Keystone is the OpenStack component responsible for identity management and user authentication and authorization, which has unique challenges in cloud-like environments where secure sharing of resources is an essential requirement and yet is fundamental to the core idea of collaborative computing. This introductory talk will give an overview of the keystone project, including: * The many ways users and applications can securely authenticate with keystone, including SAML2.0, OpenID Connect, X.509 and Kerberos, * The implications for authorization in a multitenant environment and how role-based access control is designed in keystone, * How keystone relates to projects outside of the OpenStack ecosystem such as Kubernetes