tornado-core/contracts/MerkleTreeWithHistory.sol
2019-11-08 02:58:12 +03:00

121 lines
4.0 KiB
Solidity

// https://tornado.cash
/*
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*/
pragma solidity ^0.5.8;
library Hasher {
function MiMCSponge(uint256 in_xL, uint256 in_xR, uint256 in_k) public pure returns (uint256 xL, uint256 xR);
}
contract MerkleTreeWithHistory {
uint256 public constant FIELD_SIZE = 21888242871839275222246405745257275088548364400416034343698204186575808495617;
uint256 public constant ZERO_VALUE = 5702960885942360421128284892092891246826997279710054143430547229469817701242; // = MiMC("tornado")
uint32 public levels;
// the following variables are made public for easier testing and debugging and
// are not supposed to be accessed in regular code
bytes32[] public filledSubtrees;
bytes32[] public zeros;
uint32 public currentRootIndex = 0;
uint32 public nextIndex = 0;
uint32 public constant ROOT_HISTORY_SIZE = 100;
bytes32[ROOT_HISTORY_SIZE] public roots;
constructor(uint32 _treeLevels) public {
require(_treeLevels > 0, "_treeLevels should be greater than zero");
require(_treeLevels < 32, "_treeLevels should be less than 32");
levels = _treeLevels;
bytes32 currentZero = bytes32(ZERO_VALUE);
zeros.push(currentZero);
filledSubtrees.push(currentZero);
for (uint32 i = 1; i < levels; i++) {
currentZero = hashLeftRight(currentZero, currentZero);
zeros.push(currentZero);
filledSubtrees.push(currentZero);
}
roots[0] = hashLeftRight(currentZero, currentZero);
}
/**
@dev Hash 2 tree leaves, returns MiMC(_left, _right)
*/
function hashLeftRight(bytes32 _left, bytes32 _right) public pure returns (bytes32) {
require(uint256(_left) < FIELD_SIZE, "_left should be inside the field");
require(uint256(_right) < FIELD_SIZE, "_right should be inside the field");
uint256 R = uint256(_left);
uint256 C = 0;
(R, C) = Hasher.MiMCSponge(R, C, 0);
R = addmod(R, uint256(_right), FIELD_SIZE);
(R, C) = Hasher.MiMCSponge(R, C, 0);
return bytes32(R);
}
function _insert(bytes32 _leaf) internal returns(uint32 index) {
uint32 currentIndex = nextIndex;
require(currentIndex != uint32(2)**levels, "Merkle tree is full. No more leafs can be added");
nextIndex += 1;
bytes32 currentLevelHash = _leaf;
bytes32 left;
bytes32 right;
for (uint32 i = 0; i < levels; i++) {
if (currentIndex % 2 == 0) {
left = currentLevelHash;
right = zeros[i];
filledSubtrees[i] = currentLevelHash;
} else {
left = filledSubtrees[i];
right = currentLevelHash;
}
currentLevelHash = hashLeftRight(left, right);
currentIndex /= 2;
}
currentRootIndex = (currentRootIndex + 1) % ROOT_HISTORY_SIZE;
roots[currentRootIndex] = currentLevelHash;
return nextIndex - 1;
}
/**
@dev Whether the root is present in the root history
*/
function isKnownRoot(bytes32 _root) public view returns(bool) {
if (_root == 0) {
return false;
}
uint32 i = currentRootIndex;
do {
if (_root == roots[i]) {
return true;
}
if (i == 0) {
i = ROOT_HISTORY_SIZE;
}
i--;
} while (i != currentRootIndex);
return false;
}
/**
@dev Returns the last root
*/
function getLastRoot() public view returns(bytes32) {
return roots[currentRootIndex];
}
}