strong_password 1.1.0

A Dart/Flutter package that generates very strong passwords the way Gmail does, plus per-service deterministic passwords, passphrases, PINs, and password strength estimation.

example/lib/main.dart

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:strong_password/strong_password.dart';

void main() {
  runApp(const StrongPasswordDemo());
}

/// A copy-paste friendly demo of the `strong_password` package.
///
/// Runs on Android, Web, iOS, desktop — anywhere Flutter runs.
/// Build it with:  `flutter run`  (or `flutter run -d chrome` /
/// `flutter run -d <android-device>`).
class StrongPasswordDemo extends StatelessWidget {
  const StrongPasswordDemo({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'strong_password demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.indigo),
        useMaterial3: true,
      ),
      home: const HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  const HomePage({super.key});

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  final _generator = StrongPasswordGenerator();

  // ————— State —————
  String _strongPassword = '';
  String _passphrase = '';
  String _pin = '';
  String _deterministic = '';
  String _masterSecret = 'correct-horse-battery-staple';
  String _service = 'gmail.com';

  PasswordStrength? _strength;

  @override
  void initState() {
    super.initState();
    _generateAll();
  }

  // ————— Actions —————
  void _generateAll() {
    setState(() {
      _strongPassword = _generator.generate();
      _passphrase = PassphraseGenerator().generate();
      _pin = PinGenerator().generate();
      _regenerateDeterministic();
      _updateStrength();
    });
  }

  void _regenerateDeterministic() {
    _deterministic = const DeterministicPasswordGenerator().generate(
      secret: _masterSecret,
      service: _service,
    );
  }

  void _updateStrength() {
    _strength = estimatePasswordStrength(_strongPassword);
  }

  Future<void> _copy(BuildContext context, String value) async {
    if (value.isEmpty) return;
    final messenger = ScaffoldMessenger.of(context);
    await Clipboard.setData(ClipboardData(text: value));
    messenger.showSnackBar(SnackBar(content: Text('Copied: $value')));
  }

  Widget _resultCard({
    required BuildContext context,
    required String title,
    required String value,
    Widget? trailing,
  }) {
    return Card(
      margin: const EdgeInsets.symmetric(vertical: 6),
      child: ListTile(
        title: Text(title, style: Theme.of(context).textTheme.labelLarge),
        subtitle: SelectableText(value, style: const TextStyle(fontSize: 18)),
        trailing: trailing ??
            IconButton(
              icon: const Icon(Icons.copy),
              tooltip: 'Copy',
              onPressed: () => _copy(context, value),
            ),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    final strength = _strength;
    return Scaffold(
      appBar: AppBar(title: const Text('strong_password demo')),
      body: ListView(
        padding: const EdgeInsets.all(16),
        children: [
          Text(
            'Gmail-style strong passwords, deterministic per-service '
            'passwords, passphrases, PINs and strength checks.',
            style: Theme.of(context).textTheme.bodyMedium,
          ),
          const SizedBox(height: 16),

          // ————— Strong password —————
          _resultCard(
            context: context,
            title: 'Gmail-style strong password (16 chars)',
            value: _strongPassword,
          ),

          // ————— Strength + crack time —————
          if (strength != null)
            Card(
              margin: const EdgeInsets.symmetric(vertical: 6),
              child: Padding(
                padding: const EdgeInsets.all(16),
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: [
                    Text(
                      'Strength: ${strength.strength.name.toUpperCase()}',
                      style: const TextStyle(fontWeight: FontWeight.bold),
                    ),
                    const SizedBox(height: 8),
                    LinearProgressIndicator(
                      value: strength.score / 100,
                      color: _strengthColor(strength.strength),
                    ),
                    const SizedBox(height: 8),
                    Text(
                      'Score ${strength.score}/100 · '
                      '${strength.entropyBits.toStringAsFixed(1)} bits · '
                      'crack time: ${strength.crackTimeLabel()}',
                    ),
                  ],
                ),
              ),
            ),

          // ————— Deterministic —————
          _resultCard(
            context: context,
            title: 'Deterministic password for "$_service"',
            value: _deterministic,
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 6),
            child: Row(
              children: [
                Expanded(
                  child: TextField(
                    decoration: const InputDecoration(
                      labelText: 'Master secret',
                      border: OutlineInputBorder(),
                    ),
                    onChanged: (v) => _masterSecret = v.isEmpty
                        ? _masterSecret
                        : v,
                  ),
                ),
              ],
            ),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 6),
            child: Row(
              children: [
                Expanded(
                  child: TextField(
                    decoration: const InputDecoration(
                      labelText: 'Service (e.g. github.com)',
                      border: OutlineInputBorder(),
                    ),
                    onChanged: (v) => _service = v.isEmpty ? _service : v,
                  ),
                ),
                const SizedBox(width: 8),
                FilledButton.tonal(
                  onPressed: () => setState(_regenerateDeterministic),
                  child: const Text('Derive'),
                ),
              ],
            ),
          ),

          // ————— Passphrase —————
          _resultCard(
            context: context,
            title: 'Memorable passphrase',
            value: _passphrase,
          ),

          // ————— PIN —————
          _resultCard(context: context, title: '6-digit PIN', value: _pin),

          // ————— Profiles —————
          _resultCard(
            context: context,
            title: 'Paranoid profile (32 chars)',
            value: _generator.generate(
              PasswordProfiles.options(PasswordProfiles.paranoid),
            ),
          ),

          const SizedBox(height: 16),
          FilledButton.icon(
            onPressed: _generateAll,
            icon: const Icon(Icons.refresh),
            label: const Text('Generate all again'),
          ),
        ],
      ),
    );
  }

  Color _strengthColor(Strength s) {
    switch (s) {
      case Strength.weak:
        return Colors.red;
      case Strength.fair:
        return Colors.orange;
      case Strength.good:
        return Colors.lightGreen;
      case Strength.strong:
        return Colors.green;
    }
  }
}