International Journal of Computer Science and Management Research (IJCSMR)
Online password guessing attacks is a major problem in password only remote login systems. Automated Turing Test (ATT) is the commonly used approach to detect and prevent such malicious login attempts. Many login protocols use ATTs. But ATTs are inconvenient to users. The PS (Pinkas and Sander), VS (Van oorschot and Stubblebine) and PGRP (Password Guessing Resistant Protocol) are the existing protocols based on ATT. In PS proposal the server authenticates a user only if a valid cookie is received from the browser otherwise the user is asked to challenge ATT each time.