Single sign-on (
SSO) is a property of
access control of multiple related, but independent
software systems. With this property a user
logs in with a single ID and password to gain access to a connected system or systems without using different usernames or passwords, or in some configurations seamlessly sign on at each system. This is typically accomplished using the
Lightweight Directory Access Protocol (LDAP) and stored LDAP databases on servers. A simple version of single sign-on can be achieved over
IP networks using
cookies but only if the sites share a common DNS parent domain.