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Using Core Kit SFA Flutter SDK

After successfully installing and initializing SingleFactorAuth, you can use it to authenticate your users and obtain their private and public keys.

The SingleFactorAuth instance natively provides the following functions:

  • getKey(LoginParams) - Returns the private key using the verifier, verifierId & idToken.
  • getAggregateKey(LoginParams) - Returns the aggregate private key using the verifier, verifierId & idToken.

getKey()​

To obtain a user's private key using the Web3Auth SFA Flutter SDK, you can call the getKey() function.

VariableDescription
loginParamsParameters for the login. It takes LoginParams as the value.

Returns​

Future<TorusKey> getKey(LoginParams loginParams)

On successful call, the getKey() function returns a Future<TorusKey> instance.

LoginParams​

ParameterDescription
verifierThe verifier obtained from the Web3Auth Dashboard. It's a mandatory field and takes String as a value.
verifierIdThe verifierId used for the verification. It takes String as a value.
idTokenThe idToken of the user obtained from login provider. It takes String as a value.
aggregateVerifier?The aggregate verifier obtained from the Web3Auth Dashboard. It takes String as a value.
Usage
Future<TorusKey> getKey() {
  return _singleFactorAuthFlutterPlugin.getKey(LoginParams(
    verifier: 'YOUR_VERIFIER_NAME',
    verifierId: 'YOUR_VERIFIER_ID',
    idToken: 'YOUR_ID_TOKEN',
    ),
  );
}

getAggregateKey()​

To obtain a user's Torus key using the Web3Auth SFA Flutter SDK, you can call the getAggregateKey() function.

VariableDescription
loginParamsParameters for the login. It takes LoginParams as the value.

Returns​

Future<TorusKey> getAggregateKey(LoginParams loginParams)

On successful call, the getAggregateKey() function returns a Future<TorusKey> instance.

LoginParams​

ParameterDescription
verifierThe verifier obtained from the Web3Auth Dashboard. It's a mandatory field and takes String as a value.
verifierIdThe verifierId used for the verification. It takes String as a value.
idTokenThe idToken of the user obtained from login provider. It takes String as a value.
aggregateVerifier?The aggregate verifier obtained from the Web3Auth Dashboard. It takes String as a value.
Usage
Future<TorusKey> getAggregateKey() {
  return _singleFactorAuthFlutterPlugin.getAggregateKey(LoginParams(
    verifier: 'YOUR_VERIFIER_NAME',
    verifierId: 'YOUR_VERIFIER_ID',
    idToken: 'YOUR_ID_TOKEN',
    aggregateVerifier: 'YOUR_AGGREGATE_VERIFIER_NAME',
  ));
}
Note

Web3Auth SFA Flutter SDK only works for users who have not enabled MFA.

MFA enabled users

For MFA enabled users, you'll see an Error message.

Session Management​

We have included Session Management in this SDK, so calling the initialize function to get the TorusKey value without re-logging in the user if a user has an active session will return the TorusKey, otherwise, it will return null.

final TorusKey? torusKey = await _singleFactorAuthFlutterPlugin.initialize();

Example​

lib/main.dart

main.dart
import 'dart:async';
import 'dart:developer';
import 'dart:io';

import 'package:flutter/material.dart';
import 'package:single_factor_auth_flutter/input.dart';
import 'package:single_factor_auth_flutter/output.dart';
import 'package:single_factor_auth_flutter/single_factor_auth_flutter.dart';
import './utils.dart';

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

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

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  final _singleFactorAuthFlutterPlugin = SingleFactAuthFlutter();
  String _result = '';
  bool logoutVisible = false;
  TorusNetwork torusNetwork = TorusNetwork.testnet;

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

  Future<void> initSdk() async {
    if (Platform.isAndroid) {
      await init();
      initialize();
    } else if (Platform.isIOS) {
      await init();
      initialize();
    } else {}
  }

  Future<void> init() async {
    await _singleFactorAuthFlutterPlugin
        .init(Web3AuthNetwork(network: torusNetwork));
  }

  Future<void> initialize() async {
    log("initialize() called");
    final TorusKey? torusKey =
        await _singleFactorAuthFlutterPlugin.initialize();
    if (torusKey != null) {
      setState(() {
        _result = "Private Key : ${torusKey.privateKey}";
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('SingleFactorAuthFlutter Example'),
        ),
        body: SingleChildScrollView(
          child: Center(
              child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              const Padding(
                padding: EdgeInsets.all(8.0),
              ),
              Visibility(
                child: Column(
                  children: [
                    const SizedBox(
                      height: 50,
                    ),
                    const Icon(
                      Icons.flutter_dash,
                      size: 80,
                      color: Color(0xFF1389fd),
                    ),
                    const SizedBox(
                      height: 40,
                    ),
                    const Text(
                      'Web3Auth',
                      style: TextStyle(
                          fontWeight: FontWeight.bold,
                          fontSize: 36,
                          color: Color(0xFF0364ff)),
                    ),
                    const SizedBox(
                      height: 10,
                    ),
                    const Text(
                      'Welcome to SingleFactorAuthFlutter Demo',
                      style: TextStyle(fontSize: 14),
                    ),
                    const SizedBox(
                      height: 20,
                    ),
                    const Text(
                      'Get TorusKey',
                      style: TextStyle(fontSize: 12),
                    ),
                    const SizedBox(
                      height: 20,
                    ),
                    ElevatedButton(
                      onPressed: _getKey(getAggregrateKey),
                      child: const Text('GetTorusKey'),
                    ),
                    ElevatedButton(
                      onPressed: () => _initialize(),
                      child: const Text('Get Session Response'),
                    ),
                  ],
                ),
              ),
              Padding(
                padding: const EdgeInsets.all(8.0),
                child: Text(_result),
              )
            ],
          )),
        ),
      ),
    );
  }

  VoidCallback _getKey(Future<TorusKey> Function() method) {
    return () async {
      try {
        final TorusKey response = await method();
        setState(() {
          _result = "Private Key : ${response.privateKey}";
          log(response.publicAddress);
        });
      } on PrivateKeyNotGeneratedException {
        log("Private key not generated");
      } on UnKnownException {
        log("Unknown exception occurred");
      }
    };
  }

  Future<void> _initialize() async {
    try {
      final TorusKey? response =
          await _singleFactorAuthFlutterPlugin.initialize();
      setState(() {
        _result = "Private Key : ${response?.privateKey}";
        log(response!.publicAddress);
      });
    } on PrivateKeyNotGeneratedException {
      log("Private key not generated");
    } on UnKnownException {
      log("Unknown exception occurred");
    }
  }

  Future<TorusKey> getKey() {
    return _singleFactorAuthFlutterPlugin.getKey(
      LoginParams(
        verifier: 'torus-test-health',
        verifierId: 'hello@tor.us',
        idToken: Utils().es256Token("hello@tor.us"),
      ),
    );
  }

  Future<TorusKey> getAggregrateKey() {
    return _singleFactorAuthFlutterPlugin.getAggregateKey(
      LoginParams(
        verifier: 'torus-test-health',
        verifierId: 'hello@tor.us',
        idToken: Utils().es256Token("hello@tor.us"),
        aggregateVerifier: 'torus-test-health-aggregate',
      ),
    );
  }
}

lib/utils.dart

This Dart code will produce a JSON Web Token (JWT) using the ES256 algorithm. You have the option to use your own implementation or follow our Bring your own JWT token steps. Alternatively, you may choose to use any social/federated identity provider that is supported by Web3auth.

utils.dart
import 'package:dart_jsonwebtoken/dart_jsonwebtoken.dart';

class Utils {
  String es256Token(String email) {
    String token;

    /* Sign */ {
      // Create a json web token
      final jwt = JWT({
        "sub": "email|hello",
        "aud": "torus-key-test",
        "exp": DateTime.now().millisecond,
        "iat": DateTime.now().millisecond,
        "iss": "torus-key-test",
        "email": email,
        "nickname": email.split("@")[0],
        "name": email,
        "picture": "",
        "email_verified": true
      });

      // Sign it
      final key = ECPrivateKey("-----BEGIN PRIVATE KEY-----\n"
          "MEECAQAwEwYHKoZIzj0CAQYIKoZIzj0DAQcEJzAlAgEBBCCD7oLrcKae+jVZPGx52Cb/lKhdKxpXjl9eGNa1MlY57A=="
          "\n-----END PRIVATE KEY-----");
      token = jwt.sign(key, algorithm: JWTAlgorithm.ES256);

      print('Signed token: \n $token\n');
      return token;
    }
  }
}