Шифрование симметричным ключом c#(CryptoAPI)

using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;

namespace Lab03_cryptoAPI_
{
    class TripleDESManagedExample
    {
        public static void Main()
        {

            Console.WriteLine("Введите строку для шифрования:");
            var original = Console.ReadLine();

                // Create a new instance of the TripleDESCryptoServiceProvider
                // class.  This generates a new key and initialization
                // vector (IV).
            try
            {
                using (var myTripleDES = new DESCryptoServiceProvider())
                {
                    // Encrypt the string to an array of bytes.
                    var encrypted = EncryptStringToBytes(original, myTripleDES.Key, myTripleDES.IV);

                    Console.WriteLine($"Зашифрованное сообщение: {Encoding.ASCII.GetString(encrypted)}");

                    // Decrypt the bytes to a string.
                    var roundtrip = DecryptStringFromBytes(encrypted, myTripleDES.Key, myTripleDES.IV);

                    Console.WriteLine($"Рвсшифрованное сообщение: {roundtrip}");

                    //Display the original data and the decrypted data.
                   // Console.WriteLine("Original:   {0}", original);
                    //Console.WriteLine("Round Trip: {0}", roundtrip);
                }

            }
            catch (Exception e)
            {
                Console.WriteLine("Error: {0}", e.Message);
            }
        }
        static byte[] EncryptStringToBytes(string plainText, byte[] Key, byte[] IV)
        {
            // Check arguments.
            if (plainText == null || plainText.Length <= 0)
                throw new ArgumentNullException("plainText");
            if (Key == null || Key.Length <= 0)
                throw new ArgumentNullException("Key");
            if (IV == null || IV.Length <= 0)
                throw new ArgumentNullException("Key");
            byte[] encrypted;
            // Create an TripleDESCryptoServiceProvider object
            // with the specified key and IV.
            using (var tdsAlg = new DESCryptoServiceProvider())
            {
                tdsAlg.Key = Key;
                tdsAlg.IV = IV;

                // Create a decrytor to perform the stream transform.
                ICryptoTransform encryptor = tdsAlg.CreateEncryptor(tdsAlg.Key, tdsAlg.IV);

                // Create the streams used for encryption.
                using (MemoryStream msEncrypt = new MemoryStream())
                {
                    using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                    {
                       // var data = Encoding.ASCII.GetBytes(plainText);

                        //csEncrypt.Write(data, 0,data.Length);
                        using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                        {
                            //Write all data to the stream.
                            swEncrypt.Write(plainText);
                        }
                        encrypted = msEncrypt.ToArray();
                    }
                }
            }

            // Return the encrypted bytes from the memory stream.
            return encrypted;

        }

        static string DecryptStringFromBytes(byte[] cipherText, byte[] Key, byte[] IV)
        {
            // Check arguments.
            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");

            // Declare the string used to hold
            // the decrypted text.
            string plaintext = null;

            // Create an TripleDESCryptoServiceProvider object
            // with the specified key and IV.
            using (var tdsAlg = new DESCryptoServiceProvider())
            {
                tdsAlg.Key = Key;
                tdsAlg.IV = IV;

                // Create a decrytor to perform the stream transform.
                ICryptoTransform decryptor = tdsAlg.CreateDecryptor(tdsAlg.Key, tdsAlg.IV);

                // Create the streams used for decryption.
                using (MemoryStream msDecrypt = new MemoryStream(cipherText))
                {
                    using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                    {
                        using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                        {

                            // Read the decrypted bytes from the decrypting stream
                            // and place them in a string.
                            plaintext = srDecrypt.ReadToEnd();
                        }
                    }
                }

            }

            return plaintext;

        }
    }
}