The PKIX (Public-Key Infrastructure (X.509)) Working Group of the IETF (The Internet Engineering Task Force) has defined a number of certificate management protocols. These protocols are primarily focused on X.509v3 public-key certificates. However, it is sometimes desirable to manage certificates in alternative formats as well. This document specifies how such certificates may be requested using the CRMF (Certificate Request Message Format) syntax that is used by several different protocols. It also explains how alternative certificate formats may be incorporated into such popular protocols as PKIX-CMP (PKIX Certificate Management Protocol) and CMC (Certificate Management Messages over CMS).