merkletreejs
Advanced tools
The merkletreejs package is a JavaScript library for constructing and verifying Merkle Trees. Merkle Trees are a fundamental component in blockchain technology and cryptographic applications, providing a way to efficiently and securely verify the integrity of data. This package allows you to create Merkle Trees, generate proofs, and verify proofs.
Creating a Merkle Tree
This feature allows you to create a Merkle Tree from an array of data. The example uses the keccak256 hashing algorithm to hash the data and then constructs the tree. The root of the tree is then printed.
const { MerkleTree } = require('merkletreejs');
const keccak256 = require('keccak256');
const leaves = ['a', 'b', 'c'].map(x => keccak256(x));
const tree = new MerkleTree(leaves, keccak256, { sortPairs: true });
const root = tree.getRoot().toString('hex');
console.log(root);Generating a Proof
This feature allows you to generate a proof for a specific leaf in the Merkle Tree. The proof can be used to verify that the leaf is part of the tree.
const leaf = keccak256('a');
const proof = tree.getProof(leaf);
console.log(proof);Verifying a Proof
This feature allows you to verify a proof against the root of the Merkle Tree. It checks if the provided leaf and proof match the root, ensuring the integrity of the data.
const isValid = tree.verify(proof, leaf, root);
console.log(isValid);The merkletree package is another library for creating and verifying Merkle Trees. It offers similar functionalities to merkletreejs but may have different API conventions and additional features.
The merkle-tools package provides tools for creating and managing Merkle Trees. It includes functionalities for creating trees, generating proofs, and verifying proofs, similar to merkletreejs. It also offers additional utilities for working with Merkle Trees.
The merkle-lib package is a lightweight library for creating and verifying Merkle Trees. It focuses on simplicity and ease of use, providing core functionalities similar to merkletreejs.
Construct Merkle Trees and verify proofs in JavaScript.
Diagram of Merkle Tree
Diagram of Merkle Tree Proof
Diagram of Invalid Merkle Tree Proofs
Diagram of Bitcoin Merkle Tree
npm install merkletreejs
objectClass reprensenting a Merkle Tree
Kind: global class
Array.<Buffer>Array.<Buffer>BufferArray.<Buffer>BooleanConstructs 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.<Buffer> | Array of hashed leaves. Each leaf must be a Buffer. |
| hashAlgorithm | function | Algorithm used for hashing leaves and nodes |
| options | Object | Additional options |
| options.isBitcoinTree | Boolean | If set to true, constructs the Merkle Tree using the Bitcoin Merkle Tree implementation. Enable it when you need to replicate Bitcoin constructed Merkle Trees. In Bitcoin Merkle Trees, single nodes are combined with themselves, and each output hash is hashed again. |
Example
const MerkleTree = require('merkletreejs')
const crypto = require('crypto')
function sha256(data) {
// returns Buffer
return crypto.createHash('sha256').update(data).digest()
}
const leaves = ['a', 'b', 'c'].map(x => sha256(x))
const tree = new MerkleTree(leaves, sha256)
Array.<Buffer>Returns array of leaves of Merkle Tree.
Kind: instance method of MerkleTree
Example
const leaves = tree.getLeaves()
Array.<Buffer>Returns array of all layers of Merkle Tree, including leaves and root.
Kind: instance method of MerkleTree
Example
const layers = tree.getLayers()
BufferReturns the Merkle root hash as a Buffer.
Kind: instance method of MerkleTree
Example
const root = tree.getRoot()
Array.<Buffer>Returns the proof for a target leaf.
Kind: instance method of MerkleTree
Returns: Array.<Buffer> - - 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 => sha256(x))
const tree = new MerkleTree(leaves, sha256)
const proof = tree.getProof(leaves[2], 2)
BooleanReturns 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.<Buffer> | 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)
objectClass reprensenting a Merkle Tree
Kind: global namespace
object
Array.<Buffer>Array.<Buffer>BufferArray.<Buffer>BooleanConstructs 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.<Buffer> | Array of hashed leaves. Each leaf must be a Buffer. |
| hashAlgorithm | function | Algorithm used for hashing leaves and nodes |
| options | Object | Additional options |
| options.isBitcoinTree | Boolean | If set to true, constructs the Merkle Tree using the Bitcoin Merkle Tree implementation. Enable it when you need to replicate Bitcoin constructed Merkle Trees. In Bitcoin Merkle Trees, single nodes are combined with themselves, and each output hash is hashed again. |
Example
const MerkleTree = require('merkletreejs')
const crypto = require('crypto')
function sha256(data) {
// returns Buffer
return crypto.createHash('sha256').update(data).digest()
}
const leaves = ['a', 'b', 'c'].map(x => sha256(x))
const tree = new MerkleTree(leaves, sha256)
Array.<Buffer>Returns array of leaves of Merkle Tree.
Kind: instance method of MerkleTree
Example
const leaves = tree.getLeaves()
Array.<Buffer>Returns array of all layers of Merkle Tree, including leaves and root.
Kind: instance method of MerkleTree
Example
const layers = tree.getLayers()
BufferReturns the Merkle root hash as a Buffer.
Kind: instance method of MerkleTree
Example
const root = tree.getRoot()
Array.<Buffer>Returns the proof for a target leaf.
Kind: instance method of MerkleTree
Returns: Array.<Buffer> - - 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 => sha256(x))
const tree = new MerkleTree(leaves, sha256)
const proof = tree.getProof(leaves[2], 2)
BooleanReturns 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.<Buffer> | 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)
npm test
As is, this implemenation is vulnerable to a second pre-image attack. Use a difference hashing algorithm function for leaves and nodes, so that H(x) != H'(x).
Also, as is, this implementation is vulnerable to a forgery attack for an unbalanced tree, where the last leaf node can be duplicated to create an artificial balanced tree, resulting in the same Merkle root hash. Do not accept unbalanced tree to prevent this.
More info here.
Bitcoin mining the hard way: the algorithms, protocols, and bytes
Why aren't Solidity sha3 hashes not matching what other sha3 libraries produce?
What is the purpose of using different hash functions for the leaves and internals of a hash tree?
MIT
FAQs
Construct Merkle Trees and verify proofs
The npm package merkletreejs receives a total of 54,090 weekly downloads. As such, merkletreejs popularity was classified as popular.
We found that merkletreejs demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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