Definition
Single sign-on, or SSO, is an authentication scheme that allows a user to log in with a single set of credentials to access multiple independent software systems. Instead of requiring separate usernames and passwords for each application, SSO centralizes authentication through a trusted identity provider. This streamlines user access and improves the overall security posture by reducing the number of potential attack vectors associated with password management. For instance, an employee might use their company network login to access their email, HR portal, and project management tools without re-authenticating. It is important to distinguish SSO from multi-factor authentication, which is a security process that requires more than one verification method, though SSO often incorporates MFA. This concept is frequently tested on certifications like CompTIA Security+, CySA+, and CISSP.