Cryptocurrency mixers and tumblers (Tornado Cash, Blender.io)

Cryptocurrency mixers and tumblers are services or software intended to weaken the public link between the source and destination of digital assets. Their architectures differ. A custodial mixer receives and controls customer funds before returning other assets. A smart-contract system can execute deposits and withdrawals through code, while interfaces, relayers, developers, governance participants and users retain separate roles. Those differences determine where sanctions and criminal law can attach.

Function and control points

A mixer combines transactions, delays transfers, changes output amounts or uses cryptographic proofs to make tracing more difficult. Tornado Cash used zero-knowledge proofs on Ethereum. Some core contracts became immutable after deployment, meaning no administrator could alter or withdraw the deposited assets through a conventional ownership right. That did not make every component decentralised or every user anonymous. Web interfaces, hosting, relayers, exchanges and identifiable proceeds remained potential control points.

Mixers have lawful privacy uses, including reducing public exposure of personal holdings and donations. They are also used to launder theft, fraud and ransomware proceeds. Transaction tracing can still use timing, amount, reuse of addresses, off-chain evidence and exchange records. A mixer complicates attribution; it does not guarantee it.

Sanctions and criminal cases

The United States designated the custodial mixer Blender.io on 6 May 2022, alleging that it supported laundering by North Korea's Lazarus Group. Treasury designated Tornado Cash on 8 August 2022 and redesignated it on 8 November 2022. The August release said more than US$7bn had moved through the service since 2019, including about US$455m attributed to the Lazarus Group. That figure was Treasury's description of total value moved, not a judicial finding that every transaction was illicit.

In Van Loon v Department of the Treasury, the Fifth Circuit held on 26 November 2024 that the immutable smart contracts in the administrative record were not 'property' or an 'interest in property' under the relevant blocking authority. The judgment did not immunise mixers, developers, interfaces or users from other laws. The Office of Foreign Assets Control removed Tornado Cash from the sanctions list on 21 March 2025.

A separate prosecution produced a narrower criminal result. On 6 August 2025, a federal jury convicted co-founder Roman Storm of conspiracy to operate an unlicensed money-transmitting business. The jury did not return verdicts on the other charged conspiracies. Storm's Rule 29 motion remained pending in the cited court record on 16 June 2026, and a retrial on unresolved counts was set for 26 October 2026 contingent on that ruling. No final sentence or appeal outcome is stated here as at 30 July 2026.

The United States charged alleged operators of Blender.io and Sinbad.io in January 2025. Those charges are allegations, and the defendants are presumed innocent unless proved guilty.

Statecraft significance

The cases show that 'the mixer' is not one object. Property blocking worked differently against a custodial business and immutable code. Delisting ended the Tornado Cash administrative blocking action, but it did not decide criminal liability. Effective policy identifies the legal person, asset, contract, interface or transaction being regulated, then measures whether activity moved to other protocols, privacy coins, bridges or exchanges.

See also

United States designation and delisting of Tornado Cash (2022-2025) · Van Loon v Department of the Treasury (Fifth Circuit, 2024) · North Korean cryptocurrency theft campaign (2017-present) · Lazarus Group · Blockchain analytics platforms (Chainalysis, Elliptic, TRM) · Privacy coins (Monero, Zcash) · Crypto exchanges as chokepoints (fiat on/off-ramps)

Sources

1. United States Department of the Treasury, Treasury sanctions virtual-currency mixer Blender.io (6 May 2022).
2. United States Department of the Treasury, Treasury sanctions virtual-currency mixer Tornado Cash (8 August 2022).
3. United States Court of Appeals for the Fifth Circuit, *Van Loon v Department of the Treasury*, No. 23-50669 (26 November 2024).
4. Office of Foreign Assets Control, Tornado Cash delisting record (21 March 2025).
5. United States Attorney's Office for the Southern District of New York, Tornado Cash founder convicted on unlicensed money-transmitting count (6 August 2025).
6. United States Department of Justice, Operators of cryptocurrency mixers charged with money laundering (10 January 2025).
7. United States District Court for the Southern District of New York, order setting a contingent retrial (24 April 2026), and pretrial scheduling order (16 June 2026).