Корректное шифрование кириллицы (des3)

decrypted = textDec.Text;
TripleDESCryptoServiceProvider des;
MD5CryptoServiceProvider provider;
byte[] pwdhash, buff;
password = "into the dead";
provider = new MD5CryptoServiceProvider();
pwdhash = provider.ComputeHash(ASCIIEncoding.ASCII.GetBytes(password));
provider = null;
des = new TripleDESCryptoServiceProvider();
des.Key = pwdhash;
des.Mode = CipherMode.ECB;
buff = ASCIIEncoding.ASCII.GetBytes(decrypted);
encrypted = Convert.ToBase64String(des.CreateEncryptor().TransformFinalBlock(buff, 0, buff.Length));
textEnc.Text = encrypted;

if (textEnc.Text.Length == 0)
{
   textEnc.Text = string.Join("\r\n", File.ReadAllLines(fullfilename, Encoding.GetEncoding("Windows-1251")));
}
encrypted = textEnc.Text;
byte[] pwdhash, buff;
MD5CryptoServiceProvider provider;
TripleDESCryptoServiceProvider des;
des = new TripleDESCryptoServiceProvider();
provider = new MD5CryptoServiceProvider();
password = "into the dead";
pwdhash = provider.ComputeHash(ASCIIEncoding.ASCII.GetBytes(password));
provider = null;
des.Key = pwdhash;
des.Mode = CipherMode.ECB;
buff = Convert.FromBase64String(encrypted);
decrypted = ASCIIEncoding.ASCII.GetString(des.CreateDecryptor().TransformFinalBlock(buff, 0, buff.Length));
des = null;
textDec.Text = decrypted;