Siemens Siemens Mobility RFC 5280 specifies several extended key purpose identifiers (KeyPurposeIds) for 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 Extended Key Usage (EKU) extension of X.509 v3 public key certificates used by industrial automation and the ERJU System Pillar.