Auth0/Okta Ping Identity It is not uncommon for resource servers to require different authentication strengths or recentness according to the characteristics of a request. This document introduces a mechanism for a resource server to signal to a client that the authentication event associated with the access token of the current request doesn't meet its authentication requirements and specify how to meet them. This document also codifies a mechanism for a client to request that an authorization server achieve a specific authentication strength or recentness when processing an authorization request.