MOVED TO merkletreejs
THIS NPM MODULE IS NOW DEPRECATED. IT'S MOVED 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
Install
npm install m-tree
Classes
Objects
- MerkleTree :
object
Class reprensenting a Merkle Tree
MerkleTree
Kind: global class
- MerkleTree
- new MerkleTree(leaves, hashAlgorithm, options)
- .getLeaves() ⇒
Array.<Buffer>
- .getLayers() ⇒
Array.<Buffer>
- .getRoot() ⇒
Buffer
- .getProof(leaf, [index]) ⇒
Array.<Buffer>
- .verify(proof, targetNode, root) ⇒
Boolean
new MerkleTree(leaves, hashAlgorithm, 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.<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 = const crypto = { // returns Buffer return crypto} const leaves = 'a' 'b' 'c' const tree = leaves sha256
Array.<Buffer>
merkleTree.getLeaves() ⇒ Returns array of leaves of Merkle Tree.
Kind: instance method of MerkleTree
Example
const leaves = tree
Array.<Buffer>
merkleTree.getLayers() ⇒ Returns array of all layers of Merkle Tree, including leaves and root.
Kind: instance method of MerkleTree
Example
const layers = tree
Buffer
merkleTree.getRoot() ⇒ Returns the Merkle root hash as a Buffer.
Kind: instance method of MerkleTree
Example
const root = tree
Array.<Buffer>
merkleTree.getProof(leaf, [index]) ⇒ 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
Example
const leaves = 'a' 'b' 'a'const tree = leaves sha3const proof = tree
Boolean
merkleTree.verify(proof, targetNode, root) ⇒ 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.<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 = treeconst proof = treeconst verified = tree
object
MerkleTree : Class reprensenting a Merkle Tree
Kind: global namespace
- MerkleTree :
object
- new MerkleTree(leaves, hashAlgorithm, options)
- .getLeaves() ⇒
Array.<Buffer>
- .getLayers() ⇒
Array.<Buffer>
- .getRoot() ⇒
Buffer
- .getProof(leaf, [index]) ⇒
Array.<Buffer>
- .verify(proof, targetNode, root) ⇒
Boolean
new MerkleTree(leaves, hashAlgorithm, 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.<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 = const crypto = { // returns Buffer return crypto} const leaves = 'a' 'b' 'c' const tree = leaves sha256
Array.<Buffer>
merkleTree.getLeaves() ⇒ Returns array of leaves of Merkle Tree.
Kind: instance method of MerkleTree
Example
const leaves = tree
Array.<Buffer>
merkleTree.getLayers() ⇒ Returns array of all layers of Merkle Tree, including leaves and root.
Kind: instance method of MerkleTree
Example
const layers = tree
Buffer
merkleTree.getRoot() ⇒ Returns the Merkle root hash as a Buffer.
Kind: instance method of MerkleTree
Example
const root = tree
Array.<Buffer>
merkleTree.getProof(leaf, [index]) ⇒ 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
Example
const leaves = 'a' 'b' 'a'const tree = leaves sha3const proof = tree
Boolean
merkleTree.verify(proof, targetNode, root) ⇒ 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.<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 = treeconst proof = treeconst verified = tree
Test
npm test
Notes
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.
Resources
-
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?
License
MIT