This document specifies entity authentication mechanisms using authenticated encryption algorithms. Four of the mechanisms provide entity authentication between two entities where no trusted third party is involved; two of these are mechanisms to unilaterally authenticate one entity to another, while the other two are mechanisms for mutual authentication of two entities. The remaining mechanisms require an on-line trusted third party for the establishment of a common secret key. They also realize mutual or unilateral entity authentication. Annex A defines Object Identifiers for the mechanisms specified in this document.