A flexible n/2 adversary node resistant and halting recoverable blockchain sharding protocol

Blockchain sharding is a promising approach to solving the dilemma between decentralisation and high performance (transaction throughput) for blockchain. The main challenge of Blockchain sharding systems is how to reach a decision on a statement among a sub-group (shard) of people while ensuring the whole population recognises this statement. Namely, the challenge is to prevent an adversary who does not have the majority of nodes globally but have the majority of nodes inside a shard. Most Blockchain sharding approaches can only reach a correct consensus inside a shard with at most $n/3$ evil nodes in a $n$ node system. There is a blockchain sharding approach which can prevent an incorrect decision to be reached when the adversary does not have $n/2$ nodes globally. However, the system can be stopped from reaching consensus (become deadlocked) if the adversary controls a smaller number of nodes. In this paper, we present an improved Blockchain sharding approach that can withstand $n/2$ adversarial nodes and recover from deadlocks. The recovery is made by dynamically adjusting the number of shards and the shard size. A performance analysis suggests our approach has a high performance (transaction throughput) while requiring little bandwidth for synchronisation

All that Glitters is not Bitcoin - Unveiling the Centralized Nature of the BTC (IP) Network

peer reviewedBlockchains are typically managed by peer-to-peer (P2P) networks providing the support and substrate to the so-called distributed ledger (DLT), a replicated, shared, and synchronized data structure, geographically spread across multiple nodes. The Bitcoin (BTC) blockchain is by far the most well-known DLT, used to record transactions among peers, based on the BTC digital currency. In this paper we focus on the network side of the BTC P2P network, analyzing its nodes from a purely network measurements-based approach. We present a BTC crawler able to discover and track the BTC P2P network through active measurements, and use it to analyze its main properties. Through the combined analysis of multiple snapshots of the BTC network as well as by using other publicly available data sources on the BTC network and DLT, we unveil the BTC P2P network, locate its active nodes, study their performance, and track the evolution of the network over the past two years. Among other relevant findings, we show that (i) the size of the BTC network has remained almost constant during the last 12 months -- since the major BTC price drop in early 2018, (ii) most of the BTC P2P network resides in US and EU countries, and (iii) despite this western network locality, most of the mining activity and corresponding revenue is controlled by major mining pools located in China. By additionally analyzing the distribution of BTC coins among independent BTC entities (i.e., single BTC addresses or groups of BTC addresses controlled by the same actor), we also conclude that (iv) BTC is very far from being the decentralized and uncontrolled system it is so much advertised to be, with only 4.5% of all the BTC entities holding about 85% of all circulating BTC coin

Evaluating prevailing Bitcoin valuation models – how do they work and how do they perform today?

Bitcoin has, since the first coin was mined in 2009, taken the world by storm. Today, millions of people are embracing the digital currency, and is evident that the growth is not going to halt any time soon. The increased adoption of Bitcoin raises the question about the fair value of the asset. What is the best way to fairly value Bitcoin, if it has any fundamental value at all? Numerous valuation models for Bitcoin have been proposed throughout the years. The majority of today's most popular models were presented between 2017 and 2019, and much has transpired since then. In this thesis, we will examine Bitcoin's underlying technology and the opportunities and challenges it brings for the contemporary world. Currently, we are discovering that digital assets and Bitcoin offer a number of opportunities that provide utility and convenience for consumers that utilize the digital asset market. To maintain objectivity, we will also discuss the issues connected with the widespread use of digital assets like Bitcoin. Finally, we will explore whether present techniques of valuing Bitcoin may be regarded as a "fair" manner of valuing Bitcoin. In addition, we will contribute to the existing research on Bitcoin valuation by suggesting improvements in the current valuation methods that we believe holds merit

Evaluating prevailing Bitcoin valuation models – how do they work and how do they perform today?

Bitcoin has, since the first coin was mined in 2009, taken the world by storm. Today, millions of people are embracing the digital currency, and is evident that the growth is not going to halt any time soon. The increased adoption of Bitcoin raises the question about the fair value of the asset. What is the best way to fairly value Bitcoin, if it has any fundamental value at all? Numerous valuation models for Bitcoin have been proposed throughout the years. The majority of today's most popular models were presented between 2017 and 2019, and much has transpired since then. In this thesis, we will examine Bitcoin's underlying technology and the opportunities and challenges it brings for the contemporary world. Currently, we are discovering that digital assets and Bitcoin offer a number of opportunities that provide utility and convenience for consumers that utilize the digital asset market. To maintain objectivity, we will also discuss the issues connected with the widespread use of digital assets like Bitcoin. Finally, we will explore whether present techniques of valuing Bitcoin may be regarded as a "fair" manner of valuing Bitcoin. In addition, we will contribute to the existing research on Bitcoin valuation by suggesting improvements in the current valuation methods that we believe holds merit