Secure connection

Hi
for a secure connection of predefined clients to my server I need to check with all clients. apart from username and password I could get some info with the help of Server Variables Syntax, but for a much more secure connection I need to check with some other unique info such as Network Card Serial Nr. or you may say "MAC Address".
Does anybody knows how I could check these type of information?
Is there any syntax for it?

thanks in advance
Bahramm

Remember most network information can be "spoofed". You mentioned server variables, are you talking about a web server? If so you won't have access to any of the client data like mac address, etc.

Consider what (or who) you are guarding against before deciding on the security precautions you'll take. If you're worried about unknowns sniffing on the network path then strong encryption will be your answer, but that won't protect you at all from the janitor that sits down at a screen and logs on using the username/password scribbled on the post-it note on the screen