aes_dencrypt.cs

private void AES_Decrypt(string inputFile, string password)
{
    //todo:
    // - create error message on wrong password
    // - on cancel: close and delete file
    // - on wrong password: close and delete file!
    // - create a better filen name
    // - could be check md5 hash on the files but it make this slow

    byte[] passwordBytes = System.Text.Encoding.UTF8.GetBytes(password);
    byte[] salt = new byte[32];
    FileStream fsCrypt = new FileStream(inputFile, FileMode.Open);

    fsCrypt.Read(salt, 0, salt.Length);

    RijndaelManaged AES = new RijndaelManaged();
    AES.KeySize = 256;
    AES.BlockSize = 128;

    var key = new Rfc2898DeriveBytes(passwordBytes, salt, 50000);
    AES.Key = key.GetBytes(AES.KeySize / 8);
    AES.IV = key.GetBytes(AES.BlockSize / 8);
    AES.Padding = PaddingMode.PKCS7;
    AES.Mode = CipherMode.CFB;

    CryptoStream cs = new CryptoStream(fsCrypt, AES.CreateDecryptor(), CryptoStreamMode.Read);
    FileStream fsOut = new FileStream(inputFile + ".decrypted", FileMode.Create);

    int read;
    byte[] buffer = new byte[1048576];

    try
    {
        while ((read = cs.Read(buffer, 0, buffer.Length)) > 0)
        {
            Application.DoEvents();
            fsOut.Write(buffer, 0, read);
        }
    }
    catch (System.Security.Cryptography.CryptographicException ex_CryptographicException)
    {
        Debug.WriteLine("CryptographicException error: " + ex_CryptographicException.Message);
    }
    catch (Exception ex)
    {
        Debug.WriteLine("Error: " + ex.Message);
    }

    try
    {
        cs.Close();
    }
    catch (Exception ex)
    {
        Debug.WriteLine("Error by closing CryptoStream: " + ex.Message);
    }
    finally
    {
        fsOut.Close();
        fsCrypt.Close();
    }
}