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A performance conscious package for merkle root and tree calculations.

merkle-lib #

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, see these[1] [2] 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, 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

import 'dart:typed_data';

import 'package:convert/convert.dart';
import 'package:crypto/crypto.dart' as crypto;

Uint8List sha256(data) {
  return Uint8List.fromList(crypto.sha1.convert(data).bytes);
}

List<Uint8List> data = [
  'cafebeef',
  'ffffffff',
  'aaaaaaaa',
  'bbbbbbbb',
  'cccccccc'
].map((x) => Uint8List.fromList(hex.decode(x))).toList();

// ... now, the examples

Tree #

  List<Uint8List> tree = merkle(data, sha256);

  print('[\n\t"${tree.map((x) => hex.encode(x)).join('",\n\t"')}"\n]');
  // => [
  // 	"cafebeef",
  // 	"ffffffff",
  // 	"aaaaaaaa",
  // 	"bbbbbbbb",
  // 	"cccccccc",
  // 	"bda5c39dec343da54ce91c57bf8e796c2ca16a1bd8cae6a2cefbdd16efc32578",
  // 	"8b722baf6775a313f1032ba9984c0dce32ff3c40d7a67b5df8de4dbaa43a3db0",
  // 	"3d2f424783df5853c8d7121b1371650c04241f318e1b0cd46bedbc805b9164c3",
  // 	"bb232963fd0efdeacb0fd76e26cf69055fa5facc19a5f5c2f2f27a6925d1db2f",
  // 	"2256e70bea2c591190a0d4d6c1415acd7458fae84d8d85cdc68b851da27777d4",
  // 	"c2692b0e127b3b774a92f6e1d8ff8c3a5ea9eef9a1d389fe294f0a7a2fec9be1"
  // ]

Root only (equivalent to tree[tree.length - 1]) #

  Uint8List root = fastRoot(data, sha256);
  print(hex.encode(root));
  // => 'c2692b0e127b3b774a92f6e1d8ff8c3a5ea9eef9a1d389fe294f0a7a2fec9be1'

Proof (with verify) #

  List<Uint8List> tree = merkle(data, sha256);
  List<Uint8List?>? proof = merkleProof(tree, data[0]);

  if (proof == null) {
    throw Exception('No proof exists!');
  }

  print(
      '[\n\t${proof.map((x) => x == null ? 'null' : '"' + hex.encode(x)).join(',\n\t') + '"'}\n]');
  // => [
  //   'cafebeef',
  //   'ffffffff',
  //   null,
  //   '8b722baf6775a313f1032ba9984c0dce32ff3c40d7a67b5df8de4dbaa43a3db0',
  //   null,
  //   '2256e70bea2c591190a0d4d6c1415acd7458fae84d8d85cdc68b851da27777d4',
  //   'c2692b0e127b3b774a92f6e1d8ff8c3a5ea9eef9a1d389fe294f0a7a2fec9be1'
  // ]

  print(verify(proof, sha256));
  // => true
// => true
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A performance conscious package for merkle root and tree calculations.

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License

Icon for licenses.MIT (LICENSE)

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