From Blockchain to Internet-based Voting

Blockchain has been one of the hottest topics among the state-of-the-art technologies. As the enabling technology for Bitcoin, the pioneering cryptocurrency, blockchain is an append-only distributed ledger that is virtually impossible to attack. Hence, blockchain holds great promises as the fundamental technology to enable Internet-based electronic voting. However, Internet-based voting has additional requirements than what monetary transactions such as Bitcoin have to offer. In this thesis, we discuss the key differences of a blockchain-based voting system with digital currencies. In this context we also highlight the requirements, review existing proposed solutions, and outline possible improvements. Specifically, we propose several schemes on how to tackle various issues such as authentication, privacy, transparency, scalability, safety, as well as several other practical aspects of the platform. Most importantly, a blockchain-based voting system needs to ensure that the prospect of tampering with the election result is to a large extent eliminated. At the same time, the voting platform should have proper performance characteristics, i.e. sufficient throughput, for a voting of large magnitude such as a presidential election. Being heavily linked together, security and performance should be investigated in a unified framework to capture the interaction effects between the two. To address this concern, for the first time, we will study the performance and security implications of the blockchain voting system in a quantitative manner, using a blockchain simulator developed by researchers at Swiss Federal Institute of Technology, ETH Zurich. In our analysis, we will specifically investigate the stale block rate and relative mining share of the dishonest network, as the central security measures, as a function of important network parameters that determine the throughput of the network, i.e. block size and block interval. Ultimately, we focus on selfish mining and eclipse attacks as the most critical threats to the integrity of the blockchain voting in order to find the optimal network parameters

From Blockchain to Internet-based Voting

Blockchain has been one of the hottest topics among the state-of-the-art technologies. As the enabling technology for Bitcoin, the pioneering cryptocurrency, blockchain is an append-only distributed ledger that is virtually impossible to attack. Hence, blockchain holds great promises as the fundamental technology to enable Internet-based electronic voting. However, Internet-based voting has additional requirements than what monetary transactions such as Bitcoin have to offer. In this thesis, we discuss the key differences of a blockchain-based voting system with digital currencies. In this context we also highlight the requirements, review existing proposed solutions, and outline possible improvements. Specifically, we propose several schemes on how to tackle various issues such as authentication, privacy, transparency, scalability, safety, as well as several other practical aspects of the platform. Most importantly, a blockchain-based voting system needs to ensure that the prospect of tampering with the election result is to a large extent eliminated. At the same time, the voting platform should have proper performance characteristics, i.e. sufficient throughput, for a voting of large magnitude such as a presidential election. Being heavily linked together, security and performance should be investigated in a unified framework to capture the interaction effects between the two. To address this concern, for the first time, we will study the performance and security implications of the blockchain voting system in a quantitative manner, using a blockchain simulator developed by researchers at Swiss Federal Institute of Technology, ETH Zurich. In our analysis, we will specifically investigate the stale block rate and relative mining share of the dishonest network, as the central security measures, as a function of important network parameters that determine the throughput of the network, i.e. block size and block interval. Ultimately, we focus on selfish mining and eclipse attacks as the most critical threats to the integrity of the blockchain voting in order to find the optimal network parameters

On the Security and Performance of Proof of Work Blockchains

Proof of Work (PoW) powered blockchains currently account for more than 90% of the total market capitalization of existing digital currencies. Although the security provisions of Bitcoin have been thoroughly analysed, the security guarantees of variant (forked) PoW blockchains (which were instantiated with different parameters) have not received much attention in the literature. In this paper, we introduce a novel quantitative framework to analyse the security and performance implications of various consensus and network parameters of PoW blockchains. Based on our framework, we devise optimal adversarial strategies for double-spending and selfish mining while taking into account real world constraints such as network propagation, different block sizes, block generation intervals, information propagation mechanism, and the impact of eclipse attacks. Our framework therefore allows us to capture existing PoW-based deployments as well as PoW blockchain variants that are instantiated with different parameters, and to objectively compare the tradeoffs between their performance and security provisions

Greedy-Mine: A Profitable Mining Attack Strategy in Bitcoin-NG

Bitcoin-NG is an extensible blockchain protocol based on the same trust model as Bitcoin. It divides each epoch into one Key-Block and multiple Micro-Blocks, effectively improving transaction processing capacity. Bitcoin-NG adopts a special incentive mechanism (i.e., the transaction fees in each epoch are split to the current and next leader) to maintain its security. However, there are some limitations to the existing incentive analysis of Bitcoin-NG in recent works. First, the incentive division method of Bitcoin-NG only includes some specific mining attack strategies of adversary, while ignoring more stubborn attack strategies. Second, once adversaries find a whale transaction, they will deviate from honest mining strategy to obtain extra reward. In this paper, we are committed to solving these two limitations. First, we propose a novel mining strategy named Greedy-Mine attack. Then, we formulate a Markov Decision Process (MDP) model to analyze the competition of honest miners and adversaries. Furthermore, we analysis the extra reward of adversaries and summarize the mining power proportion range required for malicious adversaries to launch Greedy-Mine to obtain extra returns. Finally, we make a backward-compatibility progressive modification to Bitcoin-NG protocol that would raise the threshold of propagation factor from 0 to 1. Meanwhile, we get the winning condition of adversaries when adopting Greedy-Mine, compared with honest mining. Simulation and experimental results indicate that Bitcoin-NG is not incentive compatible, which is vulnerable to Greedy-Mine attack.Comment: 20 pages, 12 figur

A Survey on Consensus Mechanisms and Mining Strategy Management in Blockchain Networks

© 2013 IEEE. The past decade has witnessed the rapid evolution in blockchain technologies, which has attracted tremendous interests from both the research communities and industries. The blockchain network was originated from the Internet financial sector as a decentralized, immutable ledger system for transactional data ordering. Nowadays, it is envisioned as a powerful backbone/framework for decentralized data processing and data-driven self-organization in flat, open-access networks. In particular, the plausible characteristics of decentralization, immutability, and self-organization are primarily owing to the unique decentralized consensus mechanisms introduced by blockchain networks. This survey is motivated by the lack of a comprehensive literature review on the development of decentralized consensus mechanisms in blockchain networks. In this paper, we provide a systematic vision of the organization of blockchain networks. By emphasizing the unique characteristics of decentralized consensus in blockchain networks, our in-depth review of the state-of-the-art consensus protocols is focused on both the perspective of distributed consensus system design and the perspective of incentive mechanism design. From a game-theoretic point of view, we also provide a thorough review of the strategy adopted for self-organization by the individual nodes in the blockchain backbone networks. Consequently, we provide a comprehensive survey of the emerging applications of blockchain networks in a broad area of telecommunication. We highlight our special interest in how the consensus mechanisms impact these applications. Finally, we discuss several open issues in the protocol design for blockchain consensus and the related potential research directions