Central Bank Digital Currency (CBDC) is gaining popularity due to its potential benefit. However, experiments to explore the Distributed Ledger Technology (DLT) based CBDC is mostly done in the wholesale area, not in the retail area which has more impact on the public. This paper proposes a CBDC design where the digital currency or token that is distributed in the wholesale DLT network, can be widely accessed by the public through accounts provided by commercial banks. The proposed design maintains reliability as well as user-friendliness and scalability. This paper describes the architecture, infrastructure, and business process of the proposed design.
Divija Swetha Gadiraju, V. Lalitha, Vaneet Aggarwal
Blockchain is a distributed ledger with wide applications. Due to the\nincreasing storage requirement for blockchains, the computation can be afforded\nby only a few miners. Sharding has been proposed to scale blockchains so that\nstorage and transaction efficiency of the blockchain improves at the cost of\nsecurity guarantee. This paper aims to consider a new protocol,\nSecure-Repair-Blockchain (SRB), which aims to decrease the storage cost at the\nminers. In addition, SRB also decreases the bootstrapping cost, which allows\nfor new miners to easily join a sharded blockchain. In order to reduce storage,\ncoding-theoretic techniques are used in SRB. In order to decrease the amount of\ndata that is transferred to the new node joining a shard, the concept of exact\nrepair secure regenerating codes is used. The proposed blockchain protocol\nachieves lower storage than those that do not use coding, and achieves lower\nbootstrapping cost as compared to the different baselines.\n
Sebastian Bănescu, Martin Derka, Jan Gorzny, Sung-Shine Lee · 5 authors
Smart contracts are code fragments that automatically execute on distributed ledgers or blockchains. Smart contracts are typically executed by all block producers on a proof-of-work blockchain. As a result, smart contracts have their computational resources limited in order to prevent denial of service attacks on the blockchain, which would decrease its responsiveness, i.e. block creation throughput. Subsequently, updating values for a large number of records becomes infeasible on the scale of existing centralized services. We present a solution to this problem, when all numerical values of records need to be updated, i.e. in/de-creased proportionally. Our solution uses a mechanism similar to cryptocurrency tokens to track record values and enables constant-time updates for these values.
For many applications, data are worthy only if they are trustworthy. The concept of trust is sometimes elusive, and yet it is fundamental in data management. Even when not expressed explicitly, the correctness of computations and reliability of applications depend on trustworthy management of the data. These notions received new attention with the advent of blockchain and distributed ledger technology.
The full-replication data storage mechanism, as commonly utilized in existing blockchains, is the barrier to the system's scalability, since it retains a copy of entire blockchain at each node so that the overall storage consumption per block is O(n) with n participants. Yet another drawback is that this mechanism may limit the throughput in permissioned blockchain. Moreover, due to the existence of Byzantine nodes, existing partitioning methods, though widely adopted in distributed systems for decades, cannot suit for blockchain systems directly, so that it is critical to devise new storage mechanism for blockchain systems. This article proposes a novel storage engine, called BFT-Store, to enhance storage scalability by integrating erasure coding with Byzantine Fault Tolerance (BFT) consensus protocol. The first property of BFT-store is that the storage consumption per block can be reduced to O(1) for the first time, which enlarges overall storage capability when more nodes attend the blockchain. Second, we design an efficient online re-encoding protocol for storage scale-out and a hybrid replication scheme to enhance reading performance. Analysis in theory and extensive experimental results illustrate the scalability, availability and efficiency of BFT-Store via the implementation in an open-source permissioned blockchain Tendermint.
As digital currency wallets are gaining popularity, security incidents related to them are also increasing. They lead to the disclosure of users' private information and security threats of users' assets. This article analyzes the security risks of digital wallets in Android, which is the most popular mobile operating system. it first establishes the threat model and the security goals, and then analyzes the attack surface and attack vectors from the aspects of wallet apps and the Android system. Experiments are conducted on two realworld digital currency wallet apps, and the results reveal several serious security risks in these apps, which highlight the necessity and importance of developing secure cryptocurrency wallets.
Jun Li, Alex Grintsvayg, Jeremy D. Kauffman, Charles B. Fleming
Despite the critical need of publishing and consuming content online, a centralized content platform such as Amazon or YouTube may not always have their policy and practice aligned with the interest of their users and could be rent-seeking, censorious, and frequently exploitative, whereas a peer-to-peer solution such as BitTorrent may suffer from issues of content discovery, legitimacy, monetization, verifiable publisher identity, and poor user experience. In this paper, to improve significantly over both options, we propose a new approach called LBRY that enables a decentralized online content marketplace. In particular, it uses a blockchain to build a decentralized content platform controlled by the community, and allows its users to publish, host, find, access, download, and pay for content with ease. LBRY introduces a new naming scheme that gives users the full control of the names of their content, and uses a blockchain to not only support a digital currency (LBC) and transparent decentralized ledger, but also allow every user to access a synchronized name space and a global index of content metadata, thus supporting a new paradigm of digital content distribution. We detail how LBRY works in this paper, including how it designs its data structures for content, content metadata, and a novel content naming space; how it uses the blockchain to manage and synchronize the name space and implement an index for content metadata in order to support content sharing and purchase; and how it handles several issues in running LBRY.
The protocol for cryptocurrencies can be divided into three parts, namely consensus, wallet, and networking overlay. The aim of the consensus part is to bring trustless rational peer-to-peer nodes to an agreement to the current status of the blockchain. The status must be updated through valid transactions. A proof-of-work (PoW) based consensus mechanism has been proven to be secure and robust owing to its simple rule and has served as a firm foundation for cryptocurrencies such as Bitcoin and Ethereum. Specialized mining devices have emerged, as rational miners aim to maximize profit, and caused two problems: i) the re-centralization of a mining market and ii) the huge energy spending in mining. In this paper, we aim to propose a new PoW called Error-Correction Codes PoW (ECCPoW) where the error-correction codes and their decoder can be utilized for PoW. In ECCPoW, puzzles can be intentionally generated to vary from block to block, leading to a time-variant puzzle generation mechanism. This mechanism is useful in repressing the emergence of the specialized mining devices. It can serve as a solution to the two problems of recentralization and energy spending.
Increasing presence of distributed energy resources (DERs) is evolving electricity distribution system to decentralized and active networks. Utilising the data emerging from such networks is an essential step for developing sustainable future energy systems, as such systems must be closely monitored and managed to avoid blackouts and failures. The datasets within energy systems are very large, must be immutable, are often interrelated, yet owned by competing organisations. How then should these datasets be stored and shared? This is the main focus of my research. To provide a reliable way of collecting, storing, sharing, and analysing energy systems data, I propose to use the newly emerging distributed ledger technology. I will work towards developing a middleware-like platform over distributed ledgers, which would aim to provide a reliable data storage solution for immutable energy datasets, while also maintaining relationships between the datasets and addressing the read and write latency and scalability problems of the present distributed ledgers.
This demonstration presents vChain, a blockchain system that ensures query integrity. With the proliferation of blockchain applications and services, there has been an increasing demand for querying the data stored in a blockchain database. However, existing solutions either are at the risk of losing query integrity, or require users to maintain a full copy of the blockchain database. In comparison, by employing a novel verifiable query processing framework, vChain enables a lightweight user to authenticate the query results returned from a potentially untrusted service provider. We demonstrate its verifiable query operations, usability, and performance with visualization for better insights. We also showcase how users can detect falsified results in the case that the service provider is compromised.
In the blockchain-based, distributed computing platform Ethereum, programs called smart contracts are compiled to bytecode and executed on the Ethereum Virtual Machine (EVM). Executing EVM bytecode is subject to monetary fees---a clear optimization target. Our aim is to superoptimize EVM bytecode by encoding the operational semantics of EVM instructions as SMT formulas and leveraging a constraint solver to automatically find cheaper bytecode. We implement this approach in our EVM Bytecode SuperOptimizer ebso and perform two large scale evaluations on real-world data sets.
Over the past few years, massive cyberattacks have dominated the public imagination. Most \nAmericans have been directly affected by data breaches and an overwhelming majority believe \nthat they are no longer in control of their data. At the same time, there are important applications in \nwhich the aggregation of private data is unavoidable. Not surprisingly, there has been considerable \ninterest in developing protocols for secure multi-party computation (MPC), i.e., N parties providing \nprivate inputs to jointly compute some function f. Recent developments in MPC have led to leaps \nin efficiency and MPC is quickly becoming a practical approach for privacy-centric distributed \napplications. As MPC applications become deployed, guaranteeing the security of these protocols, \neven when interacting with other applications, is essential. The standard approach to showing \nsecurity of MPC protocols under arbitrary composition is through the universal composability (UC) \nframework. There has been much prior work on this topic; however, most previous work either \nmakes synchronicity assumptions or does not guarantee output delivery in the presence of even \none fault. For practical MPC applications, though, dealing with asynchronicity and robustness is \nessential. In this thesis, we describe two new keywords, eventually and leak, that aid in defining \nprotocols in the asynchronous world and define wrappers that implement these within the UC \nframework. We then use this novel wrapper to give a UC-realization of a reliable broadcast primitive, by means of Bracha’s classic protocol. Finally, we define and prove a realization of what we call the \nsmart contract model of MPC, which serves as a UC-idealization of asynchronous, robust MPC.
Open access
Advancements in Semiconductor Devices and Circuit Design
This paper introduces a new approach to reduce end-to-end costs in large-scale replicated systems built under a Byzantine fault model. Specifically, our approach transforms a given replicated state machine (RSM) to another RSM where nodes incur lower costs by delegating state machine execution: an untrusted prover produces succinct cryptographic proofs of correct state transitions along with state changes, which nodes in the transformed RSM verify and apply respectively.To realize our approach, we build Piperine, a system that makes the proof machinery profitable in the context of RSMs. Specifically, Piperine reduces the costs of both proving and verifying the correctness of state machine execution while retaining liveness-a distinctive requirement in the context of RSMs. Our experimental evaluation demonstrates that, for a payment service, employing Piperine is more profitable than naive reexecution of transactions as long as there are > 104nodes. When we apply Piperine to ERC-20 transactions in Ethereum (a real-world RSM with up to 105nodes), it reduces per-transaction costs by 5.4× and network costs by 2.7×.
Zachary Painter, Pradeep Kumar Gayam, Victor Cook, Damian Dechev
Popular blockchains such as Bitcoin or Ethereum provide a transaction isolation level of READ-COMMITTED. This provides difficulties when state changes many times per block interval. Hash-Mark-Set (HMS) alleviates this problem by enabling READ-UNCOMMITTED transactions for state variables. However, the current HMS implementation relies on a sequential algorithm and is susceptible to redundant calculations. As modern processors rely more heavily on parallel algorithms to leverage multiple cores for speedup, sequential algorithms see less benefit from hardware improvements. This paper proposes a lock-free HMS to make use of thread-safe techniques and other optimizations to improve the performance of the HMS algorithm and reduce the latency of read-uncommitted state variable accesses. In our experiments, the proposed algorithm experiences an average 6.4× increase in performance up to 128 go-routines, and a maximum 11.1× increase.
Manoharan Ramachandran, Niaz Chowdhury, Allan Third, John Domingue · 6 authors
Over-centralisation of data leads to tampering and sharing user information without the consent of the owners. This problem has been studied extensively in recent times providing separate solutions involving distributed storage, Blockchain technology and Solid Pods. Individually these solutions are not sufficient to build realistic applications in a decentralised environment; however, a combination of them can effectively provide more powerful and useful use-cases. In this paper, we propose the methods of combining Solid Pods and distributed ledgers in introducing complete decentralisation of data with total user-control, keeping the integrity of the stored information intact through Blockchain-based verification. We demonstrated multiple configurations of our solutions, offering several new use-cases in various sectors. These configurations introduce new dimensions on the Web and mobile applications’ data storage that developers can benefit from building Distributed Applications (DApps) in a complete decentralised environment.
The full-replication data storage mechanism, as commonly utilized in existing blockchain systems, is lack of sufficient storage scalability, since it reserves a copy of the whole block data in each node so that the overall storage consumption per block is O(n) with n nodes. Moreover, due to the existence of Byzantine nodes, existing partitioning methods, though widely adopted in distributed systems for decades, cannot suit for blockchain systems directly, thereby it is critical to devise a new storage mechanism. This paper proposes a novel storage engine, called BFT-Store, to enhance storage scalability by integrating erasure coding with Byzantine Fault Tolerance (BFT) consensus protocol. First, the storage consumption per block can be reduced to O(1), which enlarges overall storage capability when more nodes join blockchain. Second, an efficient online re-encoding protocol is designed for storage scale-out and a hybrid replication scheme is employed to improve reading performance. Last, extensive experimental results illustrate the scalability, availability and efficiency of BFT-Store, which is implemented on an open-source permissioned blockchain Tendermint.
Smart contracts have enabled blockchain systems to evolve from simple cryptocurrency platforms, such as Bitcoin, to general transactional systems, such as Ethereum. Catering for emerging business requirements, a new architecture called execute-order-validate has been proposed in Hyperledger Fabric to support parallel transactions and improve the blockchain's throughput. However, this new architecture might render many invalid transactions when serializing them. This problem is further exaggerated as the block formation rate is inherently limited due to other factors beside data processing, such as cryptography and consensus. In this work, we propose a novel method to enhance the execute-order-validate architecture, by reducing invalid transactions to improve the throughput of blockchains. Our method is inspired by state-of-the-art optimistic concurrency control techniques in modern database systems. In contrast to existing blockchains that adopt database's preventive approaches which might abort serializable transactions, our method is theoretically more fine-grained. Specifically, unserializable transactions are aborted before ordering and the remaining transactions are guaranteed to be serializable. For evaluation, we implement our method in two blockchains respectively, FabricSharp on top of Hyperledger Fabric, and FastFabricSharp on top of FastFabric. We compare the performance of FabricSharp with vanilla Fabric and three related systems, two of which are respectively implemented with one standard and one state-of-the-art concurrency control techniques from databases. The results demonstrate that FabricSharp achieves 25% higher throughput compared to the other systems in nearly all experimental scenarios. Moreover, the FastFabricSharp's improvement over FastFabric is up to 66%.
Cryptocurrencies that are based on Proof-of-Work (PoW) often rely on special purpose hardware to perform so-called mining operations that secure the system, with miners receiving freshly minted tokens as a reward for their work. A notable example of such a cryptocurrency is Bitcoin, which is primarily mined using application specific integrated circuit (ASIC) based machines. Due to the supposed profitability of cryptocurrency mining, such hardware has been in great demand in recent years, in-spite of high associated costs like electricity. In this work, we show that because mining rewards are given in the mined cryptocurrency, while expenses are usually paid in some fiat currency such as the United States Dollar (USD), cryptocurrency mining is in fact a bundle of financial options. When exercised, each option converts electricity to tokens. We provide a method of pricing mining hardware based on this insight, and prove that any other price creates arbitrage. Our method shows that contrary to the popular belief that mining hardware is worth less if the cryptocurrency is highly volatile, the opposite effect is true: volatility increases value. Thus, if a coin's volatility decreases, some miners may leave, affecting security. We compare the prices produced by our method to prices obtained from popular tools currently used by miners and show that the latter only consider the expected returns from mining, while neglecting to account for the inherent risk in mining, which is due to the high exchange-rate volatility of cryptocurrencies. Finally, we show that the returns made from mining can be imitated by trading in bonds and coins, and create such imitating investment portfolios. Historically, realized revenues of these portfolios have outperformed mining, showing that indeed hardware is mispriced.
The massive redundant data storage and communication in network 4.0 environments have issues of low integrity, high cost, and easy tampering. To address these issues, in this article, a secure data storage and recovery scheme in the blockchain-based network is proposed by improving the decentration, tampering-proof, real-time monitoring, and management of storage systems, as such design supports the dynamic storage, fast repair, and update of distributed data in the data storage system of industrial nodes. A local regenerative code technology is used to repair and store data between failed nodes while ensuring the privacy of user data. That is, as the data stored are found to be damaged, multiple local repair groups constructed by vector code can simultaneously yet efficiently repair multiple distributed data storage nodes. Based on the unique chain storage structure, such as data consensus mechanism and smart contract, the storage structure of blockchain distributed coding not only quickly repair the nearby local regenerative codes in the blockchain but also reduce the resource overhead in the data storage process of industrial nodes. Experimental results show that the proposed scheme improves the repair rate of multinode data by 9% and data storage rate increased by 8.6%, indicating to be promising with good security and real-time performance.
Peng Zhao, Hongbing Cheng, Yicheng Fang, Xiaoqing Wang
The exponential growth of storage space in blockchain network has become a serious problem to hinder the distribution of blockchain and the expansion of blockchain nodes. In this paper. We propose a security strategy for distributed storage blockchains, which can delete part of blockchains so that nodes only store part of a blockchain. We design a kind of semi-full node between full node and light node according to the requirement of the strategy, besides describe the process of deleting block and synchronizing block, and the running logic of the semi-full node. Finally, we perform comprehensive experiments of the truncated MCMC random algorithm. The results show that in the case of multi-node, the truncated block will not affect the block chain network. Compared with the traditional block design, our storage strategies can reduce storage requirements under most of situation, thus enable blockchains to be deployed on mobile or smaller storage computers.
991012879763303412 HKUST Electronic Theses Coverage-directed differential testing of EVM implementations by Hang Xu thesis 2020 x, 37 pages : illustrations ; 30 cm Ethereum virtual machine(EVM) is the heart of the Ethereum infrastructure and functions as the runtime environment for…Read more ›
Most people first encounter blockchain technology by way of cryptocurrencies like Bitcoin. Bitcoin came into existence during the start of the 2008 financial crisis and was first disclosed in October 2008.1Because of the timing and some clear indicators embedded into the first (genesis) block of Bitcoin, we know that a primary reason for developing cryptocurrency was a distrust of large institutions that control the world’s fiat currencies. However, what does currency have to do with media technology?