New article on root certificate problems with Windows

[pgut001 at cs.auckland.ac.nz]

Paul Hoffman <paul.hoffman at vpnc.org> writes:
> I posted a new security research article at
> <http://www.proper.com/root-cert-problem/>. It is not directly related to
> crypto (although not so much of the traffic on this list is...), it does
> relate to some PKI topics that are favorites of this list.

The executive summary, so I've got something to reply to:

   In the default configuration for Windows XP with Service Pack 2 (SP2), if a
   user removes one of the trusted root certificates, and the certifier who
   issued that root certificate is trusted by Microsoft, Windows will silently
   add the root certificate back into the user's store and use the original
   trust settings.

While I don't agree with this behaviour, I can see why Microsoft would do
this, and I can't see them changing it at any time in the future.  It's the
same reason why they ignore key usage restrictions and allow (for example) an
encryption-only key to be used for signatures, and a thousand other breaches
of PKI etiquette: There'd be too many user complaints if they didn't.

The people designing this stuff aren't the ones who have to man the tech
helpdesk when users find that things break because of some action that they
don't even understand (see e.g. the Xerox PARC study where a bunch of people
with PhDs in computer science, after following paint-by-numbers instructions
to install certs on their machines, had absolutely no idea what they'd just
done to their computers).

 From a security point of view, this is really bad.  From a usability point of
view, it's necessary.  The solution is to let the HCI people into the design
process, something that's very rarely, if ever, done in the security 
field [0].

Peter.

[0] Before people jump up and down about this: Yes, HCISec has become a very
     active and productive field in the last few years.  Unfortunately far too
     little of the work that's being done is making it into products though.
     We have lots of data saying "X is unusable in practice" and "The best way
     to handle this is Y", but developers keep on pushing X and avoiding (or
     don't even know about) Y.

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