AES/CBC/PKCS7Padding for dart using pointycastle

main.dart

import 'dart:convert';
import 'dart:typed_data';

import 'package:flutter/material.dart';
import 'package:pointycastle/api.dart';
import 'package:pointycastle/block/aes_fast.dart';
import 'package:pointycastle/block/modes/cbc.dart';
import 'package:pointycastle/padded_block_cipher/padded_block_cipher_impl.dart';
import 'package:pointycastle/paddings/pkcs7.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'AES256/CBC',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const EncryptionPage(),
    );
  }
}

class EncryptionPage extends StatefulWidget {
  const EncryptionPage();

  @override
  _EncryptionPageState createState() => _EncryptionPageState();
}

class _EncryptionPageState extends State<EncryptionPage> {
  String encrypted;

  final TextEditingController controller = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('AES256/CBC'),
      ),
      body: ListView(
        padding: const EdgeInsets.all(16.0),
        children: <Widget>[
          Container(
            child: TextField(
              controller: controller,
            ),
          ),
          RaisedButton(
            child: Text('Encrypt'),
            onPressed: () {
              if (controller.text.isNotEmpty) {
                setState(() {
                  encrypted = Encryption.encrypt(controller.text);
                });
              }
            },
          ),
          if (encrypted != null)
            Container(
              margin: const EdgeInsets.all(16.0),
              child: SelectableText(encrypted),
            ),
          if (encrypted != null)
            RaisedButton(
              child: Text('Decrypt'),
              onPressed: () {
                setState(() {
                  if (encrypted != null && encrypted.isNotEmpty) {
                    final String decrypt = Encryption.decrypt(encrypted);
                    controller.text = decrypt;
                    encrypted = null;
                  }
                });
              },
            ),
        ],
      ),
    );
  }
}

//Z"b~dERuX!q&zj-,>d}6aEw-_9&xJ^@8
class Encryption {
  static final Uint8List _key = new Uint8List.fromList(<int>[
    0x5a,
    0x22,
    0x62,
    0x7e,
    0x64,
    0x45,
    0x52,
    0x75,
    0x58,
    0x21,
    0x71,
    0x26,
    0x7a,
    0x6a,
    0x2d,
    0x2c,
    0x3e,
    0x64,
    0x7d,
    0x36,
    0x61,
    0x45,
    0x77,
    0x2d,
    0x5f,
    0x39,
    0x26,
    0x78,
    0x4a,
    0x5e,
    0x40,
    0x38
  ]);

  static final Uint8List _iv = new Uint8List.fromList(
    <int>[
      0xda,
      0x39,
      0xa3,
      0xee,
      0x5e,
      0x6b,
      0x4b,
      0x0d,
      0x32,
      0x55,
      0xbf,
      0xef,
      0x95,
      0x60,
      0x18,
      0x90
    ],
  );

  static String encrypt(String text) {
    return base64Encode(encryptList(utf8.encode(text)));
  }

  static Uint8List encryptList(Uint8List data) {
    final CBCBlockCipher cbcCipher = new CBCBlockCipher(new AESFastEngine());
    final ParametersWithIV<KeyParameter> ivParams =
        new ParametersWithIV<KeyParameter>(new KeyParameter(_key), _iv);
    final PaddedBlockCipherParameters<ParametersWithIV<KeyParameter>, Null>
        paddingParams =
        new PaddedBlockCipherParameters<ParametersWithIV<KeyParameter>, Null>(
            ivParams, null);

    final PaddedBlockCipherImpl paddedCipher =
        new PaddedBlockCipherImpl(new PKCS7Padding(), cbcCipher);
    paddedCipher.init(true, paddingParams);

    try {
      return paddedCipher.process(data);
    } catch (e) {
      print(e);
      return null;
    }
  }

  static String decrypt(String data) =>
      utf8.decode(decryptList(base64Decode(data)));

  static Uint8List decryptList(Uint8List data) {
    final CBCBlockCipher cbcCipher = new CBCBlockCipher(new AESFastEngine());
    final ParametersWithIV<KeyParameter> ivParams =
        new ParametersWithIV<KeyParameter>(new KeyParameter(_key), _iv);
    final PaddedBlockCipherParameters<ParametersWithIV<KeyParameter>, Null>
        paddingParams =
        new PaddedBlockCipherParameters<ParametersWithIV<KeyParameter>, Null>(
            ivParams, null);
    final PaddedBlockCipherImpl paddedCipher =
        new PaddedBlockCipherImpl(new PKCS7Padding(), cbcCipher);
    paddedCipher.init(false, paddingParams);

    try {
      return paddedCipher.process(data);
    } catch (e) {
      print(e);
      return null;
    }
  }
}

How to use a passphrase without using the predefined _key?

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Great solution