Author: Dominik Hluštík
Supervisor: Petr Švenda
Abstract: In today’s digital age, where privacy and security for financial transactions on the blockchain are of great concern, many new anonymization products have been introduced to tackle this problem. CoinJoin is one of them. The theoretical part of the thesis focuses on the implementation of the Whirlpool protocol, a specific implementation of CoinJoin developed by a group of developers called Samourai. The theoretical part explains the protocol’s inner workings and the privacy guarantees it provides. In the practical part of the thesis, a simulation apparatus was developed to execute CoinJoin mixing simulations repeatedly, allowing for testing and data collection. Using the collected data, the final part of the thesis analyzes the anonymity achieved by using Whirlpool. Anonymity was measured by a new method of pairing inputs and outputs of a CoinJoin transaction based on IP addresses, revealing potential weaknesses in maintaining user privacy from the Coordinator’s side.