain-based solution for web archive validation, which would ensure that documents retrieved by crawlers are authentic for many years to come. We developed our archive validation solution as an extension and continuation of our work in web crawler development mainly targeting news portals. The system is designed as an overlay over a blockchain with a proof-of-stake (PoS) distributed consensus algorithm. PoS was chosen due to its lower ecological footprint compared to proof-of-work solutions (e.g. Bitcoin) and lower expected investment in computing infrastructure. We based our prototype on the open-source Nxt blockchain and implemented it in Python. The prototype was tested on web archive content crawled from Hungarian news portals at two different timestamps with more than 1 million articles in total. We concluded that the proposed solution is accessible, usable by different stakeholders to validate crawled content, deployable on cheap commodity hardware, tackles the archive integrity challenge and is capable to efficiently manage duplicate documents.
<p> Power systems are undergoing rapid transitions to incorporate renewable sources of generation and to combat climate change. Next stage of transitions will lead to a shift from large-scale, centralized systems to networks of smallsized, distributed electricity systems which require distributed or decentralized ledgers for database management for efficient transactions. Distributed Ledger Technology (DLT) are a form of decentralized ledgers where the transactions (energy, information and money) among various entities are maintained. One such DLT is blockchain technology which offers several advantages. Data recorded in blockchains are difficult to tamper with; have privacy protection; facilitate fast, accurate and real-time settlement of financial transactions. Contemporary research has started focusing on their possible applications in energy systems. State-of-the-art suggests that while business and market aspects have been extensively discussed, the electrical constraints and implementation methodologies have not been adequately addressed. Furthermore, all the reviewed projects have implemented only peer-to-peer transactions that are not scalable. To incorporate the new entities like prosumers, intermicrogrid transactions and interactions with the legacy power grid, new structural and operational frameworks are necessary. The proposed research explores the possibility of developing blockchain enabled smart microgrids (BSMG) with the above frameworks. It aims to build a conceptual framework of BSMG, including the transaction protocols and process flows. It proposes inclusion of network constraints in a three-levelled transaction setup which is executed over a four-layered architecture. Another practical challenge is that BSMGs may be set up on different blockchain platforms. Hence, this paper also proposes implementing Inter-Blockchain Protocol for the first time to include interoperability and communication between different platforms. Finally the performance metrics that will be used to validate the BSMGs are outlined. </p>
Blockchain has attracted considerable attention as a solution to the challenges of privacy, security and decentralisation for many applications. However, these characteristics of the blockchain result in ever growing ledger size, which is one of the major barriers to blockchain adoption in large-scale networks such as the Internet of Things (IoT). In this paper, we propose Multi-Level Distributed Caching (MLDC) for blockchain storage optimisation which reduces data replication based on data access pattern. MLDC divides nodes into storage classes (SCs) by their node availability, and assigns each SC a different Access Frequency (AF) to remove data from the local storage. Over time, each node only stores frequently accessed data, so MLDC can reduce the total storage cost by 83% compared to conventional blockchain systems, while maintaining blockchain consistency and data availability with a slight increase in network overhead and data query delay.
Befekadu G. Gebraselase, Bjarne E. Helvik, Yuming Jiang
Bitcoin is the first and the most extensive decentralized electronic cryptocurrency system that uses blockchain technology. It uses a peer-to-peer (P2P) network to operate without a central authority and propagate system information such as transactions or blockchain updates. The communication between participating nodes is highly relying on the underlying network infrastructure to facilitate a platform. Understanding the impact of peer formation strategies, peer list, and delay is vital in understanding node to node communication and the system performance. Therefore, we performed an extensive study on the transaction characteristics of Bitcoin through a testbed. The analysis shows that peer selection strategies affect the transaction propagation and confirmation times. In particular, better performance, in terms of smaller transaction confirmation time and lower number of temporary forks, may be achieved by adjusting the default nearby-based peer selection strategy.
Matthias Grundmann, Max Baumstark, Hannes Hartenstein
A recent spam wave of IP addresses in the Bitcoin P2P network allowed us to estimate the degree distribution of reachable peers. The resulting distribution indicates that about half of the reachable peers run with Bitcoin Core’s default setting of a maximum of 125 concurrent connections and nearly all connection slots are taken. We validate this result empirically. We use our observations of the spam wave to group IP addresses that belong to the same peer. By doing this grouping, we improve on previous measurements of the number of reachable peers and show that simply counting IP addresses overestimates the number of reachable peers by 15 %. We revalidate previous work by using our observations to estimate the number of unreachable peers.
The bitcoin payment innovation has gained wider interest around the world, but its adoption among the general population has been a challenge. Bitcoin as a peer-to-peer technology works with no central authority or banks, and the transaction management and issuing of bitcoin is carried out collectively by the network. One major debate on bitcoin development and diffusion is the critical matter of nongovernment intervention through adequate policy and regulatory framework and thus hinders people’s active participation (acceptance) in the bitcoin market. Consequently, this study is purposed to examine the role government policy and regulations (moderating impact) can have in driving the acceptance of bitcoin payment from the Chinese perspective. The UTAUT was used as the theoretical basis from which a model was developed for testing. The structural equation model (SEM) through the use of SmartPLS was employed to undertake the analysis. The results have demonstrated that government regulation moderates (significant) the influence of both performance expectancy and infrastructure support on the behavioral acceptance of bitcoin payment. However, government regulation contrary to expectations was not significant in moderating the influence of effort expectancy (EE) and security on the acceptance of bitcoin payments. Additionally, the study discovered that performance expectancy, security, EE, and infrastructure support were significant in encouraging bitcoin behavioral adoption. The practical and theoretical implications of these findings on the development and diffusion of bitcoin technology systems are dissected meticulously.
State-of-the-art blockchain sharding solutions, say Monoxide, can induce imbalanced transaction (TX) distributions among all blockchain shards due to their account deployment mechanisms. Imbalanced TX distributions then cause hot shards, in which the cross-shard TXs may experience an unlimited length of confirmation latency. Thus, how to address the hot-shard issue and how to reduce cross-shard TXs become significant challenges of blockchain state sharding. Through reviewing the related studies, we find that a cross-shard TX protocol that can achieve workload balance among all shards and simultaneously reduce the number of cross-shard TXs is still absent from the literature. To this end, we propose BrokerChain, which is a cross-shard blockchain protocol devised for the account/balance-based state sharding. Essentially, BrokerChain exploits fine-grained state partition and account segmentation. We also elaborate on how BrokerChain handles cross-shard TXs through broker accounts. The security issues and other properties of BrokerChain are analyzed substantially. Finally, we conduct comprehensive evaluations using both a cloud-based prototype and a transaction-driven simulator. The evaluation results show that BrokerChain outperforms other solutions in terms of system throughput, transaction confirmation latency, the queue size of transaction pool, and workload balance.
A Blockchain is a promising infrastructure but it has serious scalability problems, i.e., long block synchronization time and high storage cost. Conventional coarse-grained data deduplication schemes (block or file level) are proved to be ineffective on this problem. Based on comprehensive analysis on typical blockchain workloads, we are the first to propose two new locality concepts: economic and argument locality. To further explore these new localities, we propose a novel fine-grained data deduplication scheme (transaction level) named Alias-Chain to improve the scalability of blockchains. Specifically, Alias-Chain replaces frequently used data, e.g., smart contract arguments, with much shorter aliases to reduce the block size. During prop-agation and preservation of blocks, smaller blocks result in both shorter synchronization time and lower storage cost. Simulation results show the average transfer and SC-call transaction sizes can be reduced by up to 11.23% and 43.23% in native Ethereum, and up to 61.95 % and 77.54 % in Ethereum optimized by state-of-the-art techniques, respectively. Prototyping-based experiments are further conducted on a testbed consisting of up to 3200 miners. The results demonstrate the effectiveness and efficiency of Alias-Chain on reducing block synchronization time and storage cost under typical real-world workloads.
Suhail Al Marzouqi, Michael Baddeley, Martin Andreoni Lopez
Blockchain has challenged many of the conventions around digital security. In essence, blockchain supports a decentralized platform maintained by peers instead of a single entity. Furthermore, the data in the blockchain is immutable and is being held in a secure and encrypted way. However, running the blockchain on resource-limited devices, such as a consumer PC or a low-power Raspberry Pi as opposed to dedicated servers, is demanding due to the resource limitation in energy, memory, and time taken to validate the transaction on the blockchain. This paper explores these limitations by evaluating and benchmarking the blockchain framework Geth: a terminal interface for the Ethereum blockchain which makes it possible to create a private blockchain in addition to joining the actual blockchain. This article employs a private blockchain within Geth and benchmarks the blockchain to highlight the differences (and limitations) between the devices. Specifically, we make the following observations: (i) the time it takes to validate and add the transaction to the blockchain on a Raspberry Pi 4 is markedly slower compared to an Intel i9-10885H CPU @ 2.40GHz, (ii) the transaction between PCs compared to transactions between Pis is around two orders of magnitude higher. These valuable insights can be used to help researchers in the design and implementation of blockchain-driven security architectures for distributed systems, such as industrial IoT deployments and UAV swarms.