Certificate Revocation Trees (CRTs). High-performance validation method proprietary to ValiCert. This is the default.
VTK_VM_OCSP
Online Certificate Status Protocol. This validation method requires a certificate recipient to check certificate status by sending a request to an OCSP server. This method provides up-to-date certificate status information, but requires network communication to the OCSP server.
VTK_VM_CRL
Certificate Revocation Lists (CRLs). This validation method requires that the verifier download CRLs published by CA and confirm that certificate is not on the list. This method is provided to accommodate legacy CRL-based systems.