In the dLibra system, there are two methods of authenticating users:

• Login and password – users are authenticated on the basis of their logins and passwords. If that information is correct (the same as the information stored in the dLibra system), the given user is authenticated. That method is used by readers, administrators, and editors.
• IP address – users are authenticated on the basis of their IP addresses. That method relies on the IP address of the computer of the user who is browsing the library web pages. The user will be authenticated as the given IP user if the IP user’s range of IP addresses contains the IP address of the reader’s computer. That method is for web page readers. It is especially useful when selected resources are only made available to a particular group of computers (for example, in the reading room of a library). From the reader’s point of view, the authentication process takes place automatically – it does not require any actions on the reader’s part.
• Dynamic groups – users can be authenticated with the use of external user bases (for example, LDAP). In such a case, the password and login entered by the user are verified by the dLibra system in a specific authentication system (for example, with the use of an LDAP server).
• Single Sign-On – the dLibra system can cooperate with the Single Sign-On service. That allows users to use several portals through just one user account (for example, a student can use one user account for logging into his or her university website and its digital library website). Having logged into one of the portals, the user can navigate all the portals connected within the framework of the Single Sign-On service, without having to enter a login and a password in each of them.