https://github.com/bitcoinjs/merkle-lib
A performance conscious library for merkle root and tree calculations.
https://github.com/bitcoinjs/merkle-lib
bitcoin digest hash merkle merkle-root merkle-tree
Last synced: 3 months ago
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A performance conscious library for merkle root and tree calculations.
- Host: GitHub
- URL: https://github.com/bitcoinjs/merkle-lib
- Owner: bitcoinjs
- License: mit
- Created: 2016-10-07T05:14:16.000Z (about 9 years ago)
- Default Branch: master
- Last Pushed: 2024-08-08T14:27:50.000Z (about 1 year ago)
- Last Synced: 2025-06-06T01:18:54.723Z (4 months ago)
- Topics: bitcoin, digest, hash, merkle, merkle-root, merkle-tree
- Language: JavaScript
- Homepage:
- Size: 541 KB
- Stars: 31
- Watchers: 5
- Forks: 14
- Open Issues: 6
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# merkle-lib
[](https://travis-ci.org/bitcoinjs/merkle-lib)
[](https://www.npmjs.org/package/merkle-lib)
[](https://github.com/feross/standard)
A performance conscious library for merkle root and tree calculations.
## Warnings
This implementation is vulnerable to a forgery attack [as a second pre-image attack](https://en.wikipedia.org/wiki/Merkle_tree#Second_preimage_attack), see these[\[1\]](https://crypto.stackexchange.com/questions/2106/what-is-the-purpose-of-using-different-hash-functions-for-the-leaves-and-interna)[\[2\]](https://crypto.stackexchange.com/questions/43430/what-is-the-reason-to-separate-domains-in-the-internal-hash-algorithm-of-a-merkl/44971#44971) crypto.stackexchange questions for an explanation.
To avoid this vulnerability, you should pre-hash your leaves *using a different hash function* than the function provided such that `H(x) != H'(x)`.
Additionally, this implementation is vulnerable to a forgery attack [for an unbalanced merkle tree](https://bitcointalk.org/?topic=102395), wherein, in an unbalanced merkle tree, the last leaf node can be duplicated to create an artificial balanced tree, resulting in the same root hash.
To avoid this vulnerability [in this implementation], do not accept unbalanced merkle trees in your application.
## Examples
Preamble
``` javascript
var crypto = require('crypto')
function sha256 (data) {
return crypto.createHash('sha256').update(data).digest()
}
var data = [
'cafebeef',
'ffffffff',
'aaaaaaaa',
'bbbbbbbb',
'cccccccc'
].map(x => new Buffer(x, 'hex'))
// ... now, the examples
```
Tree
``` javascript
var merkle = require('merkle-lib')
var tree = merkle(data, sha256)
console.log(tree.map(x => x.toString('hex')))
// => [
// 'cafebeef',
// 'ffffffff',
// 'aaaaaaaa',
// 'bbbbbbbb',
// 'cccccccc',
// 'bda5c39dec343da54ce91c57bf8e796c2ca16a1bd8cae6a2cefbdd16efc32578',
// '8b722baf6775a313f1032ba9984c0dce32ff3c40d7a67b5df8de4dbaa43a3db0',
// '3d2f424783df5853c8d7121b1371650c04241f318e1b0cd46bedbc805b9164c3',
// 'bb232963fd0efdeacb0fd76e26cf69055fa5facc19a5f5c2f2f27a6925d1db2f',
// '2256e70bea2c591190a0d4d6c1415acd7458fae84d8d85cdc68b851da27777d4',
// 'c2692b0e127b3b774a92f6e1d8ff8c3a5ea9eef9a1d389fe294f0a7a2fec9be1'
//]
```
Root only (equivalent to `tree[tree.length - 1]`)
``` javascript
var fastRoot = require('merkle-lib/fastRoot')
var root = fastRoot(data, sha256)
console.log(root.toString('hex'))
// => 'c2692b0e127b3b774a92f6e1d8ff8c3a5ea9eef9a1d389fe294f0a7a2fec9be1'
```
Proof (with verify)
``` javascript
var merkleProof = require('merkle-lib/proof')
var proof = merkleProof(tree, data[0])
if (proof === null) {
console.error('No proof exists!')
}
console.log(proof.map(x => x && x.toString('hex')))
// => [
// 'cafebeef',
// 'ffffffff',
// null,
// '8b722baf6775a313f1032ba9984c0dce32ff3c40d7a67b5df8de4dbaa43a3db0',
// null,
// '2256e70bea2c591190a0d4d6c1415acd7458fae84d8d85cdc68b851da27777d4',
// 'c2692b0e127b3b774a92f6e1d8ff8c3a5ea9eef9a1d389fe294f0a7a2fec9be1'
// ]
console.log(merkleProof.verify(proof, sha256))
// => true
```
#### Credits
Thanks to [Meni Rosenfield on bitcointalk](https://bitcointalk.org/index.php?topic=403231.msg9054025#msg9054025) for the math.