Cryptocurrency Mixer

A cryptocurrency mixer (also known as a tumbler) refers to a service that can increase the anonymity of certain cryptocurrency transactions. A mixer acts as a type of middleman that mixes together cryptocurrencies from different sources before returning other cryptocurrencies (of the same type, but with different unique blockchain identifiers) to those sources. There are two types of cryptocurrency mixers: centralized mixers (companies that operate the black box mixer and earn fees by matching/swapping cryptocurrencies) and decentralized mixers (protocols that allow a large group of users to pool cryptocurrencies for redistribution).
Cryptocurrency mixing services have been criticized as facilitators of criminal activity, such as money laundering, and are illegal in some jurisdictions.