A cryptocurrency mixer (also known a "tumbler") is a web-based service that is used to effectively launder digital assets by taking the data from transactions made on a blockchain and combining them in a group of other transactions of the same value. For example: if someone wanted to use a mixer to hide the fact that they received 1 bitcoin (BTC) through transactions amounting to 0.5 BTC, 0.3 BTC, and 0.2 BTC respectively, they could withdraw the sum of these transactions through a mixer, which scatters the data in a basket of similar data, making the transaction hard to track. In this hypothetical example, had the user withdrawn the 1 BTC directly to the address in her wallet, this action would cause data to be entered onto the blockchain that would enable her transactions to be traced - eventually, to her identity - as law enforcement agencies around the world have done in many cases of criminal investigation.
In May 2019, the Dutch Digital Intrusion Team (DIGIT), Europol, and authorities from Luxembourg, France, and Latvia shut down a mixer called Bestmixer.io, one of the larget of such services in the world. At the time, it was believed that Bestmixer.io had performed its services on over $200 million worth of digital assets since it had been in operation.
- Cryptocurrency Mixers and Why Governments May Want to Shut Them Down. Cointelegraph.
- $200M cryptocurrency mixing operation dismantled by Eurocops. The Next Web.