Siemens Siemens Mobility RFC 5280 defines the Extended Key Usage (EKU) extension and several extended key purposes (KeyPurposeIds) for use with that extension in X.509 certificates. This document defines KeyPurposeIds for general- purpose and trust anchor configuration files, for software and firmware update packages, and for safety-critical communication to be included in the EKU extension of X.509 v3 public key certificates.