One-Time Password Mutual Authentication-Based Port Knocking to Secure Remote Ports from Replay Attack

Port knocking is an important security concept for safeguarding server-provided services. This paper introduces a port-knocking scheme that integrates the OTP mutual authentication to enhance the security of commonly targeted remote ports. In client-server communication, the client initiates a service request by attempting a connection to a specific closed port on the server. Port knocking enables users to request the opening of ports for network services through a series of authentication packets. While various port-knocking schemes have been proposed previously, many face issues such as sequence replay attacks, fake packets in knocking sequences, and out-of-order packet submissions. This paper presents a port-knocking scheme that addresses these challenges, leveraging OTP-based authentication to achieve a relatively lightweight solution compared to encryption or digital certificate-based port-knocking schemes.