Pinpointing and Measuring Wasabi and Samourai CoinJoins in the Bitcoin Ecosystem

We present a first measurement study on two popular wallets with built-in distributed CoinJoin functionality, Wasabi and Samourai, in the context of the broader Bitcoin ecosystem. By applying two novel heuristics, we can effectively pinpoint 25,070 Wasabi and 134,569 Samourai transactions within the first 689,255 (2021-07-01) blocks. Our study reveals a somewhat steady adoption of these services and found a growing trend with a total amount of 190,777.11 mixed BTC with a value of ca. 3.02 B USD. Within the recent six months, we measured an average monthly mixing throughput of 5410.98 BTC (ca. 240.14 M USD). Among all actors, which were directly or indirectly involved in CoinJoins, we also found a lower-bound of 32 distinct exchanges and traced a lower-bound of 6683.19 BTC (ca. 95.98 M USD) mixed coins received by exchanges. Our analysis further shows that linking heuristics over Wasabi and Samourai transactions allows us to narrow down the anonymity set provided by these wallets over time. Furthermore, we estimate the number of mixing outputs that are handled in Wasabi and Samourai correspondingly over time. Overall, this is the first paper to provide a comprehensive picture of the adoption of distributed CoinJoin and to discuss implications for end-users, cryptoasset exchanges, and regulatory bodies.