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DNS resolution attack on Bitcoin. The attacker poisons DNS cache and modifies the data. When a user queries the server to obtain IP addresses of peers who are accepting connections, he is routed to attacker's network. The attacker can game the user by feeding him fake blocks and transactions.
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... The probability of forks Empirical studies on blockchain protocols [19][20][21] have shown the emergence of forks, i.e. the simultaneous existence of multiple-potentially conflicting-blockchains among different groups of miners. In this paragraph we aim at giving a simple statistical intuition of this occurrence and its relationship to the interplay of two characteristic times: the mining times-governed by mining protocols and CPUs-and propagation times-governed by block sizes and network bandwidth. ...
Reaching consensus—a macroscopic state where the system constituents display the same microscopic state—is a necessity in multiple complex socio-technical and techno-economic systems: their correct functioning ultimately depends on it. In many distributed systems—of which blockchain-based applications are a paradigmatic example—the process of consensus formation is crucial not only for the emergence of a leading majority but for the very functioning of the system. We build a minimalistic network model of consensus formation on blockchain systems for quantifying how central nodes—with respect to their average distance to others—can leverage on their position to obtain competitive advantage in the consensus process. We show that in a wide range of network topologies, the probability of forming a majority can significantly increase depending on the centrality of nodes that initiate the spreading. Further, we study the role that network topology plays on the consensus process: we show that central nodes in scale-free networks can win consensus in the network even if they broadcast states significantly later than peripheral ones.
... In addition to the input data location, the miner stores a pointer to the transaction or a smart contract that corresponds to the solved CO problem instance in the nonce field of the block's header, enabling all participants to access its input data. The first example of data security issue involves preventing miners from performing selfish mining and other types of known frauds [81,82]. For example, miners could play the role of a customer and submit instances for which they already have highquality solutions with the aim of composing and adding blocks to the BC without much effort. ...
Blockchains (BCs) are distributed database systems, popular for their innovative, unsupervised maintenance process. They use a so-called consensus protocol to prevent inference by any third party of absolute trust. Security, privacy, consistency, and energy consumption have been identified as the main issues involved in BC maintenance. According to the recent literature, some of these issues can be formulated as combinatorial optimization (CO) problems, and this fact motivated us to consider incorporating CO approaches into a BC. In this paper, we propose the new combinatorial optimization consensus protocol (COCP) based on the proof-of-useful-work (PoUW) concept that assumes solving instances of real-life CO problems. Due to the complexity of the underlying CO problems, we have developed various types of heuristic methods, which are utilized in the COCP. Most of these methods are problem-dependent stochastic heuristic or metaheuristic methods. As is the case with the majority of consensus protocols, PoUW exhibits the property of asymmetry. It is difficult to find a solution for the considered CO problem; however, once a solution is found, its verification is straightforward. We present here a BC framework combining the two above-mentioned fields of research: BC and CO. This framework consists of improvements aiming towards developing the COCP of the PoUW type. The main advantage of this consensus protocol is the efficient utilization of computing resources (by exploring them for finding solutions of real-life CO problem instances), and the provision of a broad range of incentives for the various BC participants. We enumerate the potential benefits of the COCP with respect to its practical impacts and savings in power consumption, describing in detail an illustrative example based on part of the real-life BC network. In addition, we identify several challenges that should be resolved in order to implement a useful, secure, and efficient PoUW consensus protocol.
... Blockchains have economic incentives included within the protocol, and blockchain protocols can hold a lot of value for many people worldwide. However, this value gives power to certain individuals who control portions of either network that at times can be very centralized and susceptible to attacks such as majority mining or staking attacks (51% attacks) (Saad et al., 2019). While many people focus on how blockchain systems are decentralized at the base layer, maybe we should start focusing more on how systems can be decentralized from a governance perspective as well. ...
As Bitcoin continued to make headlines in 2021, additional digital assets such as non-fungible tokens brought more users into the blockchain ecosystem. As more individuals and entities took a closer look at the use cases for blockchain technology, the term metaverse began to emerge across news outlets and social media platforms. With Mark Zuckerberg, the Chief Executive Officer of Facebook, announcing that the organization would become a metaverse company and change the organization's name to Meta, this announcement came with some criticism in that the Meta metaverse would be centralized. In this case study, the current state of nation-states was viewed through the lens of Hobbes' The Leviathan to assess whether decentralized metaverses will transition to a Digital Leviathan using Bit.Country-a metaverse within the Polkadot blockchain ecosystem. The case study was conducted through interviews and uncovered that the quadruple bottom line implemented in conventional business could be transferrable to a digital world built on various blockchains, non-fungible tokens, and governance in a Digital Leviathan governed by the people.
... In order to deal with conflicting transactions in Tangle, Coordicide proposed fast probabilistic consensus (FPC) [71] and cellular automata consensus (CC) [72]. IOTA own mechanism can prevent heavyweight attacks [73,74], parasitic chain attacks [75], splitting attacks [76] and quantum computing attacks. ...
Nowadays, blockchain technology and industry has developed rapidly all over the world, which is inseparable from continuous innovation and improvement on smart contract technology. Therefore, by summarizing the working principle and application research status of blockchain smart contract, this paper analyzes the development and challenges of smart contract. Firstly, we introduce the model and operation principle of blockchain smart contract for the overall architecture, analyze the deployment process of smart contract with Ethereum, Hyperledger Fabric and EOSIO, and make a comparative analysis from the technical level. And taking Byteball, InterValue and IOTA platforms as examples, we introduce the deployment process and application potential for DAG-based blockchain smart contract. Additionally, we also summarize the application research of smart contract for international and Blockchain Oracle, and discuss its innovative application and development trend in the future. Secondly, we introduce the application status of smart contract with Ethereum and Hyperledger Fabric platforms from the aspects of financial transactions, Internet of things, medical applications, and supply chain, and further discuss EOS (enterprise operation system), Blockchain Oracle and other application fields. Furthermore, we introduce the application advantages and challenges to smart contract for industrial Internet from the fields of manufacturing, food industry, industrial Internet of things and industry 4.0. Finally, we discuss the challenges faced by smart contract with technical issues, analyzes the impact on large-scale applications and mining system on the sustainable development of smart contract, and looks forward to the future research direction of blockchain smart contract.
... Although the decentralized nature of peer-to-peer (P2P) networks provides enormous advantages and mitigates substantial security risks, it is, yet, vulnerable to 51% attacks [92]. This is especially intimidating in the case of UAV networks, where UAVs can join and leave freely [45]. ...
The breakthrough of blockchain technology has facilitated the emergence and deployment of a wide range of unmanned aerial vehicles (UAV) networks-based applications. Yet, the full utilization of these applications is still limited due to the fact that each application is operating on an isolated blockchain. Thus, it is inevitable to orchestrate these blockchain fragments by introducing a cross-blockchain platform that governs the inter-communication and transfer of assets in the UAV networks context. In this paper, we survey the literature on the state-of-the-art cross blockchain frameworks to highlight the latest advances in the field. We also provide an up-to-date review of blockchain-based UAV networks applications. Based on the outcomes of our survey, we introduce a spectrum of scenarios related to UAV networks that may leverage the potentials of the currently available cross-blockchain solutions. Finally, we identify open issues and potential challenges associated with the application of a cross-blockchain scheme for UAV networks that will hopefully guide future research directions.
... Though blockchains are generally considered to be very secure systems, they may be susceptible to various kinds of attacks and must be carefully designed in order to prevent them. One potential attack is the 51% attack, in which an attacker attempts to control the network by taking control of a sufficient number of validators [17]. In permissioned networks, this attack is generally prevented by carefully selecting and protecting validators, ensuring both that the validators are trusted to not participate in such an attack, and that the machines holding their private keys are not vulnerable to attack. ...
Modern vehicles rely on data from a vast array of sensors such as radar and GPS equipment that can be shared with surrounding vehicles and other interested parties. Vehicle-to-everything (V2X) is the collection of systems that enable such communication. Although this data sharing has the potential to improve both the safety and efficiency of vehicles, ensuring that what is shared has not been altered, deleted, forged, leaked, or otherwise tampered with remains a challenging problem. Today, blockchain technology allows a system’s participants to come to an agreement (consensus) on the state of the system and its data in a decentralized, trustless manner. This new technology may be capable of securing V2X data, as well as enabling other useful V2X services such as payments. However, the V2X ecosystem poses several unique challenges that complicate the application of blockchain technology, not least of which is the vast number of communications that any proposed blockchain network will need to support. This paper gives an overview of V2X and blockchain technology, explores potential applications of blockchain within the V2X domain, and justifies its importance. It also reviews, analyzes, and discusses various blockchain architectures that could support V2X applications. Though there is a place for blockchain in the V2X environment, currently there is no robust or mature blockchain architecture available that could support the entire ecosystem’s needs. As such, this paper proposes novel directions for future research towards the creation of such a blockchain.
... Although he or she didn't refer to the blockchain by the name per se, the blockchain idea goes far before when it was initially described as a technique to timestamp digital doc-uments [2] in 1991. Ever since, it has been a race on innovating applications based on it, such as smart contracts, communication systems, healthcare systems, censorship resistance systems, electronic voting, national ID systems, and of course, cryptocurrencies hold the lion's share [3]. ...
... In May and Jun. 2018, five Blockchain-based cryptocurrencies, namely, Monacoin, Bitcoin Gold, Zencash, Verge, and Litecoin Cash, were targeted by the 51% attack, which performed double spending on valuable transactions, which led to a loss of $5 million [3]. Such incidents lead to severe concerns and require more research on the blockchain and its applications. ...
Blockchain technology is now being used in every aspect of human life. It appears like everyone is racing to develop apps that run on top of the blockchain technology available today. Indeed, this is owing to the fact that it has distinct qualities and a distinctive design. However, it is not well suited to all applications of blockchain technology. Not merely altering the blockchain protocols would make it suitable, but instead redesigning its architecture is required to make it ideal for different applications. This paper describes the overview of blockchain technology thoroughly. It provides a detailed discussion on the prevalent core-oriented and client-oriented attacks on blockchain technology and the vulnerabilities exploited by them. It also presents the possible countermeasure to these attacks. Moreover, it provides insight into the creation of a better version of the blockchain that is more suitable for different types of blockchain applications.
... People who are working on the Bitcoin are threatened by these vulnerabilities, which, if executed, can bring many damages. A publicly verifiable algorithm can be used (Karame et al., 2012) Punitive and feather forking (Miller, 2013;Narayanan et al., 2016) Blacklisting Based two-factor security can be incorporated (Gennaro et al., 2016;Goldfeder et al., 2014), Hardware wallets (Bamert et al., 2014) TrustZone-backed Bitcoin wallet (Jarecki et al., 2016), Password-protected secret sharing (PPSS) (Saad et al., 2019) Time jacking (Miller, 2013, Corbixgwelt, 2011 Attackers (Danezis et al., 2003), CoinJoin (Maxwell, 2013), CoinShuffle (Ruffing et al., 2014) Double spending (Biryukov et al., 2014;Ghosh et al., 2020;Koshy et al., 2014;Saad et al., 2019) Used the same currency in several transactions, sending two inconsistent transactions in rapid succession. From Table 1, it is clear that malicious users can attack a cryptocurrency in many ways. ...
... People who are working on the Bitcoin are threatened by these vulnerabilities, which, if executed, can bring many damages. A publicly verifiable algorithm can be used (Karame et al., 2012) Punitive and feather forking (Miller, 2013;Narayanan et al., 2016) Blacklisting Based two-factor security can be incorporated (Gennaro et al., 2016;Goldfeder et al., 2014), Hardware wallets (Bamert et al., 2014) TrustZone-backed Bitcoin wallet (Jarecki et al., 2016), Password-protected secret sharing (PPSS) (Saad et al., 2019) Time jacking (Miller, 2013, Corbixgwelt, 2011 Attackers (Danezis et al., 2003), CoinJoin (Maxwell, 2013), CoinShuffle (Ruffing et al., 2014) Double spending (Biryukov et al., 2014;Ghosh et al., 2020;Koshy et al., 2014;Saad et al., 2019) Used the same currency in several transactions, sending two inconsistent transactions in rapid succession. From Table 1, it is clear that malicious users can attack a cryptocurrency in many ways. ...
Security and privacy are the two terms that are well connected with the current trends in cryptocurrency, and this study gives an extensive review of the same. Cryptocurrency adds security to the transaction flow and regulates the formation of additional units of currency. The massive growth in the market assessment of cryptocurrency leads to misuse of deficiencies for profit by adversaries. In this study, a review was made to focus on the security and protection measurements of cryptocurrencies specifically on Bitcoin. This study describes cryptocurrency conventions, their usefulness, and communications within the framework.
... In the case of the most popular blockchains as Bitcoin and Ethereum, consensus is constructed by means of the so-called Proof-of-Work or PoW. The PoW is a mathematical puzzle based on the exhaustive search of hash collisions, and its security is determined by the computational power of one or more entities with more than the 51% of the computational power of the whole blockchain network, and which collude to subvert the decentralized nature of the underlying distributed ledger to control data insertion [12]. We have to take into account Grover's (and, eventually, Simon's) algorithm reduces the computational cost of the problem associated to searching for hash collisions, but PoW is not only derived from hash collision searches, since it also depends on how the outcome of PoW is propagated through the P2P network of the blockchain and how that outcome is validated and accepted by the rest of the entities. ...
Blockchain and quantum computing are trending topics in nowadays scientific communication, and they increasingly attract the attention of academia, but also industry stakeholders and policymakers. In this communication, we address the conundrum related to the quantum menace and the deployment of blockchain solutions. As any cryptographic product, blockchain security is affected by the advent of universal quantum computers. Besides the more or less certainty about its immediacy, we underline that blockchain is not substantially different from other secure and resilient platforms in such regard. On this ground, we discuss the main points of the roadmap that the research community in cryptography is currently taking to tackle the quantum challenge, and we highlight how these points should be properly integrated in the design and implementation of the life-cycle of blockchain products.
... It is a key research to analyze the orphan blocks of blockchain selfish mining and their influence on the waste of computing resource of blockchain. For qualitative analysis of orphan blocks, readers may refer to, such as Carlsten et al. [12], Velner et al. [89], Stifter et al. [87], Saad et al. [81] and Awe et al. [1]. However, so far none of previous works has developed an effective method to analyze the orphan blocks of blockchain selfish mining. ...
In this paper, we provide a new theoretical framework of pyramid Markov processes to solve some open and fundamental problems of blockchain selfish mining. To this end, we first describe a more general blockchain selfish mining with both a two-block leading competitive criterion and a new economic incentive, and establish a pyramid Markov process to express the dynamic behavior of the selfish mining from both consensus protocol and economic incentive. Then we show that the pyramid Markov process is stable and so is the blockchain, and its stationary probability vector is matrix-geometric with an explicitly representable rate matrix. Furthermore, we use the stationary probability vector to be able to analyze the waste of computational resource due to generating a lot of orphan (or stale) blocks. Nextly, we set up a pyramid Markov reward process to investigate the long-run average profits of the honest and dishonest mining pools, respectively. Specifically, we show that the long-run average profits are multivariate linear such that we can measure the improvement of mining efficiency of the dishonest mining pool comparing to the honest mining pool. As a by-product, we build three approximative Markov processes when the system states are described as the block-number difference of two forked block branches. Also, by using their special cases with non network latency, we can further provide some useful interpretation for both the Markov chain (Figure 1) and the revenue analysis ((1) to (3)) of the seminal work by Eyal and Sirer (2014). Finally, we use some numerical examples to verify the correctness and computability of our theoretical results. We hope that the methodology and results developed in this paper shed light on the blockchain selfish mining such that a series of promising research can be produced potentially.
