cake_wallet/lib/bitcoin/file.dart

import 'dart:io';
import 'dart:convert';
import 'package:cake_wallet/bitcoin/key.dart';
import 'package:encrypt/encrypt.dart' as encrypt;
import 'package:flutter/foundation.dart';

Future<void> write(
    {@required String path,
    @required String password,
    @required String data}) async {
  final keys = extractKeys(password);
  final key = encrypt.Key.fromBase64(keys.first);
  final iv = encrypt.IV.fromBase64(keys.last);
  final encrypted = await encode(key: key, iv: iv, data: data);
  final f = File(path);
  f.writeAsStringSync(encrypted);
}

Future<void> writeData(
    {@required String path,
    @required String password,
    @required String data}) async {
  final keys = extractKeys(password);
  final key = encrypt.Key.fromBase64(keys.first);
  final iv = encrypt.IV.fromBase64(keys.last);
  final encrypted = await encode(key: key, iv: iv, data: data);
  final f = File(path);
  f.writeAsStringSync(encrypted);
}

Future<String> read(
    {@required String path, @required String password}) async {
  final file = File(path);

  if (!file.existsSync()) {
    file.createSync();
  }
  
  final encrypted = file.readAsStringSync();

  return decode(password: password, data: encrypted);
}