SYNOPSIS

This is an implementation of the modified merkle patricia tree as specified in the Ethereum Yellow Paper:

The modified Merkle Patricia tree (trie) provides a persistent data structure to map between arbitrary-length binary data (byte arrays). It is defined in terms of a mutable data structure to map between 256-bit binary fragments and arbitrary-length binary data. The core of the trie, and its sole requirement in terms of the protocol specification is to provide a single 32-byte value that identifies a given set of key-value pairs.

The only backing store supported is LevelDB through the levelup module.

INSTALL

npm install merkle-patricia-tree

USAGE

There are 3 variants of the tree implemented in this library, namely: BaseTrie, CheckpointTrie and SecureTrie. CheckpointTrie adds checkpointing functionality to the BaseTrie with the methods checkpoint, commit and revert. SecureTrie extends CheckpointTrie and is the most suitable variant for Ethereum applications. It stores values under the keccak256 hash of their keys.

Initialization and Basic Usage

import level from 'level'
import { BaseTrie as Trie } from 'merkle-patricia-tree'

const db = level('./testdb')
const trie = new Trie(db)

async function test() {
  await trie.put(Buffer.from('test'), Buffer.from('one'))
  const value = await trie.get(Buffer.from('test'))
  console.log(value.toString()) // 'one'
}

test()

Merkle Proofs

const trie = new Trie()

async function test() {
  await trie.put(Buffer.from('test'), Buffer.from('one'))
  const proof = await Trie.createProof(trie, Buffer.from('test'))
  const value = await Trie.verifyProof(trie.root, Buffer.from('test'), proof)
  console.log(value.toString()) // 'one'
}

test()

Read stream on Geth DB

import level from 'level'
import { SecureTrie as Trie } from 'merkle-patricia-tree'

const db = level('YOUR_PATH_TO_THE_GETH_CHAIN_DB')
// Set stateRoot to block #222
const stateRoot = '0xd7f8974fb5ac78d9ac099b9ad5018bedc2ce0a72dad1827a1709da30580f0544'
// Initialize trie
const trie = new Trie(db, stateRoot)

trie
  .createReadStream()
  .on('data', console.log)
  .on('end', () => {
    console.log('End.')
  })

Read Account State including Storage from Geth DB

import level from 'level'
import rlp from 'rlp'
import { BN, bufferToHex } from 'ethereumjs-util'
import Account from 'ethereumjs-account'
import { SecureTrie as Trie } from 'merkle-patricia-tree'

const stateRoot = 'STATE_ROOT_OF_A_BLOCK'

const db = level('YOUR_PATH_TO_THE_GETH_CHAINDATA_FOLDER')
const trie = new Trie(db, stateRoot)

const address = 'AN_ETHEREUM_ACCOUNT_ADDRESS'

async function test() {
  const data = await trie.get(address)
  const acc = new Account(data)

  console.log('-------State-------')
  console.log(`nonce: ${new BN(acc.nonce)}`)
  console.log(`balance in wei: ${new BN(acc.balance)}`)
  console.log(`storageRoot: ${bufferToHex(acc.stateRoot)}`)
  console.log(`codeHash: ${bufferToHex(acc.codeHash)}`)

  let storageTrie = trie.copy()
  storageTrie.root = acc.stateRoot

  console.log('------Storage------')
  const stream = storageTrie.createReadStream()
  stream
    .on('data', (data) => {
      console.log(`key: ${bufferToHex(data.key)}`)
      console.log(`Value: ${bufferToHex(rlp.decode(data.value))}`)
    })
    .on('end', () => {
      console.log('Finished reading storage.')
    })
}

test()

Additional examples with detailed explanations are available here.

API

Documentation

TESTING

npm test

REFERENCES

• Wiki
  • Ethereum Trie Specification
• Blog posts
  • Ethereum's Merkle Patricia Trees - An Interactive JavaScript Tutorial
  • Merkling in Ethereum
  • Understanding the Ethereum Trie. Worth a read, but the Python libraries are outdated.
• Videos
  • Trie and Patricia Trie Overview

EthereumJS

See our organizational documentation for an introduction to EthereumJS as well as information on current standards and best practices.

If you want to join for work or do improvements on the libraries have a look at our contribution guidelines.

LICENSE

MPL-2.0