merkletreejs

Usage

// the basics
const MerkleTree = require('@sinasabet81/merkletreejs');

const crypto = require('crypto');

const sha256 = preimage =>
  crypto
    .createHash('sha256')
    .update(preimage)
    .digest();

const preimages = ['hello', 'world'];
const leaves = preimages.map(sha256);

const merkleTree = new MerkleTree(leaves, sha256);

console.log(merkleTree.getPrettyRoot()); // '7305db9b2abccd706c256db3d97e5ff48d677cfe4d3a5904afb7da0e3950e1e2'

console.log(merkleTree.getPrettyLayers());
// [ [ '2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824',
//     '486ea46224d1bb4fb680f34f7c9ad96a8f24ec88be73ea8e5a6c65260e9cb8a7' ],
//   [ '7305db9b2abccd706c256db3d97e5ff48d677cfe4d3a5904afb7da0e3950e1e2' ] ]

console.log(merkleTree.getPrettyProof(leaves[0]));
// { siblings:
//   [ { siblingPosition: 'right',
//       siblingHash:
//        '486ea46224d1bb4fb680f34f7c9ad96a8f24ec88be73ea8e5a6c65260e9cb8a7' } ],
//  leaf:
//   '2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824',
//  root:
//   '7305db9b2abccd706c256db3d97e5ff48d677cfe4d3a5904afb7da0e3950e1e2' }

const proof = merkleTree.getProof(leaves[0]);
const result = merkleTree.verifyProof(proof);
console.log(result); // true

Notes

Naive use of this library could be vulerable to a second preimage attack; see this blog post or this wikipedia section for more info. This attack can be avoided by using a separate hash function for your leaves and inner nodes. An example copied from the test file:

const leafHashFunction = inputBuffer =>
  sha256(Buffer.concat([Buffer.alloc(1, 0), inputBuffer]));
const innerHashFunction = inputBuffer =>
  sha256(Buffer.concat([Buffer.alloc(1, 1), inputBuffer]));

const tree1Preimages = ['hello', 'world', 'foo', 'bar'].map(
  Buffer.from,
);
const tree1Leaves = tree1Preimages.map(leafHashFunction);
const tree1 = new MerkleTree(tree1Leaves, innerHashFunction);
const tree1Root = tree1.getRoot();

const tree2Preimages = [
  Buffer.concat([tree1Leaves[0], tree1Leaves[1]]),
  Buffer.concat([tree1Leaves[2], tree1Leaves[3]]),
];
const tree2Leaves = tree2Preimages.map(leafHashFunction);
const tree2 = new MerkleTree(tree2Leaves, innerHashFunction);
const tree2Root = tree2.getRoot();

expect(tree1Root.equals(tree2Root)).toBeFalsy();