This class can be used to authenticate Web users securely. It creates a key encoded with SHA1 based on the IP address and the current time when an user accesses the login page. The key is used to generate a salt value that is used to encrypt the password that the user enters in the login form. On the server side the class uses the same salt to verify whether the password entered by the user matches the password stored in a database. If the authentication is successful, the class starts an authenticated user session. The login keys, user and session information is stored in a database. Currently the class supports either MySQL or PostgreSQL databases.