docs and minor changes

This commit is contained in:
poma 2019-07-10 15:35:46 +03:00
parent 5db6595c61
commit 9d75637b8c
5 changed files with 37 additions and 14 deletions

2
.gitignore vendored
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@ -1,3 +1,5 @@
circuits/build
# Created by .ignore support plugin (hsz.mobi) # Created by .ignore support plugin (hsz.mobi)
### Node template ### Node template
# Logs # Logs

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@ -1,6 +1,7 @@
include "../node_modules/circomlib/circuits/bitify.circom"; include "../node_modules/circomlib/circuits/bitify.circom";
include "../node_modules/circomlib/circuits/mimcsponge.circom"; include "../node_modules/circomlib/circuits/mimcsponge.circom";
// Computes MiMC(left + right)
template HashLeftRight(rounds) { template HashLeftRight(rounds) {
signal input left; signal input left;
signal input right; signal input right;
@ -15,6 +16,8 @@ template HashLeftRight(rounds) {
hash <== hasher.outs[0]; hash <== hasher.outs[0];
} }
// if pathIndex == 0 returns (left = inputElement, right = pathElement)
// if pathIndex == 1 returns (left = pathElement, right = inputElement)
template Selector() { template Selector() {
signal input inputElement; signal input inputElement;
signal input pathElement; signal input pathElement;
@ -39,13 +42,14 @@ template Selector() {
right <== rightSelector1 + rightSelector2; right <== rightSelector1 + rightSelector2;
} }
// Verifies that merkle proof is correct for given merkle root and a leaf
// pathIndex input is an array of 0/1 selectors telling whether given pathElement is on the left or right side of merkle path
template MerkleTree(levels, rounds) { template MerkleTree(levels, rounds) {
signal input leaf; signal input leaf;
signal input root;
signal private input pathElements[levels]; signal private input pathElements[levels];
signal private input pathIndex[levels]; signal private input pathIndex[levels];
signal output root;
component selectors[levels]; component selectors[levels];
component hashers[levels]; component hashers[levels];
@ -66,5 +70,5 @@ template MerkleTree(levels, rounds) {
selectors[i].inputElement <== hashers[i-1].hash; selectors[i].inputElement <== hashers[i-1].hash;
} }
root <== hashers[levels - 1].hash; root === hashers[levels - 1].hash;
} }

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@ -2,6 +2,7 @@ include "../node_modules/circomlib/circuits/bitify.circom";
include "../node_modules/circomlib/circuits/pedersen.circom"; include "../node_modules/circomlib/circuits/pedersen.circom";
include "merkleTree.circom"; include "merkleTree.circom";
// computes Pedersen(nullifier + secret)
template CommitmentHasher() { template CommitmentHasher() {
signal input nullifier; signal input nullifier;
signal private input secret; signal private input secret;
@ -21,6 +22,7 @@ template CommitmentHasher() {
hash <== commitment.out[0]; hash <== commitment.out[0];
} }
// Verifies that commitment that corresponds to given secret and nullifier is included in the merkle tree of deposits
template Withdraw(levels, rounds) { template Withdraw(levels, rounds) {
signal input root; signal input root;
signal input nullifier; signal input nullifier;
@ -36,10 +38,11 @@ template Withdraw(levels, rounds) {
component tree = MerkleTree(levels, rounds); component tree = MerkleTree(levels, rounds);
tree.leaf <== hasher.hash; tree.leaf <== hasher.hash;
tree.pathElements <== pathElements; tree.root <== root;
tree.pathIndex <== pathIndex; for (var i = 0; i < levels; i++) {
tree.pathElements[i] <== pathElements[i];
root === tree.root; tree.pathIndex[i] <== pathIndex[i];
}
// TODO: Check if we need some kind of explicit constraints or something // TODO: Check if we need some kind of explicit constraints or something
fee === fee; fee === fee;

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@ -25,15 +25,15 @@ contract MerkleTreeWithHistory {
filled_subtrees.push(zeros[0]); filled_subtrees.push(zeros[0]);
for (uint8 i = 1; i < levels; i++) { for (uint8 i = 1; i < levels; i++) {
zeros.push(HashLeftRight(zeros[i-1], zeros[i-1])); zeros.push(hashLeftRight(zeros[i-1], zeros[i-1]));
filled_subtrees.push(zeros[i]); filled_subtrees.push(zeros[i]);
} }
roots = new uint256[](ROOT_HISTORY_SIZE); roots = new uint256[](ROOT_HISTORY_SIZE);
roots[0] = HashLeftRight(zeros[levels - 1], zeros[levels - 1]); roots[0] = hashLeftRight(zeros[levels - 1], zeros[levels - 1]);
} }
function HashLeftRight(uint256 left, uint256 right) public pure returns (uint256 mimc_hash) { function hashLeftRight(uint256 left, uint256 right) public pure returns (uint256 mimc_hash) {
uint256 k = 21888242871839275222246405745257275088548364400416034343698204186575808495617; uint256 k = 21888242871839275222246405745257275088548364400416034343698204186575808495617;
uint256 R = 0; uint256 R = 0;
uint256 C = 0; uint256 C = 0;
@ -67,7 +67,7 @@ contract MerkleTreeWithHistory {
right = current_level_hash; right = current_level_hash;
} }
current_level_hash = HashLeftRight(left, right); current_level_hash = hashLeftRight(left, right);
current_index /= 2; current_index /= 2;
} }

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@ -1,15 +1,12 @@
pragma solidity ^0.5.8; pragma solidity ^0.5.8;
import "./MerkleTreeWithHistory.sol"; import "./MerkleTreeWithHistory.sol";
import "../node_modules/openzeppelin-solidity/contracts/math/SafeMath.sol";
contract IVerifier { contract IVerifier {
function verify(uint256[2] memory a, uint256[2][2] memory b, uint256[2] memory c, uint256[4] memory input) public returns(bool); function verify(uint256[2] memory a, uint256[2][2] memory b, uint256[2] memory c, uint256[4] memory input) public returns(bool);
} }
contract Mixer is MerkleTreeWithHistory { contract Mixer is MerkleTreeWithHistory {
using SafeMath for uint256;
uint256 public transferValue; uint256 public transferValue;
mapping(uint256 => bool) public nullifiers; mapping(uint256 => bool) public nullifiers;
IVerifier verifier; IVerifier verifier;
@ -17,17 +14,34 @@ contract Mixer is MerkleTreeWithHistory {
event Deposit(address from, uint256 commitment); event Deposit(address from, uint256 commitment);
event Withdraw(address to, uint256 nullifier, uint256 fee); event Withdraw(address to, uint256 nullifier, uint256 fee);
/**
@dev The constructor
@param _verifier the address of SNARK verifier for this contract
@param _transferValue the value for all deposits in this contract in wei
*/
constructor(address _verifier, uint256 _transferValue) MerkleTreeWithHistory(16, 0) public { constructor(address _verifier, uint256 _transferValue) MerkleTreeWithHistory(16, 0) public {
verifier = IVerifier(_verifier); verifier = IVerifier(_verifier);
transferValue = _transferValue; transferValue = _transferValue;
} }
/**
@dev Deposit funds into mixer. The caller must send value equal to `transferValue` of this mixer.
@param commitment the note commitment, which is PedersenHash(nullifier + secret)
*/
function deposit(uint256 commitment) public payable { function deposit(uint256 commitment) public payable {
require(msg.value == transferValue, "Please send `transferValue` ETH along with transaction"); require(msg.value == transferValue, "Please send `transferValue` ETH along with transaction");
insert(commitment); insert(commitment);
emit Deposit(msg.sender, commitment); emit Deposit(msg.sender, commitment);
} }
/**
@dev Withdraw deposit from the mixer. `a`, `b`, and `c` are zkSNARK proof data, and input is an array of circuit public inputs
`input` array consists of:
- merkle root of all deposits in the mixer
- unique deposit nullifier to prevent double spends
- the receiver of funds
- optional fee that goes to the transaction sender (usually a relay)
*/
function withdraw(uint256[2] memory a, uint256[2][2] memory b, uint256[2] memory c, uint256[4] memory input) public { function withdraw(uint256[2] memory a, uint256[2][2] memory b, uint256[2] memory c, uint256[4] memory input) public {
uint256 root = input[0]; uint256 root = input[0];
uint256 nullifier = input[1]; uint256 nullifier = input[1];