Muhammad, Hasbi, et al. “ANALISIS PERBANDINGAN SISTEM AUTENTIKASI PORT KNOCKING DAN SINGLE PACKET AUTHORIZATION PADA SERVER RASPBIAN”. Jurnal Informatika Dan Rekayasa Elektronik, vol. 2, no. 1, Apr. 2019, pp. 28-37, http://e-journal.stmiklombok.ac.id/index.php/jire/article/view/87.