Mutual certificate chain verification between a VU and an EGF shall take place only during the coupling of the VU and the EGF by a workshop. During normal operation of a coupled VU and EGF, no certificates shall be verified. Instead, the VU and EGF shall trust the certificates they stored during the coupling, after checking the temporal validity of these certificates. The VU and the EGF shall not trust any other certificates for protecting the VU — EGF communication during normal operation.