A Security Study in Decentralized Applications of Ethereum Blockchain

Abstract

The proposal of the first cryptocurrency Bitcoin brings about the new technology called blockchain that massively expands the concept of financial system.Tamper-resistance, decentralization and traceability are three essential properties of a blockchain.In the following years, the original idea of blockchain also inspired the development and research of other cryptocurrency implementations.And the development of blockchain has extended beyond its fundamental transactional attributes.As blockchain can be regarded as an immutable ledger, it can also be exploited in other application scenarios.Ethereum, based on the principles of blockchain, further introduced smart contract technology, allowing any blockchain user to deploy programs on the chain for others to invoke.This has given rise to decentralized applications.Due to the distinct network model of decentralized applications, existing studies regarding the security of centralized models are difficult to directly adapt to decentralized blockchain applications.Therefore, safeguarding information security and user privacy in the blockchain environment has become a focal point of security study.The thesis contains three studies regarding security of decentralized applications.They are primarily categorized into two types according to the scenarios.One type involves using blockchain to enhance existing applications, while the other focuses on native applications based on blockchain.In the first scenario, I utilize blockchain to provide a verifiable endorsement solution for identity authentication in social networking service (SNS) scenarios.Previous identity authentication research in this area rarely incorporated blockchain.I significantly enhance the reliability and efficiency of identity authentication while preventing impersonation using blockchain.In the second scenario, our focus is on NFT trading within the blockchain.Existing research has only addressed NFT privacy issues to a limited extent due to conflicts with Ethereum's transparency principle.To tackle this problem, I proposed two solutions: first, I make the marketplace a semi-trusted entity to achieve anonymous NFT trading.Then, based on previous research, I further propose a solution for anonymous NFT transactions in a trustless environment.Through security analysis and performance evaluation, our solutions meet security requirements with acceptable expenses, making them suitable for practical applications.