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Merkle Tree

Construct Merkle Trees and verify via proofs in JavaScript.

Install

npm install m-tree

Documentation

Classes

MerkleTree

Objects

MerkleTree : object

Class reprensenting a Merkle Tree

MerkleTree

Kind: global class

new MerkleTree(leaves, hashAlgo, options)

Constructs a Merkle Tree. All nodes and leaves are stored as Buffers. Lonely leaf nodes are promoted to the next level up without being hashed again.

Param Type Description
leaves Array Array of hashed leaves. Each leaf must be a Buffer.
hashAlgo function Algorithm used for hashing leaves and nodes
options Object Additional options
options.isBitcoinTree Boolean If set to true, generates the Merkle Tree with the Bitcoin Merkle Tree implementation. Enable it when you need to replicate Bitcoin constructed Merkle Trees.

Example

const MerkleTree = require('m-tree')
const crypto = require('crypto')

function sha256(data) {
  // returns Buffer
  return crypto.createHash('sha256').update(data).digest()
}

const leaves = ['a', 'b', 'c'].map(x => sha3(x))

const tree = new MerkleTree(leaves, sha256)

merkleTree.getLeaves() ⇒ Array

Returns leaves of Merkle Tree.

Kind: instance method of MerkleTree Returns: Array - - array of leaves Example

const leaves = tree.getLeaves()

merkleTree.getLayers() ⇒ Array

Returns all layers of Merkle Tree, including leaves and root.

Kind: instance method of MerkleTree Returns: Array - - array of layers Example

const layers = tree.getLayers()

merkleTree.getRoot() ⇒ Buffer

Returns the Merkle root hash.

Kind: instance method of MerkleTree Returns: Buffer - - Merkle root hash Example

const root = tree.getRoot()

merkleTree.getProof(leaf, [index]) ⇒ Array

Returns the proof for a target leaf.

Kind: instance method of MerkleTree Returns: Array - - Array of Buffer hashes.

Param Type Description
leaf Buffer Target leaf
[index] Number Target leaf index in leaves array. Use if there are leaves containing duplicate data in order to distinguish it.

Example

const proof = tree.getProof(leaves[2])

Example

const leaves = ['a', 'b', 'a'].map(x => sha3(x))
const tree = new MerkleTree(leaves, sha3)
const proof = tree.getProof(leaves[2], 2)

merkleTree.verify(proof, targetNode, root) ⇒ Boolean

Returns true if the proof path (array of hashes) can connect the target node to the Merkle root.

Kind: instance method of MerkleTree

Param Type Description
proof Array Array of proof Buffer hashes that should connect target node to Merkle root.
targetNode Buffer Target node Buffer
root Buffer Merkle root Buffer

Example

const root = tree.getRoot()
const proof = tree.getProof(leaves[2])
const verified = tree.verify(proof, leaves[2], root)

MerkleTree : object

Class reprensenting a Merkle Tree

Kind: global namespace Example

const tree = new MerkleTree(leaves, sha256)

new MerkleTree(leaves, hashAlgo, options)

Constructs a Merkle Tree. All nodes and leaves are stored as Buffers. Lonely leaf nodes are promoted to the next level up without being hashed again.

Param Type Description
leaves Array Array of hashed leaves. Each leaf must be a Buffer.
hashAlgo function Algorithm used for hashing leaves and nodes
options Object Additional options
options.isBitcoinTree Boolean If set to true, generates the Merkle Tree with the Bitcoin Merkle Tree implementation. Enable it when you need to replicate Bitcoin constructed Merkle Trees.

Example

const MerkleTree = require('m-tree')
const crypto = require('crypto')

function sha256(data) {
  // returns Buffer
  return crypto.createHash('sha256').update(data).digest()
}

const leaves = ['a', 'b', 'c'].map(x => sha3(x))

const tree = new MerkleTree(leaves, sha256)

merkleTree.getLeaves() ⇒ Array

Returns leaves of Merkle Tree.

Kind: instance method of MerkleTree Returns: Array - - array of leaves Example

const leaves = tree.getLeaves()

merkleTree.getLayers() ⇒ Array

Returns all layers of Merkle Tree, including leaves and root.

Kind: instance method of MerkleTree Returns: Array - - array of layers Example

const layers = tree.getLayers()

merkleTree.getRoot() ⇒ Buffer

Returns the Merkle root hash.

Kind: instance method of MerkleTree Returns: Buffer - - Merkle root hash Example

const root = tree.getRoot()

merkleTree.getProof(leaf, [index]) ⇒ Array

Returns the proof for a target leaf.

Kind: instance method of MerkleTree Returns: Array - - Array of Buffer hashes.

Param Type Description
leaf Buffer Target leaf
[index] Number Target leaf index in leaves array. Use if there are leaves containing duplicate data in order to distinguish it.

Example

const proof = tree.getProof(leaves[2])

Example

const leaves = ['a', 'b', 'a'].map(x => sha3(x))
const tree = new MerkleTree(leaves, sha3)
const proof = tree.getProof(leaves[2], 2)

merkleTree.verify(proof, targetNode, root) ⇒ Boolean

Returns true if the proof path (array of hashes) can connect the target node to the Merkle root.

Kind: instance method of MerkleTree

Param Type Description
proof Array Array of proof Buffer hashes that should connect target node to Merkle root.
targetNode Buffer Target node Buffer
root Buffer Merkle root Buffer

Example

const root = tree.getRoot()
const proof = tree.getProof(leaves[2])
const verified = tree.verify(proof, leaves[2], root)

Test

``bash npm test


# Credits/Resources

- [Bitcoin mining the hard way: the algorithms, protocols, and bytes](http://www.righto.com/2014/02/bitcoin-mining-hard-way-algorithms.html)
- [Raiden Merkle Tree Implemenation](https://github.com/raiden-network/raiden/blob/f9cf12571891cdf54feb4667cd2fffcb3d5daa89/raiden/mtree.py)
- [Bitcoin Talk - Merkle Trees](https://bitcointalk.org/index.php?topic=403231.msg9054025#msg9054025)
- [How Log Proofs Work](https://www.certificate-transparency.org/log-proofs-work)
- [Why aren't Solidity sha3 hashes not matching what other sha3 libraries produce?](https://ethereum.stackexchange.com/questions/559/why-arent-solidity-sha3-hashes-not-matching-what-other-sha3-libraries-produce)

# License

MIT