Characterizing a client apparatus on at least one server apparatus

A client apparatus, comprising:

• a wireless receiver;
• a memory coupled to a processor;
• wherein the wireless receiver is configured to receive a first certificate from a server apparatus in an event of a first request for a connection set-up;
• wherein the memory coupled to the processor is configured to store the values of one or more permanently specified certificate parameters of the first certificate as a stored characterization parameter set;
• wherein no other values for the one or more permanently specified certificate parameters will be stored in the client apparatus;
• wherein the one or more permanently specified certificate parameters of the first certificate are a subset of the first certificate;
• wherein the processor is configured to check values for one or more permanently specified certificate parameters of a second certificate received from a second server apparatus against values for the stored characterization parameter set in the event of a request for a further connection set-up and to accept the request for the further connection set-up only when all values of all of the one or more permanently specified certificate parameters of the second certificate match all values of the stored characterization parameter set.