Niclas Kannengießer, Sebastian Lins, Tobias Dehling, Ali Sunyaev
When developing peer-to-peer applications on Distributed Ledger Technology (DLT), a crucial decision is the selection of a suitable DLT design (e.g., Ethereum) because it is hard to change the underlying DLT design post hoc. To facilitate the selection of suitable DLT designs, we review DLT characteristics and identify trade-offs between them. Furthermore, we assess how DLT designs account for these trade-offs and we develop archetypes for DLT designs that cater to specific quality requirements. The main purpose of our article is to introduce scientific and practical audiences to the intricacies of DLT designs and to support development of viable applications on DLT.
Francesco Zola, Cristina Pérez‐Solà, Jon Egana, Maria Eguimendia · 5 authors
Bitcoin is a peer-to-peer distributed cryptocurrency system, that keeps all transaction history in a public ledger known as blockchain. The Bitcoin network is implicitly pseudoanonymous and its nodes are controlled by independent entities making network analysis difficult. This calls for the development of a fully controlled testing environment. This paper presents Kriptosare.gen, a dockerized automatized Bitcoin testbed, for deploying full-scale custom Bitcoin networks. The testbed is deployed in a single machine executing four different experiments, each one with different network configuration. We perform a cost analysis to investigate how the resources are related with network parameters and provide experimental data quantifying the amount of computational resources needed to run the different types of simulations. Obtained results demonstrate that it is possible to run the testbed with a configuration similar to a real Bitcoin system.
Maximilian Tschuchnig, Dejan Radovanovic, Eduard Hirsch, Oberluggauer Anna-Maria · 5 authors
Conventional data storage methods like SQL and NoSQL offer a huge amount of possibilities with one major disadvantage, having to use a centralized authority. This authority may be in the form of a centralized or decentralized master server or a permissioned peer-to-peer setting. This paper looks at different technologies on how to persist data without using a central authority, mainly looking at permissionless peer-to-peer networks, primarily Distributed Ledger Technologies (DLTs) and a combination of DLTs with conventional databases. Afterwards it is shown how a system like this might be implemented in two prototypes which are then evaluated against conventional databases.
Bitcoin, introduced in 2008 and launched in 2009, is the first digital currency to solve the double spending problem without relying on a trusted third party. Bitcoin provides a way to transact without any trusted intermediary, but its privacy guarantees are questionable. Despite the fact that Bitcoin addresses are not linked to any identity, multiple deanonymization attacks have been proposed. Alternative cryptocurrencies such as Dash, Monero, and Zcash aim to provide stronger privacy by using sophisticated cryptographic techniques to obfuscate transaction data. Previous work in cryptocurrency privacy mostly focused on applying data mining algorithms to the transaction graph extracted from the blockchain. We focus on a less well researched vector for privacy attacks: network analysis. We argue that timings of transaction messages leak information about their origin, which can be exploited by a well connected adversarial node. For the first time, network level attacks on Bitcoin and the three major privacy-focused cryptocurrencies have been examined. We describe the message propagation mechanics and privacy guarantees in Bitcoin, Dash, Monero, and Zcash. We propose a novel technique for linking transactions based on transaction propagation analysis. We also unpack address advertisement messages (ADDR), which under certain assumptions may help in linking transaction clusters to IP addresses of nodes. We implement and evaluate our method, deanonymizing our own transactions in Bitcoin and Zcash with a high level of accuracy. We also show that our technique is applicable to Dash and Monero. We estimate the cost of a full-scale attack on the Bitcoin mainnet at hundreds of US dollars, feasible even for a low budget adversary.
Sebastian Henningsen, Daniel Teunis, Martin Florian, Björn Scheuermann
Ethereum is a decentralized Blockchain system that supports the execution of Turing-complete smart contracts. Although the security of the Ethereum ecosystem has been studied in the past, the network layer has been mostly neglected. We show that Go Ethereum (Geth), the most widely used Ethereum implementation, is vulnerable to eclipse attacks, effectively circumventing recently introduced (Geth v1.8.0) security enhancements. We responsibly disclosed the vulnerability to core Ethereum developers; the corresponding countermeasures to our attack where incorporated into the v1.9.0 release of Geth. Our false friends attack exploits the Kademlia-inspired peer discovery logic used by Geth and enables a low-resource eclipsing of long-running, remote victim nodes. An adversary only needs two hosts in distinct /24 subnets to launch the eclipse, which can then be leveraged to filter the victim's view of the Blockchain. We discuss fundamental properties of Geth's node discovery logic that enable the false friends attack, as well as proposed and implemented countermeasures.
Open access
3 source records
Peer-to-Peer Network Technologies
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
Bitcoin is a top-ranked cryptocurrency that has experienced huge growth and survived numerous attacks. The protocols making up Bitcoin must therefore accommodate the growth of the network and ensure security. Security of the Bitcoin network depends on connectivity between the nodes. Higher connectivity yields better security. In this paper we make two observations: (1) current connectivity in the Bitcoin network is too low for optimal security; (2) at the same time, increasing connectivity will substantially increase the bandwidth used by the transaction dissemination protocol, making it prohibitively expensive to operate a Bitcoin node. Half of the total bandwidth needed to operate a Bitcoin node is currently used to just announce transactions. Unlike block relay, transaction dissemination has received little attention in prior work. We propose a new transaction dissemination protocol, Erlay, that not only reduces the bandwidth consumption by 40% assuming current connectivity, but also keeps the bandwidth use almost constant as the connectivity increases. In contrast, the existing protocol increases the bandwidth consumption linearly with the number of connections. By allowing more connections at a small cost, Erlay improves the security of the Bitcoin network. And, as we demonstrate, Erlay also hardens the network against attacks that attempt to learn the origin node of a transaction. Erlay is currently being investigated by the Bitcoin community for future use with the Bitcoin protocol.
Paweł Szałachowski, Daniël Reijsbergen, Ivan Homoliak, Siwei Sun
Bitcoin is the most successful cryptocurrency so far. This is mainly due to its novel consensus algorithm, which is based on proof-of-work combined with a cryptographically-protected data structure and a rewarding scheme that incentivizes nodes to participate. However, despite its unprecedented success Bitcoin suffers from many inefficiencies. For instance, Bitcoin's consensus mechanism has been proved to be incentive-incompatible, its high reward variance causes centralization, and its hardcoded deflation raises questions about its long-term sustainability. In this work, we revise the Bitcoin consensus mechanism by proposing StrongChain, a scheme that introduces transparency and incentivizes participants to collaborate rather than to compete. The core design of our protocol is to reflect and utilize the computing power aggregated on the blockchain which is invisible and "wasted" in Bitcoin today. Introducing relatively easy, although important changes to Bitcoin's design enables us to improve many crucial aspects of Bitcoin-like cryptocurrencies making it more secure, efficient, and profitable for participants. We thoroughly analyze our approach and we present an implementation of StrongChain. The obtained results confirm its efficiency, security, and deployability.
Fuelled by the success (and hype) around cryptocurrencies, distributed ledger technologies (DLT), particularly blockchains, have gained a lot of attention from a wide spectrum of audience who perceive blockchains as a key to carry out business processes that have hitherto been cumbersome in a cost and time effective manner. Governments across the globe have responded to this promising but nascent technology differently - from being apathetic or adopting a wait-and-watch approach: letting the systems shape themselves, to creating regulatory sandboxes and sponsoring capacity building, or in some instances (arguably) over-regulating and attempting to put the blockchain genie back in the bottle. Possible government role spans across a spectrum: regulating crypto-currencies and initial coin offerings (ICO), formulating regulatory frameworks for managing the adoption of blockchains, particularly in critical infrastructure industries, facilitating capacity building, and finally, embracing blockchain technology in conducting the activities of the government itself - be it internally, or in using them to deliver public services. In this paper we survey the last, namely, the use of blockchain and associated distributed ledger technologies in the government technology (GovTech) stack, and discuss the merits and concerns associated with the existing initiatives and approaches.
Ethereum is an open-source, public, blockchain-based distributed computing platform and operating system featuring smart contract functionality. In this paper, we proposed an Ethereum based eletronic voting (e-voting) protocol, Ques-Chain, which can ensure the authentication can be done without hurting confidentiality and the anonymity can be protected without problems of scams at the same time. Furthermore, the authors considered the wider usages Ques-Chain can be applied on, pointing out that it is able to process all kinds of messages and can be used in all fields with similar needs.
People need a motive to use and maintain a system. In many of the systems we use today, financial rewards and punishments provide a key incentive to participate and abide by the rules. From salaries to traffic tickets, financial motives are often closely tied to a system's viability. Distributed systems such as blockchain also need a mechanism to motivate good behavior. A blockchain must encourage users to maintain the system while preventing a minority of these users from colluding and gaining disproportionate control. Many popular public blockchains use monetary incentives to encourage users to participate and behave appropriately. But these same incentive schemes create more problems than they solve. Mining rewards cause centralization in proof of work chains such as Bitcoin. Validator rewards and punishments invite attacks in proof of stake chains. This paper argues why these incentive schemes are detrimental to blockchain. It also considers a range of other systems-some of which incorporate monetary incentives, some of which do not-to confirm that monetary incentives may be neither necessary nor sufficient for good user behavior.
Emilija Stojmenova Duh, Andrej Duh, Uroš Droftina, Tim Kos · 7 authors
Scholarly communication is today immersed in publish-or-perish culture that propels non-cooperative behavior in the sense of strategic games played by researchers. Here we introduce and describe a blockchain based platform for decentralized scholarly communication. The design of the platform rests on community driven publishing reviewing processes and implements cryptoeconomic incentives that promote cooperative user behavior. The key to achieve cooperation in blockchain based scholarly communication is to transform today’s static research paper into a modifiable research paper under continuous peer review process. We introduce and discuss the implementation of a modifiable research paper as a smart contract on the blockchain.
Léo Besançon, Catarina Ferreira da Silva, Parisa Ghodous
Current solutions for designing and building decentralized blockchain applications lack interoperability. Consequently, blockchains and existing technologies do not integrate well in a unified framework. This integration is necessary to work around some of the blockchains constraints, such as scalability of transactions and ergonomics. Indeed, blockchains are not suitable for huge data storage, but there are distributed data storage solutions that can be used in a decentralized blockchain application. Regarding ergonomics, the use of blockchain technology should be in the background and transparent for users that may not know how to set up and secure a blockchain-based application.We propose an architecture aiming to easily link existing decentralized technologies and blockchains. We then discuss the impact of this architecture for the video game industry. As a result, we propose an original data representation of blockchain gaming assets in order to improve data exchanges in this industry.
Open access
Blockchain Technology Applications and Security
Peer-to-Peer Network Technologies
Advanced Steganography and Watermarking Techniques
Tarun Chitra, Monica Quaintance, Stuart Haber, Will Martino
While many distributed consensus protocols provide robust liveness and consistency guarantees under the presence of malicious actors, quantitative estimates of how economic incentives affect security are few and far between. In this paper, we describe a system for simulating how adversarial agents, both economically rational and Byzantine, interact with a blockchain protocol. This system provides statistical estimates for the economic difficulty of an attack and how the presence of certain actors influences protocol-level statistics, such as the expected time to regain liveness. This simulation system is influenced by the design of algorithmic trading and reinforcement learning systems that use explicit modeling of an agent's reward mechanism to evaluate and optimize a fully autonomous agent. We implement and apply this simulation framework to Kadena's Chainweb, a parallelized Proof-of-Work system, that contains complexity in how miner incentive compliance affects security and censorship resistance. We provide the first formal description of Chainweb that is in the literature and use this formal description to motivate our simulation design. Our simulation results include a phase transition in block height growth rate as a function of shard connectivity and empirical evidence that censorship in Chainweb is too costly for rational miners to engage in. We conclude with an outlook on how simulation can guide and optimize protocol development in a variety of contexts, including Proof-of-Stake parameter optimization and peer-to-peer networking design.
Cryptocurrencies came to the world in the recent decade and attempted to offer a new order where the financial system is not governed by a centralized entity, and where you have complete control over your account without the need to trust strangers (governments and banks above all). However, cryptocurrency systems face many challenges that prevent them from being used as an everyday coin. In this paper we attempt to take one step forward by introducing a cryptocurrency system that has many important properties. Perhaps the most revolutionary property is its deterministic operation over a fully asynchronous communication network, which has sometimes been mistakenly considered to be impossible. By avoiding any temporal assumptions, we get a system that is robust against arbitrary delays in the network, and whose latency is only a function of the actual communication delay. The presented system is based on familiar concepts $-$ banking and democracy. Our banks, just like normal banks, keep their clients' money and perform their clients' requests. However, because of the cryptographic scheme, your bank cannot do anything in your account without your permission and its entire operation is transparent so you don't have to trust it blindly. The democracy means that every operation performed by the banks (e.g., committing a client transaction) has to be accepted by a majority of the coin holders, in a way that resembles representative democracy where the banks are the representatives and where each client implicitly delegates his voting power (the sum of money in his account) to his bank. A client can switch banks at any moment, by simply applying a corresponding request to the new bank of his choice.
The main goal of this article is to present a direct approach for the formula giving the long-term apparent hashrates of Selfish Mining strategies using only elementary probabilities and combinatorics, more precisely, Dyck words. We can avoid computing stationary probabilities on Markov chain, nor stopping times for Poisson processes as in previous analysis. We do apply these techniques to other block withholding strategies in Bitcoin, and then, we consider also selfish mining in Ethereum.
The EPCglobal Network is a computer network used to share product data between trading partners. The EPC Information Services (EPCIS) is an event record repository that allows disparate applications to access and query for data both within and across enterprises. Ultimately, this data sharing is aimed at enabling participants in the EPCglobal Network to gain a shared view of the disposition of EPC-bearing objects within a relevant business context [1].Despite the potential benefits, enterprises are reluctant to integrate into the EPCglobal Network due to the financial and manpower resources required to set up, operate and maintain the EPCIS and to adopt the standards. Issues like security, computation and storage overheads would also have to be managed. To solve the problem, this paper advocates a blockchain solution using Hyperledger Fabric to serve as a shared EPCIS across trading partners. The blockchain can be queried directly to facilitate information sharing subjected to access control rules. It also adheres to the EPCglobal Network standards. This approach provides several important benefits including eliminating the need for enterprises to maintain their own EPCIS while still being able to participate and benefit from the network. As the blockchain can be queried directly, the provision of EPC Discovery Services (EPCDS) may also be unnecessary. To explore this idea, we constructed a prototype using Hyperledger Composer and Hyperledger Fabric while adhering to the data elements, structures and formats as stated in the standards to ensure interoperability with existing architecture both upstream and downstream.
Martijn de Vos, Mitchell Olsthoorn, Johan Pouwelse
Decentralized applications, also known as dApps, are the new paradigm for writing business-critical software. Recruiting developers with appropriate qualifications and skills for this activity is key, yet challenging. The main problem is that the portfolio of developers is usually scattered across centralized platforms like GitHub and LinkedIn, and vendor locked. This can result in an incomplete impression of their capabilities. We address this problem and introduce DevID, a blockchain-based portfolio for developers. Over time, this portfolio enables developers to build up a trustworthy collection of records that showcase their capabilities and expertise. They can import data assets from third parties into a unified DevID portfolio, add projects and skills, and receive endorsements. All portfolio records are stored on a scalable distributed ledger and owned by developers themselves. The essential idea is to exploit the tamper-proof property of the blockchain while providing durable storage. To demonstrate the practical value of DevID, we build the competition-based platform, dAppCoder, for the development of decentralized applications. On dAppCoder clients are able to submit their ideas and developers can find work. dAppCoder utilizes DevID portfolios to match these clients and developers. We fully implement our ideas and conduct a deployment trial. Our trial demonstrates that DevID is efficient at storing portfolio records.
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 have downsides in communication and storage efficiency, convergence to centralization, and consistency problems. In this paper, 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 the 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 blockchain. 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. LightChain provides a deterministic fork-resolving strategy as well as a blacklisting mechanism, and it is secure against colluding adversarial peers attacking the availability and integrity of the system. We provide mathematical analysis and experimental results on scenarios involving 10K nodes to demonstrate the security and fairness of LightChain. As we experimentally show in this paper, compared to the mainstream blockchains like Bitcoin and Ethereum, LightChain requires around 66 times less per node storage, and is around 380 times faster on bootstrapping a new node to the system, while each LightChain node is rewarded equally likely for participating in the protocol.
In a blockchain system, consensus protocol as an incentive and security mechanism, is to ensure the participants to build the block honestly and effectively. There are different consensus protocols for blockchain, like Proof of work (PoW), Proof of Stake (PoS), Proof of Space (PoSpace), Proof of Activities etc. But most of these consensus protocols are not designed for doing some useful jobs for society because of too much competition and scalability limitation. Massive electric power and computing resources, including CPU, RAM, storage and sensors have been wasted to run blockchain network based on these consensus protocols. Current frameworks and middleware for building decentralised applications (dApps) are largely limited to simple and less useful jobs. In this paper, we present Proofware which is designed for developers to build their dApps easily with existing public/crowd-based computing resources. Under Proofware, developers can develop and test their own Proof of Useful Work (PoUW) consensus protocols. Also, rather than depending on a centralised accounting system, each dApp has an embedded currency system to keep the whole incentive system decentralised, fair, transparent, stable and sustainable. Based on Proofware, we have built a crowd based video sharing application, called OurTube, as a case study. By the OurTube example, it has shown Proofware significantly improves the productivity to build crowd-based computing system with the features of cost-effectiveness, anti-censorship, elasticity and financial sustainability.
Andrew Cullen, Pietro Ferraro, Christopher King, Robert Shorten
Recently, Directed Acyclic Graph (DAG) based Distributed Ledgers have been proposed for various applications in the smart mobility domain [1]. While many application studies have been described in the literature, an open problem in the DLT community concerns the lack of mathematical models describing their behaviour, and their validation. Building on a previous work in [1], we present, in this paper, a fluid based approximation for the IOTA Foundation's DAG-based DLT that incorporates varying transaction delays. This extension, namely the inclusion of varying delays, is important for feedback control applications (such as transactive control [2]). Extensive simulations are presented to illustrate the efficacy of our approach.
Summary Proof of stake (PoS) protocols rely on voting mechanisms to reach consensus on the current state. If an enhanced majority of staking nodes, also called validators , agree on a proposed block, then this block is appended to the blockchain. Yet these protocols remain vulnerable to faults caused by validators who abstain either accidentally or maliciously. To protect against such faults while retaining the PoS selection and reward allocation schemes, we study weighted voting in validator committees. We formalize the block creation process and introduce validators' voting profiles which we update by a multiplicative weights algorithm relative to validators' voting behavior and aggregate blockchain rewards. Using this framework, we leverage weighted majority voting rules that optimize collective decision making to show, both numerically and analytically, that the consensus mechanism is more robust if validators' votes are appropriately scaled. We raise potential issues and limitations of weighted voting in trustless, decentralized networks and relate our results to the design of current PoS protocols.
In this paper, we design and implement the first-ever decentralized replicated relational database with blockchain properties that we term blockchain relational database. We highlight several similarities between features provided by blockchain platforms and a replicated relational database, although they are conceptually different, primarily in their trust model. Motivated by this, we leverage the rich features, decades of research and optimization, and available tooling in relational databases to build a blockchain relational database. We consider a permissioned blockchain model of known, but mutually distrustful organizations each operating their own database instance that are replicas of one another. The replicas execute transactions independently and engage in decentralized consensus to determine the commit order for transactions. We design two approaches, the first where the commit order for transactions is agreed upon prior to executing them, and the second where transactions are executed without prior knowledge of the commit order while the ordering happens in parallel. We leverage serializable snapshot isolation (SSI) to guarantee that the replicas across nodes remain consistent and respect the ordering determined by consensus, and devise a new variant of SSI based on block height for the latter approach. We implement our system on PostgreSQL and present detailed performance experiments analyzing both approaches.
Sandi Rahmadika, Diena Rauda Ramdania, Maisevli Harika
Blockchain technology holds great promise to rewire the current financial system which relies on the third party. Every transaction is recorded in a secure and transparent for the parties in the blockchain network. Blockchain technology in the energy sector becomes an interesting topic among researchers at this moment. The use of blockchain allows producers and consumers to trade energy transactions through smart grids because of a decentralized energy trading system. The trading activities without a third party involved would reduce the cost of a transaction thus it brings to a new level of quality of service in the trading system. In this paper, we propose an architectural model for decentralized energy trading system among the neighbors that allows the producer who has the surplus energy to conduct a trading activity with his/her neighbors. The transactions manage by the miners in the same blockchain network. Moreover, we analyze the security issues from various attacks and presenting the performance of the selected attack that might occur in the model.
Fazeel Ahmed Khan, Adamu Abubakar Ibrahim, Marwan Mahmoud, Mahmoud Ahmad Al‐Khasawneh · 5 authors
The emergence of Blockchain have revolutionize the decentralization in distributed architecture. The advances in the consensus mechanism techniques and the development of different variants of consensus algorithms gives a huge impact on its progress. These technologies allow to have a distributed peer-to-peer network in which each external entity can be able to interact with other entities without any trusted intermediary in a verifiable manner. The existing consensus algorithms are mostly concerned with public blockchain having focused on public ledgers in general. The consortium blockchain is least focused as compared with other variants of blockchain (public and private) showing the need to address this vacuum. In this paper, we proposed a consensus algorithm named Rift for consortium blockchain which works on the principle of trust mechanism for achieving consensus in a blockchain. The consensus is achieved by distributed nodes in a consortium blockchain which were controlled by consortium members to decentralize the arbitration by voting and trust metrics. In this paper, we elaborate the comprehensive idea of Rift and discuss the working model for this algorithm. We also perform simulation on the proposed algorithm and determine the performance variables to evaluate the effectiveness of Rift. The evaluated results show the improvement in the performance which is the objective requirement for the evaluation.