A secure, modular, and extensible password generation library for Dart and Flutter.

• Cryptographically Secure: Uses Random.secure() for strong random number generation.
• Modular Design: Built with interfaces (IPasswordGenerationStrategy, IPasswordStrengthEstimator) for maximum flexibility.
• Customizable:
  • Configure length, character sets, and exclusion of ambiguous characters.
  • Inject custom generation strategies.
  • Inject custom strength estimators.
• Extensible: Easily add new strategies (e.g., memorable words, PINs) without modifying the core library.
• Validation: Built-in validation ensures generated passwords meet your criteria.

Add the package to your pubspec.yaml:

dependencies:
  password_engine: ^1.0.0

import 'package:password_engine/password_engine.dart';

void main() {
  // Create a generator with default settings (RandomPasswordStrategy)
  final generator = PasswordGenerator();

  // Generate a password
  String password = generator.generatePassword(); 
  print(password); // e.g., "aB3$kL9@pQ2!"
}

final generator = PasswordGenerator();

generator.updateConfig(
  PasswordGeneratorConfig(
    length: 20,
    useUpperCase: true,
    useLowerCase: true,
    useNumbers: true,
    useSpecialChars: true,
    excludeAmbiguousChars: true, // e.g., excludes 'I', 'l', '1', 'O', '0'
  ),
);

String password = generator.generatePassword();

The library supports custom generation strategies. You can implement IPasswordGenerationStrategy to create your own.

Note: The MemorablePasswordStrategy and PronounceablePasswordStrategy have been moved to the example app to serve as learning resources. You can copy them into your project if needed.

// Example of using a custom strategy (e.g., from the example app)
final memorableStrategy = MemorablePasswordStrategy(separator: '-');
final generator = PasswordGenerator(generationStrategy: memorableStrategy);

generator.updateConfig(PasswordGeneratorConfig(length: 4)); // 4 words
String password = generator.generatePassword(); // e.g., "correct-horse-battery-staple"

The library includes a default entropy-based strength estimator, but you can inject your own (e.g., one based on zxcvbn).

class MyCustomStrengthEstimator implements IPasswordStrengthEstimator {
  @override
  PasswordStrength estimatePasswordStrength(String password) {
    // Your custom logic here
    return PasswordStrength.strong;
  }
}

final generator = PasswordGenerator(
  strengthEstimator: MyCustomStrengthEstimator(),
);

PasswordStrength strength = generator.estimateStrength("myPassword123");

• CSPRNG: Uses Random.secure() for all random number generation.
• Entropy: The default strength estimator uses Shannon entropy to calculate password strength.
• Validation: Strategies include a validate method to ensure configuration parameters are safe before generation.

• Source Code: GitHub Repository
• Issues: Issue Tracker
• Examples: Check the example folder for a full Flutter app demonstrating custom strategies and UI integration.

MIT License - see the LICENSE file for details.