User authentication to an open server or a system based on username and password is familiar to access the control. Entering the username and password in an untruthful computer is impulse to avert from involuntary exposure through phishing, keyloggers and cross-site password reuse. Since users habitually select weak passwords and reuse the same passwords across diverse websites, trespasser can easily snatch these passwords. Once a trespasser hacks a password of the user, it can be maltreated to gain access to more websites. One time password-oPass protocol can guarantee the blocking of trespassers since it evades long-term password.