Valid point. I suspect that many of us are operating from an intuitive notion 
of “Well, of course there must be a security perimeter”, which surreptitiously 
assumes everyone’s preferred private definition of *their* current perimeter.

From a Root CA perspective, I would have thought that there must be a 
physically defined site perimeter within which only authorised personnel are 
allowed (subject to logging, identification, secret knowledge demonstration, 
etc.) AND that there is an equipment perimeter which contains (at least) the 
equipment constituting the Root CA system (controlling computer, HSM, 
crosswired cables, dedicated network hub, serial cables, etc) [e.g. a locked 
cabinet]. There is thus a perimeter inside that cabinet which is the core Root 
CA equipment network (and in fact, may be the only equipment within that 
cabinet). This is the Root CA perimeter.

With that (verbose) description, I would say that, if any connection through 
the designated Root CA perimeter and *any* other equipment is possible, then 
that Root CA system is not air gapped. A connection being defined as an active 
piece of equipment capable of bearing data in real time to another piece of 
equipment without active, authorised, human participation.

So, that would mean that a Root CA controlling laptop with a powered Bluetooth 
or Wifi adapter (connected to an AP or not) is not air gapped. But it still 
leaves the ability to communicate data via a USB storage device which can then 
be used to export data (CRLs, signed certificates, etc.) as well as import 
(PKCS10 data, etc.), because that’s not “real time”. Although, I admit, it’s a 
somewhat arbitrary distinction to draw.

Now, whether such a description is workable or not as a requirement, I’m not 
sure.

Neil

> On 8 Sep 2017, at 21:17, Tim Hollebeek <[email protected]> wrote:
> 
> I think one of the problems with some of the discussion on the call is that 
> we don’t really have a concept of a security perimeter for CA systems in the 
> current requirements.  This makes it hard to write requirements that don’t 
> allow stupid things, like cables running to systems which, while not 
> connected to the public internet, do not have the appropriate access controls.
>  
> My thinking right now is that perhaps the best approach is to actually 
> require an identified security perimeter, and then an air gapped system is a 
> system that is not physically connected to any networks or devices outside 
> the security perimeter, nor can it be accessed from outside of the security 
> perimeter.
>  
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