This document specifies entity authentication mechanisms using digital signatures based on asymmetric techniques. A digital signature is used to verify the identity of an entity. Ten mechanisms are specified in this document. The first five mechanisms do not involve an on-line trusted third party and the last five make use of on-line trusted third parties. In both of these two categories, two mechanisms achieve unilateral authentication and the remaining three achieve mutual authentication. Annex A defines the object identifiers assigned to the entity authentication mechanisms specified in this document.