tornado-core/contracts/MerkleTreeWithHistory.sol
2019-09-16 13:07:14 +03:00

136 lines
3.8 KiB
Solidity

// https://tornado.cash
/*
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*/
pragma solidity ^0.5.8;
library MiMC {
function MiMCSponge(uint256 in_xL, uint256 in_xR, uint256 in_k) public pure returns (uint256 xL, uint256 xR);
}
contract MerkleTreeWithHistory {
uint256 public levels;
uint8 constant ROOT_HISTORY_SIZE = 100;
uint256[] private _roots;
uint256 public current_root = 0;
uint256[] private _filled_subtrees;
uint256[] private _zeros;
uint32 public next_index = 0;
constructor(uint256 tree_levels, uint256 zero_value) public {
levels = tree_levels;
_zeros.push(zero_value);
_filled_subtrees.push(_zeros[0]);
for (uint8 i = 1; i < levels; i++) {
_zeros.push(hashLeftRight(_zeros[i-1], _zeros[i-1]));
_filled_subtrees.push(_zeros[i]);
}
_roots = new uint256[](ROOT_HISTORY_SIZE);
_roots[0] = hashLeftRight(_zeros[levels - 1], _zeros[levels - 1]);
}
function hashLeftRight(uint256 left, uint256 right) public pure returns (uint256 mimc_hash) {
uint256 k = 21888242871839275222246405745257275088548364400416034343698204186575808495617;
uint256 R = 0;
uint256 C = 0;
R = addmod(R, left, k);
(R, C) = MiMC.MiMCSponge(R, C, 0);
R = addmod(R, right, k);
(R, C) = MiMC.MiMCSponge(R, C, 0);
mimc_hash = R;
}
function _insert(uint256 leaf) internal {
uint32 current_index = next_index;
require(current_index != 2**levels, "Merkle tree is full. No more leafs can be added");
next_index += 1;
uint256 current_level_hash = leaf;
uint256 left;
uint256 right;
for (uint256 i = 0; i < levels; i++) {
if (current_index % 2 == 0) {
left = current_level_hash;
right = _zeros[i];
_filled_subtrees[i] = current_level_hash;
} else {
left = _filled_subtrees[i];
right = current_level_hash;
}
current_level_hash = hashLeftRight(left, right);
current_index /= 2;
}
current_root = (current_root + 1) % ROOT_HISTORY_SIZE;
_roots[current_root] = current_level_hash;
}
function isKnownRoot(uint256 root) public view returns(bool) {
if (root == 0) {
return false;
}
// search most recent first
uint256 i;
for(i = current_root; i < 2**256 - 1; i--) {
if (root == _roots[i]) {
return true;
}
}
// process the rest of roots
for(i = ROOT_HISTORY_SIZE - 1; i > current_root; i--) {
if (root == _roots[i]) {
return true;
}
}
return false;
// or we can do that in other way
// uint256 i = _current_root;
// do {
// if (root == _roots[i]) {
// return true;
// }
// if (i == 0) {
// i = ROOT_HISTORY_SIZE;
// }
// i--;
// } while (i != _current_root);
}
function getLastRoot() public view returns(uint256) {
return _roots[current_root];
}
function roots() public view returns(uint256[] memory) {
return _roots;
}
function filled_subtrees() public view returns(uint256[] memory) {
return _filled_subtrees;
}
function zeros() public view returns(uint256[] memory) {
return _zeros;
}
}