/**
* Encrypt a secret key packet.
*
* @param OpenPGP_SecretKeyPacket $p Secret key packet.
* @param \phpseclib\Crypt\RSA $cipher RSA cipher object.
* @param OpenPGP_S2K $s2k OpenPGP String-to-key object.
* @param string $iv Initial vector.
*/
protected function _encryptPrivateKey($p, $cipher, $s2k, $iv)
{
$cipher->setIV($iv);
$secret = '';
foreach ($p::$secret_key_fields[$p->algorithm] as $f) {
$f = $p->key[$f];
$secret .= pack('n', OpenPGP::bitlength($f)) . $f;
}
$secret .= hash('sha1', $secret, true);
$p->encrypted_data = $iv . $cipher->encrypt($secret);
$p->s2k = $s2k;
$p->s2k_useage = 254;
$p->symmetric_algorithm = 7;
}