The document discusses techniques for operating system security including authentication, authorization, and confinement. It describes the goals of safely sharing resources while preventing unauthorized access to private data or interference between programs. The trusted computing base and security techniques like reference monitors, access control lists, and capabilities are explained. Later sections cover implementing authentication through passwords, public keys, and biometrics and how authorization works using access control matrices. The challenges of confinement and running untrusted code securely are also discussed.