Subject: Re: [kitten] PKCROSS

From: Josh Howlett <[email-masked]>
Date: Thu, 1 Aug 2013 15:53:18 +0000

>
>That's nice, for you :)  But you should care about it.  And we should
>care about: a) making sysadmins' lives easier, b) removing the need
>for them to know sensitive secret keys, c) scalability (see (a)), d)
>removing the need for manual key rollover and outages during key
>rollover.  We might agree that we don't need e) LoF/TOFU, but I think
>ABFAB is proof that we need something like it, and also, for a very
>large Internet I think LoF/TOFU makes some sense, and indeed we see
>some of that in TLS server PKI specifications like key/CA pinning, and
>in browser plugins like CertPatrol.

(Speaking as an individual)

Personally I would argue that trust management strategies such as LoF and
pinning are indicative of a poorly functioning trust system. They make
sense only insofar that the other options are even worse. We should aspire
to better. 

Nico's PKCROSS draft looks really interesting. However I don't believe
that, in practice, the use of DANE will provide a solution for "a very
large Internet", unless KDC trust policies can be made congruent with DNS
naming.

Josh.

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From: Nico Williams <[email-masked]>
Date: Thu, 1 Aug 2013 11:09:46 -0500

> sense only insofar that the other options are even worse. We should aspire

LoF/TOFU is not a central feature here.  It's just a side benefit that
one could do it.

Pseudonymous authentication is at least as useful as anonymous authentication.

> large Internet", unless KDC trust policies can be made congruent with DNS

If you want to scale to Internet scale then you kinda need trust
policies that are congruent with the DNS.  Now, that doesn't mean that
you can't have islands of higher trust.

For example, CRYPTONECTOR.COM might have various partners with
manually-exchanged trust anchors.  Principals in our respective realms
would reject trust paths involving each other than do not use those
manually-exchanged trust anchors.  But if I wanted to access some AFS
resource in some .edu, I could without having to manually exchange any
sort of key material to make that possible -- that's what scalability
requires.  And I could, once I've authenticated a service in some
realm that later becomes valuable to me, apply pinning techniques to
increase trust in spite of having used DANE to start with (this is
TOFUish).

To me this is no different than ABFAB's approach to federation.  If
it's good for ABFAB, it's good for Kerberos.

Nico
--

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From: Josh Howlett <[email-masked]>
Date: Thu, 1 Aug 2013 16:31:21 +0000

>LoF/TOFU is not a central feature here.  It's just a side benefit that

Understood (as a "side feature" :-)

>you can't have islands of higher trust.

Sure. But those "higher trust" islands get manifested using a different
mechanism from the mechanism used to manifest the "baseline" trust. I
would prefer a more consistent architecture that didn't require this
distinction.

>it's good for ABFAB, it's good for Kerberos.

Well, I disagree but let's not have that discussion here :-)

Josh.

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From: Josh Howlett <[email-masked]>
Date: Thu, 1 Aug 2013 16:51:30 +0000

>Well, I disagree but let's not have that discussion here :-)

Let me clarify: you are correct for extant trust management mechanisms for
AAA infrastructures that are standardised today.

Josh.