Roman Matzutt, Benedikt Kalde, Jan Pennekamp, Arthur Drichel · 6 authors
Popular cryptocurrencies continue to face serious scalability issues due to their ever-growing blockchains. Thus, modern blockchain designs began to prune old blocks and rely on recent snapshots for their bootstrapping processes instead. Unfortunately, established systems are often considered incapable of adopting these improvements. In this work, we present CoinPrune, our block-pruning scheme with full Bitcoin compatibility, to revise this popular belief. CoinPrune bootstraps joining nodes via snapshots that are periodically created from Bitcoin's set of unspent transaction outputs (UTXO set). Our scheme establishes trust in these snapshots by relying on CoinPrune-supporting miners to mutually reaffirm a snapshot's correctness on the blockchain. This way, snapshots remain trustworthy even if adversaries attempt to tamper with them. Our scheme maintains its retrospective deployability by relying on positive feedback only, i.e., blocks containing invalid reaffirmations are not rejected, but invalid reaffirmations are outpaced by the benign ones created by an honest majority among CoinPrune-supporting miners. Already today, CoinPrune reduces the storage requirements for Bitcoin nodes by two orders of magnitude, as joining nodes need to fetch and process only 6 GiB instead of 271 GiB of data in our evaluation, reducing the synchronization time of powerful devices from currently 7 h to 51 min, with even larger potential drops for less powerful devices. CoinPrune is further aware of higher-level application data, i.e., it conserves otherwise pruned application data and allows nodes to obfuscate objectionable and potentially illegal blockchain content from their UTXO set and the snapshots they distribute.
lockchain stores a series of transactions in form of a sequence of linked blocks. Hence, the concept of ledger is easily maintained. Transactions and interactions that take place among participants accessing the distributed and decentralized blockchain network are holding through ledger. In a student management system (SMS), vital information can be highly shared and well protected at the same time. This paper proposes a model for using blockchains to implement fully functional SMS that maintains students’ records, course registrations record and student marks. The proposed model adds more security via the use of hashing and data readily available with decentralized data storage. In addition, the use of ledger-based system to maintain SMS data introduces reliable and highly trusted model.
Alexandr Kuznetsov, Inna Oleshko, Vladyslav Tymchenko, Konstantin Lisitsky · 6 authors
A blockchain, or in other words a chain of transaction blocks, is a distributed database that maintains an ordered chain of blocks that reliably connect the information contained in them. Copies of chain blocks are usually stored on multiple computers and synchronized in accordance with the rules of building a chain of blocks, which provides secure and change-resistant storage of information. To build linked lists of blocks hashing is used. Hashing is a special cryptographic primitive that provides one-way, resistance to collisions and search for prototypes computation of hash value (hash or message digest). In this paper a comparative analysis of the performance of hashing algorithms that can be used in modern decentralized blockchain networks are conducted. Specifically, the hash performance on different desktop systems, the number of cycles per byte (Cycles/byte), the amount of hashed message per second (MB/s) and the hash rate (KHash/s) are investigated. The comparative analysis of different hashing algorithms allows us to choose the most suitable candidates for building decentralized systems type of blockchain.
As an append-only distributed database, blockchain is utilized in a vast variety of applications including the cryptocurrency and Internet-of-Things (IoT). The existing blockchain solutions show downsides in communication and storage scalability, as well as decentralization. In this article, we propose LightChain , which is the first blockchain architecture that operates over a Distributed Hash Table (DHT) of participating peers. LightChain is a permissionless blockchain that provides addressable blocks and transactions within the network, which makes them efficiently accessible by all peers. Each block and transaction is replicated within the DHT of peers and is retrieved in an on-demand manner. Hence, peers in LightChain are not required to retrieve or keep the entire ledger. LightChain is fair as all of the participating peers have a uniform chance of being involved in the consensus regardless of their influence such as hashing power or stake. We provide formal mathematical analysis and experimental results (simulations and cloud deployment) to demonstrate the security, efficiency, and fairness of LightChain , and show that LightChain is the only existing blockchain that can provide integrity under the corrupted majority power of peers. As we experimentally demonstrate, compared to the mainstream blockchains such as Bitcoin and Ethereum, LightChain requires around 66 times smaller per node storage, and is around 380 times faster on bootstrapping a new node to the system, and each LightChain node is rewarded equally likely for participating in the protocol.
With the rise in fog computing, users are no longer restricted to only accessing resources located in central and distant clouds and can request services from neighboring fog nodes distributed over networks. This can effectively reduce the network latency of service responses and the load of data centers. Furthermore, it can prevent the Internet’s bandwidth from being used up due to massive data flows from end users to clouds. However, fog-computing resources are distributed over multiple levels of networks and are managed by different owners. Consequently, the problem of service discovery becomes quite complicated. For resolving this problem, a decentralized service discovery method is required. Accordingly, this research proposes a service discovery framework based on the distributed ledger technology of IOTA. The proposed framework enables clients to directly search for service nodes through any node in the IOTA Mainnet to achieve the goals of public access and high availability and avoid network attacks to distributed hash tables that are popularly used for service discovery. Moreover, clients can obtain more comprehensive information by visiting known nodes and select a fog node able to provide services with the shortest latency. Our experimental results have shown that the proposed framework is cost-effective for distributed service discovery due to the advantages of IOTA. On the other hand, it can indeed enable clients to obtain higher service quality by automatic node selection.
Ge Chen, Jun Wu, Wu Yang, Ali Kashif Bashir · 6 authors
Nowadays, adopting blockchain technology to Internet of Things has become a trend and it is important to minimize energy consumption while providing a high quality of service (QoS) in Blockchain-based IoT networks. Pre-caching popular and fresh IoT content avoids activating sensors frequently, thus effectively reducing network energy consumption. However, the user equipment in regions covered by base stations will generate distributed and time-varying data requests, hence modeling the base station topology to capturing spatio-temporal request patterns is required for the data storage pre-allocation. Traditional solutions typically fail to pay attention to the topology, resulting in the sensor being activated redundantly. In this paper, we propose Request Graph Convolutional-LSTM to capture the spatio-temporal request patterns in Blockchain-based IoT networks and make predictions. Moreover, a heuristic algorithm based on the predictions is proposed to develop pre-caching strategy, which determines the data and location to be cached to minimize the mean data retrieval latency restricted by the cache space of IoT network entities and the freshness of IoT content. Experiments show that our proposed frame provides a low energy consumption.
Blockchain technology, with its distributed ledger, decentralization, high security, no tampering and other features, helps to solve the problems of data source confirmation, traceability and authorized data sharing. The effective utilization of data to achieve automatic governance and trusted decision-making of the city is known as "City Brain". The city brain is the key in smart city development, while the key to build a city brain is data resources. Aiming at the challenges existing in the construction of big data platform, this paper proposes a new solution based on blockchain, establishes the entity model and data model, analyzes the business model, designs the blockchain data platform framework and the cloud-blockchain integrated operation mode, and at last discusses the issues concerned in the application.
A decade on since Satoshi’s Bitcoin paper, Blockchain is now considered to be sliding into the trough of Gartner’s hype cycle. Claims in regards to Blockchain and Cryptocurrencies being dead are on the rise, whilst at the same time many claim the contrary. The vague statement encapsulates many different aspects and perspectives of a myriad of use cases, technology and platforms including both the technique as a whole as well as individual instantiations. In this paper, we unpack the statement, break it down, and investigate objectively concrete factors which provide indication in regards to whether Blockchain is dead. We examine metrics including budgets and investment; public company registries and data; community engagement, projects, and source code repositories; academic research and programmes; social media posts; and public interest. We demonstrate metrics individually that indicate the respective measures’ healthy activity and come to the conclusion that the collective statement “Blockchain is dead” does not hold. A clear message extracted from the work proposed herein is that success is achieved where the community comes together rather than works in isolation.
Blockchain and distributed ledger technologies have received significant interest in various areas beyond the financial sector, with profound applications in the Internet of Things (IoT), providing the means for creating truly trustless and secure solutions for IoT applications. Taking into account the weak security defences that the majority of IoT devices have, it is critical that a blockchain-based solution targeting the IoT is not only capable of addressing the many challenges IoT is facing, but also does not introduce other defects, in terms of performance, making its adoption hard to achieve. This paper aims at addressing the above needs by providing a comprehensive and coherent review of the available blockchain solutions to determine their ability to meet the requirements and tackle the challenges of the IoT, using the smart home as the reference domain. Key architectural aspects of blockchain solutions are examined in terms of their ability to withstand various types of common IoT and blockchain attacks, deliver enhanced privacy features, and assure adequate performance levels while processing large amounts of transactions being generated in an IoT environment. The analysis carried out identified that the defences currently provided by blockchain platforms are not sufficient to thwart all the prominent attacks against blockchains, with blockchain 1.0 and 2.0 platforms being susceptible to the majority of them. On the other side, privacy related mechanisms are being supported, to varying degrees, by all platforms investigated; however, each of the them tackles specific only privacy aspects, thus rendering the overall privacy evaluation a challenging task which needs to be considered in an ad-hoc basis. If the underlying consensus protocols performance and fault tolerance is also considered, then only a small number of platforms meet the requirements of our reference IoT domain.
Distributed Ledger Technologies (DLTs) have become an important driving force towards the creation of novel distributed applications aimed at solving problems that range from digital currency tools to self governing digital democracy systems. Our thesis is that Satoshi cryptocurrencies, i.e., Bitcoin and its variants, can be used to endow several popular distributed services with strong privacy, anonymity and censorship resistance properties that evade current solutions. To this end, we first study the design of Satoshi cryptocurrency mining protocols, and discover and document privacy and integrity vulnerabilities of Stratum, the de-facto pooled mining protocol. We have developed tools that exploit these vulnerabilities and have measured their impact and effectiveness under a rigorous academic context. Further, we have designed and implemented Bedrock, a solution that addresses these vulnerabilities. We have evaluated Bedrock in the live Bitcoin ecosystem and show that it achieved orders of magnitude better performance than traditional solutions like TLS and blanket encryption. We further introduce DLSS, a censorship-resistant, distributed ledger storage system that embeds client content into Satoshi transactions and organize it for fast search, recovery and reconstruction among hundreds of millions of financial transactions. DLSS distinguishes and exploits the singularities of different types of communications under censorship conditions. We design, implement and evaluate novel smart contracts tailored to the needs of censored users. For instance, we introduce difficult to censor and undetectable techniques to embed small quantities of data on Satoshi transactions, to be used for communications flowing out of the censored area that need to avoid detection by all-powerful censors. We also introduce techniques that prioritize cost optimization for storing large content flowing into the censored area, where uncensorability is the only priority. Further, we leverage our blockchain-writing constructs to introduce a novel perspective for traditionally hard problems of censorship resistance, private e-mail and secure port-knocking with surreptitious authentication and logging. We prove the security, privacy and anonymity of our smart contracts, and argue they impose unpalatable collateral damage to would-be censors. We build a monitoring and instrumentation framework for evaluating our constructs in the Litecoin cryptocurrency. We evaluate our blockchain-writing constructs by persisting hundreds of MBs of BBC news articles and censored software in the live Litecoin blockchain, where they are available to access for free anywhere in the world. We show that our solutions achieve storage throughput, blockchain utilization, and cost efficiency that improve by 2-4 orders of magnitude on state-of-the-art blockchain-writing solutions.
Lehlogonolo P. I. Ledwaba, Gerhard P. Hancke, Sherrin J. Isaac, Hein S. Venter
The increasing strain on ageing generation infrastructure has seen more frequent instances of scheduled and unscheduled blackouts, rising reliability on fossil fuel based energy alternatives and a slow down in efforts towards achieving universal access to electrical energy in South Africa. To try and relieve the burden on the National Grid and still progress electrification activities, the smart microgrid model and secure energy trade paradigm is considered—enabled by the Industrial IoT (IIoT) and distributed ledger technologies (DLTs). Given the high availability requirements of microgrid operations, the limited resources available on IIoT devices and the high processing and energy requirements of DLT operations, this work aims to determine the effect of native DLT algorithms when implemented on IIoT edge devices to assess the suitability of DLTs as a mechanism to establish a secure, energy trading market for the Internet of Energy. Metrics such as the node transaction time, operating temperature, power consumption, processor and memory usage are considered towards determining possible interference on the edge node operation. In addition, the cost and time required for mining operations associated with the DLT-enabled node are determined in an effort to predict the cost to end users—in terms of fees payable and mobile data costs—as well as predicting the microgrid’s growth and potential blockchain network slowdown.
Distributed peer-to-peer power energy markets are emerging quickly. Due to central governance and lack of effective information aggregation mechanisms, energy trading cannot be efficiently scheduled and tracked. We devise a new distributed energy transaction system over the energy Industrial Internet of Things based on predictive analytics, blockchain, and smart contract technologies. We propose a solution for scheduling distributed energy sources based on the Minimum Cut Maximum Flow theory. Blockchain is used to record transactions and reach consensus. Payment clearing for the actual power consumption is executed via smart contracts. Experimental results on real data show that our solution is practical and achieves a lower total cost for power energy consumption.
Since the introduction of the first Bitcoin blockchain in 2008, different\ndecentralized blockchain systems such as Ethereum, Hyperledger Fabric, and\nCorda, have emerged with public and private accessibility. It has been widely\nacknowledged that no single blockchain network will fit all use cases. As a\nresult, we have observed the increasing popularity of multi-blockchain\necosystem in which customers will move toward different blockchains based on\ntheir particular requirements. Hence, the efficiency and security requirements\nof interactions among these heterogeneous blockchains become critical. In\nrealization of this multi-blockchain paradigm, initiatives in building\nInteroperability-Facilitating Platforms (IFPs) that aim at bridging different\nblockchains (a.k.a. blockchain interoperability) have come to the fore. Despite\ncurrent efforts, it is extremely difficult for blockchain customers\n(organizations, governments, companies) to understand the trade-offs between\ndifferent IFPs and their suitability for different application domains before\nadoption. A key reason is due to a lack of fundamental and systematic\napproaches to assess the variables among different IFPs. To fill this gap,\ndeveloping new IFP requirements specification and open-source benchmark tools\nto advance research in distributed, multi-blockchain interoperability, with\nemphasis on IFP performance and security challenges are required. In this\ndocument, we outline a research proposal study to the community to realize this\ngap.\n
Pierre Schutz, Stanislas Gal, Dimitris Chatzopoulos, Pan Hui
Abstract Peer‐to‐peer (P2P) networks utilize centralized entities (trackers) to assist peers in finding and exchanging information. Although modern P2P protocols are now trackerless and their function relies on distributed hash tables (DHTs), centralized entities are still needed to build file indices (indexing) and assist users in joining DHT swarms (bootstrapping). Although the functionality of these centralized entities are limited, every peer in the network is expected to trust them to function as expected (e.g. to correctly index new files). In this work, a new approach for designing and building decentralized online applications is proposed by introducing DIBDApp. The approach combines blockchain, smart contracts and BitTorrent for building up a combined technology that permits to create decentralized applications that do not require any assistance from centralized entities. DIBDApp is a software library composed of Ethereum smart contracts and an API to the BitTorrent protocol that fully decentralizes indexing, bootstrapping and file storing. DIBDApp enables any peer to seamlessly connect to the designed smart contracts via the Web3J protocol. Extensive experimentation on the Rinkeby Ethereum testnet shows that applications built using the DIBDApp library can perform the same operations as in traditional back‐end architectures with a gas cost of a few USD cents.
Presently, blockchain technology has been widely applied in various application domains such as the Internet of Things (IoT), supply chain management, healthcare, etc. So far, there has been much confusion about whether blockchain performs with scale, and admittedly, a lack of information about best practices that can improve the performance and scale. This paper proposes a novel blockchain network construction methodology to improve the performance of Hyperledger Fabric. As a highly scalable permissioned blockchain platform, Hyperledger Fabric supports a wide range of enterprise use cases from finance to governance. A comprehensive evaluation is performed by observing various configurable network components that can affect the blockchain performance. To demonstrate the significance of the proposed methodology, we set up the experiment environment for the baseline and the test network using optimized parameters, respectively. The experimental results indicate that the test network's performance is enhanced effectively compared to the baseline in transaction throughput and transaction latency.
Abstract Practical Byzantine Fault-tolerant Algorithm (PBFT) is the most widely used consensus algorithm in alliance chain, which has the advantages of fault tolerance and large throughput. However, PBFT also has some problems that can’t be ignored in specific blockchain applications, such as bad behavior of master node, high network communication overhead and low system flexibility. In this paper, the improvement measures of PBFT consensus algorithm are summarized from many aspects, and then compared with traditional PBFT algorithm. Finally, the development direction and trend of PBFT algorithm are prospected, hoping to provide reference for the research and innovation of PBFT consensus algorithm in the future.
Abstract Renewable-energy resources require overwhelming adoption by the common masses for safeguarding the environment from pollution. In this context, the prosumer is an important emerging concept. A prosumer in simple terms is the one who consumes as well as produces electricity and sells it either to the grid or to a neighbour. In the present scenario, peer-to-peer (P2P) energy trading is gaining momentum as a new vista of research that is viewed as a possible way for prosumers to sell energy to neighbours. Enabling P2P energy trading is the only method of making renewable-energy sources popular among the common masses. For making P2P energy trading successful, blockchain technology is sparking considerable interest among researchers. Combined with smart contracts, a blockchain provides secure tamper-proof records of transactions that are recorded in distributed ledgers that are immutable. This paper explores, using a thorough review of recently published research work, how the existing power sector is reshaping in the direction of P2P energy trading with the application of blockchain technology. Various challenges that are being faced by researchers in the implementation of blockchain technology in the energy sector are discussed. Further, this paper presents different start-ups that have emerged in the energy-sector domain that are using blockchain technology. To give insight into the application of blockchain technology in the energy sector, a case of the application of blockchain technology in P2P trading in electrical-vehicle charging is discussed. At the end, some possible areas of research in the application of blockchain technology in the energy sector are discussed.
Matthias Grundmann, Hedwig Amberg, Hannes Hartenstein
Bitcoin is based on a P2P network that is used to propagate transactions and blocks. While the P2P network design intends to hide the topology of the P2P network, information about the topology is required to understand the network from a scientific point of view. Thus, there is a natural tension between the 'desire' for unobservability on the one hand, and for observability on the other hand. On a middle ground, one would at least be interested on some statistical features of the Bitcoin network like the number of peers that participate in the propagation of transactions and blocks. This number is composed of the number of reachable peers that accept incoming connections and unreachable peers that do not accept incoming connections. While the number of reachable peers can be measured, it is inherently difficult to determine the number of unreachable peers. Thus, the number of unreachable peers can only be estimated based on some indicators. In this paper, we first define our understanding of unreachable peers and then propose the PAL (Passive Announcement Listening) method which gives an estimate of the number of unreachable peers by observing ADDR messages that announce active IP addresses in the network. The PAL method allows for detecting unreachable peers that indicate that they provide services useful to the P2P network. In conjunction with previous methods, the PAL method can help to get a better estimate of the number of unreachable peers. We use the PAL method to analyze data from a long-term measurement of the Bitcoin P2P network that gives insights into the development of the number of unreachable peers over five years from 2015 to 2020. Results show that about 31,000 unreachable peers providing useful services were active per day at the end of the year 2020. An empirical validation indicates that the approach finds about 50 % of unreachable peers that provide useful services.
Jie Song, Pengyi Zhang, Mohammed Alkubati, Yubin Bao · 5 authors
Due to the complexity of blockchain technology, it usually costs too much effort to build, maintain and monitor a blockchain system that supports a targeted application. To this end, the emerging “Blockchain as a Service” (BaaS) makes the blockchain and distributed ledgers more accessible, particularly for businesses, by reducing costs and overheads. BaaS combines the high computing power of cloud computing, the pervasiveness of IoT and the decentralization of blockchain, allowing people to build their own applications while ensuring the transparency and openness of the system. This paper surveys the research outputs of both academia and industry. First, it introduces the representative architectures of BaaS systems and then summarizes the research contributions of BaaS from the technologies for service provision, roles, container and virtualization, interfaces, customization and evaluation. The typical applications of BaaS in both academic and practical domains are also introduced. At present, the research on the blockchain is abundant, but research on BaaS is still in its infancy. Six challenges of BaaS are concluded in this paper for further study directions.
The ecosystem inherent within currently deployed Internet of Things (IoT) systems is that of low-powered devices equipped with sensors that consume data. The data these devices collect is then stored in use-case specific applications, which are connected through application layer gateways that allow these devices to connect to third party cloud storage platforms for further processing. This stratified architecture has created data silos that introduce complexities such as limited user control and lack of solicitation regarding the usage of user data. The constant proliferation of IoT devices deployed in smart cities which include smart university campus (SUC) has resulted in the need for the development of IoT architecture models which are data-centric. In this paper a blockchain- based architecture model, and specifically, the distributed ledger inherent within the Ethereum blockchain, combined with the Proof Of Authority (POA) consensus mechanism, are proposed as a potential solution to developing a proof of concept architecture model that is data-centric. The proposed architecture model will be tested against with application specific use-cases in a simulated environment within the context of a SUC which is subsumed by a smart city.
Network topology is one of the major factors in defining the behavior of a network. In the present scenario, the demand for network security has increased due to an increase in the possibility of attacks by malicious users. In this paper, a blockchain-based system is suggested for securely discovering and storing networks. Techniques such as cloud-based storage systems are not efficient and are lacking in trust, privacy, security, and data control. The blockchain-based technique suggested in this paper is capable of resolving these challenges. Experiments were performed using Mininet, Cisco Packet Tracer, and Ethereum blockchain with the network inference algorithm. This algorithm is capable of inferring the network topology even when only partial information regarding the network is available. The results obtained clearly show that the network is resistant to malicious users and various external attacks, making the network robust.
Blockchain is becoming more and more popular in various fields. Since the information transmission mode of the blockchain is data broadcasting, the traditional TCP/IP network cannot support the blockchain system well, but the Named-Data Networking (NDN) could be a good choice because of its multi-path forwarding and intra-network caching functions. In this article, we propose a new blockchain information transmission acceleration strategy (AITS) combining with graph theory and probability theory based on the NDN architecture. We select some more important nodes in the network as “secondary nodes”, and give them more bandwidth and cache space to assist the NDN network in data transmission. In order to select the correct node as the secondary node, we present a method to calculate the number of secondary nodes, and give the function to calculate the importance of each node. The simulation results show that in complex networks, the proposed method has superior performance in accelerating information transmission and reducing data overhead.
Peer-to-peer (p2p) content delivery is promising to reduce the cost of traditional CDNs and complement the decentralized storage networks such as Filecoin. However, reliable p2p delivery requires proper enforcement of delivery fairness, i.e., the deliverers should be rewarded according to their in-time delivery. Unfortunately, most existing studies on delivery fairness are based on non-cooperative game-theoretic assumptions that are arguably unrealistic in the ad-hoc p2p setting. We for the first time put forth the expressive yet still minimalist securities for p2p content delivery, and give two efficient solutions FairDownload and FairStream via the blockchain for p2p downloading and p2p streaming scenarios, respectively. Our designs not only guarantee delivery fairness to ensure deliverers be paid (nearly) proportional to his in-time delivery, but also ensure the content consumers and content providers to be fairly treated. The fairness of each party can be guaranteed when the other two parties collude to arbitrarily misbehave. Moreover, the systems are efficient in the sense of attaining asymptotically optimal on-chain costs and optimal deliverer communication. We implement the protocols to build the prototype systems atop the Ethereum Ropsten network. Extensive experiments done in LAN and WAN settings showcase their high practicality.