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.
This paper introduces FileTribe, a secure decentralized application for sharing files in closed groups. It employs IPFS, a distributed file system, as its data storage layer, avoiding the pitfalls of centralized storage solutions. Changes to files and group membership are recorded separately on a blockchain, making them irrefutable. A Decentralized Application (Dapp) on top of Ethereum is responsible for user authentication and reaching consensus among group members regarding the state of the group and shared files. File access control is supervised by the members themselves. These features combine to make FileTribe unique in its ability to serve a wide range of safetycritical scenarios, including ones where cloud-based or pure peerto- peer solutions fall short.
As blockchain-based decentralized applications (DApp) become increasingly popular recently, there is an urgent demand for effective testing schemes and tools. Due to the complexity introduced by application-blockchain interaction, existing testing methods become non-applicable. In this paper, we present a guided and automated framework called Sungari to test DApps. The insights behind Sungari are two-fold. First, we employ random events to infer an abstract relation between frontend and blockchain. Second, we use the relation to generate event sequnces in a guided manner that can cover blockchain smart contracts as quick as possible. In a real-world DApp case study, Sungari outperformed random approach by covering 33% more application use cases.
In massive, dynamic and distributed P2P networks like Bitcoin, where thousands of updates occur per second, it is hard to obtain an accurate topology representing the structure of the network as a graph with nodes and links by using the traditional local measurement approaches based on batches, offline data, or on the discovery of the topology around a small set of nodes and then combine them to discover an approximate network topology. All of which present some limitation when applying them on blockchain-based networks. In this paper, we propose a topology discovery system, which performs a real-time data collection and analysis for Bitcoin P2P links with the use of a customized version of the Page-Rank algorithm that assembles incoming nodes information for deeper graph analysis processing. The topology discovery system allows us to gain knowledge on the Bitcoin network size, the network stability in term of well-connected Bitcoin nodes, as well as some data regarding the Bitcoin nodes geolocation.
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
Blockchain techniques are attracting growing interest due to their capability of immutable and anonymous recording without any centralized authority. One of the difficulties blockchain researchers are facing is a lack of ways to verify behaviors of large scale blockchain networks. In this demonstration, we present SimBlock, a blockchain network simulator. It simulates the peer-to-peer network of a public blockchain, e.g., Bitcoin, which consists of thousands of nodes, as well as parameters related to a blockchain and its network are flexibly configurable. SimBlock can also visualize nodes' behavior and block propagation. By giving some example studies, such as exploring better neighbor selection strategies and assessing the influence of relay networks, we show that SimBlock can facilitate blockchain network research.
Luigi Vigneri, Wolfgang Welz, Alon Gal, Vassil S. Dimitrov
Throughput is a key property for any distributed ledger technology. However, limited resources, such as bandwidth or node computational power, can lead to network congestion when nodes try to issue more transactions than the network can handle. Consequently, priority criteria are necessary to determine whether a transaction should be accepted or not. In this paper, we present a novel adaptive rate control algorithm for the Tangle, a new-generation distributed ledger allowing large throughput. Our approach combines various concepts, such as resource tests and Proof-of-Work with dynamic difficulty. Our algorithm not only serves as an anti-spam mechanism, but also achieves fair representation. This is to be contrasted with pure Proof-of-Work blockchains, which lead to wasteful mining races.
Internet of Things (IoT), Supply Chain monitoring, and other distributed applications rely on messaging protocols for data exchange. Contemporary IoT and enterprise deployments widely use the publish-subscribe messaging model because of its resource-efficiency. However, the systems with publish-subscribe messaging model employ a centralized architecture, wherein the data from all the publishers in the application network flows via a central broker to the subscribers. Such a centralized architecture makes the publish-subscribe messaging model susceptible to Byzantine failures. For example, it provides an opportunity for the organization that owns the broker to tamper with the data. In this work, we contribute Trinity, a novel distributed publish-subscribe broker with Byzantine fault-tolerance and blockchain-based immutability. Trinity distributes the data published to one of the brokers in the network to all the brokers in the network, and stores the data in an immutable ledger through the use of blockchain technology. Through the use of consensus protocols and distributed ledger technology, Trinity can guarantee ordering, fault-tolerance, persistence and immutability across trust boundaries.Our evaluation results show that Trinity consumes minimal resources. To the best of our knowledge, Trinity is the first framework that combines the components of the blockchain technology with the publish-subscribe messaging model. Furthermore, we plan to use Trinity in a real-world use case for increasing the transparency of racial profiling.
Although cryptocurrencies have attracted a large amount of users and investors and there has been various researches in the area of distributed ledger technology (DLT), there is little work on cryptocurrency studies. Given the rapidly increasing number and diversity of cryptocurrencies, we present a landscape with a selective set of representative cryptocurrencies to holistically portray their characteristics and provide practitioners an analysis from both business and technical perspectives. The focused observations elaborate how the typical cryptocurrency are designed and operated in industry. This study offers a breakthrough understanding of the cryptocurrencies through the generated landscape which report the state of cryptocurrencies, and can be used as a framework for cryptocurrency analysis.
Xuan Luo, Wei Cai, Zehua Wang, Xiuhua Li · 5 authors
Traditional centralized token exchange (CEX) is criticized for its security and privacy issues, since crypto currency users are required to surrender their private keys to the exchange. In contrast, decentralized token exchange (DEX) solves this issue by introducing additional trading gas fee and latency to the system. Hybrid decentralized token exchange (HEX) has been proposed to combine the advantages of CEX and DEX. However, existing HEX is still suffering from two issues. The first issue is that it is unfriendly for a trader who needs to exchange tokens frequently within a certain period of time, due to the fact that it is time-consuming and expensive. The second issue is the potential network congestion in Ethereum caused by excessive simultaneous transactions from the exchange. 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 network congestion.
Muhammad Anas Imtiaz, David Starobinski, Ari Trachtenberg, Nabeel Younis
Efficient and reliable propagation of blocks is vital for ensuring the scalability of the Bitcoin network. As a result, several schemes have been proposed over the last few years to speed up the block propagation, most notably the compact block protocol (BIP 152). Despite this, we show experimental evidence that (i) the vast majority (97%) of Bitcoin nodes exhibit intermittent network connectivity (churn), and (ii) this churn results in significant numbers of unsuccessful compact blocks, roughly twice the figure for continuously connected nodes. Specifically, we conduct experiments on the Bitcoin network that show that churn results in a 135% average increase in block propagation time (i.e., 336.57 ms vs 142.62 ms), and can lead to as high as an 800-fold increase in the worst case. To effect our analysis, we develop a statistical model for churn based on empirical network data, and use this model to actuate the live test nodes on the Bitcoin network. The performance of the system is measured by means of a novel framework that we develop for logging the internal behavior of a Bitcoin node and share for public use.
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.
Distributed ledgers have received significant attention as a building block for cryptocurrencies and have proven to be also relevant in several other fields. In cryptocurrencies, this abstraction is usually implemented by grouping transactions in blocks that are then linked together to form a blockchain. Nodes need to exchange information to maintain the status of the chain but this process consumes significant network resources. Unfortunately, naively reducing the number of messages exchanged can have a negative impact in performance and correctness, as some transactions might not be included in the chain.
We propose TickEth, a system that aims at mitigating some of the problems encountered by the ticketing industry. The name TickEth is built by combining the words ticket, its application domain, and Ethereum, the underlying platform we adopted for the development of the prototype.
Annotation: This Master's thesis provides a comprehensive analysis of various consensus mechanisms essential for distributed ledger technologies like blockchain, sidechain, DAG, and more. A total of 22 consensus mechanisms, including traditional and alternative proof-based algorithms, fault tolerance algorithms, and DAG-based algorithms, were evaluated using eight criteria such as security, decentralization, scalability, and energy efficiency. The study includes an extensive set of testing scenarios for these mechanisms, and recommendations are given based on the analysis of individual mechanisms, emphasizing the importance of choosing mechanisms suited to specific system requirements. The research contributes significantly to the field by providing a detailed understanding of consensus mechanisms, a comparative analysis highlighting their strengths and weaknesses, and valuable test scenarios for future studies.
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.
As of today, web-based social communication platforms, such as WhatsApp, Twitter, or Facebook, are almost exclusively realized via centralized platforms, based on proprietary interfaces, protocols, and data formats. In consequence, even though social communication being a decentralized, peer-to-peer phenomenon, web-based communication today is implemented via closed, proprietary data silos, which not only lock-in users into their service platforms, but also control and own exchange information and data, including personal and sensitive data such as photos, messages, or contact information. In this paper we present Tawki, a decentralized service architecture for social communication. Using Tawki, users remain in full control of their personal data, which is stored and managed by personal data storages. Each data storage is accessible via a unified Tawki API, which allows users to send and request data to and from other users' personal data storages. Following this approach, social communication is again peer-to-peer without involving a third party controlling and monitoring the process. Tawki uses the Ethereum Name Service (ENS) for both the management of user identities and resolving identifiers to the respective user's personal storage location. Leveraging the immutability of the Ethereum Blockchain, identity management and discovery of personal data storages is secured against censorship and control through any third party.
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.
Blockchains are currently gaining attention as a newly emerging technology in both academia and industry, capable of impacting a variety of domains beyond cryptocurrencies. Performance modeling can be used to provide us with a deeper understanding of the behavior and dynamics within blockchain peer-to-peer networks. Blockchain system architects can leverage network models to properly tune their system and to reduce design costs significantly. In this paper, we focus on the original and well-established Bitcoin blockchain network. In particular, we propose a random graph model for performance modeling and analysis of the inventory-based protocol for block dissemination. This model addresses the impact of key blockchain parameters on the overall performance of Bitcoin. We derive some explicit and closed-form equations for block propagation delay and traffic overhead. We implement our model using the popular network simulator OMNet++. We validate the accuracy of our theoretical model and its implementation with our dataset mined from the Bitcoin network. Our results show the trade-off between the default number of connections per node, network bandwidth, and block size in order to compute the optimal block propagation delay over the network.
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.