Evaluating the Practical Privacy of Whirlpool Coinjoins

Bitcoin is the leading public permissionless digital currency. Bitcoin uses a public ledger to achieve strong security properties and double-spending resistance. However, this public ledger also poses challenges for user privacy despite Bitcoin's pseudonymity. Our research aims to evaluate the real-world privacy capabilities of Bitcoin’s privacy solutions, focusing on the popular CoinJoin mixing technique, which combines multiple independent users’ transactions into a single transaction and thus limits the traceability of funds from source to destination. In this project we focus specifically on the Whirlpool CoinJoin protocol (used in Samourai Wallet) and will analyze on-chain data to evaluate prevalence of specific privacy-damaging user behaviors, such as linking change outputs with CoinJoin outputs, and estimate their effect on user's privacy.