MerkleTree.js Solidity example
Construct merkle trees with MerkleTree.js and verify merkle proofs in Solidity.
Example
pragma solidity ^0.5.2;
contract MerkleProof {
function verify(
bytes32 root,
bytes32 leaf,
bytes32[] memory proof
)
public
pure
returns (bool)
{
bytes32 computedHash = leaf;
for (uint256 i = 0; i < proof.length; i++) {
bytes32 proofElement = proof[i];
if (computedHash <= proofElement) {
// Hash(current computed hash + current element of the proof)
computedHash = keccak256(abi.encodePacked(computedHash, proofElement));
} else {
// Hash(current element of the proof + current computed hash)
computedHash = keccak256(abi.encodePacked(proofElement, computedHash));
}
}
// Check if the computed hash (root) is equal to the provided root
return computedHash == root;
}
}const MerkleProof = artifacts.require('MerkleProof')
const MerkleTree = require('merkletreejs')
const keccak256 = require('keccak256')
const contract = await MerkleProof.new()
const leaves = ['a', 'b', 'c', 'd'].map(v => keccak256(v))
const tree = new MerkleTree(leaves, keccak256, { sort: true })
const root = tree.getHexRoot()
const leaf = keccak256('a')
const proof = tree.getHexProof(leaf)
console.log(await contract.verify.call(root, leaf, proof)) // true
const badLeaves = ['a', 'b', 'x', 'd'].map(v => keccak256(v))
const badTree = new MerkleTree(badLeaves, keccak256, { sort: true })
const badProof = badTree.getHexProof(leaf)
console.log(await contract.verify.call(root, leaf, badProof)) // falseTest
make testLicense
MIT