csharp lab 2 symmetric

using System;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Windows.Forms;

namespace csharp_crypto_2
{
    public partial class Form1 : Form
    {
        private static readonly RNGCryptoServiceProvider Rand = new RNGCryptoServiceProvider();

        public Form1()
        {
            InitializeComponent();
        }

        private static int RandomInteger(int min, int max)
        {
            var scale = uint.MaxValue;
            while (scale == uint.MaxValue)
            {
                var fourBytes = new byte[4];
                Rand.GetBytes(fourBytes);
                scale = BitConverter.ToUInt32(fourBytes, 0);
            }

            return (int) (min + (max - min) *
                (scale / (double) uint.MaxValue));
        }

        public static byte[] StringToByteArray(string hex) {
            // эквивалетно
            //byte[] bytes = new byte[s.Length/2];
            //for (int i=0; i<s.Length; i+=2)
            //{
            //    bytes[i/2] = Convert.ToByte(s.Substring(i,2), 16);
            //}
            return Enumerable.Range(0, hex.Length)
                .Where(x => x % 2 == 0)
                .Select(x => Convert.ToByte(hex.Substring(x, 2), 16))
                .ToArray();
        }

        private static byte[] EncryptAES(string input, byte[] Key, byte[] IV)
        {
            if (input == null || input.Length <= 0)
                throw new ArgumentNullException("cipherText");
            if (Key == null || Key.Length <= 0)
                throw new ArgumentNullException("Key");
            if (IV == null || IV.Length <= 0)
                throw new ArgumentNullException("Key");
            byte[] encrypted;
            using (var aes = Aes.Create())
            {
                aes.Key = Key;
                aes.IV = IV;
                var encryptor = aes.CreateEncryptor(aes.Key, aes.IV); // ICryptoTransform
                using (var msEncrypt = new MemoryStream())
                using (var csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                {
                    using (var swEncrypt = new StreamWriter(csEncrypt))
                    {
                            swEncrypt.Write(input);
                    }
                    encrypted = msEncrypt.ToArray();
                }

            }

            return encrypted;
        }

        private static string DecryptAES(byte[] cipherText, byte[] Key, byte[] IV)
        {
            if (cipherText == null || cipherText.Length <= 0)
                throw new ArgumentNullException("cipherText");
            if (Key == null || Key.Length <= 0)
                throw new ArgumentNullException("Key");
            if (IV == null || IV.Length <= 0)
                throw new ArgumentNullException("Key");
            var output = string.Empty;
            using (var aes = Aes.Create())
            {
                aes.Key = Key;
                aes.IV = IV;
                var decryptor = aes.CreateDecryptor(aes.Key, aes.IV); // ICryptoTransform
                using (var msDecrypt = new MemoryStream(cipherText))
                using (var csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                using (var srDecrypt = new StreamReader(csDecrypt))
                    output = srDecrypt.ReadToEnd();

            }

            return output;
        }

        public static string RandomHexString(int length)
        {
            var random = new Random();
            const string valid = "ABCDEF0123456789";
            return new string(Enumerable.Repeat(valid, length)
                .Select(s => s[RandomInteger(0, s.Length)]).ToArray());
        }

        private void actionButton_Click(object sender, EventArgs e)
        {
            // обработка входных данных
            // если нет входных данных (они пусты), создаём рандомную строку
            if (keyBox.Text == "") keyBox.Text = RandomHexString(32);

            if (initVectorBox.Text == "") initVectorBox.Text = RandomHexString(32);

            var aesKey = StringToByteArray(keyBox.Text);
            var aesIV = StringToByteArray(initVectorBox.Text);
            //UnicodeEncoding UE = new UnicodeEncoding();
            //var aesKey = UE.GetBytes(keyBox.Text);
            //var aesIV = UE.GetBytes(initVectorBox.Text);
            // проверка key на стойкость
            var keyLength = aesKey.Length * 8;
            MessageBox.Show(keyLength.ToString(), "");
            MessageBox.Show(keyLength >= 128 ? "Ключ стойкий" : "Ключ не является стойким");
            // открыть файл для шифрования
            var fileContent = string.Empty;
            var filePath = string.Empty;
            using (var dialog = new OpenFileDialog())
            {
                dialog.Filter = "TXT files (*.txt)|*.txt|All files (*.*)|*.*";
                dialog.FilterIndex = 2;
                dialog.RestoreDirectory = true;
                if (dialog.ShowDialog() == DialogResult.OK)
                {
                    var fileStream = dialog.OpenFile();
                    filePath = dialog.FileName;

                    var outputFile = string.Empty;
                    using (var saveFileDialog = new SaveFileDialog())
                    {
                        saveFileDialog.Filter = "TXT files (*.txt)|*.txt|All files (*.*)|*.*";
                        saveFileDialog.FileName = "Result";
                        if (saveFileDialog.ShowDialog() == DialogResult.OK) outputFile = saveFileDialog.FileName;
                    }

                    if (encryptButton.Checked)
                    {
                        using (var reader = new StreamReader(fileStream))
                        {
                            fileContent = reader.ReadToEnd();
                        }

                        File.WriteAllBytes(outputFile, EncryptAES(fileContent, aesKey, aesIV));
                    }

                    if (decryptButton.Checked)
                    {
                        var test = File.ReadAllBytes(filePath);
                        // расшифрование
                        File.WriteAllText(outputFile, DecryptAES(test, aesKey, aesIV));
                    }

                    MessageBox.Show("Файл сохранён: " + outputFile, "ОК", MessageBoxButtons.OK,
                        MessageBoxIcon.Information);
                }
                else
                {
                    MessageBox.Show("Выберите файл для продолжения работы", "Ошибка", MessageBoxButtons.OK,
                        MessageBoxIcon.Error);
                }
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            keyLengthLabel.Text = "";
            IVLengthLabel.Text = "";
            keyBoxLength.Text = "";
            IVBoxLength.Text = "";
        }

        private void keyBox_TextChanged(object sender, EventArgs e)
        {
            // char занимает в памяти 2 байта
            keyLengthLabel.Text = (keyBox.Text.Length*8/2) + " бит";
            keyBoxLength.Text = keyBox.Text.Length.ToString();
        }

        private void initVectorBox_TextChanged(object sender, EventArgs e)
        {
            IVLengthLabel.Text = (initVectorBox.Text.Length*8/2) + " бит";
            IVBoxLength.Text = initVectorBox.Text.Length.ToString();
        }
    }
}