onchainlabs_flutter

Polygon EVM wallet helper for Flutter mobile apps.

Goal: give you a simple way to:

  • create a Polygon-compatible wallet (address + private key + mnemonic)
  • sign a backend challenge
  • register the wallet with https://ga-api.onchainlabs.ch
  • store the mnemonic locally on the device
  • mint tokens
  • Get token balance

Security note
Do not use this as your only security layer for large amounts of funds.
Always audit code, review storage, and consider hardware wallets for serious use.

What it does

  • Generates a BIP39 mnemonic (12 words by default).
  • Derives a private key with BIP32 path m/44'/60'/0'/0/0.
  • Builds an EVM address using web3dart.
  • Calls POST https://ga-api.onchainlabs.ch/random with { address }.
  • Signs the returned signMessage with the wallet (personal sign).
  • Calls POST https://ga-api.onchainlabs.ch/register with { message, signature }.
  • Stores securely the mnemonic string under the key wlltMnic.

The wallet is a normal Ethereum wallet, so the address type works on Polygon.

Install

In your app pubspec.yaml:

dependencies:
  Onchainlabs_flutter: ^2.0.1

Code Examples : 

### 1. Generate a wallet (create + register + store mnemonic)

import 'package:onchainlabs_flutter/onchainlabs_flutter.dart';

Future<void> createWalletExample() async {
  final api = OnchainLabsApi();
  final manager = await PolygonWalletManager.create(api);

  final wallet = await manager.createWallet();

  print('Address: ${wallet.address}');
  print('Private key (hex): 0x${wallet.privateKeyHex}');
  print('Mnemonic: ${wallet.mnemonic}');
}

### 2. Authenticate a wallet (sign random message and send to backend)

You can authenticate either:

- the current in-memory wallet, or  
- the wallet restored from secure storage.

#### 2.1 Auth the current wallet

import 'package:onchainlabs_flutter/onchainlabs_flutter.dart';

Future<void> authCurrentWalletExample(PolygonWallet wallet) async {
  final api = OnchainLabsApi();
  final manager = await PolygonWalletManager.create(api);

  final backendAddress = await manager.authenticateWallet(wallet);

  print('Backend authenticated address: $backendAddress');
}

#### 2.2 Auth the stored wallet (from secure storage)

import 'package:onchainlabs_flutter/onchainlabs_flutter.dart';

Future<void> authStoredWalletExample() async {
  final api = OnchainLabsApi();
  final manager = await PolygonWalletManager.create(api);

  final backendAddress = await manager.authenticateStoredWallet();

  print('Backend authenticated stored wallet: $backendAddress');
}

### 3. Restore a wallet from a mnemonic phrase

Use this when the user already has a recovery phrase and you want to:

- rebuild the wallet (address + private key)  
- register it with the backend  
- store the mnemonic in secure storage  

import 'package:onchainlabs_flutter/onchainlabs_flutter.dart';

Future<void> restoreWalletFromMnemonicExample() async {
  final api = OnchainLabsApi();
  final manager = await PolygonWalletManager.create(api);

  const userMnemonic =
      'word1 word2 word3 word4 word5 word6 word7 word8 word9 word10 word11 word12';

  final wallet = await manager.restoreWallet(userMnemonic);

  print('Restored wallet address: ${wallet.address}');
  print('Restored private key (hex): 0x${wallet.privateKeyHex}');
}

### 4. Restore a wallet from a private key

Use this if the user owns a **raw EVM private key** (64-hex string) and needs to:

- rebuild the wallet  
- authenticate it with your backend  
- store it securely  

import 'package:onchainlabs_flutter/onchainlabs_flutter.dart';

Future<void> restoreWalletFromPrivateKeyExample() async {
  final api = OnchainLabsApi();
  final manager = await PolygonWalletManager.create(api);

  const userPrivateKey =
      'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa';

  final wallet = await manager.restoreWalletFromPrivateKey(userPrivateKey);

  print('Restored wallet address: ${wallet.address}');
}











### 5. Mint tokens and ask token balance using an API public Key

import 'package:onchainlabs_flutter/simple_onchain_api.dart';

/// Set your public key (user input in secured storage in production)
const publicKey =
    'suQxa7jxvgfQmrKQYhCT6TZxYxbmNUHrG82VPEdYy01eZ1wsQwWjUZJPSZyyapQJ';

final api = SimpleOnchainApi(publicKey: publicKey);

### 5.1 Convert Human amount (base units 6 decimals)
String toBaseUnits(String human, {int decimals = 6}) {
  if (!human.contains('.')) {
    return human + '0'.padRight(decimals, '0');
  }
  final parts = human.split('.');
  final whole = parts[0];
  var frac = parts[1];
  if (frac.length > decimals) {
    throw Exception('Too many decimals');
  }
  frac = frac.padRight(decimals, '0');
  return whole + frac;
}

### 5.2 Mint Tokens Full API mode
Future<void> mintExample(PolygonWallet wallet) async {
  final api = SimpleOnchainApi(publicKey: publicKey);

  final amount = toBaseUnits("1000"); // → "1000000000"

  final res = await api.mint(
    address: wallet.address,
    amount: amount,
    waitForTx: true,
  );

  print('Mint result: $res');
}

### 5.3 Get Token Balance
Future<void> balanceExample(PolygonWallet wallet) async {
  final api = SimpleOnchainApi(publicKey: publicKey);

  final res = await api.balanceOf(wallet.address);

  print('Balance: $res');
}

Libraries

onchainlabs_flutter
simple_onchain_api