Secure communication is an important issue in networks and user authentication is a very important part of the security. Several strong-password authentication protocols have been introduced, but there is no fully secure authentication scheme that can resist all known attacks. We propose enhanced secure schemes with registration and login protocols, and add the “forget password” and password/verifier change protocols. We show that our scheme is more secure against guessing, stolen-verifier, replay, denial-of-service, and impersonation attacks than previously introduced protocols.