What is a cryptocurrency mixer and how does it work?

The rapid expansion of cryptocurrencies and the development of crypto infrastructure and vulnerabilities like crypto mixers or tumblers have been a source of concern for government agencies in charge of financial security.

Many people use crypto mixers to keep their cryptocurrency transactions private by mixing potentially identifiable cryptocurrency funds with vast sums of other funds. These services are often used to anonymize fund transfers between services and do not require Know Your Customer (KYC) checks.

As a result, the risk of employing crypto mixers to launder money or conceal earnings is pretty considerable. Mixers and online gambling sites have the most severe money laundering issues, as they process the vast majority of dirty currencies. Mixers, for example, have consistently processed about a quarter of all incoming illicit Bitcoin (BTC) each year, while the proportion laundered through exchanges and gambling has remained relatively steady (66 to 72%).

There are two types of Bitcoin mixers: namely centralized and decentralized mixers. Companies that receive Bitcoin and send back different BTC for a fee are known as centralized mixers, providing a simple solution for tumbling Bitcoin. 

Decentralized mixers use protocols like CoinJoin to obfuscate transactions using either a completely coordinated or peer-to-peer (P2P) approach. Essentially, the protocol allows a big group of users to pool an amount of BTC and then redistribute it such that everyone receives one Bitcoin. Still, no one can know who received what or where it originated from.

Other types of coin mixers include obfuscation-based and zero-knowledge-based mixers. Obfuscation-based mixers, often called decoy-based mixers, employ ways to conceal a user’s transaction graph. An adversary with sufficient resources, on the other hand, can recreate the transaction graph using a variety of ways. 

On the contrary, zero-knowledge-based mixers rely heavily on advanced cryptographic techniques like zero-knowledge proofs to fully erase the transaction graph. The most significant disadvantage of this strategy is that it necessitates extensive cryptography, which may limit scalability.