slip39

Description:

slip39

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
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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");
}
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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);
}
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Package Direcotry Structure #
The dart package directory structure follows the official dart's recommendations.
LICENSE #
CopyRight (c) 2019 Pal Dorogi "iLap" [email protected]
MIT License