Blockchain serving as an unalterable ledger, has received widespread attentions recently, which allows carrying out transactions with a decentralized matter. Applications with blockchain technology are springing up. However, financial applications especially in bank liquidation system are still facing big challenges. This paper first presents a consensus combined delegated-proof-of-stake protocol and BFT algorithm together. At the same time, using parallel idea and redesigned blockchain structure make the system more efficiency.
Bitcoin cryptocurrency has risen in popularity. Therefore, it not only attracts users to use it, but also it attracts the malware developers to attack it. While online Bitcoin wallets allow users to conveniently store and manage their bitcoins, they are vulnerable to several attacks.
Sheng Wang, Tien Tuan Anh Dinh, Qian Lin, Zhongle Xie · 10 authors
Existing data storage systems offer a wide range of functionalities to accommodate an equally diverse range of applications. However, new classes of applications have emerged, e.g., blockchain and collaborative analytics, featuring data versioning, fork semantics, tamper-evidence or any combination thereof. They present new opportunities for storage systems to efficiently support such applications by embedding the above requirements into the storage. In this paper, we present ForkBase, a storage engine specifically designed to provide efficient support for blockchain and forkable applications. By integrating the core application properties into the storage, ForkBase not only delivers high performance but also reduces development effort. Data in ForkBase is multi-versioned, and each version uniquely identifies the data content and its history. Two variants of fork semantics are supported in ForkBase to facilitate any collaboration workflows. A novel index structure is introduced to efficiently identify and eliminate duplicate content across data objects. Consequently, ForkBase is not only efficient in performance, but also in space requirement. We demonstrate the performance of ForkBase using three applications: a blockchain platform, a wiki engine and a collaborative analytics application. We conduct extensive experimental evaluation of these applications against respective state-of-the-art system. The results show that ForkBase achieves superior performance while significantly lowering the development cost.
Bitcoin is a peer-to-peer electronic currency without central bank controlling. Nowadays, increasing amount of people are engaged in the mining of Bitcoin for great profits. However, in the Bitcoin system, the more participants in the system, the greater computation power of the whole network and the less efficiency in the output of the coin, since large computational power of the whole Bitcoin system will lead to increased difficulty for a single miner to mine a new data block. At the same time, when more than 51% computing power is controlled by a single node, it could destroy the Bitcoin system. In order to reduce ineffective mining behaviors, one would wish to employ the optimal selection mechanism of different miners. This paper will mainly develop the model in which small miners (those who have relative smaller computational power in a block mining) join the major ones based on revenue, computational power cost, and other elements of the process comparing to the current model (when they work separately).
Lei Xu, Lin Chen, Zhimin Gao, Shouhuai Xu · 5 authors
Public blockchains provide a decentralized method for storing transaction data and have many applications in different sectors. In order for users to track transactions, a simple method is to let them keep a local copy of the entire public ledger. Since the size of the ledger keeps growing, this method becomes increasingly less practical, especially for lightweight users such as IoT devices and smartphones. In order to cope with the problem, several solutions have been proposed to reduce the storage burden. However, existing solutions either achieve a limited storage reduction (e.g., simple payment verification), or rely on some strong security assumption (e.g., the use of trusted server). In this paper, we propose a new approach to solving the problem. Specifically, we propose an \underline{e}fficient verification protocol for \underline{p}ublic \underline{b}lock\underline{c}hains, or EPBC for short. EPBC is particularly suitable for lightweight users, who only need to store a small amount of data that is {\it independent of} the size of the blockchain. We analyze EPBC's performance and security, and discuss its integration with existing public ledger systems. Experimental results confirm that EPBC is practical for lightweight users.
The blockchain technology is a new innovation with the potential to disrupt the\nworld as we currently know it, despite several limitations and challenges to overcome.\nOne of these challenges for software producing organizations is selecting the\nright technology for their case. In this research, we haveve identified this selection\nprocess as a multi-criteria decision making problem. Based on this we have created\na Decision Support System which aids developers during the technology selection\nprocess of blockchain platforms. Contemporary solutions to this problem were only\nrather simplistic decision-trees, which struggle with complexity and adaptations.\nThe novelty of this Decision Support System lies in being a feature-based artifact\nwhich incorporates ISO Software Quality Aspects and feature prioritization based\non the MoSCoW-technique. These contemporary generic blockchain features have\nbeen gathered through nine interviews with blockchain experts. Based on prioritized\nfeatures as input, the Decision Support System gives a score for feasible solutions\n(e.g. Ethereum or Hyperledger) as result. This Decision Support System was\nevaluated in three different case-studies for organization creating blockchain-based\nsolutions. In addition to this, the artifact has been validated by a blockchain-domain\nexpert. The main difficulties and obstacles of this whole research were grounded in\nthe immaturity of the blockchain domain as a whole.
With increasing popularity, the scalability of blockchain-based crypto-currencies becomes an urgent concern. Bitcoin, among other crypto-currencies, have known limitations in transaction throughput and speedbut no agreed upon solution. Many of the proposals increasing throughput also increase the load on the Bitcoin network. Lightning is a proposal enabling payments to be conducted without affecting the Bitcoin network. Lightning is a protocol using payment channels to enable instant and cheap payments using the blockchain for security. With Lightning, payments can be sent through a network of nodes connected by payment channels. In this thesis, the current state of Lightning is explored and an evaluation for use on Bitcoin exchanges is performed. The usability, privacy and security of Lightning are the topics evaluated. In order to evaluate the usability, an exchange interface application was built allowing deposits and withdrawals using Lightning. The protocol specification and relevant literature are examined in order to evaluate the security and privacy of Lightning. The exchange interface showed that Lightning can be integrated into an exchange and provide a fast and cheap way to deposit and withdraw money for clients. In this paper some integration designs are proposed and ways to improve the client user experience are discussed. The Lightning node implementations need to mature a bit before real usage and there are some security issues that also need to be considered. With monitoring and network analysis the privacy can be compromised.
This paper proposes optimization mechanisms for a multi – layered IoT network model, backed up by Blockchain Technology. This paper focuses on optimizing the computational load such that the model can meet the feasible conditions for deployment purpose. Though, dividing the IoT network into multiple layers reduces the computational load at each stage, the load split isn’t quite proportional to the amount of work done at each level. Flexibility to monitor computational load at each level and distribute the workload has been introduced at each level.
Internet of Things (IoT) means that physical objects will be able to interact and communicate via embedded systems. This will lead to a distributed network of devices that can communicate with both humans and each other. One application area is in improving supply chain management. The goal in supply chains is to move a product or a service from the producer to the customer as efficient as possible. Implementation of IoT will have many benefits but it also raises security issues that can affect integrity, security and privacy for both individuals and companies. In 2009, Satoshi Nakamoto created bitcoin and more importantly, blockchain. Blockchain is a ledger of facts, data is not stored in only one network with a common processor, but it is distributed among all the clients on the network. This technology may be a solution to some problems that IoT are facing. This paper looks into up to date research of blockchain and IoT with the purpose to study blockchain as a potential solution to secure IoT data management within supply chains. Both blockchain and IoT are relatively new research areas with little existing research, which support our use of a qualitative inductive method. Semi-structured interviews, which will be further explained in the methodology section, have been conducted with people working within the fields of blockchain, IoT and supply chain. The result indicates that blockchain can be used to secure data management within any given supply chain that uses IoT technology, but blockchain should be seen as a tool, and not as a complete solution. Many of the security issues within IoT are related to the devices and blockchain will not be able to provide a solution to these problems. Blockchain can however be used for handling information, securing identities, traceability of goods, transactions being made without human interaction, automated storage management and time stamped actions to name some examples. There are still barriers to make these benefits work in reality but there is a lot of research currently on-going, trying to make it happen.
The interest has grown around Bitcoin as a trustless and decentralized digital payment service. Along with the increase in users and transactions, Bitcoin suffers from challenges regarding scalability. Many solutions have been proposed over the years, but Bitcoin is still struggling with finding the solution that suits everyone. Lightning Network as one of the most promising solutions, will be in the scope of this thesis, along with why such a solution is needed.\n\nBy investigating Bitcoin, scalability challenges and proposed solutions, we evaluated Bitcoin s future. We explore challenges such as propagation time, block size and energy consumption. Increasing the block size, changing the consensus algorithm and off-chain payments are discussed. The Lightning Network as an off-chain solution is investigated further in-depth. Challenges and consequences of implementing the Lightning Network are discussed. Furthermore, this thesis discusses whether the Lightning Network is the solution Bitcoin needs or not.
Doaa Mohey El-Din M. Hussein, Mohamed Hamed, Nour Eldeen
A Blockchain is considered the main mechanism for Bitcoin concurrency. A Blockchain is known by a public ledger and public transactions stored in a chain. The properties of blockchain demonstrate in decentralization as distribution blocks, stability, anonymity, and auditing. Blockchain can enhance the results of network efficiency and improve the security of network. It also can be applied in several fields like financial and banking services, healthcare systems, and public services. However, the research is still opening at this point. It includes a big number of technical challenges which prevents the wide application of blockchain, for example, scalability problem, privacy leakage, etc. This paper shows a proposed comprehensive study of blockchain technology. It also examines the research efforts in blockchain. It presents a proposed blockchain lifecycle which refers to an evolution and a linked ring between business process management improvement and Internet-of-Things concepts. Then, this paper presents a practical proof of this relationship for smart city. It presents a new algorithm and a proposed blockchain framework for 38 blocks (which recognized as smart-houses). Finally, the future directions are well presented in blockchain field.
Public key server is a simple yet effective way of key management in secure end-to-end communication. To ensure the trustworthiness of a public key server, transparent log systems such as CONIKS employ a tamper-evident data structure on the server and a gossiping protocol among clients in order to detect compromised servers. However, due to lack of incentive and vulnerability to malicious clients, a gossiping protocol is hard to implement in practice. Meanwhile, alternative solutions such as EthIKS are not scalable. This paper presents Trusternity, an auditing scheme relying on Ethereum blockchain that is easy to implement, scalable and inexpensive to operate.
After the introduction of Bitcoin, blockchain has made its way through numerous applications and been adopted by various communities. A number of implementations exist today providing a platform to carry on business with ease. However, it is observed the scalability of blockchain still remains an issue. Also, none of the framework can claim the ability to handle Big Data and support to perform analytics, which is an important and integral facet of current world of business. We propose HBasechainDB, a scalable blockchain-based tamper-proofed Big Data store for distributed computing. HBasechainDB adds the blockchain characteristics of immutability and decentralization to the HBase database in the Hadoop ecosystem. Linear scaling is achieved by pushing computation to the data nodes. HBasechainDB comes with inherent property of efficient big data processing as it is built on Hadoop ecosystem. HBasechainDB also makes adaptation of blockchain very easy for those organizations whose business logic are already existing on Hadoop ecosystem. HBasechainDB can be used as a tamper-proof, decentralized, distributed Big Data store.
The rise of cryptocurrency as a new sui generis asset class creates a need for a new classification scheme to cover the wide range of functionality for which tokens can be used. By differentiating tokens based on their functional attributes, cryptocurrency tokens can be categorised into crypto-transaction tokens (which act as a cash substitute); crypto-fuel tokens (which underpin generic blockchain applications); and crypto-voucher tokens (which can be exchanged for a predefined asset). This classification is applied to identify important issues when considering whether to participate in a cryptocurrency system, such as the impact of potential forks, token supply expectations and the level of dependence on a few operators (entity-dependence). For crypto-transaction tokens (and crypto-fuel tokens if used in a similar or overlapping role) it shows the importance of the token being seen as a “better” form of money. For crypto-fuel tokens, the popularity of blockchain applications and the utility of the crypto-fuel system in application development is vital. For crypto-voucher tokens, the value of the underlying asset, the token’s exchangeability for that asset and the importance of a digital representation should be considered by participants. The interplay between fundamentals and speculation as drivers of price is considered.An erratum to this article has been published at as DOI: https://doi.org/10.5195/ledger.2018.151.
A useful blockchain should possess the following properties, one or more of which many existing blockchain systems lack: 1) A sound consensus protocol. 2) An efficient transaction-processing system. 3) Immutability of history. 4) Decentralization. 5) An effective avenue for hard-forks and rule changes. We propose a system named the “Verex Blockchain” that will fulfill these requirements. This system employs an “Assigned-Majority-Validation” consensus protocol whereby only nodes within a specialized, designated network may vote on the correct state of the blockchain and add new blocks of transactions without proof of work or stake. New nodes to this network must be approved by existing nodes. These nodes will be controlled by entities with high public visibility such as governments or multinational technology companies, whose identities and actions will be made fully transparent on the blockchain. Transactions will be charged fees in cryptocurrency according to a fixed and known fee schedule, which will be earned by nodes in the designated network. Any user in the world may download the blockchain, receive and verify updates, and submit transactions, but only nodes in the specialized network may write updates to the blockchain.
The recent emergence of a distributed technology named blockchain, clearly created a new point of view in the data storing and data distribution fields. If on one hand blockchain is mainly known for Bitcoin (an auto-regulated decentralized digital currency), on the other hand it has the potential to set up an auto regulated economy.In this thesis, the blockchain technology will be analyzed and described starting from P2P architecture and its origin in 2009 Satoshi Nakamoto’s whitepaper, and leading to the most up to date blockchains. The advantages and disadvantages of such architecture will be pointed out keeping in mind the security, speed and cost of such infrastructure.While Real Estate companies have often anticipated the technological innovations, land registries, instead, derive and keep a working manner which is extremely old and out of date: made of unclear procedures and wet signatures. The market needs and legislation will be researched mainly referring to other works and integrated with a technical point of view with particular focus on the decentralization of such systems.After analyzing the flow, problems and flaws of the current system, a new proposal will be researched, in particular trying to minimize the dead time in between the different steps of the mortgage, increase transparency, as well as reducing dependence on the central authorities, leading to more convenient interactions among the properties’ stakeholders. An attractive low capitalization decentralized financial product will also be proposed and implemented able to lower the interest rate and create a profitable investment with low risk, low interest and durable in time.Secure and ad-hoc algorithms will be presented and, in a later section, analyzed in combination with different blockchain technologies. Scalability and performance will also be evaluated, taking into account all the current technology limitations and the near future opportunities.
Distributed ledger technologies (DLTs) are currently dominating the field of distributed systems research and development. The Ethereum blockchain is emerging as a popular DLT platform for developing software and applications. Several challenges in Ethereum software development are the complex nature of working with DLTs, the lack of tools for developing on this DLT, and poor documentation of concepts for DLT developers. In this thesis, we provide building blocks that reduce the complexity of DLT operations and lower the barrier to entry into DLT development. We do this by providing a Node.js library, Ethereum-Easy, that simplifies operations on Ethereum. We implement this library into a sample application called Rock, Paper, Scissors (RPS) and built a continuous delivery, continuous integration pipeline for deploying Ethereum code (Jenk-Thereum). This thesis aims to make development on DLTs easier, quicker, and less expensive.
As the underlying technology in Bitcoin, the blockchain technology has gained wide attention. Blockchain is a kind of feasible method to solve the consistency problem of distributed system. Consensus mechanism is the core of the blockchain technology. Delicate consensus mechanism can improve system performance and promote the application of blockchain in many fields. Based on the consensus mechanisms in existing design of blockchain, this paper summarizes the basic consensus mechanisms including proof of work, proof of stake and Byzantine consistency agreement, and evaluates them from various aspects such as security, scalability, performance, etc. The future research on the blockchain consensus mechanism will be based on the different characteristics of the consensus mechanisms, and design should be carried out around the combination of different consensus mechanisms.
Blockchain is a technology to exchange digital assets including cryptocurrencies, data, software, patents etc. Blockchain is designed in various types depending on different architectures and configurations for different purposes. The mathematical and cryptographic mechanisms and consensus algorithms, implemented in the Blockchain, guarantee trust, security, integrity and availability of transactions between participants. \nThis thesis is aimed to consider mathematical foundation and algorithmic aspects of Ethereum from the base network to high level of its functionality with the comparison to mathematical mechanisms of Bitcoin. In this thesis we describe Ethereum as stack of layers. Our mission is to extract cryptographic and mathematical mechanisms implemented in each layer. \nWe present how hash function is utilized to construct cost function and Hashcash protocol. Hashcash protocol is implemented in Proof of Work (PoW) mechanism. Also, we explain how hash function is used to connect blocks in the chain of blocks and how hash function is used to organize transactions in a Merkle tree and in a Merkle-Patricia-trie. \nThis thesis describes how Elliptic Curve Digital Signature Algorithm (ECDSA) and Lamport signing algorithm provide integrity of transactions. Elliptic Curve Integrated Encryption Scheme (ECIES) is hybrid encryption scheme which is utilized to provide confidentiality of transactions. The Elliptic Curve Cryptography (ECC) is used to disguise identities in both Bitcoin and Ethereum network. The new approaches to provide privacy are Ring signatures and Zk-Snarks. \nThis thesis also explains Bloom filter structure in Ethereum. The Bloom filter is a probabilistic data structure to test membership of elements in big data bases.
Bruno Tavares, Filipe Figueiredo Correia, André Restivo, João Pascoal Faria · 5 authors
The applications of the blockchain technology are still being discov-ered. When a new potential disruptive technology emerges, there is a tendency to try to solve every problem with that technology. However, it is still necessary to determine what approach is the best for each type of application. To find how distributed ledgers solve existing problems, this study looks for blockchain frameworks in the academic world. Identifying the existing frameworks can demonstrate where the interest in the technology exists and where it can be miss-ing. This study encountered several blockchain frameworks in development. However, there are few references to operational needs, testing, and deploy of the technology. With the widespread use of the technology, either integrating with pre-existing solutions, replacing legacy systems, or new implementations, the need for testing, deploying, exploration, and maintenance is expected to in-tensify.