Mixers and Tornado Cash

Mixers — also called tumblers — pool deposits from many users and let withdrawers receive funds that are not trivially linked to their deposits. On Ethereum, Tornado Cash became the best-known example: fixed denomination pools for 0.1, 1, or 10 ETH where users proved withdrawal rights with zero-knowledge notes without revealing which deposit they owned.

Mixers do not create perfect privacy. Timing correlation, unique deposit amounts in variable pools, and graph analysis can shrink the anonymity set. Small pools with few participants offer weak protection regardless of the cryptography.

Regulators treat mixers as high-risk infrastructure because they can obscure proceeds of crime alongside legitimate privacy use. Understanding mixer mechanics is essential context for privacy pools, compliance tooling, and why Ethereum-native privacy moved toward association-set designs after Tornado Cash sanctions.