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.
This report examines how advances in data science and encoding could improve transport. It investigates three linked and rapidly changing areas: First, it discusses the deployment of blockchain and other distributed ledger-based approaches, that record transactions efficiently and in a verifiable and permanent way. Secondly, the study looks at open algorithms and other alternatives to traditional data-sharing. Finally, it reviews the development of a common data syntax for encoding mobility services.
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.
Scalability of distributed ledgers is a key adoption factor. As an alternative to blockchain-based protocols, directed acyclic graph (DAG) protocols are proposed with the intention to allow a higher volume of transactions to be processed. However, there is still limited understanding of the behaviour and security considerations of DAG-based systems. We present an asynchronous, continuous time, and multi-agent simulation framework for DAG-based cryptocurrencies. We model honest and semi-honest actors in the system to analyse the behaviour of one specific cryptocurrency, IOTA. Our simulations show that the agents that have low latency and a high connection degree have a higher probability of having their transactions accepted in the network with honest and semi-honest strategies. Last, the simulator is built with extensibility in mind. We are in the process of implementing SPECTRE as well as including malicious agents.
This chapter is the first of our applied practice chapters. It walks through the two fundamental Ethereum interactions. In the first project, we will broadcast a transaction to three Ethereum networks. In the second project, we will deploy a simple Hello World contract.
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.