AES gmc Encryption / Decryption logic in Flutter

niv_encryption_decryption.dart

import 'dart:convert';
import 'dart:typed_data';
import 'package:encrypt/encrypt.dart' as encrypt;
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

void main() {
  runApp(EncryptionApp());
}

class EncryptionApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Encryption App',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: EncryptionPage(),
    );
  }
}

class EncryptionPage extends StatefulWidget {
  @override
  _EncryptionPageState createState() => _EncryptionPageState();
}

class _EncryptionPageState extends State<EncryptionPage> {
  final TextEditingController _contentController = TextEditingController();
  final TextEditingController _aesKeyController = TextEditingController();
  final TextEditingController _encryptedDataController = TextEditingController();
  final TextEditingController _decryptionKeyController = TextEditingController();
  String _encryptedData = '';
  String _decryptedData = '';

  Future<void> _encrypt() async {
    final content = _contentController.text;
    final aesKey = _aesKeyController.text;

    if (content.isEmpty || aesKey.isEmpty) {
      setState(() {
        _encryptedData = 'Content and AES key cannot be empty';
      });
      return;
    }

    try {
      final key = encrypt.Key(Uint8List.fromList(base64Decode(aesKey)));
      final iv = encrypt.IV.fromSecureRandom(12); // AES-GCM typically uses a 12-byte IV

      final encrypter = encrypt.Encrypter(encrypt.AES(key, mode: encrypt.AESMode.gcm));

      final encrypted = encrypter.encrypt(content, iv: iv);
      final gcm = encrypted.bytes;

      // Split ciphertext and tag
      final ciphertext = gcm.sublist(0, gcm.length - 16);
      final tag = gcm.sublist(gcm.length - 16);

      final ciphertextb64 = base64Encode(ciphertext);
      final nonceb64 = base64Encode(iv.bytes);
      final tagb64 = base64Encode(tag);

      final finalData = '$ciphertextb64~$nonceb64~$tagb64';

      setState(() {
        _encryptedData = finalData;
      });
    } catch (e) {
      setState(() {
        _encryptedData = 'Encryption error: $e';
      });
    }
  }

  Future<void> _decrypt() async {
    final encryptedData = _encryptedDataController.text;
    final aesKey = _decryptionKeyController.text;

    if (encryptedData.isEmpty || aesKey.isEmpty) {
      setState(() {
        _decryptedData = 'Encrypted data and AES key cannot be empty';
      });
      return;
    }

    try {
      final key = encrypt.Key(Uint8List.fromList(base64Decode(aesKey)));
      final parts = encryptedData.split('~');
      final ciphertext = base64Decode(parts[0]);
      final nonce = base64Decode(parts[1]);
      final tag = base64Decode(parts[2]);

      final combinedData = Uint8List(ciphertext.length + tag.length)
        ..setAll(0, ciphertext)
        ..setAll(ciphertext.length, tag);

      final encrypter = encrypt.Encrypter(encrypt.AES(key, mode: encrypt.AESMode.gcm));
      final iv = encrypt.IV(nonce);

      final decrypted = encrypter.decrypt64(base64Encode(combinedData), iv: iv);
      setState(() {
        _decryptedData = decrypted;
      });
    } catch (e) {
      setState(() {
        _decryptedData = 'Decryption error: $e';
      });
    }
  }

  void _copyToClipboard(String text) {
    Clipboard.setData(ClipboardData(text: text));
    ScaffoldMessenger.of(context).showSnackBar(
      SnackBar(content: Text('Copied to clipboard')),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Encryption App'),
      ),
      body: SingleChildScrollView(
        padding: const EdgeInsets.all(16.0),
        child: Column(
          children: [
            TextField(
              controller: _contentController,
              decoration: InputDecoration(labelText: 'Content to Encrypt'),
            ),
            TextField(
              controller: _aesKeyController,
              decoration: InputDecoration(labelText: 'AES Key for Encryption'),
            ),
            SizedBox(height: 20),
            ElevatedButton(
              onPressed: _encrypt,
              child: Text('Encrypt'),
            ),
            SizedBox(height: 20),
            SelectableText(
              'Encrypted Data: $_encryptedData',
              style: TextStyle(fontSize: 16),
            ),
            ElevatedButton(
              onPressed: () => _copyToClipboard(_encryptedData),
              child: Text('Copy Encrypted Data'),
            ),
            Divider(),
            TextField(
              controller: _encryptedDataController,
              decoration: InputDecoration(labelText: 'Encrypted Data'),
            ),
            TextField(
              controller: _decryptionKeyController,
              decoration: InputDecoration(labelText: 'AES Key for Decryption'),
            ),
            SizedBox(height: 20),
            ElevatedButton(
              onPressed: _decrypt,
              child: Text('Decrypt'),
            ),
            SizedBox(height: 20),
            SelectableText(
              'Decrypted Data: $_decryptedData',
              style: TextStyle(fontSize: 16),
            ),
            ElevatedButton(
              onPressed: () => _copyToClipboard(_decryptedData),
              child: Text('Copy Decrypted Data'),
            ),
          ],
        ),
      ),
    );
  }
}