  Port knocking is a technique by which only a single packet or special
sequence will permit the firewall to open a port on a machine where all ports
are blocked by default. It is a passive authorization technique which offers
firewall-level authentication to ensure authorized access to potentially
vulnerable network services. In this paper, we present performance evaluation
and analytical comparison of three widely used port knocking (PK) algorithms,
Aldaba, FWKNOP and SIG-2. Comparative analysis is based upon ten selected
parameters; Platforms (Supported OS), Implementation (PK, SPA or both),
Protocols (UDP, TCP, ICMP), Out of Order packet delivery, NAT (Network Address
Translation), Encryption Algorithms, Root privileges (For installation and
operation), Weak Passwords, Replay Attacks and IPv6 compatibility. Based upon
these parameters, relative performance score has been given to each algorithm.
Finally, we deduce that FWKNOP due to compatibility with windows client is the
most efficient among chosen PK implementations.

Networking and Internet Architecture;Cryptography and Security