64 lines
2.3 KiB
Solidity
64 lines
2.3 KiB
Solidity
pragma solidity ^0.5.8;
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import "./MerkleTreeWithHistory.sol";
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contract IVerifier {
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function verify(uint256[2] memory a, uint256[2][2] memory b, uint256[2] memory c, uint256[4] memory input) public returns(bool);
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}
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contract Mixer is MerkleTreeWithHistory {
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uint256 public transferValue;
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mapping(uint256 => bool) public nullifiers;
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IVerifier verifier;
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event Deposit(address from, uint256 commitment);
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event Withdraw(address to, uint256 nullifier, uint256 fee);
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/**
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@dev The constructor
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@param _verifier the address of SNARK verifier for this contract
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@param _transferValue the value for all deposits in this contract in wei
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*/
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constructor(address _verifier, uint256 _transferValue) MerkleTreeWithHistory(16, 0) public {
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verifier = IVerifier(_verifier);
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transferValue = _transferValue;
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}
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/**
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@dev Deposit funds into mixer. The caller must send value equal to `transferValue` of this mixer.
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@param commitment the note commitment, which is PedersenHash(nullifier + secret)
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*/
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function deposit(uint256 commitment) public payable {
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require(msg.value == transferValue, "Please send `transferValue` ETH along with transaction");
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_insert(commitment);
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emit Deposit(msg.sender, commitment);
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}
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/**
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@dev Withdraw deposit from the mixer. `a`, `b`, and `c` are zkSNARK proof data, and input is an array of circuit public inputs
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`input` array consists of:
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- merkle root of all deposits in the mixer
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- unique deposit nullifier to prevent double spends
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- the receiver of funds
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- optional fee that goes to the transaction sender (usually a relay)
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*/
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function withdraw(uint256[2] memory a, uint256[2][2] memory b, uint256[2] memory c, uint256[4] memory input) public {
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uint256 root = input[0];
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uint256 nullifier = input[1];
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address payable receiver = address(input[2]);
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uint256 fee = input[3];
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require(fee < transferValue, "Fee exceeds transfer value");
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require(!nullifiers[nullifier], "The note has been already spent");
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require(isKnownRoot(root), "Cannot find your merkle root"); // Make sure to use a recent one
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require(verifier.verify(a, b, c, input), "Invalid withdraw proof");
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nullifiers[nullifier] = true;
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receiver.transfer(transferValue - fee);
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if (fee > 0) {
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msg.sender.transfer(fee);
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}
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emit Withdraw(receiver, nullifier, fee);
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}
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}
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