Tracking Mixed Bitcoins
This addresses the challenge of cryptocurrency traceability for law enforcement and security analysts, though it is incremental as it adapts existing techniques.
The paper tackles the problem of tracking Bitcoins after they pass through mixer services, which aim to break transaction links, and shows that their novel address taint analysis method can track mixed Bitcoins and reduce false positives with filtering criteria.
Mixer services purportedly remove all connections between the input (deposited) Bitcoins and the output (withdrawn) mixed Bitcoins, seemingly rendering taint analysis tracking ineffectual. In this paper, we introduce and explore a novel tracking strategy, called \emph{Address Taint Analysis}, that adapts from existing transaction-based taint analysis techniques for tracking Bitcoins that have passed through a mixer service. We also investigate the potential of combining address taint analysis with address clustering and backward tainting. We further introduce a set of filtering criteria that reduce the number of false-positive results based on the characteristics of withdrawn transactions and evaluate our solution with verifiable mixing transactions of nine mixer services from previous reverse-engineering studies. Our finding shows that it is possible to track the mixed Bitcoins from the deposited Bitcoins using address taint analysis and the number of potential transaction outputs can be significantly reduced with the filtering criteria.