// Alicinin sertifiklarini disa aktarmasi
 private void buttonRecipientExport_Click(object sender, EventArgs e)
 {
     Directory.CreateDirectory(FileDirectory.Create("Sender\\") + "ReceivedCertificates\\");
     ExportCertificate(dataGridViewRecipient, users);
 }
        // RSA private key'lerin dosyadan okunmasi
        public RSAParameters GetPrivateKey(string dirName, Form form)
        {
            RSAParametersSerializable rsaPrivateKeyInfoSerializable = null;

            DirectoryInfo dirInfo = new DirectoryInfo(FileDirectory.Create(dirName) + "Keys\\");

            FileInfo[] files = dirInfo.GetFiles();
            foreach (FileInfo file in files)
            {
                if (file.Name.Equals(ID))
                {
                    rsaPrivateKeyInfoSerializable = Serialization.ReadFromBinaryFile <RSAParametersSerializable>(FileDirectory.Create(dirName) + "Keys\\" + ID);
                }
            }

            Form8Passphrase formPassphrase = new Form8Passphrase(Name);
            bool            invalidPass    = true;
            int             tryCount       = 1;

            while (invalidPass && tryCount <= 3)
            {
                formPassphrase.labelTry.Visible = (tryCount == 2 || tryCount == 3) ? true : false;
                formPassphrase.labelTry.Text    = "Yanlış parola. Deneme: " + tryCount + " / 3.";
                formPassphrase.ShowDialog(form);
                byte[] passphrase = null;
                if (formPassphrase.DialogResult == DialogResult.OK)
                {
                    passphrase = Encoding.ASCII.GetBytes(formPassphrase.textBoxPassphrase.Text);
                    byte[] hashedInputPassphrase = SHA256Salted.GenerateSaltedHash(passphrase, salt);
                    if (SHA256Salted.CompareByteArrays(hashedInputPassphrase, hashedPassphrase))
                    {
                        rsaPrivateKeyInfoSerializable.Decrypt(passphrase);
                        invalidPass = false;
                    }
                    else
                    {
                        invalidPass = true;
                        tryCount++;
                    }
                }
                else
                {
                    break;
                }
            }
            if (tryCount > 3)
            {
                return(new RSAParameters());
            }
            return(rsaPrivateKeyInfoSerializable.RSAParameters);
        }