Year

2021

Degree Name

Doctor of Philosophy

Department

School of Computing and Information Technology

Abstract

Blockchain, one of the most disruptive technologies in this century, has gained extensive attention in both academia and industry. Blockchain is a technological innovation and global platform that brings a new paradigm for business. Blockchain has a number of features that previous systems do not have, such as it is decentralised, distributed, immutable and publicly accessible. As a result, blockchain has many potentials to address some stumbling block security weaknesses in concrete applications, such as manufacturing, finance and the government sector. However, by merely replacing the databases or public ledgers of existing systems with the blockchain will not solve the problem since this approach may reduce the efficiency dramatically and brings new security issues in the systems. Thus, to find more “killer” applications of blockchain besides cryptocurrencies and build practical security protocols atop blockchain remains a challenging research topic.

In this thesis, we aim to find applications of blockchain by carrying out the study on blockchain-based security protocols. That is, we focus on the issues of the surveil- lance of cryptocurrencies, decentralised e-voting, contractual equivocation and stateless blockchain. To be more specific, we make the following contributions in this thesis.

First, we introduce a new cryptocurrency named Traceable Monero to balance user anonymity and accountability. In Traceable Monero, normal transactions can still be conducted anonymously as in the Monero system except that there exists a tracing authority who is able to revoke a payer’s anonymity due to his/her misbehaviour. Our proposed framework is optimistic, in that the tracing authority is only involved when investigations in certain transactions are required. We formalise the system model and security model of Traceable Monero and present a detailed construction of Traceable Monero by overlaying Monero with two types of tracing mechanisms, tracing the one-time addresses with money flows and tracing the long-term addresses. We prove the security of Traceable Monero and implement a prototype of the system, which demonstrates that Traceable Monero incurs merely a very small overhead in generating and verifying a transaction compared to Monero transactions.

FoR codes (2008)

0899 OTHER INFORMATION AND COMPUTING SCIENCES

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.