Subject: RE: dnssec discussion today at noon

From: "Hallam-Baker, Phillip" <[email-masked]>
Date: Mon, 22 Jul 2002 10:32:39 -0700

> Public Key Cryptography is absolutely necessary for any
> store-and-forward protocol.

I disagree with your characterization. I don't think that we
need to state that public key cryptography is essential in 
this particular instance (authenticating the actual DNS records),
however it is certainly going to be helpful as a part of the 
solution.

First off, let us consider the nature of actual DNS deployments,
OK so you can have services chained of services off services
etc. But is this a typical deployment, a necessary deployment?

More importantly, examine those deployments and ask yourself 
where the trust boundaries are situated. If I relay a request
through DNS server X then I probably do so because I trust
that service in some sense. If I don't trust the service I 
am going to bypass it and chain directly to authoritative 
services that I do trust.

While transitive authentication is a nice feature of digital
signatures I do not see that feature as being essential in this
particular case.

I think that a situation in which a client has a secure 
connection to a DNS server which has a secure connection to
certain often used DNS servers is a significant step forward
in security from where we are.

I certainly think that we are going to need public key 
cryptography to establish the framework of trust between the
endpoints. But that does not mean that the current DNS 
architecture with a signature for every record is the only 
solution. We could use Kerberos with PK_INIT or some other
key agreement protocol to establish the trust relationships 
from public keys.

		Phill

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From: Derek Atkins <[email-masked]>
Date: 22 Jul 2002 13:36:41 -0400

> services that I do trust.

You have clearly never been to an hotel where their Internet services
intercept all DNS queries regardless of where you send the message...
You cannot trust the infrastructure not to misbehave.  In fact just
the other day I was hit with a DNS re-write attack where my ISP (an
airport) re-wrote all my DNS queries to something of their choosing
(their goal being to force me to read their webpage, but it caused ssh
to fail until I figured that out).

> signatures I do not see that feature as being essential in this

Well, sure, if you have TSIG and use that, then you dont necessarily
need public key crypto to the end user.  However then you are still
trusting the path between your TSIG peer and the authoritative server.

> in security from where we are.

In fact, ANY secure connection is better than where we are... Using
TSIG would be better than where we are.  However I run a local caching
nameserver on my laptop, so TSIG doesn't help me, as my resolver and
"trusted nameserver" co-exist.  I still need DNSSEC.

-derek

-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
       [email-masked]                        PGP key available

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From: Randy Bush <[email-masked]>
Date: Mon, 22 Jul 2002 11:20:19 -0700

> to fail until I figured that out).

my fave was the one where i got layer three wireless fine, it spoofed
everything, and all my spooled email dissapeared into a dns-spoofed
smtp black hole.  bye bye email.

randy