Bitcoins and Blockchain technologies are attracting the attention of different scientific communities. In addition, their widespread industrial applications and the continuous introduction of cryptocurrencies are also stimulating the attention of the public opinion. The underlying structure of these technologies constitutes one of their core concepts. In particular, they are based on peer-to-peer networks. Accordingly, all nodes lie at the same level, so that there is no place for privileged actors as, for instance, banking institutions in classical financial networks. In this work, we perform a preliminary investigation on two kinds of network, i.e. the Bitcoin network and the Bitcoin Cash network. Notably, we analyze their global structure and we try to evaluate if they are provided with a small-world behavior. Results suggest that the principle known as 'fittest-gets-richer', combined with a continuous increasing of connections, might constitute the mechanism leading these networks to reach their current structure. Moreover, further observations open the way to new investigations into this direction.
Bitcoins and Blockchain technologies are attracting the attention of different scientific communities. In addition, their widespread industrial applications and the continuous introduction of cryptocurrencies are also stimulating the attention of the public opinion. The underlying structure of these technologies constitutes one of their core concepts. In particular, they are based on peer-to-peer networks. Accordingly, all nodes lie at the same level, so that there is no place for privileged actors as, for instance, banking institutions in classical financial networks. In this work, we perform a preliminary investigation on two kinds of network, i.e. the Bitcoin network and the Bitcoin Cash network. Notably, we analyze their global structure and we try to evaluate if they are provided with a small-world behavior. Results suggest that the principle known as 'fittest-gets-richer', combined with a continuous increasing of connections, might constitute the mechanism leading these networks to reach their current structure. Moreover, further observations open the way to new investigations into this direction.
Alexander Yakubov, Wazen M. Shbair, Anders Wallbom, David Sanda · 5 authors
Public-Key Infrastructure (PKI) is the cornerstone technology that facilitates secure information exchange over the Internet. However, PKI is exposed to risks due to potential failures of Certificate Authorities (CAs) that may be used to issue unauthorized certificates for end-users. Many recent breaches show that if a CA is compromised, the security of the corresponding end-users will be in risk. As an emerging solution, Blockchain technology potentially resolves the problems of traditional PKI systems - in particular, elimination of single point-of-failure and rapid reaction to CAs shortcomings. Blockchain has the ability to store and manage digital certificates within a public and immutable ledger, resulting in a fully traceable history log. In this paper we designed and developed a blockchain-based PKI management framework for issuing, validating and revoking X.509 certificates. Evaluation and experimental results confirm that the proposed framework provides more reliable and robust PKI systems with modest maintenance costs.
The recent explosion of interest in blockchains led to a plethora of proposals for their application, including attempts to decentralize some centralized network functions. At the same time, real "distributed wireless networks" are emerging. Community networks, for instance, are large mesh networks made of hundreds of nodes built by communities primarily to solve digital divide, and they are thriving. The challenges these networks face are not only technological: they deal with creating incentives to participate, with the business model they may adopt, and with their internal governance. Very few models have been proposed to apply blockchains to bottom-up distributed networks: we instead expose how they can solve many problems which so far hindered the diffusion of such networks. Maybe we can push this further: a network is, in essence, a system in which all nodes find a rough consensus on the best paths to connect a node with another. Can we use this consensus method to run a distributed ledger and a cryptocurrency within the network itself, rather than simply applying to networks the effects of a blockchain defined in a separate system? This paper introduces this concept, named "Proof of Networking", and discusses its potential avails.
Large-scale rumor spreading could pose severe social and economic damages. The emergence of online social networks along with the new media can even make rumor spreading more severe. Effective control of rumor spreading is of theoretical and practical significance. This paper takes the first step to understand how the blockchain technology can help limit the spread of rumors. Specifically, we develop a new paradigm for social networks embedded with the blockchain technology, which employs decentralized contracts to motivate trust networks as well as secure information exchange contract. We design a blockchain-based sequential algorithm which utilizes virtual information credits for each peer-to-peer information exchange. We validate the effectiveness of the blockchain-enabled social network on limiting the rumor spreading. Simulation results validate our algorithm design in avoiding rapid and intense rumor spreading, and motivate better mechanism design for trusted social networks.
Bitcoin, as well as many of its successors, require the whole transaction record to be reliably acquired by all nodes to prevent double-spending. Recently, many blockchains have been proposed to achieve scale-out throughput by letting nodes only acquire a fraction of the whole transaction set. However, these schemes, e.g., sharding and off-chain techniques, suffer from a degradation in decentralization or the capacity of fault tolerance. In this paper, we show that the complete set of transactions is not a necessity for the prevention of double-spending if the properties of value transfers is fully explored. In other words, we show that a value-transfer ledger like Bitcoin has the potential to scale-out by its nature without sacrificing security or decentralization. Firstly, we give a formal definition for the value-transfer ledger and its distinct features from a generic database. Then, we introduce an off-chain based scheme with a shared main chain for consensus and an individual chain for each node for recording transactions. A locally executable validation scheme is proposed with uncompromising validity and consistency. A beneficial consequence of our design is that nodes will spontaneously try to reduce their transmission cost by only providing the transactions needed to show that their transactions are double-spending-proof. As a result, the network is sharded as each node only acquires part of the transaction record and a scale-out throughput could be achieved, which we call "spontaneous sharding".
We discuss the issue of what we call {\em incentive mismatch}, a fundamental problem with public blockchains supported by economic incentives. This is an open problem, but one potential solution is to make application portable. Portability is desirable for applications on private blockchains. Then, we present examples of middleware designs that enable application portability and, in particular, support migration between blockchains.
The latency and throughput of blockchain-based cyrptocurrencies is a major concern for their suitability as mainstream currencies and as transaction processors in general. The prevalent proof-of-work scheme, exemplified by Bitcoin, is a deliberately laborious effort: the time and energy required to mine blocks makes the blockchain virtually immutable and assists in the consensus-reaching process. Coinspermia (coin=money + spermia=seed) is a different approach: transactions are concurrently seeded throughout a network of peer nodes to an extent sufficient to achieve a high reliability of essential currency operations, including the fast transfer of coins from an owner to a recipient, and the prevention of double spending. A number of Bitcoin features are retained in Coinspermia, including transaction input-outputs and cryptographic addresses and signing, but no special proof-of-work is required to commit transactions. Instead, a client can be assured of an operation completion when a quorum of network nodes acknowledge the operation, which can occur before a transaction operation finishes propagating through the network. Simulation substantiates improved latency and throughput.
The topic of cryptocurrencies has been on the forefront of investors’ minds as they have seen ridiculous returns from the volatile swings in price. Its value highly debated because the asset is not backed by a hard asset. If we look back at the beginning of our country, we see how each state had its own currency and the difficulties that users faced around who would accept that as legal tender. The birth of a federal currency was accepted because it served as a medium of exchange and was backed by gold through the U.S. government. The final evolution of the U.S. dollar was moving away from the gold standard to a fiat currency backed only by the confidence in the U.S. government’s word. Today, we live in a globalized world where there is significant communication between countries around the globe that it seems that we have almost come to the same crossing point that our country saw when it first adopted a federal currency. For cryptocurrencies to be adopted as the standard around the world, we must first discuss why they would carry the same value as the current federal currencies that are already set in place and why there may be a shift. The paper will be investigating the reasons that cryptocurrencies may gain popularity first as a flight to quality asset before a widespread adoption throughout business and individuals. This carries great importance as the adoption of cryptocurrencies would mark a new era of untested, autonomous free markets around the globe. We will look at current debt levels, different asset class correlations, perceived stable currencies, and if cryptocurrencies can act as an alternative asset. The current idea of flight to quality assets is moving away from more risky assets like equities or unstable currencies to fixed income or stable currencies like the USD but what if investors lose faith in some of the U.S. denominated assets?
Lightweight clients are gaining increasing adoption in existing blockchain deployments, owing to their reduced resource consumption. There are currently a number of libraries that implement lightweight clients (e.g., BIP37, Electrum, LES, filter commitments). Notice that these libraries are intrinsically different and require significant effort to be integrated across blockchain platforms. Additionally, lightweight clients require the cooperation of full nodes, which are expected to invest in their computational (to run filters) and bandwidth resources in order to serve lightweight clients. Existing blockchains however offer no rewards for full nodes in exchange-which offers little incentives for full nodes to correctly serve lightweight clients.
The rise of cryptocurrency as a new sui generis asset class creates a need for a new classification scheme to cover the wide range of functionality for which tokens can be used. By differentiating tokens based on their functional attributes, cryptocurrency tokens can be categorised into crypto-transaction tokens (which act as a cash substitute); crypto-fuel tokens (which underpin generic blockchain applications); and crypto-voucher tokens (which can be exchanged for a predefined asset). This classification is applied to identify important issues when considering whether to participate in a cryptocurrency system, such as the impact of potential forks, token supply expectations and the level of dependence on a few operators (entity-dependence). For crypto-transaction tokens (and crypto-fuel tokens if used in a similar or overlapping role) it shows the importance of the token being seen as a “better” form of money. For crypto-fuel tokens, the popularity of blockchain applications and the utility of the crypto-fuel system in application development is vital. For crypto-voucher tokens, the value of the underlying asset, the token’s exchangeability for that asset and the importance of a digital representation should be considered by participants. The interplay between fundamentals and speculation as drivers of price is considered.An erratum to this article has been published at as DOI: https://doi.org/10.5195/ledger.2018.151.
Since the introduction of Bitcoin in 2009, it has gained a significant popularity around the world. Bitcoin is a peer-to-peer electronic payment system where payment transactions are stored in a data structure named the block-chain. Based on a fully decentralized network, the blockchain is maintained by a community of participants. In Bitcoin system, mining is the fundamental concept. In this paper, we design a new Bitcoin mining scheme based on the multi-leader multi-follower Stackelberg game model. To effectively implement the peer-to-peer relationship of Bitcoin system agents, we assume that mining pool operators are leaders and mining participating users are followers in our Stackelberg game. By using the dynamics of feedback-based repeated process, leaders, and followers can be interacting with one another and make their decisions in a way to reach an efficient system solution. Without the influence of any central authorities and organizations, the proposed method is practically applied to a distributed Bitcoin system. Through system level simulations, we show that our game approach outperforms the existing Bitcoin schemes in providing a better fair-efficient system performance.
The personal health information (PHI) is an activity among the health-care providers and the patients in terms of managing the data which is sensitive to the parties. The PHI data have been maintained by multiple health-care providers, thus resulting in separated data. Moreover, the PHI data are stored in the provider’s database, hence the patients have no authority to manage their own information. Therefore, in this article, we propose a conceptual model for managing the PHI data which is derived from several health-care providers by relying on the blockchain technology in the peer-to-peer overlay network. In addition, we elaborate the security analysis that might be occurring in the proposed model. By leveraging on our model, it allows the patients and the providers to collect effectively the PHI data onto a single view as well guarantee of data integrity. The blockchain offers an immutable of the data record without having to trust a third party. The experimental results show that the proposed approach is promising to be developed due to the high success rate in terms of data dissemination.
In recent years, with the rapid development and popularization of BitCoin, the research of blockchain technology has also shown growth. It has gradually become a new generation of distributed, non-centralized and trust-based technology solution. However, the blockchain operation is expensive and transaction is delayed. Take BitCoin as an example. On the one hand, a block is produced every ten minute. On the other hand, once the new block is generated, it takes a certain time to propagate world wide. The slow speed of propagation determines that BitCoin can not use too small block interval time. Ethereum also faces similar problems, so the concept of uncle block was introduced to reduce blockchain forks. This paper introduces a new tree structure based broadcast propagation routing model, providing a novel method to organize network nodes and message propagation mechanism. In oder to avoid the single node failure problem, the tree cluster routing is proposed. The research shows that the tree based routing can accelerate broadcast convergence time and reduce redundant traffic.
Yunhua He, Hong Li, Xiuzhen Cheng, Yan Liu · 6 authors
In distributed peer-to-peer (P2P) applications, peers self-organize and cooperate to effectively complete certain tasks such as forwarding files, delivering messages, or uploading data. Nevertheless, users are selfish in nature and they may refuse to cooperate due to their concerns on energy and bandwidth consumption. Thus each user should receive a satisfying reward to compensate its resource consumption for cooperation. However, suitable incentive mechanisms that can meet the diverse requirements of users in dynamic and distributed P2P environments are still missing. On the other hand, we observe that Blockchain is a decentralized secure digital ledger of economic transactions that can be programmed to record not just financial transactions and Blockchain-based cryptocurrencies get more and more market capitalization. Therefore in this paper, we propose a Blockchain based truthful incentive mechanism for distributed P2P applications that applies a cryptocurrency such as Bitcoin to incentivize users for cooperation. In this mechanism, users who help with a successful delivery get rewarded. As users and miners in the Blockchain P2P system may exhibit selfish actions or collude with each other, we propose a secure validation method and a pricing strategy, and integrate them into our incentive mechanism. Through a game theoretical analysis and evaluation study, we demonstrate the effectiveness and security strength of our proposed incentive mechanism.
P2P networks are the mechanism used by cryptocurrencies to disseminate system information while keeping the whole system as much decentralized as possible. Cryptocurrency P2P networks have new characteristics that propose new challenges and avoid some problems of existing P2P networks. By characterizing the most relevant cryptocurrency network, Bitcoin, we provide details on different properties of cryptocurrency networks and their similarities and differences with standard P2P network paradigms. Our study allows us to conclude that cryptocurrency networks present a new paradigm of P2P networks due to the mechanisms they use to achieve high resilience and security. With this new paradigm, interesting research lines can be further developed, both in the focused field of P2P cryptocurrency networks and also when such networks are combined with other distributed scenarios.
Blockchain-based cryptocurrencies have demonstrated how to securely implement traditionally centralized systems, such as currencies, in a decentralized fashion. However, there have been few measurement studies on the level of decentralization they achieve in practice. We present a measurement study on various decentralization metrics of two of the leading cryptocurrencies with the largest market capitalization and user base, Bitcoin and Ethereum. We investigate the extent of decentralization by measuring the network resources of nodes and the interconnection among them, the protocol requirements affecting the operation of nodes, and the robustness of the two systems against attacks. In particular, we adapted existing internet measurement techniques and used the Falcon Relay Network as a novel measurement tool to obtain our data. We discovered that neither Bitcoin nor Ethereum has strictly better properties than the other. We also provide concrete suggestions for improving both systems.
Oğuzhan Ersoy, Zhijie Ren, Zekeriya Erkin, Reginald L. Lagendijk
Existing permissionless blockchain solutions rely on peer-to-peer propagation mechanisms, where nodes in a network transfer transaction they received to their neighbors. Unfortunately, there is no explicit incentive for such transaction propagation. Therefore, existing propagation mechanisms will not be sustainable in a fully decentralized blockchain with rational nodes. In this work, we formally define the problem of incentivizing nodes for transaction propagation. We propose an incentive mechanism where each node involved in the propagation of a transaction receives a share of the transaction fee. We also show that our proposal is Sybil-proof. Furthermore, we combine the incentive mechanism with smart routing to reduce the communication and storage costs at the same time. The proposed routing mechanism reduces the redundant transaction propagation from the size of the network to a factor of average shortest path length. The routing mechanism is built upon a specific type of consensus protocol where the round leader who creates the transaction block is known in advance. Note that our routing mechanism is a generic one and can be adopted independently from the incentive mechanism.
Adoption of Cryptocurrency has grown significantly over the time and becoming more popular among young generation. People are calling it currency of new digital era. In this research work we are reviewing the dominant Cryptocurrency systems and its underlying disruptive Innovations and Technologies.
Ethereum, a cryptocurrency currently valued at 46 billion US dollars, has grown over 6,500% in the last 12 months. Despite the growth in value, we still have very limited Ethereum network visibility. In this thesis, we analyze the Ethereum network from two vantage points: the DEVp2p network and the Ethereum Mainnet. The DEVp2p peer-to- peer (P2P) network was developed specifically for and ultimately underlies the Ethereum Mainnet. We examine overall composition of the DEVp2p network. We analyze our peer connections on the Ethereum Mainnet—the main Ethereum network established on top of DEVp2p. We compare the Ethereum network’s properties to those of other well-studied P2P networks, namely BitTorrent and Gnutella. We develop novel techniques to measure the Ethereum P2P network and gain visibility into this previously opaque network.