Single sign-on – Single sign-on (SSO) is a property of access control of multiple related, yet independent, software systems. With this property, a user logs in with a single ID and password to gain access to a connected system or accomplished using the Lightweight Directory Access Protocol (LDAP) and stored LDAP databases on (directory) servers.[1] 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.[2