Information and computer security is supported by passwords. Password is the principal part of authentication process. The traditional authentication method is to use text-based password which is also called alphanumeric password. But it has significant drawbacks. So to overcome vulnerabilities of this traditional password scheme a graphical password scheme is developed. But major drawback of graphical scheme is it is vulnerable to shoulder surfing attack and also sometimes to spyware attack. So alternative technique to graphical password a Captcha technique is developed. The major advantage of Captcha is that it can not be identified by bots. Captcha gives the protection from unwanted bots. Also there are some limitations of Captcha, and to overcome those after Captcha for more robust security a new technique is developed which is CaRP (Captcha as gRaphical Passwords). This paper will explore all the passwords techniques for security.

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Captcha Carp Graphical Password Text-based Password.