What is Tornado Cash?
A decentralized cryptocurrency mixing protocol on Ethereum that was sanctioned by the US Treasury in August 2022 — the first time the US government sanctioned a piece of open-source software rather than a person or entity, raising fundamental questions about code as speech.
Also known as: Tornado Cash Sanctions, Tornado Cash Ban
The Tornado Cash sanctions represent the most aggressive government action against financial privacy technology — and set a precedent that writing and publishing code can be treated as a sanctionable offense.
What Tornado Cash Did
- Smart contract on Ethereum that broke the link between sender and receiver of crypto transactions
- Users deposited ETH or ERC-20 tokens, received a "note" (cryptographic proof), and could withdraw later from a different address
- Used zero-knowledge proofs to verify withdrawals without revealing which deposit they correspond to
- Made Ethereum transactions private — something the public blockchain doesn't provide by default
- Used by both privacy-seekers and, in some cases, by hackers laundering stolen funds
The Sanctions
August 8, 2022
- US Treasury's OFAC (Office of Foreign Assets Control) added Tornado Cash to the Specially Designated Nationals (SDN) list
- First time a neutral software tool (rather than a person or entity) was sanctioned
- All US persons prohibited from interacting with Tornado Cash smart contracts
- GitHub deleted the Tornado Cash repository and banned contributor accounts
The Arrest
- Alexey Pertsev, one of Tornado Cash's developers, was arrested in the Netherlands in August 2022
- Convicted of money laundering in May 2024 and sentenced to 64 months in prison
- Convicted for writing code that others used for illicit purposes
Legal Challenge
- Coin Center and six individuals challenged the sanctions in court
- In November 2024, a federal appeals court ruled that immutable smart contracts are not "property" that can be sanctioned under IEEPA
- The legal battle continues but the ruling was a significant win for code-as-speech arguments
Why It Matters
Code as Speech
If developers can be sanctioned or arrested for writing open-source software, it creates a chilling effect on all privacy technology development. By this logic, Tor developers, VPN creators, and encryption implementers could face similar treatment.
Privacy Is Not a Crime
The majority of Tornado Cash users were seeking ordinary financial privacy — the same kind banks provide by default. Using a privacy tool does not imply criminal activity.
Precedent for Privacy Coins
If the US government can sanction a mixing protocol, it can potentially sanction privacy coins (Monero, DERO, Zcash) or any technology that provides financial privacy.
The Financial Privacy Tension
Tornado Cash highlights the fundamental conflict between:
- Government's interest in tracking financial transactions (anti-money laundering, sanctions enforcement)
- Individual's right to financial privacy (a basic aspect of personal freedom)
- Developer freedom to write and publish code (First Amendment / free expression)
Related Terms
CoinJoin
A Bitcoin privacy technique that combines multiple users' transactions into a single transaction, making it difficult to determine which inputs correspond to which outputs.
DERO
A privacy-focused blockchain platform that uses homomorphic encryption for fully encrypted transactions and supports private smart contracts.
Mixer / Tumbler
A service that pools cryptocurrency from multiple users and redistributes it, breaking the link between the original sender and the final recipient.
Monero
The most widely-used privacy cryptocurrency, using ring signatures, stealth addresses, and RingCT to make transactions untraceable by default.
Privacy Coin
A cryptocurrency designed with built-in privacy features that hide transaction amounts, sender and receiver addresses, or both.
Sanctions Compliance & Crypto
The growing intersection of financial sanctions enforcement and cryptocurrency — where governments use OFAC sanctions, exchange regulations, and blockchain surveillance to extend traditional financial controls to digital assets, often at the expense of legitimate privacy.
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