Peer-to-peer (p2p) content delivery is promising to provide benefits like cost-saving and scalable peak-demand handling in comparison with conventional content delivery networks (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.
As the typical peer-to-peer distributed networks, blockchain systems require each node to copy a complete transaction database, so as to ensure new transactions can by verified independently. In a blockchain system (e.g., bitcoin system), the node does not rely on any central organization, and every node keeps an entire copy of the transaction database. However, this feature determines that the size of blockchain transaction database is growing rapidly. Therefore, with the continuous system operations, the node memory also needs to be expanded to support the system running. Especially in the big data era, the increasing network traffic will lead to faster transaction growth rate. This paper analyzes blockchain transaction databases and proposes a storage optimization scheme. The proposed scheme divides blockchain transaction database into cold zone and hot zone using expiration recognition method based on Least Recently Used (LRU) algorithm. It can achieve storage optimization by moving unspent transaction outputs outside the in-memory transaction databases. We present the theoretical analysis on the optimization method to validate the effectiveness. Extensive experiments show our proposed method outperforms the current mechanism for the blockchain transaction databases.
Enforcement of policy regulations and availability of auditing mechanisms are crucial building blocks for the adoption of distributed payment systems. In this work we review a number of existing proposals for distributed payment systems that offer some form of auditability for regulators. We identify two major distinct lines of work: payment systems that are not privacy-preserving such as Bitcoin, where regulation functionalities are typically tailored for organizations controlling many accounts, and privacy-preserving payment systems where regulation functionalities are typically targeted to user level. We provide a systematization methodology over several axes of characteristics and performance, while highlighting insights and research gaps that we have identified, such as lack of dispute-resolution solutions between the regulator and the entity under audit, and the incompatibility of ledger pruning or off-chain protocols with regulatory requirements. Based on our findings, we propose a number of exciting future research directions.
Blockchain and general purpose distributed ledgers are foundational technologies which bring significant innovation in the infrastructures and other underpinnings of our socio-economic systems. These P2P technologies are able to securely diffuse information within and across networks, without need for trustees or central authorities to enforce consensus. In this contribution, we propose a minimalistic stochastic model to understand the dynamics of blockchain-based consensus. By leveraging on random-walk theory, we model block propagation delay on different network topologies and provide a classification of blockchain systems in terms of two emergent properties. Firstly, we identify two performing regimes: a functional regime corresponding to an optimal system function; and a non-functional regime characterised by a congested or branched state of sub-optimal blockchains. Secondly, we discover a phase transition during the emergence of consensus and numerically investigate the corresponding critical point. Our results provide important insights into the consensus mechanism and sub-optimal states in decentralised systems.
Smart contracts are dependent on oracle systems for their adoption and usability. We perform an empirical study of oracle systems' usage trends and adoption metrics to provide better insight into the health of the smart contract ecosystem. We collect ChainLink usage data on the Ethereum network using a modified Ethereum client and running a full node. We analyze the collected data and present our findings and insights surrounding the usage trends, adoption metrics, oracle pricing and service quality associated with ChainLink on the Ethereum network.
Christoph Egger, Mike Graf, Ralf Küsters, Daniel Rausch · 6 authors
In the past few years blockchains have been a major focus for security research, resulting in significant progress in the design, formalization, and analysis of blockchain protocols. However, the more general class of distributed ledgers, which includes not just blockchains but also prominent non-blockchain protocols, such as Corda and OmniLedger, cannot be covered by the state-of-the-art in the security literature yet. These distributed ledgers often break with traditional blockchain paradigms, such as block structures to store data, system-wide consensus, or global consistency. In this paper, we close this gap by proposing the first framework for defining and analyzing the security of general distributed ledgers, with an ideal distributed ledger functionality, called Fledger, at the core of our contribution. This functionality covers not only classical blockchains but also non-blockchain distributed ledgers in a unified way. To illustrate Fledger, we first show that the prominent ideal block-chain functionalities Gledger and GPL realize (suitable instantiations of) Fledger, which captures their security properties. This implies that their respective implementations, including Bitcoin, Ouroboros Genesis, and Ouroboros Crypsinous, realize Fledger as well. Secondly, we demonstrate that Fledger is capable of precisely modeling also non-blockchain distributed ledgers by performing the first formal security analysis of such a distributed ledger, namely the prominent Corda protocol. Due to the wide spread use of Corda in industry, in particular the financial sector, this analysis is of independent interest. These results also illustrate that Fledger not just generalizes the modular treatment of blockchains to distributed ledgers, but moreover helps to unify existing results.
Achieving the equilibrium between scalability, sustainability and security has prevailed as the ideal solution for decentralized blockchain applications over the last years. Several approaches have been proposed being Ethereum a solid proposal among them. Ethereum is on the path of a major protocol improvement called Ethereum 2.0 (Eth2), implementing Sharding and introducing the Proof-of-Stake (PoS). As the change of consensus mechanism is a delicate matter, this improvement will be achieved through different phases, the first of which is the implementation of the Beacon Chain. The implementation of the latest has been stated with the recent launch of the Eth2 main net. In this work, we introduce an Eth2 network monitor tool, called Armiarma, used to generate a complete analysis of the p2p network of the Eth2 main net. In this paper, we present some of the results of what this Eth2 network monitor can achieve.
Achieving the equilibrium between scalability, sustainability, and security while keeping decentralization has prevailed as the target solution for decentralized blockchain applications over the last years. Several approaches have been proposed by multiple blockchain teams to achieve it, Ethereum being among them. Ethereum is on the path of a major protocol improvement called Ethereum 2.0 (Eth2), implementing Sharding and introducing the Proof-of-Stake (PoS). As the change of consensus mechanism is a delicate matter, this improvement will be achieved through different phases, the first of which is the implementation of the Beacon Chain. As Ethereum1, Eth2 relies on a decentralized peer-to-peer (p2p) network for the message distribution. Up to date, we estimate that there are around 5.000 nodes in the Eth2 main net geographically distributed. However, the topology of this one still prevails unknown. In this paper, we present the results obtained from the analysis we performed on the Eth2 p2p network. Describing the topology of the network, as possible hazards that this one implies.
Blockchain technology has enabled the keeping of a decentralized, tamper-proof, immutable, and ordered ledger of transactional events. Efforts to leverage such a ledger may be challenging when data storage requirements exceed most blockchain protocols' current capacities. Storing large amounts of decentralized data while maintaining system efficiency is the challenge that we target. This paper proposes using the IPFS distributed hash table (DHT) technology to store information immutably and in a decentralized manner to mitigate the high cost of storage. A storage system involving blockchain and other storage systems in concert should be based on immutable data and allow removal of data from malicious users in the DHT. Efficiency is improved by decreasing the overall processing time in the blockchain with the help of DHT technology and introducing an agreement service that communicate with the blockchain via a RESTful API. We demonstrate the applicability of the proposed method and conclude that the combination of IPFS and blockchain provides efficient cryptographic storage, immutable history and overall better efficiency in a decentralized manner.
Since Satoshi Nakamoto launched bitcoin in 2009, there have been many improvements in bitcoin addresses that are required to fulfill newer requirements. These improvements have made the learning curve steeper for a regular user. Many readers do not know the real motivation why certain features are implemented or otherwise. In this paper, the evolution of bitcoin addresses is clearly described so that users can better understand the progress made in bitcoin. This paper also explains the motivation for some features' motivation and why these features were implemented in a certain way.
Services computing can offer a high-level abstraction to support diverse applications via encapsulating various computing infrastructures. Though services computing has greatly boosted the productivity of developers, it is faced with three main challenges: privacy and security risks, information silo, and pricing mechanisms and incentives. The recent advances of blockchain bring opportunities to address the challenges of services computing due to its build-in encryption as well as digital signature schemes, decentralization feature, and intrinsic incentive mechanisms. In this paper, we present a survey to investigate the integration of blockchain with services computing. The integration of blockchain with services computing mainly exhibits merits in two aspects: i) blockchain can potentially address key challenges of services computing and ii) services computing can also promote blockchain development. In particular, we categorize the current literature of services computing based on blockchain into five types: services creation, services discovery, services recommendation, services composition, and services arbitration. Moreover, we generalize Blockchain as a Service (BaaS) architecture and summarize the representative BaaS platforms. In addition, we also outline open issues of blockchain-based services computing and BaaS.
Jonas Theis, Luigi Vigneri, Lin Wang, Animesh Trivedi
Permissionless distributed ledger technologies (DLTs) utilize an underlying peer-to-peer network to disseminate transactions. These types of networks have been shown to be highly heterogeneous. However, current DLTs fail to consider this heterogeneity which can render low-end nodes to be unable to participate in consensus.
Ensuring the integrity of executable binaries is of vital importance to systems that run and depend on them. Additionally, supply-chain attacks and security related bugs demonstrate that binaries, once deployed, may need to be revoked and replaced with updated versions.
Currently, all blockchain-based applications conduct two primary operations, i.e., writing data on blockchain networks and reading these data from the networks. These tasks require users to have considerable knowledge in blockchain technology, and they become even more challenging if users want to utilize different blockchain platforms to write and read data. So far, we have not had a uniform mechanism to perform write and read operations on various blockchain platforms. In addition, writing a huge amount of data on blockchain networks is a time-consuming task and requires considerable transaction fees. To address these issues, we present in the paper a data mapping language named BML. BML allows developers to uniformly define mappings for data transformation from traditional data storage mechanisms into blockchain networks. Conversely, this language also assists users in reading transformed data. Currently, BML accepts five input data sources, including XML, JSON, XLSX, SQL (relational database), NoSQL, and supports two output platforms, including Hyperledger Sawtooth and Ethereum.
Dec 1, 2020·2020 IEEE Intl Conf on Parallel & Distributed Processing with Applications, Big Data & Cloud Computing, Sustainable Computing & Communications, Social Computing & Networking (ISPA/BDCloud/SocialCom/SustainCom)
Confronted with the explosive growth of data in various cyber systems, decentralized storage has gained popularity thanks to its ubiquitousness, since the devices can share their idle storage space for higher scalability. However, current decentralized storage networks suffer the failure risk due to the insufficient trust among nodes, in addition to the lack of a reliable resource allocation mechanism. In this paper, we present a novel trusted shared storage network, namely TSSN, to achieve efficacious decentralized storage with trust. Designed under a shared storage framework, TSSN introduces blockchain via an on/off-chain collaborative protocol, which realizes the decentralized trust with promising efficiency. In the primary novelty of TSSN, we design an allocation mechanism based on trading and multi-attribute bilateral matching to maintain the stability and fluidity of resources. To verify the practical effectiveness of our solution, we implement a TSSN prototype on our testbed based on IPFS and Ethereum. The experimental results demonstrate the performance of TSSN within on-chain storage overhead, throughput, and latency.
Junzhi Yan, Xiaoyong Hang, Bo Yang, Li Su · 5 authors
Some issues such as CRL/OCSP (Certificate Revocation List / Online Certificate Status Protocol) unavailable, previsioned trust anchor unavailable, high communication load arise when PKI (Public Key Infrastructure) is leveraged into mobile networks. A blockchain based PKI framework in mobile network is proposed to solve these issues. The system is constituted by submission nodes, validator nodes, inquiry nodes. Scenarios and application cases are provided, and it shows the system can be widely used in mobile networks. The blockchain based PKI system is analyzed and compared to traditional solutions. It shows the trustworthy of SSL (Security Socket Layer) certificates and device certificates are the same as those in traditional PKI system. The storage requirement and certificate capacity of blockchain based PKI system is analyzed. Since certificates have expiry dates, the optimization method based on the invalid certificates is proposed. The optimization improves the storage efficiency of the blockchain based PKI certificate management system.
Saeideh G. Motlagh, Jelena Mišić, Vojislav B. Mišić
Compact block protocol aims to reduce bandwidth usage and, possibly, latency in the Bitcoin network. In this work, we present an analytical model to evaluate the impact of churning nodes on the Bitcoin network when the compact block protocol is used. We use a Continuous Time Markov Chain to model wake-up and sleeping behavior of each node in the network. We also calculate synchronization time, including transaction deficit recovery, when a node rejoins the network. When a node is absent from the network, it misses blocks mined during its absence but also some of the transactions which may be omitted from the subsequent compact blocks. Our results indicate that synchronization time takes more than a minute when node is away from the network for several hours. Moreover, the majority of synchronization time is spent on block verification and transaction deficit recovery.
Xuan Luo, Zehua Wang, Wei Cai, Xiuhua Li · 5 authors
Traditional centralized token exchange (CEX) has been suffering from hacking due to the centralized management of users’ tokens. In contrast, decentralized token exchange (DEX) maintains users’ assets by smart contracts in a decentralized manner, but introduces additional overhead in terms of gas fee and transaction confirmation latency. Hybrid decentralized token exchange (HEX) has been proposed to combine the benefits of CEX and DEX. However, existing HEX is criticized for two issues. First, trading transactions are time-consuming and expensive for frequent token traders. Second, excessive simultaneous transactions might cause the pending transaction congestion in the Ethereum network. In this paper, we propose a payment channel based HEX, which extends existing solutions by adding a new payment channel layer to benefit frequent traders and alleviate the pending transaction congestion. Besides, we propose the very first gas-price vs. transaction-confirmation-latency function to guide Ethereum transaction issuers to choose an optimal gas price that minimizes the overall cost. Extensive simulations are conducted to compare the cost in the proposed HEX with that in the conventional HEX. The results demonstrate the effectiveness of our proposed mechanism in terms of reducing gas fees and transaction confirmation latency for frequent traders as well as the pending transaction congestion in Ethereum.
Florian Adamsky, Daniel Kaiser, Michael Steglich, Thomas Engel
Distributed Hash Table (DHT) protocols, such as Kademlia, provide a decentralized key-value lookup which is nowadays integrated into a wide variety of applications, such as Ethereum, InterPlanetary File System (IPFS), and BitTorrent. However, many security issues in DHT protocols have not been solved yet. DHT networks are typically evaluated using mathematical models or simulations, often abstracting away from artefacts that can be relevant for security and/or performance. Experiments capturing these artefacts are typically run with too few nodes.