Re: Global PKI on DNS?

[Ben Laurie <ben at algroup.co.uk>]

Keith Moore wrote:
> > > Nearly all of the major IETF security protocols (TLS, IPsec, OpenPGP)
> > > already have their own certificate discovery mechanism and therefore
> > > have no need to have certificates in the DNS. TLS, in particular,
> > > wouldn't know what to do with them if they were there.
> >
> > This is missing the point.  Sure, TLS provides the ability for both
> > clients and servers to send certificate chains to their peers as part of
> > session startup.  But what happens if I'm a client, and the chain the
> > server sends me ends in a cert that I don't know about?  I *might* be able
> > to construct a path from one of my trusted roots to one of the certs in
> > the path it sends me, and hence be able to validate the whole chain and
> > hence successfully start the session, instead of failing.  But I can do
> > this only if I can discover certs that *aren't* either in the set it hands
> > me or in my local set, and TLS says nothing about how to do this.  That's
> > the problem that people would like to solve to enable more scalable PKI;
> > it can't be handwaved away.  I'm not particularly a fan of using DNS for
> > this, but discovery remains important.
>
>
> I don't want to discount the importance of cert discovery, but I do
> think it's a stretch to believe that you're going to be willing to
> trust all of the certs that you discover in a chain of significant
> length, for a significant set of purposes.

We're already trusting chains of signficant length (i.e. DNS delegation)
with no decent verification at all. I presume I'd be prepared to trust
certificate chains of that kind of length for those kind of purposes
even more than I trust the current system.

Cheers,

Ben.

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