slip39-dart

The dart implementation of the SLIP39 for Shamir's Secret-Sharing for Mnemonic Codes.

The code based on the Reference implementation of SLIP-0039.

DISCLAIMER

This project is still in early development phase. Use it at your own risk.

Description

This SLIP39 implementation uses a 3 level height (l=3) of a 16 degree (d=16) tree (T), which is represented as an array of the level two nodes (groups, G).

The degree (d) and the level (l) of the tree are 16 and 3 respectively, which means that max d^(l-1), i.e. 16^2, leaf nodes (M) can be in a complete tree (or forest).

The first level (l=1) node of the tree is the the root (R), the level 2 ones are the SSS groups (Gs or group nodes) e.g. [G0, ..., Gd].

The last, the third, level nodes are the only leafs (M, group members) which contains the generated mnemonics.

Every node has two values:

• the N and
• M i.e. n(N,M).

Whihc means, that N (threshold) number of M children are required to reconstruct the node's secret.

Format

There are two formats for representing the shares:

• The JSON format, see details here
• and a simplye array/List format.

The The tree's human friendly array representation only uses the group (l=2) nodes as arrays. For example. : [[1,1], [1,1], [3,5], [2,6]] The group's first parameter is the N (group threshold) while the second is the M, the number of members in the group. See, details in Example.

Installing

Add the following into the pubspec.yaml:

dependencies:
  slip39: ^0.2.1

Example

import 'package:slip39/slip39dart';

int main() {
// threshold (N) number of group shares required to reconstruct the master secret.
final threshold = 2;
final masterSecret = "ABCDEFGHIJKLMNOP";
final passphrase = "TREZOR";

// 4 groups shares and 2 are required to reconstruct the master secret.
final groups = [
  // Alice group shares. 1 is enough to reconstruct a group share,
  // therefore she needs at least two group shares to be reconstructed,
  [1, 1],
  [1, 1],
  // 3 of 5 Friends' shares are required to reconstruct this group share
  [3, 5],
  // 2 of 6 Family's shares are required to reconstruct this group share
  [2, 6]
];

final slip = Slip39.fromArray(
    masterSecret: masterSecret,
    passphrase: passphrase,
    threshold: threshold,
    groups: groups);

// One of Alice's share
final aliceShare = slip.fromPath('r/0').mnemonics;

// and any two of family's shares.
var familyShares = slip.fromPath('r/3/1').mnemonics;
familyShares = familyShares..addAll(slip.fromPath('r/3/3').mnemonics);

final allShares = aliceShare..addAll(familyShares);

print("Shares used for restoring the master secret:");
allShares..forEach((s) => print(s));

final recoveredSecret = Slip39.recoverSecret(allShares, passphrase);
assert(masterSecret == recoveredSecret);
print("Recovered secret: $recoveredSecret");
}

TODOS

• Add unit tests.
• Test with the reference code's test vectors.
• Refactor the helpers to different helper classes e.g. CryptoHelper(), ShamirHelper() etc.
• Add JSON representation, see JSON representation below.
• Refactor to much simpler code.

JSON Representation

See in an example code from eample/example.dart below:

import 'dart:convert';

import 'package:slip39/slip39.dart';

void main() {
  String masterSecret = "ABCDEFGHIJKLMNOP";
  String passphrase = "TREZOR";

  //
  // RFC 4627 compliant JSON
  //
  final jsonString = '''
{
  "name": "Alice's shares",
  "threshold": 2,
  "shares" : [
    {
      "name": "Primary",
      "threshold": 1,
      "shares": ["Primary share"]
    },
    {
      "name": "Secondary",
      "threshold": 1,
      "shares": ["Secondary share"]
    },
    {
      "name": "Friends",
      "threshold": 3,
      "shares": ["Albert", "Ben", "Carol", "David", "Edward", "Fred"]
    },
    {
      "name": "Family",
      "threshold": 2,
      "shares": ["Adam", "Brenda", "Cecil", "Donald", "Elissa"]
    }
  ]
}
''';

  final json = jsonDecode(jsonString);

  final slip = Slip39.from(
    json,
    masterSecret: masterSecret.codeUnits,
    passphrase: passphrase,
  );

  final masterNode = slip.fromPath('r');

  final jsonText = jsonEncode(masterNode);
  assert(jsonEncode(json) == jsonText);

  final familyNode = masterNode.derive(3);
  final familyNode2 = masterNode.deriveByName('Family');
  assert(familyNode == familyNode2);

  var familyShares = familyNode.mnemonics..shuffle();
  familyShares = familyShares.sublist(0, 2);

  // Recover from: 3 of 5 firend's shares and 2 of 6 of family shares
  // three Friend's shares
  var friendsShares = masterNode.deriveByName('Friends').mnemonics..shuffle();
  friendsShares = friendsShares.sublist(0, 3);

  final allShares = familyShares..addAll(friendsShares);

  print("Shares used for restoring the master secret:");
  allShares..forEach((s) => print(s));

  final recoveredSecret = String.fromCharCodes(
      Slip39.recoverSecret(allShares, passphrase: passphrase));
  print('\nMaster secret: $masterSecret');
  print("Recovered one: $recoveredSecret");
  assert(masterSecret == recoveredSecret);
}

Package Direcotry Structure

The dart package directory structure follows the official dart's recommendations.

LICENSE

CopyRight (c) 2019 Pal Dorogi "iLap" pal.dorogi@gmail.com

MIT License