Mixers & Tumblers
Services that obscure the on-chain link between source and destination of cryptocurrency - heavily used in laundering, ransomware and sanctions evasion.
Definition
Mixers (also called tumblers) are services that pool incoming transactions from many users and redistribute equivalent amounts to chosen output addresses, breaking the on-chain link between source and destination. Technical implementations range from custodial mixers (centralised, easy to subpoena) to non-custodial smart-contract mixers (Tornado Cash) and CoinJoin coordinators (Wasabi, Whirlpool).
Why they matter to compliance
Mixer exposure is one of the strongest signals in on-chain risk scoring. FATF guidance classifies mixers as "higher risk" per se. OFAC has sanctioned multiple mixer protocols including Tornado Cash (2022), Blender (2022) and Sinbad (2023), making any direct or indirect exposure to those addresses a sanctions-screening trigger.
Regulatory anchor
EU AMLR explicitly identifies anonymity-enhancing services as a high-risk indicator. FATF Updated Guidance (2021/2023) recommends a risk-based approach to mixer-exposed transactions. OFAC SDN listings of specific mixer addresses convert exposure into a strict-liability sanctions issue for any US-touching counterparty.
Detection approach
- Direct exposure: address interacted with a known mixer contract / address.
- Indirect exposure: address received funds within N hops from a mixer output.
- Statistical exposure: address shows CoinJoin behavioural signatures (equal-output transactions, multi-input).