article about Air Gapped OpenPGP Key

[Robert J. Hansen]

> 4. Are there any known issues with your "air gapped" system being the
> same physical hardware as your everyday system even if you use a LiveCD?

The airgap networks I've seen have run in separate rooms from the  
regular network and use a different kind of networking hardware in  
order to make cross-contamination impossible.  For instance, if the  
network uses gigabit Ethernet then the airgap will use 10base2 coaxial  
cable, or some other incompatible networking system.  (This may be the  
only remaining legitimate use for 10base2...)

If your airgap system is network-compatible with the regular system,  
then you don't have an airgap.  What you have instead is something  
that looks like an airgap until somebody has a five-second braino  
while hooking up network cables, and you don't discover for two weeks  
afterwards that your airgap was breached.