In the first part of this work, we present, model and analyze a randomized automated peering model, that can be implemented to any distributed system. We conclude that the scheme has some desirable properties (specifically, a reasonable message overhead, a reasonable distribution of the numbers of peers of a node, and a negligible probability of an attack by a malicious actor to be successful). In the second part, we present an article published in the volume 136 of the journal Computers & Industrial Engineering, in October of 2019 (DOI 10.1016=j.cie.2019.07.025). In the paper, we analyze the Nash Equilibria of a graph attachment game, defined to represent the different strategies that malicious actors can use to take certain advantages in a DAG-based (i.e., based on Directed Acyclic Graphs) distributed ledger system. We prove the existence of almost symmetric Nash equilibria for the system where a part of players tries to optimize their attachment strategies and another part follows a default one. We also present simulations that show that the selfish players will not choose strategies that are considerably different that the recommended one.
Dimitris Vyzovitis, Yusef Napora, Dirk McCormick, David Dias · 5 authors
Permissionless blockchain environments necessitate the use of a fast and\nattack-resilient message propagation protocol for Block and Transaction\nmessages to keep nodes synchronised and avoid forks. We present GossipSub, a\ngossip-based pubsub protocol, which, in contrast to past pubsub protocols,\nincorporates resilience against a wide spectrum of attacks.\n Firstly, GossipSub's mesh construction implements an eager push model keeps\nthe fan-out of the pubsub delivery low and balances excessive bandwidth\nconsumption and fast message propagation throughout the mesh. Secondly, through\ngossip dissemination, GossipSub realises a lazy-pull model to reach nodes\nfar-away or outside the mesh. Thirdly, through constant observation, nodes\nmaintain a score profile for the peers they are connected to, allowing them to\nchoose the most well-behaved nodes to include in the mesh. Finally, and most\nimportantly, a number of tailor-made mitigation strategies designed\nspecifically for these three components make GossipSub resilient against the\nmost challenging Sybil-based attacks. We test GossipSub in a testbed\nenvironment involving more than 5000 VM nodes deployed on AWS and show that it\nstays immune to all considered attacks. GossipSub is currently being integrated\nas the main messaging layer protocol in the Filecoin and the Ethereum 2.0\n(ETH2.0) blockchains.\n
This project aims to create a blockchain-based model that addresses key challenges in digital voting. The goal is to develop a secure and transparent system that eliminates common issues such as delays in result announcements, voter identity verification concerns, and security risks [1]. Voting is the backbone of any democracy, and ensuring its integrity is crucial. Traditional digital voting systems often face problems like fraud, manipulation, and lack of transparency. Blockchain technology, with its decentralized and tamper-proof nature, offers a promising solution. It functions as a distributed ledger that records transactions securely in a peer-to-peer network, making it nearly impossible to alter past data [2]. This technology brings several benefits to voting, including decentralization, security, transparency, immutability, and voter anonymity [3]. A major highlight of this project is the integration of blockchain with smart contracts, which adds an extra layer of security and automation to the voting process [4]. The system is designed to work on the Ethereum blockchain, using smart contracts written in Solidity and accessed through blockchain wallets [5]. By eliminating the need for a central authority to oversee elections, this approach ensures a fair and transparent voting process where every vote is securely recorded and cannot be tampered with [6]. In essence, this project reimagines digital voting by leveraging blockchain’s strengths, making elections more secure, efficient, and trustworthy.
Open access
3 source records
Blockchain Technology Applications and Security
Internet Traffic Analysis and Secure E-voting
Advanced Steganography and Watermarking Techniques
\n In the first part of this work, we present, model and analyze a randomized automated peering model, that can be implemented to any distributed system. We conclude that the scheme has some desirable properties (specifically, a reasonable message overhead, a reasonable distribution of the numbers of peers of a node, and a negligible probability of an attack by a malicious actor to be successful). In the second part, we present an article published in the volume 136 of the journal Computers & Industrial Engineering, in October of 2019 (DOI 10.1016=j.cie.2019.07.025). In the paper, we analyze the Nash Equilibria of a graph attachment game, defined to represent the different strategies that malicious actors can use to take certain advantages in a DAG-based (i.e., based on Directed Acyclic Graphs) distributed ledger system. We prove the existence of almost symmetric Nash equilibria for the system where a part of players tries to optimize their attachment strategies and another part follows a default one. We also present simulations that show that the selfish players will not choose strategies that are considerably different that the recommended one.\n
Ji‐Young Kwak, Jong-choul Yim, Namseok Ko, Sun-Me Kim
The byzantine agreement protocol has a disadvantage that there are many limitations on node scalability, because the performance degradation may occur due to a large amount of traffic. Hence, this classical byzantine agreement algorithm seems to be infeasible to achieve scale-out performance with the same level of security as a Bitcoin. In order to improve the performance degradation due to a large amount of traffic, we propose the hierarchical consensus mechanism based on service-zone sharding rather than how all nodes participate in the consensus process. In the proposed consensus mechanism (SZHBFT), a disjoint set of transactions is locally processed by a secure consensus subgroup or globally processed between consensus subgroups. Thus, the transactions that occur related to multiple Service-Zone Consensus Groups are updated and maintained in the Inter-Service Zone Public Ledger, whereas service transactions occurring locally are processed in parallel by each Service-Zone Consensus Group and then distributed into a local Service-Zone Private Ledger. The scheme of the proposed SZHBFT mechanism provides the hierarchical agreement solution along with distributed multiledger structure for the scalable byzantine resilient agreement by forming secure consensus subgroups in order to minimize the overhead of overall communication messages.
This paper proposes a proximity-aware extensions to the current Bitcoin protocol, named Master Node Based Clustering (MNBC). The ultimate purpose of the proposed protocol is to evaluate the security and performance of grouping nodes based on physical proximity. In MNBC protocol, physical internet connectivity increases as well as the number of hops between nodes decreases through assigning nodes to be responsible for propagating based on physical internet proximity.
As the infrastructure to provide support for distributed database management systems, the distributed database platform is very important to unify the management of data distributed in intricate environments. However, a traditional distributed database platform with centralized entities faces diverse and serious threats when the central entity is compromised. Consensus mechanisms in distributed ledger technology (DLT) can enhance the capability of defending threats by decentralizing the platform, but the efficiency and cost of consensus mechanisms in classic blockchain techniques are notable issues. In this paper, we propose a novel decentralized database platform, named Dagbase, with the support of an efficient and cost-effective consensus mechanism that uses the directed acyclic graph (DAG) as the structure. Dagbase decentralizes the management and distributes data to prevent threats in untrustworthy environments, which gains benefits from recent DLT. The performance of near-native data reading and high-efficiency data writing is ensured by a layered architecture and DAG-based consensus. Furthermore, we ensure flexibility by decoupling the consensus mechanism from the architecture. Dagbase is also easy-to-use and can be integrated with mainstream database products seamlessly on account of great interoperability. The implementation demonstrates our work and the security and performance analysis are enforced for evaluation.
Smart contract helps to broaden the application of blockchain to various fields. In many cases, the non-blockchain systems (NBS) are involved. However, when a smart contract directly interacts with NBS, there is a non-deterministic issue (or a state conflict issue). The reason is that different nodes may obtain different statuses of NBS when the state changes in NBS. If we can solve this issue, a smart contract can be used to interact with current systems without an additional adaptor or bridge required by the existing solutions. In this paper, we regard the states of NBS as a sequence of states instead of a single state and propose to solve the non-deterministic issue by state synchronization. Blockchain nodes synchronize the state of the non-blockchain server via the P2P protocol. The state synchronization has requirements for both blockchain and NBS. For blockchain, it should provide the mechanism to synchronize states obtained from NBS. For NBS, it should sign the query result with a timestamp; the signature prevents the cheat of the observer (the blockchain), and the timestamp ensures the order of a state in the state sequence. At last, we show our verification results with respect to our proposed model and method.
Amaury Bouchra Pilet, Davide Frey, François Taı̈ani
Blockchains and distributed ledgers have brought renewed interest in Byzantine fault-tolerant protocols and decentralized systems, two domains studied for several decades. Recent promising works have in particular proposed to use epidemic protocols to overcome the limitations of popular Blockchain mechanisms, such as proof-of-stake or proof-of-work. These works unfortunately assume a perfect peer-sampling service, immune to malicious attacks, a property that is difficult and costly to achieve. We revisit this fundamental problem in this paper, and propose a novel Byzantine-tolerant peer-sampling service that is resilient to Sybil attacks in open systems by exploiting the underlying structure of wide-area networks.
This paper presents an architecture, based on Distributed Ledger Technologies (DLTs) and Decentralized File Storage (DFS) systems, to support the use of Personal Information Management Systems (PIMS). DLT and DFS are used to manage data sensed by mobile users equipped with devices with sensing capability. DLTs guarantee the immutability, traceability and verifiability of references to personal data, that are stored in DFS. In fact, the inclusion of data digests in the DLT makes it possible to obtain an unalterable reference and a tamper-proof log, while remaining compliant with the regulations on personal data, i.e. GDPR. We provide an experimental evaluation on the feasibility of the use of DFS. Three different scenarios have been studied: i) a proprietary IPFS approach with a dedicated node interfacing with the data producers, ii) a public IPFS service and iii) Sia Skynet. Results show that through proper configuration of the system infrastructure, it is viable to build a decentralized Personal Data Storage (PDS).
The global daily data generation is estimated to be more than 2.5 quintillion bytes, and more than 90 percent of the total data produced is generated in the last two years. Most of this data is being generated and controlled by very few centralized agencies in the Web 2.0 internet architecture. This causes issues, including data manipulation, lack of privacy, and data leaks historically and is not just limited to the fields mentioned. This paper proposes a Web 3.0 based architecture which eliminates the centralized agencies and to promote a fully decentralized, secure, and transparent internet. It leverages IPFS, a peer to peer distributed hypermedia transfer protocol. Ethereum and smart contracts create a secure decentralized mechanism for initiating data-based payments. Furthermore, the proposed architecture uses zero-knowledge proofs and proxy re-encryption mechanisms to enhance the privacy of the nodes in the network.
A key performance metric in blockchains is the latency between when a transaction is broadcast and when it is confirmed (the so-called, confirmation latency). While improvements in consensus techniques can lead to lower confirmation latency, a fundamental lower bound on confirmation latency is the propagation latency of messages through the underlying peer-to-peer (p2p) network (inBitcoin, the propagation latency is several tens of seconds). The de facto p2p protocol used by Bitcoin and other blockchains is based on random connectivity: each node connects to a random subset of nodes. The induced p2p network topology can be highly suboptimal since it neglects geographical distance, differences in bandwidth, hash-power and computational abilities across peers. We present Perigee, a decentralized algorithm that automatically learns an efficient p2p topology tuned to the aforementioned network heterogeneities, purely based on peers' interactions with their neighbors. Motivated by the literature on the multi-armed bandit problem, Perigee optimally balances the tradeoff between retaining connections to known well-connected neighbors, and exploring new connections to previously-unseen neighbors. Experimental evaluations show that Perigee reduces the latency to broadcast by $33\%$. Lastly Perigee is simple, computationally lightweight, adversary-resistant, and compatible with the selfish interests of peers, making it an attractive p2p protocol for blockchains.
The Bitcoin Lightning network is a mechanism to enable fast and inexpensive off-chain Bitcoin transactions using peer-to-peer (P2P) channels between nodes that can also be composed into a routing path. Although the resulting possible channel graphs are well-studied, there is no empirical data on the network's reliability in terms of being able to successfully route payments at a given moment in time. In this paper we address this gap and investigate two forms of availability that are a necessary ingredient to achieve such reliability. We first study the Lightning network's ability to route payments of various sizes to nearly every participating node, over most available channels. We establish an inverse relationship between payment volume and success rate and show that at best only about a third of destination nodes can be successfully reached. The routing is hampered by a number of possible errors, both transient and permanent. We then study the availability of nodes in the network longitudinally and determine how long-lived they are. Churn in the network is actually low, and a considerable number of nodes are hosted on cloud providers. By testing node liveness, we find that the propagated network information is relatively often stale, however, both for IP addresses and Tor onion addresses. We provide recommendations how the Lightning network can be improved, including considerations which trade-offs between privacy and decentralization on the one hand and reliability on the other hand should at least be reconsidered by the community developing the Lightning network.
We consider a particular instance of user interactions in the Bitcoin network, that of interactions among wallet addresses belonging to scammers. Aggregation of multiple inputs and change addresses are common heuristics used to establish relationships among addresses and analyze transaction amounts in the Bitcoin network. We propose a flow centric approach that complements such heuristics, by studying the branching, merger and propagation of Bitcoin flows. We study a recent sextortion campaign by exploring the ego network of known offending wallet addresses. We compare and combine different existing and new heuristics, which allows us to identify (1) Bitcoin addresses of interest (including possible recurrent go-to addresses for the scammers) and (2) relevant Bitcoin flows, from scam Bitcoin addresses to a Binance exchange and to other other scam addresses, that suggest connections among prima facie disparate waves of similar scams.
Factors affecting the reliability of data transmission in networks with nodes with periodic availability were considered. The principles of data transfer between robots are described; the need for global connectivity of communications within an autonomous system is shown, since the non-availability of information on the intentions of other robots reduces the effectiveness of the robotics system as a whole and affects the fault tolerance of a team of independent actors performing distributed activities. It is shown that the existing solutions to the problem of data exchange based on general-purpose IP networks have drawbacks; therefore, as the basis for organizing autonomous robot networks, we used developments in the domain of topological models of communication systems allowing us to build self-organizing computer networks. The requirements for the designed network for reliable message transfer between autonomous robots are listed, the option of organizing reliable message delivery using overlay networks, which expand the functionality of underlying networks, is selected. An overview of existing popular controlled and non-controlled overlay networks is given; their applicability for communication within a team of autonomous robots is evaluated. The features and specifics of data transfer in a team of autonomous robots are listed. The algorithms and architecture of the overlay self-organizing network were described by means of generally accepted methods of constructing decentralized networks with zero configurations. As a result of the work, general principles of operation of the designed network were proposed, the message structure for the delivery algorithm was described; two independent data streams were created, i.e. service and payload; an algorithm for sending messages between network nodes and an algorithm for collecting and synchronizing the global network status were developed. In order to increase the dependability and fault tolerance of the network, it is proposed to store the global network status at each node. The principles of operation of a distributed storage are described. For the purpose of notification on changes in the global status of the network, it is proposed to use an additional data stream for intra-network service messages. A flood routing algorithm was developed to reduce delays and speed up the synchronization of the global status of a network and consistency maintenance. It is proposed to provide network connectivity using the HELLO protocol to establish and maintain adjacency relations between network nodes. The paper provides examples of adding and removing network nodes, examines possible scalability problems of the developed overlay network and methods for solving them. It confirms the criteria and indicators for achieving the effect of self-organization of nodes in the network. The designed network is compared with existing alternatives. For the developed algorithms, examples of latency estimates in message delivery are given. The theoretical limitations of the overlay network in the presence of intentional and unintentional defects are indicated; an example of restoring the network after a failure is set forth.
Permissionless distributed ledgers provide a promising approach to deal with the Internet of Things (IoT) paradigm. Since IoT devices mostly generate data transactions and micropayments, distributed ledgers that use fees to regulate the network access are not an optimal choice. In this paper, we study a feeless architecture developed by IOTA and designed specifically for the IoT. Due to the lack of fees, malicious nodes can exploit this feature to generate an unbounded number of transactions and perform a denial of service attacks. We propose to mitigate these attacks through verifiable delay functions. These functions, which are non-parallelizable, hard to compute, and easy to verify, have been formulated only recently. In our work, we design a denial of service prevention mechanism which addresses network heterogeneity, limited node computational capabilities, and hardware-specific implementation optimizations. Verifiable delay functions have mostly been studied from a theoretical point of view, but little has been done in tangible applications. Hence, this paper can be considered as a pioneer work in the field, since it builds a bridge between this theoretical mathematical framework and a real-world problem.
The recent spread of COVID-19, stressed economies and government pumping money into the market has once again ignited the discussion on the need to have decentralised economies, the role of regulatory authorities and if bitcoin represents a true store of value. In this paper, we identify the need to alternate financial structure, discuss how blockchain and cryptocurrencies play a very important role in achieving it. Blockchain applications are heavily dependent on oracles for their interaction with outside world, we have discussed here the functioning of oracles and then finally presented a broad architecture that can be used to implement a majority of financial instruments on blockchain.
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 article, 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 in the Bitcoin network. We also adapt our model to study the impact of deploying a relay network and investigate the effect of the relay network size on the network performance and decentralization. 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 tradeoff 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. Additionally, we found that bigger relay networks can jeopardize the decentralization of the Bitcoin network.
Payment Channel Networks or PCNs have gained prominence ensuring faster relaying of transactions. However, this Layer-two solution has its own fair share of problems. Topological analysis on Lightning Network reveals that Griefing Attack is a major problem whereby an adversary intentionally exhausts the channel capacity of the network. It can be used for mounting series of targeted attacks like Denial-of-Service Attack, Node Isolation Attack and Channel Exhaustion Attack on honest participants as well. Though the attack does not always result in a direct monetary gain of the attacker, blocking of channel capacity for several days prevented several nodes from processing any future transaction request, leading to substantial collateral damage. Certain portions of the payment channel network get stalled which hampers the throughput and utility of the network. Mitigating Griefing Attack still remains an open problem. In this paper, we propose an efficient countermeasure for the attack, known as Griefing-Penalty. Mounting such an attack requires the attacker to pay a penalty proportional to the collateral cost of executing a payment. The penalty is used for compensating parties who incurred loss by locking funds. Our proposed strategy works for any timelock based payment protocol and ensures faster resolution of payments. To illustrate it, we propose a new payment protocol HTLC-GP or Hashed Timelock Contract with Griefing-Penalty. It not only preserves privacy but also ensures that an attacker cannot ascribe blame on any honest intermediary present in the path relaying a payment.
Inspired by Bitcoin, many different kinds of cryptocurrencies based on blockchain technology have turned up on the market. Due to the special structure of the blockchain, it has been deemed impossible to directly trade between traditional currencies and cryptocurrencies or between different types of cryptocurrencies. Generally, trading between different currencies is conducted through a centralized third-party platform. However, it has the problem of a single point of failure, which is vulnerable to attacks and thus affects the security of the transactions. In this paper, we propose a distributed cryptocurrency trading scheme to solve the problem of centralized exchanges, which can achieve secure trading between different types of cryptocurrencies. Our scheme is implemented with smart contracts on an Ethereum blockchain and deployed on an Ethereum test network. In addition to implementing transactions between individual users, our scheme also allows transactions among multiple users. The experimental result proves that the cost of our scheme is acceptable.
Diego Pennino, Maurizio Pizzonia, Andrea Vitaletti, Marco Zecchini
Proving that an endpoint (e.g. URL, telephone number, ecc.) is controlled by a subject is crucial in many applications. In the web, this is witnessed by the widespread adoption of HTTPS. In centralized architectures, this task is usually carried out by trusted certification authorities (CAs). In decentralized applications, for example based on blockchains, or for self-sovereign identity management (SSI), it would be desirable to perform these checks in a decentralized way, relying on the collective behavior of a society of individuals rather than on a single trusted entity. In any case, the result should be a widely usable certificate, as in the centralized CA case. In this paper, we show two blockchain-based methods to prove the association between a subject and an endpoint in a decentralized manner. Our methods are compatible with a wide variety of endpoints and contribute to fill the gap of the current SSI approaches with respect to decentralization. We analyze the security of our proposal and provide a proof-of-concept implementation. We also evaluate performances, costs, and compatibility with current standardization efforts about SSI.
Blockchain networks have been suggested to have the potential to support some of the most critical functions of modern societies. When used in such capacities, failures of blockchain networks imply catastrophes that extend beyond individuals, organizations and countries. As such, before considered for wide adoption, blockchain network protocols and technologies must undergo the highest standards of analytical and empirical validation subject to key security, reliability and performance qualities. When performing empirical evaluation, however, the sheer size of open-access blockchain networks in their envisioned scale rules out the possibility of exact reproduction and validation in a lab environment. Rather, abstract working models - simulators - of proposed technologies need to be considered. To have value as research instruments, such simulators need to be widely validated for their accuracy by the research community, and also be highly transparent and reusable for allowing quick implementation and comparison of design ideas. We claim that established software engineering paradigms, namely model-driven development and software product lines can help address this need. We outline our own effort to develop a domain meta-model and object-oriented framework for efficient and reliable derivation of specialized blockchain network simulators.