Tornado Cash is a non-custodial Ethereum and ERC20 privacy solution based on zkSNARKs. It improves transaction privacy by breaking the on-chain link between recipient and destination addresses. It uses a smart contract that accepts ETH deposits that can be withdrawn by a different address. Whenever ETH is withdrawn by the new address, there is no way to link the withdrawal to the deposit, ensuring complete privacy.
To make a deposit user generates a secret and sends its hash (called a commitment) along with the deposit amount to the Tornado smart contract. The contract accepts the deposit and adds the commitment to its list of deposits.
Later, the user decides to make a withdrawal. In order to do that, the user should provide a proof that he or she possesses a secret to an unspent commitment from the smart contract’s list of deposits. zkSnark technology allows that to happen without revealing which exact deposit corresponds to this secret. The smart contract will check the proof, and transfer deposited funds to the address specified for withdrawal. An external observer will be unable to determine which deposit this withdrawal came from.
You can read more about it in this medium article
- Deposit gas const: 1088354 (43381 + 50859 * tree_depth)
- Withdraw gas cost: 301233
- Circuit Constraints = 28271 (1869 + 1325 * tree_depth)
- Circuit Proof time = 10213ms (1071 + 347 * tree_depth)
- Serverless
TornadoCash_whitepaper_v1.4.pdf
Tornado.cash protocols, circuits, and smart contracts were audited by a group of experts from ABDK Consulting, specializing in zero knowledge, cryptography, and smart contracts.
During the audit no critical issues were found and all outstanding issues were fixed. The results can be found here:
- Cryptographic review https://tornado.cash/audits/TornadoCash_cryptographic_review_ABDK.pdf
- Smart contract audit https://tornado.cash/audits/TornadoCash_contract_audit_ABDK.pdf
- Zk-SNARK circuits audit https://tornado.cash/audits/TornadoCash_circuit_audit_ABDK.pdf
Underlying circomlib dependency is currently being audited, and the team already published most of the fixes for found issues
node v11.15.0npm install -g npx
You can see example usage in cli.js, it works both in console and in browser.
npm installcp .env.example .envnpm run build- this may take 10 minutes or morenpx ganache-clinpm run test- optionally runs tests. It may fail on the first try, just run it again.
Use browser version on Kovan:
vi .env- add your Kovan private key to deploy contractsnpm run migratenpx http-server- serve current dir, you can use any other static http server- Open
localhost:8080
Use with command line version. Works for Ganache, Kovan and Mainnet:
cp .env.example .envnpm run downloadnpm run build:contract
- make sure you complete steps from Initialization
ganache-cli -i 1337npm run migrate:dev./cli.js test./cli.js --help
- Please use https://github.com/tornadocash/tornado-cli
Reason: because tornado-core uses websnark
2041cfa5fa0b71cd5cca9022a4eeea4afe28c9f7commit hash in order to work with local trusted setup. Tornado-cli uses4c0af6a8b65aabea3c09f377f63c44e7a58afa6dcommit with production trusted setup of tornadoCash
Example:
./cli.js deposit ETH 0.1 --rpc https://kovan.infura.io/v3/27a9649f826b4e31a83e07ae09a87448Your note: tornado-eth-0.1-42-0xf73dd6833ccbcc046c44228c8e2aa312bf49e08389dadc7c65e6a73239867b7ef49c705c4db227e2fadd8489a494b6880bdcb6016047e019d1abec1c7652 Tornado ETH balance is 8.9 Sender account ETH balance is 1004873.470619891361352542 Submitting deposit transaction Tornado ETH balance is 9 Sender account ETH balance is 1004873.361652048361352542
./cli.js withdraw tornado-eth-0.1-42-0xf73dd6833ccbcc046c44228c8e2aa312bf49e08389dadc7c65e6a73239867b7ef49c705c4db227e2fadd8489a494b6880bdcb6016047e019d1abec1c7652 0x8589427373D6D84E98730D7795D8f6f8731FDA16 --rpc https://kovan.infura.io/v3/27a9649f826b4e31a83e07ae09a87448 --relayer https://kovan-frelay.duckdns.orgRelay address: 0x6A31736e7490AbE5D5676be059DFf064AB4aC754 Getting current state from tornado contract Generating SNARK proof Proof time: 9117.051ms Sending withdraw transaction through relay Transaction submitted through the relay. View transaction on etherscan https://kovan.etherscan.io/tx/0xcb21ae8cad723818c6bc7273e83e00c8393fcdbe74802ce5d562acad691a2a7b Transaction mined in block 17036120 Done
cp .env.example .env- Tune all necessary params
npx truffle migrate --network kovan --reset --f 2 --to 4
cp .env.example .env- Tune all necessary params
npx truffle migrate --network kovan --reset --f 2 --to 3npx truffle migrate --network kovan --reset --f 5
Note. If you want to reuse the same verifier for all the instances, then after you deployed one of the instances you should only run 4th or 5th migration for ETH or ERC20 contracts respectively (--f 4 --to 4 or --f 5).
- Visit https://etherscan.io/enslookup and put relayer ENS name to the form.
- Copy the namehash (1) and click on the
Resolverlink (2) - Go to
Contracttab. Click onRead Contractand scrolldown to the5. textmethod. - Put the values:
- Click
Queryand you will get the DNS name. Just addhttps://to it and use it asrelayer url
Special thanks to @barryWhiteHat and @kobigurk for valuable input, and to @jbaylina for awesome Circom & Websnark framework
npm iganache-cli -dnpm run downloadnpm run build:contractcp .env.example .envnpm run migrate:devnode minimal-demo.js
cargo install zkutil
npx circom circuits/withdraw.circom -o build/circuits/withdraw.json
zkutil setup -c build/circuits/withdraw.json -p build/circuits/withdraw.params
zkutil export-keys -c build/circuits/withdraw.json -p build/circuits/withdraw.params -r build/circuits/withdraw_proving_key.json -v build/circuits/withdraw_verification_key.json
zkutil generate-verifier -p build/circuits/withdraw.params -v build/circuits/Verifier.sol
sed -i -e 's/pragma solidity \^0.6.0/pragma solidity 0.5.17/g' ./build/circuits/Verifier.sol