URPOSE_CRL_SIGN</b>, <b>X509_PURPOSE_ANY</b>, <b>X509_PURPOSE_OCSP_HELPER</b>, <b>X509_PURPOSE_TIMESTAMP_SIGN</b> and <b>X509_PURPOSE_CODE_SIGN</b>. It is also possible to create a custom purpose value. Setting a purpose requests that the key usage and extended key usage (EKU) extensions optionally declared within the certificate and its chain are verified to be consistent with that purpose. For SSL client, SSL server, and S/MIME purposes, the EKU is checked also for the CA certificates along the chain, inc