static ssize_t x509_to_serial(void *x509_der_buf, size_t x509_der_buf_len, void **outbuf) {
	struct x509_object x509;
	int read_ret;

	read_ret = asn1_x509_read_object(x509_der_buf, x509_der_buf_len, &x509);
	if (read_ret != 0) {
		CACKEY_DEBUG_PRINTF("Unable to read serial number from a %lu byte buffer", (unsigned long) x509_der_buf_len);
		CACKEY_DEBUG_PRINTBUF("X.509 DER:", x509_der_buf, x509_der_buf_len);

		return(-1);
	}

	if (outbuf) {
		*outbuf = x509.serial_number.asn1rep;